From b5007211b6582fc38647ff695b5ac51541ea9de8 Mon Sep 17 00:00:00 2001 From: Karsten Blees Date: Thu, 27 Nov 2014 00:24:01 -0500 Subject: [PATCH] pack-bitmap: do not use gcc packed attribute The "__attribute__" flag may be a noop on some compilers. That's OK as long as the code is correct without the attribute, but in this case it is not. We would typically end up with a struct that is 2 bytes too long due to struct padding, breaking both reading and writing of bitmaps. Instead of marshalling the data in a struct, let's just provide helpers for reading and writing the appropriate types. Besides being correct on all platforms, the result is more efficient and simpler to read. Signed-off-by: Karsten Blees Signed-off-by: Jeff King Signed-off-by: Junio C Hamano --- csum-file.h | 11 +++++++++++ pack-bitmap-write.c | 8 +++----- pack-bitmap.c | 22 +++++++++++++++------- pack-bitmap.h | 6 ------ 4 files changed, 29 insertions(+), 18 deletions(-) diff --git a/csum-file.h b/csum-file.h index 9dedb038ea..da612c59c1 100644 --- a/csum-file.h +++ b/csum-file.h @@ -39,4 +39,15 @@ extern void sha1flush(struct sha1file *f); extern void crc32_begin(struct sha1file *); extern uint32_t crc32_end(struct sha1file *); +static inline void sha1write_u8(struct sha1file *f, uint8_t data) +{ + sha1write(f, &data, sizeof(data)); +} + +static inline void sha1write_be32(struct sha1file *f, uint32_t data) +{ + data = htonl(data); + sha1write(f, &data, sizeof(data)); +} + #endif diff --git a/pack-bitmap-write.c b/pack-bitmap-write.c index 1218befaf2..5d353ad6a7 100644 --- a/pack-bitmap-write.c +++ b/pack-bitmap-write.c @@ -473,7 +473,6 @@ static void write_selected_commits_v1(struct sha1file *f, for (i = 0; i < writer.selected_nr; ++i) { struct bitmapped_commit *stored = &writer.selected[i]; - struct bitmap_disk_entry on_disk; int commit_pos = sha1_pos(stored->commit->object.sha1, index, index_nr, sha1_access); @@ -481,11 +480,10 @@ static void write_selected_commits_v1(struct sha1file *f, if (commit_pos < 0) die("BUG: trying to write commit not in index"); - on_disk.object_pos = htonl(commit_pos); - on_disk.xor_offset = stored->xor_offset; - on_disk.flags = stored->flags; + sha1write_be32(f, commit_pos); + sha1write_u8(f, stored->xor_offset); + sha1write_u8(f, stored->flags); - sha1write(f, &on_disk, sizeof(on_disk)); dump_bitmap(f, stored->write_as); } } diff --git a/pack-bitmap.c b/pack-bitmap.c index 91e4101531..9f8b909811 100644 --- a/pack-bitmap.c +++ b/pack-bitmap.c @@ -197,13 +197,24 @@ static struct stored_bitmap *store_bitmap(struct bitmap_index *index, return stored; } +static inline uint32_t read_be32(const unsigned char *buffer, size_t *pos) +{ + uint32_t result = get_be32(buffer + *pos); + (*pos) += sizeof(result); + return result; +} + +static inline uint8_t read_u8(const unsigned char *buffer, size_t *pos) +{ + return buffer[(*pos)++]; +} + static int load_bitmap_entries_v1(struct bitmap_index *index) { static const size_t MAX_XOR_OFFSET = 160; uint32_t i; struct stored_bitmap **recent_bitmaps; - struct bitmap_disk_entry *entry; recent_bitmaps = xcalloc(MAX_XOR_OFFSET, sizeof(struct stored_bitmap)); @@ -214,15 +225,12 @@ static int load_bitmap_entries_v1(struct bitmap_index *index) uint32_t commit_idx_pos; const unsigned char *sha1; - entry = (struct bitmap_disk_entry *)(index->map + index->map_pos); - index->map_pos += sizeof(struct bitmap_disk_entry); + commit_idx_pos = read_be32(index->map, &index->map_pos); + xor_offset = read_u8(index->map, &index->map_pos); + flags = read_u8(index->map, &index->map_pos); - commit_idx_pos = ntohl(entry->object_pos); sha1 = nth_packed_object_sha1(index->pack, commit_idx_pos); - xor_offset = (int)entry->xor_offset; - flags = (int)entry->flags; - bitmap = read_bitmap_1(index); if (!bitmap) return -1; diff --git a/pack-bitmap.h b/pack-bitmap.h index 8b7f4e9f0d..487600b18c 100644 --- a/pack-bitmap.h +++ b/pack-bitmap.h @@ -5,12 +5,6 @@ #include "khash.h" #include "pack-objects.h" -struct bitmap_disk_entry { - uint32_t object_pos; - uint8_t xor_offset; - uint8_t flags; -} __attribute__((packed)); - struct bitmap_disk_header { char magic[4]; uint16_t version; -- 2.11.4.GIT