4 ** The author disclaims copyright to this source code. In place of
5 ** a legal notice, here is a blessing:
7 ** May you do good and not evil.
8 ** May you find forgiveness for yourself and forgive others.
9 ** May you share freely, never taking more than you give.
11 *************************************************************************
15 ** This file contains some example code demonstrating how the SQLite
16 ** vfs feature can be used to have SQLite operate directly on an
17 ** embedded media, without using an intermediate file system.
19 ** Because this is only a demo designed to run on a workstation, the
20 ** underlying media is simulated using a regular file-system file. The
21 ** size of the file is fixed when it is first created (default size 10 MB).
22 ** From SQLite's point of view, this space is used to store a single
23 ** database file and the journal file.
25 ** Any statement journal created is stored in volatile memory obtained
26 ** from sqlite3_malloc(). Any attempt to create a temporary database file
27 ** will fail (SQLITE_IOERR). To prevent SQLite from attempting this,
28 ** it should be configured to store all temporary database files in
29 ** main memory (see pragma "temp_store" or the SQLITE_TEMP_STORE compile
34 ** After it has been created, the blob file is accessed using the
35 ** following three functions only:
37 ** mediaRead(); - Read a 512 byte block from the file.
38 ** mediaWrite(); - Write a 512 byte block to the file.
39 ** mediaSync(); - Tell the media hardware to sync.
41 ** It is assumed that these can be easily implemented by any "real"
42 ** media vfs driver adapting this code.
46 ** The basic principle is that the "database file" is stored at the
47 ** beginning of the 10 MB blob and grows in a forward direction. The
48 ** "journal file" is stored at the end of the 10MB blob and grows
49 ** in the reverse direction. If, during a transaction, insufficient
50 ** space is available to expand either the journal or database file,
51 ** an SQLITE_FULL error is returned. The database file is never allowed
52 ** to consume more than 90% of the blob space. If SQLite tries to
53 ** create a file larger than this, SQLITE_FULL is returned.
55 ** No allowance is made for "wear-leveling", as is required by.
56 ** embedded devices in the absence of equivalent hardware features.
58 ** The first 512 block byte of the file is reserved for storing the
59 ** size of the "database file". It is updated as part of the sync()
60 ** operation. On startup, it can only be trusted if no journal file
61 ** exists. If a journal-file does exist, then it stores the real size
62 ** of the database region. The second and subsequent blocks store the
63 ** actual database content.
65 ** The size of the "journal file" is not stored persistently in the
66 ** file. When the system is running, the size of the journal file is
67 ** stored in volatile memory. When recovering from a crash, this vfs
68 ** reports a very large size for the journal file. The normal journal
69 ** header and checksum mechanisms serve to prevent SQLite from
70 ** processing any data that lies past the logical end of the journal.
72 ** When SQLite calls OsDelete() to delete the journal file, the final
73 ** 512 bytes of the blob (the area containing the first journal header)
78 ** File locking is a no-op. Only one connection may be open at any one
79 ** time using this demo vfs.
87 ** Maximum pathname length supported by the fs backend.
90 #define BLOBSIZE 10485760
93 ** Name used to identify this VFS.
95 #define FS_VFS_NAME "fs"
97 typedef struct fs_real_file fs_real_file;
101 int nDatabase; /* Current size of database region */
102 int nJournal; /* Current size of journal region */
103 int nBlob; /* Total size of allocated blob */
104 int nRef; /* Number of pointers to this structure */
106 fs_real_file **ppThis;
109 typedef struct fs_file fs_file;
116 typedef struct tmp_file tmp_file;
124 /* Values for fs_file.eType. */
125 #define DATABASE_FILE 1
126 #define JOURNAL_FILE 2
129 ** Method declarations for fs_file.
131 static int fsClose(sqlite3_file*);
132 static int fsRead(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
133 static int fsWrite(sqlite3_file*, const void*, int iAmt, sqlite3_int64 iOfst);
134 static int fsTruncate(sqlite3_file*, sqlite3_int64 size);
135 static int fsSync(sqlite3_file*, int flags);
136 static int fsFileSize(sqlite3_file*, sqlite3_int64 *pSize);
137 static int fsLock(sqlite3_file*, int);
138 static int fsUnlock(sqlite3_file*, int);
139 static int fsCheckReservedLock(sqlite3_file*, int *pResOut);
140 static int fsFileControl(sqlite3_file*, int op, void *pArg);
141 static int fsSectorSize(sqlite3_file*);
142 static int fsDeviceCharacteristics(sqlite3_file*);
145 ** Method declarations for tmp_file.
147 static int tmpClose(sqlite3_file*);
148 static int tmpRead(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
149 static int tmpWrite(sqlite3_file*, const void*, int iAmt, sqlite3_int64 iOfst);
150 static int tmpTruncate(sqlite3_file*, sqlite3_int64 size);
151 static int tmpSync(sqlite3_file*, int flags);
152 static int tmpFileSize(sqlite3_file*, sqlite3_int64 *pSize);
153 static int tmpLock(sqlite3_file*, int);
154 static int tmpUnlock(sqlite3_file*, int);
155 static int tmpCheckReservedLock(sqlite3_file*, int *pResOut);
156 static int tmpFileControl(sqlite3_file*, int op, void *pArg);
157 static int tmpSectorSize(sqlite3_file*);
158 static int tmpDeviceCharacteristics(sqlite3_file*);
161 ** Method declarations for fs_vfs.
163 static int fsOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
164 static int fsDelete(sqlite3_vfs*, const char *zName, int syncDir);
165 static int fsAccess(sqlite3_vfs*, const char *zName, int flags, int *);
166 static int fsFullPathname(sqlite3_vfs*, const char *zName, int nOut,char *zOut);
167 static void *fsDlOpen(sqlite3_vfs*, const char *zFilename);
168 static void fsDlError(sqlite3_vfs*, int nByte, char *zErrMsg);
169 static void (*fsDlSym(sqlite3_vfs*,void*, const char *zSymbol))(void);
170 static void fsDlClose(sqlite3_vfs*, void*);
171 static int fsRandomness(sqlite3_vfs*, int nByte, char *zOut);
172 static int fsSleep(sqlite3_vfs*, int microseconds);
173 static int fsCurrentTime(sqlite3_vfs*, double*);
176 typedef struct fs_vfs_t fs_vfs_t;
179 fs_real_file *pFileList;
180 sqlite3_vfs *pParent;
183 static fs_vfs_t fs_vfs = {
189 FS_VFS_NAME, /* zName */
192 fsDelete, /* xDelete */
193 fsAccess, /* xAccess */
194 fsFullPathname, /* xFullPathname */
195 fsDlOpen, /* xDlOpen */
196 fsDlError, /* xDlError */
197 fsDlSym, /* xDlSym */
198 fsDlClose, /* xDlClose */
199 fsRandomness, /* xRandomness */
200 fsSleep, /* xSleep */
201 fsCurrentTime, /* xCurrentTime */
202 0 /* xCurrentTimeInt64 */
208 static sqlite3_io_methods fs_io_methods = {
210 fsClose, /* xClose */
212 fsWrite, /* xWrite */
213 fsTruncate, /* xTruncate */
215 fsFileSize, /* xFileSize */
217 fsUnlock, /* xUnlock */
218 fsCheckReservedLock, /* xCheckReservedLock */
219 fsFileControl, /* xFileControl */
220 fsSectorSize, /* xSectorSize */
221 fsDeviceCharacteristics, /* xDeviceCharacteristics */
229 static sqlite3_io_methods tmp_io_methods = {
231 tmpClose, /* xClose */
233 tmpWrite, /* xWrite */
234 tmpTruncate, /* xTruncate */
236 tmpFileSize, /* xFileSize */
238 tmpUnlock, /* xUnlock */
239 tmpCheckReservedLock, /* xCheckReservedLock */
240 tmpFileControl, /* xFileControl */
241 tmpSectorSize, /* xSectorSize */
242 tmpDeviceCharacteristics, /* xDeviceCharacteristics */
249 /* Useful macros used in several places */
250 #define MIN(x,y) ((x)<(y)?(x):(y))
251 #define MAX(x,y) ((x)>(y)?(x):(y))
257 static int tmpClose(sqlite3_file *pFile){
258 tmp_file *pTmp = (tmp_file *)pFile;
259 sqlite3_free(pTmp->zAlloc);
264 ** Read data from a tmp-file.
272 tmp_file *pTmp = (tmp_file *)pFile;
273 if( (iAmt+iOfst)>pTmp->nSize ){
274 return SQLITE_IOERR_SHORT_READ;
276 memcpy(zBuf, &pTmp->zAlloc[iOfst], iAmt);
281 ** Write data to a tmp-file.
289 tmp_file *pTmp = (tmp_file *)pFile;
290 if( (iAmt+iOfst)>pTmp->nAlloc ){
291 int nNew = 2*(iAmt+iOfst+pTmp->nAlloc);
292 char *zNew = sqlite3_realloc(pTmp->zAlloc, nNew);
299 memcpy(&pTmp->zAlloc[iOfst], zBuf, iAmt);
300 pTmp->nSize = MAX(pTmp->nSize, iOfst+iAmt);
305 ** Truncate a tmp-file.
307 static int tmpTruncate(sqlite3_file *pFile, sqlite_int64 size){
308 tmp_file *pTmp = (tmp_file *)pFile;
309 pTmp->nSize = MIN(pTmp->nSize, size);
316 static int tmpSync(sqlite3_file *pFile, int flags){
321 ** Return the current file-size of a tmp-file.
323 static int tmpFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
324 tmp_file *pTmp = (tmp_file *)pFile;
325 *pSize = pTmp->nSize;
332 static int tmpLock(sqlite3_file *pFile, int eLock){
337 ** Unlock a tmp-file.
339 static int tmpUnlock(sqlite3_file *pFile, int eLock){
344 ** Check if another file-handle holds a RESERVED lock on a tmp-file.
346 static int tmpCheckReservedLock(sqlite3_file *pFile, int *pResOut){
352 ** File control method. For custom operations on a tmp-file.
354 static int tmpFileControl(sqlite3_file *pFile, int op, void *pArg){
359 ** Return the sector-size in bytes for a tmp-file.
361 static int tmpSectorSize(sqlite3_file *pFile){
366 ** Return the device characteristic flags supported by a tmp-file.
368 static int tmpDeviceCharacteristics(sqlite3_file *pFile){
375 static int fsClose(sqlite3_file *pFile){
377 fs_file *p = (fs_file *)pFile;
378 fs_real_file *pReal = p->pReal;
380 /* Decrement the real_file ref-count. */
382 assert(pReal->nRef>=0);
384 /* When the ref-count reaches 0, destroy the structure */
385 if( pReal->nRef==0 ){
386 *pReal->ppThis = pReal->pNext;
388 pReal->pNext->ppThis = pReal->ppThis;
390 rc = pReal->pFile->pMethods->xClose(pReal->pFile);
398 ** Read data from an fs-file.
407 fs_file *p = (fs_file *)pFile;
408 fs_real_file *pReal = p->pReal;
409 sqlite3_file *pF = pReal->pFile;
411 if( (p->eType==DATABASE_FILE && (iAmt+iOfst)>pReal->nDatabase)
412 || (p->eType==JOURNAL_FILE && (iAmt+iOfst)>pReal->nJournal)
414 rc = SQLITE_IOERR_SHORT_READ;
415 }else if( p->eType==DATABASE_FILE ){
416 rc = pF->pMethods->xRead(pF, zBuf, iAmt, iOfst+BLOCKSIZE);
422 while( iRem>0 && rc==SQLITE_OK ){
423 int iRealOff = pReal->nBlob - BLOCKSIZE*((ii/BLOCKSIZE)+1) + ii%BLOCKSIZE;
424 int iRealAmt = MIN(iRem, BLOCKSIZE - (iRealOff%BLOCKSIZE));
426 rc = pF->pMethods->xRead(pF, &((char *)zBuf)[iBuf], iRealAmt, iRealOff);
437 ** Write data to an fs-file.
446 fs_file *p = (fs_file *)pFile;
447 fs_real_file *pReal = p->pReal;
448 sqlite3_file *pF = pReal->pFile;
450 if( p->eType==DATABASE_FILE ){
451 if( (iAmt+iOfst+BLOCKSIZE)>(pReal->nBlob-pReal->nJournal) ){
454 rc = pF->pMethods->xWrite(pF, zBuf, iAmt, iOfst+BLOCKSIZE);
456 pReal->nDatabase = MAX(pReal->nDatabase, iAmt+iOfst);
464 while( iRem>0 && rc==SQLITE_OK ){
465 int iRealOff = pReal->nBlob - BLOCKSIZE*((ii/BLOCKSIZE)+1) + ii%BLOCKSIZE;
466 int iRealAmt = MIN(iRem, BLOCKSIZE - (iRealOff%BLOCKSIZE));
468 if( iRealOff<(pReal->nDatabase+BLOCKSIZE) ){
471 rc = pF->pMethods->xWrite(pF, &((char *)zBuf)[iBuf], iRealAmt,iRealOff);
478 pReal->nJournal = MAX(pReal->nJournal, iAmt+iOfst);
486 ** Truncate an fs-file.
488 static int fsTruncate(sqlite3_file *pFile, sqlite_int64 size){
489 fs_file *p = (fs_file *)pFile;
490 fs_real_file *pReal = p->pReal;
491 if( p->eType==DATABASE_FILE ){
492 pReal->nDatabase = MIN(pReal->nDatabase, size);
494 pReal->nJournal = MIN(pReal->nJournal, size);
502 static int fsSync(sqlite3_file *pFile, int flags){
503 fs_file *p = (fs_file *)pFile;
504 fs_real_file *pReal = p->pReal;
505 sqlite3_file *pRealFile = pReal->pFile;
508 if( p->eType==DATABASE_FILE ){
509 unsigned char zSize[4];
510 zSize[0] = (pReal->nDatabase&0xFF000000)>>24;
511 zSize[1] = (pReal->nDatabase&0x00FF0000)>>16;
512 zSize[2] = (pReal->nDatabase&0x0000FF00)>>8;
513 zSize[3] = (pReal->nDatabase&0x000000FF);
514 rc = pRealFile->pMethods->xWrite(pRealFile, zSize, 4, 0);
517 rc = pRealFile->pMethods->xSync(pRealFile, flags&(~SQLITE_SYNC_DATAONLY));
524 ** Return the current file-size of an fs-file.
526 static int fsFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
527 fs_file *p = (fs_file *)pFile;
528 fs_real_file *pReal = p->pReal;
529 if( p->eType==DATABASE_FILE ){
530 *pSize = pReal->nDatabase;
532 *pSize = pReal->nJournal;
540 static int fsLock(sqlite3_file *pFile, int eLock){
545 ** Unlock an fs-file.
547 static int fsUnlock(sqlite3_file *pFile, int eLock){
552 ** Check if another file-handle holds a RESERVED lock on an fs-file.
554 static int fsCheckReservedLock(sqlite3_file *pFile, int *pResOut){
560 ** File control method. For custom operations on an fs-file.
562 static int fsFileControl(sqlite3_file *pFile, int op, void *pArg){
567 ** Return the sector-size in bytes for an fs-file.
569 static int fsSectorSize(sqlite3_file *pFile){
574 ** Return the device characteristic flags supported by an fs-file.
576 static int fsDeviceCharacteristics(sqlite3_file *pFile){
581 ** Open an fs file handle.
590 fs_vfs_t *pFsVfs = (fs_vfs_t *)pVfs;
591 fs_file *p = (fs_file *)pFile;
592 fs_real_file *pReal = 0;
597 if( 0==(flags&(SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_MAIN_JOURNAL)) ){
598 tmp_file *p = (tmp_file *)pFile;
599 memset(p, 0, sizeof(*p));
600 p->base.pMethods = &tmp_io_methods;
604 eType = ((flags&(SQLITE_OPEN_MAIN_DB))?DATABASE_FILE:JOURNAL_FILE);
605 p->base.pMethods = &fs_io_methods;
608 assert(strlen("-journal")==8);
609 nName = strlen(zName)-((eType==JOURNAL_FILE)?8:0);
610 pReal=pFsVfs->pFileList;
611 for(; pReal && strncmp(pReal->zName, zName, nName); pReal=pReal->pNext);
614 int real_flags = (flags&~(SQLITE_OPEN_MAIN_DB))|SQLITE_OPEN_TEMP_DB;
616 sqlite3_file *pRealFile;
617 sqlite3_vfs *pParent = pFsVfs->pParent;
618 assert(eType==DATABASE_FILE);
620 pReal = (fs_real_file *)sqlite3_malloc(sizeof(*pReal)+pParent->szOsFile);
625 memset(pReal, 0, sizeof(*pReal)+pParent->szOsFile);
626 pReal->zName = zName;
627 pReal->pFile = (sqlite3_file *)(&pReal[1]);
629 rc = pParent->xOpen(pParent, zName, pReal->pFile, real_flags, pOutFlags);
633 pRealFile = pReal->pFile;
635 rc = pRealFile->pMethods->xFileSize(pRealFile, &size);
640 rc = pRealFile->pMethods->xWrite(pRealFile, "\0", 1, BLOBSIZE-1);
641 pReal->nBlob = BLOBSIZE;
645 rc = pRealFile->pMethods->xRead(pRealFile, zS, 4, 0);
646 pReal->nDatabase = (zS[0]<<24)+(zS[1]<<16)+(zS[2]<<8)+zS[3];
648 rc = pRealFile->pMethods->xRead(pRealFile, zS, 4, pReal->nBlob-4);
649 if( zS[0] || zS[1] || zS[2] || zS[3] ){
650 pReal->nJournal = pReal->nBlob;
656 pReal->pNext = pFsVfs->pFileList;
658 pReal->pNext->ppThis = &pReal->pNext;
660 pReal->ppThis = &pFsVfs->pFileList;
661 pFsVfs->pFileList = pReal;
671 if( pReal->pFile->pMethods ){
672 pReal->pFile->pMethods->xClose(pReal->pFile);
681 ** Delete the file located at zPath. If the dirSync argument is true,
682 ** ensure the file-system modifications are synced to disk before
685 static int fsDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
687 fs_vfs_t *pFsVfs = (fs_vfs_t *)pVfs;
690 int nName = strlen(zPath) - 8;
692 assert(strlen("-journal")==8);
693 assert(strcmp("-journal", &zPath[nName])==0);
695 pReal = pFsVfs->pFileList;
696 for(; pReal && strncmp(pReal->zName, zPath, nName); pReal=pReal->pNext);
699 rc = pF->pMethods->xWrite(pF, "\0\0\0\0", 4, pReal->nBlob-BLOCKSIZE);
708 ** Test for access permissions. Return true if the requested permission
709 ** is available, or false otherwise.
717 fs_vfs_t *pFsVfs = (fs_vfs_t *)pVfs;
720 int nName = strlen(zPath);
722 if( flags!=SQLITE_ACCESS_EXISTS ){
723 sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
724 return pParent->xAccess(pParent, zPath, flags, pResOut);
727 assert(strlen("-journal")==8);
728 if( nName>8 && strcmp("-journal", &zPath[nName-8])==0 ){
733 pReal = pFsVfs->pFileList;
734 for(; pReal && strncmp(pReal->zName, zPath, nName); pReal=pReal->pNext);
736 *pResOut = (pReal && (!isJournal || pReal->nJournal>0));
741 ** Populate buffer zOut with the full canonical pathname corresponding
742 ** to the pathname in zPath. zOut is guaranteed to point to a buffer
743 ** of at least (FS_MAX_PATHNAME+1) bytes.
745 static int fsFullPathname(
746 sqlite3_vfs *pVfs, /* Pointer to vfs object */
747 const char *zPath, /* Possibly relative input path */
748 int nOut, /* Size of output buffer in bytes */
749 char *zOut /* Output buffer */
751 sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
752 return pParent->xFullPathname(pParent, zPath, nOut, zOut);
756 ** Open the dynamic library located at zPath and return a handle.
758 static void *fsDlOpen(sqlite3_vfs *pVfs, const char *zPath){
759 sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
760 return pParent->xDlOpen(pParent, zPath);
764 ** Populate the buffer zErrMsg (size nByte bytes) with a human readable
765 ** utf-8 string describing the most recent error encountered associated
766 ** with dynamic libraries.
768 static void fsDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
769 sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
770 pParent->xDlError(pParent, nByte, zErrMsg);
774 ** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
776 static void (*fsDlSym(sqlite3_vfs *pVfs, void *pH, const char *zSym))(void){
777 sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
778 return pParent->xDlSym(pParent, pH, zSym);
782 ** Close the dynamic library handle pHandle.
784 static void fsDlClose(sqlite3_vfs *pVfs, void *pHandle){
785 sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
786 pParent->xDlClose(pParent, pHandle);
790 ** Populate the buffer pointed to by zBufOut with nByte bytes of
793 static int fsRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
794 sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
795 return pParent->xRandomness(pParent, nByte, zBufOut);
799 ** Sleep for nMicro microseconds. Return the number of microseconds
802 static int fsSleep(sqlite3_vfs *pVfs, int nMicro){
803 sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
804 return pParent->xSleep(pParent, nMicro);
808 ** Return the current time as a Julian Day number in *pTimeOut.
810 static int fsCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
811 sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
812 return pParent->xCurrentTime(pParent, pTimeOut);
816 ** This procedure registers the fs vfs with SQLite. If the argument is
817 ** true, the fs vfs becomes the new default vfs. It is the only publicly
818 ** available function in this file.
820 int fs_register(void){
821 if( fs_vfs.pParent ) return SQLITE_OK;
822 fs_vfs.pParent = sqlite3_vfs_find(0);
823 fs_vfs.base.mxPathname = fs_vfs.pParent->mxPathname;
824 fs_vfs.base.szOsFile = MAX(sizeof(tmp_file), sizeof(fs_file));
825 return sqlite3_vfs_register(&fs_vfs.base, 0);
829 int SqlitetestOnefile_Init() {return fs_register();}