From 7bb481fda9ecb134804b49c2ce77ca28f7eea583 Mon Sep 17 00:00:00 2001 From: Hans-Christoph Steiner Date: Fri, 30 Mar 2012 20:42:12 -0400 Subject: Imported Upstream version 2.0.3 --- src/memjournal.c | 259 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 259 insertions(+) create mode 100644 src/memjournal.c (limited to 'src/memjournal.c') diff --git a/src/memjournal.c b/src/memjournal.c new file mode 100644 index 0000000..3e66e21 --- /dev/null +++ b/src/memjournal.c @@ -0,0 +1,259 @@ +/* +** 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. +*/ +#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 mimimizes wasted space in power-of-two +** memory allocators. +*/ +#define JOURNAL_CHUNKSIZE ((int)(1024-sizeof(FileChunk*))) + +/* Macro to find the minimum of two numeric values. +*/ +#ifndef MIN +# define MIN(x,y) ((x)<(y)?(x):(y)) +#endif + +/* +** The rollback journal is composed of a linked list of these structures. +*/ +struct FileChunk { + FileChunk *pNext; /* Next chunk in the journal */ + u8 zChunk[JOURNAL_CHUNKSIZE]; /* Content of this chunk */ +}; + +/* +** 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 +** is an instance of this class. +*/ +struct MemJournal { + sqlite3_io_methods *pMethod; /* Parent class. MUST BE FIRST */ + 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() */ +}; + +/* +** 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 ); + + if( p->readpoint.iOffset!=iOfst || iOfst==0 ){ + sqlite3_int64 iOff = 0; + for(pChunk=p->pFirst; + ALWAYS(pChunk) && (iOff+JOURNAL_CHUNKSIZE)<=iOfst; + pChunk=pChunk->pNext + ){ + iOff += JOURNAL_CHUNKSIZE; + } + }else{ + pChunk = p->readpoint.pChunk; + } + + iChunkOffset = (int)(iOfst%JOURNAL_CHUNKSIZE); + do { + int iSpace = JOURNAL_CHUNKSIZE - iChunkOffset; + int nCopy = MIN(nRead, (JOURNAL_CHUNKSIZE - iChunkOffset)); + memcpy(zOut, &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.pChunk = pChunk; + + return SQLITE_OK; +} + +/* +** 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); + + while( nWrite>0 ){ + FileChunk *pChunk = p->endpoint.pChunk; + int iChunkOffset = (int)(p->endpoint.iOffset%JOURNAL_CHUNKSIZE); + int iSpace = MIN(nWrite, JOURNAL_CHUNKSIZE - iChunkOffset); + + if( iChunkOffset==0 ){ + /* New chunk is required to extend the file. */ + FileChunk *pNew = sqlite3_malloc(sizeof(FileChunk)); + if( !pNew ){ + return SQLITE_IOERR_NOMEM; + } + pNew->pNext = 0; + if( pChunk ){ + assert( p->pFirst ); + pChunk->pNext = pNew; + }else{ + assert( !p->pFirst ); + p->pFirst = pNew; + } + p->endpoint.pChunk = pNew; + } + + memcpy(&p->endpoint.pChunk->zChunk[iChunkOffset], zWrite, iSpace); + zWrite += iSpace; + nWrite -= iSpace; + p->endpoint.iOffset += iSpace; + } + + return SQLITE_OK; +} + +/* +** Truncate the file. +*/ +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); + } + sqlite3MemJournalOpen(pJfd); + return SQLITE_OK; +} + +/* +** Close the file. +*/ +static int memjrnlClose(sqlite3_file *pJfd){ + memjrnlTruncate(pJfd, 0); + 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. +*/ +static int memjrnlSync(sqlite3_file *NotUsed, int NotUsed2){ + UNUSED_PARAMETER2(NotUsed, NotUsed2); + 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; +} + +/* +** Table of methods for MemJournal sqlite3_file object. +*/ +static const struct sqlite3_io_methods MemJournalMethods = { + 1, /* iVersion */ + memjrnlClose, /* xClose */ + memjrnlRead, /* xRead */ + memjrnlWrite, /* xWrite */ + memjrnlTruncate, /* xTruncate */ + memjrnlSync, /* xSync */ + memjrnlFileSize, /* xFileSize */ + 0, /* xLock */ + 0, /* xUnlock */ + 0, /* xCheckReservedLock */ + 0, /* xFileControl */ + 0, /* xSectorSize */ + 0, /* xDeviceCharacteristics */ + 0, /* xShmMap */ + 0, /* xShmLock */ + 0, /* xShmBarrier */ + 0 /* xShmUnlock */ +}; + +/* +** Open a journal file. +*/ +void sqlite3MemJournalOpen(sqlite3_file *pJfd){ + MemJournal *p = (MemJournal *)pJfd; + assert( EIGHT_BYTE_ALIGNMENT(p) ); + memset(p, 0, sqlite3MemJournalSize()); + p->pMethod = (sqlite3_io_methods*)&MemJournalMethods; +} + +/* +** Return true if the file-handle passed as an argument is +** an in-memory journal +*/ +int sqlite3IsMemJournal(sqlite3_file *pJfd){ + return pJfd->pMethods==&MemJournalMethods; +} + +/* +** Return the number of bytes required to store a MemJournal file descriptor. +*/ +int sqlite3MemJournalSize(void){ + return sizeof(MemJournal); +} -- cgit v1.2.3