X-Git-Url: https://git.distorted.org.uk/~mdw/anag/blobdiff_plain/650bb9da7cf5b677960c03e0a6a5616d48340845..904ac13a4c7d86c18d031ad3f113659440ab86b8:/anagram.c?ds=sidebyside

diff --git a/anagram.c b/anagram.c
index d4eb5e7..a1ed21f 100644
--- a/anagram.c
+++ b/anagram.c
@@ -30,10 +30,12 @@
 
 /*----- Data structures ---------------------------------------------------*/
 
+typedef unsigned countmap[UCHAR_MAX + 1];
+
 typedef struct node_gram {
   node n;
   size_t sz;
-  unsigned f[UCHAR_MAX + 1];
+  countmap count;
 } node_gram;
 
 /*----- Main code ---------------------------------------------------------*/
@@ -43,45 +45,40 @@ typedef struct node_gram {
  * Arguments:	@node_gram *n@ = pointer to node to fill in
  *		@const char *p@ = pointer to string to compile from
  *
- * Returns:	The length of the string.
+ * Returns:	---
  *
  * Use:		Fills in an anagram node with letter frequencies.
  */
 
-static size_t compile(node_gram *n, const char *p)
+static void compile(const char *p, countmap count)
 {
-  size_t len = 0;
-  unsigned i;
-  memset(n->f, 0, sizeof(n->f));
-  while (*p) {
-    i = (unsigned char)*p++;
-    n->f[i]++;
-    len++;
-  }
-  return (len);
+  memset(count, 0, sizeof(countmap));
+  while (*p) count[(unsigned char)*p++]++;
 }
 
 /* --- Node matcher --- */
 
 static int n_gram(node *nn, const char *p, size_t sz)
 {
+  /* A string X is a subgram of Y unless, for some character CH, X has more
+   * characters of value CH than Y.
+   *
+   * Special feature: count `.' in the pattern as meaning `don't care'.
+   */
+
   node_gram *n = (node_gram *)nn;
-  unsigned f[UCHAR_MAX];
+  countmap count;
   const char *q;
   unsigned i;
 
-  if (n->sz && sz != n->sz)
-    return (0);
-  memcpy(f, n->f, sizeof(f));
+  if (n->sz && sz != n->sz) return (0);
+  memcpy(count, n->count, sizeof(count));
   q = p + sz;
   while (p < q) {
     i = (unsigned char)*p++;
-    if (f[i])
-      f[i]--;
-    else if (f['.'])
-      f['.']--;
-    else
-      return (0);
+    if (count[i]) count[i]--;
+    else if (count['.']) count['.']--;
+    else return (0);
   }
   return (1);
 }
@@ -92,7 +89,8 @@ node *anagram(const char *const *av)
 {
   node_gram *n = xmalloc(sizeof(*n));
   n->n.func = n_gram;
-  n->sz = compile(n, av[0]);
+  compile(av[0], n->count);
+  n->sz = strlen(av[0]);
   return (&n->n);
 }
 
@@ -100,8 +98,8 @@ node *subgram(const char *const *av)
 {
   node_gram *n = xmalloc(sizeof(*n));
   n->n.func = n_gram;
+  compile(av[0], n->count);
   n->sz = 0;
-  compile(n, av[0]);
   return (&n->n);
 }