wut/libraries/wutdevoptab/devoptab_fs_seek.c

70 lines
1.5 KiB
C

#include "devoptab_fs.h"
off_t
__wut_fs_seek(struct _reent *r,
void *fd,
off_t pos,
int whence)
{
FSStatus status;
FSCmdBlock cmd;
FSStat fsStat;
uint64_t offset;
__wut_fs_file_t *file;
if (!fd) {
r->_errno = EINVAL;
return -1;
}
FSInitCmdBlock(&cmd);
file = (__wut_fs_file_t *)fd;
status = FSGetStatFile(__wut_devoptab_fs_client, &cmd, file->fd, &fsStat,
FS_ERROR_FLAG_ALL);
if (status < 0) {
r->_errno = __wut_fs_translate_error(status);
return -1;
}
// Find the offset to see from
switch(whence) {
// Set absolute position; start offset is 0
case SEEK_SET:
offset = 0;
break;
// Set position relative to the current position
case SEEK_CUR:
offset = file->offset;
break;
// Set position relative to the end of the file
case SEEK_END:
offset = fsStat.size;
break;
// An invalid option was provided
default:
r->_errno = EINVAL;
return -1;
}
// TODO: A better check that prevents overflow.
if(pos < 0 && offset < -pos) {
// Don't allow seek to before the beginning of the file
r->_errno = EINVAL;
return -1;
}
// Update the current offset
file->offset = offset + pos;
status = FSSetPosFile(__wut_devoptab_fs_client, &cmd, file->fd, file->offset,
FS_ERROR_FLAG_ALL);
if (status < 0) {
r->_errno = __wut_fs_translate_error(status);
return -1;
}
return file->offset;
}