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authorDave Chapman <dave@dchapman.com>2007-09-30 12:49:43 +0000
committerDave Chapman <dave@dchapman.com>2007-09-30 12:49:43 +0000
commit41541c5c31c5cd4f1a6dbbd7354046cfd5cfa13f (patch)
treea57742b5bb57f6b9d5cd5700601fcf9e22ebebf7 /tools/telechips.c
parent0f5d9f9125e53ae62175469e78151ca4cb0be79a (diff)
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Add support for the generic Telechips firmware format checksums - use -tcc=sum if the header just contains a single checksum, or -tcc=crc if the header contains two 32-bit CRCs. Credit goes to Hein-Pieter van Braam for his work on identifying the (reverse) CRC32 algorithm used when calculating the two CRCs
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@14917 a1c6a512-1295-4272-9138-f99709370657
Diffstat (limited to 'tools/telechips.c')
-rw-r--r--tools/telechips.c156
1 files changed, 156 insertions, 0 deletions
diff --git a/tools/telechips.c b/tools/telechips.c
new file mode 100644
index 0000000000..5b6f3c23b3
--- /dev/null
+++ b/tools/telechips.c
@@ -0,0 +1,156 @@
+/***************************************************************************
+ * __________ __ ___.
+ * Open \______ \ ____ ____ | | _\_ |__ _______ ___
+ * Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
+ * Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
+ * Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
+ * \/ \/ \/ \/ \/
+ * $Id$
+ *
+ * Telechips firmware checksum support for scramble
+ *
+ * Copyright (C) 2007 Dave Chapman
+ *
+ * Thanks to Hein-Pieter van Braam for his work in identifying the
+ * CRC algorithm used.
+ *
+ * All files in this archive are subject to the GNU General Public License.
+ * See the file COPYING in the source tree root for full license agreement.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+static uint32_t crctable[256];
+
+/* Simple implementation of a function to reverse the bottom n bits in x */
+static uint32_t bitreverse(uint32_t x,int n)
+{
+ int i;
+ uint32_t mask = 1<<(n-1);
+ uint32_t res = 0;
+
+ for (i=0; i<n; i++)
+ {
+ if (x & 1)
+ res |= mask;
+
+ x >>= 1;
+ mask >>= 1;
+ }
+ return res;
+}
+
+/* Generate a lookup table for a reverse CRC32 */
+static void gentable(uint32_t poly)
+{
+ int i;
+ uint32_t r;
+ uint32_t index;
+
+ for (index = 0; index < 256; index++)
+ {
+ r = bitreverse(index,8) << 24;
+ for (i=0; i<8; i++)
+ {
+ if (r & (1 << 31))
+ r = (r << 1) ^ poly;
+ else
+ r<<=1;
+ }
+ crctable[index] = bitreverse(r,32);
+ }
+}
+
+/* Perform a reverse CRC32 */
+static uint32_t calc_crc(unsigned char *message, int size)
+{
+ uint32_t crc = 0;
+ int i;
+
+ for (i=0; i < size; i++){
+ if ((i < 0x10) || (i >= 0x18)) {
+ crc = crctable[((crc ^ (message[i])) & 0xff)] ^ (crc >> 8);
+ }
+ }
+
+ return crc;
+}
+
+/* Endian-safe functions to read/write a 32-bit little-endian integer */
+
+static uint32_t get_uint32le(unsigned char* p)
+{
+ return p[0] | (p[1] << 8) | (p[2] << 16) | (p[3] << 24);
+}
+
+static void put_uint32le(unsigned char* p, uint32_t x)
+{
+ p[0] = x & 0xff;
+ p[1] = (x >> 8) & 0xff;
+ p[2] = (x >> 16) & 0xff;
+ p[3] = (x >> 24) & 0xff;
+}
+
+/* A simple checksum - seems to be used by the TCC76x firmwares */
+void telechips_encode_sum(unsigned char* buf, int length)
+{
+ uint32_t sum;
+ int i;
+
+ /* Set checksum field to 0 */
+ put_uint32le(buf + 0x10, 0);
+
+ /* Perform a simple sum, treating the file as a series of 32-bit
+ little-endian integers */
+ sum = 0;
+ for (i=0; i < length; i+=4) {
+ sum += get_uint32le(buf + i);
+ }
+ /* Negate the sum - this means that the sum of the whole file
+ (including this value) will be equal to zero */
+ sum = -sum;
+
+ /* Set the checksum field */
+ put_uint32le(buf + 0x10, sum);
+}
+
+
+/* Two reverse CRC32 checksums - seems to be used by the TCC77x firmwares */
+void telechips_encode_crc(unsigned char* buf, int length)
+{
+ uint32_t crc1,crc2;
+
+ /* Generate the CRC table */
+ gentable(0x8001801BL);
+
+ /* Clear the existing CRC values */
+ put_uint32le(buf+0x10, 0);
+ put_uint32le(buf+0x18, 0);
+
+ /* Write the length */
+ put_uint32le(buf+0x1c, length);
+
+ /* Calculate the first CRC - over the entire file */
+ crc1 = calc_crc(buf, length);
+
+ /* What happens next depends on the filesize */
+ if (length >= 128*1024)
+ {
+ put_uint32le(buf+0x18, crc1);
+
+ crc2 = calc_crc(buf, 128*1024);
+ put_uint32le(buf+0x10, crc2);
+ } else {
+ put_uint32le(buf+0x10, crc1);
+ }
+}