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authorJunio C Hamano <gitster@pobox.com>2012-04-03 15:53:10 -0700
committerJunio C Hamano <gitster@pobox.com>2012-04-03 16:24:45 -0700
commitd60c49c2d7f683cd24a738533846cd3e34f2073e (patch)
tree21edaed27035f0878e78e5ed107b7c7f81dc3fa8 /read-cache.c
parentdb3b313c84522d89ac358187a7f6928dfcfb1e7d (diff)
downloadgit-d60c49c2d7f683cd24a738533846cd3e34f2073e.tar.gz
read-cache.c: allow unaligned mapping of the index file
Both the on-disk format v2 and v3 pads the "name" field to the multiple of eight to make sure that various quantities in network long/short type can be accessed with ntohl/ntohs without having to worry about alignment, but this forces us to waste disk I/O bandwidth. Introduce ntoh_s()/ntoh_l() macros that the callers can use as if they were the regular ntohs()/ntohl() on a field that may not be aligned correctly. Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'read-cache.c')
-rw-r--r--read-cache.c44
1 files changed, 32 insertions, 12 deletions
diff --git a/read-cache.c b/read-cache.c
index fa8aa7376b..d8865f5175 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1285,6 +1285,26 @@ int read_index(struct index_state *istate)
return read_index_from(istate, get_index_file());
}
+#ifndef NEEDS_ALIGNED_ACCESS
+#define ntoh_s(var) ntohs(var)
+#define ntoh_l(var) ntohl(var)
+#else
+static inline uint16_t ntoh_s_force_align(void *p)
+{
+ uint16_t x;
+ memcpy(&x, p, sizeof(x));
+ return ntohs(x);
+}
+static inline uint32_t ntoh_l_force_align(void *p)
+{
+ uint32_t x;
+ memcpy(&x, p, sizeof(x));
+ return ntohl(x);
+}
+#define ntoh_s(var) ntoh_s_force_align(&(var))
+#define ntoh_l(var) ntoh_l_force_align(&(var))
+#endif
+
static struct cache_entry *create_from_disk(struct ondisk_cache_entry *ondisk)
{
struct cache_entry *ce;
@@ -1293,14 +1313,14 @@ static struct cache_entry *create_from_disk(struct ondisk_cache_entry *ondisk)
unsigned int flags;
/* On-disk flags are just 16 bits */
- flags = ntohs(ondisk->flags);
+ flags = ntoh_s(ondisk->flags);
len = flags & CE_NAMEMASK;
if (flags & CE_EXTENDED) {
struct ondisk_cache_entry_extended *ondisk2;
int extended_flags;
ondisk2 = (struct ondisk_cache_entry_extended *)ondisk;
- extended_flags = ntohs(ondisk2->flags2) << 16;
+ extended_flags = ntoh_s(ondisk2->flags2) << 16;
/* We do not yet understand any bit out of CE_EXTENDED_FLAGS */
if (extended_flags & ~CE_EXTENDED_FLAGS)
die("Unknown index entry format %08x", extended_flags);
@@ -1315,16 +1335,16 @@ static struct cache_entry *create_from_disk(struct ondisk_cache_entry *ondisk)
ce = xmalloc(cache_entry_size(len));
- ce->ce_ctime.sec = ntohl(ondisk->ctime.sec);
- ce->ce_mtime.sec = ntohl(ondisk->mtime.sec);
- ce->ce_ctime.nsec = ntohl(ondisk->ctime.nsec);
- ce->ce_mtime.nsec = ntohl(ondisk->mtime.nsec);
- ce->ce_dev = ntohl(ondisk->dev);
- ce->ce_ino = ntohl(ondisk->ino);
- ce->ce_mode = ntohl(ondisk->mode);
- ce->ce_uid = ntohl(ondisk->uid);
- ce->ce_gid = ntohl(ondisk->gid);
- ce->ce_size = ntohl(ondisk->size);
+ ce->ce_ctime.sec = ntoh_l(ondisk->ctime.sec);
+ ce->ce_mtime.sec = ntoh_l(ondisk->mtime.sec);
+ ce->ce_ctime.nsec = ntoh_l(ondisk->ctime.nsec);
+ ce->ce_mtime.nsec = ntoh_l(ondisk->mtime.nsec);
+ ce->ce_dev = ntoh_l(ondisk->dev);
+ ce->ce_ino = ntoh_l(ondisk->ino);
+ ce->ce_mode = ntoh_l(ondisk->mode);
+ ce->ce_uid = ntoh_l(ondisk->uid);
+ ce->ce_gid = ntoh_l(ondisk->gid);
+ ce->ce_size = ntoh_l(ondisk->size);
ce->ce_flags = flags;
hashcpy(ce->sha1, ondisk->sha1);