[PATCH 05/11] pack-write.c: add pv4_encode_in_pack_object_header

@@ -1,6 +1,7 @@
 #include "cache.h"
 #include "pack.h"
 #include "csum-file.h"
+#include "varint.h"
 
 void reset_pack_idx_option(struct pack_idx_option *opts)
 {

@@ -340,6 +341,34 @@ int encode_in_pack_object_header(enum object_type type, uintmax_t size, unsigned
 	return n;
 }
 
+/*
+ * The per-object header is a pretty dense thing, which is
+ *  - first byte: low four bits are "size", then three bits of "type",
+ *    and the high bit is "size continues".
+ *  - each byte afterwards: low seven bits are size continuation,
+ *    with the high bit being "size continues"
+ */
+int pv4_encode_in_pack_object_header(enum object_type type,
+				     uintmax_t size, unsigned char *hdr)
+{
+	uintmax_t val;
+	if (type < OBJ_COMMIT || type > OBJ_PV4_TREE || type == OBJ_OFS_DELTA)
+		die("bad type %d", type);
+
+	/*
+	 * We allocate 4 bits in the LSB for the object type which
+	 * should be good for quite a while, given that we effectively
+	 * encodes only 5 object types: commit, tree, blob, delta,
+	 * tag.
+	 */
+	val = size;
+	if (MSB(val, 4))
+		die("fixme: the code doesn't currently cope with big sizes");
+	val <<= 4;
+	val |= type;
+	return encode_varint(val, hdr);
+}
+
 struct sha1file *create_tmp_packfile(char **pack_tmp_name)
 {
 	char tmpname[PATH_MAX];

@@ -83,6 +83,7 @@ extern off_t write_pack_header(struct sha1file *f, int, uint32_t);
 extern void fixup_pack_header_footer(int, unsigned char *, const char *, uint32_t, unsigned char *, off_t);
 extern char *index_pack_lockfile(int fd);
 extern int encode_in_pack_object_header(enum object_type, uintmax_t, unsigned char *);
+extern int pv4_encode_in_pack_object_header(enum object_type, uintmax_t, unsigned char *);
 
 #define PH_ERROR_EOF		(-1)
 #define PH_ERROR_PACK_SIGNATURE	(-2)