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[PATCH] Tweak count-delta interface

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Make it return copied source and insertion separately, so that
later implementation of heuristics can use them more flexibly.

This does not change the heuristics implemented in
diffcore-rename nor diffcore-break in any way.

Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Junio C Hamano
2005-06-03 01:36:03 -07:00
committed by Linus Torvalds
parent 5b86040679
commit 355e76a4a3
5 changed files with 40 additions and 25 deletions
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30
count-delta.c
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@ -29,15 +29,18 @@ static unsigned long get_hdr_size(const unsigned char **datap)
/*
* NOTE. We do not _interpret_ delta fully. As an approximation, we
* just count the number of bytes that are copied from the source, and
* the number of literal data bytes that are inserted. Number of
* bytes that are _not_ copied from the source is deletion, and number
* of inserted literal bytes are addition, so sum of them is what we
* return. xdelta can express an edit that copies data inside of the
* destination which originally came from the source. We do not count
* that in the following routine, so we are undercounting the source
* material that remains in the final output that way.
* the number of literal data bytes that are inserted.
*
* Number of bytes that are _not_ copied from the source is deletion,
* and number of inserted literal bytes are addition, so sum of them
* is the extent of damage. xdelta can express an edit that copies
* data inside of the destination which originally came from the
* source. We do not count that in the following routine, so we are
* undercounting the source material that remains in the final output
* that way.
*/
unsigned long count_delta(void *delta_buf, unsigned long delta_size)
int count_delta(void *delta_buf, unsigned long delta_size,
unsigned long *src_copied, unsigned long *literal_added)
{
unsigned long copied_from_source, added_literal;
const unsigned char *data, *top;
@ -46,7 +49,7 @@ unsigned long count_delta(void *delta_buf, unsigned long delta_size)
/* the smallest delta size possible is 6 bytes */
if (delta_size < 6)
return UINT_MAX;
return -1;
data = delta_buf;
top = delta_buf + delta_size;
@ -83,13 +86,12 @@ unsigned long count_delta(void *delta_buf, unsigned long delta_size)
/* sanity check */
if (data != top || out != dst_size)
return UINT_MAX;
return -1;
/* delete size is what was _not_ copied from source.
* edit size is that and literal additions.
*/
if (src_size + added_literal < copied_from_source)
/* we ended up overcounting and underflowed */
return 0;
return (src_size - copied_from_source) + added_literal;
*src_copied = copied_from_source;
*literal_added = added_literal;
return 0;
}