Adding upstream version 3.40.1.upstream/3.40.1upstream

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

1 files changed, 972 insertions, 0 deletions

diff --git a/src/os_kv.c b/src/os_kv.c
new file mode 100644
index 0000000..322588b
--- /dev/null
+++ b/src/os_kv.c
@@ -0,0 +1,972 @@
+/*
+** 2022-09-06
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains an experimental VFS layer that operates on a
+** Key/Value storage engine where both keys and values must be pure
+** text.
+*/
+#include <sqliteInt.h>
+#if SQLITE_OS_KV || (SQLITE_OS_UNIX && defined(SQLITE_OS_KV_OPTIONAL))
+
+/*****************************************************************************
+** Debugging logic
+*/
+
+/* SQLITE_KV_TRACE() is used for tracing calls to kvstorage routines. */
+#if 0
+#define SQLITE_KV_TRACE(X)  printf X
+#else
+#define SQLITE_KV_TRACE(X)
+#endif
+
+/* SQLITE_KV_LOG() is used for tracing calls to the VFS interface */
+#if 0
+#define SQLITE_KV_LOG(X)  printf X
+#else
+#define SQLITE_KV_LOG(X)
+#endif
+
+
+/*
+** Forward declaration of objects used by this VFS implementation
+*/
+typedef struct KVVfsFile KVVfsFile;
+
+/* A single open file.  There are only two files represented by this
+** VFS - the database and the rollback journal.
+*/
+struct KVVfsFile {
+  sqlite3_file base;              /* IO methods */
+  const char *zClass;             /* Storage class */
+  int isJournal;                  /* True if this is a journal file */
+  unsigned int nJrnl;             /* Space allocated for aJrnl[] */
+  char *aJrnl;                    /* Journal content */
+  int szPage;                     /* Last known page size */
+  sqlite3_int64 szDb;             /* Database file size.  -1 means unknown */
+};
+
+/*
+** Methods for KVVfsFile
+*/
+static int kvvfsClose(sqlite3_file*);
+static int kvvfsReadDb(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
+static int kvvfsReadJrnl(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
+static int kvvfsWriteDb(sqlite3_file*,const void*,int iAmt, sqlite3_int64);
+static int kvvfsWriteJrnl(sqlite3_file*,const void*,int iAmt, sqlite3_int64);
+static int kvvfsTruncateDb(sqlite3_file*, sqlite3_int64 size);
+static int kvvfsTruncateJrnl(sqlite3_file*, sqlite3_int64 size);
+static int kvvfsSyncDb(sqlite3_file*, int flags);
+static int kvvfsSyncJrnl(sqlite3_file*, int flags);
+static int kvvfsFileSizeDb(sqlite3_file*, sqlite3_int64 *pSize);
+static int kvvfsFileSizeJrnl(sqlite3_file*, sqlite3_int64 *pSize);
+static int kvvfsLock(sqlite3_file*, int);
+static int kvvfsUnlock(sqlite3_file*, int);
+static int kvvfsCheckReservedLock(sqlite3_file*, int *pResOut);
+static int kvvfsFileControlDb(sqlite3_file*, int op, void *pArg);
+static int kvvfsFileControlJrnl(sqlite3_file*, int op, void *pArg);
+static int kvvfsSectorSize(sqlite3_file*);
+static int kvvfsDeviceCharacteristics(sqlite3_file*);
+
+/*
+** Methods for sqlite3_vfs
+*/
+static int kvvfsOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
+static int kvvfsDelete(sqlite3_vfs*, const char *zName, int syncDir);
+static int kvvfsAccess(sqlite3_vfs*, const char *zName, int flags, int *);
+static int kvvfsFullPathname(sqlite3_vfs*, const char *zName, int, char *zOut);
+static void *kvvfsDlOpen(sqlite3_vfs*, const char *zFilename);
+static int kvvfsRandomness(sqlite3_vfs*, int nByte, char *zOut);
+static int kvvfsSleep(sqlite3_vfs*, int microseconds);
+static int kvvfsCurrentTime(sqlite3_vfs*, double*);
+static int kvvfsCurrentTimeInt64(sqlite3_vfs*, sqlite3_int64*);
+
+static sqlite3_vfs sqlite3OsKvvfsObject = {
+  1,                              /* iVersion */
+  sizeof(KVVfsFile),              /* szOsFile */
+  1024,                           /* mxPathname */
+  0,                              /* pNext */
+  "kvvfs",                        /* zName */
+  0,                              /* pAppData */
+  kvvfsOpen,                      /* xOpen */
+  kvvfsDelete,                    /* xDelete */
+  kvvfsAccess,                    /* xAccess */
+  kvvfsFullPathname,              /* xFullPathname */
+  kvvfsDlOpen,                    /* xDlOpen */
+  0,                              /* xDlError */
+  0,                              /* xDlSym */
+  0,                              /* xDlClose */
+  kvvfsRandomness,                /* xRandomness */
+  kvvfsSleep,                     /* xSleep */
+  kvvfsCurrentTime,               /* xCurrentTime */
+  0,                              /* xGetLastError */
+  kvvfsCurrentTimeInt64           /* xCurrentTimeInt64 */
+};
+
+/* Methods for sqlite3_file objects referencing a database file
+*/
+static sqlite3_io_methods kvvfs_db_io_methods = {
+  1,                              /* iVersion */
+  kvvfsClose,                     /* xClose */
+  kvvfsReadDb,                    /* xRead */
+  kvvfsWriteDb,                   /* xWrite */
+  kvvfsTruncateDb,                /* xTruncate */
+  kvvfsSyncDb,                    /* xSync */
+  kvvfsFileSizeDb,                /* xFileSize */
+  kvvfsLock,                      /* xLock */
+  kvvfsUnlock,                    /* xUnlock */
+  kvvfsCheckReservedLock,         /* xCheckReservedLock */
+  kvvfsFileControlDb,             /* xFileControl */
+  kvvfsSectorSize,                /* xSectorSize */
+  kvvfsDeviceCharacteristics,     /* xDeviceCharacteristics */
+  0,                              /* xShmMap */
+  0,                              /* xShmLock */
+  0,                              /* xShmBarrier */
+  0,                              /* xShmUnmap */
+  0,                              /* xFetch */
+  0                               /* xUnfetch */
+};
+
+/* Methods for sqlite3_file objects referencing a rollback journal
+*/
+static sqlite3_io_methods kvvfs_jrnl_io_methods = {
+  1,                              /* iVersion */
+  kvvfsClose,                     /* xClose */
+  kvvfsReadJrnl,                  /* xRead */
+  kvvfsWriteJrnl,                 /* xWrite */
+  kvvfsTruncateJrnl,              /* xTruncate */
+  kvvfsSyncJrnl,                  /* xSync */
+  kvvfsFileSizeJrnl,              /* xFileSize */
+  kvvfsLock,                      /* xLock */
+  kvvfsUnlock,                    /* xUnlock */
+  kvvfsCheckReservedLock,         /* xCheckReservedLock */
+  kvvfsFileControlJrnl,           /* xFileControl */
+  kvvfsSectorSize,                /* xSectorSize */
+  kvvfsDeviceCharacteristics,     /* xDeviceCharacteristics */
+  0,                              /* xShmMap */
+  0,                              /* xShmLock */
+  0,                              /* xShmBarrier */
+  0,                              /* xShmUnmap */
+  0,                              /* xFetch */
+  0                               /* xUnfetch */
+};
+
+/****** Storage subsystem **************************************************/
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+/* Forward declarations for the low-level storage engine
+*/
+static int kvstorageWrite(const char*, const char *zKey, const char *zData);
+static int kvstorageDelete(const char*, const char *zKey);
+static int kvstorageRead(const char*, const char *zKey, char *zBuf, int nBuf);
+#define KVSTORAGE_KEY_SZ  32
+
+/* Expand the key name with an appropriate prefix and put the result
+** zKeyOut[].  The zKeyOut[] buffer is assumed to hold at least
+** KVSTORAGE_KEY_SZ bytes.
+*/
+static void kvstorageMakeKey(
+  const char *zClass,
+  const char *zKeyIn,
+  char *zKeyOut
+){
+  sqlite3_snprintf(KVSTORAGE_KEY_SZ, zKeyOut, "kvvfs-%s-%s", zClass, zKeyIn);
+}
+
+/* Write content into a key.  zClass is the particular namespace of the
+** underlying key/value store to use - either "local" or "session".
+**
+** Both zKey and zData are zero-terminated pure text strings.
+**
+** Return the number of errors.
+*/
+static int kvstorageWrite(
+  const char *zClass,
+  const char *zKey,
+  const char *zData
+){
+  FILE *fd;
+  char zXKey[KVSTORAGE_KEY_SZ];
+  kvstorageMakeKey(zClass, zKey, zXKey);
+  fd = fopen(zXKey, "wb");
+  if( fd ){
+    SQLITE_KV_TRACE(("KVVFS-WRITE  %-15s (%d) %.50s%s\n", zXKey,
+                 (int)strlen(zData), zData,
+                 strlen(zData)>50 ? "..." : ""));
+    fputs(zData, fd);
+    fclose(fd);
+    return 0;
+  }else{
+    return 1;
+  }
+}
+
+/* Delete a key (with its corresponding data) from the key/value
+** namespace given by zClass.  If the key does not previously exist,
+** this routine is a no-op.
+*/
+static int kvstorageDelete(const char *zClass, const char *zKey){
+  char zXKey[KVSTORAGE_KEY_SZ];
+  kvstorageMakeKey(zClass, zKey, zXKey);
+  unlink(zXKey);
+  SQLITE_KV_TRACE(("KVVFS-DELETE %-15s\n", zXKey));
+  return 0;
+}
+
+/* Read the value associated with a zKey from the key/value namespace given
+** by zClass and put the text data associated with that key in the first
+** nBuf bytes of zBuf[].  The value might be truncated if zBuf is not large
+** enough to hold it all.  The value put into zBuf must always be zero
+** terminated, even if it gets truncated because nBuf is not large enough.
+**
+** Return the total number of bytes in the data, without truncation, and
+** not counting the final zero terminator.   Return -1 if the key does
+** not exist.
+**
+** If nBuf<=0 then this routine simply returns the size of the data without
+** actually reading it.
+*/
+static int kvstorageRead(
+  const char *zClass,
+  const char *zKey,
+  char *zBuf,
+  int nBuf
+){
+  FILE *fd;
+  struct stat buf;
+  char zXKey[KVSTORAGE_KEY_SZ];
+  kvstorageMakeKey(zClass, zKey, zXKey);
+  if( access(zXKey, R_OK)!=0
+   || stat(zXKey, &buf)!=0
+   || !S_ISREG(buf.st_mode)
+  ){
+    SQLITE_KV_TRACE(("KVVFS-READ   %-15s (-1)\n", zXKey));
+    return -1;
+  }
+  if( nBuf<=0 ){
+    return (int)buf.st_size;
+  }else if( nBuf==1 ){
+    zBuf[0] = 0;
+    SQLITE_KV_TRACE(("KVVFS-READ   %-15s (%d)\n", zXKey,
+                 (int)buf.st_size));
+    return (int)buf.st_size;
+  }
+  if( nBuf > buf.st_size + 1 ){
+    nBuf = buf.st_size + 1;
+  }
+  fd = fopen(zXKey, "rb");
+  if( fd==0 ){
+    SQLITE_KV_TRACE(("KVVFS-READ   %-15s (-1)\n", zXKey));
+    return -1;
+  }else{
+    sqlite3_int64 n = fread(zBuf, 1, nBuf-1, fd);
+    fclose(fd);
+    zBuf[n] = 0;
+    SQLITE_KV_TRACE(("KVVFS-READ   %-15s (%lld) %.50s%s\n", zXKey,
+                 n, zBuf, n>50 ? "..." : ""));
+    return (int)n;
+  }
+}
+
+/*
+** An internal level of indirection which enables us to replace the
+** kvvfs i/o methods with JavaScript implementations in WASM builds.
+** Maintenance reminder: if this struct changes in any way, the JSON
+** rendering of its structure must be updated in
+** sqlite3_wasm_enum_json(). There are no binary compatibility
+** concerns, so it does not need an iVersion member. This file is
+** necessarily always compiled together with sqlite3_wasm_enum_json(),
+** and JS code dynamically creates the mapping of members based on
+** that JSON description.
+*/
+typedef struct sqlite3_kvvfs_methods sqlite3_kvvfs_methods;
+struct sqlite3_kvvfs_methods {
+  int (*xRead)(const char *zClass, const char *zKey, char *zBuf, int nBuf);
+  int (*xWrite)(const char *zClass, const char *zKey, const char *zData);
+  int (*xDelete)(const char *zClass, const char *zKey);
+  const int nKeySize;
+};
+
+/*
+** This object holds the kvvfs I/O methods which may be swapped out
+** for JavaScript-side implementations in WASM builds. In such builds
+** it cannot be const, but in native builds it should be so that
+** the compiler can hopefully optimize this level of indirection out.
+** That said, kvvfs is intended primarily for use in WASM builds.
+**
+** Note that this is not explicitly flagged as static because the
+** amalgamation build will tag it with SQLITE_PRIVATE.
+*/
+#ifndef SQLITE_WASM
+const
+#endif
+sqlite3_kvvfs_methods sqlite3KvvfsMethods = {
+kvstorageRead,
+kvstorageWrite,
+kvstorageDelete,
+KVSTORAGE_KEY_SZ
+};
+
+/****** Utility subroutines ************************************************/
+
+/*
+** Encode binary into the text encoded used to persist on disk.
+** The output text is stored in aOut[], which must be at least
+** nData+1 bytes in length.
+**
+** Return the actual length of the encoded text, not counting the
+** zero terminator at the end.
+**
+** Encoding format
+** ---------------
+**
+**   *  Non-zero bytes are encoded as upper-case hexadecimal
+**
+**   *  A sequence of one or more zero-bytes that are not at the
+**      beginning of the buffer are encoded as a little-endian
+**      base-26 number using a..z.  "a" means 0.  "b" means 1,
+**      "z" means 25.  "ab" means 26.  "ac" means 52.  And so forth.
+**
+**   *  Because there is no overlap between the encoding characters
+**      of hexadecimal and base-26 numbers, it is always clear where
+**      one stops and the next begins.
+*/
+static int kvvfsEncode(const char *aData, int nData, char *aOut){
+  int i, j;
+  const unsigned char *a = (const unsigned char*)aData;
+  for(i=j=0; i<nData; i++){
+    unsigned char c = a[i];
+    if( c!=0 ){
+      aOut[j++] = "0123456789ABCDEF"[c>>4];
+      aOut[j++] = "0123456789ABCDEF"[c&0xf];
+    }else{
+      /* A sequence of 1 or more zeros is stored as a little-endian
+      ** base-26 number using a..z as the digits. So one zero is "b".
+      ** Two zeros is "c". 25 zeros is "z", 26 zeros is "ab", 27 is "bb",
+      ** and so forth.
+      */
+      int k;
+      for(k=1; i+k<nData && a[i+k]==0; k++){}
+      i += k-1;
+      while( k>0 ){
+        aOut[j++] = 'a'+(k%26);
+        k /= 26;
+      }
+    }
+  }
+  aOut[j] = 0;
+  return j;
+}
+
+static const signed char kvvfsHexValue[256] = {
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+   0,  1,  2,  3,  4,  5,  6,  7,    8,  9, -1, -1, -1, -1, -1, -1,
+  -1, 10, 11, 12, 13, 14, 15, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1
+};
+
+/*
+** Decode the text encoding back to binary.  The binary content is
+** written into pOut, which must be at least nOut bytes in length.
+**
+** The return value is the number of bytes actually written into aOut[].
+*/
+static int kvvfsDecode(const char *a, char *aOut, int nOut){
+  int i, j;
+  int c;
+  const unsigned char *aIn = (const unsigned char*)a;
+  i = 0;
+  j = 0;
+  while( 1 ){
+    c = kvvfsHexValue[aIn[i]];
+    if( c<0 ){
+      int n = 0;
+      int mult = 1;
+      c = aIn[i];
+      if( c==0 ) break;
+      while( c>='a' && c<='z' ){
+        n += (c - 'a')*mult;
+        mult *= 26;
+        c = aIn[++i];
+      }
+      if( j+n>nOut ) return -1;
+      memset(&aOut[j], 0, n);
+      j += n;
+      c = aIn[i];
+      if( c==0 ) break;
+    }else{
+      aOut[j] = c<<4;
+      c = kvvfsHexValue[aIn[++i]];
+      if( c<0 ) break;
+      aOut[j++] += c;
+      i++;
+    }
+  }
+  return j;
+}
+
+/*
+** Decode a complete journal file.  Allocate space in pFile->aJrnl
+** and store the decoding there.  Or leave pFile->aJrnl set to NULL
+** if an error is encountered.
+**
+** The first few characters of the text encoding will be a little-endian
+** base-26 number (digits a..z) that is the total number of bytes
+** in the decoded journal file image.  This base-26 number is followed
+** by a single space, then the encoding of the journal.  The space
+** separator is required to act as a terminator for the base-26 number.
+*/
+static void kvvfsDecodeJournal(
+  KVVfsFile *pFile,      /* Store decoding in pFile->aJrnl */
+  const char *zTxt,      /* Text encoding.  Zero-terminated */
+  int nTxt               /* Bytes in zTxt, excluding zero terminator */
+){
+  unsigned int n = 0;
+  int c, i, mult;
+  i = 0;
+  mult = 1;
+  while( (c = zTxt[i++])>='a' && c<='z' ){
+    n += (zTxt[i] - 'a')*mult;
+    mult *= 26;
+  }
+  sqlite3_free(pFile->aJrnl);
+  pFile->aJrnl = sqlite3_malloc64( n );
+  if( pFile->aJrnl==0 ){
+    pFile->nJrnl = 0;
+    return;
+  }
+  pFile->nJrnl = n;
+  n = kvvfsDecode(zTxt+i, pFile->aJrnl, pFile->nJrnl);
+  if( n<pFile->nJrnl ){
+    sqlite3_free(pFile->aJrnl);
+    pFile->aJrnl = 0;
+    pFile->nJrnl = 0;
+  }
+}
+
+/*
+** Read or write the "sz" element, containing the database file size.
+*/
+static sqlite3_int64 kvvfsReadFileSize(KVVfsFile *pFile){
+  char zData[50];
+  zData[0] = 0;
+  sqlite3KvvfsMethods.xRead(pFile->zClass, "sz", zData, sizeof(zData)-1);
+  return strtoll(zData, 0, 0);
+}
+static int kvvfsWriteFileSize(KVVfsFile *pFile, sqlite3_int64 sz){
+  char zData[50];
+  sqlite3_snprintf(sizeof(zData), zData, "%lld", sz);
+  return sqlite3KvvfsMethods.xWrite(pFile->zClass, "sz", zData);
+}
+
+/****** sqlite3_io_methods methods ******************************************/
+
+/*
+** Close an kvvfs-file.
+*/
+static int kvvfsClose(sqlite3_file *pProtoFile){
+  KVVfsFile *pFile = (KVVfsFile *)pProtoFile;
+
+  SQLITE_KV_LOG(("xClose %s %s\n", pFile->zClass, 
+             pFile->isJournal ? "journal" : "db"));
+  sqlite3_free(pFile->aJrnl);
+  return SQLITE_OK;
+}
+
+/*
+** Read from the -journal file.
+*/
+static int kvvfsReadJrnl(
+  sqlite3_file *pProtoFile,
+  void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  KVVfsFile *pFile = (KVVfsFile*)pProtoFile;
+  assert( pFile->isJournal );
+  SQLITE_KV_LOG(("xRead('%s-journal',%d,%lld)\n", pFile->zClass, iAmt, iOfst));
+  if( pFile->aJrnl==0 ){
+    int szTxt = kvstorageRead(pFile->zClass, "jrnl", 0, 0);
+    char *aTxt;
+    if( szTxt<=4 ){
+      return SQLITE_IOERR;
+    }
+    aTxt = sqlite3_malloc64( szTxt+1 );
+    if( aTxt==0 ) return SQLITE_NOMEM;
+    kvstorageRead(pFile->zClass, "jrnl", aTxt, szTxt+1);
+    kvvfsDecodeJournal(pFile, aTxt, szTxt);
+    sqlite3_free(aTxt);
+    if( pFile->aJrnl==0 ) return SQLITE_IOERR;
+  }
+  if( iOfst+iAmt>pFile->nJrnl ){
+    return SQLITE_IOERR_SHORT_READ;
+  }
+  memcpy(zBuf, pFile->aJrnl+iOfst, iAmt);
+  return SQLITE_OK;
+}
+
+/*
+** Read from the database file.
+*/
+static int kvvfsReadDb(
+  sqlite3_file *pProtoFile,
+  void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  KVVfsFile *pFile = (KVVfsFile*)pProtoFile;
+  unsigned int pgno;
+  int got, n;
+  char zKey[30];
+  char aData[133073];
+  assert( iOfst>=0 );
+  assert( iAmt>=0 );
+  SQLITE_KV_LOG(("xRead('%s-db',%d,%lld)\n", pFile->zClass, iAmt, iOfst));
+  if( iOfst+iAmt>=512 ){
+    if( (iOfst % iAmt)!=0 ){
+      return SQLITE_IOERR_READ;
+    }
+    if( (iAmt & (iAmt-1))!=0 || iAmt<512 || iAmt>65536 ){
+      return SQLITE_IOERR_READ;
+    }
+    pFile->szPage = iAmt;
+    pgno = 1 + iOfst/iAmt;
+  }else{
+    pgno = 1;
+  }
+  sqlite3_snprintf(sizeof(zKey), zKey, "%u", pgno);
+  got = sqlite3KvvfsMethods.xRead(pFile->zClass, zKey, aData, sizeof(aData)-1);
+  if( got<0 ){
+    n = 0;
+  }else{
+    aData[got] = 0;
+    if( iOfst+iAmt<512 ){
+      int k = iOfst+iAmt;
+      aData[k*2] = 0;
+      n = kvvfsDecode(aData, &aData[2000], sizeof(aData)-2000);
+      if( n>=iOfst+iAmt ){
+        memcpy(zBuf, &aData[2000+iOfst], iAmt);
+        n = iAmt;
+      }else{
+        n = 0;
+      }
+    }else{
+      n = kvvfsDecode(aData, zBuf, iAmt);
+    }
+  }
+  if( n<iAmt ){
+    memset(zBuf+n, 0, iAmt-n);
+    return SQLITE_IOERR_SHORT_READ;
+  }
+  return SQLITE_OK;
+}
+
+
+/*
+** Write into the -journal file.
+*/
+static int kvvfsWriteJrnl(
+  sqlite3_file *pProtoFile,
+  const void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  KVVfsFile *pFile = (KVVfsFile*)pProtoFile;
+  sqlite3_int64 iEnd = iOfst+iAmt;
+  SQLITE_KV_LOG(("xWrite('%s-journal',%d,%lld)\n", pFile->zClass, iAmt, iOfst));
+  if( iEnd>=0x10000000 ) return SQLITE_FULL;
+  if( pFile->aJrnl==0 || pFile->nJrnl<iEnd ){
+    char *aNew = sqlite3_realloc(pFile->aJrnl, iEnd);
+    if( aNew==0 ){
+      return SQLITE_IOERR_NOMEM;
+    }
+    pFile->aJrnl = aNew;
+    if( pFile->nJrnl<iOfst ){
+      memset(pFile->aJrnl+pFile->nJrnl, 0, iOfst-pFile->nJrnl);
+    }
+    pFile->nJrnl = iEnd;
+  }
+  memcpy(pFile->aJrnl+iOfst, zBuf, iAmt);
+  return SQLITE_OK;
+}
+
+/*
+** Write into the database file.
+*/
+static int kvvfsWriteDb(
+  sqlite3_file *pProtoFile,
+  const void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  KVVfsFile *pFile = (KVVfsFile*)pProtoFile;
+  unsigned int pgno;
+  char zKey[30];
+  char aData[131073];
+  SQLITE_KV_LOG(("xWrite('%s-db',%d,%lld)\n", pFile->zClass, iAmt, iOfst));
+  assert( iAmt>=512 && iAmt<=65536 );
+  assert( (iAmt & (iAmt-1))==0 );
+  assert( pFile->szPage<0 || pFile->szPage==iAmt );
+  pFile->szPage = iAmt;
+  pgno = 1 + iOfst/iAmt;
+  sqlite3_snprintf(sizeof(zKey), zKey, "%u", pgno);
+  kvvfsEncode(zBuf, iAmt, aData);
+  if( sqlite3KvvfsMethods.xWrite(pFile->zClass, zKey, aData) ){
+    return SQLITE_IOERR;
+  }
+  if( iOfst+iAmt > pFile->szDb ){
+    pFile->szDb = iOfst + iAmt;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Truncate an kvvfs-file.
+*/
+static int kvvfsTruncateJrnl(sqlite3_file *pProtoFile, sqlite_int64 size){
+  KVVfsFile *pFile = (KVVfsFile *)pProtoFile;
+  SQLITE_KV_LOG(("xTruncate('%s-journal',%lld)\n", pFile->zClass, size));
+  assert( size==0 );
+  sqlite3KvvfsMethods.xDelete(pFile->zClass, "jrnl");
+  sqlite3_free(pFile->aJrnl);
+  pFile->aJrnl = 0;
+  pFile->nJrnl = 0;
+  return SQLITE_OK;
+}
+static int kvvfsTruncateDb(sqlite3_file *pProtoFile, sqlite_int64 size){
+  KVVfsFile *pFile = (KVVfsFile *)pProtoFile;
+  if( pFile->szDb>size
+   && pFile->szPage>0 
+   && (size % pFile->szPage)==0
+  ){
+    char zKey[50];
+    unsigned int pgno, pgnoMax;
+    SQLITE_KV_LOG(("xTruncate('%s-db',%lld)\n", pFile->zClass, size));
+    pgno = 1 + size/pFile->szPage;
+    pgnoMax = 2 + pFile->szDb/pFile->szPage;
+    while( pgno<=pgnoMax ){
+      sqlite3_snprintf(sizeof(zKey), zKey, "%u", pgno);
+      sqlite3KvvfsMethods.xDelete(pFile->zClass, zKey);
+      pgno++;
+    }
+    pFile->szDb = size;
+    return kvvfsWriteFileSize(pFile, size) ? SQLITE_IOERR : SQLITE_OK;
+  }
+  return SQLITE_IOERR;
+}
+
+/*
+** Sync an kvvfs-file.
+*/
+static int kvvfsSyncJrnl(sqlite3_file *pProtoFile, int flags){
+  int i, n;
+  KVVfsFile *pFile = (KVVfsFile *)pProtoFile;
+  char *zOut;
+  SQLITE_KV_LOG(("xSync('%s-journal')\n", pFile->zClass));
+  if( pFile->nJrnl<=0 ){
+    return kvvfsTruncateJrnl(pProtoFile, 0);
+  }
+  zOut = sqlite3_malloc64( pFile->nJrnl*2 + 50 );
+  if( zOut==0 ){
+    return SQLITE_IOERR_NOMEM;
+  }
+  n = pFile->nJrnl;
+  i = 0;
+  do{
+    zOut[i++] = 'a' + (n%26);
+    n /= 26;
+  }while( n>0 );
+  zOut[i++] = ' ';
+  kvvfsEncode(pFile->aJrnl, pFile->nJrnl, &zOut[i]);
+  i = sqlite3KvvfsMethods.xWrite(pFile->zClass, "jrnl", zOut);
+  sqlite3_free(zOut);
+  return i ? SQLITE_IOERR : SQLITE_OK;
+}
+static int kvvfsSyncDb(sqlite3_file *pProtoFile, int flags){
+  return SQLITE_OK;
+}
+
+/*
+** Return the current file-size of an kvvfs-file.
+*/
+static int kvvfsFileSizeJrnl(sqlite3_file *pProtoFile, sqlite_int64 *pSize){
+  KVVfsFile *pFile = (KVVfsFile *)pProtoFile;
+  SQLITE_KV_LOG(("xFileSize('%s-journal')\n", pFile->zClass));
+  *pSize = pFile->nJrnl;
+  return SQLITE_OK;
+}
+static int kvvfsFileSizeDb(sqlite3_file *pProtoFile, sqlite_int64 *pSize){
+  KVVfsFile *pFile = (KVVfsFile *)pProtoFile;
+  SQLITE_KV_LOG(("xFileSize('%s-db')\n", pFile->zClass));
+  if( pFile->szDb>=0 ){
+    *pSize = pFile->szDb;
+  }else{
+    *pSize = kvvfsReadFileSize(pFile);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Lock an kvvfs-file.
+*/
+static int kvvfsLock(sqlite3_file *pProtoFile, int eLock){
+  KVVfsFile *pFile = (KVVfsFile *)pProtoFile;
+  assert( !pFile->isJournal );
+  SQLITE_KV_LOG(("xLock(%s,%d)\n", pFile->zClass, eLock));
+
+  if( eLock!=SQLITE_LOCK_NONE ){
+    pFile->szDb = kvvfsReadFileSize(pFile);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Unlock an kvvfs-file.
+*/
+static int kvvfsUnlock(sqlite3_file *pProtoFile, int eLock){
+  KVVfsFile *pFile = (KVVfsFile *)pProtoFile;
+  assert( !pFile->isJournal );
+  SQLITE_KV_LOG(("xUnlock(%s,%d)\n", pFile->zClass, eLock));
+  if( eLock==SQLITE_LOCK_NONE ){
+    pFile->szDb = -1;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Check if another file-handle holds a RESERVED lock on an kvvfs-file.
+*/
+static int kvvfsCheckReservedLock(sqlite3_file *pProtoFile, int *pResOut){
+  SQLITE_KV_LOG(("xCheckReservedLock\n"));
+  *pResOut = 0;
+  return SQLITE_OK;
+}
+
+/*
+** File control method. For custom operations on an kvvfs-file.
+*/
+static int kvvfsFileControlJrnl(sqlite3_file *pProtoFile, int op, void *pArg){
+  SQLITE_KV_LOG(("xFileControl(%d) on journal\n", op));
+  return SQLITE_NOTFOUND;
+}
+static int kvvfsFileControlDb(sqlite3_file *pProtoFile, int op, void *pArg){
+  SQLITE_KV_LOG(("xFileControl(%d) on database\n", op));
+  if( op==SQLITE_FCNTL_SYNC ){
+    KVVfsFile *pFile = (KVVfsFile *)pProtoFile;
+    int rc = SQLITE_OK;
+    SQLITE_KV_LOG(("xSync('%s-db')\n", pFile->zClass));
+    if( pFile->szDb>0 && 0!=kvvfsWriteFileSize(pFile, pFile->szDb) ){
+      rc = SQLITE_IOERR;
+    }
+    return rc;
+  }
+  return SQLITE_NOTFOUND;
+}
+
+/*
+** Return the sector-size in bytes for an kvvfs-file.
+*/
+static int kvvfsSectorSize(sqlite3_file *pFile){
+  return 512;
+}
+
+/*
+** Return the device characteristic flags supported by an kvvfs-file.
+*/
+static int kvvfsDeviceCharacteristics(sqlite3_file *pProtoFile){
+  return 0;
+}
+
+/****** sqlite3_vfs methods *************************************************/
+
+/*
+** Open an kvvfs file handle.
+*/
+static int kvvfsOpen(
+  sqlite3_vfs *pProtoVfs,
+  const char *zName,
+  sqlite3_file *pProtoFile,
+  int flags,
+  int *pOutFlags
+){
+  KVVfsFile *pFile = (KVVfsFile*)pProtoFile;
+  if( zName==0 ) zName = "";
+  SQLITE_KV_LOG(("xOpen(\"%s\")\n", zName));
+  if( strcmp(zName, "local")==0
+   || strcmp(zName, "session")==0
+  ){
+    pFile->isJournal = 0;
+    pFile->base.pMethods = &kvvfs_db_io_methods;
+  }else
+  if( strcmp(zName, "local-journal")==0 
+   || strcmp(zName, "session-journal")==0
+  ){
+    pFile->isJournal = 1;
+    pFile->base.pMethods = &kvvfs_jrnl_io_methods;
+  }else{
+    return SQLITE_CANTOPEN;
+  }
+  if( zName[0]=='s' ){
+    pFile->zClass = "session";
+  }else{
+    pFile->zClass = "local";
+  }
+  pFile->aJrnl = 0;
+  pFile->nJrnl = 0;
+  pFile->szPage = -1;
+  pFile->szDb = -1;
+  return SQLITE_OK;
+}
+
+/*
+** Delete the file located at zPath. If the dirSync argument is true,
+** ensure the file-system modifications are synced to disk before
+** returning.
+*/
+static int kvvfsDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
+  if( strcmp(zPath, "local-journal")==0 ){
+    sqlite3KvvfsMethods.xDelete("local", "jrnl");
+  }else
+  if( strcmp(zPath, "session-journal")==0 ){
+    sqlite3KvvfsMethods.xDelete("session", "jrnl");
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Test for access permissions. Return true if the requested permission
+** is available, or false otherwise.
+*/
+static int kvvfsAccess(
+  sqlite3_vfs *pProtoVfs, 
+  const char *zPath, 
+  int flags, 
+  int *pResOut
+){
+  SQLITE_KV_LOG(("xAccess(\"%s\")\n", zPath));
+  if( strcmp(zPath, "local-journal")==0 ){
+    *pResOut = sqlite3KvvfsMethods.xRead("local", "jrnl", 0, 0)>0;
+  }else
+  if( strcmp(zPath, "session-journal")==0 ){
+    *pResOut = sqlite3KvvfsMethods.xRead("session", "jrnl", 0, 0)>0;
+  }else
+  if( strcmp(zPath, "local")==0 ){
+    *pResOut = sqlite3KvvfsMethods.xRead("local", "sz", 0, 0)>0;
+  }else
+  if( strcmp(zPath, "session")==0 ){
+    *pResOut = sqlite3KvvfsMethods.xRead("session", "sz", 0, 0)>0;
+  }else
+  {
+    *pResOut = 0;
+  }
+  SQLITE_KV_LOG(("xAccess returns %d\n",*pResOut));
+  return SQLITE_OK;
+}
+
+/*
+** Populate buffer zOut with the full canonical pathname corresponding
+** to the pathname in zPath. zOut is guaranteed to point to a buffer
+** of at least (INST_MAX_PATHNAME+1) bytes.
+*/
+static int kvvfsFullPathname(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int nOut, 
+  char *zOut
+){
+  size_t nPath;
+#ifdef SQLITE_OS_KV_ALWAYS_LOCAL
+  zPath = "local";
+#endif
+  nPath = strlen(zPath);
+  SQLITE_KV_LOG(("xFullPathname(\"%s\")\n", zPath));
+  if( nOut<nPath+1 ) nPath = nOut - 1;
+  memcpy(zOut, zPath, nPath);
+  zOut[nPath] = 0;
+  return SQLITE_OK;
+}
+
+/*
+** Open the dynamic library located at zPath and return a handle.
+*/
+static void *kvvfsDlOpen(sqlite3_vfs *pVfs, const char *zPath){
+  return 0;
+}
+
+/*
+** Populate the buffer pointed to by zBufOut with nByte bytes of 
+** random data.
+*/
+static int kvvfsRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
+  memset(zBufOut, 0, nByte);
+  return nByte;
+}
+
+/*
+** Sleep for nMicro microseconds. Return the number of microseconds 
+** actually slept.
+*/
+static int kvvfsSleep(sqlite3_vfs *pVfs, int nMicro){
+  return SQLITE_OK;
+}
+
+/*
+** Return the current time as a Julian Day number in *pTimeOut.
+*/
+static int kvvfsCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
+  sqlite3_int64 i = 0;
+  int rc;
+  rc = kvvfsCurrentTimeInt64(0, &i);
+  *pTimeOut = i/86400000.0;
+  return rc;
+}
+#include <sys/time.h>
+static int kvvfsCurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *pTimeOut){
+  static const sqlite3_int64 unixEpoch = 24405875*(sqlite3_int64)8640000;
+  struct timeval sNow;
+  (void)gettimeofday(&sNow, 0);  /* Cannot fail given valid arguments */
+  *pTimeOut = unixEpoch + 1000*(sqlite3_int64)sNow.tv_sec + sNow.tv_usec/1000;
+  return SQLITE_OK;
+}
+#endif /* SQLITE_OS_KV || SQLITE_OS_UNIX */
+
+#if SQLITE_OS_KV
+/* 
+** This routine is called initialize the KV-vfs as the default VFS.
+*/
+int sqlite3_os_init(void){
+  return sqlite3_vfs_register(&sqlite3OsKvvfsObject, 1);
+}
+int sqlite3_os_end(void){
+  return SQLITE_OK;
+}
+#endif /* SQLITE_OS_KV */
+
+#if SQLITE_OS_UNIX && defined(SQLITE_OS_KV_OPTIONAL)
+int sqlite3KvvfsInit(void){
+  return sqlite3_vfs_register(&sqlite3OsKvvfsObject, 0);
+}
+#endif