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pack-bitmap: do not use gcc packed attribute

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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 <blees@dcon.de>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Karsten Blees 2014-11-27 00:24:01 -05:00 committed by Junio C Hamano
parent 68f4e1fc6a
commit b5007211b6
4 changed files with 29 additions and 18 deletions
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11
csum-file.h
View File

@ -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

8
pack-bitmap-write.c
View File

@ -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);
}
}

22
pack-bitmap.c
View File

@ -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;

6
pack-bitmap.h
View File

@ -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;