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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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54
src/main.c
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@@ -4243,6 +4243,21 @@ int sqlite3_test_control(int op, ...){
return rc;
}
/*
** The Pager stores the Database filename, Journal filename, and WAL filename
** consecutively in memory, in that order. The database filename is prefixed
** by four zero bytes. Locate the start of the database filename by searching
** backwards for the first byte following four consecutive zero bytes.
**
** This only works if the filename passed in was obtained from the Pager.
*/
static const char *databaseName(const char *zName){
while( zName[-1]!=0 || zName[-2]!=0 || zName[-3]!=0 || zName[-4]!=0 ){
zName--;
}
return zName;
}
/*
** This is a utility routine, useful to VFS implementations, that checks
** to see if a database file was a URI that contained a specific query
@@ -4256,6 +4271,7 @@ int sqlite3_test_control(int op, ...){
*/
const char *sqlite3_uri_parameter(const char *zFilename, const char *zParam){
if( zFilename==0 || zParam==0 ) return 0;
zFilename = databaseName(zFilename);
zFilename += sqlite3Strlen30(zFilename) + 1;
while( zFilename[0] ){
int x = strcmp(zFilename, zParam);
@@ -4271,6 +4287,7 @@ const char *sqlite3_uri_parameter(const char *zFilename, const char *zParam){
*/
const char *sqlite3_uri_key(const char *zFilename, int N){
if( zFilename==0 || N<0 ) return 0;
zFilename = databaseName(zFilename);
zFilename += sqlite3Strlen30(zFilename) + 1;
while( zFilename[0] && (N--)>0 ){
zFilename += sqlite3Strlen30(zFilename) + 1;
@@ -4304,25 +4321,6 @@ sqlite3_int64 sqlite3_uri_int64(
return bDflt;
}
/*
** The Pager stores the Journal filename, WAL filename, and Database filename
** consecutively in memory, in that order, with prefixes \000\001\000,
** \002\000, and \003\000, in that order. Thus the three names look like query
** parameters if you start at the first prefix.
**
** This routine backs up a filename to the start of the first prefix.
**
** This only works if the filenamed passed in was obtained from the Pager.
*/
static const char *startOfNameList(const char *zName){
while( zName[0]!='\001' || zName[1]!=0 ){
zName -= 3;
while( zName[0]!='\000' ){ zName--; }
zName++;
}
return zName-1;
}
/*
** Translate a filename that was handed to a VFS routine into the corresponding
** database, journal, or WAL file.
@@ -4334,14 +4332,26 @@ static const char *startOfNameList(const char *zName){
** corruption.
*/
const char *sqlite3_filename_database(const char *zFilename){
return databaseName(zFilename);
return sqlite3_uri_parameter(zFilename - 3, "\003");
}
const char *sqlite3_filename_journal(const char *zFilename){
const char *z = sqlite3_uri_parameter(startOfNameList(zFilename), "\001");
return ALWAYS(z) && z[0] ? z : 0;
zFilename = databaseName(zFilename);
zFilename += sqlite3Strlen30(zFilename) + 1;
while( zFilename[0] ){
zFilename += sqlite3Strlen30(zFilename) + 1;
zFilename += sqlite3Strlen30(zFilename) + 1;
}
return zFilename + 1;
}
const char *sqlite3_filename_wal(const char *zFilename){
return sqlite3_uri_parameter(startOfNameList(zFilename), "\002");
#ifdef SQLITE_OMIT_WAL
return 0;
#else
zFilename = sqlite3_filename_journal(zFilename);
zFilename += sqlite3Strlen30(zFilename) + 1;
return zFilename;
#endif
}
/*