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/*
* Copyright (C) 2015 Colin Walters <walters@verbum.org>
*
* SPDX-License-Identifier: LGPL-2.0+
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library. If not, see <https://www.gnu.org/licenses/>.
*/
#include "config.h"
#include <string.h>
#include <zlib.h>
#include "ostree-rollsum.h"
#include "libglnx.h"
#include "bupsplit.h"
#define ROLLSUM_BLOB_MAX (8192*4)
static GHashTable *
rollsum_chunks_crc32 (GBytes *bytes)
{
gsize start = 0;
gboolean rollsum_end = FALSE;
GHashTable *ret_rollsums = NULL;
const guint8 *buf;
gsize buflen;
gsize remaining;
ret_rollsums = g_hash_table_new_full (NULL, NULL, NULL, (GDestroyNotify)g_ptr_array_unref);
buf = g_bytes_get_data (bytes, &buflen);
remaining = buflen;
while (remaining > 0)
{
int offset, bits;
if (!rollsum_end)
{
offset = bupsplit_find_ofs (buf + start, MIN(G_MAXINT32, remaining), &bits);
if (offset == 0)
{
rollsum_end = TRUE;
offset = MIN(ROLLSUM_BLOB_MAX, remaining);
}
else if (offset > ROLLSUM_BLOB_MAX)
offset = ROLLSUM_BLOB_MAX;
}
else
offset = MIN(ROLLSUM_BLOB_MAX, remaining);
/* Use zlib's crc32 */
{ guint32 crc = crc32 (0L, NULL, 0);
GVariant *val;
GPtrArray *matches;
crc = crc32 (crc, buf, offset);
val = g_variant_ref_sink (g_variant_new ("(utt)", crc, (guint64) start, (guint64)offset));
matches = g_hash_table_lookup (ret_rollsums, GUINT_TO_POINTER (crc));
if (!matches)
{
matches = g_ptr_array_new_with_free_func ((GDestroyNotify)g_variant_unref);
g_hash_table_insert (ret_rollsums, GUINT_TO_POINTER (crc), matches);
}
g_ptr_array_add (matches, val);
}
start += offset;
remaining -= offset;
}
return ret_rollsums;
}
static gint
compare_matches (const void *app,
const void *bpp)
{
GVariant **avpp = (GVariant**)app;
GVariant *a = *avpp;
GVariant **bvpp = (GVariant**)bpp;
GVariant *b = *bvpp;
guint64 a_start, b_start;
g_variant_get_child (a, 2, "t", &a_start);
g_variant_get_child (b, 2, "t", &b_start);
g_assert_cmpint (a_start, !=, b_start);
if (a_start < b_start)
return -1;
return 1;
}
OstreeRollsumMatches *
_ostree_compute_rollsum_matches (GBytes *from,
GBytes *to)
{
OstreeRollsumMatches *ret_rollsum = NULL;
g_autoptr(GHashTable) from_rollsum = NULL;
g_autoptr(GHashTable) to_rollsum = NULL;
g_autoptr(GPtrArray) matches = NULL;
const guint8 *from_buf;
gsize from_len;
const guint8 *to_buf;
gsize to_len;
gpointer hkey, hvalue;
GHashTableIter hiter;
ret_rollsum = g_new0 (OstreeRollsumMatches, 1);
matches = g_ptr_array_new_with_free_func ((GDestroyNotify)g_variant_unref);
from_buf = g_bytes_get_data (from, &from_len);
to_buf = g_bytes_get_data (to, &to_len);
from_rollsum = rollsum_chunks_crc32 (from);
to_rollsum = rollsum_chunks_crc32 (to);
g_hash_table_iter_init (&hiter, to_rollsum);
while (g_hash_table_iter_next (&hiter, &hkey, &hvalue))
{
GPtrArray *to_chunks = hvalue;
GPtrArray *from_chunks;
from_chunks = g_hash_table_lookup (from_rollsum, hkey);
if (from_chunks != NULL)
{
guint i;
ret_rollsum->crcmatches++;
for (i = 0; i < to_chunks->len; i++)
{
GVariant *to_chunk = to_chunks->pdata[i];
guint64 to_start, to_offset;
guint32 tocrc;
guint j;
g_variant_get (to_chunk, "(utt)", &tocrc, &to_start, &to_offset);
for (j = 0; j < from_chunks->len; j++)
{
GVariant *from_chunk = from_chunks->pdata[j];
guint32 fromcrc;
guint64 from_start, from_offset;
g_variant_get (from_chunk, "(utt)", &fromcrc, &from_start, &from_offset);
g_assert (fromcrc == tocrc);
/* Same crc32 but different length, skip it. */
if (to_offset != from_offset)
continue;
/* Rsync uses a cryptographic checksum, but let's be
* very conservative here and just memcmp.
*/
if (memcmp (from_buf + from_start, to_buf + to_start, to_offset) == 0)
{
GVariant *match = g_variant_new ("(uttt)", fromcrc, to_offset, to_start, from_start);
ret_rollsum->bufmatches++;
ret_rollsum->match_size += to_offset;
g_ptr_array_add (matches, g_variant_ref_sink (match));
break; /* Don't need any more matches */
}
}
}
}
ret_rollsum->total += to_chunks->len;
}
g_ptr_array_sort (matches, compare_matches);
ret_rollsum->from_rollsums = from_rollsum; from_rollsum = NULL;
ret_rollsum->to_rollsums = to_rollsum; to_rollsum = NULL;
ret_rollsum->matches = matches; matches = NULL;
return ret_rollsum;
}
void
_ostree_rollsum_matches_free (OstreeRollsumMatches *rollsum)
{
g_hash_table_unref (rollsum->to_rollsums);
g_hash_table_unref (rollsum->from_rollsums);
g_ptr_array_unref (rollsum->matches);
g_free (rollsum);
}
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