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Diffstat (limited to '3rdParty/SQLiteAsync/sqlite3async.c')
| -rw-r--r-- | 3rdParty/SQLiteAsync/sqlite3async.c | 1700 |
1 files changed, 0 insertions, 1700 deletions
diff --git a/3rdParty/SQLiteAsync/sqlite3async.c b/3rdParty/SQLiteAsync/sqlite3async.c deleted file mode 100644 index 0814da7..0000000 --- a/3rdParty/SQLiteAsync/sqlite3async.c +++ /dev/null @@ -1,1700 +0,0 @@ -/* -** 2005 December 14 -** -** 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. -** -************************************************************************* -** -** $Id: sqlite3async.c,v 1.7 2009/07/18 11:52:04 danielk1977 Exp $ -** -** This file contains the implementation of an asynchronous IO backend -** for SQLite. -*/ - -#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_ASYNCIO) - -#include "sqlite3async.h" -#include "sqlite3.h" -#include <stdarg.h> -#include <string.h> -#include <assert.h> - -/* Useful macros used in several places */ -#define MIN(x,y) ((x)<(y)?(x):(y)) -#define MAX(x,y) ((x)>(y)?(x):(y)) - -#ifndef SQLITE_AMALGAMATION -/* Macro to mark parameters as unused and silence compiler warnings. */ -#define UNUSED_PARAMETER(x) (void)(x) -#endif - -/* Forward references */ -typedef struct AsyncWrite AsyncWrite; -typedef struct AsyncFile AsyncFile; -typedef struct AsyncFileData AsyncFileData; -typedef struct AsyncFileLock AsyncFileLock; -typedef struct AsyncLock AsyncLock; - -/* Enable for debugging */ -#ifndef NDEBUG -#include <stdio.h> -static int sqlite3async_trace = 0; -# define ASYNC_TRACE(X) if( sqlite3async_trace ) asyncTrace X -static void asyncTrace(const char *zFormat, ...){ - char *z; - va_list ap; - va_start(ap, zFormat); - z = sqlite3_vmprintf(zFormat, ap); - va_end(ap); - fprintf(stderr, "[%d] %s", 0 /* (int)pthread_self() */, z); - sqlite3_free(z); -} -#else -# define ASYNC_TRACE(X) -#endif - -/* -** THREAD SAFETY NOTES -** -** Basic rules: -** -** * Both read and write access to the global write-op queue must be -** protected by the async.queueMutex. As are the async.ioError and -** async.nFile variables. -** -** * The async.pLock list and all AsyncLock and AsyncFileLock -** structures must be protected by the async.lockMutex mutex. -** -** * The file handles from the underlying system are not assumed to -** be thread safe. -** -** * See the last two paragraphs under "The Writer Thread" for -** an assumption to do with file-handle synchronization by the Os. -** -** Deadlock prevention: -** -** There are three mutex used by the system: the "writer" mutex, -** the "queue" mutex and the "lock" mutex. Rules are: -** -** * It is illegal to block on the writer mutex when any other mutex -** are held, and -** -** * It is illegal to block on the queue mutex when the lock mutex -** is held. -** -** i.e. mutex's must be grabbed in the order "writer", "queue", "lock". -** -** File system operations (invoked by SQLite thread): -** -** xOpen -** xDelete -** xFileExists -** -** File handle operations (invoked by SQLite thread): -** -** asyncWrite, asyncClose, asyncTruncate, asyncSync -** -** The operations above add an entry to the global write-op list. They -** prepare the entry, acquire the async.queueMutex momentarily while -** list pointers are manipulated to insert the new entry, then release -** the mutex and signal the writer thread to wake up in case it happens -** to be asleep. -** -** -** asyncRead, asyncFileSize. -** -** Read operations. Both of these read from both the underlying file -** first then adjust their result based on pending writes in the -** write-op queue. So async.queueMutex is held for the duration -** of these operations to prevent other threads from changing the -** queue in mid operation. -** -** -** asyncLock, asyncUnlock, asyncCheckReservedLock -** -** These primitives implement in-process locking using a hash table -** on the file name. Files are locked correctly for connections coming -** from the same process. But other processes cannot see these locks -** and will therefore not honor them. -** -** -** The writer thread: -** -** The async.writerMutex is used to make sure only there is only -** a single writer thread running at a time. -** -** Inside the writer thread is a loop that works like this: -** -** WHILE (write-op list is not empty) -** Do IO operation at head of write-op list -** Remove entry from head of write-op list -** END WHILE -** -** The async.queueMutex is always held during the <write-op list is -** not empty> test, and when the entry is removed from the head -** of the write-op list. Sometimes it is held for the interim -** period (while the IO is performed), and sometimes it is -** relinquished. It is relinquished if (a) the IO op is an -** ASYNC_CLOSE or (b) when the file handle was opened, two of -** the underlying systems handles were opened on the same -** file-system entry. -** -** If condition (b) above is true, then one file-handle -** (AsyncFile.pBaseRead) is used exclusively by sqlite threads to read the -** file, the other (AsyncFile.pBaseWrite) by sqlite3_async_flush() -** threads to perform write() operations. This means that read -** operations are not blocked by asynchronous writes (although -** asynchronous writes may still be blocked by reads). -** -** This assumes that the OS keeps two handles open on the same file -** properly in sync. That is, any read operation that starts after a -** write operation on the same file system entry has completed returns -** data consistent with the write. We also assume that if one thread -** reads a file while another is writing it all bytes other than the -** ones actually being written contain valid data. -** -** If the above assumptions are not true, set the preprocessor symbol -** SQLITE_ASYNC_TWO_FILEHANDLES to 0. -*/ - - -#ifndef NDEBUG -# define TESTONLY( X ) X -#else -# define TESTONLY( X ) -#endif - -/* -** PORTING FUNCTIONS -** -** There are two definitions of the following functions. One for pthreads -** compatible systems and one for Win32. These functions isolate the OS -** specific code required by each platform. -** -** The system uses three mutexes and a single condition variable. To -** block on a mutex, async_mutex_enter() is called. The parameter passed -** to async_mutex_enter(), which must be one of ASYNC_MUTEX_LOCK, -** ASYNC_MUTEX_QUEUE or ASYNC_MUTEX_WRITER, identifies which of the three -** mutexes to lock. Similarly, to unlock a mutex, async_mutex_leave() is -** called with a parameter identifying the mutex being unlocked. Mutexes -** are not recursive - it is an error to call async_mutex_enter() to -** lock a mutex that is already locked, or to call async_mutex_leave() -** to unlock a mutex that is not currently locked. -** -** The async_cond_wait() and async_cond_signal() functions are modelled -** on the pthreads functions with similar names. The first parameter to -** both functions is always ASYNC_COND_QUEUE. When async_cond_wait() -** is called the mutex identified by the second parameter must be held. -** The mutex is unlocked, and the calling thread simultaneously begins -** waiting for the condition variable to be signalled by another thread. -** After another thread signals the condition variable, the calling -** thread stops waiting, locks mutex eMutex and returns. The -** async_cond_signal() function is used to signal the condition variable. -** It is assumed that the mutex used by the thread calling async_cond_wait() -** is held by the caller of async_cond_signal() (otherwise there would be -** a race condition). -** -** It is guaranteed that no other thread will call async_cond_wait() when -** there is already a thread waiting on the condition variable. -** -** The async_sched_yield() function is called to suggest to the operating -** system that it would be a good time to shift the current thread off the -** CPU. The system will still work if this function is not implemented -** (it is not currently implemented for win32), but it might be marginally -** more efficient if it is. -*/ -static void async_mutex_enter(int eMutex); -static void async_mutex_leave(int eMutex); -static void async_cond_wait(int eCond, int eMutex); -static void async_cond_signal(int eCond); -static void async_sched_yield(void); - -/* -** There are also two definitions of the following. async_os_initialize() -** is called when the asynchronous VFS is first installed, and os_shutdown() -** is called when it is uninstalled (from within sqlite3async_shutdown()). -** -** For pthreads builds, both of these functions are no-ops. For win32, -** they provide an opportunity to initialize and finalize the required -** mutex and condition variables. -** -** If async_os_initialize() returns other than zero, then the initialization -** fails and SQLITE_ERROR is returned to the user. -*/ -static int async_os_initialize(void); -static void async_os_shutdown(void); - -/* Values for use as the 'eMutex' argument of the above functions. The -** integer values assigned to these constants are important for assert() -** statements that verify that mutexes are locked in the correct order. -** Specifically, it is unsafe to try to lock mutex N while holding a lock -** on mutex M if (M<=N). -*/ -#define ASYNC_MUTEX_LOCK 0 -#define ASYNC_MUTEX_QUEUE 1 -#define ASYNC_MUTEX_WRITER 2 - -/* Values for use as the 'eCond' argument of the above functions. */ -#define ASYNC_COND_QUEUE 0 - -/************************************************************************* -** Start of OS specific code. -*/ -#if SQLITE_OS_WIN || defined(_WIN32) || defined(WIN32) || defined(__CYGWIN__) || defined(__MINGW32__) || defined(__BORLANDC__) - -#include <windows.h> - -/* The following block contains the win32 specific code. */ - -#define mutex_held(X) (GetCurrentThreadId()==primitives.aHolder[X]) - -static struct AsyncPrimitives { - int isInit; - DWORD aHolder[3]; - CRITICAL_SECTION aMutex[3]; - HANDLE aCond[1]; -} primitives = { 0 }; - -static int async_os_initialize(void){ - if( !primitives.isInit ){ - primitives.aCond[0] = CreateEvent(NULL, TRUE, FALSE, 0); - if( primitives.aCond[0]==NULL ){ - return 1; - } - InitializeCriticalSection(&primitives.aMutex[0]); - InitializeCriticalSection(&primitives.aMutex[1]); - InitializeCriticalSection(&primitives.aMutex[2]); - primitives.isInit = 1; - } - return 0; -} -static void async_os_shutdown(void){ - if( primitives.isInit ){ - DeleteCriticalSection(&primitives.aMutex[0]); - DeleteCriticalSection(&primitives.aMutex[1]); - DeleteCriticalSection(&primitives.aMutex[2]); - CloseHandle(primitives.aCond[0]); - primitives.isInit = 0; - } -} - -/* The following block contains the Win32 specific code. */ -static void async_mutex_enter(int eMutex){ - assert( eMutex==0 || eMutex==1 || eMutex==2 ); - assert( eMutex!=2 || (!mutex_held(0) && !mutex_held(1) && !mutex_held(2)) ); - assert( eMutex!=1 || (!mutex_held(0) && !mutex_held(1)) ); - assert( eMutex!=0 || (!mutex_held(0)) ); - EnterCriticalSection(&primitives.aMutex[eMutex]); - TESTONLY( primitives.aHolder[eMutex] = GetCurrentThreadId(); ) -} -static void async_mutex_leave(int eMutex){ - assert( eMutex==0 || eMutex==1 || eMutex==2 ); - assert( mutex_held(eMutex) ); - TESTONLY( primitives.aHolder[eMutex] = 0; ) - LeaveCriticalSection(&primitives.aMutex[eMutex]); -} -static void async_cond_wait(int eCond, int eMutex){ - ResetEvent(primitives.aCond[eCond]); - async_mutex_leave(eMutex); - WaitForSingleObject(primitives.aCond[eCond], INFINITE); - async_mutex_enter(eMutex); -} -static void async_cond_signal(int eCond){ - assert( mutex_held(ASYNC_MUTEX_QUEUE) ); - SetEvent(primitives.aCond[eCond]); -} -static void async_sched_yield(void){ - Sleep(0); -} -#else - -/* The following block contains the pthreads specific code. */ -#include <pthread.h> -#include <sched.h> - -#define mutex_held(X) pthread_equal(primitives.aHolder[X], pthread_self()) - -static int async_os_initialize(void) {return 0;} -static void async_os_shutdown(void) {} - -static struct AsyncPrimitives { - pthread_mutex_t aMutex[3]; - pthread_cond_t aCond[1]; - pthread_t aHolder[3]; -} primitives = { - { PTHREAD_MUTEX_INITIALIZER, - PTHREAD_MUTEX_INITIALIZER, - PTHREAD_MUTEX_INITIALIZER - } , { - PTHREAD_COND_INITIALIZER - } , { 0, 0, 0 } -}; - -static void async_mutex_enter(int eMutex){ - assert( eMutex==0 || eMutex==1 || eMutex==2 ); - assert( eMutex!=2 || (!mutex_held(0) && !mutex_held(1) && !mutex_held(2)) ); - assert( eMutex!=1 || (!mutex_held(0) && !mutex_held(1)) ); - assert( eMutex!=0 || (!mutex_held(0)) ); - pthread_mutex_lock(&primitives.aMutex[eMutex]); - TESTONLY( primitives.aHolder[eMutex] = pthread_self(); ) -} -static void async_mutex_leave(int eMutex){ - assert( eMutex==0 || eMutex==1 || eMutex==2 ); - assert( mutex_held(eMutex) ); - TESTONLY( primitives.aHolder[eMutex] = 0; ) - pthread_mutex_unlock(&primitives.aMutex[eMutex]); -} -static void async_cond_wait(int eCond, int eMutex){ - assert( eMutex==0 || eMutex==1 || eMutex==2 ); - assert( mutex_held(eMutex) ); - TESTONLY( primitives.aHolder[eMutex] = 0; ) - pthread_cond_wait(&primitives.aCond[eCond], &primitives.aMutex[eMutex]); - TESTONLY( primitives.aHolder[eMutex] = pthread_self(); ) -} -static void async_cond_signal(int eCond){ - assert( mutex_held(ASYNC_MUTEX_QUEUE) ); - pthread_cond_signal(&primitives.aCond[eCond]); -} -static void async_sched_yield(void){ - sched_yield(); -} -#endif -/* -** End of OS specific code. -*************************************************************************/ - -#define assert_mutex_is_held(X) assert( mutex_held(X) ) - - -#ifndef SQLITE_ASYNC_TWO_FILEHANDLES -/* #define SQLITE_ASYNC_TWO_FILEHANDLES 0 */ -#define SQLITE_ASYNC_TWO_FILEHANDLES 1 -#endif - -/* -** State information is held in the static variable "async" defined -** as the following structure. -** -** Both async.ioError and async.nFile are protected by async.queueMutex. -*/ -static struct TestAsyncStaticData { - AsyncWrite *pQueueFirst; /* Next write operation to be processed */ - AsyncWrite *pQueueLast; /* Last write operation on the list */ - AsyncLock *pLock; /* Linked list of all AsyncLock structures */ - volatile int ioDelay; /* Extra delay between write operations */ - volatile int eHalt; /* One of the SQLITEASYNC_HALT_XXX values */ - volatile int bLockFiles; /* Current value of "lockfiles" parameter */ - int ioError; /* True if an IO error has occurred */ - int nFile; /* Number of open files (from sqlite pov) */ -} async = { 0,0,0,0,0,1,0,0 }; - -/* Possible values of AsyncWrite.op */ -#define ASYNC_NOOP 0 -#define ASYNC_WRITE 1 -#define ASYNC_SYNC 2 -#define ASYNC_TRUNCATE 3 -#define ASYNC_CLOSE 4 -#define ASYNC_DELETE 5 -#define ASYNC_OPENEXCLUSIVE 6 -#define ASYNC_UNLOCK 7 - -/* Names of opcodes. Used for debugging only. -** Make sure these stay in sync with the macros above! -*/ -static const char *azOpcodeName[] = { - "NOOP", "WRITE", "SYNC", "TRUNCATE", "CLOSE", "DELETE", "OPENEX", "UNLOCK" -}; - -/* -** Entries on the write-op queue are instances of the AsyncWrite -** structure, defined here. -** -** The interpretation of the iOffset and nByte variables varies depending -** on the value of AsyncWrite.op: -** -** ASYNC_NOOP: -** No values used. -** -** ASYNC_WRITE: -** iOffset -> Offset in file to write to. -** nByte -> Number of bytes of data to write (pointed to by zBuf). -** -** ASYNC_SYNC: -** nByte -> flags to pass to sqlite3OsSync(). -** -** ASYNC_TRUNCATE: -** iOffset -> Size to truncate file to. -** nByte -> Unused. -** -** ASYNC_CLOSE: -** iOffset -> Unused. -** nByte -> Unused. -** -** ASYNC_DELETE: -** iOffset -> Contains the "syncDir" flag. -** nByte -> Number of bytes of zBuf points to (file name). -** -** ASYNC_OPENEXCLUSIVE: -** iOffset -> Value of "delflag". -** nByte -> Number of bytes of zBuf points to (file name). -** -** ASYNC_UNLOCK: -** nByte -> Argument to sqlite3OsUnlock(). -** -** -** For an ASYNC_WRITE operation, zBuf points to the data to write to the file. -** This space is sqlite3_malloc()d along with the AsyncWrite structure in a -** single blob, so is deleted when sqlite3_free() is called on the parent -** structure. -*/ -struct AsyncWrite { - AsyncFileData *pFileData; /* File to write data to or sync */ - int op; /* One of ASYNC_xxx etc. */ - sqlite_int64 iOffset; /* See above */ - int nByte; /* See above */ - char *zBuf; /* Data to write to file (or NULL if op!=ASYNC_WRITE) */ - AsyncWrite *pNext; /* Next write operation (to any file) */ -}; - -/* -** An instance of this structure is created for each distinct open file -** (i.e. if two handles are opened on the one file, only one of these -** structures is allocated) and stored in the async.aLock hash table. The -** keys for async.aLock are the full pathnames of the opened files. -** -** AsyncLock.pList points to the head of a linked list of AsyncFileLock -** structures, one for each handle currently open on the file. -** -** If the opened file is not a main-database (the SQLITE_OPEN_MAIN_DB is -** not passed to the sqlite3OsOpen() call), or if async.bLockFiles is -** false, variables AsyncLock.pFile and AsyncLock.eLock are never used. -** Otherwise, pFile is a file handle opened on the file in question and -** used to obtain the file-system locks required by database connections -** within this process. -** -** See comments above the asyncLock() function for more details on -** the implementation of database locking used by this backend. -*/ -struct AsyncLock { - char *zFile; - int nFile; - sqlite3_file *pFile; - int eLock; - AsyncFileLock *pList; - AsyncLock *pNext; /* Next in linked list headed by async.pLock */ -}; - -/* -** An instance of the following structure is allocated along with each -** AsyncFileData structure (see AsyncFileData.lock), but is only used if the -** file was opened with the SQLITE_OPEN_MAIN_DB. -*/ -struct AsyncFileLock { - int eLock; /* Internally visible lock state (sqlite pov) */ - int eAsyncLock; /* Lock-state with write-queue unlock */ - AsyncFileLock *pNext; -}; - -/* -** The AsyncFile structure is a subclass of sqlite3_file used for -** asynchronous IO. -** -** All of the actual data for the structure is stored in the structure -** pointed to by AsyncFile.pData, which is allocated as part of the -** sqlite3OsOpen() using sqlite3_malloc(). The reason for this is that the -** lifetime of the AsyncFile structure is ended by the caller after OsClose() -** is called, but the data in AsyncFileData may be required by the -** writer thread after that point. -*/ -struct AsyncFile { - sqlite3_io_methods *pMethod; - AsyncFileData *pData; -}; -struct AsyncFileData { - char *zName; /* Underlying OS filename - used for debugging */ - int nName; /* Number of characters in zName */ - sqlite3_file *pBaseRead; /* Read handle to the underlying Os file */ - sqlite3_file *pBaseWrite; /* Write handle to the underlying Os file */ - AsyncFileLock lock; /* Lock state for this handle */ - AsyncLock *pLock; /* AsyncLock object for this file system entry */ - AsyncWrite closeOp; /* Preallocated close operation */ -}; - -/* -** Add an entry to the end of the global write-op list. pWrite should point -** to an AsyncWrite structure allocated using sqlite3_malloc(). The writer -** thread will call sqlite3_free() to free the structure after the specified -** operation has been completed. -** -** Once an AsyncWrite structure has been added to the list, it becomes the -** property of the writer thread and must not be read or modified by the -** caller. -*/ -static void addAsyncWrite(AsyncWrite *pWrite){ - /* We must hold the queue mutex in order to modify the queue pointers */ - if( pWrite->op!=ASYNC_UNLOCK ){ - async_mutex_enter(ASYNC_MUTEX_QUEUE); - } - - /* Add the record to the end of the write-op queue */ - assert( !pWrite->pNext ); - if( async.pQueueLast ){ - assert( async.pQueueFirst ); - async.pQueueLast->pNext = pWrite; - }else{ - async.pQueueFirst = pWrite; - } - async.pQueueLast = pWrite; - ASYNC_TRACE(("PUSH %p (%s %s %d)\n", pWrite, azOpcodeName[pWrite->op], - pWrite->pFileData ? pWrite->pFileData->zName : "-", pWrite->iOffset)); - - if( pWrite->op==ASYNC_CLOSE ){ - async.nFile--; - } - - /* The writer thread might have been idle because there was nothing - ** on the write-op queue for it to do. So wake it up. */ - async_cond_signal(ASYNC_COND_QUEUE); - - /* Drop the queue mutex */ - if( pWrite->op!=ASYNC_UNLOCK ){ - async_mutex_leave(ASYNC_MUTEX_QUEUE); - } -} - -/* -** Increment async.nFile in a thread-safe manner. -*/ -static void incrOpenFileCount(void){ - /* We must hold the queue mutex in order to modify async.nFile */ - async_mutex_enter(ASYNC_MUTEX_QUEUE); - if( async.nFile==0 ){ - async.ioError = SQLITE_OK; - } - async.nFile++; - async_mutex_leave(ASYNC_MUTEX_QUEUE); -} - -/* -** This is a utility function to allocate and populate a new AsyncWrite -** structure and insert it (via addAsyncWrite() ) into the global list. -*/ -static int addNewAsyncWrite( - AsyncFileData *pFileData, - int op, - sqlite3_int64 iOffset, - int nByte, - const char *zByte -){ - AsyncWrite *p; - if( op!=ASYNC_CLOSE && async.ioError ){ - return async.ioError; - } - p = sqlite3_malloc(sizeof(AsyncWrite) + (zByte?nByte:0)); - if( !p ){ - /* The upper layer does not expect operations like OsWrite() to - ** return SQLITE_NOMEM. This is partly because under normal conditions - ** SQLite is required to do rollback without calling malloc(). So - ** if malloc() fails here, treat it as an I/O error. The above - ** layer knows how to handle that. - */ - return SQLITE_IOERR; - } - p->op = op; - p->iOffset = iOffset; - p->nByte = nByte; - p->pFileData = pFileData; - p->pNext = 0; - if( zByte ){ - p->zBuf = (char *)&p[1]; - memcpy(p->zBuf, zByte, nByte); - }else{ - p->zBuf = 0; - } - addAsyncWrite(p); - return SQLITE_OK; -} - -/* -** Close the file. This just adds an entry to the write-op list, the file is -** not actually closed. -*/ -static int asyncClose(sqlite3_file *pFile){ - AsyncFileData *p = ((AsyncFile *)pFile)->pData; - - /* Unlock the file, if it is locked */ - async_mutex_enter(ASYNC_MUTEX_LOCK); - p->lock.eLock = 0; - async_mutex_leave(ASYNC_MUTEX_LOCK); - - addAsyncWrite(&p->closeOp); - return SQLITE_OK; -} - -/* -** Implementation of sqlite3OsWrite() for asynchronous files. Instead of -** writing to the underlying file, this function adds an entry to the end of -** the global AsyncWrite list. Either SQLITE_OK or SQLITE_NOMEM may be -** returned. -*/ -static int asyncWrite( - sqlite3_file *pFile, - const void *pBuf, - int amt, - sqlite3_int64 iOff -){ - AsyncFileData *p = ((AsyncFile *)pFile)->pData; - return addNewAsyncWrite(p, ASYNC_WRITE, iOff, amt, pBuf); -} - -/* -** Read data from the file. First we read from the filesystem, then adjust -** the contents of the buffer based on ASYNC_WRITE operations in the -** write-op queue. -** -** This method holds the mutex from start to finish. -*/ -static int asyncRead( - sqlite3_file *pFile, - void *zOut, - int iAmt, - sqlite3_int64 iOffset -){ - AsyncFileData *p = ((AsyncFile *)pFile)->pData; - int rc = SQLITE_OK; - sqlite3_int64 filesize = 0; - sqlite3_file *pBase = p->pBaseRead; - sqlite3_int64 iAmt64 = (sqlite3_int64)iAmt; - - /* Grab the write queue mutex for the duration of the call */ - async_mutex_enter(ASYNC_MUTEX_QUEUE); - - /* If an I/O error has previously occurred in this virtual file - ** system, then all subsequent operations fail. - */ - if( async.ioError!=SQLITE_OK ){ - rc = async.ioError; - goto asyncread_out; - } - - if( pBase->pMethods ){ - sqlite3_int64 nRead; - rc = pBase->pMethods->xFileSize(pBase, &filesize); - if( rc!=SQLITE_OK ){ - goto asyncread_out; - } - nRead = MIN(filesize - iOffset, iAmt64); - if( nRead>0 ){ - rc = pBase->pMethods->xRead(pBase, zOut, (int)nRead, iOffset); - ASYNC_TRACE(("READ %s %d bytes at %d\n", p->zName, nRead, iOffset)); - } - } - - if( rc==SQLITE_OK ){ - AsyncWrite *pWrite; - char *zName = p->zName; - - for(pWrite=async.pQueueFirst; pWrite; pWrite = pWrite->pNext){ - if( pWrite->op==ASYNC_WRITE && ( - (pWrite->pFileData==p) || - (zName && pWrite->pFileData->zName==zName) - )){ - sqlite3_int64 nCopy; - sqlite3_int64 nByte64 = (sqlite3_int64)pWrite->nByte; - - /* Set variable iBeginIn to the offset in buffer pWrite->zBuf[] from - ** which data should be copied. Set iBeginOut to the offset within - ** the output buffer to which data should be copied. If either of - ** these offsets is a negative number, set them to 0. - */ - sqlite3_int64 iBeginOut = (pWrite->iOffset-iOffset); - sqlite3_int64 iBeginIn = -iBeginOut; - if( iBeginIn<0 ) iBeginIn = 0; - if( iBeginOut<0 ) iBeginOut = 0; - - filesize = MAX(filesize, pWrite->iOffset+nByte64); - - nCopy = MIN(nByte64-iBeginIn, iAmt64-iBeginOut); - if( nCopy>0 ){ - memcpy(&((char *)zOut)[iBeginOut], &pWrite->zBuf[iBeginIn], (size_t)nCopy); - ASYNC_TRACE(("OVERREAD %d bytes at %d\n", nCopy, iBeginOut+iOffset)); - } - } - } - } - -asyncread_out: - async_mutex_leave(ASYNC_MUTEX_QUEUE); - if( rc==SQLITE_OK && filesize<(iOffset+iAmt) ){ - rc = SQLITE_IOERR_SHORT_READ; - } - return rc; -} - -/* -** Truncate the file to nByte bytes in length. This just adds an entry to -** the write-op list, no IO actually takes place. -*/ -static int asyncTruncate(sqlite3_file *pFile, sqlite3_int64 nByte){ - AsyncFileData *p = ((AsyncFile *)pFile)->pData; - return addNewAsyncWrite(p, ASYNC_TRUNCATE, nByte, 0, 0); -} - -/* -** Sync the file. This just adds an entry to the write-op list, the -** sync() is done later by sqlite3_async_flush(). -*/ -static int asyncSync(sqlite3_file *pFile, int flags){ - AsyncFileData *p = ((AsyncFile *)pFile)->pData; - return addNewAsyncWrite(p, ASYNC_SYNC, 0, flags, 0); -} - -/* -** Read the size of the file. First we read the size of the file system -** entry, then adjust for any ASYNC_WRITE or ASYNC_TRUNCATE operations -** currently in the write-op list. -** -** This method holds the mutex from start to finish. -*/ -int asyncFileSize(sqlite3_file *pFile, sqlite3_int64 *piSize){ - AsyncFileData *p = ((AsyncFile *)pFile)->pData; - int rc = SQLITE_OK; - sqlite3_int64 s = 0; - sqlite3_file *pBase; - - async_mutex_enter(ASYNC_MUTEX_QUEUE); - - /* Read the filesystem size from the base file. If pMethods is NULL, this - ** means the file hasn't been opened yet. In this case all relevant data - ** must be in the write-op queue anyway, so we can omit reading from the - ** file-system. - */ - pBase = p->pBaseRead; - if( pBase->pMethods ){ - rc = pBase->pMethods->xFileSize(pBase, &s); - } - - if( rc==SQLITE_OK ){ - AsyncWrite *pWrite; - for(pWrite=async.pQueueFirst; pWrite; pWrite = pWrite->pNext){ - if( pWrite->op==ASYNC_DELETE - && p->zName - && strcmp(p->zName, pWrite->zBuf)==0 - ){ - s = 0; - }else if( pWrite->pFileData && ( - (pWrite->pFileData==p) - || (p->zName && pWrite->pFileData->zName==p->zName) - )){ - switch( pWrite->op ){ - case ASYNC_WRITE: - s = MAX(pWrite->iOffset + (sqlite3_int64)(pWrite->nByte), s); - break; - case ASYNC_TRUNCATE: - s = MIN(s, pWrite->iOffset); - break; - } - } - } - *piSize = s; - } - async_mutex_leave(ASYNC_MUTEX_QUEUE); - return rc; -} - -/* -** Lock or unlock the actual file-system entry. -*/ -static int getFileLock(AsyncLock *pLock){ - int rc = SQLITE_OK; - AsyncFileLock *pIter; - int eRequired = 0; - - if( pLock->pFile ){ - for(pIter=pLock->pList; pIter; pIter=pIter->pNext){ - assert(pIter->eAsyncLock>=pIter->eLock); - if( pIter->eAsyncLock>eRequired ){ - eRequired = pIter->eAsyncLock; - assert(eRequired>=0 && eRequired<=SQLITE_LOCK_EXCLUSIVE); - } - } - - if( eRequired>pLock->eLock ){ - rc = pLock->pFile->pMethods->xLock(pLock->pFile, eRequired); - if( rc==SQLITE_OK ){ - pLock->eLock = eRequired; - } - } - else if( eRequired<pLock->eLock && eRequired<=SQLITE_LOCK_SHARED ){ - rc = pLock->pFile->pMethods->xUnlock(pLock->pFile, eRequired); - if( rc==SQLITE_OK ){ - pLock->eLock = eRequired; - } - } - } - - return rc; -} - -/* -** Return the AsyncLock structure from the global async.pLock list -** associated with the file-system entry identified by path zName -** (a string of nName bytes). If no such structure exists, return 0. -*/ -static AsyncLock *findLock(const char *zName, int nName){ - AsyncLock *p = async.pLock; - while( p && (p->nFile!=nName || memcmp(p->zFile, zName, nName)) ){ - p = p->pNext; - } - return p; -} - -/* -** The following two methods - asyncLock() and asyncUnlock() - are used -** to obtain and release locks on database files opened with the -** asynchronous backend. -*/ -static int asyncLock(sqlite3_file *pFile, int eLock){ - int rc = SQLITE_OK; - AsyncFileData *p = ((AsyncFile *)pFile)->pData; - - if( p->zName ){ - async_mutex_enter(ASYNC_MUTEX_LOCK); - if( p->lock.eLock<eLock ){ - AsyncLock *pLock = p->pLock; - AsyncFileLock *pIter; - assert(pLock && pLock->pList); - for(pIter=pLock->pList; pIter; pIter=pIter->pNext){ - if( pIter!=&p->lock && ( - (eLock==SQLITE_LOCK_EXCLUSIVE && pIter->eLock>=SQLITE_LOCK_SHARED) || - (eLock==SQLITE_LOCK_PENDING && pIter->eLock>=SQLITE_LOCK_RESERVED) || - (eLock==SQLITE_LOCK_RESERVED && pIter->eLock>=SQLITE_LOCK_RESERVED) || - (eLock==SQLITE_LOCK_SHARED && pIter->eLock>=SQLITE_LOCK_PENDING) - )){ - rc = SQLITE_BUSY; - } - } - if( rc==SQLITE_OK ){ - p->lock.eLock = eLock; - p->lock.eAsyncLock = MAX(p->lock.eAsyncLock, eLock); - } - assert(p->lock.eAsyncLock>=p->lock.eLock); - if( rc==SQLITE_OK ){ - rc = getFileLock(pLock); - } - } - async_mutex_leave(ASYNC_MUTEX_LOCK); - } - - ASYNC_TRACE(("LOCK %d (%s) rc=%d\n", eLock, p->zName, rc)); - return rc; -} -static int asyncUnlock(sqlite3_file *pFile, int eLock){ - int rc = SQLITE_OK; - AsyncFileData *p = ((AsyncFile *)pFile)->pData; - if( p->zName ){ - AsyncFileLock *pLock = &p->lock; - async_mutex_enter(ASYNC_MUTEX_QUEUE); - async_mutex_enter(ASYNC_MUTEX_LOCK); - pLock->eLock = MIN(pLock->eLock, eLock); - rc = addNewAsyncWrite(p, ASYNC_UNLOCK, 0, eLock, 0); - async_mutex_leave(ASYNC_MUTEX_LOCK); - async_mutex_leave(ASYNC_MUTEX_QUEUE); - } - return rc; -} - -/* -** This function is called when the pager layer first opens a database file -** and is checking for a hot-journal. -*/ -static int asyncCheckReservedLock(sqlite3_file *pFile, int *pResOut){ - int ret = 0; - AsyncFileLock *pIter; - AsyncFileData *p = ((AsyncFile *)pFile)->pData; - - async_mutex_enter(ASYNC_MUTEX_LOCK); - for(pIter=p->pLock->pList; pIter; pIter=pIter->pNext){ - if( pIter->eLock>=SQLITE_LOCK_RESERVED ){ - ret = 1; - break; - } - } - async_mutex_leave(ASYNC_MUTEX_LOCK); - - ASYNC_TRACE(("CHECK-LOCK %d (%s)\n", ret, p->zName)); - *pResOut = ret; - return SQLITE_OK; -} - -/* -** sqlite3_file_control() implementation. -*/ -static int asyncFileControl(sqlite3_file *id, int op, void *pArg){ - switch( op ){ - case SQLITE_FCNTL_LOCKSTATE: { - async_mutex_enter(ASYNC_MUTEX_LOCK); - *(int*)pArg = ((AsyncFile*)id)->pData->lock.eLock; - async_mutex_leave(ASYNC_MUTEX_LOCK); - return SQLITE_OK; - } - } - return SQLITE_NOTFOUND; -} - -/* -** Return the device characteristics and sector-size of the device. It -** is tricky to implement these correctly, as this backend might -** not have an open file handle at this point. -*/ -static int asyncSectorSize(sqlite3_file *pFile){ - UNUSED_PARAMETER(pFile); - return 512; -} -static int asyncDeviceCharacteristics(sqlite3_file *pFile){ - UNUSED_PARAMETER(pFile); - return 0; -} - -static int unlinkAsyncFile(AsyncFileData *pData){ - AsyncFileLock **ppIter; - int rc = SQLITE_OK; - - if( pData->zName ){ - AsyncLock *pLock = pData->pLock; - for(ppIter=&pLock->pList; *ppIter; ppIter=&((*ppIter)->pNext)){ - if( (*ppIter)==&pData->lock ){ - *ppIter = pData->lock.pNext; - break; - } - } - if( !pLock->pList ){ - AsyncLock **pp; - if( pLock->pFile ){ - pLock->pFile->pMethods->xClose(pLock->pFile); - } - for(pp=&async.pLock; *pp!=pLock; pp=&((*pp)->pNext)); - *pp = pLock->pNext; - sqlite3_free(pLock); - }else{ - rc = getFileLock(pLock); - } - } - - return rc; -} - -/* -** The parameter passed to this function is a copy of a 'flags' parameter -** passed to this modules xOpen() method. This function returns true -** if the file should be opened asynchronously, or false if it should -** be opened immediately. -** -** If the file is to be opened asynchronously, then asyncOpen() will add -** an entry to the event queue and the file will not actually be opened -** until the event is processed. Otherwise, the file is opened directly -** by the caller. -*/ -static int doAsynchronousOpen(int flags){ - return (flags&SQLITE_OPEN_CREATE) && ( - (flags&SQLITE_OPEN_MAIN_JOURNAL) || - (flags&SQLITE_OPEN_TEMP_JOURNAL) || - (flags&SQLITE_OPEN_DELETEONCLOSE) - ); -} - -/* -** Open a file. -*/ -static int asyncOpen( - sqlite3_vfs *pAsyncVfs, - const char *zName, - sqlite3_file *pFile, - int flags, - int *pOutFlags -){ - static sqlite3_io_methods async_methods = { - 1, /* iVersion */ - asyncClose, /* xClose */ - asyncRead, /* xRead */ - asyncWrite, /* xWrite */ - asyncTruncate, /* xTruncate */ - asyncSync, /* xSync */ - asyncFileSize, /* xFileSize */ - asyncLock, /* xLock */ - asyncUnlock, /* xUnlock */ - asyncCheckReservedLock, /* xCheckReservedLock */ - asyncFileControl, /* xFileControl */ - asyncSectorSize, /* xSectorSize */ - asyncDeviceCharacteristics /* xDeviceCharacteristics */ - }; - - sqlite3_vfs *pVfs = (sqlite3_vfs *)pAsyncVfs->pAppData; - AsyncFile *p = (AsyncFile *)pFile; - int nName = 0; - int rc = SQLITE_OK; - int nByte; - AsyncFileData *pData; - AsyncLock *pLock = 0; - char *z; - int isAsyncOpen = doAsynchronousOpen(flags); - - /* If zName is NULL, then the upper layer is requesting an anonymous file. - ** Otherwise, allocate enough space to make a copy of the file name (along - ** with the second nul-terminator byte required by xOpen). - */ - if( zName ){ - nName = (int)strlen(zName); - } - - nByte = ( - sizeof(AsyncFileData) + /* AsyncFileData structure */ - 2 * pVfs->szOsFile + /* AsyncFileData.pBaseRead and pBaseWrite */ - nName + 2 /* AsyncFileData.zName */ - ); - z = sqlite3_malloc(nByte); - if( !z ){ - return SQLITE_NOMEM; - } - memset(z, 0, nByte); - pData = (AsyncFileData*)z; - z += sizeof(pData[0]); - pData->pBaseRead = (sqlite3_file*)z; - z += pVfs->szOsFile; - pData->pBaseWrite = (sqlite3_file*)z; - pData->closeOp.pFileData = pData; - pData->closeOp.op = ASYNC_CLOSE; - - if( zName ){ - z += pVfs->szOsFile; - pData->zName = z; - pData->nName = nName; - memcpy(pData->zName, zName, nName); - } - - if( !isAsyncOpen ){ - int flagsout; - rc = pVfs->xOpen(pVfs, pData->zName, pData->pBaseRead, flags, &flagsout); - if( rc==SQLITE_OK - && (flagsout&SQLITE_OPEN_READWRITE) - && (flags&SQLITE_OPEN_EXCLUSIVE)==0 - ){ - rc = pVfs->xOpen(pVfs, pData->zName, pData->pBaseWrite, flags, 0); - } - if( pOutFlags ){ - *pOutFlags = flagsout; - } - } - - async_mutex_enter(ASYNC_MUTEX_LOCK); - - if( zName && rc==SQLITE_OK ){ - pLock = findLock(pData->zName, pData->nName); - if( !pLock ){ - int nByte = pVfs->szOsFile + sizeof(AsyncLock) + pData->nName + 1; - pLock = (AsyncLock *)sqlite3_malloc(nByte); - if( pLock ){ - memset(pLock, 0, nByte); - if( async.bLockFiles && (flags&SQLITE_OPEN_MAIN_DB) ){ - pLock->pFile = (sqlite3_file *)&pLock[1]; - rc = pVfs->xOpen(pVfs, pData->zName, pLock->pFile, flags, 0); - if( rc!=SQLITE_OK ){ - sqlite3_free(pLock); - pLock = 0; - } - } - if( pLock ){ - pLock->nFile = pData->nName; - pLock->zFile = &((char *)(&pLock[1]))[pVfs->szOsFile]; - memcpy(pLock->zFile, pData->zName, pLock->nFile); - pLock->pNext = async.pLock; - async.pLock = pLock; - } - }else{ - rc = SQLITE_NOMEM; - } - } - } - - if( rc==SQLITE_OK ){ - p->pMethod = &async_methods; - p->pData = pData; - - /* Link AsyncFileData.lock into the linked list of - ** AsyncFileLock structures for this file. - */ - if( zName ){ - pData->lock.pNext = pLock->pList; - pLock->pList = &pData->lock; - pData->zName = pLock->zFile; - } - }else{ - if( pData->pBaseRead->pMethods ){ - pData->pBaseRead->pMethods->xClose(pData->pBaseRead); - } - if( pData->pBaseWrite->pMethods ){ - pData->pBaseWrite->pMethods->xClose(pData->pBaseWrite); - } - sqlite3_free(pData); - } - - async_mutex_leave(ASYNC_MUTEX_LOCK); - - if( rc==SQLITE_OK ){ - pData->pLock = pLock; - } - - if( rc==SQLITE_OK && isAsyncOpen ){ - rc = addNewAsyncWrite(pData, ASYNC_OPENEXCLUSIVE, (sqlite3_int64)flags,0,0); - if( rc==SQLITE_OK ){ - if( pOutFlags ) *pOutFlags = flags; - }else{ - async_mutex_enter(ASYNC_MUTEX_LOCK); - unlinkAsyncFile(pData); - async_mutex_leave(ASYNC_MUTEX_LOCK); - sqlite3_free(pData); - } - } - if( rc!=SQLITE_OK ){ - p->pMethod = 0; - }else{ - incrOpenFileCount(); - } - - return rc; -} - -/* -** Implementation of sqlite3OsDelete. Add an entry to the end of the -** write-op queue to perform the delete. -*/ -static int asyncDelete(sqlite3_vfs *pAsyncVfs, const char *z, int syncDir){ - UNUSED_PARAMETER(pAsyncVfs); - return addNewAsyncWrite(0, ASYNC_DELETE, syncDir, (int)strlen(z)+1, z); -} - -/* -** Implementation of sqlite3OsAccess. This method holds the mutex from -** start to finish. -*/ -static int asyncAccess( - sqlite3_vfs *pAsyncVfs, - const char *zName, - int flags, - int *pResOut -){ - int rc; - int ret; - AsyncWrite *p; - sqlite3_vfs *pVfs = (sqlite3_vfs *)pAsyncVfs->pAppData; - - assert(flags==SQLITE_ACCESS_READWRITE - || flags==SQLITE_ACCESS_READ - || flags==SQLITE_ACCESS_EXISTS - ); - - async_mutex_enter(ASYNC_MUTEX_QUEUE); - rc = pVfs->xAccess(pVfs, zName, flags, &ret); - if( rc==SQLITE_OK && flags==SQLITE_ACCESS_EXISTS ){ - for(p=async.pQueueFirst; p; p = p->pNext){ - if( p->op==ASYNC_DELETE && 0==strcmp(p->zBuf, zName) ){ - ret = 0; - }else if( p->op==ASYNC_OPENEXCLUSIVE - && p->pFileData->zName - && 0==strcmp(p->pFileData->zName, zName) - ){ - ret = 1; - } - } - } - ASYNC_TRACE(("ACCESS(%s): %s = %d\n", - flags==SQLITE_ACCESS_READWRITE?"read-write": - flags==SQLITE_ACCESS_READ?"read":"exists" - , zName, ret) - ); - async_mutex_leave(ASYNC_MUTEX_QUEUE); - *pResOut = ret; - return rc; -} - -/* -** Fill in zPathOut with the full path to the file identified by zPath. -*/ -static int asyncFullPathname( - sqlite3_vfs *pAsyncVfs, - const char *zPath, - int nPathOut, - char *zPathOut -){ - int rc; - sqlite3_vfs *pVfs = (sqlite3_vfs *)pAsyncVfs->pAppData; - rc = pVfs->xFullPathname(pVfs, zPath, nPathOut, zPathOut); - - /* Because of the way intra-process file locking works, this backend - ** needs to return a canonical path. The following block assumes the - ** file-system uses unix style paths. - */ - if( rc==SQLITE_OK ){ - int i, j; - char *z = zPathOut; - int n = (int)strlen(z); - while( n>1 && z[n-1]=='/' ){ n--; } - for(i=j=0; i<n; i++){ - if( z[i]=='/' ){ - if( z[i+1]=='/' ) continue; - if( z[i+1]=='.' && i+2<n && z[i+2]=='/' ){ - i += 1; - continue; - } - if( z[i+1]=='.' && i+3<n && z[i+2]=='.' && z[i+3]=='/' ){ - while( j>0 && z[j-1]!='/' ){ j--; } - if( j>0 ){ j--; } - i += 2; - continue; - } - } - z[j++] = z[i]; - } - z[j] = 0; - } - - return rc; -} -static void *asyncDlOpen(sqlite3_vfs *pAsyncVfs, const char *zPath){ - sqlite3_vfs *pVfs = (sqlite3_vfs *)pAsyncVfs->pAppData; - return pVfs->xDlOpen(pVfs, zPath); -} -static void asyncDlError(sqlite3_vfs *pAsyncVfs, int nByte, char *zErrMsg){ - sqlite3_vfs *pVfs = (sqlite3_vfs *)pAsyncVfs->pAppData; - pVfs->xDlError(pVfs, nByte, zErrMsg); -} -static void (*asyncDlSym( - sqlite3_vfs *pAsyncVfs, - void *pHandle, - const char *zSymbol -))(void){ - sqlite3_vfs *pVfs = (sqlite3_vfs *)pAsyncVfs->pAppData; - return pVfs->xDlSym(pVfs, pHandle, zSymbol); -} -static void asyncDlClose(sqlite3_vfs *pAsyncVfs, void *pHandle){ - sqlite3_vfs *pVfs = (sqlite3_vfs *)pAsyncVfs->pAppData; - pVfs->xDlClose(pVfs, pHandle); -} -static int asyncRandomness(sqlite3_vfs *pAsyncVfs, int nByte, char *zBufOut){ - sqlite3_vfs *pVfs = (sqlite3_vfs *)pAsyncVfs->pAppData; - return pVfs->xRandomness(pVfs, nByte, zBufOut); -} -static int asyncSleep(sqlite3_vfs *pAsyncVfs, int nMicro){ - sqlite3_vfs *pVfs = (sqlite3_vfs *)pAsyncVfs->pAppData; - return pVfs->xSleep(pVfs, nMicro); -} -static int asyncCurrentTime(sqlite3_vfs *pAsyncVfs, double *pTimeOut){ - sqlite3_vfs *pVfs = (sqlite3_vfs *)pAsyncVfs->pAppData; - return pVfs->xCurrentTime(pVfs, pTimeOut); -} - -static sqlite3_vfs async_vfs = { - 1, /* iVersion */ - sizeof(AsyncFile), /* szOsFile */ - 0, /* mxPathname */ - 0, /* pNext */ - SQLITEASYNC_VFSNAME, /* zName */ - 0, /* pAppData */ - asyncOpen, /* xOpen */ - asyncDelete, /* xDelete */ - asyncAccess, /* xAccess */ - asyncFullPathname, /* xFullPathname */ - asyncDlOpen, /* xDlOpen */ - asyncDlError, /* xDlError */ - asyncDlSym, /* xDlSym */ - asyncDlClose, /* xDlClose */ - asyncRandomness, /* xDlError */ - asyncSleep, /* xDlSym */ - asyncCurrentTime /* xDlClose */ -}; - -/* -** This procedure runs in a separate thread, reading messages off of the -** write queue and processing them one by one. -** -** If async.writerHaltNow is true, then this procedure exits -** after processing a single message. -** -** If async.writerHaltWhenIdle is true, then this procedure exits when -** the write queue is empty. -** -** If both of the above variables are false, this procedure runs -** indefinately, waiting for operations to be added to the write queue -** and processing them in the order in which they arrive. -** -** An artifical delay of async.ioDelay milliseconds is inserted before -** each write operation in order to simulate the effect of a slow disk. -** -** Only one instance of this procedure may be running at a time. -*/ -static void asyncWriterThread(void){ - sqlite3_vfs *pVfs = (sqlite3_vfs *)(async_vfs.pAppData); - AsyncWrite *p = 0; - int rc = SQLITE_OK; - int holdingMutex = 0; - - async_mutex_enter(ASYNC_MUTEX_WRITER); - - while( async.eHalt!=SQLITEASYNC_HALT_NOW ){ - int doNotFree = 0; - sqlite3_file *pBase = 0; - - if( !holdingMutex ){ - async_mutex_enter(ASYNC_MUTEX_QUEUE); - } - while( (p = async.pQueueFirst)==0 ){ - if( async.eHalt!=SQLITEASYNC_HALT_NEVER ){ - async_mutex_leave(ASYNC_MUTEX_QUEUE); - break; - }else{ - ASYNC_TRACE(("IDLE\n")); - async_cond_wait(ASYNC_COND_QUEUE, ASYNC_MUTEX_QUEUE); - ASYNC_TRACE(("WAKEUP\n")); - } - } - if( p==0 ) break; - holdingMutex = 1; - - /* Right now this thread is holding the mutex on the write-op queue. - ** Variable 'p' points to the first entry in the write-op queue. In - ** the general case, we hold on to the mutex for the entire body of - ** the loop. - ** - ** However in the cases enumerated below, we relinquish the mutex, - ** perform the IO, and then re-request the mutex before removing 'p' from - ** the head of the write-op queue. The idea is to increase concurrency with - ** sqlite threads. - ** - ** * An ASYNC_CLOSE operation. - ** * An ASYNC_OPENEXCLUSIVE operation. For this one, we relinquish - ** the mutex, call the underlying xOpenExclusive() function, then - ** re-aquire the mutex before seting the AsyncFile.pBaseRead - ** variable. - ** * ASYNC_SYNC and ASYNC_WRITE operations, if - ** SQLITE_ASYNC_TWO_FILEHANDLES was set at compile time and two - ** file-handles are open for the particular file being "synced". - */ - if( async.ioError!=SQLITE_OK && p->op!=ASYNC_CLOSE ){ - p->op = ASYNC_NOOP; - } - if( p->pFileData ){ - pBase = p->pFileData->pBaseWrite; - if( - p->op==ASYNC_CLOSE || - p->op==ASYNC_OPENEXCLUSIVE || - (pBase->pMethods && (p->op==ASYNC_SYNC || p->op==ASYNC_WRITE) ) - ){ - async_mutex_leave(ASYNC_MUTEX_QUEUE); - holdingMutex = 0; - } - if( !pBase->pMethods ){ - pBase = p->pFileData->pBaseRead; - } - } - - switch( p->op ){ - case ASYNC_NOOP: - break; - - case ASYNC_WRITE: - assert( pBase ); - ASYNC_TRACE(("WRITE %s %d bytes at %d\n", - p->pFileData->zName, p->nByte, p->iOffset)); - rc = pBase->pMethods->xWrite(pBase, (void *)(p->zBuf), p->nByte, p->iOffset); - break; - - case ASYNC_SYNC: - assert( pBase ); - ASYNC_TRACE(("SYNC %s\n", p->pFileData->zName)); - rc = pBase->pMethods->xSync(pBase, p->nByte); - break; - - case ASYNC_TRUNCATE: - assert( pBase ); - ASYNC_TRACE(("TRUNCATE %s to %d bytes\n", - p->pFileData->zName, p->iOffset)); - rc = pBase->pMethods->xTruncate(pBase, p->iOffset); - break; - - case ASYNC_CLOSE: { - AsyncFileData *pData = p->pFileData; - ASYNC_TRACE(("CLOSE %s\n", p->pFileData->zName)); - if( pData->pBaseWrite->pMethods ){ - pData->pBaseWrite->pMethods->xClose(pData->pBaseWrite); - } - if( pData->pBaseRead->pMethods ){ - pData->pBaseRead->pMethods->xClose(pData->pBaseRead); - } - - /* Unlink AsyncFileData.lock from the linked list of AsyncFileLock - ** structures for this file. Obtain the async.lockMutex mutex - ** before doing so. - */ - async_mutex_enter(ASYNC_MUTEX_LOCK); - rc = unlinkAsyncFile(pData); - async_mutex_leave(ASYNC_MUTEX_LOCK); - - if( !holdingMutex ){ - async_mutex_enter(ASYNC_MUTEX_QUEUE); - holdingMutex = 1; - } - assert_mutex_is_held(ASYNC_MUTEX_QUEUE); - async.pQueueFirst = p->pNext; - sqlite3_free(pData); - doNotFree = 1; - break; - } - - case ASYNC_UNLOCK: { - AsyncWrite *pIter; - AsyncFileData *pData = p->pFileData; - int eLock = p->nByte; - - /* When a file is locked by SQLite using the async backend, it is - ** locked within the 'real' file-system synchronously. When it is - ** unlocked, an ASYNC_UNLOCK event is added to the write-queue to - ** unlock the file asynchronously. The design of the async backend - ** requires that the 'real' file-system file be locked from the - ** time that SQLite first locks it (and probably reads from it) - ** until all asynchronous write events that were scheduled before - ** SQLite unlocked the file have been processed. - ** - ** This is more complex if SQLite locks and unlocks the file multiple - ** times in quick succession. For example, if SQLite does: - ** - ** lock, write, unlock, lock, write, unlock - ** - ** Each "lock" operation locks the file immediately. Each "write" - ** and "unlock" operation adds an event to the event queue. If the - ** second "lock" operation is performed before the first "unlock" - ** operation has been processed asynchronously, then the first - ** "unlock" cannot be safely processed as is, since this would mean - ** the file was unlocked when the second "write" operation is - ** processed. To work around this, when processing an ASYNC_UNLOCK - ** operation, SQLite: - ** - ** 1) Unlocks the file to the minimum of the argument passed to - ** the xUnlock() call and the current lock from SQLite's point - ** of view, and - ** - ** 2) Only unlocks the file at all if this event is the last - ** ASYNC_UNLOCK event on this file in the write-queue. - */ - assert( holdingMutex==1 ); - assert( async.pQueueFirst==p ); - for(pIter=async.pQueueFirst->pNext; pIter; pIter=pIter->pNext){ - if( pIter->pFileData==pData && pIter->op==ASYNC_UNLOCK ) break; - } - if( !pIter ){ - async_mutex_enter(ASYNC_MUTEX_LOCK); - pData->lock.eAsyncLock = MIN( - pData->lock.eAsyncLock, MAX(pData->lock.eLock, eLock) - ); - assert(pData->lock.eAsyncLock>=pData->lock.eLock); - rc = getFileLock(pData->pLock); - async_mutex_leave(ASYNC_MUTEX_LOCK); - } - break; - } - - case ASYNC_DELETE: - ASYNC_TRACE(("DELETE %s\n", p->zBuf)); - rc = pVfs->xDelete(pVfs, p->zBuf, (int)p->iOffset); - break; - - case ASYNC_OPENEXCLUSIVE: { - int flags = (int)p->iOffset; - AsyncFileData *pData = p->pFileData; - ASYNC_TRACE(("OPEN %s flags=%d\n", p->zBuf, (int)p->iOffset)); - assert(pData->pBaseRead->pMethods==0 && pData->pBaseWrite->pMethods==0); - rc = pVfs->xOpen(pVfs, pData->zName, pData->pBaseRead, flags, 0); - assert( holdingMutex==0 ); - async_mutex_enter(ASYNC_MUTEX_QUEUE); - holdingMutex = 1; - break; - } - - default: assert(!"Illegal value for AsyncWrite.op"); - } - - /* If we didn't hang on to the mutex during the IO op, obtain it now - ** so that the AsyncWrite structure can be safely removed from the - ** global write-op queue. - */ - if( !holdingMutex ){ - async_mutex_enter(ASYNC_MUTEX_QUEUE); - holdingMutex = 1; - } - /* ASYNC_TRACE(("UNLINK %p\n", p)); */ - if( p==async.pQueueLast ){ - async.pQueueLast = 0; - } - if( !doNotFree ){ - assert_mutex_is_held(ASYNC_MUTEX_QUEUE); - async.pQueueFirst = p->pNext; - sqlite3_free(p); - } - assert( holdingMutex ); - - /* An IO error has occurred. We cannot report the error back to the - ** connection that requested the I/O since the error happened - ** asynchronously. The connection has already moved on. There - ** really is nobody to report the error to. - ** - ** The file for which the error occurred may have been a database or - ** journal file. Regardless, none of the currently queued operations - ** associated with the same database should now be performed. Nor should - ** any subsequently requested IO on either a database or journal file - ** handle for the same database be accepted until the main database - ** file handle has been closed and reopened. - ** - ** Furthermore, no further IO should be queued or performed on any file - ** handle associated with a database that may have been part of a - ** multi-file transaction that included the database associated with - ** the IO error (i.e. a database ATTACHed to the same handle at some - ** point in time). - */ - if( rc!=SQLITE_OK ){ - async.ioError = rc; - } - - if( async.ioError && !async.pQueueFirst ){ - async_mutex_enter(ASYNC_MUTEX_LOCK); - if( 0==async.pLock ){ - async.ioError = SQLITE_OK; - } - async_mutex_leave(ASYNC_MUTEX_LOCK); - } - - /* Drop the queue mutex before continuing to the next write operation - ** in order to give other threads a chance to work with the write queue. - */ - if( !async.pQueueFirst || !async.ioError ){ - async_mutex_leave(ASYNC_MUTEX_QUEUE); - holdingMutex = 0; - if( async.ioDelay>0 ){ - pVfs->xSleep(pVfs, async.ioDelay*1000); - }else{ - async_sched_yield(); - } - } - } - - async_mutex_leave(ASYNC_MUTEX_WRITER); - return; -} - -/* -** Install the asynchronous VFS. -*/ -int sqlite3async_initialize(const char *zParent, int isDefault){ - int rc = SQLITE_OK; - if( async_vfs.pAppData==0 ){ - sqlite3_vfs *pParent = sqlite3_vfs_find(zParent); - if( !pParent || async_os_initialize() ){ - rc = SQLITE_ERROR; - }else if( SQLITE_OK!=(rc = sqlite3_vfs_register(&async_vfs, isDefault)) ){ - async_os_shutdown(); - }else{ - async_vfs.pAppData = (void *)pParent; - async_vfs.mxPathname = ((sqlite3_vfs *)async_vfs.pAppData)->mxPathname; - } - } - return rc; -} - -/* -** Uninstall the asynchronous VFS. -*/ -void sqlite3async_shutdown(void){ - if( async_vfs.pAppData ){ - async_os_shutdown(); - sqlite3_vfs_unregister((sqlite3_vfs *)&async_vfs); - async_vfs.pAppData = 0; - } -} - -/* -** Process events on the write-queue. -*/ -void sqlite3async_run(void){ - asyncWriterThread(); -} - -/* -** Control/configure the asynchronous IO system. -*/ -int sqlite3async_control(int op, ...){ - va_list ap; - va_start(ap, op); - switch( op ){ - case SQLITEASYNC_HALT: { - int eWhen = va_arg(ap, int); - if( eWhen!=SQLITEASYNC_HALT_NEVER - && eWhen!=SQLITEASYNC_HALT_NOW - && eWhen!=SQLITEASYNC_HALT_IDLE - ){ - return SQLITE_MISUSE; - } - async.eHalt = eWhen; - async_mutex_enter(ASYNC_MUTEX_QUEUE); - async_cond_signal(ASYNC_COND_QUEUE); - async_mutex_leave(ASYNC_MUTEX_QUEUE); - break; - } - - case SQLITEASYNC_DELAY: { - int iDelay = va_arg(ap, int); - if( iDelay<0 ){ - return SQLITE_MISUSE; - } - async.ioDelay = iDelay; - break; - } - - case SQLITEASYNC_LOCKFILES: { - int bLock = va_arg(ap, int); - async_mutex_enter(ASYNC_MUTEX_QUEUE); - if( async.nFile || async.pQueueFirst ){ - async_mutex_leave(ASYNC_MUTEX_QUEUE); - return SQLITE_MISUSE; - } - async.bLockFiles = bLock; - async_mutex_leave(ASYNC_MUTEX_QUEUE); - break; - } - - case SQLITEASYNC_GET_HALT: { - int *peWhen = va_arg(ap, int *); - *peWhen = async.eHalt; - break; - } - case SQLITEASYNC_GET_DELAY: { - int *piDelay = va_arg(ap, int *); - *piDelay = async.ioDelay; - break; - } - case SQLITEASYNC_GET_LOCKFILES: { - int *piDelay = va_arg(ap, int *); - *piDelay = async.bLockFiles; - break; - } - - default: - return SQLITE_ERROR; - } - return SQLITE_OK; -} - -#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_ASYNCIO) */ - |