+++ /dev/null
-/*
-** 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);
- if( rc==SQLITE_IOERR_DELETE_NOENT ) rc = SQLITE_OK;
- 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, ...){
- int rc = SQLITE_OK;
- 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
- ){
- rc = SQLITE_MISUSE;
- break;
- }
- 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 ){
- rc = SQLITE_MISUSE;
- break;
- }
- 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);
- rc = SQLITE_MISUSE;
- break;
- }
- 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:
- rc = SQLITE_ERROR;
- break;
- }
- va_end(ap);
- return rc;
-}
-
-#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_ASYNCIO) */
projects / thirdparty / sqlite.git / commitdiff
