[sql] Import SQLite 3.17.0.

third_party/sqlite/src/src/memjournal.c

 /*
 ** 2008 October 7
 **
 ** 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 code use to implement an in-memory rollback journal.
 ** The in-memory rollback journal is used to journal transactions for
 ** ":memory:" databases and when the journal_mode=MEMORY pragma is used.
+**
+** Update:  The in-memory journal is also used to temporarily cache
+** smaller journals that are not critical for power-loss recovery.
+** For example, statement journals that are not too big will be held
+** entirely in memory, thus reducing the number of file I/O calls, and
+** more importantly, reducing temporary file creation events.  If these
+** journals become too large for memory, they are spilled to disk.  But
+** in the common case, they are usually small and no file I/O needs to
+** occur.
 */
 #include "sqliteInt.h"
 
 /* Forward references to internal structures */
 typedef struct MemJournal MemJournal;
 typedef struct FilePoint FilePoint;
 typedef struct FileChunk FileChunk;
 
-/* Space to hold the rollback journal is allocated in increments of
-** this many bytes.
-**
-** The size chosen is a little less than a power of two.  That way,
-** the FileChunk object will have a size that almost exactly fills
-** a power-of-two allocation.  This minimizes wasted space in power-of-two
-** memory allocators.
-*/
-#define JOURNAL_CHUNKSIZE ((int)(1024-sizeof(FileChunk*)))
-
 /*
 ** The rollback journal is composed of a linked list of these structures.
+**
+** The zChunk array is always at least 8 bytes in size - usually much more.
+** Its actual size is stored in the MemJournal.nChunkSize variable.
 */
 struct FileChunk {
   FileChunk *pNext;               /* Next chunk in the journal */
-  u8 zChunk[JOURNAL_CHUNKSIZE];   /* Content of this chunk */
+  u8 zChunk[8];                   /* Content of this chunk */
 };
 
 /*
+** By default, allocate this many bytes of memory for each FileChunk object.
+*/
+#define MEMJOURNAL_DFLT_FILECHUNKSIZE 1024
+
+/*
+** For chunk size nChunkSize, return the number of bytes that should
+** be allocated for each FileChunk structure.
+*/
+#define fileChunkSize(nChunkSize) (sizeof(FileChunk) + ((nChunkSize)-8))
+
+/*
 ** An instance of this object serves as a cursor into the rollback journal.
 ** The cursor can be either for reading or writing.
 */
 struct FilePoint {
   sqlite3_int64 iOffset;          /* Offset from the beginning of the file */
   FileChunk *pChunk;              /* Specific chunk into which cursor points */
 };
 
 /*
-** This subclass is a subclass of sqlite3_file.  Each open memory-journal
+** This structure is a subclass of sqlite3_file. Each open memory-journal
 ** is an instance of this class.
 */
 struct MemJournal {
-  sqlite3_io_methods *pMethod;    /* Parent class. MUST BE FIRST */
+  const sqlite3_io_methods *pMethod; /* Parent class. MUST BE FIRST */
+  int nChunkSize;                 /* In-memory chunk-size */
+
+  int nSpill;                     /* Bytes of data before flushing */
+  int nSize;                      /* Bytes of data currently in memory */
   FileChunk *pFirst;              /* Head of in-memory chunk-list */
   FilePoint endpoint;             /* Pointer to the end of the file */
   FilePoint readpoint;            /* Pointer to the end of the last xRead() */
+
+  int flags;                      /* xOpen flags */
+  sqlite3_vfs *pVfs;              /* The "real" underlying VFS */
+  const char *zJournal;           /* Name of the journal file */
 };
 
 /*
 ** Read data from the in-memory journal file.  This is the implementation
 ** of the sqlite3_vfs.xRead method.
 */
 static int memjrnlRead(
   sqlite3_file *pJfd,    /* The journal file from which to read */
   void *zBuf,            /* Put the results here */
   int iAmt,              /* Number of bytes to read */
   sqlite_int64 iOfst     /* Begin reading at this offset */
 ){
   MemJournal *p = (MemJournal *)pJfd;
   u8 *zOut = zBuf;
   int nRead = iAmt;
   int iChunkOffset;
   FileChunk *pChunk;
 
-  /* SQLite never tries to read past the end of a rollback journal file */
-  assert( iOfst+iAmt<=p->endpoint.iOffset );
+#ifdef SQLITE_ENABLE_ATOMIC_WRITE
+  if( (iAmt+iOfst)>p->endpoint.iOffset ){
+    return SQLITE_IOERR_SHORT_READ;
+  }
+#endif
 
+  assert( (iAmt+iOfst)<=p->endpoint.iOffset );
+  assert( p->readpoint.iOffset==0 || p->readpoint.pChunk!=0 );
   if( p->readpoint.iOffset!=iOfst || iOfst==0 ){
     sqlite3_int64 iOff = 0;
     for(pChunk=p->pFirst; 
-        ALWAYS(pChunk) && (iOff+JOURNAL_CHUNKSIZE)<=iOfst;
+        ALWAYS(pChunk) && (iOff+p->nChunkSize)<=iOfst;
         pChunk=pChunk->pNext
     ){
-      iOff += JOURNAL_CHUNKSIZE;
+      iOff += p->nChunkSize;
     }
   }else{
     pChunk = p->readpoint.pChunk;
+    assert( pChunk!=0 );
   }
 
-  iChunkOffset = (int)(iOfst%JOURNAL_CHUNKSIZE);
+  iChunkOffset = (int)(iOfst%p->nChunkSize);
   do {
-    int iSpace = JOURNAL_CHUNKSIZE - iChunkOffset;
-    int nCopy = MIN(nRead, (JOURNAL_CHUNKSIZE - iChunkOffset));
-    memcpy(zOut, &pChunk->zChunk[iChunkOffset], nCopy);
+    int iSpace = p->nChunkSize - iChunkOffset;
+    int nCopy = MIN(nRead, (p->nChunkSize - iChunkOffset));
+    memcpy(zOut, (u8*)pChunk->zChunk + iChunkOffset, nCopy);
     zOut += nCopy;
     nRead -= iSpace;
     iChunkOffset = 0;
   } while( nRead>=0 && (pChunk=pChunk->pNext)!=0 && nRead>0 );
-  p->readpoint.iOffset = iOfst+iAmt;
+  p->readpoint.iOffset = pChunk ? iOfst+iAmt : 0;
   p->readpoint.pChunk = pChunk;
 
   return SQLITE_OK;
 }
 
 /*
+** Free the list of FileChunk structures headed at MemJournal.pFirst.
+*/
+static void memjrnlFreeChunks(MemJournal *p){
+  FileChunk *pIter;
+  FileChunk *pNext;
+  for(pIter=p->pFirst; pIter; pIter=pNext){
+    pNext = pIter->pNext;
+    sqlite3_free(pIter);
+  } 
+  p->pFirst = 0;
+}
+
+/*
+** Flush the contents of memory to a real file on disk.
+*/
+static int memjrnlCreateFile(MemJournal *p){
+  int rc;
+  sqlite3_file *pReal = (sqlite3_file*)p;
+  MemJournal copy = *p;
+
+  memset(p, 0, sizeof(MemJournal));
+  rc = sqlite3OsOpen(copy.pVfs, copy.zJournal, pReal, copy.flags, 0);
+  if( rc==SQLITE_OK ){
+    int nChunk = copy.nChunkSize;
+    i64 iOff = 0;
+    FileChunk *pIter;
+    for(pIter=copy.pFirst; pIter; pIter=pIter->pNext){
+      if( iOff + nChunk > copy.endpoint.iOffset ){
+        nChunk = copy.endpoint.iOffset - iOff;
+      }
+      rc = sqlite3OsWrite(pReal, (u8*)pIter->zChunk, nChunk, iOff);
+      if( rc ) break;
+      iOff += nChunk;
+    }
+    if( rc==SQLITE_OK ){
+      /* No error has occurred. Free the in-memory buffers. */
+      memjrnlFreeChunks(&copy);
+    }
+  }
+  if( rc!=SQLITE_OK ){
+    /* If an error occurred while creating or writing to the file, restore
+    ** the original before returning. This way, SQLite uses the in-memory
+    ** journal data to roll back changes made to the internal page-cache
+    ** before this function was called.  */
+    sqlite3OsClose(pReal);
+    *p = copy;
+  }
+  return rc;
+}
+
+
+/*
 ** Write data to the file.
 */
 static int memjrnlWrite(
   sqlite3_file *pJfd,    /* The journal file into which to write */
   const void *zBuf,      /* Take data to be written from here */
   int iAmt,              /* Number of bytes to write */
   sqlite_int64 iOfst     /* Begin writing at this offset into the file */
 ){
   MemJournal *p = (MemJournal *)pJfd;
   int nWrite = iAmt;
   u8 *zWrite = (u8 *)zBuf;
 
-  /* An in-memory journal file should only ever be appended to. Random
-  ** access writes are not required by sqlite.
-  */
-  assert( iOfst==p->endpoint.iOffset );
-  UNUSED_PARAMETER(iOfst);
+  /* If the file should be created now, create it and write the new data
+  ** into the file on disk. */
+  if( p->nSpill>0 && (iAmt+iOfst)>p->nSpill ){
+    int rc = memjrnlCreateFile(p);
+    if( rc==SQLITE_OK ){
+      rc = sqlite3OsWrite(pJfd, zBuf, iAmt, iOfst);
+    }
+    return rc;
+  }
 
-  while( nWrite>0 ){
-    FileChunk *pChunk = p->endpoint.pChunk;
-    int iChunkOffset = (int)(p->endpoint.iOffset%JOURNAL_CHUNKSIZE);
-    int iSpace = MIN(nWrite, JOURNAL_CHUNKSIZE - iChunkOffset);
+  /* If the contents of this write should be stored in memory */
+  else{
+    /* An in-memory journal file should only ever be appended to. Random
+    ** access writes are not required. The only exception to this is when
+    ** the in-memory journal is being used by a connection using the
+    ** atomic-write optimization. In this case the first 28 bytes of the
+    ** journal file may be written as part of committing the transaction. */ 
+    assert( iOfst==p->endpoint.iOffset || iOfst==0 );
+#ifdef SQLITE_ENABLE_ATOMIC_WRITE
+    if( iOfst==0 && p->pFirst ){
+      assert( p->nChunkSize>iAmt );
+      memcpy((u8*)p->pFirst->zChunk, zBuf, iAmt);
+    }else
+#else
+    assert( iOfst>0 || p->pFirst==0 );
+#endif
+    {
+      while( nWrite>0 ){
+        FileChunk *pChunk = p->endpoint.pChunk;
+        int iChunkOffset = (int)(p->endpoint.iOffset%p->nChunkSize);
+        int iSpace = MIN(nWrite, p->nChunkSize - iChunkOffset);
 
-    if( iChunkOffset==0 ){
-      /* New chunk is required to extend the file. */
-      FileChunk *pNew = sqlite3_malloc(sizeof(FileChunk));
-      if( !pNew ){
-        return SQLITE_IOERR_NOMEM;
+        if( iChunkOffset==0 ){
+          /* New chunk is required to extend the file. */
+          FileChunk *pNew = sqlite3_malloc(fileChunkSize(p->nChunkSize));
+          if( !pNew ){
+            return SQLITE_IOERR_NOMEM_BKPT;
+          }
+          pNew->pNext = 0;
+          if( pChunk ){
+            assert( p->pFirst );
+            pChunk->pNext = pNew;
+          }else{
+            assert( !p->pFirst );
+            p->pFirst = pNew;
+          }
+          p->endpoint.pChunk = pNew;
+        }
+
+        memcpy((u8*)p->endpoint.pChunk->zChunk + iChunkOffset, zWrite, iSpace);
+        zWrite += iSpace;
+        nWrite -= iSpace;
+        p->endpoint.iOffset += iSpace;
       }
-      pNew->pNext = 0;
-      if( pChunk ){
-        assert( p->pFirst );
-        pChunk->pNext = pNew;
-      }else{
-        assert( !p->pFirst );
-        p->pFirst = pNew;
-      }
-      p->endpoint.pChunk = pNew;
+      p->nSize = iAmt + iOfst;
     }
-
-    memcpy(&p->endpoint.pChunk->zChunk[iChunkOffset], zWrite, iSpace);
-    zWrite += iSpace;
-    nWrite -= iSpace;
-    p->endpoint.iOffset += iSpace;
   }
 
   return SQLITE_OK;
 }
 
 /*
 ** Truncate the file.
+**
+** If the journal file is already on disk, truncate it there. Or, if it
+** is still in main memory but is being truncated to zero bytes in size,
+** ignore 
 */
 static int memjrnlTruncate(sqlite3_file *pJfd, sqlite_int64 size){
   MemJournal *p = (MemJournal *)pJfd;
-  FileChunk *pChunk;
-  assert(size==0);
-  UNUSED_PARAMETER(size);
-  pChunk = p->pFirst;
-  while( pChunk ){
-    FileChunk *pTmp = pChunk;
-    pChunk = pChunk->pNext;
-    sqlite3_free(pTmp);
+  if( ALWAYS(size==0) ){
+    memjrnlFreeChunks(p);
+    p->nSize = 0;
+    p->endpoint.pChunk = 0;
+    p->endpoint.iOffset = 0;
+    p->readpoint.pChunk = 0;
+    p->readpoint.iOffset = 0;
   }
-  sqlite3MemJournalOpen(pJfd);
   return SQLITE_OK;
 }
 
 /*
 ** Close the file.
 */
 static int memjrnlClose(sqlite3_file *pJfd){
-  memjrnlTruncate(pJfd, 0);
+  MemJournal *p = (MemJournal *)pJfd;
+  memjrnlFreeChunks(p);
   return SQLITE_OK;
 }
 
-
 /*
 ** Sync the file.
 **
-** Syncing an in-memory journal is a no-op.  And, in fact, this routine
-** is never called in a working implementation.  This implementation
-** exists purely as a contingency, in case some malfunction in some other
-** part of SQLite causes Sync to be called by mistake.
+** If the real file has been created, call its xSync method. Otherwise, 
+** syncing an in-memory journal is a no-op. 
 */
-static int memjrnlSync(sqlite3_file *NotUsed, int NotUsed2){
-  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+static int memjrnlSync(sqlite3_file *pJfd, int flags){
+  UNUSED_PARAMETER2(pJfd, flags);
   return SQLITE_OK;
 }
 
 /*
 ** Query the size of the file in bytes.
 */
 static int memjrnlFileSize(sqlite3_file *pJfd, sqlite_int64 *pSize){
   MemJournal *p = (MemJournal *)pJfd;
   *pSize = (sqlite_int64) p->endpoint.iOffset;
   return SQLITE_OK;
@@ skipping 18 matching lines @@
   0,                /* xDeviceCharacteristics */
   0,                /* xShmMap */
   0,                /* xShmLock */
   0,                /* xShmBarrier */
   0,                /* xShmUnmap */
   0,                /* xFetch */
   0                 /* xUnfetch */
 };
 
 /* 
-** Open a journal file.
+** Open a journal file. 
+**
+** The behaviour of the journal file depends on the value of parameter 
+** nSpill. If nSpill is 0, then the journal file is always create and 
+** accessed using the underlying VFS. If nSpill is less than zero, then
+** all content is always stored in main-memory. Finally, if nSpill is a
+** positive value, then the journal file is initially created in-memory
+** but may be flushed to disk later on. In this case the journal file is
+** flushed to disk either when it grows larger than nSpill bytes in size,
+** or when sqlite3JournalCreate() is called.
 */
-void sqlite3MemJournalOpen(sqlite3_file *pJfd){
-  MemJournal *p = (MemJournal *)pJfd;
-  assert( EIGHT_BYTE_ALIGNMENT(p) );
-  memset(p, 0, sqlite3MemJournalSize());
-  p->pMethod = (sqlite3_io_methods*)&MemJournalMethods;
+int sqlite3JournalOpen(
+  sqlite3_vfs *pVfs,         /* The VFS to use for actual file I/O */
+  const char *zName,         /* Name of the journal file */
+  sqlite3_file *pJfd,        /* Preallocated, blank file handle */
+  int flags,                 /* Opening flags */
+  int nSpill                 /* Bytes buffered before opening the file */
+){
+  MemJournal *p = (MemJournal*)pJfd;
+
+  /* Zero the file-handle object. If nSpill was passed zero, initialize
+  ** it using the sqlite3OsOpen() function of the underlying VFS. In this
+  ** case none of the code in this module is executed as a result of calls
+  ** made on the journal file-handle.  */
+  memset(p, 0, sizeof(MemJournal));
+  if( nSpill==0 ){
+    return sqlite3OsOpen(pVfs, zName, pJfd, flags, 0);
+  }
+
+  if( nSpill>0 ){
+    p->nChunkSize = nSpill;
+  }else{
+    p->nChunkSize = 8 + MEMJOURNAL_DFLT_FILECHUNKSIZE - sizeof(FileChunk);
+    assert( MEMJOURNAL_DFLT_FILECHUNKSIZE==fileChunkSize(p->nChunkSize) );
+  }
+
+  p->pMethod = (const sqlite3_io_methods*)&MemJournalMethods;
+  p->nSpill = nSpill;
+  p->flags = flags;
+  p->zJournal = zName;
+  p->pVfs = pVfs;
+  return SQLITE_OK;
 }
 
 /*
-** Return true if the file-handle passed as an argument is 
-** an in-memory journal 
+** Open an in-memory journal file.
 */
-int sqlite3IsMemJournal(sqlite3_file *pJfd){
-  return pJfd->pMethods==&MemJournalMethods;
+void sqlite3MemJournalOpen(sqlite3_file *pJfd){
+  sqlite3JournalOpen(0, 0, pJfd, 0, -1);
+}
+
+#ifdef SQLITE_ENABLE_ATOMIC_WRITE
+/*
+** If the argument p points to a MemJournal structure that is not an 
+** in-memory-only journal file (i.e. is one that was opened with a +ve
+** nSpill parameter), and the underlying file has not yet been created, 
+** create it now.
+*/
+int sqlite3JournalCreate(sqlite3_file *p){
+  int rc = SQLITE_OK;
+  if( p->pMethods==&MemJournalMethods && ((MemJournal*)p)->nSpill>0 ){
+    rc = memjrnlCreateFile((MemJournal*)p);
+  }
+  return rc;
+}
+#endif
+
+/*
+** The file-handle passed as the only argument is open on a journal file.
+** Return true if this "journal file" is currently stored in heap memory,
+** or false otherwise.
+*/
+int sqlite3JournalIsInMemory(sqlite3_file *p){
+  return p->pMethods==&MemJournalMethods;
 }
 
 /* 
-** Return the number of bytes required to store a MemJournal file descriptor.
+** Return the number of bytes required to store a JournalFile that uses vfs
+** pVfs to create the underlying on-disk files.
 */
-int sqlite3MemJournalSize(void){
-  return sizeof(MemJournal);
+int sqlite3JournalSize(sqlite3_vfs *pVfs){
+  return MAX(pVfs->szOsFile, (int)sizeof(MemJournal));
 }