/* Original author: mlb2gm5x @ misticriver forums */
/* Modified: Jon Lund Steffensen, 2008 */

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <unistd.h>

#define USAGE \
	"Usage: %s -e|-d [-h] [-r] INPUT OUTPUT\n"
#define HELP \
	USAGE \
	" Encode or decode iriver files.\n" \
	"  -e\tEncode INPUT to OUTPUT\n" \
	"  -d\tDecode INPUT to OUTPUT\n" \
	"  -h\tDisplay this help message\n" \
	"  -r\tRaw data mode; Don't update header\n" \
	"  -s\tSkip checksum check when decoding (DANGEROUS!)\n"

static const uint8_t table1[256] = {
	0x67, 0xB2, 0x9F, 0x5A, 0x9E, 0xAD, 0x46, 0x4B,
	0x8F, 0x23, 0x16, 0x7B, 0x4B, 0x5B, 0x5C, 0x44,
	0xC1, 0x79, 0xCA, 0x35, 0x2D, 0xAA, 0xF4, 0x7D,
	0x53, 0xED, 0x60, 0x03, 0x7D, 0x36, 0x98, 0xFB,
	0x02, 0xBB, 0x5A, 0x6D, 0xD4, 0x09, 0x9C, 0x1D,
	0xB2, 0x61, 0xA7, 0xC9, 0x62, 0x46, 0xB3, 0x4E,
	0xEC, 0x26, 0x5C, 0xB0, 0xE7, 0x44, 0x27, 0xBD,
	0x39, 0x8F, 0xD1, 0x0E, 0xD2, 0xDA, 0x6C, 0xDC,
	0x76, 0x90, 0x33, 0x0E, 0xBD, 0x60, 0x5D, 0x34,
	0x19, 0x56, 0x05, 0xD7, 0x5E, 0x14, 0xA0, 0x04,
	0x1F, 0x11, 0x97, 0x42, 0x7F, 0xF1, 0x76, 0xA8,
	0x60, 0xFD, 0xA0, 0xD0, 0x1B, 0x41, 0xCA, 0xF5,
	0x30, 0x52, 0xD1, 0x9B, 0xD7, 0x14, 0xDB, 0xF5,
	0xC2, 0xD0, 0xD9, 0x2C, 0x13, 0x98, 0x70, 0x3F,
	0x16, 0x73, 0xE9, 0x08, 0x2C, 0xDD, 0xFA, 0x05,
	0x96, 0xD6, 0x7E, 0x81, 0xA1, 0xD3, 0xF1, 0x09,
	0x2C, 0x6D, 0x97, 0x0A, 0x0C, 0x6D, 0x6A, 0x99,
	0xC0, 0x98, 0x8F, 0x5A, 0x22, 0xB0, 0xE1, 0xE3,
	0xDF, 0xDF, 0xCF, 0x18, 0x71, 0x26, 0xFD, 0x70,
	0xC6, 0x0D, 0x32, 0x6C, 0xBF, 0x48, 0x9E, 0xB5,
	0x83, 0xEA, 0x33, 0x77, 0x9A, 0x25, 0xFC, 0x38,
	0x58, 0x6D, 0xD4, 0xD3, 0x86, 0x7E, 0xBC, 0x70,
	0x25, 0x95, 0x71, 0x19, 0xB8, 0xED, 0x10, 0x5F,
	0x32, 0x45, 0xAF, 0x3D, 0x69, 0xC6, 0x9A, 0x41,
	0x49, 0xB5, 0xEE, 0x9B, 0x58, 0xBA, 0xED, 0x01,
	0xF4, 0xE2, 0xCF, 0x0B, 0xEE, 0xC9, 0xB7, 0xE4,
	0xF0, 0xBA, 0xEF, 0x3B, 0x23, 0x09, 0x61, 0x0E,
	0xF5, 0x02, 0x1E, 0xB5, 0x3A, 0x3C, 0xBC, 0x65,
	0xB1, 0x1D, 0xC6, 0x7C, 0x97, 0xBC, 0x90, 0x9B,
	0x66, 0xE3, 0x32, 0x4B, 0x4B, 0x85, 0x0D, 0x9B,
	0xED, 0x9D, 0x8A, 0x5C, 0xDC, 0x02, 0x76, 0xED,
	0x61, 0xC2, 0xAB, 0x19, 0x1E, 0x1A, 0x25, 0x28
};

static const uint8_t table2[256] = {
	0x04, 0x08, 0x5E, 0xB9, 0xC0, 0x4D, 0xD8, 0x04,
	0xA5, 0xB6, 0x77, 0x20, 0x28, 0x5D, 0x82, 0x2D,
	0x3B, 0x3F, 0x92, 0x60, 0xCB, 0x3D, 0xAF, 0x49,
	0x50, 0xEB, 0x13, 0x00, 0x04, 0xB5, 0x4B, 0x00,
	0x1B, 0xA2, 0x99, 0x22, 0x68, 0x5C, 0x82, 0xD6,
	0x5A, 0x43, 0xEB, 0x12, 0xC0, 0xD6, 0x37, 0x7A,
	0x17, 0x9D, 0x4B, 0xD0, 0x5B, 0x6B, 0xE8, 0x1D,
	0x02, 0x0C, 0xD8, 0xC5, 0x56, 0x12, 0x24, 0xB1,
	0x20, 0x20, 0xF6, 0x63, 0x1E, 0x85, 0x24, 0x61,
	0x5B, 0x53, 0x7D, 0xC0, 0x95, 0x70, 0x2E, 0x8F,
	0xEC, 0xBB, 0x8F, 0xFF, 0xF9, 0x69, 0x24, 0x79,
	0xD8, 0xB1, 0xB1, 0x29, 0x9A, 0x39, 0x4B, 0xA2,
	0xB9, 0x29, 0x58, 0x9A, 0xBB, 0x04, 0x85, 0xB9,
	0x29, 0x5A, 0xB8, 0x04, 0xE8, 0xE9, 0xD4, 0xA6,
	0xE8, 0xC6, 0x25, 0xB0, 0x94, 0x4B, 0x4B, 0x97,
	0x00, 0x94, 0xBB, 0x69, 0x14, 0x81, 0xAB, 0x5C,
	0x6A, 0x29, 0x97, 0xBA, 0xCA, 0xA5, 0xA0, 0xBB,
	0x42, 0x13, 0x48, 0xDD, 0x11, 0xFB, 0x31, 0x05,
	0x4B, 0xBB, 0xB1, 0x60, 0x69, 0x67, 0x0B, 0x96,
	0xBB, 0x35, 0x5B, 0xC1, 0x3B, 0xB6, 0x58, 0xA9,
	0xE0, 0x9D, 0xB3, 0x8E, 0xAC, 0x34, 0x0D, 0x3D,
	0x73, 0xB7, 0x9A, 0x6D, 0x4D, 0x59, 0x64, 0xEE,
	0x56, 0xB3, 0xDA, 0x22, 0x70, 0xB7, 0x9A, 0xE1,
	0xC1, 0x54, 0x76, 0x9C, 0xB9, 0x76, 0x9C, 0xA1,
	0x2C, 0x5A, 0x45, 0xE0, 0xDA, 0x71, 0xD6, 0x31,
	0xA5, 0x49, 0x02, 0xBD, 0x6D, 0x43, 0x9E, 0x0D,
	0x33, 0x77, 0x29, 0xCF, 0x46, 0x4B, 0x66, 0x78,
	0x7D, 0xFC, 0xAE, 0xFD, 0x5D, 0xFD, 0xAF, 0x4F,
	0xDC, 0xE6, 0x46, 0x7C, 0x49, 0xC6, 0x52, 0x5D,
	0x69, 0xE0, 0xD2, 0xDC, 0x88, 0xFD, 0x58, 0x06,
	0x9E, 0x33, 0xDD, 0x93, 0x0A, 0xC2, 0x9A, 0xE0,
	0xCA, 0x17, 0x70, 0x81, 0xCD, 0x6D, 0x5A, 0x8B
};

static const uint8_t table3[256] = {
	0xF3, 0x2C, 0x61, 0x9E, 0xEA, 0x2D, 0x43, 0x27,
	0x6F, 0xE4, 0x9A, 0xA4, 0x22, 0x46, 0x3F, 0x2E,
	0xCA, 0x19, 0x8D, 0xCC, 0xA9, 0x0C, 0xB7, 0xD5,
	0x99, 0x3D, 0x42, 0xF1, 0xFE, 0x0F, 0x05, 0x5A,
	0xC1, 0x5C, 0xF8, 0x04, 0x2F, 0xB0, 0xC4, 0x21,
	0x13, 0xC7, 0xBB, 0xC3, 0x69, 0xF2, 0x28, 0xB4,
	0x54, 0x39, 0xD2, 0x29, 0x40, 0x63, 0x37, 0x23,
	0x7E, 0xA0, 0xDF, 0xD3, 0xB8, 0x02, 0x7F, 0xED,
	0xBD, 0x44, 0xB9, 0x45, 0x26, 0x64, 0x0E, 0x20,
	0x58, 0x89, 0x12, 0x4C, 0x73, 0x4D, 0x7B, 0x2A,
	0x3A, 0x1F, 0xD6, 0x7A, 0xC0, 0x00, 0x38, 0x72,
	0x52, 0x7D, 0x5D, 0x9C, 0xE2, 0x76, 0xA6, 0x4F,
	0x1C, 0x55, 0x1B, 0x90, 0xDE, 0x9B, 0x24, 0xD9,
	0xDC, 0xB6, 0x1D, 0x85, 0xE9, 0xCD, 0x8A, 0x97,
	0xBA, 0x71, 0xF7, 0x6C, 0x32, 0x06, 0x51, 0x5F,
	0xFB, 0x74, 0x36, 0xFF, 0x7C, 0x4A, 0xEF, 0x3C,
	0x68, 0xE8, 0xAB, 0x56, 0x49, 0xB2, 0x0B, 0x2B,
	0x80, 0x65, 0x30, 0xD0, 0xE7, 0xDD, 0x98, 0x67,
	0x4B, 0x6B, 0x77, 0x83, 0x8B, 0x53, 0x92, 0x60,
	0xA1, 0xA2, 0xBC, 0x91, 0x82, 0x33, 0x87, 0x57,
	0xB5, 0x59, 0xE5, 0x16, 0xEE, 0xD8, 0xF6, 0xFA,
	0x25, 0x6A, 0x31, 0xCE, 0x48, 0x84, 0xA5, 0x5B,
	0x11, 0xAC, 0x3B, 0xF9, 0x14, 0xE0, 0x8C, 0x4E,
	0x8F, 0x95, 0xF5, 0xAF, 0xE3, 0x35, 0x34, 0x9D,
	0x81, 0xAE, 0x50, 0xD1, 0x78, 0x10, 0x88, 0x86,
	0xCF, 0x94, 0x1A, 0xDB, 0xAD, 0x18, 0xC8, 0xBF,
	0x08, 0xA8, 0xFD, 0xBE, 0x96, 0xE6, 0x09, 0x75,
	0x93, 0x9F, 0x01, 0xCB, 0xB3, 0x6D, 0xC5, 0x6E,
	0xD4, 0xA3, 0x62, 0x41, 0x07, 0xA7, 0xAA, 0xEB,
	0xE1, 0x79, 0x1E, 0xF0, 0xC2, 0x0D, 0x0A, 0x5E,
	0xFC, 0xC6, 0xF4, 0xDA, 0xEC, 0x3E, 0x17, 0x15,
	0x03, 0xD7, 0x70, 0x66, 0x47, 0x8E, 0xB1, 0xC9
};

static int
decode_256(const uint8_t *src, uint8_t *dst, int skip_checksums)
{
	unsigned int i, j, k;
	unsigned int tmp1, tmp2;
	uint8_t temp[256];
	
	for (i = 0, tmp1 = 0; i < 255; i++) {
		tmp1 = 0xFFFF & (tmp1 + src[i]);
	}
	
	if ((tmp1 & 0xFF) != src[255]) {
		if (!skip_checksums) return 0;
	}

	for (i = 0; i < 255; i++) {
		temp[i] = table3[src[i]];
	}
	
	for (i = 0, k = 0; i < 5; i++) {
		tmp2 = 50*i;
		tmp1 = 0;
		for (j = 0; j < 50; j++) {
			tmp1 = (temp[k] + tmp1) & 0xFFFF;
			dst[j+tmp2] = temp[k];
			k++;
		}
		if (temp[k] != (tmp1 & 0xFF)) {
			if (!skip_checksums) return 0;
		}
		k++;
	}
	
	for (i = 0; i < 250; i++) {
		tmp1 = ((dst[i]) ^ (table2[i])) << (8-(table1[i] & 7));
		dst[i] = tmp1 | (tmp1 >> 8);
	}
	return 1;
}

static int
decode_file(const char *srcfile, const char *dstfile, int skip_checksums)
{
	int r;
	int size, newsize, err = 0;
	int i, j;
	uint8_t *pMemSource, *pMemDest;
	FILE *pDest, *pSource;

	/* Open source file */
	pSource = fopen(srcfile, "rb");
	if (pSource == NULL) {
		perror("fopen");
		return -1;
	}

	r = fseek(pSource, 0, SEEK_END);
	if (r < 0) {
		perror("fseek");
		return -1;
	}

	size = ftell(pSource);
	if (size < 0) {
		perror("ftell");
		return -1;
	}

	if ((size & 0x7f) != 0) {
		fprintf(stderr, "ERROR: size & 0x7f != 0\n");
		return -1;
	}

	newsize = (125*size)>>7;

	r = fseek(pSource, 0, SEEK_SET);
	if (r < 0) {
		perror("fseek");
		return -1;
	}

	pMemSource = (uint8_t *)malloc(size);
	if (pMemSource == NULL) {
		fprintf(stderr, "ERROR: malloc(%u) failed.\n", size);
		return -1;
	}

	/* Read source file to memory */
	r = fread(pMemSource, sizeof(uint8_t), size, pSource);
	if (r < size) {
		if (ferror(pSource)) perror("fread");
		else fprintf(stderr, "ERROR: EOF reached.\n");
		return -1;
	}
		
	fclose(pSource);

	pMemDest = (uint8_t *)malloc(newsize);
	if (pMemDest == NULL) {
		fprintf(stderr, "ERROR: malloc(%u) failed.\n", newsize);
		return -1;
	}

	/* Decode */
	for (i = 0, j = 0; i < size; i += 256, j += 250) {
		if (decode_256(pMemSource+i, pMemDest+j, skip_checksums) == 0) {
			err = 1;
			break;
		}
	}
	
	if (err) {
		fprintf(stderr, "ERROR: decode failed.\n");
		return -1;
	}

	/* Open destination file */
	pDest = fopen(dstfile, "wb");
	if (pDest == NULL) {
		perror("fopen");
		return -1;
	}

	r = fseek(pDest, 0, SEEK_SET);
	if (r < 0) {
		perror("fseek");
		return -1;
	}

	/* Write to destination file */
	r = fwrite(pMemDest, sizeof(uint8_t), newsize, pDest);
	if (r < newsize) {
		perror("fwrite");
		return -1;
	}
	
	fclose(pDest);

	free(pMemDest);
	free(pMemSource);

	return 0;
}

static void
encode_250(uint8_t *src, uint8_t *dst)
{
	unsigned int i, j, k;
	unsigned int tmp1, tmp2;
	uint8_t temp[256];
	
	for (i = 0; i < 250; i++) {
		int tmp2 = 8 - (table1[i] & 7);
		for (j = 0; j < 256; j++) {
			tmp1 = j << tmp2;
			if (src[i] == (0xFF & (tmp1 | (tmp1 >> 8)))) {
				break;
			}
		}
		src[i] = j ^ (table2[i]);
	}
	
	for (i = 0, k = 0; i < 5; i++) {
		tmp2 = 50*i;
		tmp1 = 0;
		for (j = 0; j < 50; j++) {
			temp[k] = src[j+tmp2];
			tmp1 = (temp[k] + tmp1) & 0xFFFF;
			k++;
		}
		temp[k] = tmp1 & 0xFF;
		k++;
	}
	
	for (i = 0; i < 255; i++) {
		for (j = 0; j < 256; j++) {
			if (temp[i] == table3[j]) {
				dst[i] = j;
				break;
			}
		}
	}
	
	for (i = 0, tmp1 = 0; i < 255; i++) {
		tmp1 = 0xFFFF & (tmp1 + dst[i]);
	}
	
	dst[255] = tmp1 & 0xFF;
}

static void
update_header(uint8_t *pHeader, unsigned int size, unsigned int checksum)
{
	pHeader[0x10] = 0xFF&(size>>24);
	pHeader[0x20] = 0xFF&(size>>16);
	pHeader[0x30] = 0xFF&(size>>8);
	pHeader[0x40] = 0xFF&(size);

	pHeader[0x90] = 0xFF&(checksum>>24);
	pHeader[0xA0] = 0xFF&(checksum>>16);
	pHeader[0xB0] = 0xFF&(checksum>>8);
	pHeader[0xC0] = 0xFF&(checksum);
}

static int
encode_file(const char *srcfile, const char *dstfile, int raw)
{
	int r;
	unsigned int checksum, size, newsize;
	unsigned int i, j;
	uint8_t *pMemSource, *pMemDest;
	FILE *pDest, *pSource;

	/* Open source file */
	pSource = fopen(srcfile, "rb");
	if (pSource == NULL) {
		perror("fopen");
		return -1;
	}

	r = fseek(pSource, 0, SEEK_END);
	if (r < 0) {
		perror("fseek");
		return -1;
	}

	size = ftell(pSource);
	if (size < 0) {
		perror("ftell");
		return -1;
	}

	r = fseek(pSource, 0, SEEK_SET);
	if (r < 0) {
		perror("fseek");
		return -1;
	}

	newsize = size;
	if (size % 250 != 0) {
		newsize = size + 250 - size % 250;
	}

	pMemSource = (uint8_t *)calloc(newsize, 1);
	if (pMemSource == NULL) {
		fprintf(stderr, "ERROR: malloc(%u) failed.\n", newsize);
		return -1;
	}

	/* Read source to memory */
	r = fread(pMemSource, sizeof(uint8_t), size, pSource);
	if (r < size) {
		if (ferror(pSource)) perror("fread");
		else fprintf(stderr, "ERROR: EOF reached.\n");
		return -1;
	}
	
	fclose(pSource);

	size = newsize;
	newsize = (size << 7)/125;

	pMemDest = (uint8_t *)malloc(newsize);
	if (pMemDest == NULL) {
		fprintf(stderr, "ERROR: malloc(%u) failed.\n", newsize);
		return -1;
	}

	/* Encode */
	for (i = 500, j = 512; i < size; i += 250, j += 256) {
		encode_250(pMemSource+i, pMemDest+j);
	}

	if (!raw) {
		for (i = 512, checksum = 0; i < newsize; i++) {
			checksum += pMemDest[i];
		}

		update_header(pMemSource, newsize, checksum);
	}

	encode_250(pMemSource, pMemDest);
	encode_250(pMemSource+250, pMemDest+256);

	/* Open destination file */
	pDest = fopen(dstfile, "wb");
	if (pDest == NULL) {
		perror("fopen");
		return -1;
	}

	r = fseek(pDest, 0, SEEK_SET);
	if (r < 0) {
		perror("fseek");
		return -1;
	}

	/* Write to destination file */
	r = fwrite(pMemDest, sizeof(uint8_t), newsize, pDest);
	if (r < newsize) {
		perror("write");
		return -1;
	}
	
	fclose(pDest);
	
	free(pMemDest);
	free(pMemSource);

	return 0;
}


int
main(int argc, char *argv[])
{
	int r;

	int decode = -1;
	int raw = 0;
	int skip_checksums = 0;
	int opt;

	while ((opt = getopt(argc, argv, "edrhs")) != -1) {
		switch (opt) {
		case 'e':
			decode = 0;
			break;
		case 'd':
			decode = 1;
			break;
		case 'r':
			raw = 1;
			break;
		case 's':
			skip_checksums = 1;
			break;
		case 'h':
			printf(HELP, argv[0]);
			exit(EXIT_SUCCESS);
			break;
		default:
			fprintf(stderr, USAGE, argv[0]);
			exit(EXIT_FAILURE);
			break;
		}
	}

	/* decode or encode mode must be chosen */
	if (decode == -1) {
		fprintf(stderr, USAGE, argv[0]);
		exit(EXIT_FAILURE);
	}

	char *in_file = NULL;
	char *out_file = NULL;

	/* input file */
	if (optind < argc) in_file = argv[optind++];
	else {
		fprintf(stderr, USAGE, argv[0]);
		exit(EXIT_FAILURE);
	}

	/* output file */
	if (optind < argc) out_file = argv[optind++];
	else {
		fprintf(stderr, USAGE, argv[0]);
		exit(EXIT_FAILURE);
	}

	if (decode) {
		r = decode_file(in_file, out_file, skip_checksums);
		if (r < 0) exit(EXIT_FAILURE);
	} else {
		r = encode_file(in_file, out_file, raw);
		if (r < 0) exit(EXIT_FAILURE);
	}

	return EXIT_SUCCESS;
}