edit_distance: calculate edit distance between strings

[ccan] / ccan / edit_distance / edit_distance.c

diff --git a/ccan/edit_distance/edit_distance.c b/ccan/edit_distance/edit_distance.c
new file mode 100644 (file)
index 0000000..82379d0
--- /dev/null
+++ b/ccan/edit_distance/edit_distance.c
@@ -0,0 +1,116 @@
+/** @file
+ * Defines shared edit distance functions.
+ *
+ * @copyright 2016 Kevin Locke <kevin@kevinlocke.name>
+ *            MIT license - see LICENSE file for details
+ */
+#include "edit_distance-params.h"
+#include "edit_distance-private.h"
+
+ed_dist edit_distance(const ed_elem *src, ed_size slen,
+                     const ed_elem *tgt, ed_size tlen, enum ed_measure measure)
+{
+       /* Remove common prefix. */
+       while (slen > 0 && tlen > 0 && ED_ELEM_EQUAL(src[0], tgt[0])) {
+               ++src;
+               ++tgt;
+               --slen;
+               --tlen;
+       }
+
+       /* Remove common suffix. */
+       while (slen > 0 && tlen > 0 &&
+              ED_ELEM_EQUAL(src[slen - 1], tgt[tlen - 1])) {
+               --slen;
+               --tlen;
+       }
+
+#if defined(ED_COST_IS_SYMMETRIC)
+       /* Use smaller array for src. */
+       if (slen > tlen) {
+               ED_SWAP(src, tgt, const ed_elem *);
+               ED_SWAP(slen, tlen, ed_size);
+       }
+#endif
+
+       /* Early return when all insertions. */
+       if (slen == 0) {
+#ifdef ED_INS_COST_CONST
+               return (ed_dist)tlen *ED_INS_COST();
+#else
+               ed_dist result = 0;
+               for (ed_size i = 0; i < tlen; ++i) {
+                       result += ED_INS_COST(tgt[i]);
+               }
+               return result;
+#endif
+       }
+#ifndef ED_COST_IS_SYMMETRIC
+       /* Early return when all deletions. */
+       if (tlen == 0) {
+# ifdef ED_DEL_COST_CONST
+               return (ed_dist)slen *ED_DEL_COST();
+# else
+               ed_dist result = 0;
+               for (ed_size i = 0; i < slen; ++i) {
+                       result += ED_DEL_COST(src[i]);
+               }
+               return result;
+# endif
+       }
+#endif
+
+#if defined(ED_HAS_ELEM) && \
+               defined(ED_INS_COST_CONST) && \
+               defined(ED_SUB_COST_CONST)
+       /* Fast search for single-element source. */
+       if (slen == 1) {
+               /* Always tlen - 1 inserts (of non-src elements). */
+               ed_dist result = (ed_dist)(tlen - 1) * ED_INS_COST();
+               if (!ED_HAS_ELEM(tgt, src[0], tlen)) {
+                       if (measure == EDIT_DISTANCE_LCS) {
+                               /* If src is not present, delete + insert. */
+                               result += ED_DEL_COST(src[0]) + ED_INS_COST();
+                       } else {
+                               /* If src is not present, substitute it out. */
+                               result += ED_SUB_COST(,);
+                       }
+               }
+               return result;
+       }
+#endif
+
+#if !defined(ED_COST_IS_SYMMETRIC) && \
+               defined(ED_HAS_ELEM) && \
+               defined(ED_DEL_COST_CONST) && \
+               defined(ED_SUB_COST_CONST)
+       /* Fast search for single-element target. */
+       if (tlen == 1) {
+               /* Always slen - 1 deletes (of non-tgt elements). */
+               ed_dist result = (ed_dist)(slen - 1) * ED_DEL_COST();
+               if (!ED_HAS_ELEM(src, tgt[0], slen)) {
+                       if (measure == EDIT_DISTANCE_LCS) {
+                               /* If tgt is not present, delete + insert. */
+                               result += ED_INS_COST(tgt[0]) + ED_DEL_COST();
+                       } else {
+                               /* If tgt is not present, substitute it out. */
+                               result += ED_SUB_COST(,);
+                       }
+               }
+               return result;
+       }
+#endif
+
+       switch (measure) {
+       case EDIT_DISTANCE_LCS:
+               return edit_distance_lcs(src, slen, tgt, tlen);
+       case EDIT_DISTANCE_LEV:
+               return edit_distance_lev(src, slen, tgt, tlen);
+       case EDIT_DISTANCE_RDL:
+               return edit_distance_rdl(src, slen, tgt, tlen);
+       case EDIT_DISTANCE_DL:
+               return edit_distance_dl(src, slen, tgt, tlen);
+       }
+
+       return (ed_dist)-1;
+}