diff options
Diffstat (limited to 'libstore/rdwr.c')
| -rw-r--r-- | libstore/rdwr.c | 56 |
1 files changed, 55 insertions, 1 deletions
diff --git a/libstore/rdwr.c b/libstore/rdwr.c index b4139a4e..e14601e3 100644 --- a/libstore/rdwr.c +++ b/libstore/rdwr.c @@ -20,11 +20,65 @@ with this program; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ +/* Write LEN bytes from BUF to STORE at ADDR. Returns the amount written in + AMOUNT. ADDR is in BLOCKS (as defined by store->block_size). */ error_t store_write (struct store *store, off_t addr, char *buf, size_t len, size_t *amount); { - + error_t err = 0; + size_t request_len = len; + off_t *runs = store->runs; + unsigned runs_len = store->runs_len; + store_write_meth_t write = store->meths->write; + int block_shift = store->log2_block_size; + + /* XXX: this isn't going to be very efficient if RUNS is very complex... + But it should do dandy if it's short. For long run lists, we could do a + binary search or something to find the starting run. */ + while (runs_len) + { + off_t run_offs = runs[0]; + off_t run_len = runs[1]; + + if (run_len <= addr) + /* Not to the right place yet, move on... */ + addr -= run_len; + else if (run_offs < 0) + /* A hole! Can't write here. Must stop. */ + break; + else + /* Ok, we can write in this run, at least a bit. */ + { + size_t written, blocks_written; + off_t end = addr + len; + off_t seg_len = end > run_len ? run_len - addr : len; + + /* Write to the actual object at the correct address. */ + err = (*write)(store, run_offs + addr, buf, seg_len, &written); + if (err) + /* Ack */ + break; + + buf += written; + len -= written; + + blocks_written = written >> block_shift; + if ((blocks_written << block_shift) != seg_amount) + /* A non-block multiple amount was written!? What do we do? */ + break; + + addr += blocks_written; + } + + runs += 2; + runs_len -= 2; + } + + if (!err) + *amount = request_len - len; + + return err; } error_t |