Formerly rdwr.c.~2~

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