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Fix some lseek to zero problems

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git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@1251 42af7a65-404d-4744-a932-0658087f49c3
This commit is contained in:
patacongo 2008-11-16 14:54:03 +00:00
parent f2b7c5e6b4
commit 3a02c111ca
1 changed files with 113 additions and 112 deletions
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225
fs/fat/fs_fat32.c
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@ -304,7 +304,6 @@ static int fat_open(FAR struct file *filep, const char *relpath,
ff->ff_open = TRUE;
ff->ff_oflags = oflags;
ff->ff_sectorsincluster = 1;
/* Save information that can be used later to recover the directory entry */
@ -925,135 +924,137 @@ static off_t fat_seek(FAR struct file *filep, off_t offset, int whence)
position = ff->ff_size;
}
/* Set file position to the beginning of the file */
/* Set file position to the beginning of the file (first cluster,
* first sector in cluster)
*/
filep->f_pos = 0;
ff->ff_sectorsincluster = 1;
ff->ff_sectorsincluster = fs->fs_fatsecperclus;
/* Get the start cluster of the file */
cluster = ff->ff_startcluster;
/* Create a new cluster chain if the file does not have one (and
* if we are seeking beyond zero
*/
if (!cluster && position > 0)
{
cluster = fat_createchain(fs);
if (cluster < 0)
{
ret = cluster;
goto errout_with_semaphore;
}
ff->ff_startcluster = cluster;
}
/* Move file position if necessary */
if (position)
if (cluster)
{
/* Get the start cluster of the file */
/* If the file has a cluster chain, follow it to the
* requested position.
*/
cluster = ff->ff_startcluster;
if (!cluster)
clustersize = fs->fs_fatsecperclus * fs->fs_hwsectorsize;
for (;;)
{
/* Create a new cluster chain if the file does not have one */
/* Skip over clusters prior to the one containing
* the requested position.
*/
cluster = fat_createchain(fs);
if (cluster < 0)
ff->ff_currentcluster = cluster;
if (position < clustersize)
{
ret = cluster;
goto errout_with_semaphore;
break;
}
ff->ff_startcluster = cluster;
/* Extend the cluster chain if write in enabled. NOTE:
* this is not consistent with the lseek description:
* "The lseek() function allows the file offset to be
* set beyond the end of the file (but this does not
* change the size of the file). If data is later written
* at this point, subsequent reads of the data in the
* gap (a "hole") return null bytes ('\0') until data
* is actually written into the gap."
*/
if ((ff->ff_oflags & O_WROK) != 0)
{
/* Extend the cluster chain (fat_extendchain
* will follow the existing chain or add new
* clusters as needed.
*/
cluster = fat_extendchain(fs, cluster);
}
else
{
/* Otherwise we can only follong the existing chain */
cluster = fat_getcluster(fs, cluster);
}
if (cluster < 0)
{
/* An error occurred getting the cluster */
ret = cluster;
goto errout_with_semaphore;
}
/* Zero means that there is no further clusters available
* in the chain.
*/
if (cluster == 0)
{
/* At the position to the current locaiton and
* break out.
*/
position = clustersize;
break;
}
if (cluster >= fs->fs_nclusters)
{
ret = -ENOSPC;
goto errout_with_semaphore;
}
/* Otherwise, update the position and continue looking */
filep->f_pos += clustersize;
position -= clustersize;
}
if (cluster)
{
/* If the file has a cluster chain, follow it to the
* requested position.
*/
/* We get here after we have found the sector containing
* the requested position.
*
* Save the new file position
*/
clustersize = fs->fs_fatsecperclus * fs->fs_hwsectorsize;
for (;;)
{
/* Skip over clusters prior to the one containing
* the requested position.
*/
filep->f_pos += position;
ff->ff_currentcluster = cluster;
if (position < clustersize)
{
break;
}
/* Then get the current sector from the cluster and the offset
* into the cluster from the position
*/
/* Extend the cluster chain if write in enabled. NOTE:
* this is not consistent with the lseek description:
* "The lseek() function allows the file offset to be
* set beyond the end of the file (but this does not
* change the size of the file). If data is later written
* at this point, subsequent reads of the data in the
* gap (a "hole") return null bytes ('\0') until data
* is actually written into the gap."
*/
(void)fat_currentsector(fs, ff, filep->f_pos);
if ((ff->ff_oflags & O_WROK) != 0)
{
/* Extend the cluster chain (fat_extendchain
* will follow the existing chain or add new
* clusters as needed.
*/
/* Load the sector corresponding to the position */
cluster = fat_extendchain(fs, cluster);
}
else
{
/* Otherwise we can only follong the existing chain */
cluster = fat_getcluster(fs, cluster);
}
if (cluster < 0)
{
/* An error occurred getting the cluster */
ret = cluster;
goto errout_with_semaphore;
}
/* Zero means that there is no further clusters available
* in the chain.
*/
if (cluster == 0)
{
/* At the position to the current locaiton and
* break out.
*/
position = clustersize;
break;
}
if (cluster >= fs->fs_nclusters)
{
ret = -ENOSPC;
goto errout_with_semaphore;
}
/* Otherwise, update the position and continue looking */
filep->f_pos += clustersize;
position -= clustersize;
}
/* We get here after we have found the sector containing
* the requested position.
*
* Save the new file position
*/
filep->f_pos += position;
/* Then get the current sector from the cluster and the offset
* into the cluster from the position
*/
(void)fat_currentsector(fs, ff, filep->f_pos);
/* Load the sector corresponding to the position */
if ((position & SEC_NDXMASK(fs)) != 0)
{
ret = fat_ffcacheread(fs, ff, ff->ff_currentsector);
if (ret < 0)
{
goto errout_with_semaphore;
}
}
}
if ((position & SEC_NDXMASK(fs)) != 0)
{
ret = fat_ffcacheread(fs, ff, ff->ff_currentsector);
if (ret < 0)
{
goto errout_with_semaphore;
}
}
}
/* If we extended the size of the file, then mark the file as modified. */