int fseek(FAR FILE *stream, long int offset, int whence)
{
#if CONFIG_STDIO_BUFFER_SIZE > 0
/* Flush any valid read/write data in the buffer (also verifies stream) */
if (lib_rdflush(stream) < 0 || lib_wrflush(stream) < 0)
{
return ERROR;
}
#else
/* Verify that we were provided with a stream */
if (!stream)
{
set_errno(EBADF);
return ERROR;
}
#endif
/* On success or failure, discard any characters saved by ungetc() */
#if CONFIG_NUNGET_CHARS > 0
stream->fs_nungotten = 0;
#endif
/* Perform the fseek on the underlying file descriptor */
return lseek(stream->fs_fd, offset, whence) == (off_t)-1 ? ERROR : OK;
}
ssize_t lib_fread(FAR void *ptr, size_t count, FAR FILE *stream)
{
unsigned char *dest = (unsigned char*)ptr;
ssize_t bytes_read;
#if CONFIG_STDIO_BUFFER_SIZE > 0
int ret;
#endif
/* Make sure that reading from this stream is allowed */
if (!stream || (stream->fs_oflags & O_RDOK) == 0)
{
set_errno(EBADF);
bytes_read = -1;
}
else
{
/* The stream must be stable until we complete the read */
lib_take_semaphore(stream);
#if CONFIG_NUNGET_CHARS > 0
/* First, re-read any previously ungotten characters */
while ((stream->fs_nungotten > 0) && (count > 0))
{
/* Decrement the count of ungotten bytes to get an index */
stream->fs_nungotten--;
/* Return the last ungotten byte */
*dest++ = stream->fs_ungotten[stream->fs_nungotten];
/* That's one less byte that we have to read */
count--;
}
#endif
#if CONFIG_STDIO_BUFFER_SIZE > 0
/* If the buffer is currently being used for write access, then
* flush all of the buffered write data. We do not support concurrent
* buffered read/write access.
*/
ret = lib_wrflush(stream);
if (ret < 0)
{
lib_give_semaphore(stream);
return ret;
}
/* Now get any other needed chars from the buffer or the file. */
while (count > 0)
{
/* Is there readable data in the buffer? */
while ((count > 0) && (stream->fs_bufpos < stream->fs_bufread))
{
/* Yes, copy a byte into the user buffer */
*dest++ = *stream->fs_bufpos++;
count--;
}
/* The buffer is empty OR we have already supplied the number of
* bytes requested in the read. Check if we need to read
* more from the file.
*/
if (count > 0)
{
size_t buffer_available;
/* We need to read more data into the buffer from the file */
/* Mark the buffer empty */
stream->fs_bufpos = stream->fs_bufread = stream->fs_bufstart;
/* How much space is available in the buffer? */
buffer_available = stream->fs_bufend - stream->fs_bufread;
/* Will the number of bytes that we need to read fit into
* the buffer space that is available? If the read size is
* larger than the buffer, then read some of the data
* directly into the user's buffer.
*/
if (count > buffer_available)
{
bytes_read = read(stream->fs_fd, dest, count);
if (bytes_read < 0)
{
/* An error occurred on the read. The error code is
* in the 'errno' variable.
*/
goto errout_with_errno;
}
else if (bytes_read == 0)
{
/* We are at the end of the file. But we may already
* have buffered data. In that case, we will report
* the EOF indication later.
*/
goto shortread;
}
else
{
/* Some bytes were read. Adjust the dest pointer */
dest += bytes_read;
/* Were all of the requested bytes read? */
if ((size_t)bytes_read < count)
{
/* No. We must be at the end of file. */
goto shortread;
}
else
{
/* Yes. We are done. */
count = 0;
}
}
}
else
{
/* The number of bytes required to satisfy the read
* is less than or equal to the size of the buffer
* space that we have left. Read as much as we can
* into the buffer.
*/
bytes_read = read(stream->fs_fd, stream->fs_bufread, buffer_available);
if (bytes_read < 0)
{
/* An error occurred on the read. The error code is
* in the 'errno' variable.
*/
goto errout_with_errno;
}
else if (bytes_read == 0)
{
/* We are at the end of the file. But we may already
* have buffered data. In that case, we will report
* the EOF indication later.
*/
goto shortread;
}
else
{
/* Some bytes were read */
stream->fs_bufread += bytes_read;
}
}
}
}
#else
/* Now get any other needed chars from the file. */
while (count > 0)
{
bytes_read = read(stream->fs_fd, dest, count);
if (bytes_read < 0)
{
/* An error occurred on the read. The error code is
* in the 'errno' variable.
*/
goto errout_with_errno;
}
else if (bytes_read == 0)
{
/* We are at the end of the file. But we may already
* have buffered data. In that case, we will report
* the EOF indication later.
*/
break;
}
else
{
dest += bytes_read;
count -= bytes_read;
}
}
#endif
/* Here after a successful (but perhaps short) read */
#if CONFIG_STDIO_BUFFER_SIZE > 0
shortread:
#endif
bytes_read = dest - (unsigned char*)ptr;
/* Set or clear the EOF indicator. If we get here because of a
* short read and the total number of* bytes read is zero, then
* we must be at the end-of-file.
*/
if (bytes_read > 0)
{
stream->fs_flags &= ~__FS_FLAG_EOF;
}
else
{
stream->fs_flags |= __FS_FLAG_EOF;
}
lib_give_semaphore(stream);
}
return bytes_read;
/* Error exits */
errout_with_errno:
stream->fs_flags |= __FS_FLAG_ERROR;
lib_give_semaphore(stream);
return -get_errno();
}
