#define _GNU_SOURCE

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

/*
 * Normal 64-bit CRC calculation.
 *
 * This is a basic crc64 implementation following ECMA-182 specification,
 * which can be found from,
 * http://www.ecma-international.org/publications/standards/Ecma-182.htm
 *
 * Dr. Ross N. Williams has a great document to introduce the idea of CRC
 * algorithm, here the CRC64 code is also inspired by the table-driven
 * algorithm and detail example from this paper. This paper can be found
 * from,
 * http://www.ross.net/crc/download/crc_v3.txt
 *
 * crc64table[256] is the lookup table of a table-driven 64-bit CRC
 * calculation, which is generated by gen_crc64table.c in kernel build
 * time. The polynomial of crc64 arithmetic is from ECMA-182 specification
 * as well, which is defined as,
 *
 * x^64 + x^62 + x^57 + x^55 + x^54 + x^53 + x^52 + x^47 + x^46 + x^45 +
 * x^40 + x^39 + x^38 + x^37 + x^35 + x^33 + x^32 + x^31 + x^29 + x^27 +
 * x^24 + x^23 + x^22 + x^21 + x^19 + x^17 + x^13 + x^12 + x^10 + x^9 +
 * x^7 + x^4 + x + 1
 *
 * crc64table[256] is generated by output of gen_crc64table from Linux
 * kernel source code lib/gen_crc64table.c, crc64_be() is also copied
 * and modified from Linux kernel source code lib/crc64.c.
 *
 */

static const uint64_t crc64table[256] = {
	0x0000000000000000ULL, 	0x42f0e1eba9ea3693ULL,
	0x85e1c3d753d46d26ULL, 	0xc711223cfa3e5bb5ULL,
	0x493366450e42ecdfULL, 	0x0bc387aea7a8da4cULL,
	0xccd2a5925d9681f9ULL, 	0x8e224479f47cb76aULL,
	0x9266cc8a1c85d9beULL, 	0xd0962d61b56fef2dULL,
	0x17870f5d4f51b498ULL, 	0x5577eeb6e6bb820bULL,
	0xdb55aacf12c73561ULL, 	0x99a54b24bb2d03f2ULL,
	0x5eb4691841135847ULL, 	0x1c4488f3e8f96ed4ULL,
	0x663d78ff90e185efULL, 	0x24cd9914390bb37cULL,
	0xe3dcbb28c335e8c9ULL, 	0xa12c5ac36adfde5aULL,
	0x2f0e1eba9ea36930ULL, 	0x6dfeff5137495fa3ULL,
	0xaaefdd6dcd770416ULL, 	0xe81f3c86649d3285ULL,
	0xf45bb4758c645c51ULL, 	0xb6ab559e258e6ac2ULL,
	0x71ba77a2dfb03177ULL, 	0x334a9649765a07e4ULL,
	0xbd68d2308226b08eULL, 	0xff9833db2bcc861dULL,
	0x388911e7d1f2dda8ULL, 	0x7a79f00c7818eb3bULL,
	0xcc7af1ff21c30bdeULL, 	0x8e8a101488293d4dULL,
	0x499b3228721766f8ULL, 	0x0b6bd3c3dbfd506bULL,
	0x854997ba2f81e701ULL, 	0xc7b97651866bd192ULL,
	0x00a8546d7c558a27ULL, 	0x4258b586d5bfbcb4ULL,
	0x5e1c3d753d46d260ULL, 	0x1cecdc9e94ace4f3ULL,
	0xdbfdfea26e92bf46ULL, 	0x990d1f49c77889d5ULL,
	0x172f5b3033043ebfULL, 	0x55dfbadb9aee082cULL,
	0x92ce98e760d05399ULL, 	0xd03e790cc93a650aULL,
	0xaa478900b1228e31ULL, 	0xe8b768eb18c8b8a2ULL,
	0x2fa64ad7e2f6e317ULL, 	0x6d56ab3c4b1cd584ULL,
	0xe374ef45bf6062eeULL, 	0xa1840eae168a547dULL,
	0x66952c92ecb40fc8ULL, 	0x2465cd79455e395bULL,
	0x3821458aada7578fULL, 	0x7ad1a461044d611cULL,
	0xbdc0865dfe733aa9ULL, 	0xff3067b657990c3aULL,
	0x711223cfa3e5bb50ULL, 	0x33e2c2240a0f8dc3ULL,
	0xf4f3e018f031d676ULL, 	0xb60301f359dbe0e5ULL,
	0xda050215ea6c212fULL, 	0x98f5e3fe438617bcULL,
	0x5fe4c1c2b9b84c09ULL, 	0x1d14202910527a9aULL,
	0x93366450e42ecdf0ULL, 	0xd1c685bb4dc4fb63ULL,
	0x16d7a787b7faa0d6ULL, 	0x5427466c1e109645ULL,
	0x4863ce9ff6e9f891ULL, 	0x0a932f745f03ce02ULL,
	0xcd820d48a53d95b7ULL, 	0x8f72eca30cd7a324ULL,
	0x0150a8daf8ab144eULL, 	0x43a04931514122ddULL,
	0x84b16b0dab7f7968ULL, 	0xc6418ae602954ffbULL,
	0xbc387aea7a8da4c0ULL, 	0xfec89b01d3679253ULL,
	0x39d9b93d2959c9e6ULL, 	0x7b2958d680b3ff75ULL,
	0xf50b1caf74cf481fULL, 	0xb7fbfd44dd257e8cULL,
	0x70eadf78271b2539ULL, 	0x321a3e938ef113aaULL,
	0x2e5eb66066087d7eULL, 	0x6cae578bcfe24bedULL,
	0xabbf75b735dc1058ULL, 	0xe94f945c9c3626cbULL,
	0x676dd025684a91a1ULL, 	0x259d31cec1a0a732ULL,
	0xe28c13f23b9efc87ULL, 	0xa07cf2199274ca14ULL,
	0x167ff3eacbaf2af1ULL, 	0x548f120162451c62ULL,
	0x939e303d987b47d7ULL, 	0xd16ed1d631917144ULL,
	0x5f4c95afc5edc62eULL, 	0x1dbc74446c07f0bdULL,
	0xdaad56789639ab08ULL, 	0x985db7933fd39d9bULL,
	0x84193f60d72af34fULL, 	0xc6e9de8b7ec0c5dcULL,
	0x01f8fcb784fe9e69ULL, 	0x43081d5c2d14a8faULL,
	0xcd2a5925d9681f90ULL, 	0x8fdab8ce70822903ULL,
	0x48cb9af28abc72b6ULL, 	0x0a3b7b1923564425ULL,
	0x70428b155b4eaf1eULL, 	0x32b26afef2a4998dULL,
	0xf5a348c2089ac238ULL, 	0xb753a929a170f4abULL,
	0x3971ed50550c43c1ULL, 	0x7b810cbbfce67552ULL,
	0xbc902e8706d82ee7ULL, 	0xfe60cf6caf321874ULL,
	0xe224479f47cb76a0ULL, 	0xa0d4a674ee214033ULL,
	0x67c58448141f1b86ULL, 	0x253565a3bdf52d15ULL,
	0xab1721da49899a7fULL, 	0xe9e7c031e063acecULL,
	0x2ef6e20d1a5df759ULL, 	0x6c0603e6b3b7c1caULL,
	0xf6fae5c07d3274cdULL, 	0xb40a042bd4d8425eULL,
	0x731b26172ee619ebULL, 	0x31ebc7fc870c2f78ULL,
	0xbfc9838573709812ULL, 	0xfd39626eda9aae81ULL,
	0x3a28405220a4f534ULL, 	0x78d8a1b9894ec3a7ULL,
	0x649c294a61b7ad73ULL, 	0x266cc8a1c85d9be0ULL,
	0xe17dea9d3263c055ULL, 	0xa38d0b769b89f6c6ULL,
	0x2daf4f0f6ff541acULL, 	0x6f5faee4c61f773fULL,
	0xa84e8cd83c212c8aULL, 	0xeabe6d3395cb1a19ULL,
	0x90c79d3fedd3f122ULL, 	0xd2377cd44439c7b1ULL,
	0x15265ee8be079c04ULL, 	0x57d6bf0317edaa97ULL,
	0xd9f4fb7ae3911dfdULL, 	0x9b041a914a7b2b6eULL,
	0x5c1538adb04570dbULL, 	0x1ee5d94619af4648ULL,
	0x02a151b5f156289cULL, 	0x4051b05e58bc1e0fULL,
	0x87409262a28245baULL, 	0xc5b073890b687329ULL,
	0x4b9237f0ff14c443ULL, 	0x0962d61b56fef2d0ULL,
	0xce73f427acc0a965ULL, 	0x8c8315cc052a9ff6ULL,
	0x3a80143f5cf17f13ULL, 	0x7870f5d4f51b4980ULL,
	0xbf61d7e80f251235ULL, 	0xfd913603a6cf24a6ULL,
	0x73b3727a52b393ccULL, 	0x31439391fb59a55fULL,
	0xf652b1ad0167feeaULL, 	0xb4a25046a88dc879ULL,
	0xa8e6d8b54074a6adULL, 	0xea16395ee99e903eULL,
	0x2d071b6213a0cb8bULL, 	0x6ff7fa89ba4afd18ULL,
	0xe1d5bef04e364a72ULL, 	0xa3255f1be7dc7ce1ULL,
	0x64347d271de22754ULL, 	0x26c49cccb40811c7ULL,
	0x5cbd6cc0cc10fafcULL, 	0x1e4d8d2b65facc6fULL,
	0xd95caf179fc497daULL, 	0x9bac4efc362ea149ULL,
	0x158e0a85c2521623ULL, 	0x577eeb6e6bb820b0ULL,
	0x906fc95291867b05ULL, 	0xd29f28b9386c4d96ULL,
	0xcedba04ad0952342ULL, 	0x8c2b41a1797f15d1ULL,
	0x4b3a639d83414e64ULL, 	0x09ca82762aab78f7ULL,
	0x87e8c60fded7cf9dULL, 	0xc51827e4773df90eULL,
	0x020905d88d03a2bbULL, 	0x40f9e43324e99428ULL,
	0x2cffe7d5975e55e2ULL, 	0x6e0f063e3eb46371ULL,
	0xa91e2402c48a38c4ULL, 	0xebeec5e96d600e57ULL,
	0x65cc8190991cb93dULL, 	0x273c607b30f68faeULL,
	0xe02d4247cac8d41bULL, 	0xa2dda3ac6322e288ULL,
	0xbe992b5f8bdb8c5cULL, 	0xfc69cab42231bacfULL,
	0x3b78e888d80fe17aULL, 	0x7988096371e5d7e9ULL,
	0xf7aa4d1a85996083ULL, 	0xb55aacf12c735610ULL,
	0x724b8ecdd64d0da5ULL, 	0x30bb6f267fa73b36ULL,
	0x4ac29f2a07bfd00dULL, 	0x08327ec1ae55e69eULL,
	0xcf235cfd546bbd2bULL, 	0x8dd3bd16fd818bb8ULL,
	0x03f1f96f09fd3cd2ULL, 	0x41011884a0170a41ULL,
	0x86103ab85a2951f4ULL, 	0xc4e0db53f3c36767ULL,
	0xd8a453a01b3a09b3ULL, 	0x9a54b24bb2d03f20ULL,
	0x5d45907748ee6495ULL, 	0x1fb5719ce1045206ULL,
	0x919735e51578e56cULL, 	0xd367d40ebc92d3ffULL,
	0x1476f63246ac884aULL, 	0x568617d9ef46bed9ULL,
	0xe085162ab69d5e3cULL, 	0xa275f7c11f7768afULL,
	0x6564d5fde549331aULL, 	0x279434164ca30589ULL,
	0xa9b6706fb8dfb2e3ULL, 	0xeb46918411358470ULL,
	0x2c57b3b8eb0bdfc5ULL, 	0x6ea7525342e1e956ULL,
	0x72e3daa0aa188782ULL, 	0x30133b4b03f2b111ULL,
	0xf7021977f9cceaa4ULL, 	0xb5f2f89c5026dc37ULL,
	0x3bd0bce5a45a6b5dULL, 	0x79205d0e0db05dceULL,
	0xbe317f32f78e067bULL, 	0xfcc19ed95e6430e8ULL,
	0x86b86ed5267cdbd3ULL, 	0xc4488f3e8f96ed40ULL,
	0x0359ad0275a8b6f5ULL, 	0x41a94ce9dc428066ULL,
	0xcf8b0890283e370cULL, 	0x8d7be97b81d4019fULL,
	0x4a6acb477bea5a2aULL, 	0x089a2aacd2006cb9ULL,
	0x14dea25f3af9026dULL, 	0x562e43b4931334feULL,
	0x913f6188692d6f4bULL, 	0xd3cf8063c0c759d8ULL,
	0x5dedc41a34bbeeb2ULL, 	0x1f1d25f19d51d821ULL,
	0xd80c07cd676f8394ULL, 	0x9afce626ce85b507ULL,
};

/**
 * crc64_be - Calculate bitwise big-endian ECMA-182 CRC64
 * @crc: seed value for computation. 0 or (u64)~0 for a new CRC calculation,
        or the previous crc64 value if computing incrementally.
 * @p: pointer to buffer over which CRC64 is run
 * @len: length of buffer @p
 */
static uint64_t crc64_be(uint64_t crc, const void *p, size_t len)
{
        size_t i, t;

        const unsigned char *_p = p;

        for (i = 0; i < len; i++) {
                t = ((crc >> 56) ^ (*_p++)) & 0xFF;
                crc = crc64table[t] ^ (crc << 8);
        }

        return crc;
}

uint64_t crc64(const void *data, size_t len)
{
	uint64_t crc = 0xFFFFFFFFFFFFFFFFULL;

	crc = crc64_be(crc, data, len);
	return crc ^ 0xFFFFFFFFFFFFFFFFULL;
}