From 15318cad33835e4e2dc620d033e43cd930676cdd Mon Sep 17 00:00:00 2001
From: kergoth <kergoth>
Date: Fri, 25 Jan 2002 22:14:26 +0000
Subject: Initial revision

---
(limited to 'rsync/search.c')

diff --git a/rsync/search.c b/rsync/search.c
new file mode 100644
index 0000000..3e0c5e2
--- a/dev/null
+++ b/rsync/search.c
@@ -0,0 +1,162 @@
+/*= -*- c-basic-offset: 4; indent-tabs-mode: nil; -*-
+ *
+ * librsync -- the library for network deltas
+ * $Id$
+ * 
+ * Copyright (C) 1999, 2000, 2001 by Martin Pool <mbp@samba.org>
+ * Copyright (C) 1999 by Andrew Tridgell
+ * 
+ * This program 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 2.1 of the License, or
+ * (at your option) any later version.
+ * 
+ * This program 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 program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+/* 
+ * This file contains code for searching the sumset for matching
+ * values.
+ */
+
+/* 
+ * TODO: The common case is that the next block in both streams
+ * match. Can we make that a bit faster at all?  We'd need to perhaps
+ * add a link forward between blocks in the sum_struct corresponding
+ * to the order they're found in the input; then before doing a search
+ * we can just check that pointer.
+ */
+
+#include <config_rsync.h>
+
+#include <string.h>
+#include <assert.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#include "rsync.h"
+#include "trace.h"
+#include "util.h"
+#include "sumset.h"
+#include "search.h"
+#include "checksum.h"
+
+
+#define TABLESIZE (1<<16)
+#define NULL_TAG (-1)
+
+
+#define gettag2(s1,s2) (((s1) + (s2)) & 0xFFFF)
+#define gettag(sum) gettag2((sum)&0xFFFF,(sum)>>16)
+
+
+static int
+rs_compare_targets(rs_target_t const *t1, rs_target_t const *t2)
+{
+    return ((int) t1->t - (int) t2->t);
+}
+
+
+rs_result
+rs_build_hash_table(rs_signature_t * sums)
+{
+    int                     i;
+
+    sums->tag_table = calloc(TABLESIZE, sizeof sums->tag_table[0]);
+    if (!sums->tag_table)
+        return RS_MEM_ERROR;
+    
+    if (sums->count > 0) {
+	sums->targets = calloc(sums->count, sizeof(rs_target_t));
+        if (!sums->targets)
+            return RS_MEM_ERROR;
+
+	for (i = 0; i < sums->count; i++) {
+	    sums->targets[i].i = i;
+	    sums->targets[i].t = gettag(sums->block_sigs[i].weak_sum);
+	}
+
+	/* FIXME: Perhaps if this operating system has comparison_fn_t
+         * like GNU, then use it in the cast.  But really does anyone
+         * care?  */
+	qsort(sums->targets, sums->count,
+	      sizeof(sums->targets[0]),
+              (int (*)(const void *, const void *)) rs_compare_targets);
+    }
+
+    for (i = 0; i < TABLESIZE; i++)
+	sums->tag_table[i] = NULL_TAG;
+
+    for (i = sums->count - 1; i >= 0; i--) {
+	sums->tag_table[sums->targets[i].t] = i;
+    }
+
+    rs_trace("done");
+    return RS_DONE;
+}
+
+
+
+/* 
+ * See if there is a match for the specified block INBUF..BLOCK_LEN in
+ * the checksum set, using precalculated WEAK_SUM.
+ *
+ * If we don't find a match on the weak checksum, then we just give
+ * up.  If we do find a weak match, then we proceed to calculate the
+ * strong checksum for the current block, and see if it will match
+ * anything.
+ */
+int
+rs_search_for_block(rs_weak_sum_t weak_sum,
+                    char const *inbuf, size_t block_len,
+                    rs_signature_t const *sig, rs_stats_t * stats,
+                    rs_long_t * match_where)
+{
+    int                     hash_tag = gettag(weak_sum);
+    int                     j = sig->tag_table[hash_tag];
+    rs_strong_sum_t         strong_sum;
+    int                     got_strong = 0;
+
+    if (j == NULL_TAG) {
+	return 0;
+    }
+
+    for (; j < sig->count && sig->targets[j].t == hash_tag; j++) {
+	int                     i = sig->targets[j].i;
+	int                     token;
+
+	if (weak_sum != sig->block_sigs[i].weak_sum)
+	    continue;
+
+	token = sig->block_sigs[i].i;
+
+	rs_trace("found weak match for %08x in token %d", weak_sum, token);
+
+	if (!got_strong) {
+	    rs_calc_strong_sum(inbuf, block_len, &strong_sum);
+	    got_strong = 1;
+	}
+
+	/* FIXME: Use correct dynamic sum length! */
+	if (memcmp(strong_sum, sig->block_sigs[i].strong_sum,
+                   sig->strong_sum_len) == 0) {
+	    /* XXX: This is a remnant of rsync: token number 1 is the
+	     * block at offset 0.  It would be good to clear this
+	     * up. */
+	    *match_where = (token - 1) * sig->block_len;
+	    return 1;
+	} else {
+	    rs_trace("this was a false positive, the strong sig doesn't match");
+	    stats->false_matches++;
+	}
+    }
+
+    return 0;
+}
--
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