/*

 * Copied from btrfs-progs, kernel-lib/crc32c.c, which was:

 * Copied from the kernel source code, lib/libcrc32c.c.

 *

 * This program is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License as published by the Free

 * Software Foundation; either version 2 of the License, or (at your option)

 * any later version.

 *

 */

#include <stdlib.h>

#include <inttypes.h>

#include "crc32c.h"

static uint32_t __crc32c_le(uint32_t crc, unsigned char const *data, size_t length);

static uint32_t (*crc_function)(uint32_t crc, unsigned char const *data, size_t length) = __crc32c_le;

#ifdef __x86_64__

/*

 * Based on a posting to lkml by Austin Zhang <austin.zhang@intel.com>

 *

 * Using hardware provided CRC32 instruction to accelerate the CRC32 disposal.

 * CRC32C polynomial:0x1EDC6F41(BE)/0x82F63B78(LE)

 * CRC32 is a new instruction in Intel SSE4.2, the reference can be found at:

 * http://www.intel.com/products/processor/manuals/

 * Intel(R) 64 and IA-32 Architectures Software Developer's Manual

 * Volume 2A: Instruction Set Reference, A-M

 */

#if  __SIZEOF_LONG__ == 8

#define REX_PRE "0x48, "

#define SCALE_F 8

#else

#define REX_PRE

#define SCALE_F 4

#endif

static int crc32c_probed = 0;

static int crc32c_intel_available = 0;

static uint32_t crc32c_intel_le_hw_byte(uint32_t crc, unsigned char const *data,

					unsigned long length)

{

	while (length--) {

		__asm__ __volatile__(

			".byte 0xf2, 0xf, 0x38, 0xf0, 0xf1"

			:"=S"(crc)

			:"0"(crc), "c"(*data)

		);

		data++;

	}

	return crc;

}

/*

 * Steps through buffer one byte at at time, calculates reflected 

 * crc using table.

 */

static uint32_t crc32c_intel(uint32_t crc, unsigned char const *data, unsigned long length)

{

	unsigned int iquotient = length / SCALE_F;

	unsigned int iremainder = length % SCALE_F;

	unsigned long *ptmp = (unsigned long *)data;

	while (iquotient--) {

		__asm__ __volatile__(

			".byte 0xf2, " REX_PRE "0xf, 0x38, 0xf1, 0xf1;"

			:"=S"(crc)

			:"0"(crc), "c"(*ptmp)

		);

		ptmp++;

	}

	if (iremainder)

		crc = crc32c_intel_le_hw_byte(crc, (unsigned char *)ptmp,

				 iremainder);

	return crc;

}

static void do_cpuid(unsigned int *eax, unsigned int *ebx, unsigned int *ecx,

		     unsigned int *edx)

{

	int id = *eax;

	asm("movl %4, %%eax;"

	    "cpuid;"

	    "movl %%eax, %0;"

	    "movl %%ebx, %1;"

	    "movl %%ecx, %2;"

	    "movl %%edx, %3;"

		: "=r" (*eax), "=r" (*ebx), "=r" (*ecx), "=r" (*edx)

		: "r" (id)

		: "eax", "ebx", "ecx", "edx");

}

static void crc32c_intel_probe(void)

{

	if (!crc32c_probed) {

		unsigned int eax, ebx, ecx, edx;

		eax = 1;

		do_cpuid(&eax, &ebx, &ecx, &edx;;

		crc32c_intel_available = (ecx & (1 << 20)) != 0;

		crc32c_probed = 1;

	}

}

void crc32c_optimization_init(void)

{

	crc32c_intel_probe();

	if (crc32c_intel_available)

		crc_function = crc32c_intel;

}

#else

void crc32c_optimization_init(void)

{

}

#endif /* __x86_64__ */

/*

 * This is the CRC-32C table

 * Generated with:

 * width = 32 bits

 * poly = 0x1EDC6F41

 * reflect input bytes = true

 * reflect output bytes = true

 */

static const uint32_t crc32c_table[256] = {

	0x00000000L, 0xF26B8303L, 0xE13B70F7L, 0x1350F3F4L,

	0xC79A971FL, 0x35F1141CL, 0x26A1E7E8L, 0xD4CA64EBL,

	0x8AD958CFL, 0x78B2DBCCL, 0x6BE22838L, 0x9989AB3BL,

	0x4D43CFD0L, 0xBF284CD3L, 0xAC78BF27L, 0x5E133C24L,

	0x105EC76FL, 0xE235446CL, 0xF165B798L, 0x030E349BL,

	0xD7C45070L, 0x25AFD373L, 0x36FF2087L, 0xC494A384L,

	0x9A879FA0L, 0x68EC1CA3L, 0x7BBCEF57L, 0x89D76C54L,

	0x5D1D08BFL, 0xAF768BBCL, 0xBC267848L, 0x4E4DFB4BL,

	0x20BD8EDEL, 0xD2D60DDDL, 0xC186FE29L, 0x33ED7D2AL,

	0xE72719C1L, 0x154C9AC2L, 0x061C6936L, 0xF477EA35L,

	0xAA64D611L, 0x580F5512L, 0x4B5FA6E6L, 0xB93425E5L,

	0x6DFE410EL, 0x9F95C20DL, 0x8CC531F9L, 0x7EAEB2FAL,

	0x30E349B1L, 0xC288CAB2L, 0xD1D83946L, 0x23B3BA45L,

	0xF779DEAEL, 0x05125DADL, 0x1642AE59L, 0xE4292D5AL,

	0xBA3A117EL, 0x4851927DL, 0x5B016189L, 0xA96AE28AL,

	0x7DA08661L, 0x8FCB0562L, 0x9C9BF696L, 0x6EF07595L,

	0x417B1DBCL, 0xB3109EBFL, 0xA0406D4BL, 0x522BEE48L,

	0x86E18AA3L, 0x748A09A0L, 0x67DAFA54L, 0x95B17957L,

	0xCBA24573L, 0x39C9C670L, 0x2A993584L, 0xD8F2B687L,

	0x0C38D26CL, 0xFE53516FL, 0xED03A29BL, 0x1F682198L,

	0x5125DAD3L, 0xA34E59D0L, 0xB01EAA24L, 0x42752927L,

	0x96BF4DCCL, 0x64D4CECFL, 0x77843D3BL, 0x85EFBE38L,

	0xDBFC821CL, 0x2997011FL, 0x3AC7F2EBL, 0xC8AC71E8L,

	0x1C661503L, 0xEE0D9600L, 0xFD5D65F4L, 0x0F36E6F7L,

	0x61C69362L, 0x93AD1061L, 0x80FDE395L, 0x72966096L,

	0xA65C047DL, 0x5437877EL, 0x4767748AL, 0xB50CF789L,

	0xEB1FCBADL, 0x197448AEL, 0x0A24BB5AL, 0xF84F3859L,

	0x2C855CB2L, 0xDEEEDFB1L, 0xCDBE2C45L, 0x3FD5AF46L,

	0x7198540DL, 0x83F3D70EL, 0x90A324FAL, 0x62C8A7F9L,

	0xB602C312L, 0x44694011L, 0x5739B3E5L, 0xA55230E6L,

	0xFB410CC2L, 0x092A8FC1L, 0x1A7A7C35L, 0xE811FF36L,

	0x3CDB9BDDL, 0xCEB018DEL, 0xDDE0EB2AL, 0x2F8B6829L,

	0x82F63B78L, 0x709DB87BL, 0x63CD4B8FL, 0x91A6C88CL,

	0x456CAC67L, 0xB7072F64L, 0xA457DC90L, 0x563C5F93L,

	0x082F63B7L, 0xFA44E0B4L, 0xE9141340L, 0x1B7F9043L,

	0xCFB5F4A8L, 0x3DDE77ABL, 0x2E8E845FL, 0xDCE5075CL,

	0x92A8FC17L, 0x60C37F14L, 0x73938CE0L, 0x81F80FE3L,

	0x55326B08L, 0xA759E80BL, 0xB4091BFFL, 0x466298FCL,

	0x1871A4D8L, 0xEA1A27DBL, 0xF94AD42FL, 0x0B21572CL,

	0xDFEB33C7L, 0x2D80B0C4L, 0x3ED04330L, 0xCCBBC033L,

	0xA24BB5A6L, 0x502036A5L, 0x4370C551L, 0xB11B4652L,

	0x65D122B9L, 0x97BAA1BAL, 0x84EA524EL, 0x7681D14DL,

	0x2892ED69L, 0xDAF96E6AL, 0xC9A99D9EL, 0x3BC21E9DL,

	0xEF087A76L, 0x1D63F975L, 0x0E330A81L, 0xFC588982L,

	0xB21572C9L, 0x407EF1CAL, 0x532E023EL, 0xA145813DL,

	0x758FE5D6L, 0x87E466D5L, 0x94B49521L, 0x66DF1622L,

	0x38CC2A06L, 0xCAA7A905L, 0xD9F75AF1L, 0x2B9CD9F2L,

	0xFF56BD19L, 0x0D3D3E1AL, 0x1E6DCDEEL, 0xEC064EEDL,

	0xC38D26C4L, 0x31E6A5C7L, 0x22B65633L, 0xD0DDD530L,

	0x0417B1DBL, 0xF67C32D8L, 0xE52CC12CL, 0x1747422FL,

	0x49547E0BL, 0xBB3FFD08L, 0xA86F0EFCL, 0x5A048DFFL,

	0x8ECEE914L, 0x7CA56A17L, 0x6FF599E3L, 0x9D9E1AE0L,

	0xD3D3E1ABL, 0x21B862A8L, 0x32E8915CL, 0xC083125FL,

	0x144976B4L, 0xE622F5B7L, 0xF5720643L, 0x07198540L,

	0x590AB964L, 0xAB613A67L, 0xB831C993L, 0x4A5A4A90L,

	0x9E902E7BL, 0x6CFBAD78L, 0x7FAB5E8CL, 0x8DC0DD8FL,

	0xE330A81AL, 0x115B2B19L, 0x020BD8EDL, 0xF0605BEEL,

	0x24AA3F05L, 0xD6C1BC06L, 0xC5914FF2L, 0x37FACCF1L,

	0x69E9F0D5L, 0x9B8273D6L, 0x88D28022L, 0x7AB90321L,

	0xAE7367CAL, 0x5C18E4C9L, 0x4F48173DL, 0xBD23943EL,

	0xF36E6F75L, 0x0105EC76L, 0x12551F82L, 0xE03E9C81L,

	0x34F4F86AL, 0xC69F7B69L, 0xD5CF889DL, 0x27A40B9EL,

	0x79B737BAL, 0x8BDCB4B9L, 0x988C474DL, 0x6AE7C44EL,

	0xBE2DA0A5L, 0x4C4623A6L, 0x5F16D052L, 0xAD7D5351L

};

/*

 * Steps through buffer one byte at at time, calculates reflected 

 * crc using table.

 */

static uint32_t __crc32c_le(uint32_t crc, unsigned char const *data, size_t length)

{

	while (length--)

		crc =

		    crc32c_table[(crc ^ *data++) & 0xFFL] ^ (crc >> 8);

	return crc;

}

uint32_t crc32c(uint32_t crc, unsigned char const *data, size_t length)

{

	/* Use by-byte access for unaligned buffers */

	if ((unsigned long)data % sizeof(unsigned long))

		return __crc32c_le(crc, data, length);

	return crc_function(crc, data, length);

}