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| -rw-r--r-- | src/test_demovfs.c | 691 |
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diff --git a/src/test_demovfs.c b/src/test_demovfs.c new file mode 100644 index 0000000..2930767 --- /dev/null +++ b/src/test_demovfs.c @@ -0,0 +1,691 @@ +/* +** 2010 April 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 implements an example of a simple VFS implementation that +** omits complex features often not required or not possible on embedded +** platforms. Code is included to buffer writes to the journal file, +** which can be a significant performance improvement on some embedded +** platforms. +** +** OVERVIEW +** +** The code in this file implements a minimal SQLite VFS that can be +** used on Linux and other posix-like operating systems. The following +** system calls are used: +** +** File-system: access(), unlink(), getcwd() +** File IO: open(), read(), write(), fsync(), close(), fstat() +** Other: sleep(), usleep(), time() +** +** The following VFS features are omitted: +** +** 1. File locking. The user must ensure that there is at most one +** connection to each database when using this VFS. Multiple +** connections to a single shared-cache count as a single connection +** for the purposes of the previous statement. +** +** 2. The loading of dynamic extensions (shared libraries). +** +** 3. Temporary files. The user must configure SQLite to use in-memory +** temp files when using this VFS. The easiest way to do this is to +** compile with: +** +** -DSQLITE_TEMP_STORE=3 +** +** 4. File truncation. As of version 3.6.24, SQLite may run without +** a working xTruncate() call, providing the user does not configure +** SQLite to use "journal_mode=truncate", or use both +** "journal_mode=persist" and ATTACHed databases. +** +** It is assumed that the system uses UNIX-like path-names. Specifically, +** that '/' characters are used to separate path components and that +** a path-name is a relative path unless it begins with a '/'. And that +** no UTF-8 encoded paths are greater than 512 bytes in length. +** +** JOURNAL WRITE-BUFFERING +** +** To commit a transaction to the database, SQLite first writes rollback +** information into the journal file. This usually consists of 4 steps: +** +** 1. The rollback information is sequentially written into the journal +** file, starting at the start of the file. +** 2. The journal file is synced to disk. +** 3. A modification is made to the first few bytes of the journal file. +** 4. The journal file is synced to disk again. +** +** Most of the data is written in step 1 using a series of calls to the +** VFS xWrite() method. The buffers passed to the xWrite() calls are of +** various sizes. For example, as of version 3.6.24, when committing a +** transaction that modifies 3 pages of a database file that uses 4096 +** byte pages residing on a media with 512 byte sectors, SQLite makes +** eleven calls to the xWrite() method to create the rollback journal, +** as follows: +** +** Write offset | Bytes written +** ---------------------------- +** 0 512 +** 512 4 +** 516 4096 +** 4612 4 +** 4616 4 +** 4620 4096 +** 8716 4 +** 8720 4 +** 8724 4096 +** 12820 4 +** ++++++++++++SYNC+++++++++++ +** 0 12 +** ++++++++++++SYNC+++++++++++ +** +** On many operating systems, this is an efficient way to write to a file. +** However, on some embedded systems that do not cache writes in OS +** buffers it is much more efficient to write data in blocks that are +** an integer multiple of the sector-size in size and aligned at the +** start of a sector. +** +** To work around this, the code in this file allocates a fixed size +** buffer of SQLITE_DEMOVFS_BUFFERSZ using sqlite3_malloc() whenever a +** journal file is opened. It uses the buffer to coalesce sequential +** writes into aligned SQLITE_DEMOVFS_BUFFERSZ blocks. When SQLite +** invokes the xSync() method to sync the contents of the file to disk, +** all accumulated data is written out, even if it does not constitute +** a complete block. This means the actual IO to create the rollback +** journal for the example transaction above is this: +** +** Write offset | Bytes written +** ---------------------------- +** 0 8192 +** 8192 4632 +** ++++++++++++SYNC+++++++++++ +** 0 12 +** ++++++++++++SYNC+++++++++++ +** +** Much more efficient if the underlying OS is not caching write +** operations. +*/ + +#if !defined(SQLITE_TEST) || SQLITE_OS_UNIX + +#include "sqlite3.h" + +#include <assert.h> +#include <string.h> +#include <sys/types.h> +#include <sys/stat.h> +#include <sys/file.h> +#include <sys/param.h> +#include <unistd.h> +#include <time.h> +#include <errno.h> +#include <fcntl.h> + +/* +** Size of the write buffer used by journal files in bytes. +*/ +#ifndef SQLITE_DEMOVFS_BUFFERSZ +# define SQLITE_DEMOVFS_BUFFERSZ 8192 +#endif + +/* +** The maximum pathname length supported by this VFS. +*/ +#define MAXPATHNAME 512 + +/* +** When using this VFS, the sqlite3_file* handles that SQLite uses are +** actually pointers to instances of type DemoFile. +*/ +typedef struct DemoFile DemoFile; +struct DemoFile { + sqlite3_file base; /* Base class. Must be first. */ + int fd; /* File descriptor */ + + char *aBuffer; /* Pointer to malloc'd buffer */ + int nBuffer; /* Valid bytes of data in zBuffer */ + sqlite3_int64 iBufferOfst; /* Offset in file of zBuffer[0] */ +}; + +/* +** Write directly to the file passed as the first argument. Even if the +** file has a write-buffer (DemoFile.aBuffer), ignore it. +*/ +static int demoDirectWrite( + DemoFile *p, /* File handle */ + const void *zBuf, /* Buffer containing data to write */ + int iAmt, /* Size of data to write in bytes */ + sqlite_int64 iOfst /* File offset to write to */ +){ + off_t ofst; /* Return value from lseek() */ + size_t nWrite; /* Return value from write() */ + + ofst = lseek(p->fd, iOfst, SEEK_SET); + if( ofst!=iOfst ){ + return SQLITE_IOERR_WRITE; + } + + nWrite = write(p->fd, zBuf, iAmt); + if( nWrite!=iAmt ){ + return SQLITE_IOERR_WRITE; + } + + return SQLITE_OK; +} + +/* +** Flush the contents of the DemoFile.aBuffer buffer to disk. This is a +** no-op if this particular file does not have a buffer (i.e. it is not +** a journal file) or if the buffer is currently empty. +*/ +static int demoFlushBuffer(DemoFile *p){ + int rc = SQLITE_OK; + if( p->nBuffer ){ + rc = demoDirectWrite(p, p->aBuffer, p->nBuffer, p->iBufferOfst); + p->nBuffer = 0; + } + return rc; +} + +/* +** Close a file. +*/ +static int demoClose(sqlite3_file *pFile){ + int rc; + DemoFile *p = (DemoFile*)pFile; + rc = demoFlushBuffer(p); + sqlite3_free(p->aBuffer); + close(p->fd); + return rc; +} + +/* +** Read data from a file. +*/ +static int demoRead( + sqlite3_file *pFile, + void *zBuf, + int iAmt, + sqlite_int64 iOfst +){ + DemoFile *p = (DemoFile*)pFile; + off_t ofst; /* Return value from lseek() */ + int nRead; /* Return value from read() */ + int rc; /* Return code from demoFlushBuffer() */ + + /* Flush any data in the write buffer to disk in case this operation + ** is trying to read data the file-region currently cached in the buffer. + ** It would be possible to detect this case and possibly save an + ** unnecessary write here, but in practice SQLite will rarely read from + ** a journal file when there is data cached in the write-buffer. + */ + rc = demoFlushBuffer(p); + if( rc!=SQLITE_OK ){ + return rc; + } + + ofst = lseek(p->fd, iOfst, SEEK_SET); + if( ofst!=iOfst ){ + return SQLITE_IOERR_READ; + } + nRead = read(p->fd, zBuf, iAmt); + + if( nRead==iAmt ){ + return SQLITE_OK; + }else if( nRead>=0 ){ + if( nRead<iAmt ){ + memset(&((char*)zBuf)[nRead], 0, iAmt-nRead); + } + return SQLITE_IOERR_SHORT_READ; + } + + return SQLITE_IOERR_READ; +} + +/* +** Write data to a crash-file. +*/ +static int demoWrite( + sqlite3_file *pFile, + const void *zBuf, + int iAmt, + sqlite_int64 iOfst +){ + DemoFile *p = (DemoFile*)pFile; + + if( p->aBuffer ){ + char *z = (char *)zBuf; /* Pointer to remaining data to write */ + int n = iAmt; /* Number of bytes at z */ + sqlite3_int64 i = iOfst; /* File offset to write to */ + + while( n>0 ){ + int nCopy; /* Number of bytes to copy into buffer */ + + /* If the buffer is full, or if this data is not being written directly + ** following the data already buffered, flush the buffer. Flushing + ** the buffer is a no-op if it is empty. + */ + if( p->nBuffer==SQLITE_DEMOVFS_BUFFERSZ || p->iBufferOfst+p->nBuffer!=i ){ + int rc = demoFlushBuffer(p); + if( rc!=SQLITE_OK ){ + return rc; + } + } + assert( p->nBuffer==0 || p->iBufferOfst+p->nBuffer==i ); + p->iBufferOfst = i - p->nBuffer; + + /* Copy as much data as possible into the buffer. */ + nCopy = SQLITE_DEMOVFS_BUFFERSZ - p->nBuffer; + if( nCopy>n ){ + nCopy = n; + } + memcpy(&p->aBuffer[p->nBuffer], z, nCopy); + p->nBuffer += nCopy; + + n -= nCopy; + i += nCopy; + z += nCopy; + } + }else{ + return demoDirectWrite(p, zBuf, iAmt, iOfst); + } + + return SQLITE_OK; +} + +/* +** Truncate a file. This is a no-op for this VFS (see header comments at +** the top of the file). +*/ +static int demoTruncate(sqlite3_file *pFile, sqlite_int64 size){ +#if 0 + if( ftruncate(((DemoFile *)pFile)->fd, size) ) return SQLITE_IOERR_TRUNCATE; +#endif + return SQLITE_OK; +} + +/* +** Sync the contents of the file to the persistent media. +*/ +static int demoSync(sqlite3_file *pFile, int flags){ + DemoFile *p = (DemoFile*)pFile; + int rc; + + rc = demoFlushBuffer(p); + if( rc!=SQLITE_OK ){ + return rc; + } + + rc = fsync(p->fd); + return (rc==0 ? SQLITE_OK : SQLITE_IOERR_FSYNC); +} + +/* +** Write the size of the file in bytes to *pSize. +*/ +static int demoFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){ + DemoFile *p = (DemoFile*)pFile; + int rc; /* Return code from fstat() call */ + struct stat sStat; /* Output of fstat() call */ + + /* Flush the contents of the buffer to disk. As with the flush in the + ** demoRead() method, it would be possible to avoid this and save a write + ** here and there. But in practice this comes up so infrequently it is + ** not worth the trouble. + */ + rc = demoFlushBuffer(p); + if( rc!=SQLITE_OK ){ + return rc; + } + + rc = fstat(p->fd, &sStat); + if( rc!=0 ) return SQLITE_IOERR_FSTAT; + *pSize = sStat.st_size; + return SQLITE_OK; +} + +/* +** Locking functions. The xLock() and xUnlock() methods are both no-ops. +** The xCheckReservedLock() always indicates that no other process holds +** a reserved lock on the database file. This ensures that if a hot-journal +** file is found in the file-system it is rolled back. +*/ +static int demoLock(sqlite3_file *pFile, int eLock){ + return SQLITE_OK; +} +static int demoUnlock(sqlite3_file *pFile, int eLock){ + return SQLITE_OK; +} +static int demoCheckReservedLock(sqlite3_file *pFile, int *pResOut){ + *pResOut = 0; + return SQLITE_OK; +} + +/* +** No xFileControl() verbs are implemented by this VFS. +*/ +static int demoFileControl(sqlite3_file *pFile, int op, void *pArg){ + return SQLITE_NOTFOUND; +} + +/* +** The xSectorSize() and xDeviceCharacteristics() methods. These two +** may return special values allowing SQLite to optimize file-system +** access to some extent. But it is also safe to simply return 0. +*/ +static int demoSectorSize(sqlite3_file *pFile){ + return 0; +} +static int demoDeviceCharacteristics(sqlite3_file *pFile){ + return 0; +} + +/* +** Open a file handle. +*/ +static int demoOpen( + sqlite3_vfs *pVfs, /* VFS */ + const char *zName, /* File to open, or 0 for a temp file */ + sqlite3_file *pFile, /* Pointer to DemoFile struct to populate */ + int flags, /* Input SQLITE_OPEN_XXX flags */ + int *pOutFlags /* Output SQLITE_OPEN_XXX flags (or NULL) */ +){ + static const sqlite3_io_methods demoio = { + 1, /* iVersion */ + demoClose, /* xClose */ + demoRead, /* xRead */ + demoWrite, /* xWrite */ + demoTruncate, /* xTruncate */ + demoSync, /* xSync */ + demoFileSize, /* xFileSize */ + demoLock, /* xLock */ + demoUnlock, /* xUnlock */ + demoCheckReservedLock, /* xCheckReservedLock */ + demoFileControl, /* xFileControl */ + demoSectorSize, /* xSectorSize */ + demoDeviceCharacteristics /* xDeviceCharacteristics */ + }; + + DemoFile *p = (DemoFile*)pFile; /* Populate this structure */ + int oflags = 0; /* flags to pass to open() call */ + char *aBuf = 0; + + if( zName==0 ){ + return SQLITE_IOERR; + } + + if( flags&SQLITE_OPEN_MAIN_JOURNAL ){ + aBuf = (char *)sqlite3_malloc(SQLITE_DEMOVFS_BUFFERSZ); + if( !aBuf ){ + return SQLITE_NOMEM; + } + } + + if( flags&SQLITE_OPEN_EXCLUSIVE ) oflags |= O_EXCL; + if( flags&SQLITE_OPEN_CREATE ) oflags |= O_CREAT; + if( flags&SQLITE_OPEN_READONLY ) oflags |= O_RDONLY; + if( flags&SQLITE_OPEN_READWRITE ) oflags |= O_RDWR; + + memset(p, 0, sizeof(DemoFile)); + p->fd = open(zName, oflags, 0600); + if( p->fd<0 ){ + sqlite3_free(aBuf); + return SQLITE_CANTOPEN; + } + p->aBuffer = aBuf; + + if( pOutFlags ){ + *pOutFlags = flags; + } + p->base.pMethods = &demoio; + return SQLITE_OK; +} + +/* +** Delete the file identified by argument zPath. If the dirSync parameter +** is non-zero, then ensure the file-system modification to delete the +** file has been synced to disk before returning. +*/ +static int demoDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){ + int rc; /* Return code */ + + rc = unlink(zPath); + if( rc!=0 && errno==ENOENT ) return SQLITE_OK; + + if( rc==0 && dirSync ){ + int dfd; /* File descriptor open on directory */ + int i; /* Iterator variable */ + char *zSlash; + char zDir[MAXPATHNAME+1]; /* Name of directory containing file zPath */ + + /* Figure out the directory name from the path of the file deleted. */ + sqlite3_snprintf(MAXPATHNAME, zDir, "%s", zPath); + zDir[MAXPATHNAME] = '\0'; + zSlash = strrchr(zDir,'/'); + if( zSlash ){ + /* Open a file-descriptor on the directory. Sync. Close. */ + zSlash[0] = 0; + dfd = open(zDir, O_RDONLY, 0); + if( dfd<0 ){ + rc = -1; + }else{ + rc = fsync(dfd); + close(dfd); + } + } + } + return (rc==0 ? SQLITE_OK : SQLITE_IOERR_DELETE); +} + +#ifndef F_OK +# define F_OK 0 +#endif +#ifndef R_OK +# define R_OK 4 +#endif +#ifndef W_OK +# define W_OK 2 +#endif + +/* +** Query the file-system to see if the named file exists, is readable or +** is both readable and writable. +*/ +static int demoAccess( + sqlite3_vfs *pVfs, + const char *zPath, + int flags, + int *pResOut +){ + int rc; /* access() return code */ + int eAccess = F_OK; /* Second argument to access() */ + + assert( flags==SQLITE_ACCESS_EXISTS /* access(zPath, F_OK) */ + || flags==SQLITE_ACCESS_READ /* access(zPath, R_OK) */ + || flags==SQLITE_ACCESS_READWRITE /* access(zPath, R_OK|W_OK) */ + ); + + if( flags==SQLITE_ACCESS_READWRITE ) eAccess = R_OK|W_OK; + if( flags==SQLITE_ACCESS_READ ) eAccess = R_OK; + + rc = access(zPath, eAccess); + *pResOut = (rc==0); + return SQLITE_OK; +} + +/* +** Argument zPath points to a nul-terminated string containing a file path. +** If zPath is an absolute path, then it is copied as is into the output +** buffer. Otherwise, if it is a relative path, then the equivalent full +** path is written to the output buffer. +** +** This function assumes that paths are UNIX style. Specifically, that: +** +** 1. Path components are separated by a '/'. and +** 2. Full paths begin with a '/' character. +*/ +static int demoFullPathname( + sqlite3_vfs *pVfs, /* VFS */ + const char *zPath, /* Input path (possibly a relative path) */ + int nPathOut, /* Size of output buffer in bytes */ + char *zPathOut /* Pointer to output buffer */ +){ + char zDir[MAXPATHNAME+1]; + if( zPath[0]=='/' ){ + zDir[0] = '\0'; + }else{ + if( getcwd(zDir, sizeof(zDir))==0 ) return SQLITE_IOERR; + } + zDir[MAXPATHNAME] = '\0'; + + sqlite3_snprintf(nPathOut, zPathOut, "%s/%s", zDir, zPath); + zPathOut[nPathOut-1] = '\0'; + + return SQLITE_OK; +} + +/* +** The following four VFS methods: +** +** xDlOpen +** xDlError +** xDlSym +** xDlClose +** +** are supposed to implement the functionality needed by SQLite to load +** extensions compiled as shared objects. This simple VFS does not support +** this functionality, so the following functions are no-ops. +*/ +static void *demoDlOpen(sqlite3_vfs *pVfs, const char *zPath){ + return 0; +} +static void demoDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){ + sqlite3_snprintf(nByte, zErrMsg, "Loadable extensions are not supported"); + zErrMsg[nByte-1] = '\0'; +} +static void (*demoDlSym(sqlite3_vfs *pVfs, void *pH, const char *z))(void){ + return 0; +} +static void demoDlClose(sqlite3_vfs *pVfs, void *pHandle){ + return; +} + +/* +** Parameter zByte points to a buffer nByte bytes in size. Populate this +** buffer with pseudo-random data. +*/ +static int demoRandomness(sqlite3_vfs *pVfs, int nByte, char *zByte){ + return SQLITE_OK; +} + +/* +** Sleep for at least nMicro microseconds. Return the (approximate) number +** of microseconds slept for. +*/ +static int demoSleep(sqlite3_vfs *pVfs, int nMicro){ + sleep(nMicro / 1000000); + usleep(nMicro % 1000000); + return nMicro; +} + +/* +** Set *pTime to the current UTC time expressed as a Julian day. Return +** SQLITE_OK if successful, or an error code otherwise. +** +** http://en.wikipedia.org/wiki/Julian_day +** +** This implementation is not very good. The current time is rounded to +** an integer number of seconds. Also, assuming time_t is a signed 32-bit +** value, it will stop working some time in the year 2038 AD (the so-called +** "year 2038" problem that afflicts systems that store time this way). +*/ +static int demoCurrentTime(sqlite3_vfs *pVfs, double *pTime){ + time_t t = time(0); + *pTime = t/86400.0 + 2440587.5; + return SQLITE_OK; +} + +/* +** This function returns a pointer to the VFS implemented in this file. +** To make the VFS available to SQLite: +** +** sqlite3_vfs_register(sqlite3_demovfs(), 0); +*/ +sqlite3_vfs *sqlite3_demovfs(void){ + static sqlite3_vfs demovfs = { + 1, /* iVersion */ + sizeof(DemoFile), /* szOsFile */ + MAXPATHNAME, /* mxPathname */ + 0, /* pNext */ + "demo", /* zName */ + 0, /* pAppData */ + demoOpen, /* xOpen */ + demoDelete, /* xDelete */ + demoAccess, /* xAccess */ + demoFullPathname, /* xFullPathname */ + demoDlOpen, /* xDlOpen */ + demoDlError, /* xDlError */ + demoDlSym, /* xDlSym */ + demoDlClose, /* xDlClose */ + demoRandomness, /* xRandomness */ + demoSleep, /* xSleep */ + demoCurrentTime, /* xCurrentTime */ + }; + return &demovfs; +} + +#endif /* !defined(SQLITE_TEST) || SQLITE_OS_UNIX */ + + +#ifdef SQLITE_TEST + +#if defined(INCLUDE_SQLITE_TCL_H) +# include "sqlite_tcl.h" +#else +# include "tcl.h" +# ifndef SQLITE_TCLAPI +# define SQLITE_TCLAPI +# endif +#endif + +#if SQLITE_OS_UNIX +static int SQLITE_TCLAPI register_demovfs( + ClientData clientData, /* Pointer to sqlite3_enable_XXX function */ + Tcl_Interp *interp, /* The TCL interpreter that invoked this command */ + int objc, /* Number of arguments */ + Tcl_Obj *CONST objv[] /* Command arguments */ +){ + sqlite3_vfs_register(sqlite3_demovfs(), 1); + return TCL_OK; +} +static int SQLITE_TCLAPI unregister_demovfs( + ClientData clientData, /* Pointer to sqlite3_enable_XXX function */ + Tcl_Interp *interp, /* The TCL interpreter that invoked this command */ + int objc, /* Number of arguments */ + Tcl_Obj *CONST objv[] /* Command arguments */ +){ + sqlite3_vfs_unregister(sqlite3_demovfs()); + return TCL_OK; +} + +/* +** Register commands with the TCL interpreter. +*/ +int Sqlitetest_demovfs_Init(Tcl_Interp *interp){ + Tcl_CreateObjCommand(interp, "register_demovfs", register_demovfs, 0, 0); + Tcl_CreateObjCommand(interp, "unregister_demovfs", unregister_demovfs, 0, 0); + return TCL_OK; +} + +#else +int Sqlitetest_demovfs_Init(Tcl_Interp *interp){ return TCL_OK; } +#endif + +#endif /* SQLITE_TEST */ |