diff options
Diffstat (limited to 'kopete/plugins/statistics/sqlite/os_unix.c')
| -rw-r--r-- | kopete/plugins/statistics/sqlite/os_unix.c | 1276 |
1 files changed, 1276 insertions, 0 deletions
diff --git a/kopete/plugins/statistics/sqlite/os_unix.c b/kopete/plugins/statistics/sqlite/os_unix.c new file mode 100644 index 00000000..94fca701 --- /dev/null +++ b/kopete/plugins/statistics/sqlite/os_unix.c @@ -0,0 +1,1276 @@ +/* +** 2004 May 22 +** +** 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 that is specific to Unix systems. +*/ +#include "sqliteInt.h" +#include "os.h" +#if OS_UNIX /* This file is used on unix only */ + + +#include <time.h> +#include <errno.h> +#include <unistd.h> +#ifndef O_LARGEFILE +# define O_LARGEFILE 0 +#endif +#ifdef SQLITE_DISABLE_LFS +# undef O_LARGEFILE +# define O_LARGEFILE 0 +#endif +#ifndef O_NOFOLLOW +# define O_NOFOLLOW 0 +#endif +#ifndef O_BINARY +# define O_BINARY 0 +#endif + + +/* +** The DJGPP compiler environment looks mostly like Unix, but it +** lacks the fcntl() system call. So redefine fcntl() to be something +** that always succeeds. This means that locking does not occur under +** DJGPP. But its DOS - what did you expect? +*/ +#ifdef __DJGPP__ +# define fcntl(A,B,C) 0 +#endif + +/* +** Macros used to determine whether or not to use threads. The +** SQLITE_UNIX_THREADS macro is defined if we are synchronizing for +** Posix threads and SQLITE_W32_THREADS is defined if we are +** synchronizing using Win32 threads. +*/ +#if defined(THREADSAFE) && THREADSAFE +# include <pthread.h> +# define SQLITE_UNIX_THREADS 1 +#endif + + +/* +** Include code that is common to all os_*.c files +*/ +#include "os_common.h" + +#if defined(THREADSAFE) && THREADSAFE && defined(__linux__) +#define getpid pthread_self +#endif + +/* +** Here is the dirt on POSIX advisory locks: ANSI STD 1003.1 (1996) +** section 6.5.2.2 lines 483 through 490 specify that when a process +** sets or clears a lock, that operation overrides any prior locks set +** by the same process. It does not explicitly say so, but this implies +** that it overrides locks set by the same process using a different +** file descriptor. Consider this test case: +** +** int fd1 = open("./file1", O_RDWR|O_CREAT, 0644); +** int fd2 = open("./file2", O_RDWR|O_CREAT, 0644); +** +** Suppose ./file1 and ./file2 are really the same file (because +** one is a hard or symbolic link to the other) then if you set +** an exclusive lock on fd1, then try to get an exclusive lock +** on fd2, it works. I would have expected the second lock to +** fail since there was already a lock on the file due to fd1. +** But not so. Since both locks came from the same process, the +** second overrides the first, even though they were on different +** file descriptors opened on different file names. +** +** Bummer. If you ask me, this is broken. Badly broken. It means +** that we cannot use POSIX locks to synchronize file access among +** competing threads of the same process. POSIX locks will work fine +** to synchronize access for threads in separate processes, but not +** threads within the same process. +** +** To work around the problem, SQLite has to manage file locks internally +** on its own. Whenever a new database is opened, we have to find the +** specific inode of the database file (the inode is determined by the +** st_dev and st_ino fields of the stat structure that fstat() fills in) +** and check for locks already existing on that inode. When locks are +** created or removed, we have to look at our own internal record of the +** locks to see if another thread has previously set a lock on that same +** inode. +** +** The OsFile structure for POSIX is no longer just an integer file +** descriptor. It is now a structure that holds the integer file +** descriptor and a pointer to a structure that describes the internal +** locks on the corresponding inode. There is one locking structure +** per inode, so if the same inode is opened twice, both OsFile structures +** point to the same locking structure. The locking structure keeps +** a reference count (so we will know when to delete it) and a "cnt" +** field that tells us its internal lock status. cnt==0 means the +** file is unlocked. cnt==-1 means the file has an exclusive lock. +** cnt>0 means there are cnt shared locks on the file. +** +** Any attempt to lock or unlock a file first checks the locking +** structure. The fcntl() system call is only invoked to set a +** POSIX lock if the internal lock structure transitions between +** a locked and an unlocked state. +** +** 2004-Jan-11: +** More recent discoveries about POSIX advisory locks. (The more +** I discover, the more I realize the a POSIX advisory locks are +** an abomination.) +** +** If you close a file descriptor that points to a file that has locks, +** all locks on that file that are owned by the current process are +** released. To work around this problem, each OsFile structure contains +** a pointer to an openCnt structure. There is one openCnt structure +** per open inode, which means that multiple OsFiles can point to a single +** openCnt. When an attempt is made to close an OsFile, if there are +** other OsFiles open on the same inode that are holding locks, the call +** to close() the file descriptor is deferred until all of the locks clear. +** The openCnt structure keeps a list of file descriptors that need to +** be closed and that list is walked (and cleared) when the last lock +** clears. +** +** First, under Linux threads, because each thread has a separate +** process ID, lock operations in one thread do not override locks +** to the same file in other threads. Linux threads behave like +** separate processes in this respect. But, if you close a file +** descriptor in linux threads, all locks are cleared, even locks +** on other threads and even though the other threads have different +** process IDs. Linux threads is inconsistent in this respect. +** (I'm beginning to think that linux threads is an abomination too.) +** The consequence of this all is that the hash table for the lockInfo +** structure has to include the process id as part of its key because +** locks in different threads are treated as distinct. But the +** openCnt structure should not include the process id in its +** key because close() clears lock on all threads, not just the current +** thread. Were it not for this goofiness in linux threads, we could +** combine the lockInfo and openCnt structures into a single structure. +** +** 2004-Jun-28: +** On some versions of linux, threads can override each others locks. +** On others not. Sometimes you can change the behavior on the same +** system by setting the LD_ASSUME_KERNEL environment variable. The +** POSIX standard is silent as to which behavior is correct, as far +** as I can tell, so other versions of unix might show the same +** inconsistency. There is no little doubt in my mind that posix +** advisory locks and linux threads are profoundly broken. +** +** To work around the inconsistencies, we have to test at runtime +** whether or not threads can override each others locks. This test +** is run once, the first time any lock is attempted. A static +** variable is set to record the results of this test for future +** use. +*/ + +/* +** An instance of the following structure serves as the key used +** to locate a particular lockInfo structure given its inode. +** +** If threads cannot override each others locks, then we set the +** lockKey.tid field to the thread ID. If threads can override +** each others locks then tid is always set to zero. tid is also +** set to zero if we compile without threading support. +*/ +struct lockKey { + dev_t dev; /* Device number */ + ino_t ino; /* Inode number */ +#ifdef SQLITE_UNIX_THREADS + pthread_t tid; /* Thread ID or zero if threads cannot override each other */ +#endif +}; + +/* +** An instance of the following structure is allocated for each open +** inode on each thread with a different process ID. (Threads have +** different process IDs on linux, but not on most other unixes.) +** +** A single inode can have multiple file descriptors, so each OsFile +** structure contains a pointer to an instance of this object and this +** object keeps a count of the number of OsFiles pointing to it. +*/ +struct lockInfo { + struct lockKey key; /* The lookup key */ + int cnt; /* Number of SHARED locks held */ + int locktype; /* One of SHARED_LOCK, RESERVED_LOCK etc. */ + int nRef; /* Number of pointers to this structure */ +}; + +/* +** An instance of the following structure serves as the key used +** to locate a particular openCnt structure given its inode. This +** is the same as the lockKey except that the thread ID is omitted. +*/ +struct openKey { + dev_t dev; /* Device number */ + ino_t ino; /* Inode number */ +}; + +/* +** An instance of the following structure is allocated for each open +** inode. This structure keeps track of the number of locks on that +** inode. If a close is attempted against an inode that is holding +** locks, the close is deferred until all locks clear by adding the +** file descriptor to be closed to the pending list. +*/ +struct openCnt { + struct openKey key; /* The lookup key */ + int nRef; /* Number of pointers to this structure */ + int nLock; /* Number of outstanding locks */ + int nPending; /* Number of pending close() operations */ + int *aPending; /* Malloced space holding fd's awaiting a close() */ +}; + +/* +** These hash table maps inodes and process IDs into lockInfo and openCnt +** structures. Access to these hash tables must be protected by a mutex. +*/ +static Hash lockHash = { SQLITE_HASH_BINARY, 0, 0, 0, 0, 0 }; +static Hash openHash = { SQLITE_HASH_BINARY, 0, 0, 0, 0, 0 }; + + +#ifdef SQLITE_UNIX_THREADS +/* +** This variable records whether or not threads can override each others +** locks. +** +** 0: No. Threads cannot override each others locks. +** 1: Yes. Threads can override each others locks. +** -1: We don't know yet. +*/ +static int threadsOverrideEachOthersLocks = -1; + +/* +** This structure holds information passed into individual test +** threads by the testThreadLockingBehavior() routine. +*/ +struct threadTestData { + int fd; /* File to be locked */ + struct flock lock; /* The locking operation */ + int result; /* Result of the locking operation */ +}; + +/* +** The testThreadLockingBehavior() routine launches two separate +** threads on this routine. This routine attempts to lock a file +** descriptor then returns. The success or failure of that attempt +** allows the testThreadLockingBehavior() procedure to determine +** whether or not threads can override each others locks. +*/ +static void *threadLockingTest(void *pArg){ + struct threadTestData *pData = (struct threadTestData*)pArg; + pData->result = fcntl(pData->fd, F_SETLK, &pData->lock); + return pArg; +} + +/* +** This procedure attempts to determine whether or not threads +** can override each others locks then sets the +** threadsOverrideEachOthersLocks variable appropriately. +*/ +static void testThreadLockingBehavior(fd_orig){ + int fd; + struct threadTestData d[2]; + pthread_t t[2]; + + fd = dup(fd_orig); + if( fd<0 ) return; + memset(d, 0, sizeof(d)); + d[0].fd = fd; + d[0].lock.l_type = F_RDLCK; + d[0].lock.l_len = 1; + d[0].lock.l_start = 0; + d[0].lock.l_whence = SEEK_SET; + d[1] = d[0]; + d[1].lock.l_type = F_WRLCK; + pthread_create(&t[0], 0, threadLockingTest, &d[0]); + pthread_create(&t[1], 0, threadLockingTest, &d[1]); + pthread_join(t[0], 0); + pthread_join(t[1], 0); + close(fd); + threadsOverrideEachOthersLocks = d[0].result==0 && d[1].result==0; +} +#endif /* SQLITE_UNIX_THREADS */ + +/* +** Release a lockInfo structure previously allocated by findLockInfo(). +*/ +static void releaseLockInfo(struct lockInfo *pLock){ + pLock->nRef--; + if( pLock->nRef==0 ){ + sqlite3HashInsert(&lockHash, &pLock->key, sizeof(pLock->key), 0); + sqliteFree(pLock); + } +} + +/* +** Release a openCnt structure previously allocated by findLockInfo(). +*/ +static void releaseOpenCnt(struct openCnt *pOpen){ + pOpen->nRef--; + if( pOpen->nRef==0 ){ + sqlite3HashInsert(&openHash, &pOpen->key, sizeof(pOpen->key), 0); + sqliteFree(pOpen->aPending); + sqliteFree(pOpen); + } +} + +/* +** Given a file descriptor, locate lockInfo and openCnt structures that +** describes that file descriptor. Create a new ones if necessary. The +** return values might be unset if an error occurs. +** +** Return the number of errors. +*/ +static int findLockInfo( + int fd, /* The file descriptor used in the key */ + struct lockInfo **ppLock, /* Return the lockInfo structure here */ + struct openCnt **ppOpen /* Return the openCnt structure here */ +){ + int rc; + struct lockKey key1; + struct openKey key2; + struct stat statbuf; + struct lockInfo *pLock; + struct openCnt *pOpen; + rc = fstat(fd, &statbuf); + if( rc!=0 ) return 1; + memset(&key1, 0, sizeof(key1)); + key1.dev = statbuf.st_dev; + key1.ino = statbuf.st_ino; +#ifdef SQLITE_UNIX_THREADS + if( threadsOverrideEachOthersLocks<0 ){ + testThreadLockingBehavior(fd); + } + key1.tid = threadsOverrideEachOthersLocks ? 0 : pthread_self(); +#endif + memset(&key2, 0, sizeof(key2)); + key2.dev = statbuf.st_dev; + key2.ino = statbuf.st_ino; + pLock = (struct lockInfo*)sqlite3HashFind(&lockHash, &key1, sizeof(key1)); + if( pLock==0 ){ + struct lockInfo *pOld; + pLock = sqliteMallocRaw( sizeof(*pLock) ); + if( pLock==0 ) return 1; + pLock->key = key1; + pLock->nRef = 1; + pLock->cnt = 0; + pLock->locktype = 0; + pOld = sqlite3HashInsert(&lockHash, &pLock->key, sizeof(key1), pLock); + if( pOld!=0 ){ + assert( pOld==pLock ); + sqliteFree(pLock); + return 1; + } + }else{ + pLock->nRef++; + } + *ppLock = pLock; + pOpen = (struct openCnt*)sqlite3HashFind(&openHash, &key2, sizeof(key2)); + if( pOpen==0 ){ + struct openCnt *pOld; + pOpen = sqliteMallocRaw( sizeof(*pOpen) ); + if( pOpen==0 ){ + releaseLockInfo(pLock); + return 1; + } + pOpen->key = key2; + pOpen->nRef = 1; + pOpen->nLock = 0; + pOpen->nPending = 0; + pOpen->aPending = 0; + pOld = sqlite3HashInsert(&openHash, &pOpen->key, sizeof(key2), pOpen); + if( pOld!=0 ){ + assert( pOld==pOpen ); + sqliteFree(pOpen); + releaseLockInfo(pLock); + return 1; + } + }else{ + pOpen->nRef++; + } + *ppOpen = pOpen; + return 0; +} + +/* +** Delete the named file +*/ +int sqlite3OsDelete(const char *zFilename){ + unlink(zFilename); + return SQLITE_OK; +} + +/* +** Return TRUE if the named file exists. +*/ +int sqlite3OsFileExists(const char *zFilename){ + return access(zFilename, 0)==0; +} + +/* +** Attempt to open a file for both reading and writing. If that +** fails, try opening it read-only. If the file does not exist, +** try to create it. +** +** On success, a handle for the open file is written to *id +** and *pReadonly is set to 0 if the file was opened for reading and +** writing or 1 if the file was opened read-only. The function returns +** SQLITE_OK. +** +** On failure, the function returns SQLITE_CANTOPEN and leaves +** *id and *pReadonly unchanged. +*/ +int sqlite3OsOpenReadWrite( + const char *zFilename, + OsFile *id, + int *pReadonly +){ + int rc; + assert( !id->isOpen ); + id->dirfd = -1; + id->h = open(zFilename, O_RDWR|O_CREAT|O_LARGEFILE|O_BINARY, 0644); + if( id->h<0 ){ +#ifdef EISDIR + if( errno==EISDIR ){ + return SQLITE_CANTOPEN; + } +#endif + id->h = open(zFilename, O_RDONLY|O_LARGEFILE|O_BINARY); + if( id->h<0 ){ + return SQLITE_CANTOPEN; + } + *pReadonly = 1; + }else{ + *pReadonly = 0; + } + sqlite3OsEnterMutex(); + rc = findLockInfo(id->h, &id->pLock, &id->pOpen); + sqlite3OsLeaveMutex(); + if( rc ){ + close(id->h); + return SQLITE_NOMEM; + } + id->locktype = 0; + id->isOpen = 1; + TRACE3("OPEN %-3d %s\n", id->h, zFilename); + OpenCounter(+1); + return SQLITE_OK; +} + + +/* +** Attempt to open a new file for exclusive access by this process. +** The file will be opened for both reading and writing. To avoid +** a potential security problem, we do not allow the file to have +** previously existed. Nor do we allow the file to be a symbolic +** link. +** +** If delFlag is true, then make arrangements to automatically delete +** the file when it is closed. +** +** On success, write the file handle into *id and return SQLITE_OK. +** +** On failure, return SQLITE_CANTOPEN. +*/ +int sqlite3OsOpenExclusive(const char *zFilename, OsFile *id, int delFlag){ + int rc; + assert( !id->isOpen ); + if( access(zFilename, 0)==0 ){ + return SQLITE_CANTOPEN; + } + id->dirfd = -1; + id->h = open(zFilename, + O_RDWR|O_CREAT|O_EXCL|O_NOFOLLOW|O_LARGEFILE|O_BINARY, 0600); + if( id->h<0 ){ + return SQLITE_CANTOPEN; + } + sqlite3OsEnterMutex(); + rc = findLockInfo(id->h, &id->pLock, &id->pOpen); + sqlite3OsLeaveMutex(); + if( rc ){ + close(id->h); + unlink(zFilename); + return SQLITE_NOMEM; + } + id->locktype = 0; + id->isOpen = 1; + if( delFlag ){ + unlink(zFilename); + } + TRACE3("OPEN-EX %-3d %s\n", id->h, zFilename); + OpenCounter(+1); + return SQLITE_OK; +} + +/* +** Attempt to open a new file for read-only access. +** +** On success, write the file handle into *id and return SQLITE_OK. +** +** On failure, return SQLITE_CANTOPEN. +*/ +int sqlite3OsOpenReadOnly(const char *zFilename, OsFile *id){ + int rc; + assert( !id->isOpen ); + id->dirfd = -1; + id->h = open(zFilename, O_RDONLY|O_LARGEFILE|O_BINARY); + if( id->h<0 ){ + return SQLITE_CANTOPEN; + } + sqlite3OsEnterMutex(); + rc = findLockInfo(id->h, &id->pLock, &id->pOpen); + sqlite3OsLeaveMutex(); + if( rc ){ + close(id->h); + return SQLITE_NOMEM; + } + id->locktype = 0; + id->isOpen = 1; + TRACE3("OPEN-RO %-3d %s\n", id->h, zFilename); + OpenCounter(+1); + return SQLITE_OK; +} + +/* +** Attempt to open a file descriptor for the directory that contains a +** file. This file descriptor can be used to fsync() the directory +** in order to make sure the creation of a new file is actually written +** to disk. +** +** This routine is only meaningful for Unix. It is a no-op under +** windows since windows does not support hard links. +** +** On success, a handle for a previously open file is at *id is +** updated with the new directory file descriptor and SQLITE_OK is +** returned. +** +** On failure, the function returns SQLITE_CANTOPEN and leaves +** *id unchanged. +*/ +int sqlite3OsOpenDirectory( + const char *zDirname, + OsFile *id +){ + if( !id->isOpen ){ + /* Do not open the directory if the corresponding file is not already + ** open. */ + return SQLITE_CANTOPEN; + } + assert( id->dirfd<0 ); + id->dirfd = open(zDirname, O_RDONLY|O_BINARY, 0644); + if( id->dirfd<0 ){ + return SQLITE_CANTOPEN; + } + TRACE3("OPENDIR %-3d %s\n", id->dirfd, zDirname); + return SQLITE_OK; +} + +/* +** If the following global variable points to a string which is the +** name of a directory, then that directory will be used to store +** temporary files. +*/ +const char *sqlite3_temp_directory = 0; + +/* +** Create a temporary file name in zBuf. zBuf must be big enough to +** hold at least SQLITE_TEMPNAME_SIZE characters. +*/ +int sqlite3OsTempFileName(char *zBuf){ + static const char *azDirs[] = { + 0, + "/var/tmp", + "/usr/tmp", + "/tmp", + ".", + }; + static const unsigned char zChars[] = + "abcdefghijklmnopqrstuvwxyz" + "ABCDEFGHIJKLMNOPQRSTUVWXYZ" + "0123456789"; + int i, j; + struct stat buf; + const char *zDir = "."; + azDirs[0] = sqlite3_temp_directory; + for(i=0; i<sizeof(azDirs)/sizeof(azDirs[0]); i++){ + if( azDirs[i]==0 ) continue; + if( stat(azDirs[i], &buf) ) continue; + if( !S_ISDIR(buf.st_mode) ) continue; + if( access(azDirs[i], 07) ) continue; + zDir = azDirs[i]; + break; + } + do{ + sprintf(zBuf, "%s/"TEMP_FILE_PREFIX, zDir); + j = strlen(zBuf); + sqlite3Randomness(15, &zBuf[j]); + for(i=0; i<15; i++, j++){ + zBuf[j] = (char)zChars[ ((unsigned char)zBuf[j])%(sizeof(zChars)-1) ]; + } + zBuf[j] = 0; + }while( access(zBuf,0)==0 ); + return SQLITE_OK; +} + +/* +** Read data from a file into a buffer. Return SQLITE_OK if all +** bytes were read successfully and SQLITE_IOERR if anything goes +** wrong. +*/ +int sqlite3OsRead(OsFile *id, void *pBuf, int amt){ + int got; + assert( id->isOpen ); + SimulateIOError(SQLITE_IOERR); + TIMER_START; + got = read(id->h, pBuf, amt); + TIMER_END; + TRACE4("READ %-3d %7d %d\n", id->h, last_page, TIMER_ELAPSED); + SEEK(0); + /* if( got<0 ) got = 0; */ + if( got==amt ){ + return SQLITE_OK; + }else{ + return SQLITE_IOERR; + } +} + +/* +** Write data from a buffer into a file. Return SQLITE_OK on success +** or some other error code on failure. +*/ +int sqlite3OsWrite(OsFile *id, const void *pBuf, int amt){ + int wrote = 0; + assert( id->isOpen ); + SimulateIOError(SQLITE_IOERR); + SimulateDiskfullError; + TIMER_START; + while( amt>0 && (wrote = write(id->h, pBuf, amt))>0 ){ + amt -= wrote; + pBuf = &((char*)pBuf)[wrote]; + } + TIMER_END; + TRACE4("WRITE %-3d %7d %d\n", id->h, last_page, TIMER_ELAPSED); + SEEK(0); + if( amt>0 ){ + return SQLITE_FULL; + } + return SQLITE_OK; +} + +/* +** Move the read/write pointer in a file. +*/ +int sqlite3OsSeek(OsFile *id, i64 offset){ + assert( id->isOpen ); + SEEK(offset/1024 + 1); + lseek(id->h, offset, SEEK_SET); + return SQLITE_OK; +} + +/* +** The fsync() system call does not work as advertised on many +** unix systems. The following procedure is an attempt to make +** it work better. +*/ +static int full_fsync(int fd){ + int rc; +#ifdef F_FULLFSYNC + rc = fcntl(fd, F_FULLFSYNC, 0); + if( rc ) rc = fsync(fd); +#else + rc = fsync(fd); +#endif + return rc; +} + +/* +** Make sure all writes to a particular file are committed to disk. +** +** Under Unix, also make sure that the directory entry for the file +** has been created by fsync-ing the directory that contains the file. +** If we do not do this and we encounter a power failure, the directory +** entry for the journal might not exist after we reboot. The next +** SQLite to access the file will not know that the journal exists (because +** the directory entry for the journal was never created) and the transaction +** will not roll back - possibly leading to database corruption. +*/ +int sqlite3OsSync(OsFile *id){ + assert( id->isOpen ); + SimulateIOError(SQLITE_IOERR); + TRACE2("SYNC %-3d\n", id->h); + if( full_fsync(id->h) ){ + return SQLITE_IOERR; + } + if( id->dirfd>=0 ){ + TRACE2("DIRSYNC %-3d\n", id->dirfd); + full_fsync(id->dirfd); + close(id->dirfd); /* Only need to sync once, so close the directory */ + id->dirfd = -1; /* when we are done. */ + } + return SQLITE_OK; +} + +/* +** Sync the directory zDirname. This is a no-op on operating systems other +** than UNIX. +*/ +int sqlite3OsSyncDirectory(const char *zDirname){ + int fd; + int r; + SimulateIOError(SQLITE_IOERR); + fd = open(zDirname, O_RDONLY|O_BINARY, 0644); + TRACE3("DIRSYNC %-3d (%s)\n", fd, zDirname); + if( fd<0 ){ + return SQLITE_CANTOPEN; + } + r = fsync(fd); + close(fd); + return ((r==0)?SQLITE_OK:SQLITE_IOERR); +} + +/* +** Truncate an open file to a specified size +*/ +int sqlite3OsTruncate(OsFile *id, i64 nByte){ + assert( id->isOpen ); + SimulateIOError(SQLITE_IOERR); + return ftruncate(id->h, nByte)==0 ? SQLITE_OK : SQLITE_IOERR; +} + +/* +** Determine the current size of a file in bytes +*/ +int sqlite3OsFileSize(OsFile *id, i64 *pSize){ + struct stat buf; + assert( id->isOpen ); + SimulateIOError(SQLITE_IOERR); + if( fstat(id->h, &buf)!=0 ){ + return SQLITE_IOERR; + } + *pSize = buf.st_size; + return SQLITE_OK; +} + +/* +** This routine checks if there is a RESERVED lock held on the specified +** file by this or any other process. If such a lock is held, return +** non-zero. If the file is unlocked or holds only SHARED locks, then +** return zero. +*/ +int sqlite3OsCheckReservedLock(OsFile *id){ + int r = 0; + + assert( id->isOpen ); + sqlite3OsEnterMutex(); /* Needed because id->pLock is shared across threads */ + + /* Check if a thread in this process holds such a lock */ + if( id->pLock->locktype>SHARED_LOCK ){ + r = 1; + } + + /* Otherwise see if some other process holds it. + */ + if( !r ){ + struct flock lock; + lock.l_whence = SEEK_SET; + lock.l_start = RESERVED_BYTE; + lock.l_len = 1; + lock.l_type = F_WRLCK; + fcntl(id->h, F_GETLK, &lock); + if( lock.l_type!=F_UNLCK ){ + r = 1; + } + } + + sqlite3OsLeaveMutex(); + TRACE3("TEST WR-LOCK %d %d\n", id->h, r); + + return r; +} + +#ifdef SQLITE_DEBUG +/* +** Helper function for printing out trace information from debugging +** binaries. This returns the string represetation of the supplied +** integer lock-type. +*/ +static const char * locktypeName(int locktype){ + switch( locktype ){ + case NO_LOCK: return "NONE"; + case SHARED_LOCK: return "SHARED"; + case RESERVED_LOCK: return "RESERVED"; + case PENDING_LOCK: return "PENDING"; + case EXCLUSIVE_LOCK: return "EXCLUSIVE"; + } + return "ERROR"; +} +#endif + +/* +** Lock the file with the lock specified by parameter locktype - one +** of the following: +** +** (1) SHARED_LOCK +** (2) RESERVED_LOCK +** (3) PENDING_LOCK +** (4) EXCLUSIVE_LOCK +** +** Sometimes when requesting one lock state, additional lock states +** are inserted in between. The locking might fail on one of the later +** transitions leaving the lock state different from what it started but +** still short of its goal. The following chart shows the allowed +** transitions and the inserted intermediate states: +** +** UNLOCKED -> SHARED +** SHARED -> RESERVED +** SHARED -> (PENDING) -> EXCLUSIVE +** RESERVED -> (PENDING) -> EXCLUSIVE +** PENDING -> EXCLUSIVE +** +** This routine will only increase a lock. Use the sqlite3OsUnlock() +** routine to lower a locking level. +*/ +int sqlite3OsLock(OsFile *id, int locktype){ + /* The following describes the implementation of the various locks and + ** lock transitions in terms of the POSIX advisory shared and exclusive + ** lock primitives (called read-locks and write-locks below, to avoid + ** confusion with SQLite lock names). The algorithms are complicated + ** slightly in order to be compatible with windows systems simultaneously + ** accessing the same database file, in case that is ever required. + ** + ** Symbols defined in os.h indentify the 'pending byte' and the 'reserved + ** byte', each single bytes at well known offsets, and the 'shared byte + ** range', a range of 510 bytes at a well known offset. + ** + ** To obtain a SHARED lock, a read-lock is obtained on the 'pending + ** byte'. If this is successful, a random byte from the 'shared byte + ** range' is read-locked and the lock on the 'pending byte' released. + ** + ** A process may only obtain a RESERVED lock after it has a SHARED lock. + ** A RESERVED lock is implemented by grabbing a write-lock on the + ** 'reserved byte'. + ** + ** A process may only obtain a PENDING lock after it has obtained a + ** SHARED lock. A PENDING lock is implemented by obtaining a write-lock + ** on the 'pending byte'. This ensures that no new SHARED locks can be + ** obtained, but existing SHARED locks are allowed to persist. A process + ** does not have to obtain a RESERVED lock on the way to a PENDING lock. + ** This property is used by the algorithm for rolling back a journal file + ** after a crash. + ** + ** An EXCLUSIVE lock, obtained after a PENDING lock is held, is + ** implemented by obtaining a write-lock on the entire 'shared byte + ** range'. Since all other locks require a read-lock on one of the bytes + ** within this range, this ensures that no other locks are held on the + ** database. + ** + ** The reason a single byte cannot be used instead of the 'shared byte + ** range' is that some versions of windows do not support read-locks. By + ** locking a random byte from a range, concurrent SHARED locks may exist + ** even if the locking primitive used is always a write-lock. + */ + int rc = SQLITE_OK; + struct lockInfo *pLock = id->pLock; + struct flock lock; + int s; + + assert( id->isOpen ); + TRACE7("LOCK %d %s was %s(%s,%d) pid=%d\n", id->h, locktypeName(locktype), + locktypeName(id->locktype), locktypeName(pLock->locktype), pLock->cnt + ,getpid() ); + + /* If there is already a lock of this type or more restrictive on the + ** OsFile, do nothing. Don't use the end_lock: exit path, as + ** sqlite3OsEnterMutex() hasn't been called yet. + */ + if( id->locktype>=locktype ){ + TRACE3("LOCK %d %s ok (already held)\n", id->h, locktypeName(locktype)); + return SQLITE_OK; + } + + /* Make sure the locking sequence is correct + */ + assert( id->locktype!=NO_LOCK || locktype==SHARED_LOCK ); + assert( locktype!=PENDING_LOCK ); + assert( locktype!=RESERVED_LOCK || id->locktype==SHARED_LOCK ); + + /* This mutex is needed because id->pLock is shared across threads + */ + sqlite3OsEnterMutex(); + + /* If some thread using this PID has a lock via a different OsFile* + ** handle that precludes the requested lock, return BUSY. + */ + if( (id->locktype!=pLock->locktype && + (pLock->locktype>=PENDING_LOCK || locktype>SHARED_LOCK)) + ){ + rc = SQLITE_BUSY; + goto end_lock; + } + + /* If a SHARED lock is requested, and some thread using this PID already + ** has a SHARED or RESERVED lock, then increment reference counts and + ** return SQLITE_OK. + */ + if( locktype==SHARED_LOCK && + (pLock->locktype==SHARED_LOCK || pLock->locktype==RESERVED_LOCK) ){ + assert( locktype==SHARED_LOCK ); + assert( id->locktype==0 ); + assert( pLock->cnt>0 ); + id->locktype = SHARED_LOCK; + pLock->cnt++; + id->pOpen->nLock++; + goto end_lock; + } + + lock.l_len = 1L; + lock.l_whence = SEEK_SET; + + /* A PENDING lock is needed before acquiring a SHARED lock and before + ** acquiring an EXCLUSIVE lock. For the SHARED lock, the PENDING will + ** be released. + */ + if( locktype==SHARED_LOCK + || (locktype==EXCLUSIVE_LOCK && id->locktype<PENDING_LOCK) + ){ + lock.l_type = (locktype==SHARED_LOCK?F_RDLCK:F_WRLCK); + lock.l_start = PENDING_BYTE; + s = fcntl(id->h, F_SETLK, &lock); + if( s ){ + rc = (errno==EINVAL) ? SQLITE_NOLFS : SQLITE_BUSY; + goto end_lock; + } + } + + + /* If control gets to this point, then actually go ahead and make + ** operating system calls for the specified lock. + */ + if( locktype==SHARED_LOCK ){ + assert( pLock->cnt==0 ); + assert( pLock->locktype==0 ); + + /* Now get the read-lock */ + lock.l_start = SHARED_FIRST; + lock.l_len = SHARED_SIZE; + s = fcntl(id->h, F_SETLK, &lock); + + /* Drop the temporary PENDING lock */ + lock.l_start = PENDING_BYTE; + lock.l_len = 1L; + lock.l_type = F_UNLCK; + fcntl(id->h, F_SETLK, &lock); + if( s ){ + rc = (errno==EINVAL) ? SQLITE_NOLFS : SQLITE_BUSY; + }else{ + id->locktype = SHARED_LOCK; + id->pOpen->nLock++; + pLock->cnt = 1; + } + }else if( locktype==EXCLUSIVE_LOCK && pLock->cnt>1 ){ + /* We are trying for an exclusive lock but another thread in this + ** same process is still holding a shared lock. */ + rc = SQLITE_BUSY; + }else{ + /* The request was for a RESERVED or EXCLUSIVE lock. It is + ** assumed that there is a SHARED or greater lock on the file + ** already. + */ + assert( 0!=id->locktype ); + lock.l_type = F_WRLCK; + switch( locktype ){ + case RESERVED_LOCK: + lock.l_start = RESERVED_BYTE; + break; + case EXCLUSIVE_LOCK: + lock.l_start = SHARED_FIRST; + lock.l_len = SHARED_SIZE; + break; + default: + assert(0); + } + s = fcntl(id->h, F_SETLK, &lock); + if( s ){ + rc = (errno==EINVAL) ? SQLITE_NOLFS : SQLITE_BUSY; + } + } + + if( rc==SQLITE_OK ){ + id->locktype = locktype; + pLock->locktype = locktype; + }else if( locktype==EXCLUSIVE_LOCK ){ + id->locktype = PENDING_LOCK; + pLock->locktype = PENDING_LOCK; + } + +end_lock: + sqlite3OsLeaveMutex(); + TRACE4("LOCK %d %s %s\n", id->h, locktypeName(locktype), + rc==SQLITE_OK ? "ok" : "failed"); + return rc; +} + +/* +** Lower the locking level on file descriptor id to locktype. locktype +** must be either NO_LOCK or SHARED_LOCK. +** +** If the locking level of the file descriptor is already at or below +** the requested locking level, this routine is a no-op. +** +** It is not possible for this routine to fail if the second argument +** is NO_LOCK. If the second argument is SHARED_LOCK, this routine +** might return SQLITE_IOERR instead of SQLITE_OK. +*/ +int sqlite3OsUnlock(OsFile *id, int locktype){ + struct lockInfo *pLock; + struct flock lock; + int rc = SQLITE_OK; + + assert( id->isOpen ); + TRACE7("UNLOCK %d %d was %d(%d,%d) pid=%d\n", id->h, locktype, id->locktype, + id->pLock->locktype, id->pLock->cnt, getpid()); + + assert( locktype<=SHARED_LOCK ); + if( id->locktype<=locktype ){ + return SQLITE_OK; + } + sqlite3OsEnterMutex(); + pLock = id->pLock; + assert( pLock->cnt!=0 ); + if( id->locktype>SHARED_LOCK ){ + assert( pLock->locktype==id->locktype ); + if( locktype==SHARED_LOCK ){ + lock.l_type = F_RDLCK; + lock.l_whence = SEEK_SET; + lock.l_start = SHARED_FIRST; + lock.l_len = SHARED_SIZE; + if( fcntl(id->h, F_SETLK, &lock)!=0 ){ + /* This should never happen */ + rc = SQLITE_IOERR; + } + } + lock.l_type = F_UNLCK; + lock.l_whence = SEEK_SET; + lock.l_start = PENDING_BYTE; + lock.l_len = 2L; assert( PENDING_BYTE+1==RESERVED_BYTE ); + fcntl(id->h, F_SETLK, &lock); + pLock->locktype = SHARED_LOCK; + } + if( locktype==NO_LOCK ){ + struct openCnt *pOpen; + + /* Decrement the shared lock counter. Release the lock using an + ** OS call only when all threads in this same process have released + ** the lock. + */ + pLock->cnt--; + if( pLock->cnt==0 ){ + lock.l_type = F_UNLCK; + lock.l_whence = SEEK_SET; + lock.l_start = lock.l_len = 0L; + fcntl(id->h, F_SETLK, &lock); + pLock->locktype = NO_LOCK; + } + + /* Decrement the count of locks against this same file. When the + ** count reaches zero, close any other file descriptors whose close + ** was deferred because of outstanding locks. + */ + pOpen = id->pOpen; + pOpen->nLock--; + assert( pOpen->nLock>=0 ); + if( pOpen->nLock==0 && pOpen->nPending>0 ){ + int i; + for(i=0; i<pOpen->nPending; i++){ + close(pOpen->aPending[i]); + } + sqliteFree(pOpen->aPending); + pOpen->nPending = 0; + pOpen->aPending = 0; + } + } + sqlite3OsLeaveMutex(); + id->locktype = locktype; + return rc; +} + +/* +** Close a file. +*/ +int sqlite3OsClose(OsFile *id){ + if( !id->isOpen ) return SQLITE_OK; + sqlite3OsUnlock(id, NO_LOCK); + if( id->dirfd>=0 ) close(id->dirfd); + id->dirfd = -1; + sqlite3OsEnterMutex(); + if( id->pOpen->nLock ){ + /* If there are outstanding locks, do not actually close the file just + ** yet because that would clear those locks. Instead, add the file + ** descriptor to pOpen->aPending. It will be automatically closed when + ** the last lock is cleared. + */ + int *aNew; + struct openCnt *pOpen = id->pOpen; + pOpen->nPending++; + aNew = sqliteRealloc( pOpen->aPending, pOpen->nPending*sizeof(int) ); + if( aNew==0 ){ + /* If a malloc fails, just leak the file descriptor */ + }else{ + pOpen->aPending = aNew; + pOpen->aPending[pOpen->nPending-1] = id->h; + } + }else{ + /* There are no outstanding locks so we can close the file immediately */ + close(id->h); + } + releaseLockInfo(id->pLock); + releaseOpenCnt(id->pOpen); + sqlite3OsLeaveMutex(); + id->isOpen = 0; + TRACE2("CLOSE %-3d\n", id->h); + OpenCounter(-1); + return SQLITE_OK; +} + +/* +** Get information to seed the random number generator. The seed +** is written into the buffer zBuf[256]. The calling function must +** supply a sufficiently large buffer. +*/ +int sqlite3OsRandomSeed(char *zBuf){ + /* We have to initialize zBuf to prevent valgrind from reporting + ** errors. The reports issued by valgrind are incorrect - we would + ** prefer that the randomness be increased by making use of the + ** uninitialized space in zBuf - but valgrind errors tend to worry + ** some users. Rather than argue, it seems easier just to initialize + ** the whole array and silence valgrind, even if that means less randomness + ** in the random seed. + ** + ** When testing, initializing zBuf[] to zero is all we do. That means + ** that we always use the same random number sequence.* This makes the + ** tests repeatable. + */ + memset(zBuf, 0, 256); +#if !defined(SQLITE_TEST) + { + int pid; + time((time_t*)zBuf); + pid = getpid(); + memcpy(&zBuf[sizeof(time_t)], &pid, sizeof(pid)); + } +#endif + return SQLITE_OK; +} + +/* +** Sleep for a little while. Return the amount of time slept. +*/ +int sqlite3OsSleep(int ms){ +#if defined(HAVE_USLEEP) && HAVE_USLEEP + usleep(ms*1000); + return ms; +#else + sleep((ms+999)/1000); + return 1000*((ms+999)/1000); +#endif +} + +/* +** Static variables used for thread synchronization +*/ +static int inMutex = 0; +#ifdef SQLITE_UNIX_THREADS +static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER; +#endif + +/* +** The following pair of routine implement mutual exclusion for +** multi-threaded processes. Only a single thread is allowed to +** executed code that is surrounded by EnterMutex() and LeaveMutex(). +** +** SQLite uses only a single Mutex. There is not much critical +** code and what little there is executes quickly and without blocking. +*/ +void sqlite3OsEnterMutex(){ +#ifdef SQLITE_UNIX_THREADS + pthread_mutex_lock(&mutex); +#endif + assert( !inMutex ); + inMutex = 1; +} +void sqlite3OsLeaveMutex(){ + assert( inMutex ); + inMutex = 0; +#ifdef SQLITE_UNIX_THREADS + pthread_mutex_unlock(&mutex); +#endif +} + +/* +** Turn a relative pathname into a full pathname. Return a pointer +** to the full pathname stored in space obtained from sqliteMalloc(). +** The calling function is responsible for freeing this space once it +** is no longer needed. +*/ +char *sqlite3OsFullPathname(const char *zRelative){ + char *zFull = 0; + if( zRelative[0]=='/' ){ + sqlite3SetString(&zFull, zRelative, (char*)0); + }else{ + char zBuf[5000]; + sqlite3SetString(&zFull, getcwd(zBuf, sizeof(zBuf)), "/", zRelative, + (char*)0); + } + return zFull; +} + +/* +** The following variable, if set to a non-zero value, becomes the result +** returned from sqlite3OsCurrentTime(). This is used for testing. +*/ +#ifdef SQLITE_TEST +int sqlite3_current_time = 0; +#endif + +/* +** Find the current time (in Universal Coordinated Time). Write the +** current time and date as a Julian Day number into *prNow and +** return 0. Return 1 if the time and date cannot be found. +*/ +int sqlite3OsCurrentTime(double *prNow){ + time_t t; + time(&t); + *prNow = t/86400.0 + 2440587.5; +#ifdef SQLITE_TEST + if( sqlite3_current_time ){ + *prNow = sqlite3_current_time/86400.0 + 2440587.5; + } +#endif + return 0; +} + +#if 0 /* NOT USED */ +/* +** Find the time that the file was last modified. Write the +** modification time and date as a Julian Day number into *prNow and +** return SQLITE_OK. Return SQLITE_ERROR if the modification +** time cannot be found. +*/ +int sqlite3OsFileModTime(OsFile *id, double *prNow){ + int rc; + struct stat statbuf; + if( fstat(id->h, &statbuf)==0 ){ + *prNow = statbuf.st_mtime/86400.0 + 2440587.5; + rc = SQLITE_OK; + }else{ + rc = SQLITE_ERROR; + } + return rc; +} +#endif /* NOT USED */ + +#endif /* OS_UNIX */ |