--- /dev/null
+/** @file
+ * Defines Damerau-Levenshtein distance functions.
+ *
+ * @copyright 2016 Kevin Locke <kevin@kevinlocke.name>
+ * MIT license - see LICENSE file for details
+ */
+#include <stdlib.h> /* free, malloc */
+
+#include "edit_distance.h"
+#include "edit_distance-params.h"
+#include "edit_distance-private.h"
+
+ed_dist edit_distance_dl(const ed_elem *src, ed_size slen,
+ const ed_elem *tgt, ed_size tlen)
+{
+ /* Optimization: Avoid malloc when distance matrix can fit on the stack.
+ */
+ ed_dist stackdist[ED_STACK_ELEMS];
+
+ /* Lowrance-Wagner distance matrix, in row-major order. */
+ size_t matsize = ((size_t)slen + 2) * (tlen + 2);
+ ed_dist *distmem = matsize <= ED_STACK_ELEMS ? stackdist :
+ malloc(matsize * sizeof(ed_dist));
+ ed_dist *dist = distmem;
+
+#ifdef ED_HASH_ON_STACK
+ ed_size lasttgt[ED_HASH_MAX + 1] = { 0 };
+#else
+ ed_size *lasttgt = calloc(ED_HASH_MAX + 1, sizeof(ed_size));
+#endif
+
+ /* Upper bound on distance between strings. */
+ ed_dist maxdist = 0;
+
+#ifdef ED_DEL_COST_CONST
+ maxdist += (ed_dist)slen *ED_DEL_COST();
+#else
+ /* Lower-triangular matrix of deletion costs.
+ * delcost[i2, i1] is cost to delete src[i1..i2-1].
+ * delcost[i, i] is 0. */
+ ed_dist *delcost = malloc(ED_TMAT_SIZE(slen + 1) * sizeof(ed_dist));
+ ed_dist *delcostitr = delcost;
+ ed_dist *delcostprevitr = delcost;
+ *delcostitr++ = 0;
+ for (ed_size i2 = 1; i2 <= slen; ++i2) {
+ ed_dist costi2 = ED_DEL_COST(src[i2 - 1]);
+ for (ed_size i1 = 0; i1 < i2; ++i1) {
+ *delcostitr++ = *delcostprevitr++ + costi2;
+ }
+ *delcostitr++ = 0;
+ }
+ maxdist += delcost[ED_TMAT_IND(slen, 0)];
+#endif
+
+#ifdef ED_INS_COST_CONST
+ maxdist += (ed_dist)tlen *ED_INS_COST();
+#else
+ /* Lower-triangular matrix of insertion costs.
+ * inscost[j2, j1] is cost to insert tgt[j1..j2-1].
+ * inscost[j, j] is 0. */
+ ed_dist *inscost = malloc(ED_TMAT_SIZE(tlen + 1) * sizeof(ed_dist));
+ ed_dist *inscostitr = inscost;
+ ed_dist *inscostprevitr = inscost;
+ *inscostitr++ = 0;
+ for (ed_size j2 = 1; j2 <= tlen; ++j2) {
+ ed_dist costj2 = ED_INS_COST(tgt[j2 - 1]);
+ for (ed_size j1 = 0; j1 < j2; ++j1) {
+ *inscostitr++ = *inscostprevitr++ + costj2;
+ }
+ *inscostitr++ = 0;
+ }
+ maxdist += inscost[ED_TMAT_IND(tlen, 0)];
+#endif
+
+ /* Initialize first row with maximal cost */
+ for (ed_size i = 0; i < slen + 2; ++i) {
+ dist[i] = maxdist;
+ }
+
+ /* Position dist to match other algorithms. dist[-1] will be maxdist */
+ dist += slen + 3;
+
+ /* Initialize row with cost to delete src[0..i-1] */
+ dist[-1] = maxdist;
+ dist[0] = 0;
+ for (ed_size i = 1; i <= slen; ++i) {
+ dist[i] = dist[i - 1] + ED_DEL_COST(src[i - 1]);
+ }
+
+ for (ed_size j = 1; j <= tlen; ++j) {
+ /* Largest y < i such that src[y] = tgt[j] */
+ ed_size lastsrc = 0;
+ ed_dist *prevdist = dist;
+ dist += slen + 2;
+ dist[-1] = maxdist;
+ dist[0] = prevdist[0] + ED_INS_COST(tgt[j - 1]);
+
+ /* Loop invariant: dist[i] is the edit distance between first j
+ * elements of tgt and first i elements of src.
+ *
+ * Loop invariant: lasttgt[ED_HASH_ELEM(c)] holds the largest
+ * x < j such that tgt[x-1] = c or 0 if no such x exists.
+ */
+ for (ed_size i = 1; i <= slen; ++i) {
+ ed_size i1 = lastsrc;
+ ed_size j1 = lasttgt[ED_HASH_ELEM(src[i - 1])];
+
+ if (ED_ELEM_EQUAL(src[i - 1], tgt[j - 1])) {
+ /* Same as tgt upto j-2, src upto i-2. */
+ dist[i] = prevdist[i - 1];
+ lastsrc = i;
+ } else {
+ /* Insertion is tgt upto j-2, src upto i-1
+ * + insert tgt[j-1] */
+ ed_dist insdist =
+ prevdist[i] + ED_INS_COST(tgt[j - 1]);
+
+ /* Deletion is tgt upto j-1, src upto i-2
+ * + delete src[i-1] */
+ ed_dist deldist =
+ dist[i - 1] + ED_DEL_COST(src[i - 1]);
+
+ /* Substitution is tgt upto j-2, src upto i-2
+ * + substitute tgt[j-1] for src[i-1] */
+ ed_dist subdist = prevdist[i - 1] +
+ ED_SUB_COST(src[i - 1], tgt[j - 1]);
+
+ /* Use best distance available */
+ dist[i] = ED_MIN3(insdist, deldist, subdist);
+
+ ed_dist swpdist =
+ distmem[(size_t)j1 * (slen + 2) + i1];
+#ifdef ED_INS_COST_CONST
+ swpdist +=
+ (ed_dist)(j - j1 - 1) * ED_INS_COST();
+#else
+ swpdist += inscost[ED_TMAT_IND(j - 1, j1)];
+#endif
+#ifdef ED_TRA_COST_CONST
+ swpdist += ED_TRA_COST(,);
+#else
+ if (i1 > 0) {
+ swpdist +=
+ ED_TRA_COST(src[i1 - 1],
+ src[i - 1]);
+ }
+#endif
+#ifdef ED_DEL_COST_CONST
+ swpdist +=
+ (ed_dist)(i - i1 - 1) * ED_DEL_COST();
+#else
+ swpdist += delcost[ED_TMAT_IND(i - 1, i1)];
+#endif
+
+ dist[i] = ED_MIN2(dist[i], swpdist);
+ }
+ }
+
+ lasttgt[ED_HASH_ELEM(tgt[j - 1])] = j;
+ }
+
+#ifndef ED_HASH_ON_STACK
+ free(lasttgt);
+#endif
+
+#ifndef ED_DEL_COST_CONST
+ free(delcost);
+#endif
+
+#ifndef ED_INS_COST_CONST
+ free(inscost);
+#endif
+
+ ed_dist total = dist[slen];
+ if (distmem != stackdist) {
+ free(distmem);
+ }
+ return total;
+}
projects / ccan / blobdiff