First checkin

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@55 a1c6a512-1295-4272-9138-f99709370657

tools/descramble.c

@@ -0,0 +1,83 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2002 by Björn Stenberg
+ *
+ * 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 <stdlib.h>
+
+int main (int argc, char** argv)
+{
+    unsigned long length,i,slen;
+    unsigned char *inbuf,*outbuf;
+    FILE* file;
+
+    if (argc < 3) {
+       printf("usage: %s <input file> <output file>\n",argv[0]);
+       return -1;
+    }
+    
+    /* open file and check size */
+    file = fopen(argv[1],"rb");
+    if (!file) {
+       perror(argv[1]);
+       return -1;
+    }
+    fseek(file,0,SEEK_END);
+    length = ftell(file) - 6; /* skip 6-byte header */
+    fseek(file,6,SEEK_SET); 
+    inbuf = malloc(length);
+    outbuf = malloc(length);
+    if ( !inbuf || !outbuf ) {
+       printf("out of memory!\n");
+       return -1;
+    }
+
+    /* read file */
+    i=fread(inbuf,1,length,file);
+    if ( !i ) {
+       perror(argv[1]);
+       return -1;
+    }
+    fclose(file);
+
+    /* descramble */
+    slen = length/4;
+    for (i = 0; i < length; i++) {
+      unsigned long addr = ((i % slen) << 2) + i/slen;
+      unsigned char data = inbuf[i];
+      data = ~((data >> 1) | ((data << 7) & 0x80)); /* poor man's ROR */
+      outbuf[addr] = data;
+    }
+    
+    /* write file */
+    file = fopen(argv[2],"wb");
+    if ( !file ) {
+       perror(argv[2]);
+       return -1;
+    }
+    if ( !fwrite(outbuf,length,1,file) ) {
+       perror(argv[2]);
+       return -1;
+    }
+    fclose(file);
+    
+    free(inbuf);
+    free(outbuf);
+    
+    return 0;	
+}