1 files changed, 143 insertions, 0 deletions

diff --git a/src/lib/tsearch.c b/src/lib/tsearch.c
new file mode 100644
index 00000000..fe5fcd5b
--- /dev/null
+++ b/src/lib/tsearch.c
@@ -0,0 +1,143 @@
+/*
+ * Tree search generalized from Knuth (6.2.2) Algorithm T just like
+ * the AT&T man page says.
+ *
+ * The node_t structure is for internal use only, lint doesn't grok it.
+ *
+ * Written by reading the System V Interface Definition, not the code.
+ *
+ * Totally public domain.
+ */
+
+#include "tsearch.h"
+#include <stdlib.h>
+
+
+typedef struct node
+{
+  const void   *key;
+  struct node  *llink;
+  struct node  *rlink;
+} node_t;
+
+
+/*      $NetBSD: tsearch.c,v 1.5 2005/11/29 03:12:00 christos Exp $     */
+/* find or insert datum into search tree */
+void *
+tsearch (const void *vkey,              /* key to be located */
+         void **vrootp,                 /* address of tree root */
+         int (*compar)(const void *, const void *))
+{
+  node_t *q;
+  node_t **rootp = (node_t **)vrootp;
+
+  if (NULL == rootp)
+    return NULL;
+
+  while (*rootp != NULL)
+    {   /* Knuth's T1: */
+      int r;
+
+      if ((r = (*compar)(vkey, (*rootp)->key)) == 0)    /* T2: */
+        return *rootp;          /* we found it! */
+
+      rootp = (r < 0) ?
+        &(*rootp)->llink :              /* T3: follow left branch */
+        &(*rootp)->rlink;               /* T4: follow right branch */
+    }
+
+  q = malloc (sizeof(node_t));          /* T5: key not found */
+  if (q)
+    {                           /* make new node */
+      *rootp = q;                       /* link new node to old */
+      q->key = vkey;            /* initialize new node */
+      q->llink = q->rlink = NULL;
+    }
+  return q;
+}
+
+
+/*      $NetBSD: tfind.c,v 1.5 2005/03/23 08:16:53 kleink Exp $ */
+/* find a node, or return NULL */
+void *
+tfind (const void *vkey,         /* key to be found */
+       void * const *vrootp,     /* address of the tree root */
+       int (*compar)(const void *, const void *))
+{
+  node_t * const *rootp = (node_t * const*)vrootp;
+
+  if (NULL == rootp)
+    return NULL;
+
+  while (*rootp != NULL)
+    {           /* T1: */
+      int r;
+
+      if ((r = (*compar)(vkey, (*rootp)->key)) == 0)    /* T2: */
+        return *rootp;          /* key found */
+      rootp = (r < 0) ?
+        &(*rootp)->llink :              /* T3: follow left branch */
+        &(*rootp)->rlink;               /* T4: follow right branch */
+    }
+  return NULL;
+}
+
+
+/*      $NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp $        */
+/*
+ * delete node with given key
+ *
+ * vkey:   key to be deleted
+ * vrootp: address of the root of the tree
+ * compar: function to carry out node comparisons
+ */
+void *
+tdelete (const void * __restrict vkey,
+         void ** __restrict vrootp,
+         int (*compar)(const void *, const void *))
+{
+  node_t **rootp = (node_t **)vrootp;
+  node_t *p;
+  node_t *q;
+  node_t *r;
+  int cmp;
+
+  if (rootp == NULL || (p = *rootp) == NULL)
+    return NULL;
+
+  while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0)
+    {
+      p = *rootp;
+      rootp = (cmp < 0) ?
+        &(*rootp)->llink :              /* follow llink branch */
+        &(*rootp)->rlink;               /* follow rlink branch */
+      if (*rootp == NULL)
+        return NULL;            /* key not found */
+    }
+  r = (*rootp)->rlink;                  /* D1: */
+  if ((q = (*rootp)->llink) == NULL)    /* Left NULL? */
+    {
+      q = r;
+    }
+  else if (r != NULL)
+    {                   /* Right link is NULL? */
+      if (r->llink == NULL)
+        {               /* D2: Find successor */
+          r->llink = q;
+          q = r;
+        }
+      else
+        {                       /* D3: Find NULL link */
+          for (q = r->llink; q->llink != NULL; q = r->llink)
+            r = q;
+          r->llink = q->rlink;
+          q->llink = (*rootp)->llink;
+          q->rlink = (*rootp)->rlink;
+        }
+    }
+  free(*rootp);                         /* D4: Free node */
+  *rootp = q;                           /* link parent to new node */
+  return p;
+}
+
+/* end of tsearch.c */