1702 lines
53 KiB
C
1702 lines
53 KiB
C
/*
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** 2005 December 14
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**
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** The author disclaims copyright to this source code. In place of
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** a legal notice, here is a blessing:
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**
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** May you do good and not evil.
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** May you find forgiveness for yourself and forgive others.
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** May you share freely, never taking more than you give.
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**
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*************************************************************************
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**
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** $Id: sqlite3async.c,v 1.7 2009/07/18 11:52:04 danielk1977 Exp $
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**
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** This file contains the implementation of an asynchronous IO backend
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** for SQLite.
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*/
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#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_ASYNCIO)
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#include "sqlite3async.h"
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#include "sqlite3.h"
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#include <stdarg.h>
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#include <string.h>
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#include <assert.h>
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/* Useful macros used in several places */
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#define MIN(x,y) ((x)<(y)?(x):(y))
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#define MAX(x,y) ((x)>(y)?(x):(y))
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#ifndef SQLITE_AMALGAMATION
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/* Macro to mark parameters as unused and silence compiler warnings. */
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#define UNUSED_PARAMETER(x) (void)(x)
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#endif
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/* Forward references */
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typedef struct AsyncWrite AsyncWrite;
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typedef struct AsyncFile AsyncFile;
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typedef struct AsyncFileData AsyncFileData;
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typedef struct AsyncFileLock AsyncFileLock;
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typedef struct AsyncLock AsyncLock;
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/* Enable for debugging */
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#ifndef NDEBUG
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#include <stdio.h>
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static int sqlite3async_trace = 0;
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# define ASYNC_TRACE(X) if( sqlite3async_trace ) asyncTrace X
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static void asyncTrace(const char *zFormat, ...){
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char *z;
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va_list ap;
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va_start(ap, zFormat);
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z = sqlite3_vmprintf(zFormat, ap);
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va_end(ap);
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fprintf(stderr, "[%d] %s", 0 /* (int)pthread_self() */, z);
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sqlite3_free(z);
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}
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#else
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# define ASYNC_TRACE(X)
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#endif
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/*
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** THREAD SAFETY NOTES
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**
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** Basic rules:
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**
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** * Both read and write access to the global write-op queue must be
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** protected by the async.queueMutex. As are the async.ioError and
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** async.nFile variables.
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**
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** * The async.pLock list and all AsyncLock and AsyncFileLock
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** structures must be protected by the async.lockMutex mutex.
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**
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** * The file handles from the underlying system are not assumed to
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** be thread safe.
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**
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** * See the last two paragraphs under "The Writer Thread" for
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** an assumption to do with file-handle synchronization by the Os.
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**
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** Deadlock prevention:
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**
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** There are three mutex used by the system: the "writer" mutex,
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** the "queue" mutex and the "lock" mutex. Rules are:
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**
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** * It is illegal to block on the writer mutex when any other mutex
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** are held, and
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**
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** * It is illegal to block on the queue mutex when the lock mutex
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** is held.
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**
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** i.e. mutex's must be grabbed in the order "writer", "queue", "lock".
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**
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** File system operations (invoked by SQLite thread):
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**
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** xOpen
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** xDelete
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** xFileExists
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**
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** File handle operations (invoked by SQLite thread):
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**
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** asyncWrite, asyncClose, asyncTruncate, asyncSync
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**
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** The operations above add an entry to the global write-op list. They
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** prepare the entry, acquire the async.queueMutex momentarily while
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** list pointers are manipulated to insert the new entry, then release
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** the mutex and signal the writer thread to wake up in case it happens
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** to be asleep.
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**
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**
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** asyncRead, asyncFileSize.
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**
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** Read operations. Both of these read from both the underlying file
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** first then adjust their result based on pending writes in the
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** write-op queue. So async.queueMutex is held for the duration
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** of these operations to prevent other threads from changing the
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** queue in mid operation.
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**
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**
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** asyncLock, asyncUnlock, asyncCheckReservedLock
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**
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** These primitives implement in-process locking using a hash table
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** on the file name. Files are locked correctly for connections coming
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** from the same process. But other processes cannot see these locks
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** and will therefore not honor them.
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**
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**
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** The writer thread:
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**
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** The async.writerMutex is used to make sure only there is only
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** a single writer thread running at a time.
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**
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** Inside the writer thread is a loop that works like this:
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**
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** WHILE (write-op list is not empty)
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** Do IO operation at head of write-op list
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** Remove entry from head of write-op list
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** END WHILE
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**
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** The async.queueMutex is always held during the <write-op list is
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** not empty> test, and when the entry is removed from the head
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** of the write-op list. Sometimes it is held for the interim
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** period (while the IO is performed), and sometimes it is
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** relinquished. It is relinquished if (a) the IO op is an
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** ASYNC_CLOSE or (b) when the file handle was opened, two of
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** the underlying systems handles were opened on the same
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** file-system entry.
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**
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** If condition (b) above is true, then one file-handle
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** (AsyncFile.pBaseRead) is used exclusively by sqlite threads to read the
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** file, the other (AsyncFile.pBaseWrite) by sqlite3_async_flush()
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** threads to perform write() operations. This means that read
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** operations are not blocked by asynchronous writes (although
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** asynchronous writes may still be blocked by reads).
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**
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** This assumes that the OS keeps two handles open on the same file
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** properly in sync. That is, any read operation that starts after a
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** write operation on the same file system entry has completed returns
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** data consistent with the write. We also assume that if one thread
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** reads a file while another is writing it all bytes other than the
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** ones actually being written contain valid data.
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**
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** If the above assumptions are not true, set the preprocessor symbol
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** SQLITE_ASYNC_TWO_FILEHANDLES to 0.
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*/
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#ifndef NDEBUG
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# define TESTONLY( X ) X
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#else
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# define TESTONLY( X )
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#endif
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/*
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** PORTING FUNCTIONS
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**
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** There are two definitions of the following functions. One for pthreads
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** compatible systems and one for Win32. These functions isolate the OS
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** specific code required by each platform.
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**
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** The system uses three mutexes and a single condition variable. To
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** block on a mutex, async_mutex_enter() is called. The parameter passed
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** to async_mutex_enter(), which must be one of ASYNC_MUTEX_LOCK,
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** ASYNC_MUTEX_QUEUE or ASYNC_MUTEX_WRITER, identifies which of the three
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** mutexes to lock. Similarly, to unlock a mutex, async_mutex_leave() is
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** called with a parameter identifying the mutex being unlocked. Mutexes
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** are not recursive - it is an error to call async_mutex_enter() to
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** lock a mutex that is already locked, or to call async_mutex_leave()
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** to unlock a mutex that is not currently locked.
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**
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** The async_cond_wait() and async_cond_signal() functions are modelled
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** on the pthreads functions with similar names. The first parameter to
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** both functions is always ASYNC_COND_QUEUE. When async_cond_wait()
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** is called the mutex identified by the second parameter must be held.
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** The mutex is unlocked, and the calling thread simultaneously begins
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** waiting for the condition variable to be signalled by another thread.
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** After another thread signals the condition variable, the calling
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** thread stops waiting, locks mutex eMutex and returns. The
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** async_cond_signal() function is used to signal the condition variable.
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** It is assumed that the mutex used by the thread calling async_cond_wait()
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** is held by the caller of async_cond_signal() (otherwise there would be
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** a race condition).
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**
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** It is guaranteed that no other thread will call async_cond_wait() when
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** there is already a thread waiting on the condition variable.
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**
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** The async_sched_yield() function is called to suggest to the operating
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** system that it would be a good time to shift the current thread off the
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** CPU. The system will still work if this function is not implemented
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** (it is not currently implemented for win32), but it might be marginally
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** more efficient if it is.
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*/
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static void async_mutex_enter(int eMutex);
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static void async_mutex_leave(int eMutex);
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static void async_cond_wait(int eCond, int eMutex);
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static void async_cond_signal(int eCond);
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static void async_sched_yield(void);
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/*
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** There are also two definitions of the following. async_os_initialize()
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** is called when the asynchronous VFS is first installed, and os_shutdown()
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** is called when it is uninstalled (from within sqlite3async_shutdown()).
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**
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** For pthreads builds, both of these functions are no-ops. For win32,
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** they provide an opportunity to initialize and finalize the required
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** mutex and condition variables.
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**
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** If async_os_initialize() returns other than zero, then the initialization
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** fails and SQLITE_ERROR is returned to the user.
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*/
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static int async_os_initialize(void);
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static void async_os_shutdown(void);
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/* Values for use as the 'eMutex' argument of the above functions. The
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** integer values assigned to these constants are important for assert()
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** statements that verify that mutexes are locked in the correct order.
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** Specifically, it is unsafe to try to lock mutex N while holding a lock
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** on mutex M if (M<=N).
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*/
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#define ASYNC_MUTEX_LOCK 0
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#define ASYNC_MUTEX_QUEUE 1
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#define ASYNC_MUTEX_WRITER 2
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/* Values for use as the 'eCond' argument of the above functions. */
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#define ASYNC_COND_QUEUE 0
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/*************************************************************************
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** Start of OS specific code.
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*/
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#if SQLITE_OS_WIN || defined(_WIN32) || defined(WIN32) || defined(__CYGWIN__) || defined(__MINGW32__) || defined(__BORLANDC__)
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#include <windows.h>
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/* The following block contains the win32 specific code. */
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#define mutex_held(X) (GetCurrentThreadId()==primitives.aHolder[X])
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static struct AsyncPrimitives {
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int isInit;
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DWORD aHolder[3];
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CRITICAL_SECTION aMutex[3];
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HANDLE aCond[1];
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} primitives = { 0 };
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static int async_os_initialize(void){
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if( !primitives.isInit ){
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primitives.aCond[0] = CreateEvent(NULL, TRUE, FALSE, 0);
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if( primitives.aCond[0]==NULL ){
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return 1;
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}
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InitializeCriticalSection(&primitives.aMutex[0]);
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InitializeCriticalSection(&primitives.aMutex[1]);
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InitializeCriticalSection(&primitives.aMutex[2]);
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primitives.isInit = 1;
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}
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return 0;
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}
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static void async_os_shutdown(void){
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if( primitives.isInit ){
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DeleteCriticalSection(&primitives.aMutex[0]);
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DeleteCriticalSection(&primitives.aMutex[1]);
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DeleteCriticalSection(&primitives.aMutex[2]);
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CloseHandle(primitives.aCond[0]);
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primitives.isInit = 0;
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}
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}
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/* The following block contains the Win32 specific code. */
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static void async_mutex_enter(int eMutex){
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assert( eMutex==0 || eMutex==1 || eMutex==2 );
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assert( eMutex!=2 || (!mutex_held(0) && !mutex_held(1) && !mutex_held(2)) );
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assert( eMutex!=1 || (!mutex_held(0) && !mutex_held(1)) );
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assert( eMutex!=0 || (!mutex_held(0)) );
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EnterCriticalSection(&primitives.aMutex[eMutex]);
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TESTONLY( primitives.aHolder[eMutex] = GetCurrentThreadId(); )
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}
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static void async_mutex_leave(int eMutex){
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assert( eMutex==0 || eMutex==1 || eMutex==2 );
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assert( mutex_held(eMutex) );
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TESTONLY( primitives.aHolder[eMutex] = 0; )
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LeaveCriticalSection(&primitives.aMutex[eMutex]);
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}
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static void async_cond_wait(int eCond, int eMutex){
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ResetEvent(primitives.aCond[eCond]);
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async_mutex_leave(eMutex);
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WaitForSingleObject(primitives.aCond[eCond], INFINITE);
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async_mutex_enter(eMutex);
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}
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static void async_cond_signal(int eCond){
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assert( mutex_held(ASYNC_MUTEX_QUEUE) );
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SetEvent(primitives.aCond[eCond]);
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}
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static void async_sched_yield(void){
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Sleep(0);
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}
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#else
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/* The following block contains the pthreads specific code. */
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#include <pthread.h>
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#include <sched.h>
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#define mutex_held(X) pthread_equal(primitives.aHolder[X], pthread_self())
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static int async_os_initialize(void) {return 0;}
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static void async_os_shutdown(void) {}
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static struct AsyncPrimitives {
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pthread_mutex_t aMutex[3];
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pthread_cond_t aCond[1];
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pthread_t aHolder[3];
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} primitives = {
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{ PTHREAD_MUTEX_INITIALIZER,
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PTHREAD_MUTEX_INITIALIZER,
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PTHREAD_MUTEX_INITIALIZER
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} , {
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PTHREAD_COND_INITIALIZER
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} , { 0, 0, 0 }
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};
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static void async_mutex_enter(int eMutex){
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assert( eMutex==0 || eMutex==1 || eMutex==2 );
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assert( eMutex!=2 || (!mutex_held(0) && !mutex_held(1) && !mutex_held(2)) );
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assert( eMutex!=1 || (!mutex_held(0) && !mutex_held(1)) );
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assert( eMutex!=0 || (!mutex_held(0)) );
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pthread_mutex_lock(&primitives.aMutex[eMutex]);
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TESTONLY( primitives.aHolder[eMutex] = pthread_self(); )
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}
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static void async_mutex_leave(int eMutex){
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assert( eMutex==0 || eMutex==1 || eMutex==2 );
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assert( mutex_held(eMutex) );
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TESTONLY( primitives.aHolder[eMutex] = 0; )
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pthread_mutex_unlock(&primitives.aMutex[eMutex]);
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}
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static void async_cond_wait(int eCond, int eMutex){
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assert( eMutex==0 || eMutex==1 || eMutex==2 );
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assert( mutex_held(eMutex) );
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TESTONLY( primitives.aHolder[eMutex] = 0; )
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pthread_cond_wait(&primitives.aCond[eCond], &primitives.aMutex[eMutex]);
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TESTONLY( primitives.aHolder[eMutex] = pthread_self(); )
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}
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static void async_cond_signal(int eCond){
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assert( mutex_held(ASYNC_MUTEX_QUEUE) );
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pthread_cond_signal(&primitives.aCond[eCond]);
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}
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static void async_sched_yield(void){
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sched_yield();
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}
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#endif
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/*
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** End of OS specific code.
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*************************************************************************/
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#define assert_mutex_is_held(X) assert( mutex_held(X) )
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#ifndef SQLITE_ASYNC_TWO_FILEHANDLES
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/* #define SQLITE_ASYNC_TWO_FILEHANDLES 0 */
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#define SQLITE_ASYNC_TWO_FILEHANDLES 1
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#endif
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/*
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** State information is held in the static variable "async" defined
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** as the following structure.
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**
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** Both async.ioError and async.nFile are protected by async.queueMutex.
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*/
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static struct TestAsyncStaticData {
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AsyncWrite *pQueueFirst; /* Next write operation to be processed */
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AsyncWrite *pQueueLast; /* Last write operation on the list */
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AsyncLock *pLock; /* Linked list of all AsyncLock structures */
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volatile int ioDelay; /* Extra delay between write operations */
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volatile int eHalt; /* One of the SQLITEASYNC_HALT_XXX values */
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volatile int bLockFiles; /* Current value of "lockfiles" parameter */
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int ioError; /* True if an IO error has occurred */
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int nFile; /* Number of open files (from sqlite pov) */
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} async = { 0,0,0,0,0,1,0,0 };
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/* Possible values of AsyncWrite.op */
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#define ASYNC_NOOP 0
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#define ASYNC_WRITE 1
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#define ASYNC_SYNC 2
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#define ASYNC_TRUNCATE 3
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#define ASYNC_CLOSE 4
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#define ASYNC_DELETE 5
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#define ASYNC_OPENEXCLUSIVE 6
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#define ASYNC_UNLOCK 7
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/* Names of opcodes. Used for debugging only.
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** Make sure these stay in sync with the macros above!
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*/
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static const char *azOpcodeName[] = {
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"NOOP", "WRITE", "SYNC", "TRUNCATE", "CLOSE", "DELETE", "OPENEX", "UNLOCK"
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};
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/*
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** Entries on the write-op queue are instances of the AsyncWrite
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** structure, defined here.
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**
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** The interpretation of the iOffset and nByte variables varies depending
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** on the value of AsyncWrite.op:
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**
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** ASYNC_NOOP:
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** No values used.
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**
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** ASYNC_WRITE:
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** iOffset -> Offset in file to write to.
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** nByte -> Number of bytes of data to write (pointed to by zBuf).
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**
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** ASYNC_SYNC:
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** nByte -> flags to pass to sqlite3OsSync().
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**
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** ASYNC_TRUNCATE:
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** iOffset -> Size to truncate file to.
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** nByte -> Unused.
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**
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** ASYNC_CLOSE:
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** iOffset -> Unused.
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** nByte -> Unused.
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**
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** ASYNC_DELETE:
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** iOffset -> Contains the "syncDir" flag.
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** nByte -> Number of bytes of zBuf points to (file name).
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**
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** ASYNC_OPENEXCLUSIVE:
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** iOffset -> Value of "delflag".
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** nByte -> Number of bytes of zBuf points to (file name).
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**
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** ASYNC_UNLOCK:
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** nByte -> Argument to sqlite3OsUnlock().
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**
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**
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** For an ASYNC_WRITE operation, zBuf points to the data to write to the file.
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** This space is sqlite3_malloc()d along with the AsyncWrite structure in a
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** single blob, so is deleted when sqlite3_free() is called on the parent
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** structure.
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*/
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struct AsyncWrite {
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AsyncFileData *pFileData; /* File to write data to or sync */
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int op; /* One of ASYNC_xxx etc. */
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sqlite_int64 iOffset; /* See above */
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int nByte; /* See above */
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char *zBuf; /* Data to write to file (or NULL if op!=ASYNC_WRITE) */
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AsyncWrite *pNext; /* Next write operation (to any file) */
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};
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/*
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** An instance of this structure is created for each distinct open file
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** (i.e. if two handles are opened on the one file, only one of these
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** structures is allocated) and stored in the async.aLock hash table. The
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** keys for async.aLock are the full pathnames of the opened files.
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**
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** AsyncLock.pList points to the head of a linked list of AsyncFileLock
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** structures, one for each handle currently open on the file.
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**
|
|
** 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, ...){
|
|
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) */
|
|
|