#include <stdio.h>
#include <stdlib.h>
#include <err.h>
#include <fcntl.h>
#include <string.h>
#include <stdint.h>
#include <sys/stat.h>
#include <sys/mman.h>

/*
 * http://www.xiph.org/ogg/doc/framing.html
 * http://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-600004.2
 */

#define	FIXED_LANG "LANGUAGE=Japanese"

int streamid;

/* From /usr/src/usr.bin/cksum/crc32 */

static const uint32_t crctab[256] = {
	0x0,
	0x04c11db7, 0x09823b6e, 0x0d4326d9, 0x130476dc, 0x17c56b6b,
	0x1a864db2, 0x1e475005, 0x2608edb8, 0x22c9f00f, 0x2f8ad6d6,
	0x2b4bcb61, 0x350c9b64, 0x31cd86d3, 0x3c8ea00a, 0x384fbdbd,
	0x4c11db70, 0x48d0c6c7, 0x4593e01e, 0x4152fda9, 0x5f15adac,
	0x5bd4b01b, 0x569796c2, 0x52568b75, 0x6a1936c8, 0x6ed82b7f,
	0x639b0da6, 0x675a1011, 0x791d4014, 0x7ddc5da3, 0x709f7b7a,
	0x745e66cd, 0x9823b6e0, 0x9ce2ab57, 0x91a18d8e, 0x95609039,
	0x8b27c03c, 0x8fe6dd8b, 0x82a5fb52, 0x8664e6e5, 0xbe2b5b58,
	0xbaea46ef, 0xb7a96036, 0xb3687d81, 0xad2f2d84, 0xa9ee3033,
	0xa4ad16ea, 0xa06c0b5d, 0xd4326d90, 0xd0f37027, 0xddb056fe,
	0xd9714b49, 0xc7361b4c, 0xc3f706fb, 0xceb42022, 0xca753d95,
	0xf23a8028, 0xf6fb9d9f, 0xfbb8bb46, 0xff79a6f1, 0xe13ef6f4,
	0xe5ffeb43, 0xe8bccd9a, 0xec7dd02d, 0x34867077, 0x30476dc0,
	0x3d044b19, 0x39c556ae, 0x278206ab, 0x23431b1c, 0x2e003dc5,
	0x2ac12072, 0x128e9dcf, 0x164f8078, 0x1b0ca6a1, 0x1fcdbb16,
	0x018aeb13, 0x054bf6a4, 0x0808d07d, 0x0cc9cdca, 0x7897ab07,
	0x7c56b6b0, 0x71159069, 0x75d48dde, 0x6b93dddb, 0x6f52c06c,
	0x6211e6b5, 0x66d0fb02, 0x5e9f46bf, 0x5a5e5b08, 0x571d7dd1,
	0x53dc6066, 0x4d9b3063, 0x495a2dd4, 0x44190b0d, 0x40d816ba,
	0xaca5c697, 0xa864db20, 0xa527fdf9, 0xa1e6e04e, 0xbfa1b04b,
	0xbb60adfc, 0xb6238b25, 0xb2e29692, 0x8aad2b2f, 0x8e6c3698,
	0x832f1041, 0x87ee0df6, 0x99a95df3, 0x9d684044, 0x902b669d,
	0x94ea7b2a, 0xe0b41de7, 0xe4750050, 0xe9362689, 0xedf73b3e,
	0xf3b06b3b, 0xf771768c, 0xfa325055, 0xfef34de2, 0xc6bcf05f,
	0xc27dede8, 0xcf3ecb31, 0xcbffd686, 0xd5b88683, 0xd1799b34,
	0xdc3abded, 0xd8fba05a, 0x690ce0ee, 0x6dcdfd59, 0x608edb80,
	0x644fc637, 0x7a089632, 0x7ec98b85, 0x738aad5c, 0x774bb0eb,
	0x4f040d56, 0x4bc510e1, 0x46863638, 0x42472b8f, 0x5c007b8a,
	0x58c1663d, 0x558240e4, 0x51435d53, 0x251d3b9e, 0x21dc2629,
	0x2c9f00f0, 0x285e1d47, 0x36194d42, 0x32d850f5, 0x3f9b762c,
	0x3b5a6b9b, 0x0315d626, 0x07d4cb91, 0x0a97ed48, 0x0e56f0ff,
	0x1011a0fa, 0x14d0bd4d, 0x19939b94, 0x1d528623, 0xf12f560e,
	0xf5ee4bb9, 0xf8ad6d60, 0xfc6c70d7, 0xe22b20d2, 0xe6ea3d65,
	0xeba91bbc, 0xef68060b, 0xd727bbb6, 0xd3e6a601, 0xdea580d8,
	0xda649d6f, 0xc423cd6a, 0xc0e2d0dd, 0xcda1f604, 0xc960ebb3,
	0xbd3e8d7e, 0xb9ff90c9, 0xb4bcb610, 0xb07daba7, 0xae3afba2,
	0xaafbe615, 0xa7b8c0cc, 0xa379dd7b, 0x9b3660c6, 0x9ff77d71,
	0x92b45ba8, 0x9675461f, 0x8832161a, 0x8cf30bad, 0x81b02d74,
	0x857130c3, 0x5d8a9099, 0x594b8d2e, 0x5408abf7, 0x50c9b640,
	0x4e8ee645, 0x4a4ffbf2, 0x470cdd2b, 0x43cdc09c, 0x7b827d21,
	0x7f436096, 0x7200464f, 0x76c15bf8, 0x68860bfd, 0x6c47164a,
	0x61043093, 0x65c52d24, 0x119b4be9, 0x155a565e, 0x18197087,
	0x1cd86d30, 0x029f3d35, 0x065e2082, 0x0b1d065b, 0x0fdc1bec,
	0x3793a651, 0x3352bbe6, 0x3e119d3f, 0x3ad08088, 0x2497d08d,
	0x2056cd3a, 0x2d15ebe3, 0x29d4f654, 0xc5a92679, 0xc1683bce,
	0xcc2b1d17, 0xc8ea00a0, 0xd6ad50a5, 0xd26c4d12, 0xdf2f6bcb,
	0xdbee767c, 0xe3a1cbc1, 0xe760d676, 0xea23f0af, 0xeee2ed18,
	0xf0a5bd1d, 0xf464a0aa, 0xf9278673, 0xfde69bc4, 0x89b8fd09,
	0x8d79e0be, 0x803ac667, 0x84fbdbd0, 0x9abc8bd5, 0x9e7d9662,
	0x933eb0bb, 0x97ffad0c, 0xafb010b1, 0xab710d06, 0xa6322bdf,
	0xa2f33668, 0xbcb4666d, 0xb8757bda, 0xb5365d03, 0xb1f740b4
};

uint32_t
compute_crc32(char *m, off_t len)
{
	unsigned char *_m;
	uint32_t lcrc;

	_m = malloc(len);
	memcpy(_m, m, len);
	/* Zero out the crc */
	memset(_m + 22, 0, 4);

	lcrc = 0;
	for (; len--; ++_m)
		lcrc = (lcrc << 8) ^ crctab[((lcrc >> 24) & 0xff) ^ *_m];

	free (_m);

	return (lcrc);
}

void
fix_lang(char *m)
{
	uint32_t ncomments, clen, vlen;
	int i, off, tlen;

	vlen = *(uint32_t *)m;
	printf("vlen %d\n", vlen);
	ncomments = *(uint32_t *)(m + 4 + vlen);
	off = 8 + vlen;
	tlen = 0;
	for (i = 0; i < ncomments; i++) {
		clen = *(uint32_t *)(m + off);
		off += clen + 4;
		tlen += clen + 4;
	}

	/* Change to 2 comments */
	*(uint32_t *)(m + vlen + 4) = 2;

	/* New language */
	*(uint32_t *)(m + vlen + 8) = strlen(FIXED_LANG);
	memcpy(m + vlen + 12, FIXED_LANG, strlen(FIXED_LANG));

	/* Padding */
	*(uint32_t *)(m + vlen + 12 + strlen(FIXED_LANG)) = tlen -
	    strlen(FIXED_LANG) - 8;
	memset(m + vlen + 16 + strlen(FIXED_LANG), 'A', tlen -
	    strlen(FIXED_LANG) - 8);
}

int
read_page(char *m, long *_off)
{
	unsigned char nsegs, *segs;
	uint64_t granule;
	uint32_t crc, _crc, sequence, stream;
	long off, local_off;
	int i, total_size;

	off = *_off;

	if (strncmp(m + off, "OggS", 4) || m[off + 4] != 0) {
		printf("bad capture pattern at %ld\n", off);
		printf("%c%c%c%c %.2hhx\n", m[off], m[off + 1], m[off + 2],
		    m[off + 3], m[off + 4]);
		return (1);
	}

	granule = *(uint64_t *)(m + off + 6);
	stream = *(uint32_t *)(m + off + 14);
	sequence = *(uint32_t *)(m + off + 18);
	crc = *(uint32_t *)(m + off + 22);
	nsegs = m[off + 26];

	if (stream == streamid) {
		printf("page at offset 0x%lx (%ld)\n", off, off);
		printf("  type: %.2hhx\n", m[off + 5]);
		printf("  granule: %lx\n", granule);
		printf("  stream: %d\n", stream);
		printf("  sequence: 0x%x\n", sequence);
		printf("  segments: %.2hhx\n", nsegs);
		printf("  CRC: 0x%.4x\n", crc);
	}

	segs = malloc(nsegs);
	total_size = 27 + nsegs;
	for (i = 0; i < nsegs; i++) {
		segs[i] = m[off + 27 + i];
		total_size += segs[i];
		if (stream == streamid)
			printf("    seg %d: 0x%.2hhx (%hhu) bytes\n", i,
			    segs[i], segs[i]);
	}

	_crc = compute_crc32(m + off, total_size);
	if (_crc != crc) {
		printf("invalid crc for page at 0x%lx %x != %x\n", off, _crc,
		    crc);
		return (1);
	}

	if (stream != streamid)
		goto out;
	
	local_off = off + 27 + nsegs;
	for (i = 0; i < nsegs; i++) {
		if (!strncmp(m + local_off, "\x03vorbis", 7)) {
			printf("FOUND at 0x%lx!\n", local_off);
			fix_lang(m + local_off + 7);
			/* Fixup crc */
			crc = compute_crc32(m + off, total_size);
			*(uint32_t *)(m + off + 22) = crc;
			return (1);
		}
		local_off += segs[i];
	}

out:
	free(segs);
	*_off += total_size;
	return (0);
}

int
main(int argc, char **argv)
{
	struct stat stat;
	char *m;
	long off;
	int fd;

	if (argc < 3)
		errx(1, "Usage: %s <file> <stream id>", argv[0]);

	streamid = atoi(argv[2]);

	if ((fd = open(argv[1], O_RDWR)) == -1)
		err(1, "open");

	if (fstat(fd, &stat) < 0)
		err(1, "fstat");

	m = mmap(NULL, stat.st_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
	if (m == MAP_FAILED)
		err(1, "mmap");

	off = 0;
	while (read_page(m, &off) == 0);

	return (0);
}