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diff --git a/reference/C/CONTRIB/SNIP/memrev.c b/reference/C/CONTRIB/SNIP/memrev.c
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+/*
+**  Public domain demo by Ray Gardner, 7 dec 88
+**
+**  Here's an old programming trick that (I bet) will be new to at least a
+**  few of you out there, even some "old hands".  I don't remember where I
+**  saw this; it might have been Jon Bentley's "Programming Pearls" column in
+**  Communications of the ACM.
+**
+**  Have you ever wanted to exchange two adjacent areas of storage which
+**  might be of two different lengths?  There are some tricky and complicated
+**  "efficient" methods to do this without using a lot of extra temporary
+**  storage.  But there is also an old and simple way: Assume that the buffer
+**  looks like this:
+**
+**     |...... head .......|.................. tail .................|
+**
+**  You reverse the head, reverse the tail, then reverse the entire buffer.
+**  That's all there is to it.  It will leave you with:
+**
+**     |.................. tail .................|...... head .......|
+**
+**  Here's code:
+*/
+
+#include <stdlib.h>
+
+/*
+**  reverse "count" bytes starting at "buf"
+*/
+
+void memrev(char  *buf, size_t count)
+{
+      char *r;
+
+      for (r = buf + count - 1; buf < r; buf++, r--)
+      {
+            *buf ^= *r;
+            *r   ^= *buf;
+            *buf ^= *r;
+      }
+}
+
+/*
+**  swap "head" bytes with "tail" bytes at "buf"
+*/
+
+void aswap(char  *buf, size_t head, size_t tail)
+{
+      memrev(buf, head);
+      memrev(buf + head, tail);
+      memrev(buf, head + tail);
+}