1 files changed, 148 insertions, 0 deletions
diff --git a/t/helper/test-pack-deltas.c b/t/helper/test-pack-deltas.c
new file mode 100644
index 0000000000..4caa024b1e
--- /dev/null
+++ b/t/helper/test-pack-deltas.c
@@ -0,0 +1,148 @@
+#define USE_THE_REPOSITORY_VARIABLE
+
+#include "test-tool.h"
+#include "git-compat-util.h"
+#include "delta.h"
+#include "git-zlib.h"
+#include "hash.h"
+#include "hex.h"
+#include "pack.h"
+#include "pack-objects.h"
+#include "parse-options.h"
+#include "setup.h"
+#include "strbuf.h"
+#include "string-list.h"
+
+static const char *usage_str[] = {
+	"test-tool pack-deltas --num-objects <num-objects>",
+	NULL
+};
+
+static unsigned long do_compress(void **pptr, unsigned long size)
+{
+	git_zstream stream;
+	void *in, *out;
+	unsigned long maxsize;
+
+	git_deflate_init(&stream, 1);
+	maxsize = git_deflate_bound(&stream, size);
+
+	in = *pptr;
+	out = xmalloc(maxsize);
+	*pptr = out;
+
+	stream.next_in = in;
+	stream.avail_in = size;
+	stream.next_out = out;
+	stream.avail_out = maxsize;
+	while (git_deflate(&stream, Z_FINISH) == Z_OK)
+		; /* nothing */
+	git_deflate_end(&stream);
+
+	free(in);
+	return stream.total_out;
+}
+
+static void write_ref_delta(struct hashfile *f,
+			    struct object_id *oid,
+			    struct object_id *base)
+{
+	unsigned char header[MAX_PACK_OBJECT_HEADER];
+	unsigned long size, base_size, delta_size, compressed_size, hdrlen;
+	enum object_type type;
+	void *base_buf, *delta_buf;
+	void *buf = repo_read_object_file(the_repository,
+					  oid, &type,
+					  &size);
+
+	if (!buf)
+		die("unable to read %s", oid_to_hex(oid));
+
+	base_buf = repo_read_object_file(the_repository,
+					 base, &type,
+					 &base_size);
+
+	if (!base_buf)
+		die("unable to read %s", oid_to_hex(base));
+
+	delta_buf = diff_delta(base_buf, base_size,
+			       buf, size, &delta_size, 0);
+
+	compressed_size = do_compress(&delta_buf, delta_size);
+
+	hdrlen = encode_in_pack_object_header(header, sizeof(header),
+					      OBJ_REF_DELTA, delta_size);
+	hashwrite(f, header, hdrlen);
+	hashwrite(f, base->hash, the_repository->hash_algo->rawsz);
+	hashwrite(f, delta_buf, compressed_size);
+
+	free(buf);
+	free(base_buf);
+	free(delta_buf);
+}
+
+int cmd__pack_deltas(int argc, const char **argv)
+{
+	int num_objects = -1;
+	struct hashfile *f;
+	struct strbuf line = STRBUF_INIT;
+	struct option options[] = {
+		OPT_INTEGER('n', "num-objects", &num_objects, N_("the number of objects to write")),
+		OPT_END()
+	};
+
+	argc = parse_options(argc, argv, NULL,
+			     options, usage_str, 0);
+
+	if (argc || num_objects < 0)
+		usage_with_options(usage_str, options);
+
+	setup_git_directory();
+
+	f = hashfd(the_repository->hash_algo, 1, "<stdout>");
+	write_pack_header(f, num_objects);
+
+	/* Read each line from stdin into 'line' */
+	while (strbuf_getline_lf(&line, stdin) != EOF) {
+		const char *type_str, *content_oid_str, *base_oid_str = NULL;
+		struct object_id content_oid, base_oid;
+		struct string_list items = STRING_LIST_INIT_NODUP;
+		/*
+		 * Tokenize into two or three parts:
+		 * 1. REF_DELTA, OFS_DELTA, or FULL.
+		 * 2. The object ID for the content object.
+		 * 3. The object ID for the base object (optional).
+		 */
+		if (string_list_split_in_place(&items, line.buf, " ", 3) < 0)
+			die("invalid input format: %s", line.buf);
+
+		if (items.nr < 2)
+			die("invalid input format: %s", line.buf);
+
+		type_str = items.items[0].string;
+		content_oid_str = items.items[1].string;
+
+		if (get_oid_hex(content_oid_str, &content_oid))
+			die("invalid object: %s", content_oid_str);
+		if (items.nr >= 3) {
+			base_oid_str = items.items[2].string;
+			if (get_oid_hex(base_oid_str, &base_oid))
+				die("invalid object: %s", base_oid_str);
+		}
+		string_list_clear(&items, 0);
+
+		if (!strcmp(type_str, "REF_DELTA"))
+			write_ref_delta(f, &content_oid, &base_oid);
+		else if (!strcmp(type_str, "OFS_DELTA"))
+			die("OFS_DELTA not implemented");
+		else if (!strcmp(type_str, "FULL"))
+			die("FULL not implemented");
+		else
+			die("unknown pack type: %s", type_str);
+	}
+
+	finalize_hashfile(f, NULL, FSYNC_COMPONENT_PACK,
+			  CSUM_HASH_IN_STREAM | CSUM_FSYNC | CSUM_CLOSE);
+	strbuf_release(&line);
+	return 0;
+}