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-rw-r--r--Makefile4
-rw-r--r--count-delta.c72
-rw-r--r--count-delta.h10
-rw-r--r--diffcore-break.c45
-rw-r--r--diffcore-delta.c96
-rw-r--r--diffcore-rename.c20
-rw-r--r--diffcore.h4
-rw-r--r--pack-check.c20
-rw-r--r--pack-objects.c38
9 files changed, 136 insertions, 173 deletions
diff --git a/Makefile b/Makefile
index 1c555da..8e2a496 100644
--- a/Makefile
+++ b/Makefile
@@ -190,7 +190,7 @@ PYMODULES = \
LIB_FILE=libgit.a
LIB_H = \
- blob.h cache.h commit.h count-delta.h csum-file.h delta.h \
+ blob.h cache.h commit.h csum-file.h delta.h \
diff.h object.h pack.h pkt-line.h quote.h refs.h \
run-command.h strbuf.h tag.h tree.h git-compat-util.h revision.h
@@ -200,7 +200,7 @@ DIFF_OBJS = \
diffcore-delta.o
LIB_OBJS = \
- blob.o commit.o connect.o count-delta.o csum-file.o \
+ blob.o commit.o connect.o csum-file.o \
date.o diff-delta.o entry.o exec_cmd.o ident.o index.o \
object.o pack-check.o patch-delta.o path.o pkt-line.o \
quote.o read-cache.o refs.o run-command.o \
diff --git a/count-delta.c b/count-delta.c
deleted file mode 100644
index 058a2aa..0000000
--- a/count-delta.c
+++ /dev/null
@@ -1,72 +0,0 @@
-/*
- * Copyright (C) 2005 Junio C Hamano
- * The delta-parsing part is almost straight copy of patch-delta.c
- * which is (C) 2005 Nicolas Pitre <nico@cam.org>.
- */
-#include <stdlib.h>
-#include <string.h>
-#include <limits.h>
-#include "delta.h"
-#include "count-delta.h"
-
-/*
- * 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 the extent of damage.
- */
-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;
- unsigned char cmd;
- unsigned long src_size, dst_size, out;
-
- if (delta_size < DELTA_SIZE_MIN)
- return -1;
-
- data = delta_buf;
- top = delta_buf + delta_size;
-
- src_size = get_delta_hdr_size(&data);
- dst_size = get_delta_hdr_size(&data);
-
- added_literal = copied_from_source = out = 0;
- while (data < top) {
- cmd = *data++;
- if (cmd & 0x80) {
- unsigned long cp_off = 0, cp_size = 0;
- if (cmd & 0x01) cp_off = *data++;
- if (cmd & 0x02) cp_off |= (*data++ << 8);
- if (cmd & 0x04) cp_off |= (*data++ << 16);
- if (cmd & 0x08) cp_off |= (*data++ << 24);
- if (cmd & 0x10) cp_size = *data++;
- if (cmd & 0x20) cp_size |= (*data++ << 8);
- if (cmd & 0x40) cp_size |= (*data++ << 16);
- if (cp_size == 0) cp_size = 0x10000;
-
- copied_from_source += cp_size;
- out += cp_size;
- } else {
- /* write literal into dst */
- added_literal += cmd;
- out += cmd;
- data += cmd;
- }
- }
-
- /* sanity check */
- if (data != top || out != dst_size)
- return -1;
-
- /* delete size is what was _not_ copied from source.
- * edit size is that and literal additions.
- */
- *src_copied = copied_from_source;
- *literal_added = added_literal;
- return 0;
-}
diff --git a/count-delta.h b/count-delta.h
deleted file mode 100644
index 7359629..0000000
--- a/count-delta.h
+++ /dev/null
@@ -1,10 +0,0 @@
-/*
- * Copyright (C) 2005 Junio C Hamano
- */
-#ifndef COUNT_DELTA_H
-#define COUNT_DELTA_H
-
-int count_delta(void *, unsigned long,
- unsigned long *src_copied, unsigned long *literal_added);
-
-#endif
diff --git a/diffcore-break.c b/diffcore-break.c
index 0fc2b86..71ad58a 100644
--- a/diffcore-break.c
+++ b/diffcore-break.c
@@ -45,8 +45,8 @@ static int should_break(struct diff_filespec *src,
* The value we return is 1 if we want the pair to be broken,
* or 0 if we do not.
*/
- unsigned long delta_size, base_size, src_copied, literal_added;
- int to_break = 0;
+ unsigned long delta_size, base_size, src_copied, literal_added,
+ src_removed;
*merge_score_p = 0; /* assume no deletion --- "do not break"
* is the default.
@@ -72,33 +72,40 @@ static int should_break(struct diff_filespec *src,
&src_copied, &literal_added))
return 0;
+ /* sanity */
+ if (src->size < src_copied)
+ src_copied = src->size;
+ if (dst->size < literal_added + src_copied) {
+ if (src_copied < dst->size)
+ literal_added = dst->size - src_copied;
+ else
+ literal_added = 0;
+ }
+ src_removed = src->size - src_copied;
+
/* Compute merge-score, which is "how much is removed
* from the source material". The clean-up stage will
* merge the surviving pair together if the score is
* less than the minimum, after rename/copy runs.
*/
- if (src->size <= src_copied)
- ; /* all copied, nothing removed */
- else {
- delta_size = src->size - src_copied;
- *merge_score_p = delta_size * MAX_SCORE / src->size;
- }
-
+ *merge_score_p = src_removed * MAX_SCORE / src->size;
+
/* Extent of damage, which counts both inserts and
* deletes.
*/
- if (src->size + literal_added <= src_copied)
- delta_size = 0; /* avoid wrapping around */
- else
- delta_size = (src->size - src_copied) + literal_added;
-
- /* We break if the edit exceeds the minimum.
- * i.e. (break_score / MAX_SCORE < delta_size / base_size)
+ delta_size = src_removed + literal_added;
+ if (delta_size * MAX_SCORE / base_size < break_score)
+ return 0;
+
+ /* If you removed a lot without adding new material, that is
+ * not really a rewrite.
*/
- if (break_score * base_size < delta_size * MAX_SCORE)
- to_break = 1;
+ if ((src->size * break_score < src_removed * MAX_SCORE) &&
+ (literal_added * 20 < src_removed) &&
+ (literal_added * 20 < src_copied))
+ return 0;
- return to_break;
+ return 1;
}
void diffcore_break(int break_score)
diff --git a/diffcore-delta.c b/diffcore-delta.c
index 1e6a691..70bacff 100644
--- a/diffcore-delta.c
+++ b/diffcore-delta.c
@@ -1,32 +1,53 @@
#include "cache.h"
#include "diff.h"
#include "diffcore.h"
-#include "delta.h"
-#include "count-delta.h"
-
-static int diffcore_count_changes_1(void *src, unsigned long src_size,
- void *dst, unsigned long dst_size,
- unsigned long delta_limit,
- unsigned long *src_copied,
- unsigned long *literal_added)
+
+/*
+ * Idea here is very simple.
+ *
+ * We have total of (sz-N+1) N-byte overlapping sequences in buf whose
+ * size is sz. If the same N-byte sequence appears in both source and
+ * destination, we say the byte that starts that sequence is shared
+ * between them (i.e. copied from source to destination).
+ *
+ * For each possible N-byte sequence, if the source buffer has more
+ * instances of it than the destination buffer, that means the
+ * difference are the number of bytes not copied from source to
+ * destination. If the counts are the same, everything was copied
+ * from source to destination. If the destination has more,
+ * everything was copied, and destination added more.
+ *
+ * We are doing an approximation so we do not really have to waste
+ * memory by actually storing the sequence. We just hash them into
+ * somewhere around 2^16 hashbuckets and count the occurrences.
+ *
+ * The length of the sequence is arbitrarily set to 8 for now.
+ */
+
+#define HASHBASE 65537 /* next_prime(2^16) */
+
+static void hash_chars(unsigned char *buf, unsigned long sz, int *count)
{
- void *delta;
- unsigned long delta_size;
-
- delta = diff_delta(src, src_size,
- dst, dst_size,
- &delta_size, delta_limit);
- if (!delta)
- /* If delta_limit is exceeded, we have too much differences */
- return -1;
+ unsigned int accum1, accum2, i;
- /* Estimate the edit size by interpreting delta. */
- if (count_delta(delta, delta_size, src_copied, literal_added)) {
- free(delta);
- return -1;
+ /* an 8-byte shift register made of accum1 and accum2. New
+ * bytes come at LSB of accum2, and shifted up to accum1
+ */
+ for (i = accum1 = accum2 = 0; i < 7; i++, sz--) {
+ accum1 = (accum1 << 8) | (accum2 >> 24);
+ accum2 = (accum2 << 8) | *buf++;
+ }
+ while (sz) {
+ accum1 = (accum1 << 8) | (accum2 >> 24);
+ accum2 = (accum2 << 8) | *buf++;
+ /* We want something that hashes permuted byte
+ * sequences nicely; simpler hash like (accum1 ^
+ * accum2) does not perform as well.
+ */
+ i = (accum1 + accum2 * 0x61) % HASHBASE;
+ count[i]++;
+ sz--;
}
- free(delta);
- return 0;
}
int diffcore_count_changes(void *src, unsigned long src_size,
@@ -35,9 +56,28 @@ int diffcore_count_changes(void *src, unsigned long src_size,
unsigned long *src_copied,
unsigned long *literal_added)
{
- return diffcore_count_changes_1(src, src_size,
- dst, dst_size,
- delta_limit,
- src_copied,
- literal_added);
+ int *src_count, *dst_count, i;
+ unsigned long sc, la;
+
+ if (src_size < 8 || dst_size < 8)
+ return -1;
+
+ src_count = xcalloc(HASHBASE * 2, sizeof(int));
+ dst_count = src_count + HASHBASE;
+ hash_chars(src, src_size, src_count);
+ hash_chars(dst, dst_size, dst_count);
+
+ sc = la = 0;
+ for (i = 0; i < HASHBASE; i++) {
+ if (src_count[i] < dst_count[i]) {
+ la += dst_count[i] - src_count[i];
+ sc += src_count[i];
+ }
+ else /* i.e. if (dst_count[i] <= src_count[i]) */
+ sc += dst_count[i];
+ }
+ *src_copied = sc;
+ *literal_added = la;
+ free(src_count);
+ return 0;
}
diff --git a/diffcore-rename.c b/diffcore-rename.c
index 55cf1c3..625b589 100644
--- a/diffcore-rename.c
+++ b/diffcore-rename.c
@@ -170,19 +170,15 @@ static int estimate_similarity(struct diff_filespec *src,
&src_copied, &literal_added))
return 0;
- /* Extent of damage */
- if (src->size + literal_added < src_copied)
- delta_size = 0;
- else
- delta_size = (src->size - src_copied) + literal_added;
-
- /*
- * Now we will give some score to it. 100% edit gets 0 points
- * and 0% edit gets MAX_SCORE points.
+ /* How similar are they?
+ * what percentage of material in dst are from source?
*/
- score = MAX_SCORE - (MAX_SCORE * delta_size / base_size);
- if (score < 0) return 0;
- if (MAX_SCORE < score) return MAX_SCORE;
+ if (dst->size < src_copied)
+ score = MAX_SCORE;
+ else if (!dst->size)
+ score = 0; /* should not happen */
+ else
+ score = src_copied * MAX_SCORE / dst->size;
return score;
}
diff --git a/diffcore.h b/diffcore.h
index dba4f17..d31b3b4 100644
--- a/diffcore.h
+++ b/diffcore.h
@@ -17,8 +17,8 @@
*/
#define MAX_SCORE 60000.0
#define DEFAULT_RENAME_SCORE 30000 /* rename/copy similarity minimum (50%) */
-#define DEFAULT_BREAK_SCORE 30000 /* minimum for break to happen (50%)*/
-#define DEFAULT_MERGE_SCORE 48000 /* maximum for break-merge to happen (80%)*/
+#define DEFAULT_BREAK_SCORE 30000 /* minimum for break to happen (50%) */
+#define DEFAULT_MERGE_SCORE 36000 /* maximum for break-merge to happen 60%) */
#define MINIMUM_BREAK_SIZE 400 /* do not break a file smaller than this */
diff --git a/pack-check.c b/pack-check.c
index eca32b6..84ed90d 100644
--- a/pack-check.c
+++ b/pack-check.c
@@ -70,13 +70,17 @@ static int verify_packfile(struct packed_git *p)
}
+#define MAX_CHAIN 40
+
static void show_pack_info(struct packed_git *p)
{
struct pack_header *hdr;
int nr_objects, i;
+ unsigned int chain_histogram[MAX_CHAIN];
hdr = p->pack_base;
nr_objects = ntohl(hdr->hdr_entries);
+ memset(chain_histogram, 0, sizeof(chain_histogram));
for (i = 0; i < nr_objects; i++) {
unsigned char sha1[20], base_sha1[20];
@@ -97,11 +101,25 @@ static void show_pack_info(struct packed_git *p)
printf("%s ", sha1_to_hex(sha1));
if (!delta_chain_length)
printf("%-6s %lu %u\n", type, size, e.offset);
- else
+ else {
printf("%-6s %lu %u %u %s\n", type, size, e.offset,
delta_chain_length, sha1_to_hex(base_sha1));
+ if (delta_chain_length < MAX_CHAIN)
+ chain_histogram[delta_chain_length]++;
+ else
+ chain_histogram[0]++;
+ }
}
+ for (i = 0; i < MAX_CHAIN; i++) {
+ if (!chain_histogram[i])
+ continue;
+ printf("chain length %s %d: %d object%s\n",
+ i ? "=" : ">=",
+ i ? i : MAX_CHAIN,
+ chain_histogram[i],
+ 1 < chain_histogram[i] ? "s" : "");
+ }
}
int verify_pack(struct packed_git *p, int verbose)
diff --git a/pack-objects.c b/pack-objects.c
index 136a7f5..49357c6 100644
--- a/pack-objects.c
+++ b/pack-objects.c
@@ -32,9 +32,6 @@ struct object_entry {
* be used as the base objectto delta huge
* objects against.
*/
- int based_on_preferred; /* current delta candidate is a preferred
- * one, or delta against a preferred one.
- */
};
/*
@@ -824,8 +821,6 @@ static int try_delta(struct unpacked *cur, struct unpacked *old, unsigned max_de
{
struct object_entry *cur_entry = cur->entry;
struct object_entry *old_entry = old->entry;
- int old_preferred = (old_entry->preferred_base ||
- old_entry->based_on_preferred);
unsigned long size, oldsize, delta_size, sizediff;
long max_size;
void *delta_buf;
@@ -867,27 +862,8 @@ static int try_delta(struct unpacked *cur, struct unpacked *old, unsigned max_de
* delete).
*/
max_size = size / 2 - 20;
- if (cur_entry->delta) {
- if (cur_entry->based_on_preferred) {
- if (old_preferred)
- max_size = cur_entry->delta_size-1;
- else
- /* trying with non-preferred one when we
- * already have a delta based on preferred
- * one is pointless.
- */
- return -1;
- }
- else if (!old_preferred)
- max_size = cur_entry->delta_size-1;
- else
- /* otherwise... even if delta with a
- * preferred one produces a bigger result than
- * what we currently have, which is based on a
- * non-preferred one, it is OK.
- */
- ;
- }
+ if (cur_entry->delta)
+ max_size = cur_entry->delta_size-1;
if (sizediff >= max_size)
return -1;
delta_buf = diff_delta(old->data, oldsize,
@@ -897,7 +873,6 @@ static int try_delta(struct unpacked *cur, struct unpacked *old, unsigned max_de
cur_entry->delta = old_entry;
cur_entry->delta_size = delta_size;
cur_entry->depth = old_entry->depth + 1;
- cur_entry->based_on_preferred = old_preferred;
free(delta_buf);
return 0;
}
@@ -966,6 +941,15 @@ static void find_deltas(struct object_entry **list, int window, int depth)
if (try_delta(n, m, depth) < 0)
break;
}
+#if 0
+ /* if we made n a delta, and if n is already at max
+ * depth, leaving it in the window is pointless. we
+ * should evict it first.
+ * ... in theory only; somehow this makes things worse.
+ */
+ if (entry->delta && depth <= entry->depth)
+ continue;
+#endif
idx++;
if (idx >= window)
idx = 0;