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-/*
-** 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 */