* Add new algorithm based on diff algorithm to compare relatively short text parts

1 files changed, 379 insertions, 0 deletions

diff --git a/src/diff.c b/src/diff.c
new file mode 100644
index 000000000..a2e84349b
--- /dev/null
+++ b/src/diff.c
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+/* diff - compute a shortest edit script (SES) given two sequences
+ * Copyright (c) 2004 Michael B. Allen <mba2000 ioplex.com>
+ *
+ * The MIT License
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+/* This algorithm is basically Myers' solution to SES/LCS with
+ * the Hirschberg linear space refinement as described in the
+ * following publication:
+ *
+ *   E. Myers, ``An O(ND) Difference Algorithm and Its Variations,''
+ *   Algorithmica 1, 2 (1986), 251-266.
+ *   http://www.cs.arizona.edu/people/gene/PAPERS/diff.ps
+ *
+ * This is the same algorithm used by GNU diff(1).
+ */
+
+/* Copyright (c) 2010, Vsevolod Stakhov
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *       * Redistributions of source code must retain the above copyright
+ *         notice, this list of conditions and the following disclaimer.
+ *       * Redistributions in binary form must reproduce the above copyright
+ *         notice, this list of conditions and the following disclaimer in the
+ *         documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED ''AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL Rambler BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "config.h"
+#include "diff.h"
+
+
+#define FV(k) _v(ctx, (k), 0)
+#define RV(k) _v(ctx, (k), 1)
+
+#define MAX_DIFF 1024
+
+struct _ctx
+{
+	GArray *buf;
+	GArray *ses;
+	gint si;
+	gint dmax;
+};
+
+struct middle_snake
+{
+	gint x, y, u, v;
+};
+
+static
+void maybe_resize_array(GArray *arr, guint k)
+{
+	if (k > arr->len) {
+		g_array_set_size (arr, k);
+	}
+
+}
+
+static void
+_setv(struct _ctx *ctx, gint k, gint r, gint val)
+{
+	gint j;
+	gint *i;
+	/* Pack -N to N ginto 0 to N * 2
+	 */
+	j = k <= 0 ? -k * 4 + r : k * 4 + (r - 2);
+
+	maybe_resize_array (ctx->buf, j);
+	i = (gint *) &g_array_index (ctx->buf, gint, j);
+	*i = val;
+}
+
+static gint
+_v(struct _ctx *ctx, gint k, gint r)
+{
+	gint j;
+
+	j = k <= 0 ? -k * 4 + r : k * 4 + (r - 2);
+
+	return *((gint *) &g_array_index (ctx->buf, gint, j));
+}
+
+static gint
+_find_middle_snake(const void *a, gint aoff, gint n, const void *b,
+		gint boff, gint m, struct _ctx *ctx, struct middle_snake *ms)
+{
+	gint delta, odd, mid, d;
+
+	delta = n - m;
+	odd = delta & 1;
+	mid = (n + m) / 2;
+	mid += odd;
+
+	_setv (ctx, 1, 0, 0);
+	_setv (ctx, delta - 1, 1, n);
+
+	for (d = 0; d <= mid; d++) {
+		gint k, x, y;
+
+		if ((2 * d - 1) >= ctx->dmax) {
+			return ctx->dmax;
+		}
+
+		for (k = d; k >= -d; k -= 2) {
+			if (k == -d || (k != d && FV(k - 1) < FV(k + 1))) {
+				x = FV(k + 1);
+			}
+			else {
+				x = FV(k - 1) + 1;
+			}
+			y = x - k;
+
+			ms->x = x;
+			ms->y = y;
+			const guchar *a0 = (const guchar *) a + aoff;
+			const guchar *b0 = (const guchar *) b + boff;
+			while (x < n && y < m && a0[x] == b0[y]) {
+				x++;
+				y++;
+			}
+			_setv (ctx, k, 0, x);
+
+			if (odd && k >= (delta - (d - 1)) && k <= (delta + (d - 1))) {
+				if (x >= RV(k)) {
+					ms->u = x;
+					ms->v = y;
+					return 2 * d - 1;
+				}
+			}
+		}
+		for (k = d; k >= -d; k -= 2) {
+			gint kr = (n - m) + k;
+
+			if (k == d || (k != -d && RV(kr - 1) < RV(kr + 1))) {
+				x = RV(kr - 1);
+			}
+			else {
+				x = RV(kr + 1) - 1;
+			}
+			y = x - kr;
+
+			ms->u = x;
+			ms->v = y;
+			const guchar *a0 = (const guchar *) a + aoff;
+			const guchar *b0 = (const guchar *) b + boff;
+			while (x > 0 && y > 0 && a0[x - 1] == b0[y - 1]) {
+				x--;
+				y--;
+			}
+			_setv (ctx, kr, 1, x);
+
+			if (!odd && kr >= -d && kr <= d) {
+				if (x <= FV(kr)) {
+					ms->x = x;
+					ms->y = y;
+					return 2 * d;
+				}
+			}
+		}
+	}
+
+	errno = EFAULT;
+
+	return -1;
+}
+
+static void
+_edit(struct _ctx *ctx, gint op, gint off, gint len)
+{
+	struct diff_edit *e = NULL, newe;
+
+	if (len == 0 || ctx->ses == NULL) {
+		return;
+	}
+	/*
+	 * Add an edit to the SES (or
+	 * coalesce if the op is the same)
+	 */
+	if (ctx->ses->len != 0) {
+		e = &g_array_index (ctx->ses, struct diff_edit, ctx->ses->len - 1);
+	}
+	if (e == NULL || e->op != op) {
+		newe.op = op;
+		newe.off = off;
+		newe.len = len;
+		g_array_append_val (ctx->ses, newe);
+	}
+	else {
+		e->len += len;
+	}
+}
+
+static gint
+_ses(const void *a, gint aoff, gint n, const void *b, gint boff,
+		gint m, struct _ctx *ctx)
+{
+	struct middle_snake ms;
+	gint d;
+
+	if (n == 0) {
+		_edit (ctx, DIFF_INSERT, boff, m);
+		d = m;
+	}
+	else if (m == 0) {
+		_edit (ctx, DIFF_DELETE, aoff, n);
+		d = n;
+	}
+	else {
+		/* Find the middle "snake" around which we
+		 * recursively solve the sub-problems.
+		 */
+		d = _find_middle_snake (a, aoff, n, b, boff, m, ctx, &ms);
+		if (d == -1) {
+			return -1;
+		}
+		else if (d >= ctx->dmax) {
+			return ctx->dmax;
+		}
+		else if (ctx->ses == NULL) {
+			return d;
+		}
+		else if (d > 1) {
+			if (_ses (a, aoff, ms.x, b, boff, ms.y, ctx) == -1) {
+				return -1;
+			}
+
+			_edit (ctx, DIFF_MATCH, aoff + ms.x, ms.u - ms.x);
+
+			aoff += ms.u;
+			boff += ms.v;
+			n -= ms.u;
+			m -= ms.v;
+			if (_ses (a, aoff, n, b, boff, m, ctx) == -1) {
+				return -1;
+			}
+		}
+		else {
+			gint x = ms.x;
+			gint u = ms.u;
+
+			/* There are only 4 base cases when the
+			 * edit distance is 1.
+			 *
+			 * n > m   m > n
+			 *
+			 *   -       |
+			 *    \       \    x != u
+			 *     \       \
+			 *
+			 *   \       \
+			 *    \       \    x == u
+			 *     -       |
+			 */
+
+			if (m > n) {
+				if (x == u) {
+					_edit (ctx, DIFF_MATCH, aoff, n);
+					_edit (ctx, DIFF_INSERT, boff + (m - 1), 1);
+				}
+				else {
+					_edit (ctx, DIFF_INSERT, boff, 1);
+					_edit (ctx, DIFF_MATCH, aoff, n);
+				}
+			}
+			else {
+				if (x == u) {
+					_edit (ctx, DIFF_MATCH, aoff, m);
+					_edit (ctx, DIFF_DELETE, aoff + (n - 1), 1);
+				}
+				else {
+					_edit (ctx, DIFF_DELETE, aoff, 1);
+					_edit (ctx, DIFF_MATCH, aoff + 1, m);
+				}
+			}
+		}
+	}
+
+	return d;
+}
+
+gint
+rspamd_diff(const void *a, gint aoff, gint n, const void *b, gint boff, gint m,
+		gint dmax, GArray *ses, gint *sn)
+{
+	struct _ctx ctx;
+	gint d, x, y;
+	struct diff_edit *e = NULL;
+	GArray *tmp;
+
+	tmp = g_array_sized_new (FALSE, TRUE, sizeof(gint), dmax);
+	ctx.buf = tmp;
+	ctx.ses = ses;
+	ctx.si = 0;
+	ctx.dmax = dmax;
+
+	/* The _ses function assumes the SES will begin or end with a delete
+	 * or insert. The following will insure this is true by eating any
+	 * beginning matches. This is also a quick to process sequences
+	 * that match entirely.
+	 */
+	x = y = 0;
+	const guchar *a0 = (const guchar *) a + aoff;
+	const guchar *b0 = (const guchar *) b + boff;
+	while (x < n && y < m && a0[x] == b0[y]) {
+		x++;
+		y++;
+	}
+	_edit (&ctx, DIFF_MATCH, aoff, x);
+
+	if ((d = _ses (a, aoff + x, n - x, b, boff + y, m - y, &ctx)) == -1) {
+		g_array_free (tmp, TRUE);
+		return -1;
+	}
+	if (ses && sn) {
+		*sn = e->op ? ctx.si + 1 : 0;
+	}
+
+	g_array_free (tmp, TRUE);
+	return d;
+}
+
+guint32
+compare_diff_distance (f_str_t *s1, f_str_t *s2)
+{
+	GArray *ses;
+	struct diff_edit *e;
+	gint i;
+	guint32 distance = 0;
+
+	ses = g_array_sized_new (FALSE, TRUE, sizeof (struct diff_edit), MAX_DIFF);
+
+	if (rspamd_diff (s1->begin, 0, s1->len,
+				s2->begin, 0, s2->len, MAX_DIFF, ses, NULL) == -1) {
+		/* Diff failed, strings are different */
+		g_array_free (ses, TRUE);
+		return 0;
+	}
+
+	for (i = 0; i < ses->len; i ++) {
+		e = &g_array_index(ses, struct diff_edit, i);
+		if (e->op != DIFF_MATCH) {
+			distance += e->len;
+		}
+	}
+
+	g_array_free (ses, TRUE);
+	return 100 - (2 * distance * 100) / (s1->len + s2->len);
+}