From 3a3118953bcc38ae84cd7fb5ba5b1a20995b9f5d Mon Sep 17 00:00:00 2001
From: Joerg Wunsch <j@uriah.heep.sax.de>
Date: Tue, 10 May 2005 19:43:44 +0000
Subject: [PATCH] I forgot to add these files in the previous commit.  They are
 basically obtained from Atmel's appnote AVR067.

git-svn-id: svn://svn.savannah.nongnu.org/avrdude/trunk/avrdude@452 81a1dc3b-b13d-400b-aceb-764788c761c2
---
 crc16.c | 83 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 crc16.h | 25 +++++++++++++++++
 2 files changed, 108 insertions(+)
 create mode 100644 crc16.c
 create mode 100644 crc16.h

diff --git a/crc16.c b/crc16.c
new file mode 100644
index 00000000..ed0e7e0f
--- /dev/null
+++ b/crc16.c
@@ -0,0 +1,83 @@
+/*
+ * Derived from CRC algorithm for JTAG ICE mkII, published in Atmel
+ * Appnote AVR067.  Converted from C++ to C.
+ */
+#include "crc16.h"
+
+/* CRC16 Definitions */
+const unsigned short crc_table[256] = {
+  0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,
+  0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,
+  0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,
+  0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,
+  0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd,
+  0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,
+  0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c,
+  0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,
+  0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
+  0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,
+  0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a,
+  0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,
+  0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9,
+  0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,
+  0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,
+  0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,
+  0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7,
+  0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
+  0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036,
+  0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,
+  0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,
+  0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,
+  0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134,
+  0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,
+  0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3,
+  0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,
+  0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,
+  0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a,
+  0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1,
+  0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,
+  0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330,
+  0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78
+};
+
+/* CRC calculation macros */
+#define CRC_INIT 0xFFFF
+#define CRC(crcval,newchar) crcval = (crcval >> 8) ^ \
+	crc_table[(crcval ^ newchar) & 0x00ff]
+
+unsigned short
+crcsum(const unsigned char* message, unsigned long length,
+       unsigned short crc)
+{
+  unsigned long i;
+
+  for(i = 0; i < length; i++)
+    {
+      CRC(crc, message[i]);
+    }
+  return crc;
+}
+
+int
+crcverify(const unsigned char* message, unsigned long length)
+{
+  /*
+   * Returns true if the last two bytes in a message is the crc of the
+   * preceding bytes.
+   */
+  unsigned short expected;
+
+  expected = crcsum(message, length - 2, CRC_INIT);
+  return (expected & 0xff) == message[length - 2] &&
+    ((expected >> 8) & 0xff) == message[length - 1];
+}
+
+void
+crcappend(unsigned char* message, unsigned long length)
+{
+  unsigned long crc;
+
+  crc = crcsum(message, length, CRC_INIT);
+  message[length] = (unsigned char)(crc & 0xff);
+  message[length+1] = (unsigned char)((crc >> 8) & 0xff);
+}
diff --git a/crc16.h b/crc16.h
new file mode 100644
index 00000000..54647fd0
--- /dev/null
+++ b/crc16.h
@@ -0,0 +1,25 @@
+#ifndef CRC16_H
+#define CRC16_H
+/*
+ * Derived from CRC algorithm for JTAG ICE mkII, published in Atmel
+ * Appnote AVR067.  Converted from C++ to C.
+ */
+
+extern unsigned short crcsum(const unsigned char* message,
+			     unsigned long length,
+			     unsigned short crc);
+/*
+ * Verify that the last two bytes is a (LSB first) valid CRC of the
+ * message.
+ */
+extern int crcverify(const unsigned char* message,
+		     unsigned long length);
+/*
+ * Append a two byte CRC (LSB first) to message.  length is size of
+ * message excluding crc.  Space for the CRC bytes must be allocated
+ * in advance!
+ */
+extern void crcappend(unsigned char* message,
+		      unsigned long length);
+
+#endif