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A cluster is only allocated for a file when data is written, instead of when the file is opened

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file_extend_r renamed to _FAT_file_extend_r
This commit is contained in:
Michael Chisholm 2007-11-04 09:51:31 +00:00
parent 28e71f2920
commit 634887aa0f
1 changed files with 42 additions and 19 deletions
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61
source/fatfile.c
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@ -48,6 +48,10 @@
2007-04-12 - Chishm
* Fixed seek to end of file when reading
2007-11-04 - Chishm
* file_extend_r renamed to _FAT_file_extend_r
* A cluster is only allocated for a file when data is written, instead of when the file is opened
*/
@ -64,6 +68,20 @@
#include "bit_ops.h"
#include "filetime.h"
static void _FAT_file_resetPosition (FILE_STRUCT* file) {
PARTITION* partition = file->partition;
file->currentPosition = 0;
file->rwPosition.cluster = file->startCluster;
file->rwPosition.sector = 0;
file->rwPosition.byte = 0;
file->appendPosition.cluster = _FAT_fat_lastCluster (partition, file->startCluster);
file->appendPosition.sector = (file->filesize % partition->bytesPerCluster) / BYTES_PER_READ;
file->appendPosition.byte = file->filesize % BYTES_PER_READ;
}
int _FAT_open_r (struct _reent *r, void *fileStruct, const char *path, int flags, int mode) {
PARTITION* partition = NULL;
bool fileExists;
@ -204,25 +222,12 @@ int _FAT_open_r (struct _reent *r, void *fileStruct, const char *path, int flags
file->filesize = 0;
}
// Get a new cluster for the file if required
if (file->startCluster == 0) {
file->startCluster = _FAT_fat_linkFreeCluster (partition, CLUSTER_FREE);
}
// Remember the position of this file's directory entry
file->dirEntryStart = dirEntry.dataStart; // Points to the start of the LFN entries of a file, or the alias for no LFN
file->dirEntryEnd = dirEntry.dataEnd;
file->currentPosition = 0;
file->rwPosition.cluster = file->startCluster;
file->rwPosition.sector = 0;
file->rwPosition.byte = 0;
file->appendPosition.cluster = _FAT_fat_lastCluster (partition, file->startCluster);
file->appendPosition.sector = (file->filesize % partition->bytesPerCluster) / BYTES_PER_READ;
file->appendPosition.byte = file->filesize % BYTES_PER_READ;
_FAT_file_resetPosition (file);
// Check if the end of the file is on the end of a cluster
if ( (file->filesize > 0) && ((file->filesize % partition->bytesPerCluster)==0) ){
// Set flag to allocate a new cluster
@ -310,7 +315,7 @@ int _FAT_read_r (struct _reent *r, int fd, char *ptr, int len) {
}
// Don't try to read if the read pointer is past the end of file
if (file->currentPosition >= file->filesize) {
if (file->currentPosition >= file->filesize || file->startCluster == CLUSTER_FREE) {
return 0;
}
@ -319,6 +324,11 @@ int _FAT_read_r (struct _reent *r, int fd, char *ptr, int len) {
r->_errno = EOVERFLOW;
len = file->filesize - file->currentPosition;
}
// Short circuit cases where len is 0 (or less)
if (len <= 0) {
return 0;
}
remain = len;
@ -446,7 +456,7 @@ int _FAT_read_r (struct _reent *r, int fd, char *ptr, int len) {
/*
Extend a file so that the size is the same as the rwPosition
*/
static bool file_extend_r (struct _reent *r, FILE_STRUCT* file) {
static bool _FAT_file_extend_r (struct _reent *r, FILE_STRUCT* file) {
PARTITION* partition = file->partition;
CACHE* cache = file->partition->cache;
@ -460,6 +470,8 @@ static bool file_extend_r (struct _reent *r, FILE_STRUCT* file) {
position.byte = file->filesize % BYTES_PER_READ;
position.sector = (file->filesize % partition->bytesPerCluster) / BYTES_PER_READ;
// It is assumed that there is always a startCluster
// This will be true when _FAT_file_extend_r is called from _FAT_write_r
position.cluster = _FAT_fat_lastCluster (partition, file->startCluster);
remain = file->currentPosition - file->filesize;
@ -563,17 +575,28 @@ int _FAT_write_r (struct _reent *r,int fd, const char *ptr, int len) {
return 0;
}
// Short circuit cases where len is 0 (or less)
if (len <= 0) {
return 0;
}
partition = file->partition;
cache = file->partition->cache;
remain = len;
// Get a new cluster for the file if required
if (file->startCluster == CLUSTER_FREE) {
file->startCluster = _FAT_fat_linkFreeCluster (partition, CLUSTER_FREE);
_FAT_file_resetPosition (file);
}
if (file->append) {
position = file->appendPosition;
flagAppending = true;
} else {
// If the write pointer is past the end of the file, extend the file to that size
if (file->currentPosition > file->filesize) {
if (!file_extend_r (r, file)) {
if (!_FAT_file_extend_r (r, file)) {
return 0;
}
}
@ -788,7 +811,7 @@ int _FAT_seek_r (struct _reent *r, int fd, int pos, int dir) {
// Only change the read/write position if it is within the bounds of the current filesize,
// or at the very edge of the file
if (file->filesize >= position) {
if (position <= file->filesize && file->startCluster != CLUSTER_FREE) {
// Calculate the sector and byte of the current position,
// and store them
file->rwPosition.sector = (position % partition->bytesPerCluster) / BYTES_PER_READ;