ssize_t bchlib_read(FAR void *handle, FAR char *buffer, size_t offset, size_t len)
{
FAR struct bchlib_s *bch = (FAR struct bchlib_s *)handle;
size_t nsectors;
size_t sector;
uint16_t sectoffset;
size_t nbytes;
size_t bytesread;
int ret;
/* Get rid of this special case right away */
if (len < 1)
{
return 0;
}
/* Convert the file position into a sector number an offset. */
sector = offset / bch->sectsize;
sectoffset = offset - sector * bch->sectsize;
if (sector >= bch->nsectors)
{
/* Return end-of-file */
return 0;
}
/* Read the initial partial sector */
bytesread = 0;
if (sectoffset > 0)
{
/* Read the sector into the sector buffer */
bchlib_readsector(bch, sector);
/* Copy the tail end of the sector to the user buffer */
if (sectoffset + len > bch->sectsize)
{
nbytes = bch->sectsize - sectoffset;
}
else
{
nbytes = len;
}
memcpy(buffer, &bch->buffer[sectoffset], nbytes);
/* Adjust pointers and counts */
sectoffset = 0;
sector++;
if (sector >= bch->nsectors)
{
return nbytes;
}
bytesread = nbytes;
buffer += nbytes;
len -= nbytes;
}
/* Then read all of the full sectors following the partial sector directly
* into the user buffer.
*/
if (len >= bch->sectsize )
{
nsectors = len / bch->sectsize;
if (sector + nsectors > bch->nsectors)
{
nsectors = bch->nsectors - sector;
}
ret = bch->inode->u.i_bops->read(bch->inode, (FAR uint8_t *)buffer,
sector, nsectors);
if (ret < 0)
{
fdbg("Read failed: %d\n");
return ret;
}
/* Adjust pointers and counts */
sectoffset = 0;
sector += nsectors;
nbytes = nsectors * bch->sectsize;
bytesread += nbytes;
if (sector >= bch->nsectors)
{
return bytesread;
}
buffer += nbytes;
len -= nbytes;
}
/* Then read any partial final sector */
if (len > 0)
{
/* Read the sector into the sector buffer */
bchlib_readsector(bch, sector);
/* Copy the head end of the sector to the user buffer */
memcpy(buffer, bch->buffer, len);
/* Adjust counts */
bytesread += len;
}
return bytesread;
}
ssize_t bchlib_write(FAR void *handle, FAR const char *buffer, size_t offset, size_t len)
{
FAR struct bchlib_s *bch = (FAR struct bchlib_s *)handle;
size_t nsectors;
size_t sector;
uint16_t sectoffset;
size_t nbytes;
size_t byteswritten;
int ret;
/* Get rid of this special case right away */
if (len < 1)
{
return 0;
}
/* Convert the file position into a sector number and offset. */
sector = offset / bch->sectsize;
sectoffset = offset - sector * bch->sectsize;
if (sector >= bch->nsectors)
{
return -EFBIG;
}
/* Write the initial partial sector */
byteswritten = 0;
if (sectoffset > 0)
{
/* Read the full sector into the sector buffer */
bchlib_readsector(bch, sector);
/* Copy the tail end of the sector from the user buffer */
if (sectoffset + len > bch->sectsize)
{
nbytes = bch->sectsize - sectoffset;
}
else
{
nbytes = len;
}
memcpy(&bch->buffer[sectoffset], buffer, nbytes);
bch->dirty = true;
/* Adjust pointers and counts */
sector++;
if (sector >= bch->nsectors)
{
return nbytes;
}
byteswritten = nbytes;
buffer += nbytes;
len -= nbytes;
}
/* Then write all of the full sectors following the partial sector
* directly from the user buffer.
*/
if (len >= bch->sectsize )
{
nsectors = len / bch->sectsize;
if (sector + nsectors > bch->nsectors)
{
nsectors = bch->nsectors - sector;
}
/* Write the contiguous sectors */
ret = bch->inode->u.i_bops->write(bch->inode, (FAR uint8_t *)buffer,
sector, nsectors);
if (ret < 0)
{
fdbg("Write failed: %d\n", ret);
return ret;
}
/* Adjust pointers and counts */
sector += nsectors;
nbytes = nsectors * bch->sectsize;
byteswritten += nbytes;
if (sector >= bch->nsectors)
{
return byteswritten;
}
buffer += nbytes;
len -= nbytes;
}
/* Then write any partial final sector */
if (len > 0)
{
/* Read the sector into the sector buffer */
bchlib_readsector(bch, sector);
/* Copy the head end of the sector from the user buffer */
memcpy(bch->buffer, buffer, len);
bch->dirty = true;
/* Adjust counts */
byteswritten += len;
}
/* Finally, flush any cached writes to the device as well */
ret = bchlib_flushsector(bch);
if (ret < 0)
{
fdbg("Flush failed: %d\n", ret);
return ret;
}
return byteswritten;
}