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Revise the layout of filenames in the Pager object so that it is unchanged

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from prior versions.  It turns out that some important 3rd-party software
does questionable pointer manipulations on those filenames that depend on
that legacy layout.  Technical this is a misuse of SQLite by the 3rd-party
software, but we want to avoid unnecessary breakage.

FossilOrigin-Name: 34ab760689fd493eda482e856047708d74e769a01cc90b69da456d79ffe39aea
This commit is contained in:
drh
2020-01-27 14:40:44 +00:00
parent 9a3bdeba3e
commit 532b0d23fd
4 changed files with 86 additions and 61 deletions
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77
src/pager.c
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@@ -4838,30 +4838,48 @@ int sqlite3PagerOpen(
** Database file handle (pVfs->szOsFile bytes)
** Sub-journal file handle (journalFileSize bytes)
** Main journal file handle (journalFileSize bytes)
** \0\1\0 journal prefix (3 bytes)
** Journal filename (nPathname+8+1 bytes)
** \2\0 WAL prefix (2 bytes)
** WAL filename (nPathname+4+1 bytes)
** \3\0 database prefix (2 bytes)
** \0\0\0\0 database prefix (4 bytes)
** Database file name (nPathname+1 bytes)
** URI query parameters (nUriByte bytes)
** \0\0 terminator (2 bytes)
** Journal filename (nPathname+8+1 bytes)
** WAL filename (nPathname+4+1 bytes)
** \0\0\0 terminator (3 bytes)
**
** Some 3rd-party software, over which we have no control, depends on
** the specific order of the filenames and the \0 separators between them
** so that it can (for example) find the database filename given the WAL
** filename without using the sqlite3_filename_database() API. This is a
** misuse of SQLite and a bug in the 3rd-party software, but the 3rd-party
** software is in widespread use, so we try to avoid changing the filename
** order and formatting if possible. In particular, the details of the
** filename format expected by 3rd-party software should be as follows:
**
** - Main Database Path
** - \0
** - Multiple URI components consisting of:
** - Key
** - \0
** - Value
** - \0
** - \0
** - Journal Path
** - \0
** - WAL Path (zWALName)
** - \0
*/
pPtr = (u8 *)sqlite3MallocZero(
ROUND8(sizeof(*pPager)) + /* Pager structure */
ROUND8(pcacheSize) + /* PCache object */
ROUND8(pVfs->szOsFile) + /* The main db file */
journalFileSize * 2 + /* The two journal files */
3 + /* Journal prefix */
nPathname + 8 + 1 + /* Journal filename */
#ifndef SQLITE_OMIT_WAL
2 + /* WAL prefix */
nPathname + 4 + 1 + /* WAL filename */
#endif
2 + /* Database prefix */
4 + /* Database prefix */
nPathname + 1 + /* database filename */
nUriByte + /* query parameters */
2 /* Terminator */
nPathname + 8 + 1 + /* Journal filename */
#ifndef SQLITE_OMIT_WAL
nPathname + 4 + 1 + /* WAL filename */
#endif
3 /* Terminator */
);
assert( EIGHT_BYTE_ALIGNMENT(SQLITE_INT_TO_PTR(journalFileSize)) );
if( !pPtr ){
@@ -4875,9 +4893,20 @@ int sqlite3PagerOpen(
pPager->jfd = (sqlite3_file*)pPtr; pPtr += journalFileSize;
assert( EIGHT_BYTE_ALIGNMENT(pPager->jfd) );
/* Fill in the Pager.zFilename and pPager.zQueryParam fields */
pPtr += 4; /* Skip zero prefix */
pPager->zFilename = (char*)pPtr;
if( nPathname>0 ){
memcpy(pPtr, zPathname, nPathname); pPtr += nPathname + 1;
if( zUri ){
memcpy(pPtr, zUri, nUriByte); pPtr += nUriByte;
}else{
pPtr++;
}
}
/* Fill in Pager.zJournal */
pPtr[1] = '\001'; pPtr += 3;
if( nPathname>0 ){
pPager->zJournal = (char*)pPtr;
memcpy(pPtr, zPathname, nPathname); pPtr += nPathname;
@@ -4888,12 +4917,10 @@ int sqlite3PagerOpen(
#endif
}else{
pPager->zJournal = 0;
pPtr++;
}
#ifndef SQLITE_OMIT_WAL
/* Fill in Pager.zWal */
pPtr[0] = '\002'; pPtr[1] = 0; pPtr += 2;
if( nPathname>0 ){
pPager->zWal = (char*)pPtr;
memcpy(pPtr, zPathname, nPathname); pPtr += nPathname;
@@ -4904,21 +4931,9 @@ int sqlite3PagerOpen(
#endif
}else{
pPager->zWal = 0;
pPtr++;
}
#endif
/* Fill in the Pager.zFilename and pPager.zQueryParam fields */
pPtr[0] = '\003'; pPtr[1] = 0; pPtr += 2;
pPager->zFilename = (char*)pPtr;
if( nPathname>0 ){
memcpy(pPtr, zPathname, nPathname); pPtr += nPathname + 1;
if( zUri ){
memcpy(pPtr, zUri, nUriByte); /* pPtr += nUriByte; // not needed */
}
/* Double-zero terminator implied by the sqlite3MallocZero */
}
if( nPathname ) sqlite3DbFree(0, zPathname);
pPager->pVfs = pVfs;
pPager->vfsFlags = vfsFlags;
@@ -7038,8 +7053,8 @@ int sqlite3PagerSavepoint(Pager *pPager, int op, int iSavepoint){
** sqlite3_uri_parameter() and sqlite3_filename_database() and friends.
*/
const char *sqlite3PagerFilename(const Pager *pPager, int nullIfMemDb){
static const char zFake[] = { 0x00, 0x01, 0x00, 0x00, 0x00 };
return (nullIfMemDb && pPager->memDb) ? &zFake[3] : pPager->zFilename;
static const char zFake[] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
return (nullIfMemDb && pPager->memDb) ? &zFake[4] : pPager->zFilename;
}
/*