Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

11 files changed, 4123 insertions, 0 deletions

diff --git a/intl/icu/source/tools/makeconv/Makefile.in b/intl/icu/source/tools/makeconv/Makefile.in
new file mode 100644
index 0000000000..061d54c488
--- /dev/null
+++ b/intl/icu/source/tools/makeconv/Makefile.in
@@ -0,0 +1,97 @@
+## Makefile.in for ICU - tools/makeconv
+## Copyright (C) 2016 and later: Unicode, Inc. and others.
+## License & terms of use: http://www.unicode.org/copyright.html
+## Copyright (c) 1999-2011, International Business Machines Corporation and
+## others. All Rights Reserved.
+## Stephen F. Booth
+
+## Source directory information
+srcdir = @srcdir@
+top_srcdir = @top_srcdir@
+
+top_builddir = ../..
+
+include $(top_builddir)/icudefs.mk
+
+## Build directory information
+subdir = tools/makeconv
+
+TARGET_STUB_NAME = makeconv
+
+SECTION = 1
+
+MAN_FILES = $(TARGET_STUB_NAME).$(SECTION)
+
+## Extra files to remove for 'make clean'
+CLEANFILES = *~ $(DEPS) $(MAN_FILES)
+
+## Target information
+TARGET = $(BINDIR)/$(TARGET_STUB_NAME)$(EXEEXT)
+
+CPPFLAGS += -I$(srcdir) -I$(top_srcdir)/common -I$(srcdir)/../toolutil
+LIBS = $(LIBICUTOOLUTIL) $(LIBICUI18N) $(LIBICUUC) $(DEFAULT_LIBS) $(LIB_M)
+
+SOURCES = $(shell cat $(srcdir)/sources.txt)
+OBJECTS = $(patsubst %.cpp,%.o,$(patsubst %.c,%.o, $(SOURCES)))
+
+DEPS = $(OBJECTS:.o=.d)
+
+## List of phony targets
+.PHONY : all all-local install install-local clean clean-local	\
+distclean distclean-local dist dist-local check check-local install-man
+
+## Clear suffix list
+.SUFFIXES :
+
+## List of standard targets
+all: all-local
+install: install-local
+clean: clean-local
+distclean : distclean-local
+dist: dist-local
+check: all check-local
+
+all-local: $(TARGET) $(MAN_FILES)
+
+install-local: all-local install-man
+	$(MKINSTALLDIRS) $(DESTDIR)$(bindir)
+	$(INSTALL) $(TARGET) $(DESTDIR)$(bindir)
+
+install-man: $(MAN_FILES)
+	$(MKINSTALLDIRS) $(DESTDIR)$(mandir)/man$(SECTION)
+	$(INSTALL_DATA) $? $(DESTDIR)$(mandir)/man$(SECTION)
+
+
+dist-local:
+
+clean-local:
+	test -z "$(CLEANFILES)" || $(RMV) $(CLEANFILES)
+	$(RMV) $(TARGET) $(OBJECTS)
+
+distclean-local: clean-local
+	$(RMV) Makefile
+
+check-local: all-local
+
+Makefile: $(srcdir)/Makefile.in  $(top_builddir)/config.status
+	cd $(top_builddir) \
+	 && CONFIG_FILES=$(subdir)/$@ CONFIG_HEADERS= $(SHELL) ./config.status
+
+$(TARGET) : $(OBJECTS)
+	$(LINK.cc) $(OUTOPT)$@ $^ $(LIBS)
+	$(POST_BUILD_STEP)
+
+
+%.$(SECTION): $(srcdir)/%.$(SECTION).in
+	cd $(top_builddir) \
+	 && CONFIG_FILES=$(subdir)/$@ CONFIG_HEADERS= $(SHELL) ./config.status
+
+
+ifeq (,$(MAKECMDGOALS))
+-include $(DEPS)
+else
+ifneq ($(patsubst %clean,,$(MAKECMDGOALS)),)
+-include $(DEPS)
+endif
+endif
+
diff --git a/intl/icu/source/tools/makeconv/gencnvex.c b/intl/icu/source/tools/makeconv/gencnvex.c
new file mode 100644
index 0000000000..837a2d2c50
--- /dev/null
+++ b/intl/icu/source/tools/makeconv/gencnvex.c
@@ -0,0 +1,1084 @@
+// © 2016 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
+/*
+*******************************************************************************
+*
+*   Copyright (C) 2003-2014, International Business Machines
+*   Corporation and others.  All Rights Reserved.
+*
+*******************************************************************************
+*   file name:  gencnvex.c
+*   encoding:   UTF-8
+*   tab size:   8 (not used)
+*   indentation:4
+*
+*   created on: 2003oct12
+*   created by: Markus W. Scherer
+*/
+
+#include <stdbool.h>
+#include <stdio.h>
+#include "unicode/utypes.h"
+#include "unicode/ustring.h"
+#include "cstring.h"
+#include "cmemory.h"
+#include "ucnv_cnv.h"
+#include "ucnvmbcs.h"
+#include "toolutil.h"
+#include "unewdata.h"
+#include "ucm.h"
+#include "makeconv.h"
+#include "genmbcs.h"
+
+static void
+CnvExtClose(NewConverter *cnvData);
+
+static UBool
+CnvExtIsValid(NewConverter *cnvData,
+              const uint8_t *bytes, int32_t length);
+
+static UBool
+CnvExtAddTable(NewConverter *cnvData, UCMTable *table, UConverterStaticData *staticData);
+
+static uint32_t
+CnvExtWrite(NewConverter *cnvData, const UConverterStaticData *staticData,
+            UNewDataMemory *pData, int32_t tableType);
+
+typedef struct CnvExtData {
+    NewConverter newConverter;
+
+    UCMFile *ucm;
+
+    /* toUnicode (state table in ucm->states) */
+    UToolMemory *toUTable, *toUUChars;
+
+    /* fromUnicode */
+    UToolMemory *fromUTableUChars, *fromUTableValues, *fromUBytes;
+
+    uint16_t stage1[MBCS_STAGE_1_SIZE];
+    uint16_t stage2[MBCS_STAGE_2_SIZE];
+    uint16_t stage3[0x10000<<UCNV_EXT_STAGE_2_LEFT_SHIFT]; /* 0x10000 because of 16-bit stage 2/3 indexes */
+    uint32_t stage3b[0x10000];
+
+    int32_t stage1Top, stage2Top, stage3Top, stage3bTop;
+
+    /* for stage3 compaction of <subchar1> |2 mappings */
+    uint16_t stage3Sub1Block;
+
+    /* statistics */
+    int32_t
+        maxInBytes, maxOutBytes, maxBytesPerUChar,
+        maxInUChars, maxOutUChars, maxUCharsPerByte;
+} CnvExtData;
+
+NewConverter *
+CnvExtOpen(UCMFile *ucm) {
+    CnvExtData *extData;
+    
+    extData=(CnvExtData *)uprv_malloc(sizeof(CnvExtData));
+    if(extData==NULL) {
+        printf("out of memory\n");
+        exit(U_MEMORY_ALLOCATION_ERROR);
+    }
+    uprv_memset(extData, 0, sizeof(CnvExtData));
+
+    extData->ucm=ucm; /* aliased, not owned */
+
+    extData->newConverter.close=CnvExtClose;
+    extData->newConverter.isValid=CnvExtIsValid;
+    extData->newConverter.addTable=CnvExtAddTable;
+    extData->newConverter.write=CnvExtWrite;
+    return &extData->newConverter;
+}
+
+static void
+CnvExtClose(NewConverter *cnvData) {
+    CnvExtData *extData=(CnvExtData *)cnvData;
+    if(extData!=NULL) {
+        utm_close(extData->toUTable);
+        utm_close(extData->toUUChars);
+        utm_close(extData->fromUTableUChars);
+        utm_close(extData->fromUTableValues);
+        utm_close(extData->fromUBytes);
+        uprv_free(extData);
+    }
+}
+
+/* we do not expect this to be called */
+static UBool
+CnvExtIsValid(NewConverter *cnvData,
+        const uint8_t *bytes, int32_t length) {
+    // suppress compiler warnings about unused variables
+    (void)cnvData;
+    (void)bytes;
+    (void)length;
+    return false;
+}
+
+static uint32_t
+CnvExtWrite(NewConverter *cnvData, const UConverterStaticData *staticData,
+            UNewDataMemory *pData, int32_t tableType) {
+    (void) staticData; // suppress compiler warnings about unused variable
+    CnvExtData *extData=(CnvExtData *)cnvData;
+    int32_t length, top, headerSize;
+
+    int32_t indexes[UCNV_EXT_INDEXES_MIN_LENGTH]={ 0 };
+
+    if(tableType&TABLE_BASE) {
+        headerSize=0;
+    } else {
+        _MBCSHeader header={ { 0, 0, 0, 0 }, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
+
+        /* write the header and base table name for an extension-only table */
+        length=(int32_t)uprv_strlen(extData->ucm->baseName)+1;
+        while(length&3) {
+            /* add padding */
+            extData->ucm->baseName[length++]=0;
+        }
+
+        headerSize=MBCS_HEADER_V4_LENGTH*4+length;
+
+        /* fill the header */
+        header.version[0]=4;
+        header.version[1]=2;
+        header.flags=(uint32_t)((headerSize<<8)|MBCS_OUTPUT_EXT_ONLY);
+
+        /* write the header and the base table name */
+        udata_writeBlock(pData, &header, MBCS_HEADER_V4_LENGTH*4);
+        udata_writeBlock(pData, extData->ucm->baseName, length);
+    }
+
+    /* fill indexes[] - offsets/indexes are in units of the target array */
+    top=0;
+
+    indexes[UCNV_EXT_INDEXES_LENGTH]=length=UCNV_EXT_INDEXES_MIN_LENGTH;
+    top+=length*4;
+
+    indexes[UCNV_EXT_TO_U_INDEX]=top;
+    indexes[UCNV_EXT_TO_U_LENGTH]=length=utm_countItems(extData->toUTable);
+    top+=length*4;
+
+    indexes[UCNV_EXT_TO_U_UCHARS_INDEX]=top;
+    indexes[UCNV_EXT_TO_U_UCHARS_LENGTH]=length=utm_countItems(extData->toUUChars);
+    top+=length*2;
+
+    indexes[UCNV_EXT_FROM_U_UCHARS_INDEX]=top;
+    length=utm_countItems(extData->fromUTableUChars);
+    top+=length*2;
+
+    if(top&3) {
+        /* add padding */
+        *((UChar *)utm_alloc(extData->fromUTableUChars))=0;
+        *((uint32_t *)utm_alloc(extData->fromUTableValues))=0;
+        ++length;
+        top+=2;
+    }
+    indexes[UCNV_EXT_FROM_U_LENGTH]=length;
+
+    indexes[UCNV_EXT_FROM_U_VALUES_INDEX]=top;
+    top+=length*4;
+
+    indexes[UCNV_EXT_FROM_U_BYTES_INDEX]=top;
+    length=utm_countItems(extData->fromUBytes);
+    top+=length;
+
+    if(top&1) {
+        /* add padding */
+        *((uint8_t *)utm_alloc(extData->fromUBytes))=0;
+        ++length;
+        ++top;
+    }
+    indexes[UCNV_EXT_FROM_U_BYTES_LENGTH]=length;
+
+    indexes[UCNV_EXT_FROM_U_STAGE_12_INDEX]=top;
+    indexes[UCNV_EXT_FROM_U_STAGE_1_LENGTH]=length=extData->stage1Top;
+    indexes[UCNV_EXT_FROM_U_STAGE_12_LENGTH]=length+=extData->stage2Top;
+    top+=length*2;
+
+    indexes[UCNV_EXT_FROM_U_STAGE_3_INDEX]=top;
+    length=extData->stage3Top;
+    top+=length*2;
+
+    if(top&3) {
+        /* add padding */
+        extData->stage3[extData->stage3Top++]=0;
+        ++length;
+        top+=2;
+    }
+    indexes[UCNV_EXT_FROM_U_STAGE_3_LENGTH]=length;
+
+    indexes[UCNV_EXT_FROM_U_STAGE_3B_INDEX]=top;
+    indexes[UCNV_EXT_FROM_U_STAGE_3B_LENGTH]=length=extData->stage3bTop;
+    top+=length*4;
+
+    indexes[UCNV_EXT_SIZE]=top;
+
+    /* statistics */
+    indexes[UCNV_EXT_COUNT_BYTES]=
+        (extData->maxInBytes<<16)|
+        (extData->maxOutBytes<<8)|
+        extData->maxBytesPerUChar;
+    indexes[UCNV_EXT_COUNT_UCHARS]=
+        (extData->maxInUChars<<16)|
+        (extData->maxOutUChars<<8)|
+        extData->maxUCharsPerByte;
+
+    indexes[UCNV_EXT_FLAGS]=extData->ucm->ext->unicodeMask;
+
+    /* write the extension data */
+    udata_writeBlock(pData, indexes, sizeof(indexes));
+    udata_writeBlock(pData, utm_getStart(extData->toUTable), indexes[UCNV_EXT_TO_U_LENGTH]*4);
+    udata_writeBlock(pData, utm_getStart(extData->toUUChars), indexes[UCNV_EXT_TO_U_UCHARS_LENGTH]*2);
+
+    udata_writeBlock(pData, utm_getStart(extData->fromUTableUChars), indexes[UCNV_EXT_FROM_U_LENGTH]*2);
+    udata_writeBlock(pData, utm_getStart(extData->fromUTableValues), indexes[UCNV_EXT_FROM_U_LENGTH]*4);
+    udata_writeBlock(pData, utm_getStart(extData->fromUBytes), indexes[UCNV_EXT_FROM_U_BYTES_LENGTH]);
+
+    udata_writeBlock(pData, extData->stage1, extData->stage1Top*2);
+    udata_writeBlock(pData, extData->stage2, extData->stage2Top*2);
+    udata_writeBlock(pData, extData->stage3, extData->stage3Top*2);
+    udata_writeBlock(pData, extData->stage3b, extData->stage3bTop*4);
+
+#if 0
+    {
+        int32_t i, j;
+
+        length=extData->stage1Top;
+        printf("\nstage1[%x]:\n", length);
+
+        for(i=0; i<length; ++i) {
+            if(extData->stage1[i]!=length) {
+                printf("stage1[%04x]=%04x\n", i, extData->stage1[i]);
+            }
+        }
+
+        j=length;
+        length=extData->stage2Top;
+        printf("\nstage2[%x]:\n", length);
+
+        for(i=0; i<length; ++j, ++i) {
+            if(extData->stage2[i]!=0) {
+                printf("stage12[%04x]=%04x\n", j, extData->stage2[i]);
+            }
+        }
+
+        length=extData->stage3Top;
+        printf("\nstage3[%x]:\n", length);
+
+        for(i=0; i<length; ++i) {
+            if(extData->stage3[i]!=0) {
+                printf("stage3[%04x]=%04x\n", i, extData->stage3[i]);
+            }
+        }
+
+        length=extData->stage3bTop;
+        printf("\nstage3b[%x]:\n", length);
+
+        for(i=0; i<length; ++i) {
+            if(extData->stage3b[i]!=0) {
+                printf("stage3b[%04x]=%08x\n", i, extData->stage3b[i]);
+            }
+        }
+    }
+#endif
+
+    if(VERBOSE) {
+        printf("size of extension data: %ld\n", (long)top);
+    }
+
+    /* return the number of bytes that should have been written */
+    return (uint32_t)(headerSize+top);
+}
+
+/* to Unicode --------------------------------------------------------------- */
+
+/*
+ * Remove fromUnicode fallbacks and SUB mappings which are irrelevant for
+ * the toUnicode table.
+ * This includes mappings with MBCS_FROM_U_EXT_FLAG which were suitable
+ * for the base toUnicode table but not for the base fromUnicode table.
+ * The table must be sorted.
+ * Modifies previous data in the reverseMap.
+ */
+static int32_t
+reduceToUMappings(UCMTable *table) {
+    UCMapping *mappings;
+    int32_t *map;
+    int32_t i, j, count;
+    int8_t flag;
+
+    mappings=table->mappings;
+    map=table->reverseMap;
+    count=table->mappingsLength;
+
+    /* leave the map alone for the initial mappings with desired flags */
+    for(i=j=0; i<count; ++i) {
+        flag=mappings[map[i]].f;
+        if(flag!=0 && flag!=3) {
+            break;
+        }
+    }
+
+    /* reduce from here to the rest */
+    for(j=i; i<count; ++i) {
+        flag=mappings[map[i]].f;
+        if(flag==0 || flag==3) {
+            map[j++]=map[i];
+        }
+    }
+
+    return j;
+}
+
+static uint32_t
+getToUnicodeValue(CnvExtData *extData, UCMTable *table, UCMapping *m) {
+    UChar32 *u32;
+    UChar *u;
+    uint32_t value;
+    int32_t u16Length, ratio;
+    UErrorCode errorCode;
+
+    /* write the Unicode result code point or string index */
+    if(m->uLen==1) {
+        u16Length=U16_LENGTH(m->u);
+        value=(uint32_t)(UCNV_EXT_TO_U_MIN_CODE_POINT+m->u);
+    } else {
+        /* the parser enforces m->uLen<=UCNV_EXT_MAX_UCHARS */
+
+        /* get the result code point string and its 16-bit string length */
+        u32=UCM_GET_CODE_POINTS(table, m);
+        errorCode=U_ZERO_ERROR;
+        u_strFromUTF32(NULL, 0, &u16Length, u32, m->uLen, &errorCode);
+        if(U_FAILURE(errorCode) && errorCode!=U_BUFFER_OVERFLOW_ERROR) {
+            exit(errorCode);
+        }
+
+        /* allocate it and put its length and index into the value */
+        value=
+            (((uint32_t)u16Length+UCNV_EXT_TO_U_LENGTH_OFFSET)<<UCNV_EXT_TO_U_LENGTH_SHIFT)|
+            ((uint32_t)utm_countItems(extData->toUUChars));
+        u=utm_allocN(extData->toUUChars, u16Length);
+
+        /* write the result 16-bit string */
+        errorCode=U_ZERO_ERROR;
+        u_strFromUTF32(u, u16Length, NULL, u32, m->uLen, &errorCode);
+        if(U_FAILURE(errorCode) && errorCode!=U_BUFFER_OVERFLOW_ERROR) {
+            exit(errorCode);
+        }
+    }
+    if(m->f==0) {
+        value|=UCNV_EXT_TO_U_ROUNDTRIP_FLAG;
+    }
+
+    /* update statistics */
+    if(m->bLen>extData->maxInBytes) {
+        extData->maxInBytes=m->bLen;
+    }
+    if(u16Length>extData->maxOutUChars) {
+        extData->maxOutUChars=u16Length;
+    }
+
+    ratio=(u16Length+(m->bLen-1))/m->bLen;
+    if(ratio>extData->maxUCharsPerByte) {
+        extData->maxUCharsPerByte=ratio;
+    }
+
+    return value;
+}
+
+/*
+ * Recursive toUTable generator core function.
+ * Preconditions:
+ * - start<limit (There is at least one mapping.)
+ * - The mappings are sorted lexically. (Access is through the reverseMap.)
+ * - All mappings between start and limit have input sequences that share
+ *   the same prefix of unitIndex length, and therefore all of these sequences
+ *   are at least unitIndex+1 long.
+ * - There are only relevant mappings available through the reverseMap,
+ *   see reduceToUMappings().
+ *
+ * One function invocation generates one section table.
+ *
+ * Steps:
+ * 1. Count the number of unique unit values and get the low/high unit values
+ *    that occur at unitIndex.
+ * 2. Allocate the section table with possible optimization for linear access.
+ * 3. Write temporary version of the section table with start indexes of
+ *    subsections, each corresponding to one unit value at unitIndex.
+ * 4. Iterate through the table once more, and depending on the subsection length:
+ *    0: write 0 as a result value (unused byte in linear-access section table)
+ *   >0: if there is one mapping with an input unit sequence of unitIndex+1
+ *       then defaultValue=compute the mapping result for this whole sequence
+ *       else defaultValue=0
+ *
+ *       recurse into the subsection
+ */
+static UBool
+generateToUTable(CnvExtData *extData, UCMTable *table,
+                 int32_t start, int32_t limit, int32_t unitIndex,
+                 uint32_t defaultValue) {
+    UCMapping *mappings, *m;
+    int32_t *map;
+    int32_t i, j, uniqueCount, count, subStart, subLimit;
+
+    uint8_t *bytes;
+    int32_t low, high, prev;
+
+    uint32_t *section;
+
+    mappings=table->mappings;
+    map=table->reverseMap;
+
+    /* step 1: examine the input units; set low, high, uniqueCount */
+    m=mappings+map[start];
+    bytes=UCM_GET_BYTES(table, m);
+    low=bytes[unitIndex];
+    uniqueCount=1;
+
+    prev=high=low;
+    for(i=start+1; i<limit; ++i) {
+        m=mappings+map[i];
+        bytes=UCM_GET_BYTES(table, m);
+        high=bytes[unitIndex];
+
+        if(high!=prev) {
+            prev=high;
+            ++uniqueCount;
+        }
+    }
+
+    /* step 2: allocate the section; set count, section */
+    count=(high-low)+1;
+    if(count<0x100 && (unitIndex==0 || uniqueCount>=(3*count)/4)) {
+        /*
+         * for the root table and for fairly full tables:
+         * allocate for direct, linear array access
+         * by keeping count, to write an entry for each unit value
+         * from low to high
+         * exception: use a compact table if count==0x100 because
+         * that cannot be encoded in the length byte
+         */
+    } else {
+        count=uniqueCount;
+    }
+
+    if(count>=0x100) {
+        fprintf(stderr, "error: toUnicode extension table section overflow: %ld section entries\n", (long)count);
+        return false;
+    }
+
+    /* allocate the section: 1 entry for the header + count for the items */
+    section=(uint32_t *)utm_allocN(extData->toUTable, 1+count);
+
+    /* write the section header */
+    *section++=((uint32_t)count<<UCNV_EXT_TO_U_BYTE_SHIFT)|defaultValue;
+
+    /* step 3: write temporary section table with subsection starts */
+    prev=low-1; /* just before low to prevent empty subsections before low */
+    j=0; /* section table index */
+    for(i=start; i<limit; ++i) {
+        m=mappings+map[i];
+        bytes=UCM_GET_BYTES(table, m);
+        high=bytes[unitIndex];
+
+        if(high!=prev) {
+            /* start of a new subsection for unit high */
+            if(count>uniqueCount) {
+                /* write empty subsections for unused units in a linear table */
+                while(++prev<high) {
+                    section[j++]=((uint32_t)prev<<UCNV_EXT_TO_U_BYTE_SHIFT)|(uint32_t)i;
+                }
+            } else {
+                prev=high;
+            }
+
+            /* write the entry with the subsection start */
+            section[j++]=((uint32_t)high<<UCNV_EXT_TO_U_BYTE_SHIFT)|(uint32_t)i;
+        }
+    }
+    /* assert(j==count) */
+
+    /* step 4: recurse and write results */
+    subLimit=UCNV_EXT_TO_U_GET_VALUE(section[0]);
+    for(j=0; j<count; ++j) {
+        subStart=subLimit;
+        subLimit= (j+1)<count ? UCNV_EXT_TO_U_GET_VALUE(section[j+1]) : limit;
+
+        /* remove the subStart temporary value */
+        section[j]&=~UCNV_EXT_TO_U_VALUE_MASK;
+
+        if(subStart==subLimit) {
+            /* leave the value zero: empty subsection for unused unit in a linear table */
+            continue;
+        }
+
+        /* see if there is exactly one input unit sequence of length unitIndex+1 */
+        defaultValue=0;
+        m=mappings+map[subStart];
+        if(m->bLen==unitIndex+1) {
+            /* do not include this in generateToUTable() */
+            ++subStart;
+
+            if(subStart<subLimit && mappings[map[subStart]].bLen==unitIndex+1) {
+                /* print error for multiple same-input-sequence mappings */
+                fprintf(stderr, "error: multiple mappings from same bytes\n");
+                ucm_printMapping(table, m, stderr);
+                ucm_printMapping(table, mappings+map[subStart], stderr);
+                return false;
+            }
+
+            defaultValue=getToUnicodeValue(extData, table, m);
+        }
+
+        if(subStart==subLimit) {
+            /* write the result for the input sequence ending here */
+            section[j]|=defaultValue;
+        } else {
+            /* write the index to the subsection table */
+            section[j]|=(uint32_t)utm_countItems(extData->toUTable);
+
+            /* recurse */
+            if(!generateToUTable(extData, table, subStart, subLimit, unitIndex+1, defaultValue)) {
+                return false;
+            }
+        }
+    }
+    return true;
+}
+
+/*
+ * Generate the toUTable and toUUChars from the input table.
+ * The input table must be sorted, and all precision flags must be 0..3.
+ * This function will modify the table's reverseMap.
+ */
+static UBool
+makeToUTable(CnvExtData *extData, UCMTable *table) {
+    int32_t toUCount;
+
+    toUCount=reduceToUMappings(table);
+
+    extData->toUTable=utm_open("cnv extension toUTable", 0x10000, UCNV_EXT_TO_U_MIN_CODE_POINT, 4);
+    extData->toUUChars=utm_open("cnv extension toUUChars", 0x10000, UCNV_EXT_TO_U_INDEX_MASK+1, 2);
+
+    return generateToUTable(extData, table, 0, toUCount, 0, 0);
+}
+
+/* from Unicode ------------------------------------------------------------- */
+
+/*
+ * preprocessing:
+ * rebuild reverseMap with mapping indexes for mappings relevant for from Unicode
+ * change each Unicode string to encode all but the first code point in 16-bit form
+ *
+ * generation:
+ * for each unique code point
+ *   write an entry in the 3-stage trie
+ *   check that there is only one single-code point sequence
+ *   start recursion for following 16-bit input units
+ */
+
+/*
+ * Remove toUnicode fallbacks and non-<subchar1> SUB mappings
+ * which are irrelevant for the fromUnicode extension table.
+ * Remove MBCS_FROM_U_EXT_FLAG bits.
+ * Overwrite the reverseMap with an index array to the relevant mappings.
+ * Modify the code point sequences to a generator-friendly format where
+ * the first code points remains unchanged but the following are recoded
+ * into 16-bit Unicode string form.
+ * The table must be sorted.
+ * Destroys previous data in the reverseMap.
+ */
+static int32_t
+prepareFromUMappings(UCMTable *table) {
+    UCMapping *mappings, *m;
+    int32_t *map;
+    int32_t i, j, count;
+    int8_t flag;
+
+    mappings=table->mappings;
+    map=table->reverseMap;
+    count=table->mappingsLength;
+
+    /*
+     * we do not go through the map on input because the mappings are
+     * sorted lexically
+     */
+    m=mappings;
+
+    for(i=j=0; i<count; ++m, ++i) {
+        flag=m->f;
+        if(flag>=0) {
+            flag&=MBCS_FROM_U_EXT_MASK;
+            m->f=flag;
+        }
+        if(flag==0 || flag==1 || (flag==2 && m->bLen==1) || flag==4) {
+            map[j++]=i;
+
+            if(m->uLen>1) {
+                /* recode all but the first code point to 16-bit Unicode */
+                UChar32 *u32;
+                UChar *u;
+                UChar32 c;
+                int32_t q, r;
+
+                u32=UCM_GET_CODE_POINTS(table, m);
+                u=(UChar *)u32; /* destructive in-place recoding */
+                for(r=2, q=1; q<m->uLen; ++q) {
+                    c=u32[q];
+                    U16_APPEND_UNSAFE(u, r, c);
+                }
+
+                /* counts the first code point always at 2 - the first 16-bit unit is at 16-bit index 2 */
+                m->uLen=(int8_t)r;
+            }
+        }
+    }
+
+    return j;
+}
+
+static uint32_t
+getFromUBytesValue(CnvExtData *extData, UCMTable *table, UCMapping *m) {
+    uint8_t *bytes, *resultBytes;
+    uint32_t value;
+    int32_t u16Length, ratio;
+
+    if(m->f==2) {
+        /*
+         * no mapping, <subchar1> preferred
+         *
+         * no need to count in statistics because the subchars are already
+         * counted for maxOutBytes and maxBytesPerUChar in UConverterStaticData,
+         * and this non-mapping does not count for maxInUChars which are always
+         * trivially at least two if counting unmappable supplementary code points
+         */
+        return UCNV_EXT_FROM_U_SUBCHAR1;
+    }
+
+    bytes=UCM_GET_BYTES(table, m);
+    value=0;
+    switch(m->bLen) {
+        /* 1..3: store the bytes in the value word */
+    case 3:
+        value=((uint32_t)*bytes++)<<16;
+    case 2:
+        value|=((uint32_t)*bytes++)<<8;
+    case 1:
+        value|=*bytes;
+        break;
+    default:
+        /* the parser enforces m->bLen<=UCNV_EXT_MAX_BYTES */
+        /* store the bytes in fromUBytes[] and the index in the value word */
+        value=(uint32_t)utm_countItems(extData->fromUBytes);
+        resultBytes=utm_allocN(extData->fromUBytes, m->bLen);
+        uprv_memcpy(resultBytes, bytes, m->bLen);
+        break;
+    }
+    value|=(uint32_t)m->bLen<<UCNV_EXT_FROM_U_LENGTH_SHIFT;
+    if(m->f==0) {
+        value|=UCNV_EXT_FROM_U_ROUNDTRIP_FLAG;
+    } else if(m->f==4) {
+        value|=UCNV_EXT_FROM_U_GOOD_ONE_WAY_FLAG;
+    }
+
+    /* calculate the real UTF-16 length (see recoding in prepareFromUMappings()) */
+    if(m->uLen==1) {
+        u16Length=U16_LENGTH(m->u);
+    } else {
+        u16Length=U16_LENGTH(UCM_GET_CODE_POINTS(table, m)[0])+(m->uLen-2);
+    }
+
+    /* update statistics */
+    if(u16Length>extData->maxInUChars) {
+        extData->maxInUChars=u16Length;
+    }
+    if(m->bLen>extData->maxOutBytes) {
+        extData->maxOutBytes=m->bLen;
+    }
+
+    ratio=(m->bLen+(u16Length-1))/u16Length;
+    if(ratio>extData->maxBytesPerUChar) {
+        extData->maxBytesPerUChar=ratio;
+    }
+
+    return value;
+}
+
+/*
+ * works like generateToUTable(), except that the
+ * output section consists of two arrays, one for input UChars and one
+ * for result values
+ *
+ * also, fromUTable sections are always stored in a compact form for
+ * access via binary search
+ */
+static UBool
+generateFromUTable(CnvExtData *extData, UCMTable *table,
+                   int32_t start, int32_t limit, int32_t unitIndex,
+                   uint32_t defaultValue) {
+    UCMapping *mappings, *m;
+    int32_t *map;
+    int32_t i, j, uniqueCount, count, subStart, subLimit;
+
+    UChar *uchars;
+    UChar32 low, high, prev;
+
+    UChar *sectionUChars;
+    uint32_t *sectionValues;
+
+    mappings=table->mappings;
+    map=table->reverseMap;
+
+    /* step 1: examine the input units; set low, high, uniqueCount */
+    m=mappings+map[start];
+    uchars=(UChar *)UCM_GET_CODE_POINTS(table, m);
+    low=uchars[unitIndex];
+    uniqueCount=1;
+
+    prev=high=low;
+    for(i=start+1; i<limit; ++i) {
+        m=mappings+map[i];
+        uchars=(UChar *)UCM_GET_CODE_POINTS(table, m);
+        high=uchars[unitIndex];
+
+        if(high!=prev) {
+            prev=high;
+            ++uniqueCount;
+        }
+    }
+
+    /* step 2: allocate the section; set count, section */
+    /* the fromUTable always stores for access via binary search */
+    count=uniqueCount;
+
+    /* allocate the section: 1 entry for the header + count for the items */
+    sectionUChars=(UChar *)utm_allocN(extData->fromUTableUChars, 1+count);
+    sectionValues=(uint32_t *)utm_allocN(extData->fromUTableValues, 1+count);
+
+    /* write the section header */
+    *sectionUChars++=(UChar)count;
+    *sectionValues++=defaultValue;
+
+    /* step 3: write temporary section table with subsection starts */
+    prev=low-1; /* just before low to prevent empty subsections before low */
+    j=0; /* section table index */
+    for(i=start; i<limit; ++i) {
+        m=mappings+map[i];
+        uchars=(UChar *)UCM_GET_CODE_POINTS(table, m);
+        high=uchars[unitIndex];
+
+        if(high!=prev) {
+            /* start of a new subsection for unit high */
+            prev=high;
+
+            /* write the entry with the subsection start */
+            sectionUChars[j]=(UChar)high;
+            sectionValues[j]=(uint32_t)i;
+            ++j;
+        }
+    }
+    /* assert(j==count) */
+
+    /* step 4: recurse and write results */
+    subLimit=(int32_t)(sectionValues[0]);
+    for(j=0; j<count; ++j) {
+        subStart=subLimit;
+        subLimit= (j+1)<count ? (int32_t)(sectionValues[j+1]) : limit;
+
+        /* see if there is exactly one input unit sequence of length unitIndex+1 */
+        defaultValue=0;
+        m=mappings+map[subStart];
+        if(m->uLen==unitIndex+1) {
+            /* do not include this in generateToUTable() */
+            ++subStart;
+
+            if(subStart<subLimit && mappings[map[subStart]].uLen==unitIndex+1) {
+                /* print error for multiple same-input-sequence mappings */
+                fprintf(stderr, "error: multiple mappings from same Unicode code points\n");
+                ucm_printMapping(table, m, stderr);
+                ucm_printMapping(table, mappings+map[subStart], stderr);
+                return false;
+            }
+
+            defaultValue=getFromUBytesValue(extData, table, m);
+        }
+
+        if(subStart==subLimit) {
+            /* write the result for the input sequence ending here */
+            sectionValues[j]=defaultValue;
+        } else {
+            /* write the index to the subsection table */
+            sectionValues[j]=(uint32_t)utm_countItems(extData->fromUTableValues);
+
+            /* recurse */
+            if(!generateFromUTable(extData, table, subStart, subLimit, unitIndex+1, defaultValue)) {
+                return false;
+            }
+        }
+    }
+    return true;
+}
+
+/*
+ * add entries to the fromUnicode trie,
+ * assume to be called with code points in ascending order
+ * and use that to build the trie in precompacted form
+ */
+static void
+addFromUTrieEntry(CnvExtData *extData, UChar32 c, uint32_t value) {
+    int32_t i1, i2, i3, i3b, nextOffset, min, newBlock;
+
+    if(value==0) {
+        return;
+    }
+
+    /*
+     * compute the index for each stage,
+     * allocate a stage block if necessary,
+     * and write the stage value
+     */
+    i1=c>>10;
+    if(i1>=extData->stage1Top) {
+        extData->stage1Top=i1+1;
+    }
+
+    nextOffset=(c>>4)&0x3f;
+
+    if(extData->stage1[i1]==0) {
+        /* allocate another block in stage 2; overlap with the previous block */
+        newBlock=extData->stage2Top;
+        min=newBlock-nextOffset; /* minimum block start with overlap */
+        while(min<newBlock && extData->stage2[newBlock-1]==0) {
+            --newBlock;
+        }
+
+        extData->stage1[i1]=(uint16_t)newBlock;
+        extData->stage2Top=newBlock+MBCS_STAGE_2_BLOCK_SIZE;
+        if(extData->stage2Top>UPRV_LENGTHOF(extData->stage2)) {
+            fprintf(stderr, "error: too many stage 2 entries at U+%04x\n", (int)c);
+            exit(U_MEMORY_ALLOCATION_ERROR);
+        }
+    }
+
+    i2=extData->stage1[i1]+nextOffset;
+    nextOffset=c&0xf;
+
+    if(extData->stage2[i2]==0) {
+        /* allocate another block in stage 3; overlap with the previous block */
+        newBlock=extData->stage3Top;
+        min=newBlock-nextOffset; /* minimum block start with overlap */
+        while(min<newBlock && extData->stage3[newBlock-1]==0) {
+            --newBlock;
+        }
+
+        /* round up to a multiple of stage 3 granularity >1 (similar to utrie.c) */
+        newBlock=(newBlock+(UCNV_EXT_STAGE_3_GRANULARITY-1))&~(UCNV_EXT_STAGE_3_GRANULARITY-1);
+        extData->stage2[i2]=(uint16_t)(newBlock>>UCNV_EXT_STAGE_2_LEFT_SHIFT);
+
+        extData->stage3Top=newBlock+MBCS_STAGE_3_BLOCK_SIZE;
+        if(extData->stage3Top>UPRV_LENGTHOF(extData->stage3)) {
+            fprintf(stderr, "error: too many stage 3 entries at U+%04x\n", (int)c);
+            exit(U_MEMORY_ALLOCATION_ERROR);
+        }
+    }
+
+    i3=((int32_t)extData->stage2[i2]<<UCNV_EXT_STAGE_2_LEFT_SHIFT)+nextOffset;
+    /*
+     * assume extData->stage3[i3]==0 because we get
+     * code points in strictly ascending order
+     */
+
+    if(value==UCNV_EXT_FROM_U_SUBCHAR1) {
+        /* <subchar1> SUB mapping, see getFromUBytesValue() and prepareFromUMappings() */
+        extData->stage3[i3]=1;
+
+        /*
+         * precompaction is not optimal for <subchar1> |2 mappings because
+         * stage3 values for them are all the same, unlike for other mappings
+         * which all have unique values;
+         * use a simple compaction of reusing a whole block filled with these
+         * mappings
+         */
+
+        /* is the entire block filled with <subchar1> |2 mappings? */
+        if(nextOffset==MBCS_STAGE_3_BLOCK_SIZE-1) {
+            for(min=i3-nextOffset;
+                min<i3 && extData->stage3[min]==1;
+                ++min) {}
+
+            if(min==i3) {
+                /* the entire block is filled with these mappings */
+                if(extData->stage3Sub1Block!=0) {
+                    /* point to the previous such block and remove this block from stage3 */
+                    extData->stage2[i2]=extData->stage3Sub1Block;
+                    extData->stage3Top-=MBCS_STAGE_3_BLOCK_SIZE;
+                    uprv_memset(extData->stage3+extData->stage3Top, 0, MBCS_STAGE_3_BLOCK_SIZE*2);
+                } else {
+                    /* remember this block's stage2 entry */
+                    extData->stage3Sub1Block=extData->stage2[i2];
+                }
+            }
+        }
+    } else {
+        if((i3b=extData->stage3bTop++)>=UPRV_LENGTHOF(extData->stage3b)) {
+            fprintf(stderr, "error: too many stage 3b entries at U+%04x\n", (int)c);
+            exit(U_MEMORY_ALLOCATION_ERROR);
+        }
+
+        /* roundtrip or fallback mapping */
+        extData->stage3[i3]=(uint16_t)i3b;
+        extData->stage3b[i3b]=value;
+    }
+}
+
+static UBool
+generateFromUTrie(CnvExtData *extData, UCMTable *table, int32_t mapLength) {
+    UCMapping *mappings, *m;
+    int32_t *map;
+    uint32_t value;
+    int32_t subStart, subLimit;
+
+    UChar32 *codePoints;
+    UChar32 c, next;
+
+    if(mapLength==0) {
+        return true;
+    }
+
+    mappings=table->mappings;
+    map=table->reverseMap;
+
+    /*
+     * iterate over same-initial-code point mappings,
+     * enter the initial code point into the trie,
+     * and start a recursion on the corresponding mappings section
+     * with generateFromUTable()
+     */
+    m=mappings+map[0];
+    codePoints=UCM_GET_CODE_POINTS(table, m);
+    next=codePoints[0];
+    subLimit=0;
+    while(subLimit<mapLength) {
+        /* get a new subsection of mappings starting with the same code point */
+        subStart=subLimit;
+        c=next;
+        while(next==c && ++subLimit<mapLength) {
+            m=mappings+map[subLimit];
+            codePoints=UCM_GET_CODE_POINTS(table, m);
+            next=codePoints[0];
+        }
+
+        /*
+         * compute the value for this code point;
+         * if there is a mapping for this code point alone, it is at subStart
+         * because the table is sorted lexically
+         */
+        value=0;
+        m=mappings+map[subStart];
+        codePoints=UCM_GET_CODE_POINTS(table, m);
+        if(m->uLen==1) {
+            /* do not include this in generateFromUTable() */
+            ++subStart;
+
+            if(subStart<subLimit && mappings[map[subStart]].uLen==1) {
+                /* print error for multiple same-input-sequence mappings */
+                fprintf(stderr, "error: multiple mappings from same Unicode code points\n");
+                ucm_printMapping(table, m, stderr);
+                ucm_printMapping(table, mappings+map[subStart], stderr);
+                return false;
+            }
+
+            value=getFromUBytesValue(extData, table, m);
+        }
+
+        if(subStart==subLimit) {
+            /* write the result for this one code point */
+            addFromUTrieEntry(extData, c, value);
+        } else {
+            /* write the index to the subsection table */
+            addFromUTrieEntry(extData, c, (uint32_t)utm_countItems(extData->fromUTableValues));
+
+            /* recurse, starting from 16-bit-unit index 2, the first 16-bit unit after c */
+            if(!generateFromUTable(extData, table, subStart, subLimit, 2, value)) {
+                return false;
+            }
+        }
+    }
+    return true;
+}
+
+/*
+ * Generate the fromU data structures from the input table.
+ * The input table must be sorted, and all precision flags must be 0..3.
+ * This function will modify the table's reverseMap.
+ */
+static UBool
+makeFromUTable(CnvExtData *extData, UCMTable *table) {
+    uint16_t *stage1;
+    int32_t i, stage1Top, fromUCount;
+
+    fromUCount=prepareFromUMappings(table);
+
+    extData->fromUTableUChars=utm_open("cnv extension fromUTableUChars", 0x10000, UCNV_EXT_FROM_U_DATA_MASK+1, 2);
+    extData->fromUTableValues=utm_open("cnv extension fromUTableValues", 0x10000, UCNV_EXT_FROM_U_DATA_MASK+1, 4);
+    extData->fromUBytes=utm_open("cnv extension fromUBytes", 0x10000, UCNV_EXT_FROM_U_DATA_MASK+1, 1);
+
+    /* allocate all-unassigned stage blocks */
+    extData->stage2Top=MBCS_STAGE_2_FIRST_ASSIGNED;
+    extData->stage3Top=MBCS_STAGE_3_FIRST_ASSIGNED;
+
+    /*
+     * stage 3b stores only unique values, and in
+     * index 0: 0 for "no mapping"
+     * index 1: "no mapping" with preference for <subchar1> rather than <subchar>
+     */
+    extData->stage3b[1]=UCNV_EXT_FROM_U_SUBCHAR1;
+    extData->stage3bTop=2;
+
+    /* allocate the first entry in the fromUTable because index 0 means "no result" */
+    utm_alloc(extData->fromUTableUChars);
+    utm_alloc(extData->fromUTableValues);
+
+    if(!generateFromUTrie(extData, table, fromUCount)) {
+        return false;
+    }
+
+    /*
+     * offset the stage 1 trie entries by stage1Top because they will
+     * be stored in a single array
+     */
+    stage1=extData->stage1;
+    stage1Top=extData->stage1Top;
+    for(i=0; i<stage1Top; ++i) {
+        stage1[i]=(uint16_t)(stage1[i]+stage1Top);
+    }
+
+    return true;
+}
+
+/* -------------------------------------------------------------------------- */
+
+static UBool
+CnvExtAddTable(NewConverter *cnvData, UCMTable *table, UConverterStaticData *staticData) {
+    CnvExtData *extData;
+
+    if(table->unicodeMask&UCNV_HAS_SURROGATES) {
+        fprintf(stderr, "error: contains mappings for surrogate code points\n");
+        return false;
+    }
+
+    staticData->conversionType=UCNV_MBCS;
+
+    extData=(CnvExtData *)cnvData;
+
+    /*
+     * assume that the table is sorted
+     *
+     * call the functions in this order because
+     * makeToUTable() modifies the original reverseMap,
+     * makeFromUTable() writes a whole new mapping into reverseMap
+     */
+    return
+        makeToUTable(extData, table) &&
+        makeFromUTable(extData, table);
+}
diff --git a/intl/icu/source/tools/makeconv/genmbcs.cpp b/intl/icu/source/tools/makeconv/genmbcs.cpp
new file mode 100644
index 0000000000..43b96d814f
--- /dev/null
+++ b/intl/icu/source/tools/makeconv/genmbcs.cpp
@@ -0,0 +1,1576 @@
+// © 2016 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
+/*
+*******************************************************************************
+*
+*   Copyright (C) 2000-2016, International Business Machines
+*   Corporation and others.  All Rights Reserved.
+*
+*******************************************************************************
+*   file name:  genmbcs.cpp
+*   encoding:   UTF-8
+*   tab size:   8 (not used)
+*   indentation:4
+*
+*   created on: 2000jul06
+*   created by: Markus W. Scherer
+*/
+
+#include <stdio.h>
+#include "unicode/utypes.h"
+#include "cstring.h"
+#include "cmemory.h"
+#include "unewdata.h"
+#include "ucnv_cnv.h"
+#include "ucnvmbcs.h"
+#include "ucm.h"
+#include "makeconv.h"
+#include "genmbcs.h"
+#include "toolutil.h"
+
+/*
+ * TODO: Split this file into toUnicode, SBCSFromUnicode and MBCSFromUnicode files.
+ * Reduce tests for maxCharLength.
+ */
+
+struct MBCSData {
+    NewConverter newConverter;
+
+    UCMFile *ucm;
+
+    /* toUnicode (state table in ucm->states) */
+    _MBCSToUFallback toUFallbacks[MBCS_MAX_FALLBACK_COUNT];
+    int32_t countToUFallbacks;
+    uint16_t *unicodeCodeUnits;
+
+    /* fromUnicode */
+    uint16_t stage1[MBCS_STAGE_1_SIZE];
+    uint16_t stage2Single[MBCS_STAGE_2_SIZE]; /* stage 2 for single-byte codepages */
+    uint32_t stage2[MBCS_STAGE_2_SIZE]; /* stage 2 for MBCS */
+    uint8_t *fromUBytes;
+    uint32_t stage2Top, stage3Top;
+
+    /* fromUTF8 */
+    uint16_t stageUTF8[0x10000>>MBCS_UTF8_STAGE_SHIFT];  /* allow for utf8Max=0xffff */
+
+    /*
+     * Maximum UTF-8-friendly code point.
+     * 0 if !utf8Friendly, otherwise 0x01ff..0xffff in steps of 0x100.
+     * If utf8Friendly, utf8Max is normally either MBCS_UTF8_MAX or 0xffff.
+     */
+    uint16_t utf8Max;
+
+    UBool utf8Friendly;
+    UBool omitFromU;
+};
+
+/* prototypes */
+U_CDECL_BEGIN
+static void
+MBCSClose(NewConverter *cnvData);
+
+static UBool
+MBCSStartMappings(MBCSData *mbcsData);
+
+static UBool
+MBCSAddToUnicode(MBCSData *mbcsData,
+                 const uint8_t *bytes, int32_t length,
+                 UChar32 c,
+                 int8_t flag);
+
+static UBool
+MBCSIsValid(NewConverter *cnvData,
+            const uint8_t *bytes, int32_t length);
+
+static UBool
+MBCSSingleAddFromUnicode(MBCSData *mbcsData,
+                         const uint8_t *bytes, int32_t length,
+                         UChar32 c,
+                         int8_t flag);
+
+static UBool
+MBCSAddFromUnicode(MBCSData *mbcsData,
+                   const uint8_t *bytes, int32_t length,
+                   UChar32 c,
+                   int8_t flag);
+
+static void
+MBCSPostprocess(MBCSData *mbcsData, const UConverterStaticData *staticData);
+
+static UBool
+MBCSAddTable(NewConverter *cnvData, UCMTable *table, UConverterStaticData *staticData);
+
+static uint32_t
+MBCSWrite(NewConverter *cnvData, const UConverterStaticData *staticData,
+          UNewDataMemory *pData, int32_t tableType);
+U_CDECL_END
+
+/* helper ------------------------------------------------------------------- */
+
+static inline char
+hexDigit(uint8_t digit) {
+    return digit<=9 ? (char)('0'+digit) : (char)('a'-10+digit);
+}
+
+static inline char *
+printBytes(char *buffer, const uint8_t *bytes, int32_t length) {
+    char *s=buffer;
+    while(length>0) {
+        *s++=hexDigit((uint8_t)(*bytes>>4));
+        *s++=hexDigit((uint8_t)(*bytes&0xf));
+        ++bytes;
+        --length;
+    }
+
+    *s=0;
+    return buffer;
+}
+
+/* implementation ----------------------------------------------------------- */
+
+static MBCSData gDummy;
+
+
+U_CFUNC const MBCSData *
+MBCSGetDummy() {
+    uprv_memset(&gDummy, 0, sizeof(MBCSData));
+
+    /*
+     * Set "pessimistic" values which may sometimes move too many
+     * mappings to the extension table (but never too few).
+     * These values cause MBCSOkForBaseFromUnicode() to return false for the
+     * largest set of mappings.
+     * Assume maxCharLength>1.
+     */
+    gDummy.utf8Friendly=true;
+    if(SMALL) {
+        gDummy.utf8Max=0xffff;
+        gDummy.omitFromU=true;
+    } else {
+        gDummy.utf8Max=MBCS_UTF8_MAX;
+    }
+    return &gDummy;
+}
+
+static void
+MBCSInit(MBCSData *mbcsData, UCMFile *ucm) {
+    uprv_memset(mbcsData, 0, sizeof(MBCSData));
+
+    mbcsData->ucm=ucm; /* aliased, not owned */
+
+    mbcsData->newConverter.close=MBCSClose;
+    mbcsData->newConverter.isValid=MBCSIsValid;
+    mbcsData->newConverter.addTable=MBCSAddTable;
+    mbcsData->newConverter.write=MBCSWrite;
+}
+
+U_CFUNC NewConverter *
+MBCSOpen(UCMFile *ucm) {
+    MBCSData *mbcsData=(MBCSData *)uprv_malloc(sizeof(MBCSData));
+    if(mbcsData==nullptr) {
+        printf("out of memory\n");
+        exit(U_MEMORY_ALLOCATION_ERROR);
+    }
+
+    MBCSInit(mbcsData, ucm);
+    return &mbcsData->newConverter;
+}
+
+static void
+MBCSDestruct(MBCSData *mbcsData) {
+    uprv_free(mbcsData->unicodeCodeUnits);
+    uprv_free(mbcsData->fromUBytes);
+}
+
+U_CDECL_BEGIN
+static void
+MBCSClose(NewConverter *cnvData) {
+    MBCSData *mbcsData=(MBCSData *)cnvData;
+    if(mbcsData!=nullptr) {
+        MBCSDestruct(mbcsData);
+        uprv_free(mbcsData);
+    }
+}
+U_CDECL_END
+
+static UBool
+MBCSStartMappings(MBCSData *mbcsData) {
+    int32_t i, sum, maxCharLength,
+            stage2NullLength, stage2AllocLength,
+            stage3NullLength, stage3AllocLength;
+
+    /* toUnicode */
+
+    /* allocate the code unit array and prefill it with "unassigned" values */
+    sum=mbcsData->ucm->states.countToUCodeUnits;
+    if(VERBOSE) {
+        printf("the total number of offsets is 0x%lx=%ld\n", (long)sum, (long)sum);
+    }
+
+    if(sum>0) {
+        mbcsData->unicodeCodeUnits=(uint16_t *)uprv_malloc(sum*sizeof(uint16_t));
+        if(mbcsData->unicodeCodeUnits==nullptr) {
+            fprintf(stderr, "error: out of memory allocating %ld 16-bit code units\n",
+                (long)sum);
+            return false;
+        }
+        for(i=0; i<sum; ++i) {
+            mbcsData->unicodeCodeUnits[i]=0xfffe;
+        }
+    }
+
+    /* fromUnicode */
+    maxCharLength=mbcsData->ucm->states.maxCharLength;
+
+    /* allocate the codepage mappings and preset the first 16 characters to 0 */
+    if(maxCharLength==1) {
+        /* allocate 64k 16-bit results for single-byte codepages */
+        sum=0x20000;
+    } else {
+        /* allocate 1M * maxCharLength bytes for at most 1M mappings */
+        sum=0x100000*maxCharLength;
+    }
+    mbcsData->fromUBytes=(uint8_t *)uprv_malloc(sum);
+    if(mbcsData->fromUBytes==nullptr) {
+        fprintf(stderr, "error: out of memory allocating %ld B for target mappings\n", (long)sum);
+        return false;
+    }
+    uprv_memset(mbcsData->fromUBytes, 0, sum);
+
+    /*
+     * UTF-8-friendly fromUnicode tries: allocate multiple blocks at a time.
+     * See ucnvmbcs.h for details.
+     *
+     * There is code, for example in ucnv_MBCSGetUnicodeSetForUnicode(), which
+     * assumes that the initial stage 2/3 blocks are the all-unassigned ones.
+     * Therefore, we refine the data structure while maintaining this placement
+     * even though it would be convenient to allocate the ASCII block at the
+     * beginning of stage 3, for example.
+     *
+     * UTF-8-friendly fromUnicode tries work from sorted tables and are built
+     * pre-compacted, overlapping adjacent stage 2/3 blocks.
+     * This is necessary because the block allocation and compaction changes
+     * at SBCS_UTF8_MAX or MBCS_UTF8_MAX, and for MBCS tables the additional
+     * stage table uses direct indexes into stage 3, without a multiplier and
+     * thus with a smaller reach.
+     *
+     * Non-UTF-8-friendly fromUnicode tries work from unsorted tables
+     * (because implicit precision is used), and are compacted
+     * in post-processing.
+     *
+     * Preallocation for UTF-8-friendly fromUnicode tries:
+     *
+     * Stage 3:
+     * 64-entry all-unassigned first block followed by ASCII (128 entries).
+     *
+     * Stage 2:
+     * 64-entry all-unassigned first block followed by preallocated
+     * 64-block for ASCII.
+     */
+
+    /* Preallocate ASCII as a linear 128-entry stage 3 block. */
+    stage2NullLength=MBCS_STAGE_2_BLOCK_SIZE;
+    stage2AllocLength=MBCS_STAGE_2_BLOCK_SIZE;
+
+    stage3NullLength=MBCS_UTF8_STAGE_3_BLOCK_SIZE;
+    stage3AllocLength=128; /* ASCII U+0000..U+007f */
+
+    /* Initialize stage 1 for the preallocated blocks. */
+    sum=stage2NullLength;
+    for(i=0; i<(stage2AllocLength>>MBCS_STAGE_2_BLOCK_SIZE_SHIFT); ++i) {
+        mbcsData->stage1[i]=sum;
+        sum+=MBCS_STAGE_2_BLOCK_SIZE;
+    }
+    mbcsData->stage2Top=stage2NullLength+stage2AllocLength; /* ==sum */
+
+    /*
+     * Stage 2 indexes count 16-blocks in stage 3 as follows:
+     * SBCS: directly, indexes increment by 16
+     * MBCS: indexes need to be multiplied by 16*maxCharLength, indexes increment by 1
+     * MBCS UTF-8: directly, indexes increment by 16
+     */
+    if(maxCharLength==1) {
+        sum=stage3NullLength;
+        for(i=0; i<(stage3AllocLength/MBCS_STAGE_3_BLOCK_SIZE); ++i) {
+            mbcsData->stage2Single[mbcsData->stage1[0]+i]=sum;
+            sum+=MBCS_STAGE_3_BLOCK_SIZE;
+        }
+    } else {
+        sum=stage3NullLength/MBCS_STAGE_3_GRANULARITY;
+        for(i=0; i<(stage3AllocLength/MBCS_STAGE_3_BLOCK_SIZE); ++i) {
+            mbcsData->stage2[mbcsData->stage1[0]+i]=sum;
+            sum+=MBCS_STAGE_3_BLOCK_SIZE/MBCS_STAGE_3_GRANULARITY;
+        }
+    }
+
+    sum=stage3NullLength;
+    for(i=0; i<(stage3AllocLength/MBCS_UTF8_STAGE_3_BLOCK_SIZE); ++i) {
+        mbcsData->stageUTF8[i]=sum;
+        sum+=MBCS_UTF8_STAGE_3_BLOCK_SIZE;
+    }
+
+    /*
+     * Allocate a 64-entry all-unassigned first stage 3 block,
+     * for UTF-8-friendly lookup with a trail byte,
+     * plus 128 entries for ASCII.
+     */
+    mbcsData->stage3Top=(stage3NullLength+stage3AllocLength)*maxCharLength; /* ==sum*maxCharLength */
+
+    return true;
+}
+
+/* return true for success */
+static UBool
+setFallback(MBCSData *mbcsData, uint32_t offset, UChar32 c) {
+    int32_t i=ucm_findFallback(mbcsData->toUFallbacks, mbcsData->countToUFallbacks, offset);
+    if(i>=0) {
+        /* if there is already a fallback for this offset, then overwrite it */
+        mbcsData->toUFallbacks[i].codePoint=c;
+        return true;
+    } else {
+        /* if there is no fallback for this offset, then add one */
+        i=mbcsData->countToUFallbacks;
+        if(i>=MBCS_MAX_FALLBACK_COUNT) {
+            fprintf(stderr, "error: too many toUnicode fallbacks, currently at: U+%x\n", (int)c);
+            return false;
+        } else {
+            mbcsData->toUFallbacks[i].offset=offset;
+            mbcsData->toUFallbacks[i].codePoint=c;
+            mbcsData->countToUFallbacks=i+1;
+            return true;
+        }
+    }
+}
+
+/* remove fallback if there is one with this offset; return the code point if there was such a fallback, otherwise -1 */
+static int32_t
+removeFallback(MBCSData *mbcsData, uint32_t offset) {
+    int32_t i=ucm_findFallback(mbcsData->toUFallbacks, mbcsData->countToUFallbacks, offset);
+    if(i>=0) {
+        _MBCSToUFallback *toUFallbacks;
+        int32_t limit, old;
+
+        toUFallbacks=mbcsData->toUFallbacks;
+        limit=mbcsData->countToUFallbacks;
+        old=(int32_t)toUFallbacks[i].codePoint;
+
+        /* copy the last fallback entry here to keep the list contiguous */
+        toUFallbacks[i].offset=toUFallbacks[limit-1].offset;
+        toUFallbacks[i].codePoint=toUFallbacks[limit-1].codePoint;
+        mbcsData->countToUFallbacks=limit-1;
+        return old;
+    } else {
+        return -1;
+    }
+}
+
+/*
+ * isFallback is almost a boolean:
+ * 1 (true)  this is a fallback mapping
+ * 0 (false) this is a precise mapping
+ * -1        the precision of this mapping is not specified
+ */
+static UBool
+MBCSAddToUnicode(MBCSData *mbcsData,
+                 const uint8_t *bytes, int32_t length,
+                 UChar32 c,
+                 int8_t flag) {
+    char buffer[10];
+    uint32_t offset=0;
+    int32_t i=0, entry, old;
+    uint8_t state=0;
+
+    if(mbcsData->ucm->states.countStates==0) {
+        fprintf(stderr, "error: there is no state information!\n");
+        return false;
+    }
+
+    /* for SI/SO (like EBCDIC-stateful), double-byte sequences start in state 1 */
+    if(length==2 && mbcsData->ucm->states.outputType==MBCS_OUTPUT_2_SISO) {
+        state=1;
+    }
+
+    /*
+     * Walk down the state table like in conversion,
+     * much like getNextUChar().
+     * We assume that c<=0x10ffff.
+     */
+    for(i=0;;) {
+        entry=mbcsData->ucm->states.stateTable[state][bytes[i++]];
+        if(MBCS_ENTRY_IS_TRANSITION(entry)) {
+            if(i==length) {
+                fprintf(stderr, "error: byte sequence too short, ends in non-final state %hu: 0x%s (U+%x)\n",
+                    (short)state, printBytes(buffer, bytes, length), (int)c);
+                return false;
+            }
+            state=(uint8_t)MBCS_ENTRY_TRANSITION_STATE(entry);
+            offset+=MBCS_ENTRY_TRANSITION_OFFSET(entry);
+        } else {
+            if(i<length) {
+                fprintf(stderr, "error: byte sequence too long by %d bytes, final state %u: 0x%s (U+%x)\n",
+                    (int)(length-i), state, printBytes(buffer, bytes, length), (int)c);
+                return false;
+            }
+            switch(MBCS_ENTRY_FINAL_ACTION(entry)) {
+            case MBCS_STATE_ILLEGAL:
+                fprintf(stderr, "error: byte sequence ends in illegal state at U+%04x<->0x%s\n",
+                    (int)c, printBytes(buffer, bytes, length));
+                return false;
+            case MBCS_STATE_CHANGE_ONLY:
+                fprintf(stderr, "error: byte sequence ends in state-change-only at U+%04x<->0x%s\n",
+                    (int)c, printBytes(buffer, bytes, length));
+                return false;
+            case MBCS_STATE_UNASSIGNED:
+                fprintf(stderr, "error: byte sequence ends in unassigned state at U+%04x<->0x%s\n",
+                    (int)c, printBytes(buffer, bytes, length));
+                return false;
+            case MBCS_STATE_FALLBACK_DIRECT_16:
+            case MBCS_STATE_VALID_DIRECT_16:
+            case MBCS_STATE_FALLBACK_DIRECT_20:
+            case MBCS_STATE_VALID_DIRECT_20:
+                if(MBCS_ENTRY_SET_STATE(entry, 0)!=MBCS_ENTRY_FINAL(0, MBCS_STATE_VALID_DIRECT_16, 0xfffe)) {
+                    /* the "direct" action's value is not "valid-direct-16-unassigned" any more */
+                    if(MBCS_ENTRY_FINAL_ACTION(entry)==MBCS_STATE_VALID_DIRECT_16 || MBCS_ENTRY_FINAL_ACTION(entry)==MBCS_STATE_FALLBACK_DIRECT_16) {
+                        old=MBCS_ENTRY_FINAL_VALUE(entry);
+                    } else {
+                        old=0x10000+MBCS_ENTRY_FINAL_VALUE(entry);
+                    }
+                    if(flag>=0) {
+                        fprintf(stderr, "error: duplicate codepage byte sequence at U+%04x<->0x%s see U+%04x\n",
+                            (int)c, printBytes(buffer, bytes, length), (int)old);
+                        return false;
+                    } else if(VERBOSE) {
+                        fprintf(stderr, "duplicate codepage byte sequence at U+%04x<->0x%s see U+%04x\n",
+                            (int)c, printBytes(buffer, bytes, length), (int)old);
+                    }
+                    /*
+                     * Continue after the above warning
+                     * if the precision of the mapping is unspecified.
+                     */
+                }
+                /* reassign the correct action code */
+                entry=MBCS_ENTRY_FINAL_SET_ACTION(entry, (MBCS_STATE_VALID_DIRECT_16+(flag==3 ? 2 : 0)+(c>=0x10000 ? 1 : 0)));
+
+                /* put the code point into bits 22..7 for BMP, c-0x10000 into 26..7 for others */
+                if(c<=0xffff) {
+                    entry=MBCS_ENTRY_FINAL_SET_VALUE(entry, c);
+                } else {
+                    entry=MBCS_ENTRY_FINAL_SET_VALUE(entry, c-0x10000);
+                }
+                mbcsData->ucm->states.stateTable[state][bytes[i-1]]=entry;
+                break;
+            case MBCS_STATE_VALID_16:
+                /* bits 26..16 are not used, 0 */
+                /* bits 15..7 contain the final offset delta to one 16-bit code unit */
+                offset+=MBCS_ENTRY_FINAL_VALUE_16(entry);
+                /* check that this byte sequence is still unassigned */
+                if((old=mbcsData->unicodeCodeUnits[offset])!=0xfffe || (old=removeFallback(mbcsData, offset))!=-1) {
+                    if(flag>=0) {
+                        fprintf(stderr, "error: duplicate codepage byte sequence at U+%04x<->0x%s see U+%04x\n",
+                            (int)c, printBytes(buffer, bytes, length), (int)old);
+                        return false;
+                    } else if(VERBOSE) {
+                        fprintf(stderr, "duplicate codepage byte sequence at U+%04x<->0x%s see U+%04x\n",
+                            (int)c, printBytes(buffer, bytes, length), (int)old);
+                    }
+                }
+                if(c>=0x10000) {
+                    fprintf(stderr, "error: code point does not fit into valid-16-bit state at U+%04x<->0x%s\n",
+                        (int)c, printBytes(buffer, bytes, length));
+                    return false;
+                }
+                if(flag>0) {
+                    /* assign only if there is no precise mapping */
+                    if(mbcsData->unicodeCodeUnits[offset]==0xfffe) {
+                        return setFallback(mbcsData, offset, c);
+                    }
+                } else {
+                    mbcsData->unicodeCodeUnits[offset]=(uint16_t)c;
+                }
+                break;
+            case MBCS_STATE_VALID_16_PAIR:
+                /* bits 26..16 are not used, 0 */
+                /* bits 15..7 contain the final offset delta to two 16-bit code units */
+                offset+=MBCS_ENTRY_FINAL_VALUE_16(entry);
+                /* check that this byte sequence is still unassigned */
+                old=mbcsData->unicodeCodeUnits[offset];
+                if(old<0xfffe) {
+                    int32_t real;
+                    if(old<0xd800) {
+                        real=old;
+                    } else if(old<=0xdfff) {
+                        real=0x10000+((old&0x3ff)<<10)+((mbcsData->unicodeCodeUnits[offset+1])&0x3ff);
+                    } else /* old<=0xe001 */ {
+                        real=mbcsData->unicodeCodeUnits[offset+1];
+                    }
+                    if(flag>=0) {
+                        fprintf(stderr, "error: duplicate codepage byte sequence at U+%04x<->0x%s see U+%04x\n",
+                            (int)c, printBytes(buffer, bytes, length), (int)real);
+                        return false;
+                    } else if(VERBOSE) {
+                        fprintf(stderr, "duplicate codepage byte sequence at U+%04x<->0x%s see U+%04x\n",
+                            (int)c, printBytes(buffer, bytes, length), (int)real);
+                    }
+                }
+                if(flag>0) {
+                    /* assign only if there is no precise mapping */
+                    if(old<=0xdbff || old==0xe000) {
+                        /* do nothing */
+                    } else if(c<=0xffff) {
+                        /* set a BMP fallback code point as a pair with 0xe001 */
+                        mbcsData->unicodeCodeUnits[offset++]=0xe001;
+                        mbcsData->unicodeCodeUnits[offset]=(uint16_t)c;
+                    } else {
+                        /* set a fallback surrogate pair with two second surrogates */
+                        mbcsData->unicodeCodeUnits[offset++]=(uint16_t)(0xdbc0+(c>>10));
+                        mbcsData->unicodeCodeUnits[offset]=(uint16_t)(0xdc00+(c&0x3ff));
+                    }
+                } else {
+                    if(c<0xd800) {
+                        /* set a BMP code point */
+                        mbcsData->unicodeCodeUnits[offset]=(uint16_t)c;
+                    } else if(c<=0xffff) {
+                        /* set a BMP code point above 0xd800 as a pair with 0xe000 */
+                        mbcsData->unicodeCodeUnits[offset++]=0xe000;
+                        mbcsData->unicodeCodeUnits[offset]=(uint16_t)c;
+                    } else {
+                        /* set a surrogate pair */
+                        mbcsData->unicodeCodeUnits[offset++]=(uint16_t)(0xd7c0+(c>>10));
+                        mbcsData->unicodeCodeUnits[offset]=(uint16_t)(0xdc00+(c&0x3ff));
+                    }
+                }
+                break;
+            default:
+                /* reserved, must never occur */
+                fprintf(stderr, "internal error: byte sequence reached reserved action code, entry 0x%02x: 0x%s (U+%x)\n",
+                    (int)entry, printBytes(buffer, bytes, length), (int)c);
+                return false;
+            }
+
+            return true;
+        }
+    }
+}
+
+U_CDECL_BEGIN
+/* is this byte sequence valid? (this is almost the same as MBCSAddToUnicode()) */
+static UBool
+MBCSIsValid(NewConverter *cnvData,
+            const uint8_t *bytes, int32_t length) {
+    MBCSData *mbcsData=(MBCSData *)cnvData;
+
+    return (UBool)(1==ucm_countChars(&mbcsData->ucm->states, bytes, length));
+}
+U_CDECL_END
+static UBool
+MBCSSingleAddFromUnicode(MBCSData *mbcsData,
+                         const uint8_t *bytes, int32_t /*length*/,
+                         UChar32 c,
+                         int8_t flag) {
+    uint16_t *stage3, *p;
+    uint32_t idx;
+    uint16_t old;
+    uint8_t b;
+
+    uint32_t blockSize, newTop, i, nextOffset, newBlock, min;
+
+    /* ignore |2 SUB mappings */
+    if(flag==2) {
+        return true;
+    }
+
+    /*
+     * Walk down the triple-stage compact array ("trie") and
+     * allocate parts as necessary.
+     * Note that the first stage 2 and 3 blocks are reserved for all-unassigned mappings.
+     * We assume that length<=maxCharLength and that c<=0x10ffff.
+     */
+    stage3=(uint16_t *)mbcsData->fromUBytes;
+    b=*bytes;
+
+    /* inspect stage 1 */
+    idx=c>>MBCS_STAGE_1_SHIFT;
+    if(mbcsData->utf8Friendly && c<=SBCS_UTF8_MAX) {
+        nextOffset=(c>>MBCS_STAGE_2_SHIFT)&MBCS_STAGE_2_BLOCK_MASK&~(MBCS_UTF8_STAGE_3_BLOCKS-1);
+    } else {
+        nextOffset=(c>>MBCS_STAGE_2_SHIFT)&MBCS_STAGE_2_BLOCK_MASK;
+    }
+    if(mbcsData->stage1[idx]==MBCS_STAGE_2_ALL_UNASSIGNED_INDEX) {
+        /* allocate another block in stage 2 */
+        newBlock=mbcsData->stage2Top;
+        if(mbcsData->utf8Friendly) {
+            min=newBlock-nextOffset; /* minimum block start with overlap */
+            while(min<newBlock && mbcsData->stage2Single[newBlock-1]==0) {
+                --newBlock;
+            }
+        }
+        newTop=newBlock+MBCS_STAGE_2_BLOCK_SIZE;
+
+        if(newTop>MBCS_MAX_STAGE_2_TOP) {
+            fprintf(stderr, "error: too many stage 2 entries at U+%04x<->0x%02x\n", (int)c, b);
+            return false;
+        }
+
+        /*
+         * each stage 2 block contains 64 16-bit words:
+         * 6 code point bits 9..4 with 1 stage 3 index
+         */
+        mbcsData->stage1[idx]=(uint16_t)newBlock;
+        mbcsData->stage2Top=newTop;
+    }
+
+    /* inspect stage 2 */
+    idx=mbcsData->stage1[idx]+nextOffset;
+    if(mbcsData->utf8Friendly && c<=SBCS_UTF8_MAX) {
+        /* allocate 64-entry blocks for UTF-8-friendly lookup */
+        blockSize=MBCS_UTF8_STAGE_3_BLOCK_SIZE;
+        nextOffset=c&MBCS_UTF8_STAGE_3_BLOCK_MASK;
+    } else {
+        blockSize=MBCS_STAGE_3_BLOCK_SIZE;
+        nextOffset=c&MBCS_STAGE_3_BLOCK_MASK;
+    }
+    if(mbcsData->stage2Single[idx]==0) {
+        /* allocate another block in stage 3 */
+        newBlock=mbcsData->stage3Top;
+        if(mbcsData->utf8Friendly) {
+            min=newBlock-nextOffset; /* minimum block start with overlap */
+            while(min<newBlock && stage3[newBlock-1]==0) {
+                --newBlock;
+            }
+        }
+        newTop=newBlock+blockSize;
+
+        if(newTop>MBCS_STAGE_3_SBCS_SIZE) {
+            fprintf(stderr, "error: too many code points at U+%04x<->0x%02x\n", (int)c, b);
+            return false;
+        }
+        /* each block has 16 uint16_t entries */
+        i=idx;
+        while(newBlock<newTop) {
+            mbcsData->stage2Single[i++]=(uint16_t)newBlock;
+            newBlock+=MBCS_STAGE_3_BLOCK_SIZE;
+        }
+        mbcsData->stage3Top=newTop; /* ==newBlock */
+    }
+
+    /* write the codepage entry into stage 3 and get the previous entry */
+    p=stage3+mbcsData->stage2Single[idx]+nextOffset;
+    old=*p;
+    if(flag<=0) {
+        *p=(uint16_t)(0xf00|b);
+    } else if(IS_PRIVATE_USE(c)) {
+        *p=(uint16_t)(0xc00|b);
+    } else {
+        *p=(uint16_t)(0x800|b);
+    }
+
+    /* check that this Unicode code point was still unassigned */
+    if(old>=0x100) {
+        if(flag>=0) {
+            fprintf(stderr, "error: duplicate Unicode code point at U+%04x<->0x%02x see 0x%02x\n",
+                (int)c, b, old&0xff);
+            return false;
+        } else if(VERBOSE) {
+            fprintf(stderr, "duplicate Unicode code point at U+%04x<->0x%02x see 0x%02x\n",
+                (int)c, b, old&0xff);
+        }
+        /* continue after the above warning if the precision of the mapping is unspecified */
+    }
+
+    return true;
+}
+
+static UBool
+MBCSAddFromUnicode(MBCSData *mbcsData,
+                   const uint8_t *bytes, int32_t length,
+                   UChar32 c,
+                   int8_t flag) {
+    char buffer[10];
+    const uint8_t *pb;
+    uint8_t *stage3, *p;
+    uint32_t idx, b, old, stage3Index;
+    int32_t maxCharLength;
+
+    uint32_t blockSize, newTop, i, nextOffset, newBlock, min, overlap, maxOverlap;
+
+    maxCharLength=mbcsData->ucm->states.maxCharLength;
+
+    if( mbcsData->ucm->states.outputType==MBCS_OUTPUT_2_SISO &&
+        (!IGNORE_SISO_CHECK && (*bytes==0xe || *bytes==0xf))
+    ) {
+        fprintf(stderr, "error: illegal mapping to SI or SO for SI/SO codepage: U+%04x<->0x%s\n",
+            (int)c, printBytes(buffer, bytes, length));
+        return false;
+    }
+
+    if(flag==1 && length==1 && *bytes==0) {
+        fprintf(stderr, "error: unable to encode a |1 fallback from U+%04x to 0x%02x\n",
+            (int)c, *bytes);
+        return false;
+    }
+
+    /*
+     * Walk down the triple-stage compact array ("trie") and
+     * allocate parts as necessary.
+     * Note that the first stage 2 and 3 blocks are reserved for
+     * all-unassigned mappings.
+     * We assume that length<=maxCharLength and that c<=0x10ffff.
+     */
+    stage3=mbcsData->fromUBytes;
+
+    /* inspect stage 1 */
+    idx=c>>MBCS_STAGE_1_SHIFT;
+    if(mbcsData->utf8Friendly && c<=mbcsData->utf8Max) {
+        nextOffset=(c>>MBCS_STAGE_2_SHIFT)&MBCS_STAGE_2_BLOCK_MASK&~(MBCS_UTF8_STAGE_3_BLOCKS-1);
+    } else {
+        nextOffset=(c>>MBCS_STAGE_2_SHIFT)&MBCS_STAGE_2_BLOCK_MASK;
+    }
+    if(mbcsData->stage1[idx]==MBCS_STAGE_2_ALL_UNASSIGNED_INDEX) {
+        /* allocate another block in stage 2 */
+        newBlock=mbcsData->stage2Top;
+        if(mbcsData->utf8Friendly) {
+            min=newBlock-nextOffset; /* minimum block start with overlap */
+            while(min<newBlock && mbcsData->stage2[newBlock-1]==0) {
+                --newBlock;
+            }
+        }
+        newTop=newBlock+MBCS_STAGE_2_BLOCK_SIZE;
+
+        if(newTop>MBCS_MAX_STAGE_2_TOP) {
+            fprintf(stderr, "error: too many stage 2 entries at U+%04x<->0x%s\n",
+                (int)c, printBytes(buffer, bytes, length));
+            return false;
+        }
+
+        /*
+         * each stage 2 block contains 64 32-bit words:
+         * 6 code point bits 9..4 with value with bits 31..16 "assigned" flags and bits 15..0 stage 3 index
+         */
+        i=idx;
+        while(newBlock<newTop) {
+            mbcsData->stage1[i++]=(uint16_t)newBlock;
+            newBlock+=MBCS_STAGE_2_BLOCK_SIZE;
+        }
+        mbcsData->stage2Top=newTop; /* ==newBlock */
+    }
+
+    /* inspect stage 2 */
+    idx=mbcsData->stage1[idx]+nextOffset;
+    if(mbcsData->utf8Friendly && c<=mbcsData->utf8Max) {
+        /* allocate 64-entry blocks for UTF-8-friendly lookup */
+        blockSize=MBCS_UTF8_STAGE_3_BLOCK_SIZE*maxCharLength;
+        nextOffset=c&MBCS_UTF8_STAGE_3_BLOCK_MASK;
+    } else {
+        blockSize=MBCS_STAGE_3_BLOCK_SIZE*maxCharLength;
+        nextOffset=c&MBCS_STAGE_3_BLOCK_MASK;
+    }
+    if(mbcsData->stage2[idx]==0) {
+        /* allocate another block in stage 3 */
+        newBlock=mbcsData->stage3Top;
+        if(mbcsData->utf8Friendly && nextOffset>=MBCS_STAGE_3_GRANULARITY) {
+            /*
+             * Overlap stage 3 blocks only in multiples of 16-entry blocks
+             * because of the indexing granularity in stage 2.
+             */
+            maxOverlap=(nextOffset&~(MBCS_STAGE_3_GRANULARITY-1))*maxCharLength;
+            for(overlap=0;
+                overlap<maxOverlap && stage3[newBlock-overlap-1]==0;
+                ++overlap) {}
+
+            overlap=(overlap/MBCS_STAGE_3_GRANULARITY)/maxCharLength;
+            overlap=(overlap*MBCS_STAGE_3_GRANULARITY)*maxCharLength;
+
+            newBlock-=overlap;
+        }
+        newTop=newBlock+blockSize;
+
+        if(newTop>MBCS_STAGE_3_MBCS_SIZE*(uint32_t)maxCharLength) {
+            fprintf(stderr, "error: too many code points at U+%04x<->0x%s\n",
+                (int)c, printBytes(buffer, bytes, length));
+            return false;
+        }
+        /* each block has 16*maxCharLength bytes */
+        i=idx;
+        while(newBlock<newTop) {
+            mbcsData->stage2[i++]=(newBlock/MBCS_STAGE_3_GRANULARITY)/maxCharLength;
+            newBlock+=MBCS_STAGE_3_BLOCK_SIZE*maxCharLength;
+        }
+        mbcsData->stage3Top=newTop; /* ==newBlock */
+    }
+
+    stage3Index=MBCS_STAGE_3_GRANULARITY*(uint32_t)(uint16_t)mbcsData->stage2[idx];
+
+    /* Build an alternate, UTF-8-friendly stage table as well. */
+    if(mbcsData->utf8Friendly && c<=mbcsData->utf8Max) {
+        /* Overflow for uint16_t entries in stageUTF8? */
+        if(stage3Index>0xffff) {
+            /*
+             * This can occur only if the mapping table is nearly perfectly filled and if
+             * utf8Max==0xffff.
+             * (There is no known charset like this. GB 18030 does not map
+             * surrogate code points and LMBCS does not map 256 PUA code points.)
+             *
+             * Otherwise, stage3Index<=MBCS_UTF8_LIMIT<0xffff
+             * (stage3Index can at most reach exactly MBCS_UTF8_LIMIT)
+             * because we have a sorted table and there are at most MBCS_UTF8_LIMIT
+             * mappings with 0<=c<MBCS_UTF8_LIMIT, and there is only also
+             * the initial all-unassigned block in stage3.
+             *
+             * Solution for the overflow: Reduce utf8Max to the next lower value, 0xfeff.
+             *
+             * (See svn revision 20866 of the markus/ucnvutf8 feature branch for
+             * code that causes MBCSAddTable() to rebuild the table not utf8Friendly
+             * in case of overflow. That code was not tested.)
+             */
+            mbcsData->utf8Max=0xfeff;
+        } else {
+            /*
+             * The stage 3 block has been assigned for the regular trie.
+             * Just copy its index into stageUTF8[], without the granularity.
+             */
+            mbcsData->stageUTF8[c>>MBCS_UTF8_STAGE_SHIFT]=(uint16_t)stage3Index;
+        }
+    }
+
+    /* write the codepage bytes into stage 3 and get the previous bytes */
+
+    /* assemble the bytes into a single integer */
+    pb=bytes;
+    b=0;
+    switch(length) {
+    case 4:
+        b=*pb++;
+        U_FALLTHROUGH;
+    case 3:
+        b=(b<<8)|*pb++;
+        U_FALLTHROUGH;
+    case 2:
+        b=(b<<8)|*pb++;
+        U_FALLTHROUGH;
+    case 1:
+    default:
+        b=(b<<8)|*pb++;
+        break;
+    }
+
+    old=0;
+    p=stage3+(stage3Index+nextOffset)*maxCharLength;
+    switch(maxCharLength) {
+    case 2:
+        old=*(uint16_t *)p;
+        *(uint16_t *)p=(uint16_t)b;
+        break;
+    case 3:
+        old=(uint32_t)*p<<16;
+        *p++=(uint8_t)(b>>16);
+        old|=(uint32_t)*p<<8;
+        *p++=(uint8_t)(b>>8);
+        old|=*p;
+        *p=(uint8_t)b;
+        break;
+    case 4:
+        old=*(uint32_t *)p;
+        *(uint32_t *)p=b;
+        break;
+    default:
+        /* will never occur */
+        break;
+    }
+
+    /* check that this Unicode code point was still unassigned */
+    if((mbcsData->stage2[idx+(nextOffset>>MBCS_STAGE_2_SHIFT)]&(1UL<<(16+(c&0xf))))!=0 || old!=0) {
+        if(flag>=0) {
+            fprintf(stderr, "error: duplicate Unicode code point at U+%04x<->0x%s see 0x%02x\n",
+                (int)c, printBytes(buffer, bytes, length), (int)old);
+            return false;
+        } else if(VERBOSE) {
+            fprintf(stderr, "duplicate Unicode code point at U+%04x<->0x%s see 0x%02x\n",
+                (int)c, printBytes(buffer, bytes, length), (int)old);
+        }
+        /* continue after the above warning if the precision of the mapping is
+           unspecified */
+    }
+    if(flag<=0) {
+        /* set the roundtrip flag */
+        mbcsData->stage2[idx+(nextOffset>>4)]|=(1UL<<(16+(c&0xf)));
+    }
+
+    return true;
+}
+
+U_CFUNC UBool
+MBCSOkForBaseFromUnicode(const MBCSData *mbcsData,
+                         const uint8_t *bytes, int32_t length,
+                         UChar32 c, int8_t flag) {
+    /*
+     * A 1:1 mapping does not fit into the MBCS base table's fromUnicode table under
+     * the following conditions:
+     *
+     * - a |2 SUB mapping for <subchar1> (no base table data structure for them)
+     * - a |1 fallback to 0x00 (result value 0, indistinguishable from unmappable entry)
+     * - a multi-byte mapping with leading 0x00 bytes (no explicit length field)
+     *
+     * Some of these tests are redundant with ucm_mappingType().
+     */
+    if( (flag==2 && length==1) ||
+        (flag==1 && bytes[0]==0) || /* testing length==1 would be redundant with the next test */
+        (flag<=1 && length>1 && bytes[0]==0)
+    ) {
+        return false;
+    }
+
+    /*
+     * Additional restrictions for UTF-8-friendly fromUnicode tables,
+     * for code points up to the maximum optimized one:
+     *
+     * - any mapping to 0x00 (result value 0, indistinguishable from unmappable entry)
+     * - any |1 fallback (no roundtrip flags in the optimized table)
+     */
+    if(mbcsData->utf8Friendly && flag<=1 && c<=mbcsData->utf8Max && (bytes[0]==0 || flag==1)) {
+        return false;
+    }
+
+    /*
+     * If we omit the fromUnicode data, we can only store roundtrips there
+     * because only they are recoverable from the toUnicode data.
+     * Fallbacks must go into the extension table.
+     */
+    if(mbcsData->omitFromU && flag!=0) {
+        return false;
+    }
+
+    /* All other mappings do fit into the base table. */
+    return true;
+}
+
+U_CDECL_BEGIN
+/* we can assume that the table only contains 1:1 mappings with <=4 bytes each */
+static UBool
+MBCSAddTable(NewConverter *cnvData, UCMTable *table, UConverterStaticData *staticData) {
+    MBCSData *mbcsData;
+    UCMapping *m;
+    UChar32 c;
+    int32_t i, maxCharLength;
+    int8_t f;
+    UBool isOK, utf8Friendly;
+
+    staticData->unicodeMask=table->unicodeMask;
+    if(staticData->unicodeMask==3) {
+        fprintf(stderr, "error: contains mappings for both supplementary and surrogate code points\n");
+        return false;
+    }
+
+    staticData->conversionType=UCNV_MBCS;
+
+    mbcsData=(MBCSData *)cnvData;
+    maxCharLength=mbcsData->ucm->states.maxCharLength;
+
+    /*
+     * Generation of UTF-8-friendly data requires
+     * a sorted table, which makeconv generates when explicit precision
+     * indicators are used.
+     */
+    mbcsData->utf8Friendly=utf8Friendly=(UBool)((table->flagsType&UCM_FLAGS_EXPLICIT)!=0);
+    if(utf8Friendly) {
+        mbcsData->utf8Max=MBCS_UTF8_MAX;
+        if(SMALL && maxCharLength>1) {
+            mbcsData->omitFromU=true;
+        }
+    } else {
+        mbcsData->utf8Max=0;
+        if(SMALL && maxCharLength>1) {
+            fprintf(stderr,
+                "makeconv warning: --small not available for .ucm files without |0 etc.\n");
+        }
+    }
+
+    if(!MBCSStartMappings(mbcsData)) {
+        return false;
+    }
+
+    staticData->hasFromUnicodeFallback=false;
+    staticData->hasToUnicodeFallback=false;
+
+    isOK=true;
+
+    m=table->mappings;
+    for(i=0; i<table->mappingsLength; ++m, ++i) {
+        c=m->u;
+        f=m->f;
+
+        /*
+         * Small optimization for --small .cnv files:
+         *
+         * If there are fromUnicode mappings above MBCS_UTF8_MAX,
+         * then the file size will be smaller if we make utf8Max larger
+         * because the size increase in stageUTF8 will be more than balanced by
+         * how much less of stage2 needs to be stored.
+         *
+         * There is no point in doing this incrementally because stageUTF8
+         * uses so much less space per block than stage2,
+         * so we immediately increase utf8Max to 0xffff.
+         *
+         * Do not increase utf8Max if it is already at 0xfeff because MBCSAddFromUnicode()
+         * sets it to that value when stageUTF8 overflows.
+         */
+        if( mbcsData->omitFromU && f<=1 &&
+            mbcsData->utf8Max<c && c<=0xffff &&
+            mbcsData->utf8Max<0xfeff
+        ) {
+            mbcsData->utf8Max=0xffff;
+        }
+
+        switch(f) {
+        case -1:
+            /* there was no precision/fallback indicator */
+            /* fall through to set the mappings */
+            U_FALLTHROUGH;
+        case 0:
+            /* set roundtrip mappings */
+            isOK&=MBCSAddToUnicode(mbcsData, m->b.bytes, m->bLen, c, f);
+
+            if(maxCharLength==1) {
+                isOK&=MBCSSingleAddFromUnicode(mbcsData, m->b.bytes, m->bLen, c, f);
+            } else if(MBCSOkForBaseFromUnicode(mbcsData, m->b.bytes, m->bLen, c, f)) {
+                isOK&=MBCSAddFromUnicode(mbcsData, m->b.bytes, m->bLen, c, f);
+            } else {
+                m->f|=MBCS_FROM_U_EXT_FLAG;
+                m->moveFlag=UCM_MOVE_TO_EXT;
+            }
+            break;
+        case 1:
+            /* set only a fallback mapping from Unicode to codepage */
+            if(maxCharLength==1) {
+                staticData->hasFromUnicodeFallback=true;
+                isOK&=MBCSSingleAddFromUnicode(mbcsData, m->b.bytes, m->bLen, c, f);
+            } else if(MBCSOkForBaseFromUnicode(mbcsData, m->b.bytes, m->bLen, c, f)) {
+                staticData->hasFromUnicodeFallback=true;
+                isOK&=MBCSAddFromUnicode(mbcsData, m->b.bytes, m->bLen, c, f);
+            } else {
+                m->f|=MBCS_FROM_U_EXT_FLAG;
+                m->moveFlag=UCM_MOVE_TO_EXT;
+            }
+            break;
+        case 2:
+            /* ignore |2 SUB mappings, except to move <subchar1> mappings to the extension table */
+            if(maxCharLength>1 && m->bLen==1) {
+                m->f|=MBCS_FROM_U_EXT_FLAG;
+                m->moveFlag=UCM_MOVE_TO_EXT;
+            }
+            break;
+        case 3:
+            /* set only a fallback mapping from codepage to Unicode */
+            staticData->hasToUnicodeFallback=true;
+            isOK&=MBCSAddToUnicode(mbcsData, m->b.bytes, m->bLen, c, f);
+            break;
+        case 4:
+            /* move "good one-way" mappings to the extension table */
+            m->f|=MBCS_FROM_U_EXT_FLAG;
+            m->moveFlag=UCM_MOVE_TO_EXT;
+            break;
+        default:
+            /* will not occur because the parser checked it already */
+            fprintf(stderr, "error: illegal fallback indicator %d\n", f);
+            return false;
+        }
+    }
+
+    MBCSPostprocess(mbcsData, staticData);
+
+    return isOK;
+}
+U_CDECL_END
+static UBool
+transformEUC(MBCSData *mbcsData) {
+    uint8_t *p8;
+    uint32_t i, value, oldLength, old3Top;
+    uint8_t b;
+
+    oldLength=mbcsData->ucm->states.maxCharLength;
+    if(oldLength<3) {
+        return false;
+    }
+
+    old3Top=mbcsData->stage3Top;
+
+    /* careful: 2-byte and 4-byte codes are stored in platform endianness! */
+
+    /* test if all first bytes are in {0, 0x8e, 0x8f} */
+    p8=mbcsData->fromUBytes;
+
+#if !U_IS_BIG_ENDIAN
+    if(oldLength==4) {
+        p8+=3;
+    }
+#endif
+
+    for(i=0; i<old3Top; i+=oldLength) {
+        b=p8[i];
+        if(b!=0 && b!=0x8e && b!=0x8f) {
+            /* some first byte does not fit the EUC pattern, nothing to be done */
+            return false;
+        }
+    }
+    /* restore p if it was modified above */
+    p8=mbcsData->fromUBytes;
+
+    /* modify outputType and adjust stage3Top */
+    mbcsData->ucm->states.outputType=(int8_t)(MBCS_OUTPUT_3_EUC+oldLength-3);
+    mbcsData->stage3Top=(old3Top*(oldLength-1))/oldLength;
+
+    /*
+     * EUC-encode all byte sequences;
+     * see "CJKV Information Processing" (1st ed. 1999) from Ken Lunde, O'Reilly,
+     * p. 161 in chapter 4 "Encoding Methods"
+     *
+     * This also must reverse the byte order if the platform is little-endian!
+     */
+    if(oldLength==3) {
+        uint16_t *q=(uint16_t *)p8;
+        for(i=0; i<old3Top; i+=oldLength) {
+            b=*p8;
+            if(b==0) {
+                /* short sequences are stored directly */
+                /* code set 0 or 1 */
+                (*q++)=(uint16_t)((p8[1]<<8)|p8[2]);
+            } else if(b==0x8e) {
+                /* code set 2 */
+                (*q++)=(uint16_t)(((p8[1]&0x7f)<<8)|p8[2]);
+            } else /* b==0x8f */ {
+                /* code set 3 */
+                (*q++)=(uint16_t)((p8[1]<<8)|(p8[2]&0x7f));
+            }
+            p8+=3;
+        }
+    } else /* oldLength==4 */ {
+        uint8_t *q=p8;
+        uint32_t *p32=(uint32_t *)p8;
+        for(i=0; i<old3Top; i+=4) {
+            value=(*p32++);
+            if(value<=0xffffff) {
+                /* short sequences are stored directly */
+                /* code set 0 or 1 */
+                (*q++)=(uint8_t)(value>>16);
+                (*q++)=(uint8_t)(value>>8);
+                (*q++)=(uint8_t)value;
+            } else if(value<=0x8effffff) {
+                /* code set 2 */
+                (*q++)=(uint8_t)((value>>16)&0x7f);
+                (*q++)=(uint8_t)(value>>8);
+                (*q++)=(uint8_t)value;
+            } else /* first byte is 0x8f */ {
+                /* code set 3 */
+                (*q++)=(uint8_t)(value>>16);
+                (*q++)=(uint8_t)((value>>8)&0x7f);
+                (*q++)=(uint8_t)value;
+            }
+        }
+    }
+
+    return true;
+}
+
+/*
+ * Compact stage 2 for SBCS by overlapping adjacent stage 2 blocks as far
+ * as possible. Overlapping is done on unassigned head and tail
+ * parts of blocks in steps of MBCS_STAGE_2_MULTIPLIER.
+ * Stage 1 indexes need to be adjusted accordingly.
+ * This function is very similar to genprops/store.c/compactStage().
+ */
+static void
+singleCompactStage2(MBCSData *mbcsData) {
+    /* this array maps the ordinal number of a stage 2 block to its new stage 1 index */
+    uint16_t map[MBCS_STAGE_2_MAX_BLOCKS];
+    uint16_t i, start, prevEnd, newStart;
+
+    /* enter the all-unassigned first stage 2 block into the map */
+    map[0]=MBCS_STAGE_2_ALL_UNASSIGNED_INDEX;
+
+    /* begin with the first block after the all-unassigned one */
+    start=newStart=MBCS_STAGE_2_FIRST_ASSIGNED;
+    while(start<mbcsData->stage2Top) {
+        prevEnd=(uint16_t)(newStart-1);
+
+        /* find the size of the overlap */
+        for(i=0; i<MBCS_STAGE_2_BLOCK_SIZE && mbcsData->stage2Single[start+i]==0 && mbcsData->stage2Single[prevEnd-i]==0; ++i) {}
+
+        if(i>0) {
+            map[start>>MBCS_STAGE_2_BLOCK_SIZE_SHIFT]=(uint16_t)(newStart-i);
+
+            /* move the non-overlapping indexes to their new positions */
+            start+=i;
+            for(i=(uint16_t)(MBCS_STAGE_2_BLOCK_SIZE-i); i>0; --i) {
+                mbcsData->stage2Single[newStart++]=mbcsData->stage2Single[start++];
+            }
+        } else if(newStart<start) {
+            /* move the indexes to their new positions */
+            map[start>>MBCS_STAGE_2_BLOCK_SIZE_SHIFT]=newStart;
+            for(i=MBCS_STAGE_2_BLOCK_SIZE; i>0; --i) {
+                mbcsData->stage2Single[newStart++]=mbcsData->stage2Single[start++];
+            }
+        } else /* no overlap && newStart==start */ {
+            map[start>>MBCS_STAGE_2_BLOCK_SIZE_SHIFT]=start;
+            start=newStart+=MBCS_STAGE_2_BLOCK_SIZE;
+        }
+    }
+
+    /* adjust stage2Top */
+    if(VERBOSE && newStart<mbcsData->stage2Top) {
+        printf("compacting stage 2 from stage2Top=0x%lx to 0x%lx, saving %ld bytes\n",
+                (unsigned long)mbcsData->stage2Top, (unsigned long)newStart,
+                (long)(mbcsData->stage2Top-newStart)*2);
+    }
+    mbcsData->stage2Top=newStart;
+
+    /* now adjust stage 1 */
+    for(i=0; i<MBCS_STAGE_1_SIZE; ++i) {
+        mbcsData->stage1[i]=map[mbcsData->stage1[i]>>MBCS_STAGE_2_BLOCK_SIZE_SHIFT];
+    }
+}
+
+/* Compact stage 3 for SBCS - same algorithm as above. */
+static void
+singleCompactStage3(MBCSData *mbcsData) {
+    uint16_t *stage3=(uint16_t *)mbcsData->fromUBytes;
+
+    /* this array maps the ordinal number of a stage 3 block to its new stage 2 index */
+    uint16_t map[0x1000];
+    uint16_t i, start, prevEnd, newStart;
+
+    /* enter the all-unassigned first stage 3 block into the map */
+    map[0]=0;
+
+    /* begin with the first block after the all-unassigned one */
+    start=newStart=16;
+    while(start<mbcsData->stage3Top) {
+        prevEnd=(uint16_t)(newStart-1);
+
+        /* find the size of the overlap */
+        for(i=0; i<16 && stage3[start+i]==0 && stage3[prevEnd-i]==0; ++i) {}
+
+        if(i>0) {
+            map[start>>4]=(uint16_t)(newStart-i);
+
+            /* move the non-overlapping indexes to their new positions */
+            start+=i;
+            for(i=(uint16_t)(16-i); i>0; --i) {
+                stage3[newStart++]=stage3[start++];
+            }
+        } else if(newStart<start) {
+            /* move the indexes to their new positions */
+            map[start>>4]=newStart;
+            for(i=16; i>0; --i) {
+                stage3[newStart++]=stage3[start++];
+            }
+        } else /* no overlap && newStart==start */ {
+            map[start>>4]=start;
+            start=newStart+=16;
+        }
+    }
+
+    /* adjust stage3Top */
+    if(VERBOSE && newStart<mbcsData->stage3Top) {
+        printf("compacting stage 3 from stage3Top=0x%lx to 0x%lx, saving %ld bytes\n",
+                (unsigned long)mbcsData->stage3Top, (unsigned long)newStart,
+                (long)(mbcsData->stage3Top-newStart)*2);
+    }
+    mbcsData->stage3Top=newStart;
+
+    /* now adjust stage 2 */
+    for(i=0; i<mbcsData->stage2Top; ++i) {
+        mbcsData->stage2Single[i]=map[mbcsData->stage2Single[i]>>4];
+    }
+}
+
+/*
+ * Compact stage 2 by overlapping adjacent stage 2 blocks as far
+ * as possible. Overlapping is done on unassigned head and tail
+ * parts of blocks in steps of MBCS_STAGE_2_MULTIPLIER.
+ * Stage 1 indexes need to be adjusted accordingly.
+ * This function is very similar to genprops/store.c/compactStage().
+ */
+static void
+compactStage2(MBCSData *mbcsData) {
+    /* this array maps the ordinal number of a stage 2 block to its new stage 1 index */
+    uint16_t map[MBCS_STAGE_2_MAX_BLOCKS];
+    uint16_t i, start, prevEnd, newStart;
+
+    /* enter the all-unassigned first stage 2 block into the map */
+    map[0]=MBCS_STAGE_2_ALL_UNASSIGNED_INDEX;
+
+    /* begin with the first block after the all-unassigned one */
+    start=newStart=MBCS_STAGE_2_FIRST_ASSIGNED;
+    while(start<mbcsData->stage2Top) {
+        prevEnd=(uint16_t)(newStart-1);
+
+        /* find the size of the overlap */
+        for(i=0; i<MBCS_STAGE_2_BLOCK_SIZE && mbcsData->stage2[start+i]==0 && mbcsData->stage2[prevEnd-i]==0; ++i) {}
+
+        if(i>0) {
+            map[start>>MBCS_STAGE_2_BLOCK_SIZE_SHIFT]=(uint16_t)(newStart-i);
+
+            /* move the non-overlapping indexes to their new positions */
+            start+=i;
+            for(i=(uint16_t)(MBCS_STAGE_2_BLOCK_SIZE-i); i>0; --i) {
+                mbcsData->stage2[newStart++]=mbcsData->stage2[start++];
+            }
+        } else if(newStart<start) {
+            /* move the indexes to their new positions */
+            map[start>>MBCS_STAGE_2_BLOCK_SIZE_SHIFT]=newStart;
+            for(i=MBCS_STAGE_2_BLOCK_SIZE; i>0; --i) {
+                mbcsData->stage2[newStart++]=mbcsData->stage2[start++];
+            }
+        } else /* no overlap && newStart==start */ {
+            map[start>>MBCS_STAGE_2_BLOCK_SIZE_SHIFT]=start;
+            start=newStart+=MBCS_STAGE_2_BLOCK_SIZE;
+        }
+    }
+
+    /* adjust stage2Top */
+    if(VERBOSE && newStart<mbcsData->stage2Top) {
+        printf("compacting stage 2 from stage2Top=0x%lx to 0x%lx, saving %ld bytes\n",
+                (unsigned long)mbcsData->stage2Top, (unsigned long)newStart,
+                (long)(mbcsData->stage2Top-newStart)*4);
+    }
+    mbcsData->stage2Top=newStart;
+
+    /* now adjust stage 1 */
+    for(i=0; i<MBCS_STAGE_1_SIZE; ++i) {
+        mbcsData->stage1[i]=map[mbcsData->stage1[i]>>MBCS_STAGE_2_BLOCK_SIZE_SHIFT];
+    }
+}
+
+static void
+MBCSPostprocess(MBCSData *mbcsData, const UConverterStaticData * /*staticData*/) {
+    UCMStates *states;
+    int32_t maxCharLength, stage3Width;
+
+    states=&mbcsData->ucm->states;
+    stage3Width=maxCharLength=states->maxCharLength;
+
+    ucm_optimizeStates(states,
+                       &mbcsData->unicodeCodeUnits,
+                       mbcsData->toUFallbacks, mbcsData->countToUFallbacks,
+                       VERBOSE);
+
+    /* try to compact the fromUnicode tables */
+    if(transformEUC(mbcsData)) {
+        --stage3Width;
+    }
+
+    /*
+     * UTF-8-friendly tries are built precompacted, to cope with variable
+     * stage 3 allocation block sizes.
+     *
+     * Tables without precision indicators cannot be built that way,
+     * because if a block was overlapped with a previous one, then a smaller
+     * code point for the same block would not fit.
+     * Therefore, such tables are not marked UTF-8-friendly and must be
+     * compacted after all mappings are entered.
+     */
+    if(!mbcsData->utf8Friendly) {
+        if(maxCharLength==1) {
+            singleCompactStage3(mbcsData);
+            singleCompactStage2(mbcsData);
+        } else {
+            compactStage2(mbcsData);
+        }
+    }
+
+    if(VERBOSE) {
+        /*uint32_t c, i1, i2, i2Limit, i3;*/
+
+        printf("fromUnicode number of uint%s_t in stage 2: 0x%lx=%lu\n",
+               maxCharLength==1 ? "16" : "32",
+               (unsigned long)mbcsData->stage2Top,
+               (unsigned long)mbcsData->stage2Top);
+        printf("fromUnicode number of %d-byte stage 3 mapping entries: 0x%lx=%lu\n",
+               (int)stage3Width,
+               (unsigned long)mbcsData->stage3Top/stage3Width,
+               (unsigned long)mbcsData->stage3Top/stage3Width);
+#if 0
+        c=0;
+        for(i1=0; i1<MBCS_STAGE_1_SIZE; ++i1) {
+            i2=mbcsData->stage1[i1];
+            if(i2==0) {
+                c+=MBCS_STAGE_2_BLOCK_SIZE*MBCS_STAGE_3_BLOCK_SIZE;
+                continue;
+            }
+            for(i2Limit=i2+MBCS_STAGE_2_BLOCK_SIZE; i2<i2Limit; ++i2) {
+                if(maxCharLength==1) {
+                    i3=mbcsData->stage2Single[i2];
+                } else {
+                    i3=(uint16_t)mbcsData->stage2[i2];
+                }
+                if(i3==0) {
+                    c+=MBCS_STAGE_3_BLOCK_SIZE;
+                    continue;
+                }
+                printf("U+%04lx i1=0x%02lx i2=0x%04lx i3=0x%04lx\n",
+                       (unsigned long)c,
+                       (unsigned long)i1,
+                       (unsigned long)i2,
+                       (unsigned long)i3);
+                c+=MBCS_STAGE_3_BLOCK_SIZE;
+            }
+        }
+#endif
+    }
+}
+
+U_CDECL_BEGIN
+static uint32_t
+MBCSWrite(NewConverter *cnvData, const UConverterStaticData *staticData,
+          UNewDataMemory *pData, int32_t tableType) {
+    MBCSData *mbcsData=(MBCSData *)cnvData;
+    uint32_t stage2Start, stage2Length;
+    uint32_t top, stageUTF8Length=0;
+    int32_t i, stage1Top;
+    uint32_t headerLength;
+
+    _MBCSHeader header=UCNV_MBCS_HEADER_INITIALIZER;
+
+    stage2Length=mbcsData->stage2Top;
+    if(mbcsData->omitFromU) {
+        /* find how much of stage2 can be omitted */
+        int32_t utf8Limit=(int32_t)mbcsData->utf8Max+1;
+        uint32_t st2=0; /*initialized it to avoid compiler warnings */
+
+        i=utf8Limit>>MBCS_STAGE_1_SHIFT;
+        if((utf8Limit&((1<<MBCS_STAGE_1_SHIFT)-1))!=0 && (st2=mbcsData->stage1[i])!=0) {
+            /* utf8Limit is in the middle of an existing stage 2 block */
+            stage2Start=st2+((utf8Limit>>MBCS_STAGE_2_SHIFT)&MBCS_STAGE_2_BLOCK_MASK);
+        } else {
+            /* find the last stage2 block with mappings before utf8Limit */
+            while(i>0 && (st2=mbcsData->stage1[--i])==0) {}
+            /* stage2 up to the end of this block corresponds to stageUTF8 */
+            stage2Start=st2+MBCS_STAGE_2_BLOCK_SIZE;
+        }
+        header.options|=MBCS_OPT_NO_FROM_U;
+        header.fullStage2Length=stage2Length;
+        stage2Length-=stage2Start;
+        if(VERBOSE) {
+            printf("+ omitting %lu out of %lu stage2 entries and %lu fromUBytes\n",
+                    (unsigned long)stage2Start,
+                    (unsigned long)mbcsData->stage2Top,
+                    (unsigned long)mbcsData->stage3Top);
+            printf("+ total size savings: %lu bytes\n", (unsigned long)stage2Start*4+mbcsData->stage3Top);
+        }
+    } else {
+        stage2Start=0;
+    }
+
+    if(staticData->unicodeMask&UCNV_HAS_SUPPLEMENTARY) {
+        stage1Top=MBCS_STAGE_1_SIZE; /* 0x440==1088 */
+    } else {
+        stage1Top=0x40; /* 0x40==64 */
+    }
+
+    /* adjust stage 1 entries to include the size of stage 1 in the offsets to stage 2 */
+    if(mbcsData->ucm->states.maxCharLength==1) {
+        for(i=0; i<stage1Top; ++i) {
+            mbcsData->stage1[i]+=(uint16_t)stage1Top;
+        }
+
+        /* stage2Top/Length have counted 16-bit results, now we need to count bytes */
+        /* also round up to a multiple of 4 bytes */
+        stage2Length=(stage2Length*2+1)&~1;
+
+        /* stage3Top has counted 16-bit results, now we need to count bytes */
+        mbcsData->stage3Top*=2;
+
+        if(mbcsData->utf8Friendly) {
+            header.version[2]=(uint8_t)(SBCS_UTF8_MAX>>8); /* store 0x1f for max==0x1fff */
+        }
+    } else {
+        for(i=0; i<stage1Top; ++i) {
+            mbcsData->stage1[i]+=(uint16_t)stage1Top/2; /* stage 2 contains 32-bit entries, stage 1 16-bit entries */
+        }
+
+        /* stage2Top/Length have counted 32-bit results, now we need to count bytes */
+        stage2Length*=4;
+        /* leave stage2Start counting 32-bit units */
+
+        if(mbcsData->utf8Friendly) {
+            stageUTF8Length=(mbcsData->utf8Max+1)>>MBCS_UTF8_STAGE_SHIFT;
+            header.version[2]=(uint8_t)(mbcsData->utf8Max>>8); /* store 0xd7 for max==0xd7ff */
+        }
+
+        /* stage3Top has already counted bytes */
+    }
+
+    /* round up stage3Top so that the sizes of all data blocks are multiples of 4 */
+    mbcsData->stage3Top=(mbcsData->stage3Top+3)&~3;
+
+    /* fill the header */
+    if(header.options&MBCS_OPT_INCOMPATIBLE_MASK) {
+        header.version[0]=5;
+        if(header.options&MBCS_OPT_NO_FROM_U) {
+            headerLength=10;  /* include fullStage2Length */
+        } else {
+            headerLength=MBCS_HEADER_V5_MIN_LENGTH;  /* 9 */
+        }
+    } else {
+        header.version[0]=4;
+        headerLength=MBCS_HEADER_V4_LENGTH;  /* 8 */
+    }
+    header.version[1]=4;
+    /* header.version[2] set above for utf8Friendly data */
+
+    header.options|=(uint32_t)headerLength;
+
+    header.countStates=mbcsData->ucm->states.countStates;
+    header.countToUFallbacks=mbcsData->countToUFallbacks;
+
+    header.offsetToUCodeUnits=
+        headerLength*4+
+        mbcsData->ucm->states.countStates*1024+
+        mbcsData->countToUFallbacks*sizeof(_MBCSToUFallback);
+    header.offsetFromUTable=
+        header.offsetToUCodeUnits+
+        mbcsData->ucm->states.countToUCodeUnits*2;
+    header.offsetFromUBytes=
+        header.offsetFromUTable+
+        stage1Top*2+
+        stage2Length;
+    header.fromUBytesLength=mbcsData->stage3Top;
+
+    top=header.offsetFromUBytes+stageUTF8Length*2;
+    if(!(header.options&MBCS_OPT_NO_FROM_U)) {
+        top+=header.fromUBytesLength;
+    }
+
+    header.flags=(uint8_t)(mbcsData->ucm->states.outputType);
+
+    if(tableType&TABLE_EXT) {
+        if(top>0xffffff) {
+            fprintf(stderr, "error: offset 0x%lx to extension table exceeds 0xffffff\n", (long)top);
+            return 0;
+        }
+
+        header.flags|=top<<8;
+    }
+
+    /* write the MBCS data */
+    udata_writeBlock(pData, &header, headerLength*4);
+    udata_writeBlock(pData, mbcsData->ucm->states.stateTable, header.countStates*1024);
+    udata_writeBlock(pData, mbcsData->toUFallbacks, mbcsData->countToUFallbacks*sizeof(_MBCSToUFallback));
+    udata_writeBlock(pData, mbcsData->unicodeCodeUnits, mbcsData->ucm->states.countToUCodeUnits*2);
+    udata_writeBlock(pData, mbcsData->stage1, stage1Top*2);
+    if(mbcsData->ucm->states.maxCharLength==1) {
+        udata_writeBlock(pData, mbcsData->stage2Single+stage2Start, stage2Length);
+    } else {
+        udata_writeBlock(pData, mbcsData->stage2+stage2Start, stage2Length);
+    }
+    if(!(header.options&MBCS_OPT_NO_FROM_U)) {
+        udata_writeBlock(pData, mbcsData->fromUBytes, mbcsData->stage3Top);
+    }
+
+    if(stageUTF8Length>0) {
+        udata_writeBlock(pData, mbcsData->stageUTF8, stageUTF8Length*2);
+    }
+
+    /* return the number of bytes that should have been written */
+    return top;
+}
+U_CDECL_END
diff --git a/intl/icu/source/tools/makeconv/genmbcs.h b/intl/icu/source/tools/makeconv/genmbcs.h
new file mode 100644
index 0000000000..9ff1c77633
--- /dev/null
+++ b/intl/icu/source/tools/makeconv/genmbcs.h
@@ -0,0 +1,126 @@
+// © 2016 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
+/*
+*******************************************************************************
+*
+*   Copyright (C) 2000-2008, International Business Machines
+*   Corporation and others.  All Rights Reserved.
+*
+*******************************************************************************
+*   file name:  genmbcs.h
+*   encoding:   UTF-8
+*   tab size:   8 (not used)
+*   indentation:4
+*
+*   created on: 2000jul10
+*   created by: Markus W. Scherer
+*/
+
+#ifndef __GENMBCS_H__
+#define __GENMBCS_H__
+
+#include "makeconv.h"
+
+enum {
+    /*
+     * TODO: Consider using ucnvmbcs.h constants.
+     * However, not all values need to be exactly the same, for example
+     * the xxx_UTF8_MAX values may be different. (Especially SBCS_UTF8_MAX
+     * may be higher in makeconv than in the runtime code because that
+     * affects only a small number of .cnv files [if any] but all
+     * runtime UConverterSharedData objects.
+     */
+    MBCS_STAGE_2_SHIFT=4,
+    MBCS_STAGE_2_BLOCK_SIZE=0x40,       /* =64=1<<6 for 6 bits in stage 2 */
+    MBCS_STAGE_2_BLOCK_SIZE_SHIFT=6,    /* log2(MBCS_STAGE_2_BLOCK_SIZE) */
+    MBCS_STAGE_2_BLOCK_MASK=0x3f,       /* for after shifting by MBCS_STAGE_2_SHIFT */
+    MBCS_STAGE_1_SHIFT=10,
+    MBCS_STAGE_1_BMP_SIZE=0x40, /* 0x10000>>MBCS_STAGE_1_SHIFT, or 16 for one entry per 1k code points on the BMP */
+    MBCS_STAGE_1_SIZE=0x440,    /* 0x110000>>MBCS_STAGE_1_SHIFT, or 17*64 for one entry per 1k code points */
+    MBCS_STAGE_2_SIZE=0xfbc0,   /* 0x10000-MBCS_STAGE_1_SIZE: stages 1 & 2 share a 16-bit-indexed array */
+    MBCS_MAX_STAGE_2_TOP=MBCS_STAGE_2_SIZE,
+    MBCS_STAGE_2_MAX_BLOCKS=MBCS_STAGE_2_SIZE>>MBCS_STAGE_2_BLOCK_SIZE_SHIFT,
+
+    MBCS_STAGE_2_ALL_UNASSIGNED_INDEX=0, /* stage 1 entry for the all-unassigned stage 2 block */
+    MBCS_STAGE_2_FIRST_ASSIGNED=MBCS_STAGE_2_BLOCK_SIZE, /* start of the first stage 2 block after the all-unassigned one */
+
+    MBCS_STAGE_3_BLOCK_SIZE=16,         /* =16=1<<4 for 4 bits in stage 3 */
+    MBCS_STAGE_3_BLOCK_MASK=0xf,
+    MBCS_STAGE_3_FIRST_ASSIGNED=MBCS_STAGE_3_BLOCK_SIZE, /* start of the first stage 3 block after the all-unassigned one */
+
+    MBCS_STAGE_3_GRANULARITY=16,        /* =1<<4: MBCS stage 2 indexes are shifted left 4 */
+    MBCS_STAGE_3_SBCS_SIZE=0x10000,     /* max 64k mappings for SBCS */
+    MBCS_STAGE_3_MBCS_SIZE=0x10000*MBCS_STAGE_3_GRANULARITY, /* max mappings for MBCS */
+
+    /*
+     * SBCS_UTF8_MAX: Maximum code point with UTF-8-friendly SBCS data structures.
+     * Possible values are 0x01ff..0xffff, in steps of 0x100.
+     *
+     * Unlike for MBCS, this constant only affects the stage 3 block allocation size;
+     * there is no additional stage 1/2 table stored in the .cnv file.
+     * The max value should be at least 0x7ff to cover 2-byte UTF-8.
+     * 0xfff also covers a number other small scripts which have legacy charsets
+     * (like Thai).
+     * Higher values up to 0x1fff are harmless and potentially useful because
+     * that covers small-script blocks which usually have either dense mappings
+     * or no mappings at all.
+     * Starting at U+2000, there are mostly symbols and format characters
+     * with a low density of SBCS mappings, which would result in more wasted
+     * stage 3 entries with the larger block size.
+     */
+    SBCS_UTF8_MAX=0x1fff,
+
+    /*
+     * MBCS_UTF8_MAX: Maximum code point with UTF-8-friendly MBCS data structures.
+     * Possible values are 0x01ff..0xffff, in steps of 0x100.
+     *
+     * Note that with 0xffff, MBCSAddFromUnicode() may overflow the additional UTF-8 stage table
+     * with extreme input data. The function checks for this overflow.
+     *
+     * 0xd7ff is chosen for the majority of common characters including Unihan and Hangul.
+     * At U+d800 there are mostly surrogates, private use codes, compatibility characters, etc.
+     * Larger values cause slightly larger MBCS .cnv files.
+     */
+    MBCS_UTF8_MAX=0xd7ff,
+    MBCS_UTF8_LIMIT=MBCS_UTF8_MAX+1,    /* =0xd800 */
+
+    MBCS_UTF8_STAGE_SHIFT=6,
+    MBCS_UTF8_STAGE_3_BLOCK_SIZE=0x40,  /* =64=1<<6 for 6 bits from last trail byte */
+    MBCS_UTF8_STAGE_3_BLOCK_MASK=0x3f,
+
+    /* size of the single-stage table for up to U+d7ff (used instead of stage1/2) */
+    MBCS_UTF8_STAGE_SIZE=MBCS_UTF8_LIMIT>>MBCS_UTF8_STAGE_SHIFT, /* =0x360 */
+
+    MBCS_FROM_U_EXT_FLAG=0x10,          /* UCMapping.f bit for base table mappings that fit into the base toU table */
+    MBCS_FROM_U_EXT_MASK=0x0f,          /* but need to go into the extension fromU table */
+
+    /* =4 number of regular stage 3 blocks for final UTF-8 trail byte */
+    MBCS_UTF8_STAGE_3_BLOCKS=MBCS_UTF8_STAGE_3_BLOCK_SIZE/MBCS_STAGE_3_BLOCK_SIZE,
+
+    MBCS_MAX_FALLBACK_COUNT=8192
+};
+
+U_CFUNC NewConverter *
+MBCSOpen(UCMFile *ucm);
+
+struct MBCSData;
+typedef struct MBCSData MBCSData;
+
+/*
+ * Get a dummy MBCSData for use with MBCSOkForBaseFromUnicode()
+ * for creating an extension-only file.
+ * Assume maxCharLength>1.
+ */
+U_CFUNC const MBCSData *
+MBCSGetDummy(void);
+
+/* Test if a 1:1 mapping fits into the MBCS base table's fromUnicode structure. */
+U_CFUNC UBool
+MBCSOkForBaseFromUnicode(const MBCSData *mbcsData,
+                         const uint8_t *bytes, int32_t length,
+                         UChar32 c, int8_t flag);
+
+U_CFUNC NewConverter *
+CnvExtOpen(UCMFile *ucm);
+
+#endif /* __GENMBCS_H__ */
diff --git a/intl/icu/source/tools/makeconv/makeconv.1.in b/intl/icu/source/tools/makeconv/makeconv.1.in
new file mode 100644
index 0000000000..e42d5127b5
--- /dev/null
+++ b/intl/icu/source/tools/makeconv/makeconv.1.in
@@ -0,0 +1,114 @@
+.\" Hey, Emacs! This is -*-nroff-*- you know...
+.\"
+.\" makeconv.1: manual page for the makeconv utility
+.\"
+.\" Copyright (C) 2016 and later: Unicode, Inc. and others.
+.\" License & terms of use: http://www.unicode.org/copyright.html
+.\" Copyright (C) 2000-2002 IBM, Inc. and others.
+.\"
+.\" Manual page by Yves Arrouye <yves@realnames.com>.
+.\"
+.TH MAKECONV 1 "16 April 2002" "ICU MANPAGE" "ICU @VERSION@ Manual"
+.SH NAME
+.B makeconv
+\- compile a converter table
+.SH SYNOPSIS
+.B makeconv
+[
+.BR "\-h\fP, \fB\-?\fP, \fB\-\-help"
+]
+[
+.BR "\-c\fP, \fB\-\-copyright"
+]
+[
+.BR "\-v\fP, \fB\-\-verbose"
+]
+[
+.BI "\-d\fP, \fB\-\-destdir" " destination"
+]
+.IR convertertable " .\|.\|."
+.SH DESCRIPTION
+.B makeconv
+converts the ICU converter table
+.I convertertable
+into a binary file. The binary file has the same base name as
+.I convertertable
+but has a
+.B .cnv
+extension (instead of the typical
+.B .ucm
+extension of the
+.I convertertable
+file).
+This binary file can then be read directly by ICU, or used by
+.BR pkgdata (1)
+for incorporation into a larger archive or library.
+.PP
+The
+.I convertertable
+must be in the ICU ucm (Unicode Codepage Mapping) format in order to
+be understood by
+.BR makeconv .
+The ICU ucm format is similar to the IBM NLTC upmap/tpmap/rpmap files.
+Comments in the
+.I convertertable
+are handled as follows. If a comment (starting with a `#' sign) that
+is after some text does contain the fallback indicator `|' then only
+the text starting with the `#' sign, and ending before the `|' sign,
+is ignored.
+Otherwise, or if the comment is the first thing on the line,
+the comment runs up to the end of the line. This special
+handling of comments is to accommodate the practice of putting fallback
+information in comments in the strict IBM NLTC ucmap format.
+.PP
+Note that new converters will be automatically found by ICU after their
+installation in ICU's data directory. They do not need to
+be listed in the
+.BR convrtrs.txt (5)
+converters aliases file in order to be available to applications using ICU.
+They do need to be listed there if one wants to give them aliases, or
+tags, though.
+.SH OPTIONS
+.TP
+.BR "\-h\fP, \fB\-?\fP, \fB\-\-help"
+Print help about usage and exit.
+.TP
+.BR "\-c\fP, \fB\-\-copyright"
+Include a copyright notice in the binary data.
+.TP
+.BR "\-v\fP, \fB\-\-verbose"
+Display extra informative messages during execution.
+.TP
+.BI "\-d\fP, \fB\-\-destdir" " destination"
+Set the destination directory to
+.IR destination .
+The default destination directory is specified by the environment variable
+.BR ICU_DATA .
+.SH CAVEATS
+If an existing converter table is changed and recompiled using
+.BR makeconv ,
+the resulting binary file must be packaged in the same way that it was
+packaged initially. For example, if converters were grouped together in
+an archive or a library with
+.BR pkgdata (1),
+then the archive or library must be rebuilt with the new binary file.
+A standalone binary converter file will not take precedence over a
+packaged one.
+.SH ENVIRONMENT
+.TP 10
+.B ICU_DATA
+Specifies the directory containing ICU data. Defaults to
+.BR @thepkgicudatadir@/@PACKAGE@/@VERSION@/ .
+Some tools in ICU depend on the presence of the trailing slash. It is thus
+important to make sure that it is present if
+.B ICU_DATA
+is set.
+.SH VERSION
+@VERSION@
+.SH COPYRIGHT
+Copyright (C) 2000 IBM, Inc. and others.
+.SH SEE ALSO
+.BR convrtrs.txt (5) 
+.br
+.BR pkgdata (1)
+
diff --git a/intl/icu/source/tools/makeconv/makeconv.cpp b/intl/icu/source/tools/makeconv/makeconv.cpp
new file mode 100644
index 0000000000..b14b4316f3
--- /dev/null
+++ b/intl/icu/source/tools/makeconv/makeconv.cpp
@@ -0,0 +1,862 @@
+// © 2016 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
+/*
+ ********************************************************************************
+ *
+ *   Copyright (C) 1998-2015, International Business Machines
+ *   Corporation and others.  All Rights Reserved.
+ *
+ ********************************************************************************
+ *
+ *
+ *  makeconv.cpp:
+ *  tool creating a binary (compressed) representation of the conversion mapping
+ *  table (IBM NLTC ucmap format).
+ *
+ *  05/04/2000    helena     Added fallback mapping into the picture...
+ *  06/29/2000  helena      Major rewrite of the callback APIs.
+ */
+
+#include <stdio.h>
+#include "unicode/putil.h"
+#include "unicode/ucnv_err.h"
+#include "charstr.h"
+#include "ucnv_bld.h"
+#include "ucnv_imp.h"
+#include "ucnv_cnv.h"
+#include "cstring.h"
+#include "cmemory.h"
+#include "uinvchar.h"
+#include "filestrm.h"
+#include "toolutil.h"
+#include "uoptions.h"
+#include "unicode/udata.h"
+#include "unewdata.h"
+#include "uparse.h"
+#include "ucm.h"
+#include "makeconv.h"
+#include "genmbcs.h"
+
+#define DEBUG 0
+
+typedef struct ConvData {
+    UCMFile *ucm;
+    NewConverter *cnvData, *extData;
+    UConverterSharedData sharedData;
+    UConverterStaticData staticData;
+} ConvData;
+
+static void
+initConvData(ConvData *data) {
+    uprv_memset(data, 0, sizeof(ConvData));
+    data->sharedData.structSize=sizeof(UConverterSharedData);
+    data->staticData.structSize=sizeof(UConverterStaticData);
+    data->sharedData.staticData=&data->staticData;
+}
+
+static void
+cleanupConvData(ConvData *data) {
+    if(data!=nullptr) {
+        if(data->cnvData!=nullptr) {
+            data->cnvData->close(data->cnvData);
+            data->cnvData=nullptr;
+        }
+        if(data->extData!=nullptr) {
+            data->extData->close(data->extData);
+            data->extData=nullptr;
+        }
+        ucm_close(data->ucm);
+        data->ucm=nullptr;
+    }
+}
+
+/*
+ * from ucnvstat.c - static prototypes of data-based converters
+ */
+U_CAPI const UConverterStaticData * ucnv_converterStaticData[UCNV_NUMBER_OF_SUPPORTED_CONVERTER_TYPES];
+
+/*
+ * Global - verbosity
+ */
+UBool VERBOSE = false;
+UBool QUIET = false;
+UBool SMALL = false;
+UBool IGNORE_SISO_CHECK = false;
+
+static void
+createConverter(ConvData *data, const char* converterName, UErrorCode *pErrorCode);
+
+/*
+ * Set up the UNewData and write the converter..
+ */
+static void
+writeConverterData(ConvData *data, const char *cnvName, const char *cnvDir, UErrorCode *status);
+
+UBool haveCopyright=true;
+
+static UDataInfo dataInfo={
+    sizeof(UDataInfo),
+    0,
+
+    U_IS_BIG_ENDIAN,
+    U_CHARSET_FAMILY,
+    sizeof(char16_t),
+    0,
+
+    {0x63, 0x6e, 0x76, 0x74},     /* dataFormat="cnvt" */
+    {6, 2, 0, 0},                 /* formatVersion */
+    {0, 0, 0, 0}                  /* dataVersion (calculated at runtime) */
+};
+
+static void
+writeConverterData(ConvData *data, const char *cnvName, const char *cnvDir, UErrorCode *status)
+{
+    UNewDataMemory *mem = nullptr;
+    uint32_t sz2;
+    uint32_t size = 0;
+    int32_t tableType;
+
+    if(U_FAILURE(*status))
+      {
+        return;
+      }
+
+    tableType=TABLE_NONE;
+    if(data->cnvData!=nullptr) {
+        tableType|=TABLE_BASE;
+    }
+    if(data->extData!=nullptr) {
+        tableType|=TABLE_EXT;
+    }
+
+    mem = udata_create(cnvDir, "cnv", cnvName, &dataInfo, haveCopyright ? U_COPYRIGHT_STRING : nullptr, status);
+
+    if(U_FAILURE(*status))
+      {
+        fprintf(stderr, "Couldn't create the udata %s.%s: %s\n",
+                cnvName,
+                "cnv",
+                u_errorName(*status));
+        return;
+      }
+
+    if(VERBOSE)
+      {
+        printf("- Opened udata %s.%s\n", cnvName, "cnv");
+      }
+
+
+    /* all read only, clean, platform independent data.  Mmmm. :)  */
+    udata_writeBlock(mem, &data->staticData, sizeof(UConverterStaticData));
+    size += sizeof(UConverterStaticData); /* Is 4-aligned  - by size */
+    /* Now, write the table */
+    if(tableType&TABLE_BASE) {
+        size += data->cnvData->write(data->cnvData, &data->staticData, mem, tableType);
+    }
+    if(tableType&TABLE_EXT) {
+        size += data->extData->write(data->extData, &data->staticData, mem, tableType);
+    }
+
+    sz2 = udata_finish(mem, status);
+    if(size != sz2)
+    {
+        fprintf(stderr, "error: wrote %u bytes to the .cnv file but counted %u bytes\n", (int)sz2, (int)size);
+        *status=U_INTERNAL_PROGRAM_ERROR;
+    }
+    if(VERBOSE)
+    {
+      printf("- Wrote %u bytes to the udata.\n", (int)sz2);
+    }
+}
+
+enum {
+    OPT_HELP_H,
+    OPT_HELP_QUESTION_MARK,
+    OPT_COPYRIGHT,
+    OPT_VERSION,
+    OPT_DESTDIR,
+    OPT_VERBOSE,
+    OPT_SMALL,
+    OPT_IGNORE_SISO_CHECK,
+    OPT_QUIET,
+    OPT_SOURCEDIR,
+
+    OPT_COUNT
+};
+
+static UOption options[]={
+    UOPTION_HELP_H,
+    UOPTION_HELP_QUESTION_MARK,
+    UOPTION_COPYRIGHT,
+    UOPTION_VERSION,
+    UOPTION_DESTDIR,
+    UOPTION_VERBOSE,
+    { "small", nullptr, nullptr, nullptr, '\1', UOPT_NO_ARG, 0 },
+    { "ignore-siso-check", nullptr, nullptr, nullptr, '\1', UOPT_NO_ARG, 0 },
+    UOPTION_QUIET,
+    UOPTION_SOURCEDIR,
+};
+
+int main(int argc, char* argv[])
+{
+    ConvData data;
+    char cnvName[UCNV_MAX_FULL_FILE_NAME_LENGTH];
+
+    U_MAIN_INIT_ARGS(argc, argv);
+
+    /* Set up the ICU version number */
+    UVersionInfo icuVersion;
+    u_getVersion(icuVersion);
+    uprv_memcpy(&dataInfo.dataVersion, &icuVersion, sizeof(UVersionInfo));
+
+    /* preset then read command line options */
+    options[OPT_DESTDIR].value=u_getDataDirectory();
+    argc=u_parseArgs(argc, argv, UPRV_LENGTHOF(options), options);
+
+    if(options[OPT_VERSION].doesOccur) {
+        printf("makeconv version %u.%u, ICU tool to read .ucm codepage mapping files and write .cnv files\n",
+               dataInfo.formatVersion[0], dataInfo.formatVersion[1]);
+        printf("%s\n", U_COPYRIGHT_STRING);
+        exit(0);
+    }
+
+    /* error handling, printing usage message */
+    if(argc<0) {
+        fprintf(stderr,
+            "error in command line argument \"%s\"\n",
+            argv[-argc]);
+    } else if(argc<2) {
+        argc=-1;
+    }
+    if(argc<0 || options[OPT_HELP_H].doesOccur || options[OPT_HELP_QUESTION_MARK].doesOccur) {
+        FILE *stdfile=argc<0 ? stderr : stdout;
+        fprintf(stdfile,
+            "usage: %s [-options] files...\n"
+            "\tread .ucm codepage mapping files and write .cnv files\n"
+            "options:\n"
+            "\t-h or -? or --help  this usage text\n"
+            "\t-V or --version     show a version message\n"
+            "\t-c or --copyright   include a copyright notice\n"
+            "\t-d or --destdir     destination directory, followed by the path\n"
+            "\t-v or --verbose     Turn on verbose output\n"
+            "\t-q or --quiet       do not display warnings and progress\n"
+            "\t-s or --sourcedir   source directory, followed by the path\n",
+            argv[0]);
+        fprintf(stdfile,
+            "\t      --small       Generate smaller .cnv files. They will be\n"
+            "\t                    significantly smaller but may not be compatible with\n"
+            "\t                    older versions of ICU and will require heap memory\n"
+            "\t                    allocation when loaded.\n"
+            "\t      --ignore-siso-check         Use SI/SO other than 0xf/0xe.\n");
+        return argc<0 ? U_ILLEGAL_ARGUMENT_ERROR : U_ZERO_ERROR;
+    }
+
+    /* get the options values */
+    haveCopyright = options[OPT_COPYRIGHT].doesOccur;
+    const char *destdir = options[OPT_DESTDIR].value;
+    VERBOSE = options[OPT_VERBOSE].doesOccur;
+    QUIET = options[OPT_QUIET].doesOccur;
+    SMALL = options[OPT_SMALL].doesOccur;
+
+    if (options[OPT_IGNORE_SISO_CHECK].doesOccur) {
+        IGNORE_SISO_CHECK = true;
+    }
+
+    icu::CharString outFileName;
+    UErrorCode err = U_ZERO_ERROR;
+    if (destdir != nullptr && *destdir != 0) {
+        outFileName.append(destdir, err).ensureEndsWithFileSeparator(err);
+        if (U_FAILURE(err)) {
+            return err;
+        }
+    }
+    int32_t outBasenameStart = outFileName.length();
+
+#if DEBUG
+    {
+      int i;
+      printf("makeconv: processing %d files...\n", argc - 1);
+      for(i=1; i<argc; ++i) {
+        printf("%s ", argv[i]);
+      }
+      printf("\n");
+      fflush(stdout);
+    }
+#endif
+
+    UBool printFilename = (UBool) (argc > 2 || VERBOSE);
+    icu::CharString pathBuf;
+    for (++argv; --argc; ++argv)
+    {
+        UErrorCode localError = U_ZERO_ERROR;
+        const char *arg = getLongPathname(*argv);
+
+        const char* sourcedir = options[OPT_SOURCEDIR].value;
+        if (sourcedir != nullptr && *sourcedir != 0 && uprv_strcmp(sourcedir, ".") != 0) {
+            pathBuf.clear();
+            pathBuf.appendPathPart(sourcedir, localError);
+            pathBuf.appendPathPart(arg, localError);
+            arg = pathBuf.data();
+        }
+
+        /*produces the right destination path for display*/
+        outFileName.truncate(outBasenameStart);
+        if (outBasenameStart != 0)
+        {
+            /* find the last file sepator */
+            const char *basename = findBasename(arg);
+            outFileName.append(basename, localError);
+        }
+        else
+        {
+            outFileName.append(arg, localError);
+        }
+        if (U_FAILURE(localError)) {
+            return localError;
+        }
+
+        /*removes the extension if any is found*/
+        int32_t lastDotIndex = outFileName.lastIndexOf('.');
+        if (lastDotIndex >= outBasenameStart) {
+            outFileName.truncate(lastDotIndex);
+        }
+
+        /* the basename without extension is the converter name */
+        if ((outFileName.length() - outBasenameStart) >= UPRV_LENGTHOF(cnvName)) {
+            fprintf(stderr, "converter name %s too long\n", outFileName.data() + outBasenameStart);
+            return U_BUFFER_OVERFLOW_ERROR;
+        }
+        uprv_strcpy(cnvName, outFileName.data() + outBasenameStart);
+
+        /*Adds the target extension*/
+        outFileName.append(CONVERTER_FILE_EXTENSION, localError);
+        if (U_FAILURE(localError)) {
+            return localError;
+        }
+
+#if DEBUG
+        printf("makeconv: processing %s  ...\n", arg);
+        fflush(stdout);
+#endif
+        initConvData(&data);
+        createConverter(&data, arg, &localError);
+
+        if (U_FAILURE(localError))
+        {
+            /* if an error is found, print out an error msg and keep going */
+            fprintf(stderr, "Error creating converter for \"%s\" file for \"%s\" (%s)\n",
+                    outFileName.data(), arg, u_errorName(localError));
+            if(U_SUCCESS(err)) {
+                err = localError;
+            }
+        }
+        else
+        {
+            /* Insure the static data name matches the  file name */
+            /* Changed to ignore directory and only compare base name
+             LDH 1/2/08*/
+            char *p;
+            p = strrchr(cnvName, U_FILE_SEP_CHAR); /* Find last file separator */
+
+            if(p == nullptr)            /* OK, try alternate */
+            {
+                p = strrchr(cnvName, U_FILE_ALT_SEP_CHAR);
+                if(p == nullptr)
+                {
+                    p=cnvName; /* If no separators, no problem */
+                }
+            }
+            else
+            {
+                p++;   /* If found separator, don't include it in compare */
+            }
+            if(uprv_stricmp(p,data.staticData.name) && !QUIET)
+            {
+                fprintf(stderr, "Warning: %s%s claims to be '%s'\n",
+                    cnvName,  CONVERTER_FILE_EXTENSION,
+                    data.staticData.name);
+            }
+
+            uprv_strcpy((char*)data.staticData.name, cnvName);
+
+            if(!uprv_isInvariantString((char*)data.staticData.name, -1)) {
+                fprintf(stderr,
+                    "Error: A converter name must contain only invariant characters.\n"
+                    "%s is not a valid converter name.\n",
+                    data.staticData.name);
+                if(U_SUCCESS(err)) {
+                    err = U_INVALID_TABLE_FORMAT;
+                }
+            }
+
+            localError = U_ZERO_ERROR;
+            writeConverterData(&data, cnvName, destdir, &localError);
+
+            if(U_FAILURE(localError))
+            {
+                /* if an error is found, print out an error msg and keep going*/
+                fprintf(stderr, "Error writing \"%s\" file for \"%s\" (%s)\n", outFileName.data(), arg,
+                    u_errorName(localError));
+                if(U_SUCCESS(err)) {
+                    err = localError;
+                }
+            }
+            else if (printFilename)
+            {
+                puts(outFileName.data() + outBasenameStart);
+            }
+        }
+        fflush(stdout);
+        fflush(stderr);
+
+        cleanupConvData(&data);
+    }
+
+    return err;
+}
+
+static void
+getPlatformAndCCSIDFromName(const char *name, int8_t *pPlatform, int32_t *pCCSID) {
+    if( (name[0]=='i' || name[0]=='I') &&
+        (name[1]=='b' || name[1]=='B') &&
+        (name[2]=='m' || name[2]=='M')
+    ) {
+        name+=3;
+        if(*name=='-') {
+            ++name;
+        }
+        *pPlatform=UCNV_IBM;
+        *pCCSID=(int32_t)uprv_strtoul(name, nullptr, 10);
+    } else {
+        *pPlatform=UCNV_UNKNOWN;
+        *pCCSID=0;
+    }
+}
+
+static void
+readHeader(ConvData *data,
+           FileStream* convFile,
+           UErrorCode *pErrorCode) {
+    char line[1024];
+    char *s, *key, *value;
+    const UConverterStaticData *prototype;
+    UConverterStaticData *staticData;
+
+    if(U_FAILURE(*pErrorCode)) {
+        return;
+    }
+
+    staticData=&data->staticData;
+    staticData->platform=UCNV_IBM;
+    staticData->subCharLen=0;
+
+    while(T_FileStream_readLine(convFile, line, sizeof(line))) {
+        /* basic parsing and handling of state-related items */
+        if(ucm_parseHeaderLine(data->ucm, line, &key, &value)) {
+            continue;
+        }
+
+        /* stop at the beginning of the mapping section */
+        if(uprv_strcmp(line, "CHARMAP")==0) {
+            break;
+        }
+
+        /* collect the information from the header field, ignore unknown keys */
+        if(uprv_strcmp(key, "code_set_name")==0) {
+            if(*value!=0) {
+                uprv_strcpy((char *)staticData->name, value);
+                getPlatformAndCCSIDFromName(value, &staticData->platform, &staticData->codepage);
+            }
+        } else if(uprv_strcmp(key, "subchar")==0) {
+            uint8_t bytes[UCNV_EXT_MAX_BYTES];
+            int8_t length;
+
+            s=value;
+            length=ucm_parseBytes(bytes, line, (const char **)&s);
+            if(1<=length && length<=4 && *s==0) {
+                staticData->subCharLen=length;
+                uprv_memcpy(staticData->subChar, bytes, length);
+            } else {
+                fprintf(stderr, "error: illegal <subchar> %s\n", value);
+                *pErrorCode=U_INVALID_TABLE_FORMAT;
+                return;
+            }
+        } else if(uprv_strcmp(key, "subchar1")==0) {
+            uint8_t bytes[UCNV_EXT_MAX_BYTES];
+
+            s=value;
+            if(1==ucm_parseBytes(bytes, line, (const char **)&s) && *s==0) {
+                staticData->subChar1=bytes[0];
+            } else {
+                fprintf(stderr, "error: illegal <subchar1> %s\n", value);
+                *pErrorCode=U_INVALID_TABLE_FORMAT;
+                return;
+            }
+        }
+    }
+
+    /* copy values from the UCMFile to the static data */
+    staticData->maxBytesPerChar=(int8_t)data->ucm->states.maxCharLength;
+    staticData->minBytesPerChar=(int8_t)data->ucm->states.minCharLength;
+    staticData->conversionType=data->ucm->states.conversionType;
+
+    if(staticData->conversionType==UCNV_UNSUPPORTED_CONVERTER) {
+        fprintf(stderr, "ucm error: missing conversion type (<uconv_class>)\n");
+        *pErrorCode=U_INVALID_TABLE_FORMAT;
+        return;
+    }
+
+    /*
+     * Now that we know the type, copy any 'default' values from the table.
+     * We need not check the type any further because the parser only
+     * recognizes what we have prototypes for.
+     *
+     * For delta (extension-only) tables, copy values from the base file
+     * instead, see createConverter().
+     */
+    if(data->ucm->baseName[0]==0) {
+        prototype=ucnv_converterStaticData[staticData->conversionType];
+        if(prototype!=nullptr) {
+            if(staticData->name[0]==0) {
+                uprv_strcpy((char *)staticData->name, prototype->name);
+            }
+
+            if(staticData->codepage==0) {
+                staticData->codepage=prototype->codepage;
+            }
+
+            if(staticData->platform==0) {
+                staticData->platform=prototype->platform;
+            }
+
+            if(staticData->minBytesPerChar==0) {
+                staticData->minBytesPerChar=prototype->minBytesPerChar;
+            }
+
+            if(staticData->maxBytesPerChar==0) {
+                staticData->maxBytesPerChar=prototype->maxBytesPerChar;
+            }
+
+            if(staticData->subCharLen==0) {
+                staticData->subCharLen=prototype->subCharLen;
+                if(prototype->subCharLen>0) {
+                    uprv_memcpy(staticData->subChar, prototype->subChar, prototype->subCharLen);
+                }
+            }
+        }
+    }
+
+    if(data->ucm->states.outputType<0) {
+        data->ucm->states.outputType=(int8_t)data->ucm->states.maxCharLength-1;
+    }
+
+    if( staticData->subChar1!=0 &&
+            (staticData->minBytesPerChar>1 ||
+                (staticData->conversionType!=UCNV_MBCS &&
+                 staticData->conversionType!=UCNV_EBCDIC_STATEFUL))
+    ) {
+        fprintf(stderr, "error: <subchar1> defined for a type other than MBCS or EBCDIC_STATEFUL\n");
+        *pErrorCode=U_INVALID_TABLE_FORMAT;
+    }
+}
+
+/* return true if a base table was read, false for an extension table */
+static UBool
+readFile(ConvData *data, const char* converterName,
+         UErrorCode *pErrorCode) {
+    char line[1024];
+    char *end;
+    FileStream *convFile;
+
+    UCMStates *baseStates;
+    UBool dataIsBase;
+
+    if(U_FAILURE(*pErrorCode)) {
+        return false;
+    }
+
+    data->ucm=ucm_open();
+
+    convFile=T_FileStream_open(converterName, "r");
+    if(convFile==nullptr) {
+        *pErrorCode=U_FILE_ACCESS_ERROR;
+        return false;
+    }
+
+    readHeader(data, convFile, pErrorCode);
+    if(U_FAILURE(*pErrorCode)) {
+        return false;
+    }
+
+    if(data->ucm->baseName[0]==0) {
+        dataIsBase=true;
+        baseStates=&data->ucm->states;
+        ucm_processStates(baseStates, IGNORE_SISO_CHECK);
+    } else {
+        dataIsBase=false;
+        baseStates=nullptr;
+    }
+
+    /* read the base table */
+    ucm_readTable(data->ucm, convFile, dataIsBase, baseStates, pErrorCode);
+    if(U_FAILURE(*pErrorCode)) {
+        return false;
+    }
+
+    /* read an extension table if there is one */
+    while(T_FileStream_readLine(convFile, line, sizeof(line))) {
+        end=uprv_strchr(line, 0);
+        while(line<end &&
+              (*(end-1)=='\n' || *(end-1)=='\r' || *(end-1)==' ' || *(end-1)=='\t')) {
+            --end;
+        }
+        *end=0;
+
+        if(line[0]=='#' || u_skipWhitespace(line)==end) {
+            continue; /* ignore empty and comment lines */
+        }
+
+        if(0==uprv_strcmp(line, "CHARMAP")) {
+            /* read the extension table */
+            ucm_readTable(data->ucm, convFile, false, baseStates, pErrorCode);
+        } else {
+            fprintf(stderr, "unexpected text after the base mapping table\n");
+        }
+        break;
+    }
+
+    T_FileStream_close(convFile);
+
+    if(data->ucm->base->flagsType==UCM_FLAGS_MIXED || data->ucm->ext->flagsType==UCM_FLAGS_MIXED) {
+        fprintf(stderr, "error: some entries have the mapping precision (with '|'), some do not\n");
+        *pErrorCode=U_INVALID_TABLE_FORMAT;
+    }
+
+    return dataIsBase;
+}
+
+static void
+createConverter(ConvData *data, const char *converterName, UErrorCode *pErrorCode) {
+    ConvData baseData;
+    UBool dataIsBase;
+
+    UConverterStaticData *staticData;
+    UCMStates *states, *baseStates;
+
+    if(U_FAILURE(*pErrorCode)) {
+        return;
+    }
+
+    initConvData(data);
+
+    dataIsBase=readFile(data, converterName, pErrorCode);
+    if(U_FAILURE(*pErrorCode)) {
+        return;
+    }
+
+    staticData=&data->staticData;
+    states=&data->ucm->states;
+
+    if(dataIsBase) {
+        /*
+         * Build a normal .cnv file with a base table
+         * and an optional extension table.
+         */
+        data->cnvData=MBCSOpen(data->ucm);
+        if(data->cnvData==nullptr) {
+            *pErrorCode=U_MEMORY_ALLOCATION_ERROR;
+
+        } else if(!data->cnvData->isValid(data->cnvData,
+                            staticData->subChar, staticData->subCharLen)
+        ) {
+            fprintf(stderr, "       the substitution character byte sequence is illegal in this codepage structure!\n");
+            *pErrorCode=U_INVALID_TABLE_FORMAT;
+
+        } else if(staticData->subChar1!=0 &&
+                    !data->cnvData->isValid(data->cnvData, &staticData->subChar1, 1)
+        ) {
+            fprintf(stderr, "       the subchar1 byte is illegal in this codepage structure!\n");
+            *pErrorCode=U_INVALID_TABLE_FORMAT;
+
+        } else if(
+            data->ucm->ext->mappingsLength>0 &&
+            !ucm_checkBaseExt(states, data->ucm->base, data->ucm->ext, data->ucm->ext, false)
+        ) {
+            *pErrorCode=U_INVALID_TABLE_FORMAT;
+        } else if(data->ucm->base->flagsType&UCM_FLAGS_EXPLICIT) {
+            /* sort the table so that it can be turned into UTF-8-friendly data */
+            ucm_sortTable(data->ucm->base);
+        }
+
+        if(U_SUCCESS(*pErrorCode)) {
+            if(
+                /* add the base table after ucm_checkBaseExt()! */
+                !data->cnvData->addTable(data->cnvData, data->ucm->base, &data->staticData)
+            ) {
+                *pErrorCode=U_INVALID_TABLE_FORMAT;
+            } else {
+                /*
+                 * addTable() may have requested moving more mappings to the extension table
+                 * if they fit into the base toUnicode table but not into the
+                 * base fromUnicode table.
+                 * (Especially for UTF-8-friendly fromUnicode tables.)
+                 * Such mappings will have the MBCS_FROM_U_EXT_FLAG set, which causes them
+                 * to be excluded from the extension toUnicode data.
+                 * See MBCSOkForBaseFromUnicode() for which mappings do not fit into
+                 * the base fromUnicode table.
+                 */
+                ucm_moveMappings(data->ucm->base, data->ucm->ext);
+                ucm_sortTable(data->ucm->ext);
+                if(data->ucm->ext->mappingsLength>0) {
+                    /* prepare the extension table, if there is one */
+                    data->extData=CnvExtOpen(data->ucm);
+                    if(data->extData==nullptr) {
+                        *pErrorCode=U_MEMORY_ALLOCATION_ERROR;
+                    } else if(
+                        !data->extData->addTable(data->extData, data->ucm->ext, &data->staticData)
+                    ) {
+                        *pErrorCode=U_INVALID_TABLE_FORMAT;
+                    }
+                }
+            }
+        }
+    } else {
+        /* Build an extension-only .cnv file. */
+        char baseFilename[500];
+        char *basename;
+
+        initConvData(&baseData);
+
+        /* assemble a path/filename for data->ucm->baseName */
+        uprv_strcpy(baseFilename, converterName);
+        basename=(char *)findBasename(baseFilename);
+        uprv_strcpy(basename, data->ucm->baseName);
+        uprv_strcat(basename, ".ucm");
+
+        /* read the base table */
+        dataIsBase=readFile(&baseData, baseFilename, pErrorCode);
+        if(U_FAILURE(*pErrorCode)) {
+            return;
+        } else if(!dataIsBase) {
+            fprintf(stderr, "error: the <icu:base> file \"%s\" is not a base table file\n", baseFilename);
+            *pErrorCode=U_INVALID_TABLE_FORMAT;
+        } else {
+            /* prepare the extension table */
+            data->extData=CnvExtOpen(data->ucm);
+            if(data->extData==nullptr) {
+                *pErrorCode=U_MEMORY_ALLOCATION_ERROR;
+            } else {
+                /* fill in gaps in extension file header fields */
+                UCMapping *m, *mLimit;
+                uint8_t fallbackFlags;
+
+                baseStates=&baseData.ucm->states;
+                if(states->conversionType==UCNV_DBCS) {
+                    staticData->minBytesPerChar=(int8_t)(states->minCharLength=2);
+                } else if(states->minCharLength==0) {
+                    staticData->minBytesPerChar=(int8_t)(states->minCharLength=baseStates->minCharLength);
+                }
+                if(states->maxCharLength<states->minCharLength) {
+                    staticData->maxBytesPerChar=(int8_t)(states->maxCharLength=baseStates->maxCharLength);
+                }
+
+                if(staticData->subCharLen==0) {
+                    uprv_memcpy(staticData->subChar, baseData.staticData.subChar, 4);
+                    staticData->subCharLen=baseData.staticData.subCharLen;
+                }
+                /*
+                 * do not copy subChar1 -
+                 * only use what is explicitly specified
+                 * because it cannot be unset in the extension file header
+                 */
+
+                /* get the fallback flags */
+                fallbackFlags=0;
+                for(m=baseData.ucm->base->mappings, mLimit=m+baseData.ucm->base->mappingsLength;
+                    m<mLimit && fallbackFlags!=3;
+                    ++m
+                ) {
+                    if(m->f==1) {
+                        fallbackFlags|=1;
+                    } else if(m->f==3) {
+                        fallbackFlags|=2;
+                    }
+                }
+
+                if(fallbackFlags&1) {
+                    staticData->hasFromUnicodeFallback=true;
+                }
+                if(fallbackFlags&2) {
+                    staticData->hasToUnicodeFallback=true;
+                }
+
+                if(1!=ucm_countChars(baseStates, staticData->subChar, staticData->subCharLen)) {
+                    fprintf(stderr, "       the substitution character byte sequence is illegal in this codepage structure!\n");
+                    *pErrorCode=U_INVALID_TABLE_FORMAT;
+
+                } else if(staticData->subChar1!=0 && 1!=ucm_countChars(baseStates, &staticData->subChar1, 1)) {
+                    fprintf(stderr, "       the subchar1 byte is illegal in this codepage structure!\n");
+                    *pErrorCode=U_INVALID_TABLE_FORMAT;
+
+                } else if(
+                    !ucm_checkValidity(data->ucm->ext, baseStates) ||
+                    !ucm_checkBaseExt(baseStates, baseData.ucm->base, data->ucm->ext, data->ucm->ext, false)
+                ) {
+                    *pErrorCode=U_INVALID_TABLE_FORMAT;
+                } else {
+                    if(states->maxCharLength>1) {
+                        /*
+                         * When building a normal .cnv file with a base table
+                         * for an MBCS (not SBCS) table with explicit precision flags,
+                         * the MBCSAddTable() function marks some mappings for moving
+                         * to the extension table.
+                         * They fit into the base toUnicode table but not into the
+                         * base fromUnicode table.
+                         * (Note: We do have explicit precision flags because they are
+                         * required for extension table generation, and
+                         * ucm_checkBaseExt() verified it.)
+                         *
+                         * We do not call MBCSAddTable() here (we probably could)
+                         * so we need to do the analysis before building the extension table.
+                         * We assume that MBCSAddTable() will build a UTF-8-friendly table.
+                         * Redundant mappings in the extension table are ok except they cost some size.
+                         *
+                         * Do this after ucm_checkBaseExt().
+                         */
+                        const MBCSData *mbcsData=MBCSGetDummy();
+                        int32_t needsMove=0;
+                        for(m=baseData.ucm->base->mappings, mLimit=m+baseData.ucm->base->mappingsLength;
+                            m<mLimit;
+                            ++m
+                        ) {
+                            if(!MBCSOkForBaseFromUnicode(mbcsData, m->b.bytes, m->bLen, m->u, m->f)) {
+                                m->f|=MBCS_FROM_U_EXT_FLAG;
+                                m->moveFlag=UCM_MOVE_TO_EXT;
+                                ++needsMove;
+                            }
+                        }
+
+                        if(needsMove!=0) {
+                            ucm_moveMappings(baseData.ucm->base, data->ucm->ext);
+                            ucm_sortTable(data->ucm->ext);
+                        }
+                    }
+                    if(!data->extData->addTable(data->extData, data->ucm->ext, &data->staticData)) {
+                        *pErrorCode=U_INVALID_TABLE_FORMAT;
+                    }
+                }
+            }
+        }
+
+        cleanupConvData(&baseData);
+    }
+}
+
+/*
+ * Hey, Emacs, please set the following:
+ *
+ * Local Variables:
+ * indent-tabs-mode: nil
+ * End:
+ *
+ */
diff --git a/intl/icu/source/tools/makeconv/makeconv.h b/intl/icu/source/tools/makeconv/makeconv.h
new file mode 100644
index 0000000000..addc2cb3e7
--- /dev/null
+++ b/intl/icu/source/tools/makeconv/makeconv.h
@@ -0,0 +1,62 @@
+// © 2016 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
+/*
+*******************************************************************************
+*
+*   Copyright (C) 2000-2010, International Business Machines
+*   Corporation and others.  All Rights Reserved.
+*
+*******************************************************************************
+*   file name:  makeconv.h
+*   encoding:   UTF-8
+*   tab size:   8 (not used)
+*   indentation:4
+*
+*   created on: 2000nov01
+*   created by: Markus W. Scherer
+*/
+
+#ifndef __MAKECONV_H__
+#define __MAKECONV_H__
+
+#include "unicode/utypes.h"
+#include "ucnv_bld.h"
+#include "unewdata.h"
+#include "ucm.h"
+
+/* exports from makeconv.c */
+U_CFUNC UBool VERBOSE;
+U_CFUNC UBool SMALL;
+U_CFUNC UBool IGNORE_SISO_CHECK;
+
+/* converter table type for writing */
+enum {
+    TABLE_NONE,
+    TABLE_BASE,
+    TABLE_EXT,
+    TABLE_BASE_AND_EXT
+};
+
+/* abstract converter generator struct, C++ - style */
+struct NewConverter;
+typedef struct NewConverter NewConverter;
+
+U_CDECL_BEGIN
+struct NewConverter {
+    void
+    (* U_CALLCONV_FPTR close)(NewConverter *cnvData);
+
+    /** is this byte sequence valid? */
+    UBool
+    (*U_CALLCONV_FPTR isValid)(NewConverter *cnvData,
+               const uint8_t *bytes, int32_t length);
+
+    UBool
+    (*U_CALLCONV_FPTR addTable)(NewConverter *cnvData, UCMTable *table, UConverterStaticData *staticData);
+
+    uint32_t
+    (*U_CALLCONV_FPTR write)(NewConverter *cnvData, const UConverterStaticData *staticData,
+             UNewDataMemory *pData, int32_t tableType);
+};
+U_CDECL_END
+#endif /* __MAKECONV_H__ */
diff --git a/intl/icu/source/tools/makeconv/makeconv.vcxproj b/intl/icu/source/tools/makeconv/makeconv.vcxproj
new file mode 100644
index 0000000000..1ec8ec709e
--- /dev/null
+++ b/intl/icu/source/tools/makeconv/makeconv.vcxproj
@@ -0,0 +1,87 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project DefaultTargets="Build" ToolsVersion="14.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup Label="Globals">
+    <ProjectGuid>{F5AD9738-1A3D-4906-B9C4-A7D9CE33DC2C}</ProjectGuid>
+  </PropertyGroup>
+  <PropertyGroup Label="Configuration">
+    <ConfigurationType>Application</ConfigurationType>
+    <UseOfMfc>false</UseOfMfc>
+    <CharacterSet>MultiByte</CharacterSet>
+  </PropertyGroup>
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.Default.props" />
+  <!-- The following import will include the 'default' configuration options for VS projects. -->
+  <Import Project="..\..\allinone\Build.Windows.ProjectConfiguration.props" />
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
+  <ImportGroup Label="ExtensionSettings">
+  </ImportGroup>
+  <PropertyGroup Label="UserMacros" />
+  <PropertyGroup>
+    <_ProjectFileVersion>10.0.30319.1</_ProjectFileVersion>
+    <OutDir>.\$(Platform)\$(Configuration)\</OutDir>
+    <IntDir>.\$(Platform)\$(Configuration)\</IntDir>
+    <!-- The ICU projects use "Win32" to mean "x86", so we need to special case it. -->
+    <OutDir Condition="'$(Platform)'=='Win32'">.\x86\$(Configuration)\</OutDir>
+    <IntDir Condition="'$(Platform)'=='Win32'">.\x86\$(Configuration)\</IntDir>
+    <!-- Disable Incremental Linking for Release builds as it prevents Link-time Code Generation -->
+    <LinkIncremental Condition="'$(Configuration)'=='Debug'">true</LinkIncremental>
+    <LinkIncremental Condition="'$(Configuration)'=='Release'">false</LinkIncremental>
+  </PropertyGroup>
+  <!-- Options that are common to *all* configurations -->
+  <ItemDefinitionGroup>
+    <Midl>
+      <TypeLibraryName>$(OutDir)/makeconv.tlb</TypeLibraryName>
+    </Midl>
+    <ClCompile>
+      <WarningLevel>Level3</WarningLevel>
+      <CompileAs>Default</CompileAs>
+      <DisableLanguageExtensions>false</DisableLanguageExtensions>
+      <AdditionalIncludeDirectories>..\..\..\include;..\..\common;..\toolutil;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
+      <PrecompiledHeaderOutputFile>$(OutDir)/makeconv.pch</PrecompiledHeaderOutputFile>
+      <AssemblerListingLocation>$(OutDir)/</AssemblerListingLocation>
+      <ObjectFileName>$(OutDir)/</ObjectFileName>
+      <ProgramDataBaseFileName>$(OutDir)/makeconv.pdb</ProgramDataBaseFileName>
+    </ClCompile>
+    <Link>
+      <SubSystem>Console</SubSystem>
+      <OutputFile>$(OutDir)/makeconv.exe</OutputFile>
+      <AdditionalLibraryDirectories>..\..\..\$(IcuLibOutputDir);%(AdditionalLibraryDirectories)</AdditionalLibraryDirectories>
+    </Link>
+    <CustomBuildStep>
+      <Command>copy "$(TargetPath)" ..\..\..\$(IcuBinOutputDir)</Command>
+      <Outputs>..\..\..\$(IcuBinOutputDir)\$(TargetFileName);%(Outputs)</Outputs>
+    </CustomBuildStep>
+  </ItemDefinitionGroup>
+  <!-- Options that are common to all 'Debug' project configurations -->
+  <ItemDefinitionGroup Condition="'$(Configuration)'=='Debug'">
+    <ClCompile>
+      <BrowseInformation>true</BrowseInformation>
+      <RuntimeLibrary>MultiThreadedDebugDLL</RuntimeLibrary>
+    </ClCompile>
+    <Link>
+      <AdditionalDependencies>icuucd.lib;icutud.lib;%(AdditionalDependencies)</AdditionalDependencies>
+    </Link>
+  </ItemDefinitionGroup>
+  <!-- Options that are common to all 'Release' project configurations -->
+  <ItemDefinitionGroup Condition="'$(Configuration)'=='Release'">
+    <ClCompile>
+      <RuntimeLibrary>MultiThreadedDLL</RuntimeLibrary>
+      <FunctionLevelLinking>true</FunctionLevelLinking>
+    </ClCompile>
+    <Link>
+      <AdditionalDependencies>icuuc.lib;icutu.lib;%(AdditionalDependencies)</AdditionalDependencies>
+    </Link>
+  </ItemDefinitionGroup>
+  <ItemGroup>
+    <ClCompile Include="gencnvex.c" />
+    <ClCompile Include="genmbcs.cpp" />
+    <ClCompile Include="makeconv.cpp" />
+    <ClCompile Include="ucnvstat.c" />
+  </ItemGroup>
+  <ItemGroup>
+    <ClInclude Include="genmbcs.h" />
+    <ClInclude Include="makeconv.h" />
+  </ItemGroup>
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
+  <ImportGroup Label="ExtensionTargets">
+  </ImportGroup>
+</Project>
\ No newline at end of file
diff --git a/intl/icu/source/tools/makeconv/makeconv.vcxproj.filters b/intl/icu/source/tools/makeconv/makeconv.vcxproj.filters
new file mode 100644
index 0000000000..b5232c7c7d
--- /dev/null
+++ b/intl/icu/source/tools/makeconv/makeconv.vcxproj.filters
@@ -0,0 +1,39 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <ItemGroup>
+    <Filter Include="Source Files">
+      <UniqueIdentifier>{de2dc8b2-bfcb-4516-bc0b-851f2bddd695}</UniqueIdentifier>
+      <Extensions>cpp;c;cxx;rc;def;r;odl;idl;hpj;bat</Extensions>
+    </Filter>
+    <Filter Include="Header Files">
+      <UniqueIdentifier>{0638fe1b-842e-4db0-b609-7da558bbad33}</UniqueIdentifier>
+      <Extensions>h;hpp;hxx;hm;inl</Extensions>
+    </Filter>
+    <Filter Include="Resource Files">
+      <UniqueIdentifier>{c192904c-2a84-40cd-8829-c5a00d5a15fb}</UniqueIdentifier>
+      <Extensions>ico;cur;bmp;dlg;rc2;rct;bin;rgs;gif;jpg;jpeg;jpe</Extensions>
+    </Filter>
+  </ItemGroup>
+  <ItemGroup>
+    <ClCompile Include="gencnvex.c">
+      <Filter>Source Files</Filter>
+    </ClCompile>
+    <ClCompile Include="genmbcs.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
+    <ClCompile Include="makeconv.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
+    <ClCompile Include="ucnvstat.c">
+      <Filter>Source Files</Filter>
+    </ClCompile>
+  </ItemGroup>
+  <ItemGroup>
+    <ClInclude Include="genmbcs.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+    <ClInclude Include="makeconv.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+  </ItemGroup>
+</Project>
\ No newline at end of file
diff --git a/intl/icu/source/tools/makeconv/sources.txt b/intl/icu/source/tools/makeconv/sources.txt
new file mode 100644
index 0000000000..4283ea9c49
--- /dev/null
+++ b/intl/icu/source/tools/makeconv/sources.txt
@@ -0,0 +1,4 @@
+gencnvex.c
+genmbcs.cpp
+makeconv.cpp
+ucnvstat.c
diff --git a/intl/icu/source/tools/makeconv/ucnvstat.c b/intl/icu/source/tools/makeconv/ucnvstat.c
new file mode 100644
index 0000000000..2140bc263f
--- /dev/null
+++ b/intl/icu/source/tools/makeconv/ucnvstat.c
@@ -0,0 +1,72 @@
+// © 2016 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
+/*
+ ******************************************************************************
+ *
+ *   Copyright (C) 1998-2006, International Business Machines
+ *   Corporation and others.  All Rights Reserved.
+ *
+ ******************************************************************************
+ *
+ *
+ *  ucnvstat.c:
+ *  UConverterStaticData prototypes for data based converters
+ */
+
+#include <stdbool.h>
+
+#include "unicode/utypes.h"
+#include "unicode/ucnv.h"
+#include "toolutil.h"
+#include "ucnv_bld.h"
+
+
+static const UConverterStaticData _SBCSStaticData={
+    sizeof(UConverterStaticData),
+    "SBCS",
+    0, UCNV_IBM, UCNV_SBCS, 1, 1,
+    { 0x1a, 0, 0, 0 }, 1, false, false,
+    0,
+    0,
+    { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 } /* reserved */
+};
+
+
+static const UConverterStaticData _DBCSStaticData={
+    sizeof(UConverterStaticData),
+    "DBCS",
+    0, UCNV_IBM, UCNV_DBCS, 2, 2,
+    { 0, 0, 0, 0 },0, false, false, /* subchar */
+    0,
+    0,
+    { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 } /* reserved */
+};
+
+static const UConverterStaticData _MBCSStaticData={
+    sizeof(UConverterStaticData),
+    "MBCS",
+    0, UCNV_IBM, UCNV_MBCS, 1, 1,
+    { 0x1a, 0, 0, 0 }, 1, false, false,
+    0,
+    0,
+    { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 } /* reserved */
+};
+
+static const UConverterStaticData _EBCDICStatefulStaticData={
+    sizeof(UConverterStaticData),
+    "EBCDICStateful",
+    0, UCNV_IBM, UCNV_EBCDIC_STATEFUL, 1, 1,
+    { 0, 0, 0, 0 },0, false, false,
+    0,
+    0,
+    { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 } /* reserved */
+};
+
+/* NULLs for algorithmic types, their tables live in ucnv_bld.c */
+const UConverterStaticData *ucnv_converterStaticData[UCNV_NUMBER_OF_SUPPORTED_CONVERTER_TYPES]={
+    &_SBCSStaticData, &_DBCSStaticData, &_MBCSStaticData, NULL/*Lat1*/,
+    NULL/*UTF8*/, NULL/*UTF16be*/, NULL/*UTF16LE*/, NULL/*UTF32be*/, NULL/*UTF32LE*/, &_EBCDICStatefulStaticData,
+    NULL/*ISO2022*/,
+    /* LMBCS */ NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL
+};
+