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1 /*
2 ** 2007 September 14
3 **
4 ** The author disclaims copyright to this source code. In place of
5 ** a legal notice, here is a blessing:
6 **
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 *************************************************************************
13 ** OVERVIEW:
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
30 ** time option).
32 ** ASSUMPTIONS:
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.
44 ** FILE FORMAT:
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)
74 ** are zeroed.
76 ** LOCKING:
78 ** File locking is a no-op. Only one connection may be open at any one
79 ** time using this demo vfs.
82 #include "sqlite3.h"
83 #include <assert.h>
84 #include <string.h>
87 ** Maximum pathname length supported by the fs backend.
89 #define BLOCKSIZE 512
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;
98 struct fs_real_file {
99 sqlite3_file *pFile;
100 const char *zName;
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 */
105 fs_real_file *pNext;
106 fs_real_file **ppThis;
109 typedef struct fs_file fs_file;
110 struct fs_file {
111 sqlite3_file base;
112 int eType;
113 fs_real_file *pReal;
116 typedef struct tmp_file tmp_file;
117 struct tmp_file {
118 sqlite3_file base;
119 int nSize;
120 int nAlloc;
121 char *zAlloc;
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;
177 struct fs_vfs_t {
178 sqlite3_vfs base;
179 fs_real_file *pFileList;
180 sqlite3_vfs *pParent;
183 static fs_vfs_t fs_vfs = {
185 1, /* iVersion */
186 0, /* szOsFile */
187 0, /* mxPathname */
188 0, /* pNext */
189 FS_VFS_NAME, /* zName */
190 0, /* pAppData */
191 fsOpen, /* xOpen */
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 */
204 0, /* pFileList */
205 0 /* pParent */
208 static sqlite3_io_methods fs_io_methods = {
209 1, /* iVersion */
210 fsClose, /* xClose */
211 fsRead, /* xRead */
212 fsWrite, /* xWrite */
213 fsTruncate, /* xTruncate */
214 fsSync, /* xSync */
215 fsFileSize, /* xFileSize */
216 fsLock, /* xLock */
217 fsUnlock, /* xUnlock */
218 fsCheckReservedLock, /* xCheckReservedLock */
219 fsFileControl, /* xFileControl */
220 fsSectorSize, /* xSectorSize */
221 fsDeviceCharacteristics, /* xDeviceCharacteristics */
222 0, /* xShmMap */
223 0, /* xShmLock */
224 0, /* xShmBarrier */
225 0 /* xShmUnmap */
229 static sqlite3_io_methods tmp_io_methods = {
230 1, /* iVersion */
231 tmpClose, /* xClose */
232 tmpRead, /* xRead */
233 tmpWrite, /* xWrite */
234 tmpTruncate, /* xTruncate */
235 tmpSync, /* xSync */
236 tmpFileSize, /* xFileSize */
237 tmpLock, /* xLock */
238 tmpUnlock, /* xUnlock */
239 tmpCheckReservedLock, /* xCheckReservedLock */
240 tmpFileControl, /* xFileControl */
241 tmpSectorSize, /* xSectorSize */
242 tmpDeviceCharacteristics, /* xDeviceCharacteristics */
243 0, /* xShmMap */
244 0, /* xShmLock */
245 0, /* xShmBarrier */
246 0 /* xShmUnmap */
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))
255 ** Close a tmp-file.
257 static int tmpClose(sqlite3_file *pFile){
258 tmp_file *pTmp = (tmp_file *)pFile;
259 sqlite3_free(pTmp->zAlloc);
260 return SQLITE_OK;
264 ** Read data from a tmp-file.
266 static int tmpRead(
267 sqlite3_file *pFile,
268 void *zBuf,
269 int iAmt,
270 sqlite_int64 iOfst
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);
277 return SQLITE_OK;
281 ** Write data to a tmp-file.
283 static int tmpWrite(
284 sqlite3_file *pFile,
285 const void *zBuf,
286 int iAmt,
287 sqlite_int64 iOfst
289 tmp_file *pTmp = (tmp_file *)pFile;
290 if( (iAmt+iOfst)>pTmp->nAlloc ){
291 int nNew = (int)(2*(iAmt+iOfst+pTmp->nAlloc));
292 char *zNew = sqlite3_realloc(pTmp->zAlloc, nNew);
293 if( !zNew ){
294 return SQLITE_NOMEM;
296 pTmp->zAlloc = zNew;
297 pTmp->nAlloc = nNew;
299 memcpy(&pTmp->zAlloc[iOfst], zBuf, iAmt);
300 pTmp->nSize = (int)MAX(pTmp->nSize, iOfst+iAmt);
301 return SQLITE_OK;
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 = (int)MIN(pTmp->nSize, size);
310 return SQLITE_OK;
314 ** Sync a tmp-file.
316 static int tmpSync(sqlite3_file *pFile, int flags){
317 return SQLITE_OK;
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;
326 return SQLITE_OK;
330 ** Lock a tmp-file.
332 static int tmpLock(sqlite3_file *pFile, int eLock){
333 return SQLITE_OK;
337 ** Unlock a tmp-file.
339 static int tmpUnlock(sqlite3_file *pFile, int eLock){
340 return SQLITE_OK;
344 ** Check if another file-handle holds a RESERVED lock on a tmp-file.
346 static int tmpCheckReservedLock(sqlite3_file *pFile, int *pResOut){
347 *pResOut = 0;
348 return SQLITE_OK;
352 ** File control method. For custom operations on a tmp-file.
354 static int tmpFileControl(sqlite3_file *pFile, int op, void *pArg){
355 return SQLITE_OK;
359 ** Return the sector-size in bytes for a tmp-file.
361 static int tmpSectorSize(sqlite3_file *pFile){
362 return 0;
366 ** Return the device characteristic flags supported by a tmp-file.
368 static int tmpDeviceCharacteristics(sqlite3_file *pFile){
369 return 0;
373 ** Close an fs-file.
375 static int fsClose(sqlite3_file *pFile){
376 int rc = SQLITE_OK;
377 fs_file *p = (fs_file *)pFile;
378 fs_real_file *pReal = p->pReal;
380 /* Decrement the real_file ref-count. */
381 pReal->nRef--;
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;
387 if( pReal->pNext ){
388 pReal->pNext->ppThis = pReal->ppThis;
390 rc = pReal->pFile->pMethods->xClose(pReal->pFile);
391 sqlite3_free(pReal);
394 return rc;
398 ** Read data from an fs-file.
400 static int fsRead(
401 sqlite3_file *pFile,
402 void *zBuf,
403 int iAmt,
404 sqlite_int64 iOfst
406 int rc = SQLITE_OK;
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);
417 }else{
418 /* Journal file. */
419 int iRem = iAmt;
420 int iBuf = 0;
421 int ii = (int)iOfst;
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);
427 ii += iRealAmt;
428 iBuf += iRealAmt;
429 iRem -= iRealAmt;
433 return rc;
437 ** Write data to an fs-file.
439 static int fsWrite(
440 sqlite3_file *pFile,
441 const void *zBuf,
442 int iAmt,
443 sqlite_int64 iOfst
445 int rc = SQLITE_OK;
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) ){
452 rc = SQLITE_FULL;
453 }else{
454 rc = pF->pMethods->xWrite(pF, zBuf, iAmt, iOfst+BLOCKSIZE);
455 if( rc==SQLITE_OK ){
456 pReal->nDatabase = (int)MAX(pReal->nDatabase, iAmt+iOfst);
459 }else{
460 /* Journal file. */
461 int iRem = iAmt;
462 int iBuf = 0;
463 int ii = (int)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) ){
469 rc = SQLITE_FULL;
470 }else{
471 rc = pF->pMethods->xWrite(pF, &((char *)zBuf)[iBuf], iRealAmt,iRealOff);
472 ii += iRealAmt;
473 iBuf += iRealAmt;
474 iRem -= iRealAmt;
477 if( rc==SQLITE_OK ){
478 pReal->nJournal = (int)MAX(pReal->nJournal, iAmt+iOfst);
482 return rc;
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 = (int)MIN(pReal->nDatabase, size);
493 }else{
494 pReal->nJournal = (int)MIN(pReal->nJournal, size);
496 return SQLITE_OK;
500 ** Sync an fs-file.
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;
506 int rc = SQLITE_OK;
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);
516 if( rc==SQLITE_OK ){
517 rc = pRealFile->pMethods->xSync(pRealFile, flags&(~SQLITE_SYNC_DATAONLY));
520 return rc;
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;
531 }else{
532 *pSize = pReal->nJournal;
534 return SQLITE_OK;
538 ** Lock an fs-file.
540 static int fsLock(sqlite3_file *pFile, int eLock){
541 return SQLITE_OK;
545 ** Unlock an fs-file.
547 static int fsUnlock(sqlite3_file *pFile, int eLock){
548 return SQLITE_OK;
552 ** Check if another file-handle holds a RESERVED lock on an fs-file.
554 static int fsCheckReservedLock(sqlite3_file *pFile, int *pResOut){
555 *pResOut = 0;
556 return SQLITE_OK;
560 ** File control method. For custom operations on an fs-file.
562 static int fsFileControl(sqlite3_file *pFile, int op, void *pArg){
563 return SQLITE_OK;
567 ** Return the sector-size in bytes for an fs-file.
569 static int fsSectorSize(sqlite3_file *pFile){
570 return BLOCKSIZE;
574 ** Return the device characteristic flags supported by an fs-file.
576 static int fsDeviceCharacteristics(sqlite3_file *pFile){
577 return 0;
581 ** Open an fs file handle.
583 static int fsOpen(
584 sqlite3_vfs *pVfs,
585 const char *zName,
586 sqlite3_file *pFile,
587 int flags,
588 int *pOutFlags
590 fs_vfs_t *pFsVfs = (fs_vfs_t *)pVfs;
591 fs_file *p = (fs_file *)pFile;
592 fs_real_file *pReal = 0;
593 int eType;
594 int nName;
595 int rc = SQLITE_OK;
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;
601 return SQLITE_OK;
604 eType = ((flags&(SQLITE_OPEN_MAIN_DB))?DATABASE_FILE:JOURNAL_FILE);
605 p->base.pMethods = &fs_io_methods;
606 p->eType = eType;
608 assert(strlen("-journal")==8);
609 nName = (int)strlen(zName)-((eType==JOURNAL_FILE)?8:0);
610 pReal=pFsVfs->pFileList;
611 for(; pReal && strncmp(pReal->zName, zName, nName); pReal=pReal->pNext);
613 if( !pReal ){
614 int real_flags = (flags&~(SQLITE_OPEN_MAIN_DB))|SQLITE_OPEN_TEMP_DB;
615 sqlite3_int64 size;
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);
621 if( !pReal ){
622 rc = SQLITE_NOMEM;
623 goto open_out;
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);
630 if( rc!=SQLITE_OK ){
631 goto open_out;
633 pRealFile = pReal->pFile;
635 rc = pRealFile->pMethods->xFileSize(pRealFile, &size);
636 if( rc!=SQLITE_OK ){
637 goto open_out;
639 if( size==0 ){
640 rc = pRealFile->pMethods->xWrite(pRealFile, "\0", 1, BLOBSIZE-1);
641 pReal->nBlob = BLOBSIZE;
642 }else{
643 unsigned char zS[4];
644 pReal->nBlob = (int)size;
645 rc = pRealFile->pMethods->xRead(pRealFile, zS, 4, 0);
646 pReal->nDatabase = (zS[0]<<24)+(zS[1]<<16)+(zS[2]<<8)+zS[3];
647 if( rc==SQLITE_OK ){
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;
655 if( rc==SQLITE_OK ){
656 pReal->pNext = pFsVfs->pFileList;
657 if( pReal->pNext ){
658 pReal->pNext->ppThis = &pReal->pNext;
660 pReal->ppThis = &pFsVfs->pFileList;
661 pFsVfs->pFileList = pReal;
665 open_out:
666 if( pReal ){
667 if( rc==SQLITE_OK ){
668 p->pReal = pReal;
669 pReal->nRef++;
670 }else{
671 if( pReal->pFile->pMethods ){
672 pReal->pFile->pMethods->xClose(pReal->pFile);
674 sqlite3_free(pReal);
677 return rc;
681 ** Delete the file located at zPath. If the dirSync argument is true,
682 ** ensure the file-system modifications are synced to disk before
683 ** returning.
685 static int fsDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
686 int rc = SQLITE_OK;
687 fs_vfs_t *pFsVfs = (fs_vfs_t *)pVfs;
688 fs_real_file *pReal;
689 sqlite3_file *pF;
690 int nName = (int)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);
697 if( pReal ){
698 pF = pReal->pFile;
699 rc = pF->pMethods->xWrite(pF, "\0\0\0\0", 4, pReal->nBlob-BLOCKSIZE);
700 if( rc==SQLITE_OK ){
701 pReal->nJournal = 0;
704 return rc;
708 ** Test for access permissions. Return true if the requested permission
709 ** is available, or false otherwise.
711 static int fsAccess(
712 sqlite3_vfs *pVfs,
713 const char *zPath,
714 int flags,
715 int *pResOut
717 fs_vfs_t *pFsVfs = (fs_vfs_t *)pVfs;
718 fs_real_file *pReal;
719 int isJournal = 0;
720 int nName = (int)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 ){
729 nName -= 8;
730 isJournal = 1;
733 pReal = pFsVfs->pFileList;
734 for(; pReal && strncmp(pReal->zName, zPath, nName); pReal=pReal->pNext);
736 *pResOut = (pReal && (!isJournal || pReal->nJournal>0));
737 return SQLITE_OK;
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
791 ** random data.
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
800 ** actually slept.
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);
828 #ifdef SQLITE_TEST
829 int SqlitetestOnefile_Init() {return fs_register();}
830 #endif