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// DSi icon_fixcrc
// written by remark
// thanks to loopy_, bLASTY, segher
// Copyright 2007,2008  Segher Boessenkool  <>
// Licensed under the terms of the GNU GPL, version 2

#include <stdio.h>
typedef unsigned long u32;
typedef unsigned short u16;
typedef unsigned char u8;

u16 be16(const u8 *p)
  return (p[0] << 8) | p[1];
u32 be32(const u8 *p)
  return (p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3];

#define BNR_VER 0x0301
#define FLAG_FLIPV 0x80
#define FLAG_FLIPH 0x40
typedef struct {
  u16 version;
  u16 crcs[4];
  u8 padding[0x16]; 
  u8 bitmap[0x200];
  u16 palette[0x10];
  u8 title_jap[0x100];
  u8 title_eng[0x100];
  u8 title_fr[0x100];
  u8 title_ger[0x100];
  u8 title_ita[0x100];
  u8 title_spa[0x100];
  u8 title_unk[0x100]; 
  u8 title_unk2[0x100];
  u8 padding2[0x800];
  u8 bitmaps[8][0x200];
  u16 palettes[8][0x10];
  u16 sequence[0x40];
} bannerstruct;
int flength(FILE *f)
  int pos,end;
  pos = ftell (f);
  fseek (f, 0, SEEK_END);
  end = ftell (f);
  fseek (f, pos, SEEK_SET);
  return end;
// crc16; poly 0xA001
u16 crc_table[256] = {
  0x0000, 0xc0c1, 0xc181, 0x0140, 0xc301, 0x03c0, 0x0280, 0xc241, 0xc601, 0x06c0,
  0x0780, 0xc741, 0x0500, 0xc5c1, 0xc481, 0x0440, 0xcc01, 0x0cc0, 0x0d80, 0xcd41,
  0x0f00, 0xcfc1, 0xce81, 0x0e40, 0x0a00, 0xcac1, 0xcb81, 0x0b40, 0xc901, 0x09c0,
  0x0880, 0xc841, 0xd801, 0x18c0, 0x1980, 0xd941, 0x1b00, 0xdbc1, 0xda81, 0x1a40,
  0x1e00, 0xdec1, 0xdf81, 0x1f40, 0xdd01, 0x1dc0, 0x1c80, 0xdc41, 0x1400, 0xd4c1,
  0xd581, 0x1540, 0xd701, 0x17c0, 0x1680, 0xd641, 0xd201, 0x12c0, 0x1380, 0xd341,
  0x1100, 0xd1c1, 0xd081, 0x1040, 0xf001, 0x30c0, 0x3180, 0xf141, 0x3300, 0xf3c1,
  0xf281, 0x3240, 0x3600, 0xf6c1, 0xf781, 0x3740, 0xf501, 0x35c0, 0x3480, 0xf441,
  0x3c00, 0xfcc1, 0xfd81, 0x3d40, 0xff01, 0x3fc0, 0x3e80, 0xfe41, 0xfa01, 0x3ac0,
  0x3b80, 0xfb41, 0x3900, 0xf9c1, 0xf881, 0x3840, 0x2800, 0xe8c1, 0xe981, 0x2940,
  0xeb01, 0x2bc0, 0x2a80, 0xea41, 0xee01, 0x2ec0, 0x2f80, 0xef41, 0x2d00, 0xedc1,
  0xec81, 0x2c40, 0xe401, 0x24c0, 0x2580, 0xe541, 0x2700, 0xe7c1, 0xe681, 0x2640,
  0x2200, 0xe2c1, 0xe381, 0x2340, 0xe101, 0x21c0, 0x2080, 0xe041, 0xa001, 0x60c0,
  0x6180, 0xa141, 0x6300, 0xa3c1, 0xa281, 0x6240, 0x6600, 0xa6c1, 0xa781, 0x6740,
  0xa501, 0x65c0, 0x6480, 0xa441, 0x6c00, 0xacc1, 0xad81, 0x6d40, 0xaf01, 0x6fc0,
  0x6e80, 0xae41, 0xaa01, 0x6ac0, 0x6b80, 0xab41, 0x6900, 0xa9c1, 0xa881, 0x6840,
  0x7800, 0xb8c1, 0xb981, 0x7940, 0xbb01, 0x7bc0, 0x7a80, 0xba41, 0xbe01, 0x7ec0,
  0x7f80, 0xbf41, 0x7d00, 0xbdc1, 0xbc81, 0x7c40, 0xb401, 0x74c0, 0x7580, 0xb541,
  0x7700, 0xb7c1, 0xb681, 0x7640, 0x7200, 0xb2c1, 0xb381, 0x7340, 0xb101, 0x71c0,
  0x7080, 0xb041, 0x5000, 0x90c1, 0x9181, 0x5140, 0x9301, 0x53c0, 0x5280, 0x9241,
  0x9601, 0x56c0, 0x5780, 0x9741, 0x5500, 0x95c1, 0x9481, 0x5440, 0x9c01, 0x5cc0,
  0x5d80, 0x9d41, 0x5f00, 0x9fc1, 0x9e81, 0x5e40, 0x5a00, 0x9ac1, 0x9b81, 0x5b40,
  0x9901, 0x59c0, 0x5880, 0x9841, 0x8801, 0x48c0, 0x4980, 0x8941, 0x4b00, 0x8bc1,
  0x8a81, 0x4a40, 0x4e00, 0x8ec1, 0x8f81, 0x4f40, 0x8d01, 0x4dc0, 0x4c80, 0x8c41,
  0x4400, 0x84c1, 0x8581, 0x4540, 0x8701, 0x47c0, 0x4680, 0x8641, 0x8201, 0x42c0,
  0x4380, 0x8341, 0x4100, 0x81c1, 0x8081, 0x4040
u16 crc16(char* buf, int len)
  u16 c = 0xFFFF;
  int n;
  for (n = 0; n < len; n++) {
    c = crc_table[(c^buf[n]) & 0xFF] ^ (c>>8);
  return c;
int main(int argc, char* argv[])
  if(argc != 2)
    printf("usage: %s <icon.bin>\n", argv[0]);
  FILE* fp = fopen(argv[1],"rb");
  if(fp == NULL)
    printf("input file not found\n");
  int f_len = flength(fp);
  char* f_buf = malloc(f_len);
  if(f_buf == NULL)
    fprintf(stderr, "not enough memory\n");
  if(fread(f_buf, f_len, 1, fp) != 1)
    fprintf(stderr, "file read failure\n");
  bannerstruct* bnr = (bannerstruct*) f_buf;
  // check magic
  if(be16((u8*)&bnr->version) != BNR_VER)
    fprintf(stderr, "invalid banner icon (magic mismatch)\n");
  // 1st
  u16 calc_crc = crc16(f_buf+0x20,0x820);
  if(calc_crc != bnr->crcs[0])
    printf("crc[0] updated: %x != %x\n", calc_crc, bnr->crcs[0]);
    bnr->crcs[0] = calc_crc;
  // 2nd
  calc_crc = crc16(f_buf+0x20,0x920);
  if(calc_crc != bnr->crcs[1])
    printf("crc[1] updated: %x != %x\n", calc_crc, bnr->crcs[1]);
    bnr->crcs[1] = calc_crc;
  // 3rd
  calc_crc = crc16(f_buf+0x20,0xA20);
  if(calc_crc != bnr->crcs[2])
    printf("crc[2] updated: %x != %x\n", calc_crc, bnr->crcs[2]);
    bnr->crcs[2] = calc_crc;
  // 4th
  calc_crc = crc16(f_buf+0x1240,0x1180);
  if(calc_crc != bnr->crcs[3])
    printf("crc[3] updated: %x != %x\n", calc_crc, bnr->crcs[3]);
    bnr->crcs[3] = calc_crc;
  fp = freopen(argv[1], "wb+", fp);
  if(fwrite(f_buf, f_len, 1, fp) != 1)
    printf("write to output file failed\n");
  return 0;