/* move the cursor of offset positions. */
void
seek_ifile(file_desc_t *fd, int offset)
{
unsigned int old_pos = fd->fds_pos;
unsigned int fbloc, vbloc;
/* update the position */
fd->fds_pos += offset;
/* does the seek imply a jump in another bloc? */
if (bloc_of_pos(fd->fds_pos) != bloc_of_pos(old_pos)) {
/* flush */
flush_ifile(fd);
/* the bloc index of the new buffer */
fbloc = bloc_of_pos(fd->fds_pos);
vbloc = vbloc_of_fbloc(fd->fds_inumber, fbloc, FALSE);
if (! vbloc)
/* the bloc #0 is full of zeros */
memset(fd->fds_buf, 0, BLOC_SIZE);
else
/* load the bloc */
read_bloc(current_volume, vbloc, fd->fds_buf);
}
}
/* return the pos in the file ; RETURN_FAILURE in case of error */
int
writec_ifile(file_desc_t *fd, char c)
{
unsigned int ibloc;
/* write the char in the buffer */
fd->fds_buf[ibloc_of_pos(fd->fds_pos)] = c;
/* first write in the bloc ? ensure the data bloc allocation */
if (! fd->fds_dirty) {
ibloc = vbloc_of_fbloc(fd->fds_inumber, bloc_of_pos(fd->fds_pos), TRUE);
if (! ibloc) {
return RETURN_FAILURE;
}
fd->fds_dirty = TRUE;
}
/* is the buffer full? */
if (ibloc_of_pos(fd->fds_pos) == BLOC_SIZE-1) {
/* write the buffer */
ibloc = vbloc_of_fbloc(fd->fds_inumber, bloc_of_pos(fd->fds_pos), FALSE);
write_bloc(current_vol, ibloc, fd->fds_buf);
/* read the new buffer */
ibloc = vbloc_of_fbloc(fd->fds_inumber,
bloc_of_pos(fd->fds_pos+1), FALSE);
if (! ibloc)
memset(fd->fds_buf, 0, BLOC_SIZE);
else
read_bloc(current_vol, ibloc, fd->fds_buf);
fd->fds_dirty = FALSE;
}
/* update the file cursor and size */
if (fd->fds_size < fd->fds_pos)
fd->fds_size = fd->fds_pos;
fd->fds_pos++;
/* the position of the written char */
return fd->fds_pos - 1;
}
/* note that flush don't need to worry about the bloc allocation; a
previous write operation has already done it. */
void
flush_ifile(file_desc_t *fd)
{
unsigned int fbloc; /* bloc index in the file */
unsigned int vbloc; /* bloc index in the volume */
if (fd-> fds_dirty) {
/* compute the number of the bloc on the volume associated to
the buffer */
fbloc = bloc_of_pos(fd->fds_pos);
vbloc = vbloc_of_fbloc(fd-> fds_inumber, fbloc, TRUE);
/* write back the buffer */
write_bloc(current_volume, vbloc, fd->fds_buf);
/* done */
fd-> fds_dirty = FALSE ;
}
}
