packfile: use get_be64() for large offsets

derrickstolee · gitster · commit ad622a256f0d · 2018-01-19T11:04:56.000-08:00
The pack-index version 2 format uses two 4-byte integers in
network-byte order to represent one 8-byte value. The current
implementation has several code clones for stitching these integers
together.

Use get_be64() to create an 8-byte integer from two 4-byte integers
represented this way.

Signed-off-by: Derrick Stolee &lt;dstolee@microsoft.com&gt;
Reviewed-by: Jeff King &lt;peff@peff.net&gt;
Signed-off-by: Junio C Hamano &lt;gitster@pobox.com&gt;
diff --git a/pack-revindex.c b/pack-revindex.c
@@ -134,10 +134,8 @@ static void create_pack_revindex(struct packed_git *p)
 			if (!(off & 0x80000000)) {
 				p->revindex[i].offset = off;
 			} else {
-				p->revindex[i].offset =
-					((uint64_t)ntohl(*off_64++)) << 32;
-				p->revindex[i].offset |=
-					ntohl(*off_64++);
+				p->revindex[i].offset = get_be64(off_64);
+				off_64 += 2;
 			}
 			p->revindex[i].nr = i;
 		}
diff --git a/packfile.c b/packfile.c
@@ -1702,8 +1702,7 @@ off_t nth_packed_object_offset(const struct packed_git *p, uint32_t n)
 			return off;
 		index += p->num_objects * 4 + (off & 0x7fffffff) * 8;
 		check_pack_index_ptr(p, index);
-		return (((uint64_t)ntohl(*((uint32_t *)(index + 0)))) << 32) |
-				   ntohl(*((uint32_t *)(index + 4)));
+		return get_be64(index);
 	}
 }
 

Original file line number	Diff line number	Diff line change
`@@ -134,10 +134,8 @@ static void create_pack_revindex(struct packed_git *p)`
`134`	`134`	`if (!(off & 0x80000000)) {`
`135`	`135`	`p->revindex[i].offset = off;`
`136`	`136`	`} else {`
`137`		`- p->revindex[i].offset =`
`138`		`- ((uint64_t)ntohl(*off_64++)) << 32;`
`139`		`- p->revindex[i].offset \|=`
`140`		`- ntohl(*off_64++);`
	`137`	`+ p->revindex[i].offset = get_be64(off_64);`
	`138`	`+ off_64 += 2;`
`141`	`139`	`}`
`142`	`140`	`p->revindex[i].nr = i;`
`143`	`141`	`}`
Original file line number	Diff line number	Diff line change
`@@ -1702,8 +1702,7 @@ off_t nth_packed_object_offset(const struct packed_git *p, uint32_t n)`
`1702`	`1702`	`return off;`
`1703`	`1703`	`index += p->num_objects * 4 + (off & 0x7fffffff) * 8;`
`1704`	`1704`	`check_pack_index_ptr(p, index);`
`1705`		`- return (((uint64_t)ntohl(((uint32_t )(index + 0)))) << 32) \|`
`1706`		`- ntohl(((uint32_t )(index + 4)));`
	`1705`	`+ return get_be64(index);`
`1707`	`1706`	`}`
`1708`	`1707`	`}`
`1709`	`1708`