PD tsearch as reqd by xpg; by esr

1 files changed, 41 insertions, 0 deletions

diff --git a/lib/libc/stdlib/tfind.c b/lib/libc/stdlib/tfind.c
new file mode 100644
index 00000000000..8e77527bf51
--- /dev/null
+++ b/lib/libc/stdlib/tfind.c
@@ -0,0 +1,41 @@
+/*
+ * 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.
+ */
+/*LINTLIBRARY*/
+#include <search.h>
+
+typedef struct node_t
+{
+    char	  *key;
+    struct node_t *llink, *rlink;
+} node;
+
+/* find a node, or return 0 */
+void *
+tfind(vkey, vrootp, compar)
+	const void	*vkey;		/* key to be found */
+	void		**vrootp;	/* address of the tree root */
+	int		(*compar) __P((const void *, const void *));
+{
+    char *key = (char *)vkey;
+    node **rootp = (node **)vrootp;
+
+    if (rootp == (struct node_t **)0)
+	return ((struct node_t *)0);
+    while (*rootp != (struct node_t *)0) {	/* T1: */
+	int r;
+	if ((r = (*compar)(key, (*rootp)->key)) == 0)	/* T2: */
+	    return (*rootp);		/* key found */
+	rootp = (r < 0) ?
+	    &(*rootp)->llink :		/* T3: follow left branch */
+	    &(*rootp)->rlink;		/* T4: follow right branch */
+    }
+    return (node *)0;
+}