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; }