1 files changed, 67 insertions, 0 deletions
diff --git a/pack.h b/pack.h
new file mode 100644
index 0000000..f357c9f
--- /dev/null
+++ b/pack.h
@@ -0,0 +1,67 @@
+#ifndef PACK_H
+#define PACK_H
+
+#include "object.h"
+
+/*
+ * Packed object header
+ */
+#define PACK_SIGNATURE 0x5041434b	/* "PACK" */
+#define PACK_VERSION 2
+#define pack_version_ok(v) ((v) == htonl(2) || (v) == htonl(3))
+struct pack_header {
+	uint32_t hdr_signature;
+	uint32_t hdr_version;
+	uint32_t hdr_entries;
+};
+
+/*
+ * The first four bytes of index formats later than version 1 should
+ * start with this signature, as all older git binaries would find this
+ * value illegal and abort reading the file.
+ *
+ * This is the case because the number of objects in a packfile
+ * cannot exceed 1,431,660,000 as every object would need at least
+ * 3 bytes of data and the overall packfile cannot exceed 4 GiB with
+ * version 1 of the index file due to the offsets limited to 32 bits.
+ * Clearly the signature exceeds this maximum.
+ *
+ * Very old git binaries will also compare the first 4 bytes to the
+ * next 4 bytes in the index and abort with a "non-monotonic index"
+ * error if the second 4 byte word is smaller than the first 4
+ * byte word.  This would be true in the proposed future index
+ * format as idx_signature would be greater than idx_version.
+ */
+#define PACK_IDX_SIGNATURE 0xff744f63	/* "\377tOc" */
+
+/* These may be overridden by command-line parameters */
+extern uint32_t pack_idx_default_version;
+extern uint32_t pack_idx_off32_limit;
+
+/*
+ * Packed object index header
+ */
+struct pack_idx_header {
+	uint32_t idx_signature;
+	uint32_t idx_version;
+};
+
+/*
+ * Common part of object structure used for write_idx_file
+ */
+struct pack_idx_entry {
+	unsigned char sha1[20];
+	uint32_t crc32;
+	off_t offset;
+};
+
+extern const char *write_idx_file(const char *index_name, struct pack_idx_entry **objects, int nr_objects, unsigned char *sha1);
+
+extern int verify_pack(struct packed_git *, int);
+extern void fixup_pack_header_footer(int, unsigned char *, const char *, uint32_t);
+
+#define PH_ERROR_EOF		(-1)
+#define PH_ERROR_PACK_SIGNATURE	(-2)
+#define PH_ERROR_PROTOCOL	(-3)
+extern int read_pack_header(int fd, struct pack_header *);
+#endif