1 files changed, 257 insertions, 0 deletions
diff --git a/pack-write.c b/pack-write.c
new file mode 100644
index 000000000..b426006c5
--- /dev/null
+++ b/pack-write.c
@@ -0,0 +1,257 @@
+#include "cache.h"
+#include "pack.h"
+#include "csum-file.h"
+
+uint32_t pack_idx_default_version = 2;
+uint32_t pack_idx_off32_limit = 0x7fffffff;
+
+static int sha1_compare(const void *_a, const void *_b)
+{
+	struct pack_idx_entry *a = *(struct pack_idx_entry **)_a;
+	struct pack_idx_entry *b = *(struct pack_idx_entry **)_b;
+	return hashcmp(a->sha1, b->sha1);
+}
+
+/*
+ * On entry *sha1 contains the pack content SHA1 hash, on exit it is
+ * the SHA1 hash of sorted object names. The objects array passed in
+ * will be sorted by SHA1 on exit.
+ */
+char *write_idx_file(char *index_name, struct pack_idx_entry **objects,
+		     int nr_objects, unsigned char *sha1)
+{
+	struct sha1file *f;
+	struct pack_idx_entry **sorted_by_sha, **list, **last;
+	off_t last_obj_offset = 0;
+	uint32_t array[256];
+	int i, fd;
+	git_SHA_CTX ctx;
+	uint32_t index_version;
+
+	if (nr_objects) {
+		sorted_by_sha = objects;
+		list = sorted_by_sha;
+		last = sorted_by_sha + nr_objects;
+		for (i = 0; i < nr_objects; ++i) {
+			if (objects[i]->offset > last_obj_offset)
+				last_obj_offset = objects[i]->offset;
+		}
+		qsort(sorted_by_sha, nr_objects, sizeof(sorted_by_sha[0]),
+		      sha1_compare);
+	}
+	else
+		sorted_by_sha = list = last = NULL;
+
+	if (!index_name) {
+		static char tmpfile[PATH_MAX];
+		snprintf(tmpfile, sizeof(tmpfile),
+			 "%s/pack/tmp_idx_XXXXXX", get_object_directory());
+		fd = xmkstemp(tmpfile);
+		index_name = xstrdup(tmpfile);
+	} else {
+		unlink(index_name);
+		fd = open(index_name, O_CREAT|O_EXCL|O_WRONLY, 0600);
+	}
+	if (fd < 0)
+		die("unable to create %s: %s", index_name, strerror(errno));
+	f = sha1fd(fd, index_name);
+
+	/* if last object's offset is >= 2^31 we should use index V2 */
+	index_version = (last_obj_offset >> 31) ? 2 : pack_idx_default_version;
+
+	/* index versions 2 and above need a header */
+	if (index_version >= 2) {
+		struct pack_idx_header hdr;
+		hdr.idx_signature = htonl(PACK_IDX_SIGNATURE);
+		hdr.idx_version = htonl(index_version);
+		sha1write(f, &hdr, sizeof(hdr));
+	}
+
+	/*
+	 * Write the first-level table (the list is sorted,
+	 * but we use a 256-entry lookup to be able to avoid
+	 * having to do eight extra binary search iterations).
+	 */
+	for (i = 0; i < 256; i++) {
+		struct pack_idx_entry **next = list;
+		while (next < last) {
+			struct pack_idx_entry *obj = *next;
+			if (obj->sha1[0] != i)
+				break;
+			next++;
+		}
+		array[i] = htonl(next - sorted_by_sha);
+		list = next;
+	}
+	sha1write(f, array, 256 * 4);
+
+	/* compute the SHA1 hash of sorted object names. */
+	git_SHA1_Init(&ctx);
+
+	/*
+	 * Write the actual SHA1 entries..
+	 */
+	list = sorted_by_sha;
+	for (i = 0; i < nr_objects; i++) {
+		struct pack_idx_entry *obj = *list++;
+		if (index_version < 2) {
+			uint32_t offset = htonl(obj->offset);
+			sha1write(f, &offset, 4);
+		}
+		sha1write(f, obj->sha1, 20);
+		git_SHA1_Update(&ctx, obj->sha1, 20);
+	}
+
+	if (index_version >= 2) {
+		unsigned int nr_large_offset = 0;
+
+		/* write the crc32 table */
+		list = sorted_by_sha;
+		for (i = 0; i < nr_objects; i++) {
+			struct pack_idx_entry *obj = *list++;
+			uint32_t crc32_val = htonl(obj->crc32);
+			sha1write(f, &crc32_val, 4);
+		}
+
+		/* write the 32-bit offset table */
+		list = sorted_by_sha;
+		for (i = 0; i < nr_objects; i++) {
+			struct pack_idx_entry *obj = *list++;
+			uint32_t offset = (obj->offset <= pack_idx_off32_limit) ?
+				obj->offset : (0x80000000 | nr_large_offset++);
+			offset = htonl(offset);
+			sha1write(f, &offset, 4);
+		}
+
+		/* write the large offset table */
+		list = sorted_by_sha;
+		while (nr_large_offset) {
+			struct pack_idx_entry *obj = *list++;
+			uint64_t offset = obj->offset;
+			if (offset > pack_idx_off32_limit) {
+				uint32_t split[2];
+				split[0] = htonl(offset >> 32);
+				split[1] = htonl(offset & 0xffffffff);
+				sha1write(f, split, 8);
+				nr_large_offset--;
+			}
+		}
+	}
+
+	sha1write(f, sha1, 20);
+	sha1close(f, NULL, CSUM_FSYNC);
+	git_SHA1_Final(sha1, &ctx);
+	return index_name;
+}
+
+/*
+ * Update pack header with object_count and compute new SHA1 for pack data
+ * associated to pack_fd, and write that SHA1 at the end.  That new SHA1
+ * is also returned in new_pack_sha1.
+ *
+ * If partial_pack_sha1 is non null, then the SHA1 of the existing pack
+ * (without the header update) is computed and validated against the
+ * one provided in partial_pack_sha1.  The validation is performed at
+ * partial_pack_offset bytes in the pack file.  The SHA1 of the remaining
+ * data (i.e. from partial_pack_offset to the end) is then computed and
+ * returned in partial_pack_sha1.
+ *
+ * Note that new_pack_sha1 is updated last, so both new_pack_sha1 and
+ * partial_pack_sha1 can refer to the same buffer if the caller is not
+ * interested in the resulting SHA1 of pack data above partial_pack_offset.
+ */
+void fixup_pack_header_footer(int pack_fd,
+			 unsigned char *new_pack_sha1,
+			 const char *pack_name,
+			 uint32_t object_count,
+			 unsigned char *partial_pack_sha1,
+			 off_t partial_pack_offset)
+{
+	int aligned_sz, buf_sz = 8 * 1024;
+	git_SHA_CTX old_sha1_ctx, new_sha1_ctx;
+	struct pack_header hdr;
+	char *buf;
+
+	git_SHA1_Init(&old_sha1_ctx);
+	git_SHA1_Init(&new_sha1_ctx);
+
+	if (lseek(pack_fd, 0, SEEK_SET) != 0)
+		die("Failed seeking to start of %s: %s", pack_name, strerror(errno));
+	if (read_in_full(pack_fd, &hdr, sizeof(hdr)) != sizeof(hdr))
+		die("Unable to reread header of %s: %s", pack_name, strerror(errno));
+	if (lseek(pack_fd, 0, SEEK_SET) != 0)
+		die("Failed seeking to start of %s: %s", pack_name, strerror(errno));
+	git_SHA1_Update(&old_sha1_ctx, &hdr, sizeof(hdr));
+	hdr.hdr_entries = htonl(object_count);
+	git_SHA1_Update(&new_sha1_ctx, &hdr, sizeof(hdr));
+	write_or_die(pack_fd, &hdr, sizeof(hdr));
+	partial_pack_offset -= sizeof(hdr);
+
+	buf = xmalloc(buf_sz);
+	aligned_sz = buf_sz - sizeof(hdr);
+	for (;;) {
+		ssize_t m, n;
+		m = (partial_pack_sha1 && partial_pack_offset < aligned_sz) ?
+			partial_pack_offset : aligned_sz;
+		n = xread(pack_fd, buf, m);
+		if (!n)
+			break;
+		if (n < 0)
+			die("Failed to checksum %s: %s", pack_name, strerror(errno));
+		git_SHA1_Update(&new_sha1_ctx, buf, n);
+
+		aligned_sz -= n;
+		if (!aligned_sz)
+			aligned_sz = buf_sz;
+
+		if (!partial_pack_sha1)
+			continue;
+
+		git_SHA1_Update(&old_sha1_ctx, buf, n);
+		partial_pack_offset -= n;
+		if (partial_pack_offset == 0) {
+			unsigned char sha1[20];
+			git_SHA1_Final(sha1, &old_sha1_ctx);
+			if (hashcmp(sha1, partial_pack_sha1) != 0)
+				die("Unexpected checksum for %s "
+				    "(disk corruption?)", pack_name);
+			/*
+			 * Now let's compute the SHA1 of the remainder of the
+			 * pack, which also means making partial_pack_offset
+			 * big enough not to matter anymore.
+			 */
+			git_SHA1_Init(&old_sha1_ctx);
+			partial_pack_offset = ~partial_pack_offset;
+			partial_pack_offset -= MSB(partial_pack_offset, 1);
+		}
+	}
+	free(buf);
+
+	if (partial_pack_sha1)
+		git_SHA1_Final(partial_pack_sha1, &old_sha1_ctx);
+	git_SHA1_Final(new_pack_sha1, &new_sha1_ctx);
+	write_or_die(pack_fd, new_pack_sha1, 20);
+	fsync_or_die(pack_fd, pack_name);
+}
+
+char *index_pack_lockfile(int ip_out)
+{
+	char packname[46];
+
+	/*
+	 * The first thing we expects from index-pack's output
+	 * is "pack\t%40s\n" or "keep\t%40s\n" (46 bytes) where
+	 * %40s is the newly created pack SHA1 name.  In the "keep"
+	 * case, we need it to remove the corresponding .keep file
+	 * later on.  If we don't get that then tough luck with it.
+	 */
+	if (read_in_full(ip_out, packname, 46) == 46 && packname[45] == '\n' &&
+	    memcmp(packname, "keep\t", 5) == 0) {
+		char path[PATH_MAX];
+		packname[45] = 0;
+		snprintf(path, sizeof(path), "%s/pack/pack-%s.keep",
+			 get_object_directory(), packname + 5);
+		return xstrdup(path);
+	}
+	return NULL;
+}