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Overview
Comment: | Add the ext/misc/memvfs.c extension that implements a VFS for read-only database files contained in memory. |
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Timelines: | family | ancestors | descendants | both | trunk |
Files: | files | file ages | folders |
SHA1: |
12b7782a9af91eab913e159149cb28b3 |
User & Date: | drh 2016-09-07 18:11:11.252 |
Context
2016-09-07
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19:54 | Add support for row-value comparisons, including IN operators, and row-value updates in the UPDATE statement. (check-in: ddb5f0558c user: drh tags: trunk) | |
18:20 | Merge recent enhancements from trunk. (check-in: 00759af053 user: drh tags: apple-osx) | |
18:11 | Add the ext/misc/memvfs.c extension that implements a VFS for read-only database files contained in memory. (check-in: 12b7782a9a user: drh tags: trunk) | |
10:10 | Fix the ".read" command in the command-line shell so that it understands that the input is not interactive. (check-in: d8451fe84d user: drh tags: trunk) | |
Changes
Added ext/misc/memvfs.c.
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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 is an in-memory read-only VFS implementation. The application ** supplies a block of memory which is the database file, and this VFS ** uses that block of memory. ** ** Because there is no place to store journals and no good way to lock ** the "file", this VFS is read-only. ** ** USAGE: ** ** sqlite3_open_v2("file:/whatever?ptr=0xf05538&sz=14336", &db, ** SQLITE_OPEN_READONLY | SQLITE_OPEN_URI, ** "memvfs"); ** ** The ptr= and sz= query parameters are required or the open will fail. ** The ptr= parameter gives the memory address of the buffer holding the ** read-only database and sz= gives the size of the database. The parameter ** values may be in hexadecimal or decimal. The filename is ignored. */ #include <sqlite3ext.h> SQLITE_EXTENSION_INIT1 #include <string.h> #include <assert.h> /* ** Forward declaration of objects used by this utility */ typedef struct sqlite3_vfs MemVfs; typedef struct MemFile MemFile; /* Access to a lower-level VFS that (might) implement dynamic loading, ** access to randomness, etc. */ #define ORIGVFS(p) ((sqlite3_vfs*)((p)->pAppData)) /* An open file */ struct MemFile { sqlite3_file base; /* IO methods */ sqlite3_int64 sz; /* Size of the file */ unsigned char *aData; /* content of the file */ }; /* ** Methods for MemFile */ static int memClose(sqlite3_file*); static int memRead(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst); static int memWrite(sqlite3_file*,const void*,int iAmt, sqlite3_int64 iOfst); static int memTruncate(sqlite3_file*, sqlite3_int64 size); static int memSync(sqlite3_file*, int flags); static int memFileSize(sqlite3_file*, sqlite3_int64 *pSize); static int memLock(sqlite3_file*, int); static int memUnlock(sqlite3_file*, int); static int memCheckReservedLock(sqlite3_file*, int *pResOut); static int memFileControl(sqlite3_file*, int op, void *pArg); static int memSectorSize(sqlite3_file*); static int memDeviceCharacteristics(sqlite3_file*); static int memShmMap(sqlite3_file*, int iPg, int pgsz, int, void volatile**); static int memShmLock(sqlite3_file*, int offset, int n, int flags); static void memShmBarrier(sqlite3_file*); static int memShmUnmap(sqlite3_file*, int deleteFlag); static int memFetch(sqlite3_file*, sqlite3_int64 iOfst, int iAmt, void **pp); static int memUnfetch(sqlite3_file*, sqlite3_int64 iOfst, void *p); /* ** Methods for MemVfs */ static int memOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *); static int memDelete(sqlite3_vfs*, const char *zName, int syncDir); static int memAccess(sqlite3_vfs*, const char *zName, int flags, int *); static int memFullPathname(sqlite3_vfs*, const char *zName, int, char *zOut); static void *memDlOpen(sqlite3_vfs*, const char *zFilename); static void memDlError(sqlite3_vfs*, int nByte, char *zErrMsg); static void (*memDlSym(sqlite3_vfs *pVfs, void *p, const char*zSym))(void); static void memDlClose(sqlite3_vfs*, void*); static int memRandomness(sqlite3_vfs*, int nByte, char *zOut); static int memSleep(sqlite3_vfs*, int microseconds); static int memCurrentTime(sqlite3_vfs*, double*); static int memGetLastError(sqlite3_vfs*, int, char *); static int memCurrentTimeInt64(sqlite3_vfs*, sqlite3_int64*); static sqlite3_vfs mem_vfs = { 2, /* iVersion */ 0, /* szOsFile (set when registered) */ 1024, /* mxPathname */ 0, /* pNext */ "memvfs", /* zName */ 0, /* pAppData (set when registered) */ memOpen, /* xOpen */ memDelete, /* xDelete */ memAccess, /* xAccess */ memFullPathname, /* xFullPathname */ memDlOpen, /* xDlOpen */ memDlError, /* xDlError */ memDlSym, /* xDlSym */ memDlClose, /* xDlClose */ memRandomness, /* xRandomness */ memSleep, /* xSleep */ memCurrentTime, /* xCurrentTime */ memGetLastError, /* xGetLastError */ memCurrentTimeInt64 /* xCurrentTimeInt64 */ }; static const sqlite3_io_methods mem_io_methods = { 3, /* iVersion */ memClose, /* xClose */ memRead, /* xRead */ memWrite, /* xWrite */ memTruncate, /* xTruncate */ memSync, /* xSync */ memFileSize, /* xFileSize */ memLock, /* xLock */ memUnlock, /* xUnlock */ memCheckReservedLock, /* xCheckReservedLock */ memFileControl, /* xFileControl */ memSectorSize, /* xSectorSize */ memDeviceCharacteristics, /* xDeviceCharacteristics */ memShmMap, /* xShmMap */ memShmLock, /* xShmLock */ memShmBarrier, /* xShmBarrier */ memShmUnmap, /* xShmUnmap */ memFetch, /* xFetch */ memUnfetch /* xUnfetch */ }; /* ** Close an mem-file. ** ** The pData pointer is owned by the application, so there is nothing ** to free. */ static int memClose(sqlite3_file *pFile){ return SQLITE_OK; } /* ** Read data from an mem-file. */ static int memRead( sqlite3_file *pFile, void *zBuf, int iAmt, sqlite_int64 iOfst ){ MemFile *p = (MemFile *)pFile; memcpy(zBuf, p->aData+iOfst, iAmt); return SQLITE_OK; } /* ** Write data to an mem-file. */ static int memWrite( sqlite3_file *pFile, const void *z, int iAmt, sqlite_int64 iOfst ){ return SQLITE_READONLY; } /* ** Truncate an mem-file. */ static int memTruncate(sqlite3_file *pFile, sqlite_int64 size){ return SQLITE_READONLY; } /* ** Sync an mem-file. */ static int memSync(sqlite3_file *pFile, int flags){ return SQLITE_READONLY; } /* ** Return the current file-size of an mem-file. */ static int memFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){ MemFile *p = (MemFile *)pFile; *pSize = p->sz; return SQLITE_OK; } /* ** Lock an mem-file. */ static int memLock(sqlite3_file *pFile, int eLock){ return SQLITE_READONLY; } /* ** Unlock an mem-file. */ static int memUnlock(sqlite3_file *pFile, int eLock){ return SQLITE_OK; } /* ** Check if another file-handle holds a RESERVED lock on an mem-file. */ static int memCheckReservedLock(sqlite3_file *pFile, int *pResOut){ *pResOut = 0; return SQLITE_OK; } /* ** File control method. For custom operations on an mem-file. */ static int memFileControl(sqlite3_file *pFile, int op, void *pArg){ MemFile *p = (MemFile *)pFile; int rc = SQLITE_NOTFOUND; if( op==SQLITE_FCNTL_VFSNAME ){ *(char**)pArg = sqlite3_mprintf("mem(%p,%lld)", p->aData, p->sz); rc = SQLITE_OK; } return rc; } /* ** Return the sector-size in bytes for an mem-file. */ static int memSectorSize(sqlite3_file *pFile){ return 1024; } /* ** Return the device characteristic flags supported by an mem-file. */ static int memDeviceCharacteristics(sqlite3_file *pFile){ return SQLITE_IOCAP_IMMUTABLE; } /* Create a shared memory file mapping */ static int memShmMap( sqlite3_file *pFile, int iPg, int pgsz, int bExtend, void volatile **pp ){ return SQLITE_READONLY; } /* Perform locking on a shared-memory segment */ static int memShmLock(sqlite3_file *pFile, int offset, int n, int flags){ return SQLITE_READONLY; } /* Memory barrier operation on shared memory */ static void memShmBarrier(sqlite3_file *pFile){ return; } /* Unmap a shared memory segment */ static int memShmUnmap(sqlite3_file *pFile, int deleteFlag){ return SQLITE_OK; } /* Fetch a page of a memory-mapped file */ static int memFetch( sqlite3_file *pFile, sqlite3_int64 iOfst, int iAmt, void **pp ){ MemFile *p = (MemFile *)pFile; *pp = (void*)(p->aData + iOfst); return SQLITE_OK; } /* Release a memory-mapped page */ static int memUnfetch(sqlite3_file *pFile, sqlite3_int64 iOfst, void *pPage){ return SQLITE_OK; } /* ** Open an mem file handle. */ static int memOpen( sqlite3_vfs *pVfs, const char *zName, sqlite3_file *pFile, int flags, int *pOutFlags ){ MemFile *p = (MemFile*)pFile; memset(p, 0, sizeof(*p)); if( (flags & SQLITE_OPEN_MAIN_DB)==0 ) return SQLITE_CANTOPEN; p->aData = (unsigned char*)sqlite3_uri_int64(zName,"ptr",0); if( p->aData==0 ) return SQLITE_CANTOPEN; p->sz = sqlite3_uri_int64(zName,"sz",0); if( p->sz<0 ) return SQLITE_CANTOPEN; pFile->pMethods = &mem_io_methods; return SQLITE_OK; } /* ** Delete the file located at zPath. If the dirSync argument is true, ** ensure the file-system modifications are synced to disk before ** returning. */ static int memDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){ return SQLITE_READONLY; } /* ** Test for access permissions. Return true if the requested permission ** is available, or false otherwise. */ static int memAccess( sqlite3_vfs *pVfs, const char *zPath, int flags, int *pResOut ){ /* The spec says there are three possible values for flags. But only ** two of them are actually used */ assert( flags==SQLITE_ACCESS_EXISTS || flags==SQLITE_ACCESS_READWRITE ); if( flags==SQLITE_ACCESS_READWRITE ){ *pResOut = 0; }else{ *pResOut = 1; } return SQLITE_OK; } /* ** Populate buffer zOut with the full canonical pathname corresponding ** to the pathname in zPath. zOut is guaranteed to point to a buffer ** of at least (INST_MAX_PATHNAME+1) bytes. */ static int memFullPathname( sqlite3_vfs *pVfs, const char *zPath, int nOut, char *zOut ){ sqlite3_snprintf(nOut, zOut, "%s", zPath); return SQLITE_OK; } /* ** Open the dynamic library located at zPath and return a handle. */ static void *memDlOpen(sqlite3_vfs *pVfs, const char *zPath){ return ORIGVFS(pVfs)->xDlOpen(ORIGVFS(pVfs), zPath); } /* ** Populate the buffer zErrMsg (size nByte bytes) with a human readable ** utf-8 string describing the most recent error encountered associated ** with dynamic libraries. */ static void memDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){ ORIGVFS(pVfs)->xDlError(ORIGVFS(pVfs), nByte, zErrMsg); } /* ** Return a pointer to the symbol zSymbol in the dynamic library pHandle. */ static void (*memDlSym(sqlite3_vfs *pVfs, void *p, const char *zSym))(void){ return ORIGVFS(pVfs)->xDlSym(ORIGVFS(pVfs), p, zSym); } /* ** Close the dynamic library handle pHandle. */ static void memDlClose(sqlite3_vfs *pVfs, void *pHandle){ ORIGVFS(pVfs)->xDlClose(ORIGVFS(pVfs), pHandle); } /* ** Populate the buffer pointed to by zBufOut with nByte bytes of ** random data. */ static int memRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){ return ORIGVFS(pVfs)->xRandomness(ORIGVFS(pVfs), nByte, zBufOut); } /* ** Sleep for nMicro microseconds. Return the number of microseconds ** actually slept. */ static int memSleep(sqlite3_vfs *pVfs, int nMicro){ return ORIGVFS(pVfs)->xSleep(ORIGVFS(pVfs), nMicro); } /* ** Return the current time as a Julian Day number in *pTimeOut. */ static int memCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){ return ORIGVFS(pVfs)->xCurrentTime(ORIGVFS(pVfs), pTimeOut); } static int memGetLastError(sqlite3_vfs *pVfs, int a, char *b){ return ORIGVFS(pVfs)->xGetLastError(ORIGVFS(pVfs), a, b); } static int memCurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *p){ return ORIGVFS(pVfs)->xCurrentTimeInt64(ORIGVFS(pVfs), p); } #ifdef MEMVFS_TEST /* ** memload(FILENAME) ** ** This an SQL function used to help in testing the memvfs VFS. The ** function reads the content of a file into memory and then returns ** a string that gives the locate and size of the in-memory buffer. */ #include <stdio.h> static void memvfsMemloadFunc( sqlite3_context *context, int argc, sqlite3_value **argv ){ unsigned char *p; sqlite3_int64 sz; FILE *in; const char *zFilename = (const char*)sqlite3_value_text(argv[0]); char zReturn[100]; if( zFilename==0 ) return; in = fopen(zFilename, "rb"); if( in==0 ) return; fseek(in, 0, SEEK_END); sz = ftell(in); rewind(in); p = sqlite3_malloc( sz ); if( p==0 ){ fclose(in); sqlite3_result_error_nomem(context); return; } fread(p, sz, 1, in); fclose(in); sqlite3_snprintf(sizeof(zReturn),zReturn,"ptr=%lld&sz=%lld", (sqlite3_int64)p, sz); sqlite3_result_text(context, zReturn, -1, SQLITE_TRANSIENT); } /* Called for each new database connection */ static int memvfsRegister( sqlite3 *db, const char **pzErrMsg, const struct sqlite3_api_routines *pThunk ){ return sqlite3_create_function(db, "memload", 1, SQLITE_UTF8, 0, memvfsMemloadFunc, 0, 0); } #endif /* MEMVFS_TEST */ #ifdef _WIN32 __declspec(dllexport) #endif /* ** This routine is called when the extension is loaded. ** Register the new VFS. */ int sqlite3_memvfs_init( sqlite3 *db, char **pzErrMsg, const sqlite3_api_routines *pApi ){ int rc = SQLITE_OK; SQLITE_EXTENSION_INIT2(pApi); mem_vfs.pAppData = sqlite3_vfs_find(0); mem_vfs.szOsFile = sizeof(MemFile); rc = sqlite3_vfs_register(&mem_vfs, 1); #ifdef MEMVFS_TEST if( rc==SQLITE_OK ){ rc = sqlite3_auto_extension((void(*)(void))memvfsRegister); } #endif if( rc==SQLITE_OK ) rc = SQLITE_OK_LOAD_PERMANENTLY; return rc; } |