--- /dev/null
+/* Functions to make fuzzy comparisons between strings
+ Copyright (C) 1988-1989, 1992-1993, 1995, 2001-2003, 2006 Free Software Foundation, Inc.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2, 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 General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software Foundation,
+ Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+
+
+ Derived from GNU diff 2.7, analyze.c et al.
+
+ The basic idea is to consider two vectors as similar if, when
+ transforming the first vector into the second vector through a
+ sequence of edits (inserts and deletes of one element each),
+ this sequence is short - or equivalently, if the ordered list
+ of elements that are untouched by these edits is long. For a
+ good introduction to the subject, read about the "Levenshtein
+ distance" in Wikipedia.
+
+ The basic algorithm is described in:
+ "An O(ND) Difference Algorithm and its Variations", Eugene Myers,
+ Algorithmica Vol. 1 No. 2, 1986, pp. 251-266;
+ see especially section 4.2, which describes the variation used below.
+
+ The basic algorithm was independently discovered as described in:
+ "Algorithms for Approximate String Matching", E. Ukkonen,
+ Information and Control Vol. 64, 1985, pp. 100-118.
+
+ Unless the 'find_minimal' flag is set, this code uses the TOO_EXPENSIVE
+ heuristic, by Paul Eggert, to limit the cost to O(N**1.5 log N)
+ at the price of producing suboptimal output for large inputs with
+ many differences. */
+
+#include <config.h>
+
+/* Specification. */
+#include "fstrcmp.h"
+
+#include <string.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <limits.h>
+
+#include "lock.h"
+#include "tls.h"
+#include "minmax.h"
+#include "xalloc.h"
+
+#ifndef uintptr_t
+# define uintptr_t unsigned long
+#endif
+
+
+#define ELEMENT char
+#define EQUAL(x,y) ((x) == (y))
+#define OFFSET int
+#define EXTRA_CONTEXT_FIELDS \
+ /* The number of elements inserted or deleted. */ \
+ int xvec_edit_count; \
+ int yvec_edit_count;
+#define NOTE_DELETE(ctxt, xoff) ctxt->xvec_edit_count++
+#define NOTE_INSERT(ctxt, yoff) ctxt->yvec_edit_count++
+/* We don't need USE_HEURISTIC, since it is unlikely in typical uses of
+ fstrcmp(). */
+#include "diffseq.h"
+
+
+/* Because fstrcmp is typically called multiple times, attempt to minimize
+ the number of memory allocations performed. Thus, let a call reuse the
+ memory already allocated by the previous call, if it is sufficient.
+ To make it multithread-safe, without need for a lock that protects the
+ already allocated memory, store the allocated memory per thread. Free
+ it only when the thread exits. */
+
+static gl_tls_key_t buffer_key; /* TLS key for a 'int *' */
+static gl_tls_key_t bufmax_key; /* TLS key for a 'size_t' */
+
+static void
+keys_init (void)
+{
+ gl_tls_key_init (buffer_key, free);
+ gl_tls_key_init (bufmax_key, NULL);
+ /* The per-thread initial values are NULL and 0, respectively. */
+}
+
+/* Ensure that keys_init is called once only. */
+gl_once_define(static, keys_init_once)
+
+
+/* NAME
+ fstrcmp - fuzzy string compare
+
+ SYNOPSIS
+ double fstrcmp(const char *, const char *);
+
+ DESCRIPTION
+ The fstrcmp function may be used to compare two string for
+ similarity. It is very useful in reducing "cascade" or
+ "secondary" errors in compilers or other situations where
+ symbol tables occur.
+
+ RETURNS
+ double; 0 if the strings are entirly dissimilar, 1 if the
+ strings are identical, and a number in between if they are
+ similar. */
+
+double
+fstrcmp (const char *string1, const char *string2)
+{
+ struct context ctxt;
+ int xvec_length;
+ int yvec_length;
+ int i;
+
+ size_t fdiag_len;
+ int *buffer;
+ size_t bufmax;
+
+ /* set the info for each string. */
+ ctxt.xvec = string1;
+ xvec_length = strlen (string1);
+ ctxt.yvec = string2;
+ yvec_length = strlen (string2);
+
+ /* short-circuit obvious comparisons */
+ if (xvec_length == 0 && yvec_length == 0)
+ return 1.0;
+ if (xvec_length == 0 || yvec_length == 0)
+ return 0.0;
+
+ /* Set TOO_EXPENSIVE to be approximate square root of input size,
+ bounded below by 256. */
+ ctxt.too_expensive = 1;
+ for (i = xvec_length + yvec_length;
+ i != 0;
+ i >>= 2)
+ ctxt.too_expensive <<= 1;
+ if (ctxt.too_expensive < 256)
+ ctxt.too_expensive = 256;
+
+ /* Allocate memory for fdiag and bdiag from a thread-local pool. */
+ fdiag_len = xvec_length + yvec_length + 3;
+ gl_once (keys_init_once, keys_init);
+ buffer = (int *) gl_tls_get (buffer_key);
+ bufmax = (size_t) (uintptr_t) gl_tls_get (bufmax_key);
+ if (fdiag_len > bufmax)
+ {
+ /* Need more memory. */
+ bufmax = 2 * bufmax;
+ if (fdiag_len > bufmax)
+ bufmax = fdiag_len;
+ /* Calling xrealloc would be a waste: buffer's contents does not need
+ to be preserved. */
+ if (buffer != NULL)
+ free (buffer);
+ buffer = (int *) xnmalloc (bufmax, 2 * sizeof (int));
+ gl_tls_set (buffer_key, buffer);
+ gl_tls_set (bufmax_key, (void *) (uintptr_t) bufmax);
+ }
+ ctxt.fdiag = buffer + yvec_length + 1;
+ ctxt.bdiag = ctxt.fdiag + fdiag_len;
+
+ /* Now do the main comparison algorithm */
+ ctxt.xvec_edit_count = 0;
+ ctxt.yvec_edit_count = 0;
+ compareseq (0, xvec_length, 0, yvec_length, 0,
+ &ctxt);
+
+ /* The result is
+ ((number of chars in common) / (average length of the strings)).
+ This is admittedly biased towards finding that the strings are
+ similar, however it does produce meaningful results. */
+ return ((double) (xvec_length + yvec_length
+ - ctxt.yvec_edit_count - ctxt.xvec_edit_count)
+ / (xvec_length + yvec_length));
+}
--- /dev/null
+/* Fuzzy string comparison.
+ Copyright (C) 1995, 2000, 2002-2003, 2006 Free Software Foundation, Inc.
+
+ This file was written by Peter Miller <pmiller@agso.gov.au>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, 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 General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software Foundation,
+Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
+
+#ifndef _FSTRCMP_H
+#define _FSTRCMP_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Fuzzy compare of S1 and S2. Return a measure for the similarity of S1
+ and S1. The higher the result, the more similar the strings are. */
+extern double fstrcmp (const char *s1, const char *s2);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
projects / gnulib.git / commitdiff