Adding upstream version 115.8.0esr.upstream/115.8.0esr

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

1 files changed, 1909 insertions, 0 deletions

diff --git a/intl/icu/source/i18n/dtitvfmt.cpp b/intl/icu/source/i18n/dtitvfmt.cpp
new file mode 100644
index 0000000000..6087014668
--- /dev/null
+++ b/intl/icu/source/i18n/dtitvfmt.cpp
@@ -0,0 +1,1909 @@
+// © 2016 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
+/*******************************************************************************
+* Copyright (C) 2008-2016, International Business Machines Corporation and
+* others. All Rights Reserved.
+*******************************************************************************
+*
+* File DTITVFMT.CPP
+*
+*******************************************************************************
+*/
+
+#include "utypeinfo.h"  // for 'typeid' to work
+
+#include "unicode/dtitvfmt.h"
+
+#if !UCONFIG_NO_FORMATTING
+
+//TODO: put in compilation
+//#define DTITVFMT_DEBUG 1
+
+#include "unicode/calendar.h"
+#include "unicode/dtptngen.h"
+#include "unicode/dtitvinf.h"
+#include "unicode/simpleformatter.h"
+#include "unicode/udisplaycontext.h"
+#include "cmemory.h"
+#include "cstring.h"
+#include "dtitv_impl.h"
+#include "mutex.h"
+#include "uresimp.h"
+#include "formattedval_impl.h"
+
+#ifdef DTITVFMT_DEBUG
+#include <iostream>
+#endif
+
+U_NAMESPACE_BEGIN
+
+
+
+#ifdef DTITVFMT_DEBUG
+#define PRINTMESG(msg) { std::cout << "(" << __FILE__ << ":" << __LINE__ << ") " << msg << "\n"; }
+#endif
+
+
+static const char16_t gDateFormatSkeleton[][11] = {
+//yMMMMEEEEd
+{LOW_Y, CAP_M, CAP_M, CAP_M, CAP_M, CAP_E, CAP_E, CAP_E, CAP_E, LOW_D, 0},
+//yMMMMd
+{LOW_Y, CAP_M, CAP_M, CAP_M, CAP_M, LOW_D, 0},
+//yMMMd
+{LOW_Y, CAP_M, CAP_M, CAP_M, LOW_D, 0},
+//yMd
+{LOW_Y, CAP_M, LOW_D, 0} };
+
+
+static const char gCalendarTag[] = "calendar";
+static const char gGregorianTag[] = "gregorian";
+static const char gDateTimePatternsTag[] = "DateTimePatterns";
+
+
+// latestFirst:
+static const char16_t gLaterFirstPrefix[] = {LOW_L, LOW_A, LOW_T, LOW_E, LOW_S,LOW_T, CAP_F, LOW_I, LOW_R, LOW_S, LOW_T, COLON};
+
+// earliestFirst:
+static const char16_t gEarlierFirstPrefix[] = {LOW_E, LOW_A, LOW_R, LOW_L, LOW_I, LOW_E, LOW_S, LOW_T, CAP_F, LOW_I, LOW_R, LOW_S, LOW_T, COLON};
+
+
+class FormattedDateIntervalData : public FormattedValueFieldPositionIteratorImpl {
+public:
+    FormattedDateIntervalData(UErrorCode& status) : FormattedValueFieldPositionIteratorImpl(5, status) {}
+    virtual ~FormattedDateIntervalData();
+};
+
+FormattedDateIntervalData::~FormattedDateIntervalData() = default;
+
+UPRV_FORMATTED_VALUE_SUBCLASS_AUTO_IMPL(FormattedDateInterval)
+
+
+UOBJECT_DEFINE_RTTI_IMPLEMENTATION(DateIntervalFormat)
+
+// Mutex, protects access to fDateFormat, fFromCalendar and fToCalendar.
+//        Needed because these data members are modified by const methods of DateIntervalFormat.
+
+static UMutex gFormatterMutex;
+
+DateIntervalFormat* U_EXPORT2
+DateIntervalFormat::createInstance(const UnicodeString& skeleton,
+                                   UErrorCode& status) {
+    return createInstance(skeleton, Locale::getDefault(), status);
+}
+
+
+DateIntervalFormat* U_EXPORT2
+DateIntervalFormat::createInstance(const UnicodeString& skeleton,
+                                   const Locale& locale,
+                                   UErrorCode& status) {
+#ifdef DTITVFMT_DEBUG
+    char result[1000];
+    char result_1[1000];
+    char mesg[2000];
+    skeleton.extract(0,  skeleton.length(), result, "UTF-8");
+    UnicodeString pat;
+    ((SimpleDateFormat*)dtfmt)->toPattern(pat);
+    pat.extract(0,  pat.length(), result_1, "UTF-8");
+    snprintf(mesg, sizeof(mesg), "skeleton: %s; pattern: %s\n", result, result_1);
+    PRINTMESG(mesg)
+#endif
+
+    DateIntervalInfo* dtitvinf = new DateIntervalInfo(locale, status);
+    if (dtitvinf == nullptr) {
+        status = U_MEMORY_ALLOCATION_ERROR;
+        return nullptr;
+    }
+    return create(locale, dtitvinf, &skeleton, status);
+}
+
+
+
+DateIntervalFormat* U_EXPORT2
+DateIntervalFormat::createInstance(const UnicodeString& skeleton,
+                                   const DateIntervalInfo& dtitvinf,
+                                   UErrorCode& status) {
+    return createInstance(skeleton, Locale::getDefault(), dtitvinf, status);
+}
+
+
+DateIntervalFormat* U_EXPORT2
+DateIntervalFormat::createInstance(const UnicodeString& skeleton,
+                                   const Locale& locale,
+                                   const DateIntervalInfo& dtitvinf,
+                                   UErrorCode& status) {
+    DateIntervalInfo* ptn = dtitvinf.clone();
+    return create(locale, ptn, &skeleton, status);
+}
+
+
+DateIntervalFormat::DateIntervalFormat()
+:   fInfo(nullptr),
+    fDateFormat(nullptr),
+    fFromCalendar(nullptr),
+    fToCalendar(nullptr),
+    fLocale(Locale::getRoot()),
+    fDatePattern(nullptr),
+    fTimePattern(nullptr),
+    fDateTimeFormat(nullptr),
+    fCapitalizationContext(UDISPCTX_CAPITALIZATION_NONE)
+{}
+
+
+DateIntervalFormat::DateIntervalFormat(const DateIntervalFormat& itvfmt)
+:   Format(itvfmt),
+    fInfo(nullptr),
+    fDateFormat(nullptr),
+    fFromCalendar(nullptr),
+    fToCalendar(nullptr),
+    fLocale(itvfmt.fLocale),
+    fDatePattern(nullptr),
+    fTimePattern(nullptr),
+    fDateTimeFormat(nullptr),
+    fCapitalizationContext(UDISPCTX_CAPITALIZATION_NONE) {
+    *this = itvfmt;
+}
+
+
+DateIntervalFormat&
+DateIntervalFormat::operator=(const DateIntervalFormat& itvfmt) {
+    if ( this != &itvfmt ) {
+        delete fDateFormat;
+        delete fInfo;
+        delete fFromCalendar;
+        delete fToCalendar;
+        delete fDatePattern;
+        delete fTimePattern;
+        delete fDateTimeFormat;
+        {
+            Mutex lock(&gFormatterMutex);
+            if ( itvfmt.fDateFormat ) {
+                fDateFormat = itvfmt.fDateFormat->clone();
+            } else {
+                fDateFormat = nullptr;
+            }
+            if ( itvfmt.fFromCalendar ) {
+                fFromCalendar = itvfmt.fFromCalendar->clone();
+            } else {
+                fFromCalendar = nullptr;
+            }
+            if ( itvfmt.fToCalendar ) {
+                fToCalendar = itvfmt.fToCalendar->clone();
+            } else {
+                fToCalendar = nullptr;
+            }
+        }
+        if ( itvfmt.fInfo ) {
+            fInfo = itvfmt.fInfo->clone();
+        } else {
+            fInfo = nullptr;
+        }
+        fSkeleton = itvfmt.fSkeleton;
+        int8_t i;
+        for ( i = 0; i< DateIntervalInfo::kIPI_MAX_INDEX; ++i ) {
+            fIntervalPatterns[i] = itvfmt.fIntervalPatterns[i];
+        }
+        fLocale = itvfmt.fLocale;
+        fDatePattern    = (itvfmt.fDatePattern)?    itvfmt.fDatePattern->clone(): nullptr;
+        fTimePattern    = (itvfmt.fTimePattern)?    itvfmt.fTimePattern->clone(): nullptr;
+        fDateTimeFormat = (itvfmt.fDateTimeFormat)? itvfmt.fDateTimeFormat->clone(): nullptr;
+        fCapitalizationContext = itvfmt.fCapitalizationContext;
+    }
+    return *this;
+}
+
+
+DateIntervalFormat::~DateIntervalFormat() {
+    delete fInfo;
+    delete fDateFormat;
+    delete fFromCalendar;
+    delete fToCalendar;
+    delete fDatePattern;
+    delete fTimePattern;
+    delete fDateTimeFormat;
+}
+
+
+DateIntervalFormat*
+DateIntervalFormat::clone() const {
+    return new DateIntervalFormat(*this);
+}
+
+
+bool
+DateIntervalFormat::operator==(const Format& other) const {
+    if (typeid(*this) != typeid(other)) {return false;}
+    const DateIntervalFormat* fmt = (DateIntervalFormat*)&other;
+    if (this == fmt) {return true;}
+    if (!Format::operator==(other)) {return false;}
+    if ((fInfo != fmt->fInfo) && (fInfo == nullptr || fmt->fInfo == nullptr)) {return false;}
+    if (fInfo && fmt->fInfo && (*fInfo != *fmt->fInfo )) {return false;}
+    {
+        Mutex lock(&gFormatterMutex);
+        if (fDateFormat != fmt->fDateFormat && (fDateFormat == nullptr || fmt->fDateFormat == nullptr)) {return false;}
+        if (fDateFormat && fmt->fDateFormat && (*fDateFormat != *fmt->fDateFormat)) {return false;}
+    }
+    // note: fFromCalendar and fToCalendar hold no persistent state, and therefore do not participate in operator ==.
+    //       fDateFormat has the primary calendar for the DateIntervalFormat.
+    if (fSkeleton != fmt->fSkeleton) {return false;}
+    if (fDatePattern != fmt->fDatePattern && (fDatePattern == nullptr || fmt->fDatePattern == nullptr)) {return false;}
+    if (fDatePattern && fmt->fDatePattern && (*fDatePattern != *fmt->fDatePattern)) {return false;}
+    if (fTimePattern != fmt->fTimePattern && (fTimePattern == nullptr || fmt->fTimePattern == nullptr)) {return false;}
+    if (fTimePattern && fmt->fTimePattern && (*fTimePattern != *fmt->fTimePattern)) {return false;}
+    if (fDateTimeFormat != fmt->fDateTimeFormat && (fDateTimeFormat == nullptr || fmt->fDateTimeFormat == nullptr)) {return false;}
+    if (fDateTimeFormat && fmt->fDateTimeFormat && (*fDateTimeFormat != *fmt->fDateTimeFormat)) {return false;}
+    if (fLocale != fmt->fLocale) {return false;}
+
+    for (int32_t i = 0; i< DateIntervalInfo::kIPI_MAX_INDEX; ++i ) {
+        if (fIntervalPatterns[i].firstPart != fmt->fIntervalPatterns[i].firstPart) {return false;}
+        if (fIntervalPatterns[i].secondPart != fmt->fIntervalPatterns[i].secondPart ) {return false;}
+        if (fIntervalPatterns[i].laterDateFirst != fmt->fIntervalPatterns[i].laterDateFirst) {return false;}
+    }
+    if (fCapitalizationContext != fmt->fCapitalizationContext) {return false;}
+    return true;
+}
+
+
+UnicodeString&
+DateIntervalFormat::format(const Formattable& obj,
+                           UnicodeString& appendTo,
+                           FieldPosition& fieldPosition,
+                           UErrorCode& status) const {
+    if ( U_FAILURE(status) ) {
+        return appendTo;
+    }
+
+    if ( obj.getType() == Formattable::kObject ) {
+        const UObject* formatObj = obj.getObject();
+        const DateInterval* interval = dynamic_cast<const DateInterval*>(formatObj);
+        if (interval != nullptr) {
+            return format(interval, appendTo, fieldPosition, status);
+        }
+    }
+    status = U_ILLEGAL_ARGUMENT_ERROR;
+    return appendTo;
+}
+
+
+UnicodeString&
+DateIntervalFormat::format(const DateInterval* dtInterval,
+                           UnicodeString& appendTo,
+                           FieldPosition& fieldPosition,
+                           UErrorCode& status) const {
+    if ( U_FAILURE(status) ) {
+        return appendTo;
+    }
+    if (fDateFormat == nullptr || fInfo == nullptr) {
+        status = U_INVALID_STATE_ERROR;
+        return appendTo;
+    }
+
+    FieldPositionOnlyHandler handler(fieldPosition);
+    handler.setAcceptFirstOnly(true);
+    int8_t ignore;
+
+    Mutex lock(&gFormatterMutex);
+    return formatIntervalImpl(*dtInterval, appendTo, ignore, handler, status);
+}
+
+
+FormattedDateInterval DateIntervalFormat::formatToValue(
+        const DateInterval& dtInterval,
+        UErrorCode& status) const {
+    if (U_FAILURE(status)) {
+        return FormattedDateInterval(status);
+    }
+    // LocalPointer only sets OOM status if U_SUCCESS is true.
+    LocalPointer<FormattedDateIntervalData> result(new FormattedDateIntervalData(status), status);
+    if (U_FAILURE(status)) {
+        return FormattedDateInterval(status);
+    }
+    UnicodeString string;
+    int8_t firstIndex;
+    auto handler = result->getHandler(status);
+    handler.setCategory(UFIELD_CATEGORY_DATE);
+    {
+        Mutex lock(&gFormatterMutex);
+        formatIntervalImpl(dtInterval, string, firstIndex, handler, status);
+    }
+    handler.getError(status);
+    result->appendString(string, status);
+    if (U_FAILURE(status)) {
+        return FormattedDateInterval(status);
+    }
+
+    // Compute the span fields and sort them into place:
+    if (firstIndex != -1) {
+        result->addOverlapSpans(UFIELD_CATEGORY_DATE_INTERVAL_SPAN, firstIndex, status);
+        if (U_FAILURE(status)) {
+            return FormattedDateInterval(status);
+        }
+        result->sort();
+    }
+
+    return FormattedDateInterval(result.orphan());
+}
+
+
+UnicodeString&
+DateIntervalFormat::format(Calendar& fromCalendar,
+                           Calendar& toCalendar,
+                           UnicodeString& appendTo,
+                           FieldPosition& pos,
+                           UErrorCode& status) const {
+    FieldPositionOnlyHandler handler(pos);
+    handler.setAcceptFirstOnly(true);
+    int8_t ignore;
+
+    Mutex lock(&gFormatterMutex);
+    return formatImpl(fromCalendar, toCalendar, appendTo, ignore, handler, status);
+}
+
+
+FormattedDateInterval DateIntervalFormat::formatToValue(
+        Calendar& fromCalendar,
+        Calendar& toCalendar,
+        UErrorCode& status) const {
+    if (U_FAILURE(status)) {
+        return FormattedDateInterval(status);
+    }
+    // LocalPointer only sets OOM status if U_SUCCESS is true.
+    LocalPointer<FormattedDateIntervalData> result(new FormattedDateIntervalData(status), status);
+    if (U_FAILURE(status)) {
+        return FormattedDateInterval(status);
+    }
+    UnicodeString string;
+    int8_t firstIndex;
+    auto handler = result->getHandler(status);
+    handler.setCategory(UFIELD_CATEGORY_DATE);
+    {
+        Mutex lock(&gFormatterMutex);
+        formatImpl(fromCalendar, toCalendar, string, firstIndex, handler, status);
+    }
+    handler.getError(status);
+    result->appendString(string, status);
+    if (U_FAILURE(status)) {
+        return FormattedDateInterval(status);
+    }
+
+    // Compute the span fields and sort them into place:
+    if (firstIndex != -1) {
+        result->addOverlapSpans(UFIELD_CATEGORY_DATE_INTERVAL_SPAN, firstIndex, status);
+        result->sort();
+    }
+
+    return FormattedDateInterval(result.orphan());
+}
+
+
+UnicodeString& DateIntervalFormat::formatIntervalImpl(
+        const DateInterval& dtInterval,
+        UnicodeString& appendTo,
+        int8_t& firstIndex,
+        FieldPositionHandler& fphandler,
+        UErrorCode& status) const {
+    if (U_FAILURE(status)) {
+        return appendTo;
+    }
+    if (fFromCalendar == nullptr || fToCalendar == nullptr) {
+        status = U_INVALID_STATE_ERROR;
+        return appendTo;
+    }
+    fFromCalendar->setTime(dtInterval.getFromDate(), status);
+    fToCalendar->setTime(dtInterval.getToDate(), status);
+    return formatImpl(*fFromCalendar, *fToCalendar, appendTo, firstIndex, fphandler, status);
+}
+
+
+// The following is only called from within the gFormatterMutex lock
+UnicodeString&
+DateIntervalFormat::formatImpl(Calendar& fromCalendar,
+                           Calendar& toCalendar,
+                           UnicodeString& appendTo,
+                           int8_t& firstIndex,
+                           FieldPositionHandler& fphandler,
+                           UErrorCode& status) const {
+    if ( U_FAILURE(status) ) {
+        return appendTo;
+    }
+
+    // Initialize firstIndex to -1 (single date, no range)
+    firstIndex = -1;
+
+    // not support different calendar types and time zones
+    //if ( fromCalendar.getType() != toCalendar.getType() ) {
+    if ( !fromCalendar.isEquivalentTo(toCalendar) ) {
+        status = U_ILLEGAL_ARGUMENT_ERROR;
+        return appendTo;
+    }
+
+    // First, find the largest different calendar field.
+    UCalendarDateFields field = UCAL_FIELD_COUNT;
+
+    if ( fromCalendar.get(UCAL_ERA,status) != toCalendar.get(UCAL_ERA,status)) {
+        field = UCAL_ERA;
+    } else if ( fromCalendar.get(UCAL_YEAR, status) !=
+                toCalendar.get(UCAL_YEAR, status) ) {
+        field = UCAL_YEAR;
+    } else if ( fromCalendar.get(UCAL_MONTH, status) !=
+                toCalendar.get(UCAL_MONTH, status) ) {
+        field = UCAL_MONTH;
+    } else if ( fromCalendar.get(UCAL_DATE, status) !=
+                toCalendar.get(UCAL_DATE, status) ) {
+        field = UCAL_DATE;
+    } else if ( fromCalendar.get(UCAL_AM_PM, status) !=
+                toCalendar.get(UCAL_AM_PM, status) ) {
+        field = UCAL_AM_PM;
+    } else if ( fromCalendar.get(UCAL_HOUR, status) !=
+                toCalendar.get(UCAL_HOUR, status) ) {
+        field = UCAL_HOUR;
+    } else if ( fromCalendar.get(UCAL_MINUTE, status) !=
+                toCalendar.get(UCAL_MINUTE, status) ) {
+        field = UCAL_MINUTE;
+    } else if ( fromCalendar.get(UCAL_SECOND, status) !=
+                toCalendar.get(UCAL_SECOND, status) ) {
+        field = UCAL_SECOND;
+    } else if ( fromCalendar.get(UCAL_MILLISECOND, status) !=
+                toCalendar.get(UCAL_MILLISECOND, status) ) {
+        field = UCAL_MILLISECOND;
+    }
+
+    if ( U_FAILURE(status) ) {
+        return appendTo;
+    }
+    UErrorCode tempStatus = U_ZERO_ERROR; // for setContext, ignored
+    // Set up fDateFormat to handle the first or only part of the interval
+    // (override later for any second part). Inside lock, OK to modify fDateFormat.
+    fDateFormat->setContext(fCapitalizationContext, tempStatus);
+
+    if ( field == UCAL_FIELD_COUNT ) {
+        /* ignore the millisecond etc. small fields' difference.
+         * use single date when all the above are the same.
+         */
+        return fDateFormat->_format(fromCalendar, appendTo, fphandler, status);
+    }
+    UBool fromToOnSameDay = (field==UCAL_AM_PM || field==UCAL_HOUR || field==UCAL_MINUTE || field==UCAL_SECOND || field==UCAL_MILLISECOND);
+
+    // following call should not set wrong status,
+    // all the pass-in fields are valid till here
+    int32_t itvPtnIndex = DateIntervalInfo::calendarFieldToIntervalIndex(field,
+                                                                        status);
+    const PatternInfo& intervalPattern = fIntervalPatterns[itvPtnIndex];
+
+    if ( intervalPattern.firstPart.isEmpty() &&
+         intervalPattern.secondPart.isEmpty() ) {
+        if ( fDateFormat->isFieldUnitIgnored(field) ) {
+            /* the largest different calendar field is small than
+             * the smallest calendar field in pattern,
+             * return single date format.
+             */
+            return fDateFormat->_format(fromCalendar, appendTo, fphandler, status);
+        }
+        return fallbackFormat(fromCalendar, toCalendar, fromToOnSameDay, appendTo, firstIndex, fphandler, status);
+    }
+    // If the first part in interval pattern is empty,
+    // the 2nd part of it saves the full-pattern used in fall-back.
+    // For a 'real' interval pattern, the first part will never be empty.
+    if ( intervalPattern.firstPart.isEmpty() ) {
+        // fall back
+        UnicodeString originalPattern;
+        fDateFormat->toPattern(originalPattern);
+        fDateFormat->applyPattern(intervalPattern.secondPart);
+        appendTo = fallbackFormat(fromCalendar, toCalendar, fromToOnSameDay, appendTo, firstIndex, fphandler, status);
+        fDateFormat->applyPattern(originalPattern);
+        return appendTo;
+    }
+    Calendar* firstCal;
+    Calendar* secondCal;
+    if ( intervalPattern.laterDateFirst ) {
+        firstCal = &toCalendar;
+        secondCal = &fromCalendar;
+        firstIndex = 1;
+    } else {
+        firstCal = &fromCalendar;
+        secondCal = &toCalendar;
+        firstIndex = 0;
+    }
+    // break the interval pattern into 2 parts,
+    // first part should not be empty,
+    UnicodeString originalPattern;
+    fDateFormat->toPattern(originalPattern);
+    fDateFormat->applyPattern(intervalPattern.firstPart);
+    fDateFormat->_format(*firstCal, appendTo, fphandler, status);
+
+    if ( !intervalPattern.secondPart.isEmpty() ) {
+        fDateFormat->applyPattern(intervalPattern.secondPart);
+        // No capitalization for second part of interval
+        tempStatus = U_ZERO_ERROR;
+        fDateFormat->setContext(UDISPCTX_CAPITALIZATION_NONE, tempStatus);
+        fDateFormat->_format(*secondCal, appendTo, fphandler, status);
+    }
+    fDateFormat->applyPattern(originalPattern);
+    return appendTo;
+}
+
+
+
+void
+DateIntervalFormat::parseObject(const UnicodeString& /* source */,
+                                Formattable& /* result */,
+                                ParsePosition& /* parse_pos */) const {
+    // parseObject(const UnicodeString&, Formattable&, UErrorCode&) const
+    // will set status as U_INVALID_FORMAT_ERROR if
+    // parse_pos is still 0
+}
+
+
+
+
+const DateIntervalInfo*
+DateIntervalFormat::getDateIntervalInfo() const {
+    return fInfo;
+}
+
+
+void
+DateIntervalFormat::setDateIntervalInfo(const DateIntervalInfo& newItvPattern,
+                                        UErrorCode& status) {
+    delete fInfo;
+    fInfo = new DateIntervalInfo(newItvPattern);
+    if (fInfo == nullptr) {
+        status = U_MEMORY_ALLOCATION_ERROR;
+    }
+
+    // Delete patterns that get reset by initializePattern
+    delete fDatePattern;
+    fDatePattern = nullptr;
+    delete fTimePattern;
+    fTimePattern = nullptr;
+    delete fDateTimeFormat;
+    fDateTimeFormat = nullptr;
+
+    if (fDateFormat) {
+        initializePattern(status);
+    }
+}
+
+
+
+const DateFormat*
+DateIntervalFormat::getDateFormat() const {
+    return fDateFormat;
+}
+
+
+void
+DateIntervalFormat::adoptTimeZone(TimeZone* zone)
+{
+    if (fDateFormat != nullptr) {
+        fDateFormat->adoptTimeZone(zone);
+    }
+    // The fDateFormat has the primary calendar for the DateIntervalFormat and has
+    // ownership of any adopted TimeZone; fFromCalendar and fToCalendar are internal
+    // work clones of that calendar (and should not also be given ownership of the
+    // adopted TimeZone).
+    if (fFromCalendar) {
+        fFromCalendar->setTimeZone(*zone);
+    }
+    if (fToCalendar) {
+        fToCalendar->setTimeZone(*zone);
+    }
+}
+
+void
+DateIntervalFormat::setTimeZone(const TimeZone& zone)
+{
+    if (fDateFormat != nullptr) {
+        fDateFormat->setTimeZone(zone);
+    }
+    // The fDateFormat has the primary calendar for the DateIntervalFormat;
+    // fFromCalendar and fToCalendar are internal work clones of that calendar.
+    if (fFromCalendar) {
+        fFromCalendar->setTimeZone(zone);
+    }
+    if (fToCalendar) {
+        fToCalendar->setTimeZone(zone);
+    }
+}
+
+const TimeZone&
+DateIntervalFormat::getTimeZone() const
+{
+    if (fDateFormat != nullptr) {
+        Mutex lock(&gFormatterMutex);
+        return fDateFormat->getTimeZone();
+    }
+    // If fDateFormat is nullptr (unexpected), create default timezone.
+    return *(TimeZone::createDefault());
+}
+
+void
+DateIntervalFormat::setContext(UDisplayContext value, UErrorCode& status)
+{
+    if (U_FAILURE(status))
+        return;
+    if ( (UDisplayContextType)((uint32_t)value >> 8) == UDISPCTX_TYPE_CAPITALIZATION ) {
+        fCapitalizationContext = value;
+    } else {
+        status = U_ILLEGAL_ARGUMENT_ERROR;
+    }
+}
+
+UDisplayContext
+DateIntervalFormat::getContext(UDisplayContextType type, UErrorCode& status) const
+{
+    if (U_FAILURE(status))
+        return (UDisplayContext)0;
+    if (type != UDISPCTX_TYPE_CAPITALIZATION) {
+        status = U_ILLEGAL_ARGUMENT_ERROR;
+        return (UDisplayContext)0;
+    }
+    return fCapitalizationContext;
+}
+
+DateIntervalFormat::DateIntervalFormat(const Locale& locale,
+                                       DateIntervalInfo* dtItvInfo,
+                                       const UnicodeString* skeleton,
+                                       UErrorCode& status)
+:   fInfo(nullptr),
+    fDateFormat(nullptr),
+    fFromCalendar(nullptr),
+    fToCalendar(nullptr),
+    fLocale(locale),
+    fDatePattern(nullptr),
+    fTimePattern(nullptr),
+    fDateTimeFormat(nullptr),
+    fCapitalizationContext(UDISPCTX_CAPITALIZATION_NONE)
+{
+    LocalPointer<DateIntervalInfo> info(dtItvInfo, status);
+    LocalPointer<SimpleDateFormat> dtfmt(static_cast<SimpleDateFormat *>(
+            DateFormat::createInstanceForSkeleton(*skeleton, locale, status)), status);
+    if (U_FAILURE(status)) {
+        return;
+    }
+
+    if ( skeleton ) {
+        fSkeleton = *skeleton;
+    }
+    fInfo = info.orphan();
+    fDateFormat = dtfmt.orphan();
+    if ( fDateFormat->getCalendar() ) {
+        fFromCalendar = fDateFormat->getCalendar()->clone();
+        fToCalendar = fDateFormat->getCalendar()->clone();
+    }
+    initializePattern(status);
+}
+
+DateIntervalFormat* U_EXPORT2
+DateIntervalFormat::create(const Locale& locale,
+                           DateIntervalInfo* dtitvinf,
+                           const UnicodeString* skeleton,
+                           UErrorCode& status) {
+    DateIntervalFormat* f = new DateIntervalFormat(locale, dtitvinf,
+                                                   skeleton, status);
+    if ( f == nullptr ) {
+        status = U_MEMORY_ALLOCATION_ERROR;
+        delete dtitvinf;
+    } else if ( U_FAILURE(status) ) {
+        // safe to delete f, although nothing actually is saved
+        delete f;
+        f = 0;
+    }
+    return f;
+}
+
+
+
+/**
+ * Initialize interval patterns locale to this formatter
+ *
+ * This code is a bit complicated since
+ * 1. the interval patterns saved in resource bundle files are interval
+ *    patterns based on date or time only.
+ *    It does not have interval patterns based on both date and time.
+ *    Interval patterns on both date and time are algorithm generated.
+ *
+ *    For example, it has interval patterns on skeleton "dMy" and "hm",
+ *    but it does not have interval patterns on skeleton "dMyhm".
+ *
+ *    The rule to genearte interval patterns for both date and time skeleton are
+ *    1) when the year, month, or day differs, concatenate the two original
+ *    expressions with a separator between,
+ *    For example, interval pattern from "Jan 10, 2007 10:10 am"
+ *    to "Jan 11, 2007 10:10am" is
+ *    "Jan 10, 2007 10:10 am - Jan 11, 2007 10:10am"
+ *
+ *    2) otherwise, present the date followed by the range expression
+ *    for the time.
+ *    For example, interval pattern from "Jan 10, 2007 10:10 am"
+ *    to "Jan 10, 2007 11:10am" is
+ *    "Jan 10, 2007 10:10 am - 11:10am"
+ *
+ * 2. even a pattern does not request a certion calendar field,
+ *    the interval pattern needs to include such field if such fields are
+ *    different between 2 dates.
+ *    For example, a pattern/skeleton is "hm", but the interval pattern
+ *    includes year, month, and date when year, month, and date differs.
+ *
+ * @param status          output param set to success/failure code on exit
+ * @stable ICU 4.0
+ */
+void
+DateIntervalFormat::initializePattern(UErrorCode& status) {
+    if ( U_FAILURE(status) ) {
+        return;
+    }
+    const Locale& locale = fDateFormat->getSmpFmtLocale();
+    if ( fSkeleton.isEmpty() ) {
+        UnicodeString fullPattern;
+        fDateFormat->toPattern(fullPattern);
+#ifdef DTITVFMT_DEBUG
+    char result[1000];
+    char result_1[1000];
+    char mesg[2000];
+    fSkeleton.extract(0,  fSkeleton.length(), result, "UTF-8");
+    snprintf(mesg, sizeof(mesg), "in getBestSkeleton: fSkeleton: %s; \n", result);
+    PRINTMESG(mesg)
+#endif
+        // fSkeleton is already set by createDateIntervalInstance()
+        // or by createInstance(UnicodeString skeleton, .... )
+        fSkeleton = DateTimePatternGenerator::staticGetSkeleton(
+                fullPattern, status);
+        if ( U_FAILURE(status) ) {
+            return;
+        }
+    }
+
+    // initialize the fIntervalPattern ordering
+    int8_t i;
+    for ( i = 0; i < DateIntervalInfo::kIPI_MAX_INDEX; ++i ) {
+        fIntervalPatterns[i].laterDateFirst = fInfo->getDefaultOrder();
+    }
+
+    /* Check whether the skeleton is a combination of date and time.
+     * For the complication reason 1 explained above.
+     */
+    UnicodeString dateSkeleton;
+    UnicodeString timeSkeleton;
+    UnicodeString normalizedTimeSkeleton;
+    UnicodeString normalizedDateSkeleton;
+
+
+    /* the difference between time skeleton and normalizedTimeSkeleton are:
+     * 1. (Formerly, normalized time skeleton folded 'H' to 'h'; no longer true)
+     * 2. (Formerly, 'a' was omitted in normalized time skeleton; this is now handled elsewhere)
+     * 3. there is only one appearance for 'h' or 'H', 'm','v', 'z' in normalized
+     *    time skeleton
+     *
+     * The difference between date skeleton and normalizedDateSkeleton are:
+     * 1. both 'y' and 'd' appear only once in normalizeDateSkeleton
+     * 2. 'E' and 'EE' are normalized into 'EEE'
+     * 3. 'MM' is normalized into 'M'
+     */
+    UnicodeString convertedSkeleton = normalizeHourMetacharacters(fSkeleton);
+    getDateTimeSkeleton(convertedSkeleton, dateSkeleton, normalizedDateSkeleton,
+                        timeSkeleton, normalizedTimeSkeleton);
+
+#ifdef DTITVFMT_DEBUG
+    char result[1000];
+    char result_1[1000];
+    char mesg[2000];
+    fSkeleton.extract(0,  fSkeleton.length(), result, "UTF-8");
+    snprintf(mesg, sizeof(mesg), "in getBestSkeleton: fSkeleton: %s; \n", result);
+    PRINTMESG(mesg)
+#endif
+
+    // move this up here since we need it for fallbacks
+    if ( timeSkeleton.length() > 0 && dateSkeleton.length() > 0 ) {
+        // Need the Date/Time pattern for concatenation of the date
+        // with the time interval.
+        // The date/time pattern ( such as {0} {1} ) is saved in
+        // calendar, that is why need to get the CalendarData here.
+        LocalUResourceBundlePointer dateTimePatternsRes(ures_open(nullptr, locale.getBaseName(), &status));
+        ures_getByKey(dateTimePatternsRes.getAlias(), gCalendarTag,
+                      dateTimePatternsRes.getAlias(), &status);
+        ures_getByKeyWithFallback(dateTimePatternsRes.getAlias(), gGregorianTag,
+                                  dateTimePatternsRes.getAlias(), &status);
+        ures_getByKeyWithFallback(dateTimePatternsRes.getAlias(), gDateTimePatternsTag,
+                                  dateTimePatternsRes.getAlias(), &status);
+
+        int32_t dateTimeFormatLength;
+        const char16_t* dateTimeFormat = ures_getStringByIndex(
+                                            dateTimePatternsRes.getAlias(),
+                                            (int32_t)DateFormat::kDateTime,
+                                            &dateTimeFormatLength, &status);
+        if ( U_SUCCESS(status) && dateTimeFormatLength >= 3 ) {
+            fDateTimeFormat = new UnicodeString(dateTimeFormat, dateTimeFormatLength);
+            if (fDateTimeFormat == nullptr) {
+                status = U_MEMORY_ALLOCATION_ERROR;
+                return;
+            }
+        }
+    }
+
+    UBool found = setSeparateDateTimePtn(normalizedDateSkeleton,
+                                         normalizedTimeSkeleton);
+
+    // for skeletons with seconds, found is false and we enter this block
+    if ( found == false ) {
+        // use fallback
+        // TODO: if user asks "m"(minute), but "d"(day) differ
+        if ( timeSkeleton.length() != 0 ) {
+            if ( dateSkeleton.length() == 0 ) {
+                // prefix with yMd
+                timeSkeleton.insert(0, gDateFormatSkeleton[DateFormat::kShort], -1);
+                UnicodeString pattern = DateFormat::getBestPattern(
+                        locale, timeSkeleton, status);
+                if ( U_FAILURE(status) ) {
+                    return;
+                }
+                // for fall back interval patterns,
+                // the first part of the pattern is empty,
+                // the second part of the pattern is the full-pattern
+                // should be used in fall-back.
+                setPatternInfo(UCAL_DATE, nullptr, &pattern, fInfo->getDefaultOrder());
+                setPatternInfo(UCAL_MONTH, nullptr, &pattern, fInfo->getDefaultOrder());
+                setPatternInfo(UCAL_YEAR, nullptr, &pattern, fInfo->getDefaultOrder());
+
+                timeSkeleton.insert(0, CAP_G);
+                pattern = DateFormat::getBestPattern(
+                        locale, timeSkeleton, status);
+                if ( U_FAILURE(status) ) {
+                    return;
+                }
+                setPatternInfo(UCAL_ERA, nullptr, &pattern, fInfo->getDefaultOrder());
+            } else {
+                // TODO: fall back
+            }
+        } else {
+            // TODO: fall back
+        }
+        return;
+    } // end of skeleton not found
+    // interval patterns for skeleton are found in resource
+    if ( timeSkeleton.length() == 0 ) {
+        // done
+    } else if ( dateSkeleton.length() == 0 ) {
+        // prefix with yMd
+        timeSkeleton.insert(0, gDateFormatSkeleton[DateFormat::kShort], -1);
+        UnicodeString pattern = DateFormat::getBestPattern(
+                locale, timeSkeleton, status);
+        if ( U_FAILURE(status) ) {
+            return;
+        }
+        // for fall back interval patterns,
+        // the first part of the pattern is empty,
+        // the second part of the pattern is the full-pattern
+        // should be used in fall-back.
+        setPatternInfo(UCAL_DATE, nullptr, &pattern, fInfo->getDefaultOrder());
+        setPatternInfo(UCAL_MONTH, nullptr, &pattern, fInfo->getDefaultOrder());
+        setPatternInfo(UCAL_YEAR, nullptr, &pattern, fInfo->getDefaultOrder());
+
+        timeSkeleton.insert(0, CAP_G);
+        pattern = DateFormat::getBestPattern(
+                locale, timeSkeleton, status);
+        if ( U_FAILURE(status) ) {
+            return;
+        }
+        setPatternInfo(UCAL_ERA, nullptr, &pattern, fInfo->getDefaultOrder());
+    } else {
+        /* if both present,
+         * 1) when the era, year, month, or day differs,
+         * concatenate the two original expressions with a separator between,
+         * 2) otherwise, present the date followed by the
+         * range expression for the time.
+         */
+        /*
+         * 1) when the era, year, month, or day differs,
+         * concatenate the two original expressions with a separator between,
+         */
+        // if field exists, use fall back
+        UnicodeString skeleton = fSkeleton;
+        if ( !fieldExistsInSkeleton(UCAL_DATE, dateSkeleton) ) {
+            // prefix skeleton with 'd'
+            skeleton.insert(0, LOW_D);
+            setFallbackPattern(UCAL_DATE, skeleton, status);
+        }
+        if ( !fieldExistsInSkeleton(UCAL_MONTH, dateSkeleton) ) {
+            // then prefix skeleton with 'M'
+            skeleton.insert(0, CAP_M);
+            setFallbackPattern(UCAL_MONTH, skeleton, status);
+        }
+        if ( !fieldExistsInSkeleton(UCAL_YEAR, dateSkeleton) ) {
+            // then prefix skeleton with 'y'
+            skeleton.insert(0, LOW_Y);
+            setFallbackPattern(UCAL_YEAR, skeleton, status);
+        }
+        if ( !fieldExistsInSkeleton(UCAL_ERA, dateSkeleton) ) {
+            // then prefix skeleton with 'G'
+            skeleton.insert(0, CAP_G);
+            setFallbackPattern(UCAL_ERA, skeleton, status);
+        }
+
+        /*
+         * 2) otherwise, present the date followed by the
+         * range expression for the time.
+         */
+
+        if ( fDateTimeFormat == nullptr ) {
+            // earlier failure getting dateTimeFormat
+            return;
+        }
+
+        UnicodeString datePattern = DateFormat::getBestPattern(
+                locale, dateSkeleton, status);
+
+        concatSingleDate2TimeInterval(*fDateTimeFormat, datePattern, UCAL_AM_PM, status);
+        concatSingleDate2TimeInterval(*fDateTimeFormat, datePattern, UCAL_HOUR, status);
+        concatSingleDate2TimeInterval(*fDateTimeFormat, datePattern, UCAL_MINUTE, status);
+    }
+}
+
+
+
+UnicodeString
+DateIntervalFormat::normalizeHourMetacharacters(const UnicodeString& skeleton) const {
+    UnicodeString result = skeleton;
+    
+    char16_t hourMetachar = u'\0';
+    char16_t dayPeriodChar = u'\0';
+    int32_t hourFieldStart = 0;
+    int32_t hourFieldLength = 0;
+    int32_t dayPeriodStart = 0;
+    int32_t dayPeriodLength = 0;
+    for (int32_t i = 0; i < result.length(); i++) {
+        char16_t c = result[i];
+        if (c == LOW_J || c == CAP_J || c == CAP_C || c == LOW_H || c == CAP_H || c == LOW_K || c == CAP_K) {
+            if (hourMetachar == u'\0') {
+                hourMetachar = c;
+                hourFieldStart = i;
+            }
+            ++hourFieldLength;
+        } else if (c == LOW_A || c == LOW_B || c == CAP_B) {
+            if (dayPeriodChar == u'\0') {
+                dayPeriodChar = c;
+                dayPeriodStart = i;
+            }
+            ++dayPeriodLength;
+        } else {
+            if (hourMetachar != u'\0' && dayPeriodChar != u'\0') {
+                break;
+            }
+        }
+    }
+    
+    if (hourMetachar != u'\0') {
+        UErrorCode err = U_ZERO_ERROR;
+        char16_t hourChar = CAP_H;
+        UnicodeString convertedPattern = DateFormat::getBestPattern(fLocale, UnicodeString(hourMetachar), err);
+
+        if (U_SUCCESS(err)) {
+            // strip literal text from the pattern (so literal characters don't get mistaken for pattern
+            // characters-- such as the 'h' in 'Uhr' in Germam)
+            int32_t firstQuotePos;
+            while ((firstQuotePos = convertedPattern.indexOf(u'\'')) != -1) {
+                int32_t secondQuotePos = convertedPattern.indexOf(u'\'', firstQuotePos + 1);
+                if (secondQuotePos == -1) {
+                    secondQuotePos = firstQuotePos;
+                }
+                convertedPattern.replace(firstQuotePos, (secondQuotePos - firstQuotePos) + 1, UnicodeString());
+            }
+        
+            if (convertedPattern.indexOf(LOW_H) != -1) {
+                hourChar = LOW_H;
+            } else if (convertedPattern.indexOf(CAP_K) != -1) {
+                hourChar = CAP_K;
+            } else if (convertedPattern.indexOf(LOW_K) != -1) {
+                hourChar = LOW_K;
+            }
+            
+            if (convertedPattern.indexOf(LOW_B) != -1) {
+                dayPeriodChar = LOW_B;
+            } else if (convertedPattern.indexOf(CAP_B) != -1) {
+                dayPeriodChar = CAP_B;
+            } else if (dayPeriodChar == u'\0') {
+                dayPeriodChar = LOW_A;
+            }
+        }
+        
+        UnicodeString hourAndDayPeriod(hourChar);
+        if (hourChar != CAP_H && hourChar != LOW_K) {
+            int32_t newDayPeriodLength = 0;
+            if (dayPeriodLength >= 5 || hourFieldLength >= 5) {
+                newDayPeriodLength = 5;
+            } else if (dayPeriodLength >= 3 || hourFieldLength >= 3) {
+                newDayPeriodLength = 3;
+            } else {
+                newDayPeriodLength = 1;
+            }
+            for (int32_t i = 0; i < newDayPeriodLength; i++) {
+                hourAndDayPeriod.append(dayPeriodChar);
+            }
+        }
+        result.replace(hourFieldStart, hourFieldLength, hourAndDayPeriod);
+        if (dayPeriodStart > hourFieldStart) {
+            // before deleting the original day period field, adjust its position in case
+            // we just changed the size of the hour field (and new day period field)
+            dayPeriodStart += hourAndDayPeriod.length() - hourFieldLength;
+        }
+        result.remove(dayPeriodStart, dayPeriodLength);
+    }
+    return result;
+}
+
+
+void  U_EXPORT2
+DateIntervalFormat::getDateTimeSkeleton(const UnicodeString& skeleton,
+                                        UnicodeString& dateSkeleton,
+                                        UnicodeString& normalizedDateSkeleton,
+                                        UnicodeString& timeSkeleton,
+                                        UnicodeString& normalizedTimeSkeleton) {
+    // dateSkeleton follows the sequence of y*M*E*d*
+    // timeSkeleton follows the sequence of hm*[v|z]?
+    int32_t ECount = 0;
+    int32_t dCount = 0;
+    int32_t MCount = 0;
+    int32_t yCount = 0;
+    int32_t mCount = 0;
+    int32_t vCount = 0;
+    int32_t zCount = 0;
+    char16_t hourChar = u'\0';
+    int32_t i;
+
+    for (i = 0; i < skeleton.length(); ++i) {
+        char16_t ch = skeleton[i];
+        switch ( ch ) {
+          case CAP_E:
+            dateSkeleton.append(ch);
+            ++ECount;
+            break;
+          case LOW_D:
+            dateSkeleton.append(ch);
+            ++dCount;
+            break;
+          case CAP_M:
+            dateSkeleton.append(ch);
+            ++MCount;
+            break;
+          case LOW_Y:
+            dateSkeleton.append(ch);
+            ++yCount;
+            break;
+          case CAP_G:
+          case CAP_Y:
+          case LOW_U:
+          case CAP_Q:
+          case LOW_Q:
+          case CAP_L:
+          case LOW_L:
+          case CAP_W:
+          case LOW_W:
+          case CAP_D:
+          case CAP_F:
+          case LOW_G:
+          case LOW_E:
+          case LOW_C:
+          case CAP_U:
+          case LOW_R:
+            normalizedDateSkeleton.append(ch);
+            dateSkeleton.append(ch);
+            break;
+          case LOW_H:
+          case CAP_H:
+          case LOW_K:
+          case CAP_K:
+            timeSkeleton.append(ch);
+            if (hourChar == u'\0') {
+                hourChar = ch;
+            }
+            break;
+          case LOW_M:
+            timeSkeleton.append(ch);
+            ++mCount;
+            break;
+          case LOW_Z:
+            ++zCount;
+            timeSkeleton.append(ch);
+            break;
+          case LOW_V:
+            ++vCount;
+            timeSkeleton.append(ch);
+            break;
+          case LOW_A:
+          case CAP_V:
+          case CAP_Z:
+          case LOW_J:
+          case LOW_S:
+          case CAP_S:
+          case CAP_A:
+          case LOW_B:
+          case CAP_B:
+            timeSkeleton.append(ch);
+            normalizedTimeSkeleton.append(ch);
+            break;
+        }
+    }
+
+    /* generate normalized form for date*/
+    if ( yCount != 0 ) {
+        for (i = 0; i < yCount; ++i) {
+            normalizedDateSkeleton.append(LOW_Y);
+        }
+    }
+    if ( MCount != 0 ) {
+        if ( MCount < 3 ) {
+            normalizedDateSkeleton.append(CAP_M);
+        } else {
+            for ( int32_t j = 0; j < MCount && j < MAX_M_COUNT; ++j) {
+                 normalizedDateSkeleton.append(CAP_M);
+            }
+        }
+    }
+    if ( ECount != 0 ) {
+        if ( ECount <= 3 ) {
+            normalizedDateSkeleton.append(CAP_E);
+        } else {
+            for ( int32_t j = 0; j < ECount && j < MAX_E_COUNT; ++j ) {
+                 normalizedDateSkeleton.append(CAP_E);
+            }
+        }
+    }
+    if ( dCount != 0 ) {
+        normalizedDateSkeleton.append(LOW_D);
+    }
+
+    /* generate normalized form for time */
+    if ( hourChar != u'\0' ) {
+        normalizedTimeSkeleton.append(hourChar);
+    }
+    if ( mCount != 0 ) {
+        normalizedTimeSkeleton.append(LOW_M);
+    }
+    if ( zCount != 0 ) {
+        normalizedTimeSkeleton.append(LOW_Z);
+    }
+    if ( vCount != 0 ) {
+        normalizedTimeSkeleton.append(LOW_V);
+    }
+}
+
+
+/**
+ * Generate date or time interval pattern from resource,
+ * and set them into the interval pattern locale to this formatter.
+ *
+ * It needs to handle the following:
+ * 1. need to adjust field width.
+ *    For example, the interval patterns saved in DateIntervalInfo
+ *    includes "dMMMy", but not "dMMMMy".
+ *    Need to get interval patterns for dMMMMy from dMMMy.
+ *    Another example, the interval patterns saved in DateIntervalInfo
+ *    includes "hmv", but not "hmz".
+ *    Need to get interval patterns for "hmz' from 'hmv'
+ *
+ * 2. there might be no pattern for 'y' differ for skeleton "Md",
+ *    in order to get interval patterns for 'y' differ,
+ *    need to look for it from skeleton 'yMd'
+ *
+ * @param dateSkeleton   normalized date skeleton
+ * @param timeSkeleton   normalized time skeleton
+ * @return               whether the resource is found for the skeleton.
+ *                       true if interval pattern found for the skeleton,
+ *                       false otherwise.
+ * @stable ICU 4.0
+ */
+UBool
+DateIntervalFormat::setSeparateDateTimePtn(
+                                 const UnicodeString& dateSkeleton,
+                                 const UnicodeString& timeSkeleton) {
+    const UnicodeString* skeleton;
+    // if both date and time skeleton present,
+    // the final interval pattern might include time interval patterns
+    // ( when, am_pm, hour, minute differ ),
+    // but not date interval patterns ( when year, month, day differ ).
+    // For year/month/day differ, it falls back to fall-back pattern.
+    if ( timeSkeleton.length() != 0  ) {
+        skeleton = &timeSkeleton;
+    } else {
+        skeleton = &dateSkeleton;
+    }
+
+    /* interval patterns for skeleton "dMMMy" (but not "dMMMMy")
+     * are defined in resource,
+     * interval patterns for skeleton "dMMMMy" are calculated by
+     * 1. get the best match skeleton for "dMMMMy", which is "dMMMy"
+     * 2. get the interval patterns for "dMMMy",
+     * 3. extend "MMM" to "MMMM" in above interval patterns for "dMMMMy"
+     * getBestSkeleton() is step 1.
+     */
+    // best skeleton, and the difference information
+    int8_t differenceInfo = 0;
+    const UnicodeString* bestSkeleton = fInfo->getBestSkeleton(*skeleton,
+                                                               differenceInfo);
+    /* best skeleton could be nullptr.
+       For example: in "ca" resource file,
+       interval format is defined as following
+           intervalFormats{
+                fallback{"{0} - {1}"}
+            }
+       there is no skeletons/interval patterns defined,
+       and the best skeleton match could be nullptr
+     */
+    if ( bestSkeleton == nullptr ) {
+        return false;
+    }
+
+    // Set patterns for fallback use, need to do this
+    // before returning if differenceInfo == -1
+    UErrorCode status;
+    if ( dateSkeleton.length() != 0) {
+        status = U_ZERO_ERROR;
+        fDatePattern = new UnicodeString(DateFormat::getBestPattern(
+                fLocale, dateSkeleton, status));
+        // no way to report OOM. :(
+    }
+    if ( timeSkeleton.length() != 0) {
+        status = U_ZERO_ERROR;
+        fTimePattern = new UnicodeString(DateFormat::getBestPattern(
+                fLocale, timeSkeleton, status));
+        // no way to report OOM. :(
+    }
+
+    // difference:
+    // 0 means the best matched skeleton is the same as input skeleton
+    // 1 means the fields are the same, but field width are different
+    // 2 means the only difference between fields are v/z,
+    // -1 means there are other fields difference
+    // (this will happen, for instance, if the supplied skeleton has seconds,
+    //  but no skeletons in the intervalFormats data do)
+    if ( differenceInfo == -1 ) {
+        // skeleton has different fields, not only  v/z difference
+        return false;
+    }
+
+    if ( timeSkeleton.length() == 0 ) {
+        UnicodeString extendedSkeleton;
+        UnicodeString extendedBestSkeleton;
+        // only has date skeleton
+        setIntervalPattern(UCAL_DATE, skeleton, bestSkeleton, differenceInfo,
+                           &extendedSkeleton, &extendedBestSkeleton);
+
+        UBool extended = setIntervalPattern(UCAL_MONTH, skeleton, bestSkeleton,
+                                     differenceInfo,
+                                     &extendedSkeleton, &extendedBestSkeleton);
+
+        if ( extended ) {
+            bestSkeleton = &extendedBestSkeleton;
+            skeleton = &extendedSkeleton;
+        }
+        setIntervalPattern(UCAL_YEAR, skeleton, bestSkeleton, differenceInfo,
+                           &extendedSkeleton, &extendedBestSkeleton);
+        setIntervalPattern(UCAL_ERA, skeleton, bestSkeleton, differenceInfo,
+                           &extendedSkeleton, &extendedBestSkeleton);
+     } else {
+        setIntervalPattern(UCAL_MINUTE, skeleton, bestSkeleton, differenceInfo);
+        setIntervalPattern(UCAL_HOUR, skeleton, bestSkeleton, differenceInfo);
+        setIntervalPattern(UCAL_AM_PM, skeleton, bestSkeleton, differenceInfo);
+    }
+    return true;
+}
+
+
+
+void
+DateIntervalFormat::setFallbackPattern(UCalendarDateFields field,
+                                       const UnicodeString& skeleton,
+                                       UErrorCode& status) {
+    if ( U_FAILURE(status) ) {
+        return;
+    }
+    UnicodeString pattern = DateFormat::getBestPattern(
+            fLocale, skeleton, status);
+    if ( U_FAILURE(status) ) {
+        return;
+    }
+    setPatternInfo(field, nullptr, &pattern, fInfo->getDefaultOrder());
+}
+
+
+
+
+void
+DateIntervalFormat::setPatternInfo(UCalendarDateFields field,
+                                   const UnicodeString* firstPart,
+                                   const UnicodeString* secondPart,
+                                   UBool laterDateFirst) {
+    // for fall back interval patterns,
+    // the first part of the pattern is empty,
+    // the second part of the pattern is the full-pattern
+    // should be used in fall-back.
+    UErrorCode status = U_ZERO_ERROR;
+    // following should not set any wrong status.
+    int32_t itvPtnIndex = DateIntervalInfo::calendarFieldToIntervalIndex(field,
+                                                                        status);
+    if ( U_FAILURE(status) ) {
+        return;
+    }
+    PatternInfo& ptn = fIntervalPatterns[itvPtnIndex];
+    if ( firstPart ) {
+        ptn.firstPart = *firstPart;
+    }
+    if ( secondPart ) {
+        ptn.secondPart = *secondPart;
+    }
+    ptn.laterDateFirst = laterDateFirst;
+}
+
+void
+DateIntervalFormat::setIntervalPattern(UCalendarDateFields field,
+                                       const UnicodeString& intervalPattern) {
+    UBool order = fInfo->getDefaultOrder();
+    setIntervalPattern(field, intervalPattern, order);
+}
+
+
+void
+DateIntervalFormat::setIntervalPattern(UCalendarDateFields field,
+                                       const UnicodeString& intervalPattern,
+                                       UBool laterDateFirst) {
+    const UnicodeString* pattern = &intervalPattern;
+    UBool order = laterDateFirst;
+    // check for "latestFirst:" or "earliestFirst:" prefix
+    int8_t prefixLength = UPRV_LENGTHOF(gLaterFirstPrefix);
+    int8_t earliestFirstLength = UPRV_LENGTHOF(gEarlierFirstPrefix);
+    UnicodeString realPattern;
+    if ( intervalPattern.startsWith(gLaterFirstPrefix, prefixLength) ) {
+        order = true;
+        intervalPattern.extract(prefixLength,
+                                intervalPattern.length() - prefixLength,
+                                realPattern);
+        pattern = &realPattern;
+    } else if ( intervalPattern.startsWith(gEarlierFirstPrefix,
+                                           earliestFirstLength) ) {
+        order = false;
+        intervalPattern.extract(earliestFirstLength,
+                                intervalPattern.length() - earliestFirstLength,
+                                realPattern);
+        pattern = &realPattern;
+    }
+
+    int32_t splitPoint = splitPatternInto2Part(*pattern);
+
+    UnicodeString firstPart;
+    UnicodeString secondPart;
+    pattern->extract(0, splitPoint, firstPart);
+    if ( splitPoint < pattern->length() ) {
+        pattern->extract(splitPoint, pattern->length()-splitPoint, secondPart);
+    }
+    setPatternInfo(field, &firstPart, &secondPart, order);
+}
+
+
+
+
+/**
+ * Generate interval pattern from existing resource
+ *
+ * It not only save the interval patterns,
+ * but also return the extended skeleton and its best match skeleton.
+ *
+ * @param field           largest different calendar field
+ * @param skeleton        skeleton
+ * @param bestSkeleton    the best match skeleton which has interval pattern
+ *                        defined in resource
+ * @param differenceInfo  the difference between skeleton and best skeleton
+ *         0 means the best matched skeleton is the same as input skeleton
+ *         1 means the fields are the same, but field width are different
+ *         2 means the only difference between fields are v/z,
+ *        -1 means there are other fields difference
+ *
+ * @param extendedSkeleton      extended skeleton
+ * @param extendedBestSkeleton  extended best match skeleton
+ * @return                      whether the interval pattern is found
+ *                              through extending skeleton or not.
+ *                              true if interval pattern is found by
+ *                              extending skeleton, false otherwise.
+ * @stable ICU 4.0
+ */
+UBool
+DateIntervalFormat::setIntervalPattern(UCalendarDateFields field,
+                                       const UnicodeString* skeleton,
+                                       const UnicodeString* bestSkeleton,
+                                       int8_t differenceInfo,
+                                       UnicodeString* extendedSkeleton,
+                                       UnicodeString* extendedBestSkeleton) {
+    UErrorCode status = U_ZERO_ERROR;
+    // following getIntervalPattern() should not generate error status
+    UnicodeString pattern;
+    fInfo->getIntervalPattern(*bestSkeleton, field, pattern, status);
+    if ( pattern.isEmpty() ) {
+        // single date
+        if ( SimpleDateFormat::isFieldUnitIgnored(*bestSkeleton, field) ) {
+            // do nothing, format will handle it
+            return false;
+        }
+
+        // for 24 hour system, interval patterns in resource file
+        // might not include pattern when am_pm differ,
+        // which should be the same as hour differ.
+        // add it here for simplicity
+        if ( field == UCAL_AM_PM ) {
+            fInfo->getIntervalPattern(*bestSkeleton, UCAL_HOUR, pattern,status);
+            if ( !pattern.isEmpty() ) {
+                UBool suppressDayPeriodField = fSkeleton.indexOf(CAP_J) != -1;
+                UnicodeString adjustIntervalPattern;
+                adjustFieldWidth(*skeleton, *bestSkeleton, pattern, differenceInfo,
+                                 suppressDayPeriodField, adjustIntervalPattern);
+                setIntervalPattern(field, adjustIntervalPattern);
+            }
+            return false;
+        }
+        // else, looking for pattern when 'y' differ for 'dMMMM' skeleton,
+        // first, get best match pattern "MMMd",
+        // since there is no pattern for 'y' differs for skeleton 'MMMd',
+        // need to look for it from skeleton 'yMMMd',
+        // if found, adjust field width in interval pattern from
+        // "MMM" to "MMMM".
+        char16_t fieldLetter = fgCalendarFieldToPatternLetter[field];
+        if ( extendedSkeleton ) {
+            *extendedSkeleton = *skeleton;
+            *extendedBestSkeleton = *bestSkeleton;
+            extendedSkeleton->insert(0, fieldLetter);
+            extendedBestSkeleton->insert(0, fieldLetter);
+            // for example, looking for patterns when 'y' differ for
+            // skeleton "MMMM".
+            fInfo->getIntervalPattern(*extendedBestSkeleton,field,pattern,status);
+            if ( pattern.isEmpty() && differenceInfo == 0 ) {
+                // if there is no skeleton "yMMMM" defined,
+                // look for the best match skeleton, for example: "yMMM"
+                const UnicodeString* tmpBest = fInfo->getBestSkeleton(
+                                        *extendedBestSkeleton, differenceInfo);
+                if ( tmpBest != 0 && differenceInfo != -1 ) {
+                    fInfo->getIntervalPattern(*tmpBest, field, pattern, status);
+                    bestSkeleton = tmpBest;
+                }
+            }
+        }
+    }
+    if ( !pattern.isEmpty() ) {
+        UBool suppressDayPeriodField = fSkeleton.indexOf(CAP_J) != -1;
+        if ( differenceInfo != 0 || suppressDayPeriodField) {
+            UnicodeString adjustIntervalPattern;
+            adjustFieldWidth(*skeleton, *bestSkeleton, pattern, differenceInfo,
+                              suppressDayPeriodField, adjustIntervalPattern);
+            setIntervalPattern(field, adjustIntervalPattern);
+        } else {
+            setIntervalPattern(field, pattern);
+        }
+        if ( extendedSkeleton && !extendedSkeleton->isEmpty() ) {
+            return true;
+        }
+    }
+    return false;
+}
+
+
+
+int32_t  U_EXPORT2
+DateIntervalFormat::splitPatternInto2Part(const UnicodeString& intervalPattern) {
+    UBool inQuote = false;
+    char16_t prevCh = 0;
+    int32_t count = 0;
+
+    /* repeatedPattern used to record whether a pattern has already seen.
+       It is a pattern applies to first calendar if it is first time seen,
+       otherwise, it is a pattern applies to the second calendar
+     */
+    UBool patternRepeated[] =
+    {
+    //       A   B   C   D   E   F   G   H   I   J   K   L   M   N   O
+             0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
+    //   P   Q   R   S   T   U   V   W   X   Y   Z
+         0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0, 0, 0,  0, 0, 0,
+    //       a   b   c   d   e   f   g   h   i   j   k   l   m   n   o
+         0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
+    //   p   q   r   s   t   u   v   w   x   y   z
+         0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0
+    };
+
+    int8_t PATTERN_CHAR_BASE = 0x41;
+
+    /* loop through the pattern string character by character looking for
+     * the first repeated pattern letter, which breaks the interval pattern
+     * into 2 parts.
+     */
+    int32_t i;
+    UBool foundRepetition = false;
+    for (i = 0; i < intervalPattern.length(); ++i) {
+        char16_t ch = intervalPattern.charAt(i);
+
+        if (ch != prevCh && count > 0) {
+            // check the repeativeness of pattern letter
+            UBool repeated = patternRepeated[(int)(prevCh - PATTERN_CHAR_BASE)];
+            if ( repeated == false ) {
+                patternRepeated[prevCh - PATTERN_CHAR_BASE] = true;
+            } else {
+                foundRepetition = true;
+                break;
+            }
+            count = 0;
+        }
+        if (ch == 0x0027 /*'*/) {
+            // Consecutive single quotes are a single quote literal,
+            // either outside of quotes or between quotes
+            if ((i+1) < intervalPattern.length() &&
+                intervalPattern.charAt(i+1) == 0x0027 /*'*/) {
+                ++i;
+            } else {
+                inQuote = ! inQuote;
+            }
+        }
+        else if (!inQuote && ((ch >= 0x0061 /*'a'*/ && ch <= 0x007A /*'z'*/)
+                    || (ch >= 0x0041 /*'A'*/ && ch <= 0x005A /*'Z'*/))) {
+            // ch is a date-time pattern character
+            prevCh = ch;
+            ++count;
+        }
+    }
+    // check last pattern char, distinguish
+    // "dd MM" ( no repetition ),
+    // "d-d"(last char repeated ), and
+    // "d-d MM" ( repetition found )
+    if ( count > 0 && foundRepetition == false ) {
+        if ( patternRepeated[(int)(prevCh - PATTERN_CHAR_BASE)] == false ) {
+            count = 0;
+        }
+    }
+    return (i - count);
+}
+
+// The following is only called from fallbackFormat, i.e. within the gFormatterMutex lock
+void DateIntervalFormat::fallbackFormatRange(
+        Calendar& fromCalendar,
+        Calendar& toCalendar,
+        UnicodeString& appendTo,
+        int8_t& firstIndex,
+        FieldPositionHandler& fphandler,
+        UErrorCode& status) const {
+    UnicodeString fallbackPattern;
+    fInfo->getFallbackIntervalPattern(fallbackPattern);
+    SimpleFormatter sf(fallbackPattern, 2, 2, status);
+    if (U_FAILURE(status)) {
+        return;
+    }
+    int32_t offsets[2];
+    UnicodeString patternBody = sf.getTextWithNoArguments(offsets, 2);
+
+    UErrorCode tempStatus = U_ZERO_ERROR; // for setContext, ignored
+    // TODO(ICU-20406): Use SimpleFormatter Iterator interface when available.
+    if (offsets[0] < offsets[1]) {
+        firstIndex = 0;
+        appendTo.append(patternBody.tempSubStringBetween(0, offsets[0]));
+        fDateFormat->_format(fromCalendar, appendTo, fphandler, status);
+        appendTo.append(patternBody.tempSubStringBetween(offsets[0], offsets[1]));
+        // No capitalization for second part of interval
+        fDateFormat->setContext(UDISPCTX_CAPITALIZATION_NONE, tempStatus);
+        fDateFormat->_format(toCalendar, appendTo, fphandler, status);
+        appendTo.append(patternBody.tempSubStringBetween(offsets[1]));
+    } else {
+        firstIndex = 1;
+        appendTo.append(patternBody.tempSubStringBetween(0, offsets[1]));
+        fDateFormat->_format(toCalendar, appendTo, fphandler, status);
+        appendTo.append(patternBody.tempSubStringBetween(offsets[1], offsets[0]));
+        // No capitalization for second part of interval
+        fDateFormat->setContext(UDISPCTX_CAPITALIZATION_NONE, tempStatus);
+        fDateFormat->_format(fromCalendar, appendTo, fphandler, status);
+        appendTo.append(patternBody.tempSubStringBetween(offsets[0]));
+    }
+}
+
+// The following is only called from formatImpl, i.e. within the gFormatterMutex lock
+UnicodeString&
+DateIntervalFormat::fallbackFormat(Calendar& fromCalendar,
+                                   Calendar& toCalendar,
+                                   UBool fromToOnSameDay, // new
+                                   UnicodeString& appendTo,
+                                   int8_t& firstIndex,
+                                   FieldPositionHandler& fphandler,
+                                   UErrorCode& status) const {
+    if ( U_FAILURE(status) ) {
+        return appendTo;
+    }
+
+    UBool formatDatePlusTimeRange = (fromToOnSameDay && fDatePattern && fTimePattern);
+    if (formatDatePlusTimeRange) {
+        SimpleFormatter sf(*fDateTimeFormat, 2, 2, status);
+        if (U_FAILURE(status)) {
+            return appendTo;
+        }
+        int32_t offsets[2];
+        UnicodeString patternBody = sf.getTextWithNoArguments(offsets, 2);
+
+        UnicodeString fullPattern; // for saving the pattern in fDateFormat
+        fDateFormat->toPattern(fullPattern); // save current pattern, restore later
+
+        UErrorCode tempStatus = U_ZERO_ERROR; // for setContext, ignored
+        // {0} is time range
+        // {1} is single date portion
+        // TODO(ICU-20406): Use SimpleFormatter Iterator interface when available.
+        if (offsets[0] < offsets[1]) {
+            appendTo.append(patternBody.tempSubStringBetween(0, offsets[0]));
+            fDateFormat->applyPattern(*fTimePattern);
+            fallbackFormatRange(fromCalendar, toCalendar, appendTo, firstIndex, fphandler, status);
+            appendTo.append(patternBody.tempSubStringBetween(offsets[0], offsets[1]));
+            fDateFormat->applyPattern(*fDatePattern);
+            // No capitalization for second portion
+            fDateFormat->setContext(UDISPCTX_CAPITALIZATION_NONE, tempStatus);
+            fDateFormat->_format(fromCalendar, appendTo, fphandler, status);
+            appendTo.append(patternBody.tempSubStringBetween(offsets[1]));
+        } else {
+            appendTo.append(patternBody.tempSubStringBetween(0, offsets[1]));
+            fDateFormat->applyPattern(*fDatePattern);
+            fDateFormat->_format(fromCalendar, appendTo, fphandler, status);
+            appendTo.append(patternBody.tempSubStringBetween(offsets[1], offsets[0]));
+            fDateFormat->applyPattern(*fTimePattern);
+            // No capitalization for second portion
+            fDateFormat->setContext(UDISPCTX_CAPITALIZATION_NONE, tempStatus);
+            fallbackFormatRange(fromCalendar, toCalendar, appendTo, firstIndex, fphandler, status);
+            appendTo.append(patternBody.tempSubStringBetween(offsets[0]));
+        }
+
+        // restore full pattern
+        fDateFormat->applyPattern(fullPattern);
+    } else {
+        fallbackFormatRange(fromCalendar, toCalendar, appendTo, firstIndex, fphandler, status);
+    }
+    return appendTo;
+}
+
+
+
+
+UBool  U_EXPORT2
+DateIntervalFormat::fieldExistsInSkeleton(UCalendarDateFields field,
+                                          const UnicodeString& skeleton)
+{
+    const char16_t fieldChar = fgCalendarFieldToPatternLetter[field];
+    return ( (skeleton.indexOf(fieldChar) == -1)?false:true ) ;
+}
+
+
+
+void  U_EXPORT2
+DateIntervalFormat::adjustFieldWidth(const UnicodeString& inputSkeleton,
+                 const UnicodeString& bestMatchSkeleton,
+                 const UnicodeString& bestIntervalPattern,
+                 int8_t differenceInfo,
+                 UBool suppressDayPeriodField,
+                 UnicodeString& adjustedPtn) {
+    adjustedPtn = bestIntervalPattern;
+    int32_t inputSkeletonFieldWidth[] =
+    {
+    //       A   B   C   D   E   F   G   H   I   J   K   L   M   N   O
+             0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
+    //   P   Q   R   S   T   U   V   W   X   Y   Z
+         0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0, 0, 0,  0, 0, 0,
+    //       a   b   c   d   e   f   g   h   i   j   k   l   m   n   o
+         0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
+    //   p   q   r   s   t   u   v   w   x   y   z
+         0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0
+    };
+
+    int32_t bestMatchSkeletonFieldWidth[] =
+    {
+    //       A   B   C   D   E   F   G   H   I   J   K   L   M   N   O
+             0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
+    //   P   Q   R   S   T   U   V   W   X   Y   Z
+         0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0, 0, 0,  0, 0, 0,
+    //       a   b   c   d   e   f   g   h   i   j   k   l   m   n   o
+         0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
+    //   p   q   r   s   t   u   v   w   x   y   z
+         0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0
+    };
+
+    const int8_t PATTERN_CHAR_BASE = 0x41;
+
+    DateIntervalInfo::parseSkeleton(inputSkeleton, inputSkeletonFieldWidth);
+    DateIntervalInfo::parseSkeleton(bestMatchSkeleton, bestMatchSkeletonFieldWidth);
+    if (suppressDayPeriodField) {
+        // remove the 'a' and any NBSP/NNBSP on one side of it
+        findReplaceInPattern(adjustedPtn, UnicodeString(u"\u00A0a",-1), UnicodeString());
+        findReplaceInPattern(adjustedPtn, UnicodeString(u"\u202Fa",-1), UnicodeString());
+        findReplaceInPattern(adjustedPtn, UnicodeString(u"a\u00A0",-1), UnicodeString());
+        findReplaceInPattern(adjustedPtn, UnicodeString(u"a\u202F",-1), UnicodeString());
+        findReplaceInPattern(adjustedPtn, UnicodeString(LOW_A), UnicodeString());
+        // adjust interior double spaces, remove exterior whitespace
+        findReplaceInPattern(adjustedPtn, UnicodeString("  "), UnicodeString(" "));
+        adjustedPtn.trim();
+    }
+    if ( differenceInfo == 2 ) {
+        if (inputSkeleton.indexOf(LOW_Z) != -1) {
+             findReplaceInPattern(adjustedPtn, UnicodeString(LOW_V), UnicodeString(LOW_Z));
+         }
+         if (inputSkeleton.indexOf(CAP_K) != -1) {
+             findReplaceInPattern(adjustedPtn, UnicodeString(LOW_H), UnicodeString(CAP_K));
+         }
+         if (inputSkeleton.indexOf(LOW_K) != -1) {
+             findReplaceInPattern(adjustedPtn, UnicodeString(CAP_H), UnicodeString(LOW_K));
+         }
+         if (inputSkeleton.indexOf(LOW_B) != -1) {
+             findReplaceInPattern(adjustedPtn, UnicodeString(LOW_A), UnicodeString(LOW_B));
+         }
+    }
+    if (adjustedPtn.indexOf(LOW_A) != -1 && bestMatchSkeletonFieldWidth[LOW_A - PATTERN_CHAR_BASE] == 0) {
+        bestMatchSkeletonFieldWidth[LOW_A - PATTERN_CHAR_BASE] = 1;
+    }
+    if (adjustedPtn.indexOf(LOW_B) != -1 && bestMatchSkeletonFieldWidth[LOW_B - PATTERN_CHAR_BASE] == 0) {
+        bestMatchSkeletonFieldWidth[LOW_B - PATTERN_CHAR_BASE] = 1;
+     }
+
+    UBool inQuote = false;
+    char16_t prevCh = 0;
+    int32_t count = 0;
+
+    // loop through the pattern string character by character
+    int32_t adjustedPtnLength = adjustedPtn.length();
+    int32_t i;
+    for (i = 0; i < adjustedPtnLength; ++i) {
+        char16_t ch = adjustedPtn.charAt(i);
+        if (ch != prevCh && count > 0) {
+            // check the repeativeness of pattern letter
+            char16_t skeletonChar = prevCh;
+            if ( skeletonChar ==  CAP_L ) {
+                // there is no "L" (always be "M") in skeleton,
+                // but there is "L" in pattern.
+                // for skeleton "M+", the pattern might be "...L..."
+                skeletonChar = CAP_M;
+            }
+            int32_t fieldCount = bestMatchSkeletonFieldWidth[(int)(skeletonChar - PATTERN_CHAR_BASE)];
+            int32_t inputFieldCount = inputSkeletonFieldWidth[(int)(skeletonChar - PATTERN_CHAR_BASE)];
+            if ( fieldCount == count && inputFieldCount > fieldCount ) {
+                count = inputFieldCount - fieldCount;
+                int32_t j;
+                for ( j = 0; j < count; ++j ) {
+                    adjustedPtn.insert(i, prevCh);
+                }
+                i += count;
+                adjustedPtnLength += count;
+            }
+            count = 0;
+        }
+        if (ch == 0x0027 /*'*/) {
+            // Consecutive single quotes are a single quote literal,
+            // either outside of quotes or between quotes
+            if ((i+1) < adjustedPtn.length() && adjustedPtn.charAt(i+1) == 0x0027 /* ' */) {
+                ++i;
+            } else {
+                inQuote = ! inQuote;
+            }
+        }
+        else if ( ! inQuote && ((ch >= 0x0061 /*'a'*/ && ch <= 0x007A /*'z'*/)
+                    || (ch >= 0x0041 /*'A'*/ && ch <= 0x005A /*'Z'*/))) {
+            // ch is a date-time pattern character
+            prevCh = ch;
+            ++count;
+        }
+    }
+    if ( count > 0 ) {
+        // last item
+        // check the repeativeness of pattern letter
+        char16_t skeletonChar = prevCh;
+        if ( skeletonChar == CAP_L ) {
+            // there is no "L" (always be "M") in skeleton,
+            // but there is "L" in pattern.
+            // for skeleton "M+", the pattern might be "...L..."
+            skeletonChar = CAP_M;
+        }
+        int32_t fieldCount = bestMatchSkeletonFieldWidth[(int)(skeletonChar - PATTERN_CHAR_BASE)];
+        int32_t inputFieldCount = inputSkeletonFieldWidth[(int)(skeletonChar - PATTERN_CHAR_BASE)];
+        if ( fieldCount == count && inputFieldCount > fieldCount ) {
+            count = inputFieldCount - fieldCount;
+            int32_t j;
+            for ( j = 0; j < count; ++j ) {
+                adjustedPtn.append(prevCh);
+            }
+        }
+    }
+}
+
+void
+DateIntervalFormat::findReplaceInPattern(UnicodeString& targetString,
+                                         const UnicodeString& strToReplace,
+                                         const UnicodeString& strToReplaceWith) {
+    int32_t firstQuoteIndex = targetString.indexOf(u'\'');
+    if (firstQuoteIndex == -1) {
+        targetString.findAndReplace(strToReplace, strToReplaceWith);
+    } else {
+        UnicodeString result;
+        UnicodeString source = targetString;
+        
+        while (firstQuoteIndex >= 0) {
+            int32_t secondQuoteIndex = source.indexOf(u'\'', firstQuoteIndex + 1);
+            if (secondQuoteIndex == -1) {
+                secondQuoteIndex = source.length() - 1;
+            }
+            
+            UnicodeString unquotedText(source, 0, firstQuoteIndex);
+            UnicodeString quotedText(source, firstQuoteIndex, secondQuoteIndex - firstQuoteIndex + 1);
+            
+            unquotedText.findAndReplace(strToReplace, strToReplaceWith);
+            result += unquotedText;
+            result += quotedText;
+            
+            source.remove(0, secondQuoteIndex + 1);
+            firstQuoteIndex = source.indexOf(u'\'');
+        }
+        source.findAndReplace(strToReplace, strToReplaceWith);
+        result += source;
+        targetString = result;
+    }
+}
+
+
+
+void
+DateIntervalFormat::concatSingleDate2TimeInterval(UnicodeString& format,
+                                              const UnicodeString& datePattern,
+                                              UCalendarDateFields field,
+                                              UErrorCode& status) {
+    // following should not set wrong status
+    int32_t itvPtnIndex = DateIntervalInfo::calendarFieldToIntervalIndex(field,
+                                                                        status);
+    if ( U_FAILURE(status) ) {
+        return;
+    }
+    PatternInfo&  timeItvPtnInfo = fIntervalPatterns[itvPtnIndex];
+    if ( !timeItvPtnInfo.firstPart.isEmpty() ) {
+        UnicodeString timeIntervalPattern(timeItvPtnInfo.firstPart);
+        timeIntervalPattern.append(timeItvPtnInfo.secondPart);
+        UnicodeString combinedPattern;
+        SimpleFormatter(format, 2, 2, status).
+                format(timeIntervalPattern, datePattern, combinedPattern, status);
+        if ( U_FAILURE(status) ) {
+            return;
+        }
+        setIntervalPattern(field, combinedPattern, timeItvPtnInfo.laterDateFirst);
+    }
+    // else: fall back
+    // it should not happen if the interval format defined is valid
+}
+
+
+
+const char16_t
+DateIntervalFormat::fgCalendarFieldToPatternLetter[] =
+{
+    /*GyM*/ CAP_G, LOW_Y, CAP_M,
+    /*wWd*/ LOW_W, CAP_W, LOW_D,
+    /*DEF*/ CAP_D, CAP_E, CAP_F,
+    /*ahH*/ LOW_A, LOW_H, CAP_H,
+    /*msS*/ LOW_M, LOW_S, CAP_S, // MINUTE, SECOND, MILLISECOND
+    /*z.Y*/ LOW_Z, SPACE, CAP_Y, // ZONE_OFFSET, DST_OFFSET, YEAR_WOY,
+    /*eug*/ LOW_E, LOW_U, LOW_G, // DOW_LOCAL, EXTENDED_YEAR, JULIAN_DAY,
+    /*A..*/ CAP_A, SPACE, SPACE, // MILLISECONDS_IN_DAY, IS_LEAP_MONTH, FIELD_COUNT
+};
+
+
+
+U_NAMESPACE_END
+
+#endif