Hash :
9c454b00
Author :
Date :
2013-01-11T22:13:02
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/*
* Copyright (C) the libgit2 contributors. All rights reserved.
*
* This file is part of libgit2, distributed under the GNU GPL v2 with
* a Linking Exception. For full terms see the included COPYING file.
*/
#include "buf_text.h"
#include "fileops.h"
int git_buf_text_puts_escaped(
git_buf *buf,
const char *string,
const char *esc_chars,
const char *esc_with)
{
const char *scan;
size_t total = 0, esc_len = strlen(esc_with), count;
if (!string)
return 0;
for (scan = string; *scan; ) {
/* count run of non-escaped characters */
count = strcspn(scan, esc_chars);
total += count;
scan += count;
/* count run of escaped characters */
count = strspn(scan, esc_chars);
total += count * (esc_len + 1);
scan += count;
}
if (git_buf_grow(buf, buf->size + total + 1) < 0)
return -1;
for (scan = string; *scan; ) {
count = strcspn(scan, esc_chars);
memmove(buf->ptr + buf->size, scan, count);
scan += count;
buf->size += count;
for (count = strspn(scan, esc_chars); count > 0; --count) {
/* copy escape sequence */
memmove(buf->ptr + buf->size, esc_with, esc_len);
buf->size += esc_len;
/* copy character to be escaped */
buf->ptr[buf->size] = *scan;
buf->size++;
scan++;
}
}
buf->ptr[buf->size] = '\0';
return 0;
}
void git_buf_text_unescape(git_buf *buf)
{
buf->size = git__unescape(buf->ptr);
}
int git_buf_text_common_prefix(git_buf *buf, const git_strarray *strings)
{
size_t i;
const char *str, *pfx;
git_buf_clear(buf);
if (!strings || !strings->count)
return 0;
/* initialize common prefix to first string */
if (git_buf_sets(buf, strings->strings[0]) < 0)
return -1;
/* go through the rest of the strings, truncating to shared prefix */
for (i = 1; i < strings->count; ++i) {
for (str = strings->strings[i], pfx = buf->ptr;
*str && *str == *pfx; str++, pfx++)
/* scanning */;
git_buf_truncate(buf, pfx - buf->ptr);
if (!buf->size)
break;
}
return 0;
}
bool git_buf_text_is_binary(const git_buf *buf)
{
const char *scan = buf->ptr, *end = buf->ptr + buf->size;
int printable = 0, nonprintable = 0;
while (scan < end) {
unsigned char c = *scan++;
if (c > 0x1F && c < 0x7F)
printable++;
else if (c == '\0')
return true;
else if (!git__isspace(c))
nonprintable++;
}
return ((printable >> 7) < nonprintable);
}
bool git_buf_text_contains_nul(const git_buf *buf)
{
return (memchr(buf->ptr, '\0', buf->size) != NULL);
}
int git_buf_text_detect_bom(git_bom_t *bom, const git_buf *buf, size_t offset)
{
const char *ptr;
size_t len;
*bom = GIT_BOM_NONE;
/* need at least 2 bytes after offset to look for any BOM */
if (buf->size < offset + 2)
return 0;
ptr = buf->ptr + offset;
len = buf->size - offset;
switch (*ptr++) {
case 0:
if (len >= 4 && ptr[0] == 0 && ptr[1] == '\xFE' && ptr[2] == '\xFF') {
*bom = GIT_BOM_UTF32_BE;
return 4;
}
break;
case '\xEF':
if (len >= 3 && ptr[0] == '\xBB' && ptr[1] == '\xBF') {
*bom = GIT_BOM_UTF8;
return 3;
}
break;
case '\xFE':
if (*ptr == '\xFF') {
*bom = GIT_BOM_UTF16_BE;
return 2;
}
break;
case '\xFF':
if (*ptr != '\xFE')
break;
if (len >= 4 && ptr[1] == 0 && ptr[2] == 0) {
*bom = GIT_BOM_UTF32_LE;
return 4;
} else {
*bom = GIT_BOM_UTF16_LE;
return 2;
}
break;
default:
break;
}
return 0;
}
bool git_buf_text_gather_stats(
git_buf_text_stats *stats, const git_buf *buf, bool skip_bom)
{
const char *scan = buf->ptr, *end = buf->ptr + buf->size;
int skip;
memset(stats, 0, sizeof(*stats));
/* BOM detection */
skip = git_buf_text_detect_bom(&stats->bom, buf, 0);
if (skip_bom)
scan += skip;
/* Ignore EOF character */
if (buf->size > 0 && end[-1] == '\032')
end--;
/* Counting loop */
while (scan < end) {
unsigned char c = *scan++;
if ((c > 0x1F && c < 0x7F) || c > 0x9f)
stats->printable++;
else switch (c) {
case '\0':
stats->nul++;
stats->nonprintable++;
break;
case '\n':
stats->lf++;
break;
case '\r':
stats->cr++;
if (scan < end && *scan == '\n')
stats->crlf++;
break;
case '\t': case '\f': case '\v': case '\b': case 0x1b: /*ESC*/
stats->printable++;
break;
default:
stats->nonprintable++;
break;
}
}
return (stats->nul > 0 ||
((stats->printable >> 7) < stats->nonprintable));
}
#define SIMILARITY_MAXRUN 256
#define SIMILARITY_HASH_START 5381
#define SIMILARITY_HASH_UPDATE(S,N) (((S) << 5) + (S) + (uint32_t)(N))
enum {
SIMILARITY_FORMAT_UNKNOWN = 0,
SIMILARITY_FORMAT_TEXT = 1,
SIMILARITY_FORMAT_BINARY = 2
};
struct git_buf_text_hashsig {
uint32_t *hashes;
size_t size;
size_t asize;
unsigned int format : 2;
unsigned int pairs : 1;
};
static int similarity_advance(git_buf_text_hashsig *sig, uint32_t hash)
{
if (sig->size >= sig->asize) {
size_t new_asize = sig->asize + 512;
uint32_t *new_hashes =
git__realloc(sig->hashes, new_asize * sizeof(uint32_t));
GITERR_CHECK_ALLOC(new_hashes);
sig->hashes = new_hashes;
sig->asize = new_asize;
}
sig->hashes[sig->size++] = hash;
return 0;
}
static int similarity_add_hashes(
git_buf_text_hashsig *sig,
uint32_t *hash_start,
size_t *hashlen_start,
const char *ptr,
size_t len)
{
int error = 0;
const char *scan = ptr, *scan_end = ptr + len;
char term = (sig->format == SIMILARITY_FORMAT_TEXT) ? '\n' : '\0';
uint32_t hash = hash_start ? *hash_start : SIMILARITY_HASH_START;
size_t hashlen = hashlen_start ? *hashlen_start : 0;
while (scan < scan_end) {
char ch = *scan++;
if (ch == term || hashlen >= SIMILARITY_MAXRUN) {
if ((error = similarity_advance(sig, hash)) < 0)
break;
hash = SIMILARITY_HASH_START;
hashlen = 0;
/* skip run of terminators */
while (scan < scan_end && *scan == term)
scan++;
} else {
hash = SIMILARITY_HASH_UPDATE(hash, ch);
hashlen++;
}
}
if (hash_start)
*hash_start = hash;
if (hashlen_start)
*hashlen_start = hashlen;
/* if we're not saving intermediate state, add final hash as needed */
if (!error && !hash_start && hashlen > 0)
error = similarity_advance(sig, hash);
return error;
}
/*
* Decide if \0 or \n terminated runs are a better choice for hashes
*/
static void similarity_guess_format(
git_buf_text_hashsig *sig, const char *ptr, size_t len)
{
size_t lines = 0, line_length = 0, max_line_length = 0;
size_t runs = 0, run_length = 0, max_run_length = 0;
/* don't process more than 4k of data for this */
if (len > 4096)
len = 4096;
/* gather some stats */
while (len--) {
char ch = *ptr++;
if (ch == '\0') {
runs++;
if (max_run_length < run_length)
max_run_length = run_length;
run_length = 0;
} else if (ch == '\n') {
lines++;
if (max_line_length < line_length)
max_line_length = line_length;
line_length = 0;
} else {
run_length++;
line_length++;
}
}
/* the following heuristic could probably be improved */
if (lines > runs)
sig->format = SIMILARITY_FORMAT_TEXT;
else if (runs > 0)
sig->format = SIMILARITY_FORMAT_BINARY;
else
sig->format = SIMILARITY_FORMAT_UNKNOWN;
}
static int similarity_compare_score(const void *a, const void *b)
{
uint32_t av = *(uint32_t *)a, bv = *(uint32_t *)b;
return (av < bv) ? -1 : (av > bv) ? 1 : 0;
}
static int similarity_finalize_hashes(
git_buf_text_hashsig *sig, bool generate_pairs)
{
if (!sig->size)
return 0;
/* create pairwise hashes if requested */
if (generate_pairs) {
size_t i, needed_size = sig->size * 2 - 1;
if (needed_size > sig->asize) {
uint32_t *new_hashes =
git__realloc(sig->hashes, needed_size * sizeof(uint32_t));
GITERR_CHECK_ALLOC(new_hashes);
sig->hashes = new_hashes;
sig->asize = needed_size;
}
for (i = 1; i < sig->size; ++i)
sig->hashes[sig->size + i - 1] =
SIMILARITY_HASH_UPDATE(sig->hashes[i - 1], sig->hashes[i]);
sig->pairs = 1;
}
/* sort all hashes */
qsort(sig->hashes, sig->size, sizeof(uint32_t), similarity_compare_score);
if (generate_pairs)
qsort(&sig->hashes[sig->size], sig->size - 1, sizeof(uint32_t),
similarity_compare_score);
return 0;
}
int git_buf_text_hashsig_create(
git_buf_text_hashsig **out,
const git_buf *buf,
bool generate_pairs)
{
int error;
git_buf_text_hashsig *sig = git__calloc(1, sizeof(git_buf_text_hashsig));
GITERR_CHECK_ALLOC(sig);
similarity_guess_format(sig, buf->ptr, buf->size);
error = similarity_add_hashes(sig, NULL, NULL, buf->ptr, buf->size);
if (!error)
error = similarity_finalize_hashes(sig, generate_pairs);
if (!error)
*out = sig;
else
git_buf_text_hashsig_free(sig);
return error;
}
int git_buf_text_hashsig_create_fromfile(
git_buf_text_hashsig **out,
const char *path,
bool generate_pairs)
{
char buf[4096];
ssize_t buflen = 0;
uint32_t hash = SIMILARITY_HASH_START;
size_t hashlen = 0;
int error = 0, fd;
git_buf_text_hashsig *sig = git__calloc(1, sizeof(git_buf_text_hashsig));
GITERR_CHECK_ALLOC(sig);
if ((fd = git_futils_open_ro(path)) < 0) {
git__free(sig);
return fd;
}
while (!error && (buflen = p_read(fd, buf, sizeof(buf))) > 0) {
if (sig->format == SIMILARITY_FORMAT_UNKNOWN)
similarity_guess_format(sig, buf, buflen);
error = similarity_add_hashes(sig, &hash, &hashlen, buf, buflen);
}
if (buflen < 0) {
giterr_set(GITERR_OS,
"Read error on '%s' while calculating similarity hashes", path);
error = (int)buflen;
}
p_close(fd);
if (!error && hashlen > 0)
error = similarity_advance(sig, hash);
if (!error)
error = similarity_finalize_hashes(sig, generate_pairs);
if (!error)
*out = sig;
else
git_buf_text_hashsig_free(sig);
return error;
}
void git_buf_text_hashsig_free(git_buf_text_hashsig *sig)
{
if (!sig)
return;
if (sig->hashes) {
git__free(sig->hashes);
sig->hashes = NULL;
}
git__free(sig);
}
int git_buf_text_hashsig_compare(
const git_buf_text_hashsig *a,
const git_buf_text_hashsig *b,
int scale)
{
size_t matches = 0, pairs = 0, total = 0, i, j;
if (a->format != b->format || !a->size || !b->size)
return 0;
if (scale <= 0)
scale = 100;
/* hash lists are sorted - just look for overlap vs total */
for (i = 0, j = 0; i < a->size && j < b->size; ) {
uint32_t av = a->hashes[i];
uint32_t bv = b->hashes[j];
if (av < bv)
++i;
else if (av > bv)
++j;
else {
++i; ++j;
++matches;
}
}
total = (a->size + b->size);
if (a->pairs && b->pairs) {
for (i = 0, j = 0; i < a->size - 1 && j < b->size - 1; ) {
uint32_t av = a->hashes[i + a->size];
uint32_t bv = b->hashes[j + b->size];
if (av < bv)
++i;
else if (av > bv)
++j;
else {
++i; ++j;
++pairs;
}
}
total += (a->size + b->size - 2);
}
return (int)(scale * 2 * (matches + pairs) / total);
}