[PATCH] denser delta header encoding
- From
Nicolas Pitre <nico@cam.org>
- Date
- Jun 29, 2005, 04:27 UTC
- Message-ID
- <Pine.LNX.4.63.0506290021050.1667@localhost.localdomain>
Since the delta data format is not tied to any actual git object anymore, now is the time to add a small improvement to the delta data header as it is been done for packed object header. This patch allows for reducing the delta header of about 2 bytes and makes for simpler code.
Signed-off-by: Nicolas Pitre <nico@cam.org>
diff --git a/count-delta.c b/count-delta.c --- a/count-delta.c +++ b/count-delta.c @@ -11,16 +11,13 @@ static unsigned long get_hdr_size(const unsigned char **datap) { const unsigned char *data = *datap; - unsigned long size; - unsigned char cmd; - int i; - size = i = 0; - cmd = *data++; - while (cmd) { - if (cmd & 1) - size |= *data++ << i; - i += 8; - cmd >>= 1; + unsigned char cmd = *data++; + unsigned long size = cmd & ~0x80; + int i = 7; + while (cmd & 0x80) { + cmd = *data++; + size |= (cmd & ~0x80) << i; + i += 7; } *datap = data; return size; @@ -47,8 +44,8 @@ int count_delta(void *delta_buf, unsigne unsigned char cmd; unsigned long src_size, dst_size, out; - /* the smallest delta size possible is 6 bytes */ - if (delta_size < 6) + /* the smallest delta size possible is 4 bytes */ + if (delta_size < 4) return -1; data = delta_buf; diff --git a/diff-delta.c b/diff-delta.c --- a/diff-delta.c +++ b/diff-delta.c @@ -228,28 +228,22 @@ void *diff_delta(void *from_buf, unsigne top = to_buf + to_size; /* store reference buffer size */ - orig = out + outpos++; - *orig = i = 0; - do { - if (from_size & 0xff) { - *orig |= (1 << i); - out[outpos++] = from_size; - } - i++; - from_size >>= 8; - } while (from_size); + out[outpos++] = from_size; + from_size >>= 7; + while (from_size) { + out[outpos - 1] |= 0x80; + out[outpos++] = from_size; + from_size >>= 7; + } /* store target buffer size */ - orig = out + outpos++; - *orig = i = 0; - do { - if (to_size & 0xff) { - *orig |= (1 << i); - out[outpos++] = to_size; - } - i++; - to_size >>= 8; - } while (to_size); + out[outpos++] = to_size; + to_size >>= 7; + while (to_size) { + out[outpos - 1] |= 0x80; + out[outpos++] = to_size; + to_size >>= 7; + } inscnt = 0; moff = 0; diff --git a/patch-delta.c b/patch-delta.c --- a/patch-delta.c +++ b/patch-delta.c @@ -22,33 +22,33 @@ void *patch_delta(void *src_buf, unsigne unsigned long size; int i; - /* the smallest delta size possible is 6 bytes */ - if (delta_size < 6) + /* the smallest delta size possible is 4 bytes */ + if (delta_size < 4) return NULL; data = delta_buf; top = delta_buf + delta_size; /* make sure the orig file size matches what we expect */ - size = i = 0; cmd = *data++; - while (cmd) { - if (cmd & 1) - size |= *data++ << i; - i += 8; - cmd >>= 1; + size = cmd & ~0x80; + i = 7; + while (cmd & 0x80) { + cmd = *data++; + size |= (cmd & ~0x80) << i; + i += 7; } if (size != src_size) return NULL; /* now the result size */ - size = i = 0; cmd = *data++; - while (cmd) { - if (cmd & 1) - size |= *data++ << i; - i += 8; - cmd >>= 1; + size = cmd & ~0x80; + i = 7; + while (cmd & 0x80) { + cmd = *data++; + size |= (cmd & ~0x80) << i; + i += 7; } dst_buf = malloc(size); if (!dst_buf)