streaming: read non-delta incrementally from a pack

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

diff --git a/streaming.c b/streaming.c
index 13cbce7aabd1ad8552b2948c9935a77d96fc6dcb..4fdd567a36a3f6b22a934838b46f6b2cd71fc3ec 100644 (file)
--- a/streaming.c
+++ b/streaming.c
@@ -51,6 +51,8 @@ static open_istream_fn open_istream_tbl[] = {
 struct git_istream {
        const struct stream_vtbl *vtbl;
        unsigned long size; /* inflated size of full object */
+       z_stream z;
+       enum { z_unused, z_used, z_done, z_error } z_state;
 
        union {
                struct {
@@ -64,8 +66,8 @@ struct git_istream {
                } loose;
 
                struct {
-                       int fd; /* open for reading */
-                       /* NEEDSWORK: what else? */
+                       struct packed_git *pack;
+                       off_t pos;
                } in_pack;
        } u;
 };
@@ -128,6 +130,20 @@ struct git_istream *open_istream(const unsigned char *sha1,
        return st;
 }
 
+
+/*****************************************************************
+ *
+ * Common helpers
+ *
+ *****************************************************************/
+
+static void close_deflated_stream(struct git_istream *st)
+{
+       if (st->z_state == z_used)
+               git_inflate_end(&st->z);
+}
+
+
 /*****************************************************************
  *
  * Loose object stream
@@ -146,9 +162,92 @@ static open_method_decl(loose)
  *
  *****************************************************************/
 
+static read_method_decl(pack_non_delta)
+{
+       size_t total_read = 0;
+
+       switch (st->z_state) {
+       case z_unused:
+               memset(&st->z, 0, sizeof(st->z));
+               git_inflate_init(&st->z);
+               st->z_state = z_used;
+               break;
+       case z_done:
+               return 0;
+       case z_error:
+               return -1;
+       case z_used:
+               break;
+       }
+
+       while (total_read < sz) {
+               int status;
+               struct pack_window *window = NULL;
+               unsigned char *mapped;
+
+               mapped = use_pack(st->u.in_pack.pack, &window,
+                                 st->u.in_pack.pos, &st->z.avail_in);
+
+               st->z.next_out = (unsigned char *)buf + total_read;
+               st->z.avail_out = sz - total_read;
+               st->z.next_in = mapped;
+               status = git_inflate(&st->z, Z_FINISH);
+
+               st->u.in_pack.pos += st->z.next_in - mapped;
+               total_read = st->z.next_out - (unsigned char *)buf;
+               unuse_pack(&window);
+
+               if (status == Z_STREAM_END) {
+                       git_inflate_end(&st->z);
+                       st->z_state = z_done;
+                       break;
+               }
+               if (status != Z_OK && status != Z_BUF_ERROR) {
+                       git_inflate_end(&st->z);
+                       st->z_state = z_error;
+                       return -1;
+               }
+       }
+       return total_read;
+}
+
+static close_method_decl(pack_non_delta)
+{
+       close_deflated_stream(st);
+       return 0;
+}
+
+static struct stream_vtbl pack_non_delta_vtbl = {
+       close_istream_pack_non_delta,
+       read_istream_pack_non_delta,
+};
+
 static open_method_decl(pack_non_delta)
 {
-       return -1; /* for now */
+       struct pack_window *window;
+       enum object_type in_pack_type;
+
+       st->u.in_pack.pack = oi->u.packed.pack;
+       st->u.in_pack.pos = oi->u.packed.offset;
+       window = NULL;
+
+       in_pack_type = unpack_object_header(st->u.in_pack.pack,
+                                           &window,
+                                           &st->u.in_pack.pos,
+                                           &st->size);
+       unuse_pack(&window);
+       switch (in_pack_type) {
+       default:
+               return -1; /* we do not do deltas for now */
+       case OBJ_COMMIT:
+       case OBJ_TREE:
+       case OBJ_BLOB:
+       case OBJ_TAG:
+               break;
+       }
+       st->z_state = z_unused;
+       st->vtbl = &pack_non_delta_vtbl;
+       return 0;
 }