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authorbrian m. carlson <sandals@crustytoothpaste.net>2019-02-19 00:05:24 (GMT)
committerJunio C Hamano <gitster@pobox.com>2019-04-01 02:57:39 (GMT)
commit575fa8a3ed5828f01a934fc3337f05a43ccf7679 (patch)
tree446cbb171d4c30338b57d7f746b76cb868fb1efa /read-cache.c
parent3899b88b49c03ae76f8834a277cbd45bc6bde830 (diff)
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read-cache: read data in a hash-independent way
Index entries are structured with a variety of fields up front, followed by a hash and one or two flags fields. Because the hash field is stored in the middle of the structure, it's difficult to use one fixed-size structure that easily allows access to the hash and flags fields. Adjust the structure to hold the maximum amount of data that may be needed using a member called "data" and read and write this field independently in the various places that need to read and write the structure. Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'read-cache.c')
-rw-r--r--read-cache.c74
1 files changed, 29 insertions, 45 deletions
diff --git a/read-cache.c b/read-cache.c
index 4dc6de1..da0e411 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1640,39 +1640,24 @@ struct ondisk_cache_entry {
uint32_t uid;
uint32_t gid;
uint32_t size;
- unsigned char sha1[20];
- uint16_t flags;
- char name[FLEX_ARRAY]; /* more */
-};
-
-/*
- * This struct is used when CE_EXTENDED bit is 1
- * The struct must match ondisk_cache_entry exactly from
- * ctime till flags
- */
-struct ondisk_cache_entry_extended {
- struct cache_time ctime;
- struct cache_time mtime;
- uint32_t dev;
- uint32_t ino;
- uint32_t mode;
- uint32_t uid;
- uint32_t gid;
- uint32_t size;
- unsigned char sha1[20];
- uint16_t flags;
- uint16_t flags2;
- char name[FLEX_ARRAY]; /* more */
+ /*
+ * unsigned char hash[hashsz];
+ * uint16_t flags;
+ * if (flags & CE_EXTENDED)
+ * uint16_t flags2;
+ */
+ unsigned char data[GIT_MAX_RAWSZ + 2 * sizeof(uint16_t)];
+ char name[FLEX_ARRAY];
};
/* These are only used for v3 or lower */
#define align_padding_size(size, len) ((size + (len) + 8) & ~7) - (size + len)
-#define align_flex_name(STRUCT,len) ((offsetof(struct STRUCT,name) + (len) + 8) & ~7)
+#define align_flex_name(STRUCT,len) ((offsetof(struct STRUCT,data) + (len) + 8) & ~7)
#define ondisk_cache_entry_size(len) align_flex_name(ondisk_cache_entry,len)
-#define ondisk_cache_entry_extended_size(len) align_flex_name(ondisk_cache_entry_extended,len)
-#define ondisk_ce_size(ce) (((ce)->ce_flags & CE_EXTENDED) ? \
- ondisk_cache_entry_extended_size(ce_namelen(ce)) : \
- ondisk_cache_entry_size(ce_namelen(ce)))
+#define ondisk_data_size(flags, len) (the_hash_algo->rawsz + \
+ ((flags & CE_EXTENDED) ? 2 : 1) * sizeof(uint16_t) + len)
+#define ondisk_data_size_max(len) (ondisk_data_size(CE_EXTENDED, len))
+#define ondisk_ce_size(ce) (ondisk_cache_entry_size(ondisk_data_size((ce)->ce_flags, ce_namelen(ce))))
/* Allow fsck to force verification of the index checksum. */
int verify_index_checksum;
@@ -1746,6 +1731,8 @@ static struct cache_entry *create_from_disk(struct mem_pool *ce_mem_pool,
struct cache_entry *ce;
size_t len;
const char *name;
+ const unsigned hashsz = the_hash_algo->rawsz;
+ const uint16_t *flagsp = (const uint16_t *)(ondisk->data + hashsz);
unsigned int flags;
size_t copy_len = 0;
/*
@@ -1758,22 +1745,20 @@ static struct cache_entry *create_from_disk(struct mem_pool *ce_mem_pool,
int expand_name_field = version == 4;
/* On-disk flags are just 16 bits */
- flags = get_be16(&ondisk->flags);
+ flags = get_be16(flagsp);
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 = get_be16(&ondisk2->flags2) << 16;
+ extended_flags = get_be16(flagsp + 1) << 16;
/* We do not yet understand any bit out of CE_EXTENDED_FLAGS */
if (extended_flags & ~CE_EXTENDED_FLAGS)
die(_("unknown index entry format 0x%08x"), extended_flags);
flags |= extended_flags;
- name = ondisk2->name;
+ name = (const char *)(flagsp + 2);
}
else
- name = ondisk->name;
+ name = (const char *)(flagsp + 1);
if (expand_name_field) {
const unsigned char *cp = (const unsigned char *)name;
@@ -1812,7 +1797,9 @@ static struct cache_entry *create_from_disk(struct mem_pool *ce_mem_pool,
ce->ce_flags = flags & ~CE_NAMEMASK;
ce->ce_namelen = len;
ce->index = 0;
- hashcpy(ce->oid.hash, ondisk->sha1);
+ hashcpy(ce->oid.hash, ondisk->data);
+ memcpy(ce->name, name, len);
+ ce->name[len] = '\0';
if (expand_name_field) {
if (copy_len)
@@ -2556,6 +2543,8 @@ static void copy_cache_entry_to_ondisk(struct ondisk_cache_entry *ondisk,
struct cache_entry *ce)
{
short flags;
+ const unsigned hashsz = the_hash_algo->rawsz;
+ uint16_t *flagsp = (uint16_t *)(ondisk->data + hashsz);
ondisk->ctime.sec = htonl(ce->ce_stat_data.sd_ctime.sec);
ondisk->mtime.sec = htonl(ce->ce_stat_data.sd_mtime.sec);
@@ -2567,15 +2556,13 @@ static void copy_cache_entry_to_ondisk(struct ondisk_cache_entry *ondisk,
ondisk->uid = htonl(ce->ce_stat_data.sd_uid);
ondisk->gid = htonl(ce->ce_stat_data.sd_gid);
ondisk->size = htonl(ce->ce_stat_data.sd_size);
- hashcpy(ondisk->sha1, ce->oid.hash);
+ hashcpy(ondisk->data, ce->oid.hash);
flags = ce->ce_flags & ~CE_NAMEMASK;
flags |= (ce_namelen(ce) >= CE_NAMEMASK ? CE_NAMEMASK : ce_namelen(ce));
- ondisk->flags = htons(flags);
+ flagsp[0] = htons(flags);
if (ce->ce_flags & CE_EXTENDED) {
- struct ondisk_cache_entry_extended *ondisk2;
- ondisk2 = (struct ondisk_cache_entry_extended *)ondisk;
- ondisk2->flags2 = htons((ce->ce_flags & CE_EXTENDED_FLAGS) >> 16);
+ flagsp[1] = htons((ce->ce_flags & CE_EXTENDED_FLAGS) >> 16);
}
}
@@ -2594,10 +2581,7 @@ static int ce_write_entry(git_hash_ctx *c, int fd, struct cache_entry *ce,
stripped_name = 1;
}
- if (ce->ce_flags & CE_EXTENDED)
- size = offsetof(struct ondisk_cache_entry_extended, name);
- else
- size = offsetof(struct ondisk_cache_entry, name);
+ size = offsetof(struct ondisk_cache_entry,data) + ondisk_data_size(ce->ce_flags, 0);
if (!previous_name) {
int len = ce_namelen(ce);
@@ -2755,7 +2739,7 @@ static int do_write_index(struct index_state *istate, struct tempfile *tempfile,
struct cache_entry **cache = istate->cache;
int entries = istate->cache_nr;
struct stat st;
- struct ondisk_cache_entry_extended ondisk;
+ struct ondisk_cache_entry ondisk;
struct strbuf previous_name_buf = STRBUF_INIT, *previous_name;
int drop_cache_tree = istate->drop_cache_tree;
off_t offset;