index-pack: loop while inflating objects in unpack_data

When the unpack_data function is given a consume() callback,
it unpacks only 64K of the input at a time, feeding it to
git_inflate along with a 64K output buffer.  However,
because we are inflating, there is a good chance that the
output buffer will fill before consuming all of the input.
In this case, we need to loop on git_inflate until we have
fed the whole input buffer, feeding each chunk of output to
the consume buffer.

The current code does not do this, and as a result, will
fail the loop condition and trigger a fatal "serious inflate
inconsistency" error in this case.

While we're rearranging the loop, let's get rid of the
extra last_out pointer. It is meant to point to the
beginning of the buffer that we feed to git_inflate, but in
practice this is always the beginning of our same 64K
buffer, because:

  1. At the beginning of the loop, we are feeding the
     buffer.

  2. At the end of the loop, if we are using a consume()
     function, we reset git_inflate's pointer to the
     beginning of the buffer.  If we are not using a
     consume() function, then we do not care about the value
     of last_out at all.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/index-pack.c

@@ -524,7 +524,6 @@ static void *unpack_data(struct object_entry *obj,
 	stream.avail_out = consume ? 64*1024 : obj->size;
 
 	do {
-		unsigned char *last_out = stream.next_out;
 		ssize_t n = (len < 64*1024) ? len : 64*1024;
 		n = pread(pack_fd, inbuf, n, from);
 		if (n < 0)
@@ -538,15 +537,19 @@ static void *unpack_data(struct object_entry *obj,
 		len -= n;
 		stream.next_in = inbuf;
 		stream.avail_in = n;
-		status = git_inflate(&stream, 0);
-		if (consume) {
-			if (consume(last_out, stream.next_out - last_out, cb_data)) {
-				free(inbuf);
-				free(data);
-				return NULL;
-			}
-			stream.next_out = data;
-			stream.avail_out = 64*1024;
+		if (!consume)
+			status = git_inflate(&stream, 0);
+		else {
+			do {
+				status = git_inflate(&stream, 0);
+				if (consume(data, stream.next_out - data, cb_data)) {
+					free(inbuf);
+					free(data);
+					return NULL;
+				}
+				stream.next_out = data;
+				stream.avail_out = 64*1024;
+			} while (status == Z_OK && stream.avail_in);
 		}
 	} while (len && status == Z_OK && !stream.avail_in);