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Use the pread()/pwrite() interface on Posix if compiled with -DUSE_PREAD=1.

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Note that on Linux this is slower and does not work for large files. (CVS 3147)

FossilOrigin-Name: 5a24f61981df4d8b696f03372eba2d37228906d9
This commit is contained in:
drh
2006-03-23 22:42:20 +00:00
parent 4eeb1ffa97
commit b912b2889c
3 changed files with 49 additions and 10 deletions
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45
src/os_unix.c
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@@ -80,6 +80,7 @@ struct unixFile {
unsigned char isOpen; /* True if needs to be closed */
unsigned char fullSync; /* Use F_FULLSYNC if available */
int dirfd; /* File descriptor for the directory */
i64 offset; /* Seek offset */
#ifdef SQLITE_UNIX_THREADS
pthread_t tid; /* The thread that "owns" this OsFile */
#endif
@@ -904,6 +905,24 @@ int sqlite3UnixIsDirWritable(char *zBuf){
return 1;
}
/*
** Seek to the offset in id->offset then read cnt bytes into pBuf.
** Return the number of bytes actually read. Update the offset.
*/
static int seekAndRead(unixFile *id, void *pBuf, int cnt){
int got;
#ifdef USE_PREAD
got = pread(id->h, pBuf, cnt, id->offset);
#else
lseek(id->h, id->offset, SEEK_SET);
got = read(id->h, pBuf, cnt);
#endif
if( got>0 ){
id->offset += got;
}
return got;
}
/*
** Read data from a file into a buffer. Return SQLITE_OK if all
** bytes were read successfully and SQLITE_IOERR if anything goes
@@ -914,7 +933,7 @@ static int unixRead(OsFile *id, void *pBuf, int amt){
assert( id );
SimulateIOError(SQLITE_IOERR);
TIMER_START;
got = read(((unixFile*)id)->h, pBuf, amt);
got = seekAndRead((unixFile*)id, pBuf, amt);
TIMER_END;
TRACE5("READ %-3d %5d %7d %d\n", ((unixFile*)id)->h, got,
last_page, TIMER_ELAPSED);
@@ -927,6 +946,25 @@ static int unixRead(OsFile *id, void *pBuf, int amt){
}
}
/*
** Seek to the offset in id->offset then read cnt bytes into pBuf.
** Return the number of bytes actually read. Update the offset.
*/
static int seekAndWrite(unixFile *id, const void *pBuf, int cnt){
int got;
#ifdef USE_PREAD
got = pwrite(id->h, pBuf, cnt, id->offset);
#else
lseek(id->h, id->offset, SEEK_SET);
got = write(id->h, pBuf, cnt);
#endif
if( got>0 ){
id->offset += got;
}
return got;
}
/*
** Write data from a buffer into a file. Return SQLITE_OK on success
** or some other error code on failure.
@@ -938,7 +976,7 @@ static int unixWrite(OsFile *id, const void *pBuf, int amt){
SimulateIOError(SQLITE_IOERR);
SimulateDiskfullError;
TIMER_START;
while( amt>0 && (wrote = write(((unixFile*)id)->h, pBuf, amt))>0 ){
while( amt>0 && (wrote = seekAndWrite((unixFile*)id, pBuf, amt))>0 ){
amt -= wrote;
pBuf = &((char*)pBuf)[wrote];
}
@@ -961,7 +999,7 @@ static int unixSeek(OsFile *id, i64 offset){
#ifdef SQLITE_TEST
if( offset ) SimulateDiskfullError
#endif
lseek(((unixFile*)id)->h, offset, SEEK_SET);
((unixFile*)id)->offset = offset;
return SQLITE_OK;
}
@@ -1635,6 +1673,7 @@ static int allocateUnixFile(unixFile *pInit, OsFile **pId){
pInit->dirfd = -1;
pInit->fullSync = 0;
pInit->locktype = 0;
pInit->offset = 0;
SET_THREADID(pInit);
pNew = sqlite3ThreadSafeMalloc( sizeof(unixFile) );
if( pNew==0 ){