Make git-unpack-objects a builtin

Signed-off-by: Matthias Kestenholz <matthias@spinlock.ch>
Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 310 insertions, 0 deletions

diff --git a/builtin-unpack-objects.c b/builtin-unpack-objects.c
new file mode 100644
index 0000000000..09d264d9f2
--- /dev/null
+++ b/builtin-unpack-objects.c
@@ -0,0 +1,310 @@
+#include "builtin.h"
+#include "cache.h"
+#include "object.h"
+#include "delta.h"
+#include "pack.h"
+#include "blob.h"
+#include "commit.h"
+#include "tag.h"
+#include "tree.h"
+
+#include <sys/time.h>
+
+static int dry_run, quiet;
+static const char unpack_usage[] = "git-unpack-objects [-n] [-q] < pack-file";
+
+/* We always read in 4kB chunks. */
+static unsigned char buffer[4096];
+static unsigned long offset, len, eof;
+static SHA_CTX ctx;
+
+/*
+ * Make sure at least "min" bytes are available in the buffer, and
+ * return the pointer to the buffer.
+ */
+static void * fill(int min)
+{
+	if (min <= len)
+		return buffer + offset;
+	if (eof)
+		die("unable to fill input");
+	if (min > sizeof(buffer))
+		die("cannot fill %d bytes", min);
+	if (offset) {
+		SHA1_Update(&ctx, buffer, offset);
+		memcpy(buffer, buffer + offset, len);
+		offset = 0;
+	}
+	do {
+		int ret = xread(0, buffer + len, sizeof(buffer) - len);
+		if (ret <= 0) {
+			if (!ret)
+				die("early EOF");
+			die("read error on input: %s", strerror(errno));
+		}
+		len += ret;
+	} while (len < min);
+	return buffer;
+}
+
+static void use(int bytes)
+{
+	if (bytes > len)
+		die("used more bytes than were available");
+	len -= bytes;
+	offset += bytes;
+}
+
+static void *get_data(unsigned long size)
+{
+	z_stream stream;
+	void *buf = xmalloc(size);
+
+	memset(&stream, 0, sizeof(stream));
+
+	stream.next_out = buf;
+	stream.avail_out = size;
+	stream.next_in = fill(1);
+	stream.avail_in = len;
+	inflateInit(&stream);
+
+	for (;;) {
+		int ret = inflate(&stream, 0);
+		use(len - stream.avail_in);
+		if (stream.total_out == size && ret == Z_STREAM_END)
+			break;
+		if (ret != Z_OK)
+			die("inflate returned %d\n", ret);
+		stream.next_in = fill(1);
+		stream.avail_in = len;
+	}
+	inflateEnd(&stream);
+	return buf;
+}
+
+struct delta_info {
+	unsigned char base_sha1[20];
+	unsigned long size;
+	void *delta;
+	struct delta_info *next;
+};
+
+static struct delta_info *delta_list;
+
+static void add_delta_to_list(unsigned char *base_sha1, void *delta, unsigned long size)
+{
+	struct delta_info *info = xmalloc(sizeof(*info));
+
+	memcpy(info->base_sha1, base_sha1, 20);
+	info->size = size;
+	info->delta = delta;
+	info->next = delta_list;
+	delta_list = info;
+}
+
+static void added_object(unsigned char *sha1, const char *type, void *data, unsigned long size);
+
+static void write_object(void *buf, unsigned long size, const char *type)
+{
+	unsigned char sha1[20];
+	if (write_sha1_file(buf, size, type, sha1) < 0)
+		die("failed to write object");
+	added_object(sha1, type, buf, size);
+}
+
+static int resolve_delta(const char *type,
+	void *base, unsigned long base_size,
+	void *delta, unsigned long delta_size)
+{
+	void *result;
+	unsigned long result_size;
+
+	result = patch_delta(base, base_size,
+			     delta, delta_size,
+			     &result_size);
+	if (!result)
+		die("failed to apply delta");
+	free(delta);
+	write_object(result, result_size, type);
+	free(result);
+	return 0;
+}
+
+static void added_object(unsigned char *sha1, const char *type, void *data, unsigned long size)
+{
+	struct delta_info **p = &delta_list;
+	struct delta_info *info;
+
+	while ((info = *p) != NULL) {
+		if (!memcmp(info->base_sha1, sha1, 20)) {
+			*p = info->next;
+			p = &delta_list;
+			resolve_delta(type, data, size, info->delta, info->size);
+			free(info);
+			continue;
+		}
+		p = &info->next;
+	}
+}
+
+static int unpack_non_delta_entry(enum object_type kind, unsigned long size)
+{
+	void *buf = get_data(size);
+	const char *type;
+
+	switch (kind) {
+	case OBJ_COMMIT: type = commit_type; break;
+	case OBJ_TREE:   type = tree_type; break;
+	case OBJ_BLOB:   type = blob_type; break;
+	case OBJ_TAG:    type = tag_type; break;
+	default: die("bad type %d", kind);
+	}
+	if (!dry_run)
+		write_object(buf, size, type);
+	free(buf);
+	return 0;
+}
+
+static int unpack_delta_entry(unsigned long delta_size)
+{
+	void *delta_data, *base;
+	unsigned long base_size;
+	char type[20];
+	unsigned char base_sha1[20];
+	int result;
+
+	memcpy(base_sha1, fill(20), 20);
+	use(20);
+
+	delta_data = get_data(delta_size);
+	if (dry_run) {
+		free(delta_data);
+		return 0;
+	}
+
+	if (!has_sha1_file(base_sha1)) {
+		add_delta_to_list(base_sha1, delta_data, delta_size);
+		return 0;
+	}
+	base = read_sha1_file(base_sha1, type, &base_size);
+	if (!base)
+		die("failed to read delta-pack base object %s", sha1_to_hex(base_sha1));
+	result = resolve_delta(type, base, base_size, delta_data, delta_size);
+	free(base);
+	return result;
+}
+
+static void unpack_one(unsigned nr, unsigned total)
+{
+	unsigned shift;
+	unsigned char *pack, c;
+	unsigned long size;
+	enum object_type type;
+
+	pack = fill(1);
+	c = *pack;
+	use(1);
+	type = (c >> 4) & 7;
+	size = (c & 15);
+	shift = 4;
+	while (c & 0x80) {
+		pack = fill(1);
+		c = *pack++;
+		use(1);
+		size += (c & 0x7f) << shift;
+		shift += 7;
+	}
+	if (!quiet) {
+		static unsigned long last_sec;
+		static unsigned last_percent;
+		struct timeval now;
+		unsigned percentage = (nr * 100) / total;
+
+		gettimeofday(&now, NULL);
+		if (percentage != last_percent || now.tv_sec != last_sec) {
+			last_sec = now.tv_sec;
+			last_percent = percentage;
+			fprintf(stderr, "%4u%% (%u/%u) done\r", percentage, nr, total);
+		}
+	}
+	switch (type) {
+	case OBJ_COMMIT:
+	case OBJ_TREE:
+	case OBJ_BLOB:
+	case OBJ_TAG:
+		unpack_non_delta_entry(type, size);
+		return;
+	case OBJ_DELTA:
+		unpack_delta_entry(size);
+		return;
+	default:
+		die("bad object type %d", type);
+	}
+}
+
+static void unpack_all(void)
+{
+	int i;
+	struct pack_header *hdr = fill(sizeof(struct pack_header));
+	unsigned nr_objects = ntohl(hdr->hdr_entries);
+
+	if (ntohl(hdr->hdr_signature) != PACK_SIGNATURE)
+		die("bad pack file");
+	if (!pack_version_ok(hdr->hdr_version))
+		die("unknown pack file version %d", ntohl(hdr->hdr_version));
+	fprintf(stderr, "Unpacking %d objects\n", nr_objects);
+
+	use(sizeof(struct pack_header));
+	for (i = 0; i < nr_objects; i++)
+		unpack_one(i+1, nr_objects);
+	if (delta_list)
+		die("unresolved deltas left after unpacking");
+}
+
+int cmd_unpack_objects(int argc, const char **argv, const char *prefix)
+{
+	int i;
+	unsigned char sha1[20];
+
+	quiet = !isatty(2);
+
+	for (i = 1 ; i < argc; i++) {
+		const char *arg = argv[i];
+
+		if (*arg == '-') {
+			if (!strcmp(arg, "-n")) {
+				dry_run = 1;
+				continue;
+			}
+			if (!strcmp(arg, "-q")) {
+				quiet = 1;
+				continue;
+			}
+			usage(unpack_usage);
+		}
+
+		/* We don't take any non-flag arguments now.. Maybe some day */
+		usage(unpack_usage);
+	}
+	SHA1_Init(&ctx);
+	unpack_all();
+	SHA1_Update(&ctx, buffer, offset);
+	SHA1_Final(sha1, &ctx);
+	if (memcmp(fill(20), sha1, 20))
+		die("final sha1 did not match");
+	use(20);
+
+	/* Write the last part of the buffer to stdout */
+	while (len) {
+		int ret = xwrite(1, buffer + offset, len);
+		if (ret <= 0)
+			break;
+		len -= ret;
+		offset += ret;
+	}
+
+	/* All done */
+	if (!quiet)
+		fprintf(stderr, "\n");
+	return 0;
+}