diff --git a/cpack.c b/cpack.c
new file mode 100644
index 0000000..14c0a9e
--- /dev/null
+++ b/cpack.c
@@ -0,0 +1,144 @@
+/*-
+ * Copyright (c) 2003, 2004 David Young.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of David Young may not be used to endorse or promote
+ *    products derived from this software without specific prior
+ *    written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY DAVID YOUNG ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+ * PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL DAVID
+ * YOUNG BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
+ * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
+ * OF SUCH DAMAGE.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <stdlib.h>
+#include <string.h>
+#include <tcpdump-stdinc.h>
+
+#include "cpack.h"
+#include "extract.h"
+
+static u_int8_t *
+cpack_next_boundary(u_int8_t *buf, u_int8_t *p, size_t alignment)
+{
+	size_t misalignment = (size_t)(p - buf) % alignment;
+
+	if (misalignment == 0)
+		return p;
+
+	return p + (alignment - misalignment);
+}
+
+/* Advance to the next wordsize boundary. Return NULL if fewer than
+ * wordsize bytes remain in the buffer after the boundary.  Otherwise,
+ * return a pointer to the boundary.
+ */
+static u_int8_t *
+cpack_align_and_reserve(struct cpack_state *cs, size_t wordsize)
+{
+	u_int8_t *next;
+
+	/* Ensure alignment. */
+	next = cpack_next_boundary(cs->c_buf, cs->c_next, wordsize);
+
+	/* Too little space for wordsize bytes? */
+	if (next - cs->c_buf + wordsize > cs->c_len)
+		return NULL;
+
+	return next;
+}
+
+int
+cpack_init(struct cpack_state *cs, u_int8_t *buf, size_t buflen)
+{
+	memset(cs, 0, sizeof(*cs));
+
+	cs->c_buf = buf;
+	cs->c_len = buflen;
+	cs->c_next = cs->c_buf;
+
+	return 0;
+}
+
+/* Unpack a 64-bit unsigned integer. */
+int
+cpack_uint64(struct cpack_state *cs, u_int64_t *u)
+{
+	u_int8_t *next;
+
+	if ((next = cpack_align_and_reserve(cs, sizeof(*u))) == NULL)
+		return -1;
+
+	*u = EXTRACT_LE_64BITS(next);
+
+	/* Move pointer past the u_int64_t. */
+	cs->c_next = next + sizeof(*u);
+	return 0;
+}
+
+/* Unpack a 32-bit unsigned integer. */
+int
+cpack_uint32(struct cpack_state *cs, u_int32_t *u)
+{
+	u_int8_t *next;
+
+	if ((next = cpack_align_and_reserve(cs, sizeof(*u))) == NULL)
+		return -1;
+
+	*u = EXTRACT_LE_32BITS(next);
+
+	/* Move pointer past the u_int32_t. */
+	cs->c_next = next + sizeof(*u);
+	return 0;
+}
+
+/* Unpack a 16-bit unsigned integer. */
+int
+cpack_uint16(struct cpack_state *cs, u_int16_t *u)
+{
+	u_int8_t *next;
+
+	if ((next = cpack_align_and_reserve(cs, sizeof(*u))) == NULL)
+		return -1;
+
+	*u = EXTRACT_LE_16BITS(next);
+
+	/* Move pointer past the u_int16_t. */
+	cs->c_next = next + sizeof(*u);
+	return 0;
+}
+
+/* Unpack an 8-bit unsigned integer. */
+int
+cpack_uint8(struct cpack_state *cs, u_int8_t *u)
+{
+	/* No space left? */
+	if ((size_t)(cs->c_next - cs->c_buf) >= cs->c_len)
+		return -1;
+
+	*u = *cs->c_next;
+
+	/* Move pointer past the u_int8_t. */
+	cs->c_next++;
+	return 0;
+}