Add the SQLITE_FCNTL_SYNC and SQLITE_FCNTL_COMMIT_PHASETWO file-controls

and have the pager call them at appropriate times.  This is needed in order
to enable ZIPVFS to do multi-file atomic commits.

FossilOrigin-Name: 552f94d50f08cf11f33205730fde52bc2f06cff6

5 files changed, 52 insertions, 29 deletions

diff --git a/src/backup.c b/src/backup.c
index 1bac821f3..292f3f456 100644
--- a/src/backup.c
+++ b/src/backup.c
@@ -526,7 +526,7 @@ int sqlite3_backup_step(sqlite3_backup *p, int nPage){
 
           /* Sync the database file to disk. */
           if( rc==SQLITE_OK ){
-            rc = sqlite3PagerSync(pDestPager);
+            rc = sqlite3PagerSync(pDestPager, 0);
           }
         }else{
           sqlite3PagerTruncateImage(pDestPager, nDestTruncate);
diff --git a/src/pager.c b/src/pager.c
index 443a52326..b4988cece 100644
--- a/src/pager.c
+++ b/src/pager.c
@@ -1249,6 +1249,7 @@ static int readMasterJournal(sqlite3_file *pJrnl, char *zMaster, u32 nMaster){
    || szJ<16
    || SQLITE_OK!=(rc = read32bits(pJrnl, szJ-16, &len))
    || len>=nMaster 
+   || len==0 
    || SQLITE_OK!=(rc = read32bits(pJrnl, szJ-12, &cksum))
    || SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, aMagic, 8, szJ-8))
    || memcmp(aMagic, aJournalMagic, 8)
@@ -2018,6 +2019,11 @@ static int pager_end_transaction(Pager *pPager, int hasMaster, int bCommit){
     rc = pager_truncate(pPager, pPager->dbSize);
   }
 
+  if( rc==SQLITE_OK && bCommit && isOpen(pPager->fd) ){
+    rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_COMMIT_PHASETWO, 0);
+    if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK;
+  }
+
   if( !pPager->exclusiveMode 
    && (!pagerUseWal(pPager) || sqlite3WalExclusiveMode(pPager->pWal, 0))
   ){
@@ -2831,7 +2837,7 @@ end_playback:
   if( rc==SQLITE_OK
    && (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN)
   ){
-    rc = sqlite3PagerSync(pPager);
+    rc = sqlite3PagerSync(pPager, 0);
   }
   if( rc==SQLITE_OK ){
     rc = pager_end_transaction(pPager, zMaster[0]!='\0', 0);
@@ -6000,17 +6006,17 @@ static int pager_incr_changecounter(Pager *pPager, int isDirectMode){
 ** If successful, or if called on a pager for which it is a no-op, this
 ** function returns SQLITE_OK. Otherwise, an IO error code is returned.
 */
-int sqlite3PagerSync(Pager *pPager){
+int sqlite3PagerSync(Pager *pPager, const char *zMaster){
   int rc = SQLITE_OK;
-  if( !pPager->noSync ){
+
+  if( isOpen(pPager->fd) ){
+    void *pArg = (void*)zMaster;
+    rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_SYNC, pArg);
+    if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK;
+  }
+  if( rc==SQLITE_OK && !pPager->noSync ){
     assert( !MEMDB );
     rc = sqlite3OsSync(pPager->fd, pPager->syncFlags);
-  }else if( isOpen(pPager->fd) ){
-    assert( !MEMDB );
-    rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_SYNC_OMITTED, 0);
-    if( rc==SQLITE_NOTFOUND ){
-      rc = SQLITE_OK;
-    }
   }
   return rc;
 }
@@ -6209,7 +6215,7 @@ int sqlite3PagerCommitPhaseOne(
   
       /* Finally, sync the database file. */
       if( !noSync ){
-        rc = sqlite3PagerSync(pPager);
+        rc = sqlite3PagerSync(pPager, zMaster);
       }
       IOTRACE(("DBSYNC %p\n", pPager))
     }
@@ -6338,7 +6344,9 @@ int sqlite3PagerRollback(Pager *pPager){
 
   assert( pPager->eState==PAGER_READER || rc!=SQLITE_OK );
   assert( rc==SQLITE_OK || rc==SQLITE_FULL || rc==SQLITE_CORRUPT
-          || rc==SQLITE_NOMEM || (rc&0xFF)==SQLITE_IOERR );
+          || rc==SQLITE_NOMEM || (rc&0xFF)==SQLITE_IOERR 
+          || rc==SQLITE_CANTOPEN
+  );
 
   /* If an error occurs during a ROLLBACK, we can no longer trust the pager
   ** cache. So call pager_error() on the way out to make any error persistent.
diff --git a/src/pager.h b/src/pager.h
index 7851d2834..55988a848 100644
--- a/src/pager.h
+++ b/src/pager.h
@@ -150,7 +150,7 @@ void sqlite3PagerPagecount(Pager*, int*);
 int sqlite3PagerBegin(Pager*, int exFlag, int);
 int sqlite3PagerCommitPhaseOne(Pager*,const char *zMaster, int);
 int sqlite3PagerExclusiveLock(Pager*);
-int sqlite3PagerSync(Pager *pPager);
+int sqlite3PagerSync(Pager *pPager, const char *zMaster);
 int sqlite3PagerCommitPhaseTwo(Pager*);
 int sqlite3PagerRollback(Pager*);
 int sqlite3PagerOpenSavepoint(Pager *pPager, int n);
diff --git a/src/sqlite.h.in b/src/sqlite.h.in
index 1ad181e74..b9f4defed 100644
--- a/src/sqlite.h.in
+++ b/src/sqlite.h.in
@@ -786,15 +786,29 @@ struct sqlite3_io_methods {
 ** additional information.
 **
 ** <li>[[SQLITE_FCNTL_SYNC_OMITTED]]
-** ^(The [SQLITE_FCNTL_SYNC_OMITTED] opcode is generated internally by
-** SQLite and sent to all VFSes in place of a call to the xSync method
-** when the database connection has [PRAGMA synchronous] set to OFF.)^
-** Some specialized VFSes need this signal in order to operate correctly
-** when [PRAGMA synchronous | PRAGMA synchronous=OFF] is set, but most 
-** VFSes do not need this signal and should silently ignore this opcode.
-** Applications should not call [sqlite3_file_control()] with this
-** opcode as doing so may disrupt the operation of the specialized VFSes
-** that do require it.  
+** No longer in use.
+**
+** <li>[[SQLITE_FCNTL_SYNC]]
+** The [SQLITE_FCNTL_SYNC] opcode is generated internally by SQLite and
+** sent to the VFS immediately before the xSync method is invoked on a
+** database file descriptor. Or, if the xSync method is not invoked 
+** because the user has configured SQLite with 
+** [PRAGMA synchronous | PRAGMA synchronous=OFF] it is invoked in place 
+** of the xSync method. In most cases, the pointer argument passed with
+** this file-control is NULL. However, if the database file is being synced
+** as part of a multi-database commit, the argument points to a nul-terminated
+** string containing the transactions master-journal file name. VFSes that 
+** do not need this signal should silently ignore this opcode. Applications 
+** should not call [sqlite3_file_control()] with this opcode as doing so may 
+** disrupt the operation of the specialized VFSes that do require it.  
+**
+** <li>[[SQLITE_FCNTL_COMMIT_PHASETWO]]
+** The [SQLITE_FCNTL_COMMIT_PHASETWO] opcode is generated internally by SQLite
+** and sent to the VFS after a transaction has been committed immediately
+** but before the database is unlocked. VFSes that do not need this signal
+** should silently ignore this opcode. Applications should not call
+** [sqlite3_file_control()] with this opcode as doing so may disrupt the 
+** operation of the specialized VFSes that do require it.  
 **
 ** <li>[[SQLITE_FCNTL_WIN32_AV_RETRY]]
 ** ^The [SQLITE_FCNTL_WIN32_AV_RETRY] opcode is used to configure automatic
@@ -945,6 +959,8 @@ struct sqlite3_io_methods {
 #define SQLITE_FCNTL_MMAP_SIZE              18
 #define SQLITE_FCNTL_TRACE                  19
 #define SQLITE_FCNTL_HAS_MOVED              20
+#define SQLITE_FCNTL_SYNC                   21
+#define SQLITE_FCNTL_COMMIT_PHASETWO        22
 
 /*
 ** CAPI3REF: Mutex Handle
diff --git a/src/test6.c b/src/test6.c
index 6ea03b0f1..306482dcd 100644
--- a/src/test6.c
+++ b/src/test6.c
@@ -173,9 +173,6 @@ static void *crash_realloc(void *p, int n){
 static int writeDbFile(CrashFile *p, u8 *z, i64 iAmt, i64 iOff){
   int rc = SQLITE_OK;
   int iSkip = 0;
-  if( iOff==PENDING_BYTE && (p->flags&SQLITE_OPEN_MAIN_DB) ){
-    iSkip = 512;
-  }
   if( (iAmt-iSkip)>0 ){
     rc = sqlite3OsWrite(p->pRealFile, &z[iSkip], (int)(iAmt-iSkip), iOff+iSkip);
   }
@@ -409,13 +406,17 @@ static int cfRead(
   sqlite_int64 iOfst
 ){
   CrashFile *pCrash = (CrashFile *)pFile;
+  int nCopy = (int)MIN((i64)iAmt, (pCrash->iSize - iOfst));
+
+  if( nCopy>0 ){
+    memcpy(zBuf, &pCrash->zData[iOfst], nCopy);
+  }
 
   /* Check the file-size to see if this is a short-read */
-  if( pCrash->iSize<(iOfst+iAmt) ){
+  if( nCopy<iAmt ){
     return SQLITE_IOERR_SHORT_READ;
   }
 
-  memcpy(zBuf, &pCrash->zData[iOfst], iAmt);
   return SQLITE_OK;
 }
 
@@ -632,14 +633,12 @@ static int cfOpen(
       ** UPDATE: It also contains an assert() verifying that each call
       ** to the xRead() method reads less than 128KB of data.
       */
-      const int isDb = (flags&SQLITE_OPEN_MAIN_DB);
       i64 iOff;
 
       memset(pWrapper->zData, 0, pWrapper->nData);
       for(iOff=0; iOff<pWrapper->iSize; iOff += 512){
         int nRead = (int)(pWrapper->iSize - iOff);
         if( nRead>512 ) nRead = 512;
-        if( isDb && iOff==PENDING_BYTE ) continue;
         rc = sqlite3OsRead(pReal, &pWrapper->zData[iOff], nRead, iOff);
       }
     }else{