Revision df38c1ce660628f05b4686eeaf0b548295ce7967 authored by Mike Kolupaev on 22 April 2019, 15:17:45 UTC, committed by Facebook Github Bot on 22 April 2019, 15:20:35 UTC
Summary:
Introduce BlockBasedTableOptions::index_shortening to give users control on which key shortening techniques to be used in building index blocks. Before this patch, both separators and successor keys where shortened in indexes. With this patch, the default is set to kShortenSeparators to only shorten the separators. Since each index block has many separators and only one successor (last key), the change should not have negative impact on index block size. However it should prevent many unnecessary block loads where due to approximation introduced by shorted successor, seek would land us to the previous block and then fix it by moving to the next one.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5174

Differential Revision: D14884185

Pulled By: al13n321

fbshipit-source-id: 1b08bc8c03edcf09b6b8c16e9a7eea08ad4dd534
1 parent de76909
Raw File
crc32c.cc
//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
//  This source code is licensed under both the GPLv2 (found in the
//  COPYING file in the root directory) and Apache 2.0 License
//  (found in the LICENSE.Apache file in the root directory).
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
//
// A portable implementation of crc32c, optimized to handle
// four bytes at a time.
#include "util/crc32c.h"
#include <stdint.h>
#ifdef HAVE_SSE42
#include <nmmintrin.h>
#include <wmmintrin.h>
#endif
#include "util/coding.h"
#include "util/util.h"

#ifdef __powerpc64__
#include "util/crc32c_ppc.h"
#include "util/crc32c_ppc_constants.h"

#if __linux__
#include <sys/auxv.h>

#ifndef PPC_FEATURE2_VEC_CRYPTO
#define PPC_FEATURE2_VEC_CRYPTO 0x02000000
#endif

#ifndef AT_HWCAP2
#define AT_HWCAP2 26
#endif

#endif /* __linux__ */

#endif

namespace rocksdb {
namespace crc32c {

#if defined(HAVE_POWER8) && defined(HAS_ALTIVEC)
#ifdef __powerpc64__
static int arch_ppc_crc32 = 0;
#endif /* __powerpc64__ */
#endif

static const uint32_t table0_[256] = {
  0x00000000, 0xf26b8303, 0xe13b70f7, 0x1350f3f4,
  0xc79a971f, 0x35f1141c, 0x26a1e7e8, 0xd4ca64eb,
  0x8ad958cf, 0x78b2dbcc, 0x6be22838, 0x9989ab3b,
  0x4d43cfd0, 0xbf284cd3, 0xac78bf27, 0x5e133c24,
  0x105ec76f, 0xe235446c, 0xf165b798, 0x030e349b,
  0xd7c45070, 0x25afd373, 0x36ff2087, 0xc494a384,
  0x9a879fa0, 0x68ec1ca3, 0x7bbcef57, 0x89d76c54,
  0x5d1d08bf, 0xaf768bbc, 0xbc267848, 0x4e4dfb4b,
  0x20bd8ede, 0xd2d60ddd, 0xc186fe29, 0x33ed7d2a,
  0xe72719c1, 0x154c9ac2, 0x061c6936, 0xf477ea35,
  0xaa64d611, 0x580f5512, 0x4b5fa6e6, 0xb93425e5,
  0x6dfe410e, 0x9f95c20d, 0x8cc531f9, 0x7eaeb2fa,
  0x30e349b1, 0xc288cab2, 0xd1d83946, 0x23b3ba45,
  0xf779deae, 0x05125dad, 0x1642ae59, 0xe4292d5a,
  0xba3a117e, 0x4851927d, 0x5b016189, 0xa96ae28a,
  0x7da08661, 0x8fcb0562, 0x9c9bf696, 0x6ef07595,
  0x417b1dbc, 0xb3109ebf, 0xa0406d4b, 0x522bee48,
  0x86e18aa3, 0x748a09a0, 0x67dafa54, 0x95b17957,
  0xcba24573, 0x39c9c670, 0x2a993584, 0xd8f2b687,
  0x0c38d26c, 0xfe53516f, 0xed03a29b, 0x1f682198,
  0x5125dad3, 0xa34e59d0, 0xb01eaa24, 0x42752927,
  0x96bf4dcc, 0x64d4cecf, 0x77843d3b, 0x85efbe38,
  0xdbfc821c, 0x2997011f, 0x3ac7f2eb, 0xc8ac71e8,
  0x1c661503, 0xee0d9600, 0xfd5d65f4, 0x0f36e6f7,
  0x61c69362, 0x93ad1061, 0x80fde395, 0x72966096,
  0xa65c047d, 0x5437877e, 0x4767748a, 0xb50cf789,
  0xeb1fcbad, 0x197448ae, 0x0a24bb5a, 0xf84f3859,
  0x2c855cb2, 0xdeeedfb1, 0xcdbe2c45, 0x3fd5af46,
  0x7198540d, 0x83f3d70e, 0x90a324fa, 0x62c8a7f9,
  0xb602c312, 0x44694011, 0x5739b3e5, 0xa55230e6,
  0xfb410cc2, 0x092a8fc1, 0x1a7a7c35, 0xe811ff36,
  0x3cdb9bdd, 0xceb018de, 0xdde0eb2a, 0x2f8b6829,
  0x82f63b78, 0x709db87b, 0x63cd4b8f, 0x91a6c88c,
  0x456cac67, 0xb7072f64, 0xa457dc90, 0x563c5f93,
  0x082f63b7, 0xfa44e0b4, 0xe9141340, 0x1b7f9043,
  0xcfb5f4a8, 0x3dde77ab, 0x2e8e845f, 0xdce5075c,
  0x92a8fc17, 0x60c37f14, 0x73938ce0, 0x81f80fe3,
  0x55326b08, 0xa759e80b, 0xb4091bff, 0x466298fc,
  0x1871a4d8, 0xea1a27db, 0xf94ad42f, 0x0b21572c,
  0xdfeb33c7, 0x2d80b0c4, 0x3ed04330, 0xccbbc033,
  0xa24bb5a6, 0x502036a5, 0x4370c551, 0xb11b4652,
  0x65d122b9, 0x97baa1ba, 0x84ea524e, 0x7681d14d,
  0x2892ed69, 0xdaf96e6a, 0xc9a99d9e, 0x3bc21e9d,
  0xef087a76, 0x1d63f975, 0x0e330a81, 0xfc588982,
  0xb21572c9, 0x407ef1ca, 0x532e023e, 0xa145813d,
  0x758fe5d6, 0x87e466d5, 0x94b49521, 0x66df1622,
  0x38cc2a06, 0xcaa7a905, 0xd9f75af1, 0x2b9cd9f2,
  0xff56bd19, 0x0d3d3e1a, 0x1e6dcdee, 0xec064eed,
  0xc38d26c4, 0x31e6a5c7, 0x22b65633, 0xd0ddd530,
  0x0417b1db, 0xf67c32d8, 0xe52cc12c, 0x1747422f,
  0x49547e0b, 0xbb3ffd08, 0xa86f0efc, 0x5a048dff,
  0x8ecee914, 0x7ca56a17, 0x6ff599e3, 0x9d9e1ae0,
  0xd3d3e1ab, 0x21b862a8, 0x32e8915c, 0xc083125f,
  0x144976b4, 0xe622f5b7, 0xf5720643, 0x07198540,
  0x590ab964, 0xab613a67, 0xb831c993, 0x4a5a4a90,
  0x9e902e7b, 0x6cfbad78, 0x7fab5e8c, 0x8dc0dd8f,
  0xe330a81a, 0x115b2b19, 0x020bd8ed, 0xf0605bee,
  0x24aa3f05, 0xd6c1bc06, 0xc5914ff2, 0x37faccf1,
  0x69e9f0d5, 0x9b8273d6, 0x88d28022, 0x7ab90321,
  0xae7367ca, 0x5c18e4c9, 0x4f48173d, 0xbd23943e,
  0xf36e6f75, 0x0105ec76, 0x12551f82, 0xe03e9c81,
  0x34f4f86a, 0xc69f7b69, 0xd5cf889d, 0x27a40b9e,
  0x79b737ba, 0x8bdcb4b9, 0x988c474d, 0x6ae7c44e,
  0xbe2da0a5, 0x4c4623a6, 0x5f16d052, 0xad7d5351
};
static const uint32_t table1_[256] = {
  0x00000000, 0x13a29877, 0x274530ee, 0x34e7a899,
  0x4e8a61dc, 0x5d28f9ab, 0x69cf5132, 0x7a6dc945,
  0x9d14c3b8, 0x8eb65bcf, 0xba51f356, 0xa9f36b21,
  0xd39ea264, 0xc03c3a13, 0xf4db928a, 0xe7790afd,
  0x3fc5f181, 0x2c6769f6, 0x1880c16f, 0x0b225918,
  0x714f905d, 0x62ed082a, 0x560aa0b3, 0x45a838c4,
  0xa2d13239, 0xb173aa4e, 0x859402d7, 0x96369aa0,
  0xec5b53e5, 0xfff9cb92, 0xcb1e630b, 0xd8bcfb7c,
  0x7f8be302, 0x6c297b75, 0x58ced3ec, 0x4b6c4b9b,
  0x310182de, 0x22a31aa9, 0x1644b230, 0x05e62a47,
  0xe29f20ba, 0xf13db8cd, 0xc5da1054, 0xd6788823,
  0xac154166, 0xbfb7d911, 0x8b507188, 0x98f2e9ff,
  0x404e1283, 0x53ec8af4, 0x670b226d, 0x74a9ba1a,
  0x0ec4735f, 0x1d66eb28, 0x298143b1, 0x3a23dbc6,
  0xdd5ad13b, 0xcef8494c, 0xfa1fe1d5, 0xe9bd79a2,
  0x93d0b0e7, 0x80722890, 0xb4958009, 0xa737187e,
  0xff17c604, 0xecb55e73, 0xd852f6ea, 0xcbf06e9d,
  0xb19da7d8, 0xa23f3faf, 0x96d89736, 0x857a0f41,
  0x620305bc, 0x71a19dcb, 0x45463552, 0x56e4ad25,
  0x2c896460, 0x3f2bfc17, 0x0bcc548e, 0x186eccf9,
  0xc0d23785, 0xd370aff2, 0xe797076b, 0xf4359f1c,
  0x8e585659, 0x9dface2e, 0xa91d66b7, 0xbabffec0,
  0x5dc6f43d, 0x4e646c4a, 0x7a83c4d3, 0x69215ca4,
  0x134c95e1, 0x00ee0d96, 0x3409a50f, 0x27ab3d78,
  0x809c2506, 0x933ebd71, 0xa7d915e8, 0xb47b8d9f,
  0xce1644da, 0xddb4dcad, 0xe9537434, 0xfaf1ec43,
  0x1d88e6be, 0x0e2a7ec9, 0x3acdd650, 0x296f4e27,
  0x53028762, 0x40a01f15, 0x7447b78c, 0x67e52ffb,
  0xbf59d487, 0xacfb4cf0, 0x981ce469, 0x8bbe7c1e,
  0xf1d3b55b, 0xe2712d2c, 0xd69685b5, 0xc5341dc2,
  0x224d173f, 0x31ef8f48, 0x050827d1, 0x16aabfa6,
  0x6cc776e3, 0x7f65ee94, 0x4b82460d, 0x5820de7a,
  0xfbc3faf9, 0xe861628e, 0xdc86ca17, 0xcf245260,
  0xb5499b25, 0xa6eb0352, 0x920cabcb, 0x81ae33bc,
  0x66d73941, 0x7575a136, 0x419209af, 0x523091d8,
  0x285d589d, 0x3bffc0ea, 0x0f186873, 0x1cbaf004,
  0xc4060b78, 0xd7a4930f, 0xe3433b96, 0xf0e1a3e1,
  0x8a8c6aa4, 0x992ef2d3, 0xadc95a4a, 0xbe6bc23d,
  0x5912c8c0, 0x4ab050b7, 0x7e57f82e, 0x6df56059,
  0x1798a91c, 0x043a316b, 0x30dd99f2, 0x237f0185,
  0x844819fb, 0x97ea818c, 0xa30d2915, 0xb0afb162,
  0xcac27827, 0xd960e050, 0xed8748c9, 0xfe25d0be,
  0x195cda43, 0x0afe4234, 0x3e19eaad, 0x2dbb72da,
  0x57d6bb9f, 0x447423e8, 0x70938b71, 0x63311306,
  0xbb8de87a, 0xa82f700d, 0x9cc8d894, 0x8f6a40e3,
  0xf50789a6, 0xe6a511d1, 0xd242b948, 0xc1e0213f,
  0x26992bc2, 0x353bb3b5, 0x01dc1b2c, 0x127e835b,
  0x68134a1e, 0x7bb1d269, 0x4f567af0, 0x5cf4e287,
  0x04d43cfd, 0x1776a48a, 0x23910c13, 0x30339464,
  0x4a5e5d21, 0x59fcc556, 0x6d1b6dcf, 0x7eb9f5b8,
  0x99c0ff45, 0x8a626732, 0xbe85cfab, 0xad2757dc,
  0xd74a9e99, 0xc4e806ee, 0xf00fae77, 0xe3ad3600,
  0x3b11cd7c, 0x28b3550b, 0x1c54fd92, 0x0ff665e5,
  0x759baca0, 0x663934d7, 0x52de9c4e, 0x417c0439,
  0xa6050ec4, 0xb5a796b3, 0x81403e2a, 0x92e2a65d,
  0xe88f6f18, 0xfb2df76f, 0xcfca5ff6, 0xdc68c781,
  0x7b5fdfff, 0x68fd4788, 0x5c1aef11, 0x4fb87766,
  0x35d5be23, 0x26772654, 0x12908ecd, 0x013216ba,
  0xe64b1c47, 0xf5e98430, 0xc10e2ca9, 0xd2acb4de,
  0xa8c17d9b, 0xbb63e5ec, 0x8f844d75, 0x9c26d502,
  0x449a2e7e, 0x5738b609, 0x63df1e90, 0x707d86e7,
  0x0a104fa2, 0x19b2d7d5, 0x2d557f4c, 0x3ef7e73b,
  0xd98eedc6, 0xca2c75b1, 0xfecbdd28, 0xed69455f,
  0x97048c1a, 0x84a6146d, 0xb041bcf4, 0xa3e32483
};
static const uint32_t table2_[256] = {
  0x00000000, 0xa541927e, 0x4f6f520d, 0xea2ec073,
  0x9edea41a, 0x3b9f3664, 0xd1b1f617, 0x74f06469,
  0x38513ec5, 0x9d10acbb, 0x773e6cc8, 0xd27ffeb6,
  0xa68f9adf, 0x03ce08a1, 0xe9e0c8d2, 0x4ca15aac,
  0x70a27d8a, 0xd5e3eff4, 0x3fcd2f87, 0x9a8cbdf9,
  0xee7cd990, 0x4b3d4bee, 0xa1138b9d, 0x045219e3,
  0x48f3434f, 0xedb2d131, 0x079c1142, 0xa2dd833c,
  0xd62de755, 0x736c752b, 0x9942b558, 0x3c032726,
  0xe144fb14, 0x4405696a, 0xae2ba919, 0x0b6a3b67,
  0x7f9a5f0e, 0xdadbcd70, 0x30f50d03, 0x95b49f7d,
  0xd915c5d1, 0x7c5457af, 0x967a97dc, 0x333b05a2,
  0x47cb61cb, 0xe28af3b5, 0x08a433c6, 0xade5a1b8,
  0x91e6869e, 0x34a714e0, 0xde89d493, 0x7bc846ed,
  0x0f382284, 0xaa79b0fa, 0x40577089, 0xe516e2f7,
  0xa9b7b85b, 0x0cf62a25, 0xe6d8ea56, 0x43997828,
  0x37691c41, 0x92288e3f, 0x78064e4c, 0xdd47dc32,
  0xc76580d9, 0x622412a7, 0x880ad2d4, 0x2d4b40aa,
  0x59bb24c3, 0xfcfab6bd, 0x16d476ce, 0xb395e4b0,
  0xff34be1c, 0x5a752c62, 0xb05bec11, 0x151a7e6f,
  0x61ea1a06, 0xc4ab8878, 0x2e85480b, 0x8bc4da75,
  0xb7c7fd53, 0x12866f2d, 0xf8a8af5e, 0x5de93d20,
  0x29195949, 0x8c58cb37, 0x66760b44, 0xc337993a,
  0x8f96c396, 0x2ad751e8, 0xc0f9919b, 0x65b803e5,
  0x1148678c, 0xb409f5f2, 0x5e273581, 0xfb66a7ff,
  0x26217bcd, 0x8360e9b3, 0x694e29c0, 0xcc0fbbbe,
  0xb8ffdfd7, 0x1dbe4da9, 0xf7908dda, 0x52d11fa4,
  0x1e704508, 0xbb31d776, 0x511f1705, 0xf45e857b,
  0x80aee112, 0x25ef736c, 0xcfc1b31f, 0x6a802161,
  0x56830647, 0xf3c29439, 0x19ec544a, 0xbcadc634,
  0xc85da25d, 0x6d1c3023, 0x8732f050, 0x2273622e,
  0x6ed23882, 0xcb93aafc, 0x21bd6a8f, 0x84fcf8f1,
  0xf00c9c98, 0x554d0ee6, 0xbf63ce95, 0x1a225ceb,
  0x8b277743, 0x2e66e53d, 0xc448254e, 0x6109b730,
  0x15f9d359, 0xb0b84127, 0x5a968154, 0xffd7132a,
  0xb3764986, 0x1637dbf8, 0xfc191b8b, 0x595889f5,
  0x2da8ed9c, 0x88e97fe2, 0x62c7bf91, 0xc7862def,
  0xfb850ac9, 0x5ec498b7, 0xb4ea58c4, 0x11abcaba,
  0x655baed3, 0xc01a3cad, 0x2a34fcde, 0x8f756ea0,
  0xc3d4340c, 0x6695a672, 0x8cbb6601, 0x29faf47f,
  0x5d0a9016, 0xf84b0268, 0x1265c21b, 0xb7245065,
  0x6a638c57, 0xcf221e29, 0x250cde5a, 0x804d4c24,
  0xf4bd284d, 0x51fcba33, 0xbbd27a40, 0x1e93e83e,
  0x5232b292, 0xf77320ec, 0x1d5de09f, 0xb81c72e1,
  0xccec1688, 0x69ad84f6, 0x83834485, 0x26c2d6fb,
  0x1ac1f1dd, 0xbf8063a3, 0x55aea3d0, 0xf0ef31ae,
  0x841f55c7, 0x215ec7b9, 0xcb7007ca, 0x6e3195b4,
  0x2290cf18, 0x87d15d66, 0x6dff9d15, 0xc8be0f6b,
  0xbc4e6b02, 0x190ff97c, 0xf321390f, 0x5660ab71,
  0x4c42f79a, 0xe90365e4, 0x032da597, 0xa66c37e9,
  0xd29c5380, 0x77ddc1fe, 0x9df3018d, 0x38b293f3,
  0x7413c95f, 0xd1525b21, 0x3b7c9b52, 0x9e3d092c,
  0xeacd6d45, 0x4f8cff3b, 0xa5a23f48, 0x00e3ad36,
  0x3ce08a10, 0x99a1186e, 0x738fd81d, 0xd6ce4a63,
  0xa23e2e0a, 0x077fbc74, 0xed517c07, 0x4810ee79,
  0x04b1b4d5, 0xa1f026ab, 0x4bdee6d8, 0xee9f74a6,
  0x9a6f10cf, 0x3f2e82b1, 0xd50042c2, 0x7041d0bc,
  0xad060c8e, 0x08479ef0, 0xe2695e83, 0x4728ccfd,
  0x33d8a894, 0x96993aea, 0x7cb7fa99, 0xd9f668e7,
  0x9557324b, 0x3016a035, 0xda386046, 0x7f79f238,
  0x0b899651, 0xaec8042f, 0x44e6c45c, 0xe1a75622,
  0xdda47104, 0x78e5e37a, 0x92cb2309, 0x378ab177,
  0x437ad51e, 0xe63b4760, 0x0c158713, 0xa954156d,
  0xe5f54fc1, 0x40b4ddbf, 0xaa9a1dcc, 0x0fdb8fb2,
  0x7b2bebdb, 0xde6a79a5, 0x3444b9d6, 0x91052ba8
};
static const uint32_t table3_[256] = {
  0x00000000, 0xdd45aab8, 0xbf672381, 0x62228939,
  0x7b2231f3, 0xa6679b4b, 0xc4451272, 0x1900b8ca,
  0xf64463e6, 0x2b01c95e, 0x49234067, 0x9466eadf,
  0x8d665215, 0x5023f8ad, 0x32017194, 0xef44db2c,
  0xe964b13d, 0x34211b85, 0x560392bc, 0x8b463804,
  0x924680ce, 0x4f032a76, 0x2d21a34f, 0xf06409f7,
  0x1f20d2db, 0xc2657863, 0xa047f15a, 0x7d025be2,
  0x6402e328, 0xb9474990, 0xdb65c0a9, 0x06206a11,
  0xd725148b, 0x0a60be33, 0x6842370a, 0xb5079db2,
  0xac072578, 0x71428fc0, 0x136006f9, 0xce25ac41,
  0x2161776d, 0xfc24ddd5, 0x9e0654ec, 0x4343fe54,
  0x5a43469e, 0x8706ec26, 0xe524651f, 0x3861cfa7,
  0x3e41a5b6, 0xe3040f0e, 0x81268637, 0x5c632c8f,
  0x45639445, 0x98263efd, 0xfa04b7c4, 0x27411d7c,
  0xc805c650, 0x15406ce8, 0x7762e5d1, 0xaa274f69,
  0xb327f7a3, 0x6e625d1b, 0x0c40d422, 0xd1057e9a,
  0xaba65fe7, 0x76e3f55f, 0x14c17c66, 0xc984d6de,
  0xd0846e14, 0x0dc1c4ac, 0x6fe34d95, 0xb2a6e72d,
  0x5de23c01, 0x80a796b9, 0xe2851f80, 0x3fc0b538,
  0x26c00df2, 0xfb85a74a, 0x99a72e73, 0x44e284cb,
  0x42c2eeda, 0x9f874462, 0xfda5cd5b, 0x20e067e3,
  0x39e0df29, 0xe4a57591, 0x8687fca8, 0x5bc25610,
  0xb4868d3c, 0x69c32784, 0x0be1aebd, 0xd6a40405,
  0xcfa4bccf, 0x12e11677, 0x70c39f4e, 0xad8635f6,
  0x7c834b6c, 0xa1c6e1d4, 0xc3e468ed, 0x1ea1c255,
  0x07a17a9f, 0xdae4d027, 0xb8c6591e, 0x6583f3a6,
  0x8ac7288a, 0x57828232, 0x35a00b0b, 0xe8e5a1b3,
  0xf1e51979, 0x2ca0b3c1, 0x4e823af8, 0x93c79040,
  0x95e7fa51, 0x48a250e9, 0x2a80d9d0, 0xf7c57368,
  0xeec5cba2, 0x3380611a, 0x51a2e823, 0x8ce7429b,
  0x63a399b7, 0xbee6330f, 0xdcc4ba36, 0x0181108e,
  0x1881a844, 0xc5c402fc, 0xa7e68bc5, 0x7aa3217d,
  0x52a0c93f, 0x8fe56387, 0xedc7eabe, 0x30824006,
  0x2982f8cc, 0xf4c75274, 0x96e5db4d, 0x4ba071f5,
  0xa4e4aad9, 0x79a10061, 0x1b838958, 0xc6c623e0,
  0xdfc69b2a, 0x02833192, 0x60a1b8ab, 0xbde41213,
  0xbbc47802, 0x6681d2ba, 0x04a35b83, 0xd9e6f13b,
  0xc0e649f1, 0x1da3e349, 0x7f816a70, 0xa2c4c0c8,
  0x4d801be4, 0x90c5b15c, 0xf2e73865, 0x2fa292dd,
  0x36a22a17, 0xebe780af, 0x89c50996, 0x5480a32e,
  0x8585ddb4, 0x58c0770c, 0x3ae2fe35, 0xe7a7548d,
  0xfea7ec47, 0x23e246ff, 0x41c0cfc6, 0x9c85657e,
  0x73c1be52, 0xae8414ea, 0xcca69dd3, 0x11e3376b,
  0x08e38fa1, 0xd5a62519, 0xb784ac20, 0x6ac10698,
  0x6ce16c89, 0xb1a4c631, 0xd3864f08, 0x0ec3e5b0,
  0x17c35d7a, 0xca86f7c2, 0xa8a47efb, 0x75e1d443,
  0x9aa50f6f, 0x47e0a5d7, 0x25c22cee, 0xf8878656,
  0xe1873e9c, 0x3cc29424, 0x5ee01d1d, 0x83a5b7a5,
  0xf90696d8, 0x24433c60, 0x4661b559, 0x9b241fe1,
  0x8224a72b, 0x5f610d93, 0x3d4384aa, 0xe0062e12,
  0x0f42f53e, 0xd2075f86, 0xb025d6bf, 0x6d607c07,
  0x7460c4cd, 0xa9256e75, 0xcb07e74c, 0x16424df4,
  0x106227e5, 0xcd278d5d, 0xaf050464, 0x7240aedc,
  0x6b401616, 0xb605bcae, 0xd4273597, 0x09629f2f,
  0xe6264403, 0x3b63eebb, 0x59416782, 0x8404cd3a,
  0x9d0475f0, 0x4041df48, 0x22635671, 0xff26fcc9,
  0x2e238253, 0xf36628eb, 0x9144a1d2, 0x4c010b6a,
  0x5501b3a0, 0x88441918, 0xea669021, 0x37233a99,
  0xd867e1b5, 0x05224b0d, 0x6700c234, 0xba45688c,
  0xa345d046, 0x7e007afe, 0x1c22f3c7, 0xc167597f,
  0xc747336e, 0x1a0299d6, 0x782010ef, 0xa565ba57,
  0xbc65029d, 0x6120a825, 0x0302211c, 0xde478ba4,
  0x31035088, 0xec46fa30, 0x8e647309, 0x5321d9b1,
  0x4a21617b, 0x9764cbc3, 0xf54642fa, 0x2803e842
};

// Used to fetch a naturally-aligned 32-bit word in little endian byte-order
static inline uint32_t LE_LOAD32(const uint8_t *p) {
  return DecodeFixed32(reinterpret_cast<const char*>(p));
}

#if defined(HAVE_SSE42) && (defined(__LP64__) || defined(_WIN64))
static inline uint64_t LE_LOAD64(const uint8_t *p) {
  return DecodeFixed64(reinterpret_cast<const char*>(p));
}
#endif

static inline void Slow_CRC32(uint64_t* l, uint8_t const **p) {
  uint32_t c = static_cast<uint32_t>(*l ^ LE_LOAD32(*p));
  *p += 4;
  *l = table3_[c & 0xff] ^
  table2_[(c >> 8) & 0xff] ^
  table1_[(c >> 16) & 0xff] ^
  table0_[c >> 24];
  // DO it twice.
  c = static_cast<uint32_t>(*l ^ LE_LOAD32(*p));
  *p += 4;
  *l = table3_[c & 0xff] ^
  table2_[(c >> 8) & 0xff] ^
  table1_[(c >> 16) & 0xff] ^
  table0_[c >> 24];
}

static inline void Fast_CRC32(uint64_t* l, uint8_t const **p) {
#ifndef HAVE_SSE42
  Slow_CRC32(l, p);
#elif defined(__LP64__) || defined(_WIN64)
  *l = _mm_crc32_u64(*l, LE_LOAD64(*p));
  *p += 8;
#else
  *l = _mm_crc32_u32(static_cast<unsigned int>(*l), LE_LOAD32(*p));
  *p += 4;
  *l = _mm_crc32_u32(static_cast<unsigned int>(*l), LE_LOAD32(*p));
  *p += 4;
#endif
}

template<void (*CRC32)(uint64_t*, uint8_t const**)>
uint32_t ExtendImpl(uint32_t crc, const char* buf, size_t size) {

  const uint8_t *p = reinterpret_cast<const uint8_t *>(buf);
  const uint8_t *e = p + size;
  uint64_t l = crc ^ 0xffffffffu;

// Align n to (1 << m) byte boundary
#define ALIGN(n, m)     ((n + ((1 << m) - 1)) & ~((1 << m) - 1))

#define STEP1 do {                              \
    int c = (l & 0xff) ^ *p++;                  \
    l = table0_[c] ^ (l >> 8);                  \
} while (0)


  // Point x at first 16-byte aligned byte in string.  This might be
  // just past the end of the string.
  const uintptr_t pval = reinterpret_cast<uintptr_t>(p);
  const uint8_t* x = reinterpret_cast<const uint8_t*>(ALIGN(pval, 4));
  if (x <= e) {
    // Process bytes until finished or p is 16-byte aligned
    while (p != x) {
      STEP1;
    }
  }
  // Process bytes 16 at a time
  while ((e-p) >= 16) {
    CRC32(&l, &p);
    CRC32(&l, &p);
  }
  // Process bytes 8 at a time
  while ((e-p) >= 8) {
    CRC32(&l, &p);
  }
  // Process the last few bytes
  while (p != e) {
    STEP1;
  }
#undef STEP1
#undef ALIGN
  return static_cast<uint32_t>(l ^ 0xffffffffu);
}

// Detect if SS42 or not.
#ifndef HAVE_POWER8

static bool isSSE42() {
#ifndef HAVE_SSE42
  return false;
#elif defined(__GNUC__) && defined(__x86_64__) && !defined(IOS_CROSS_COMPILE)
  uint32_t c_;
  __asm__("cpuid" : "=c"(c_) : "a"(1) : "ebx", "edx");
  return c_ & (1U << 20);  // copied from CpuId.h in Folly. Test SSE42
#elif defined(_WIN64)
  int info[4];
  __cpuidex(info, 0x00000001, 0);
  return (info[2] & ((int)1 << 20)) != 0;
#else
  return false;
#endif
}

static bool isPCLMULQDQ() {
#ifndef HAVE_SSE42
// in build_detect_platform we set this macro when both SSE42 and PCLMULQDQ are
// supported by compiler
  return false;
#elif defined(__GNUC__) && defined(__x86_64__) && !defined(IOS_CROSS_COMPILE)
  uint32_t c_;
  __asm__("cpuid" : "=c"(c_) : "a"(1) : "ebx", "edx");
  return c_ & (1U << 1);  // PCLMULQDQ is in bit 1 (not bit 0)
#elif defined(_WIN64)
  int info[4];
  __cpuidex(info, 0x00000001, 0);
  return (info[2] & ((int)1 << 1)) != 0;
#else
  return false;
#endif
}

#endif  // HAVE_POWER8

typedef uint32_t (*Function)(uint32_t, const char*, size_t);

#if defined(HAVE_POWER8) && defined(HAS_ALTIVEC)
uint32_t ExtendPPCImpl(uint32_t crc, const char *buf, size_t size) {
  return crc32c_ppc(crc, (const unsigned char *)buf, size);
}

#if __linux__
static int arch_ppc_probe(void) {
  arch_ppc_crc32 = 0;

#if defined(__powerpc64__)
  if (getauxval(AT_HWCAP2) & PPC_FEATURE2_VEC_CRYPTO) arch_ppc_crc32 = 1;
#endif /* __powerpc64__ */

  return arch_ppc_crc32;
}
#endif  // __linux__

static bool isAltiVec() {
  if (arch_ppc_probe()) {
    return true;
  } else {
    return false;
  }
}
#endif


std::string IsFastCrc32Supported() {
  bool has_fast_crc = false;
  std::string fast_zero_msg;
  std::string arch;
#ifdef HAVE_POWER8
#ifdef HAS_ALTIVEC
  if (arch_ppc_probe()) {
    has_fast_crc = true;
    arch = "PPC";
  }
#else
  has_fast_crc = false;
  arch = "PPC";
#endif
#else
  has_fast_crc = isSSE42();
  arch = "x86";
#endif
  if (has_fast_crc) {
    fast_zero_msg.append("Supported on " + arch);
  }
  else {
    fast_zero_msg.append("Not supported on " + arch);
  }
  return fast_zero_msg;
}


/*
 * Copyright 2016 Ferry Toth, Exalon Delft BV, The Netherlands
 *  This software is provided 'as-is', without any express or implied
 * warranty.  In no event will the author be held liable for any damages
 * arising from the use of this software.
 *  Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *  1. The origin of this software must not be misrepresented; you must not
 *   claim that you wrote the original software. If you use this software
 *   in a product, an acknowledgment in the product documentation would be
 *   appreciated but is not required.
 * 2. Altered source versions must be plainly marked as such, and must not be
 *   misrepresented as being the original software.
 * 3. This notice may not be removed or altered from any source distribution.
 *  Ferry Toth
 * ftoth@exalondelft.nl
 *
 * https://github.com/htot/crc32c
 *
 * Modified by Facebook
 *
 * Original intel whitepaper:
 * "Fast CRC Computation for iSCSI Polynomial Using CRC32 Instruction"
 * https://www.intel.com/content/dam/www/public/us/en/documents/white-papers/crc-iscsi-polynomial-crc32-instruction-paper.pdf
 *
 * This version is from the folly library, created by Dave Watson <davejwatson@fb.com>
 *
*/
#if defined HAVE_SSE42 && defined HAVE_PCLMUL

#define CRCtriplet(crc, buf, offset)                  \
  crc##0 = _mm_crc32_u64(crc##0, *(buf##0 + offset)); \
  crc##1 = _mm_crc32_u64(crc##1, *(buf##1 + offset)); \
  crc##2 = _mm_crc32_u64(crc##2, *(buf##2 + offset));

#define CRCduplet(crc, buf, offset)                   \
  crc##0 = _mm_crc32_u64(crc##0, *(buf##0 + offset)); \
  crc##1 = _mm_crc32_u64(crc##1, *(buf##1 + offset));

#define CRCsinglet(crc, buf, offset)                    \
  crc = _mm_crc32_u64(crc, *(uint64_t*)(buf + offset));


// Numbers taken directly from intel whitepaper.
// clang-format off
const uint64_t clmul_constants[] = {
    0x14cd00bd6, 0x105ec76f0, 0x0ba4fc28e, 0x14cd00bd6,
    0x1d82c63da, 0x0f20c0dfe, 0x09e4addf8, 0x0ba4fc28e,
    0x039d3b296, 0x1384aa63a, 0x102f9b8a2, 0x1d82c63da,
    0x14237f5e6, 0x01c291d04, 0x00d3b6092, 0x09e4addf8,
    0x0c96cfdc0, 0x0740eef02, 0x18266e456, 0x039d3b296,
    0x0daece73e, 0x0083a6eec, 0x0ab7aff2a, 0x102f9b8a2,
    0x1248ea574, 0x1c1733996, 0x083348832, 0x14237f5e6,
    0x12c743124, 0x02ad91c30, 0x0b9e02b86, 0x00d3b6092,
    0x018b33a4e, 0x06992cea2, 0x1b331e26a, 0x0c96cfdc0,
    0x17d35ba46, 0x07e908048, 0x1bf2e8b8a, 0x18266e456,
    0x1a3e0968a, 0x11ed1f9d8, 0x0ce7f39f4, 0x0daece73e,
    0x061d82e56, 0x0f1d0f55e, 0x0d270f1a2, 0x0ab7aff2a,
    0x1c3f5f66c, 0x0a87ab8a8, 0x12ed0daac, 0x1248ea574,
    0x065863b64, 0x08462d800, 0x11eef4f8e, 0x083348832,
    0x1ee54f54c, 0x071d111a8, 0x0b3e32c28, 0x12c743124,
    0x0064f7f26, 0x0ffd852c6, 0x0dd7e3b0c, 0x0b9e02b86,
    0x0f285651c, 0x0dcb17aa4, 0x010746f3c, 0x018b33a4e,
    0x1c24afea4, 0x0f37c5aee, 0x0271d9844, 0x1b331e26a,
    0x08e766a0c, 0x06051d5a2, 0x093a5f730, 0x17d35ba46,
    0x06cb08e5c, 0x11d5ca20e, 0x06b749fb2, 0x1bf2e8b8a,
    0x1167f94f2, 0x021f3d99c, 0x0cec3662e, 0x1a3e0968a,
    0x19329634a, 0x08f158014, 0x0e6fc4e6a, 0x0ce7f39f4,
    0x08227bb8a, 0x1a5e82106, 0x0b0cd4768, 0x061d82e56,
    0x13c2b89c4, 0x188815ab2, 0x0d7a4825c, 0x0d270f1a2,
    0x10f5ff2ba, 0x105405f3e, 0x00167d312, 0x1c3f5f66c,
    0x0f6076544, 0x0e9adf796, 0x026f6a60a, 0x12ed0daac,
    0x1a2adb74e, 0x096638b34, 0x19d34af3a, 0x065863b64,
    0x049c3cc9c, 0x1e50585a0, 0x068bce87a, 0x11eef4f8e,
    0x1524fa6c6, 0x19f1c69dc, 0x16cba8aca, 0x1ee54f54c,
    0x042d98888, 0x12913343e, 0x1329d9f7e, 0x0b3e32c28,
    0x1b1c69528, 0x088f25a3a, 0x02178513a, 0x0064f7f26,
    0x0e0ac139e, 0x04e36f0b0, 0x0170076fa, 0x0dd7e3b0c,
    0x141a1a2e2, 0x0bd6f81f8, 0x16ad828b4, 0x0f285651c,
    0x041d17b64, 0x19425cbba, 0x1fae1cc66, 0x010746f3c,
    0x1a75b4b00, 0x18db37e8a, 0x0f872e54c, 0x1c24afea4,
    0x01e41e9fc, 0x04c144932, 0x086d8e4d2, 0x0271d9844,
    0x160f7af7a, 0x052148f02, 0x05bb8f1bc, 0x08e766a0c,
    0x0a90fd27a, 0x0a3c6f37a, 0x0b3af077a, 0x093a5f730,
    0x04984d782, 0x1d22c238e, 0x0ca6ef3ac, 0x06cb08e5c,
    0x0234e0b26, 0x063ded06a, 0x1d88abd4a, 0x06b749fb2,
    0x04597456a, 0x04d56973c, 0x0e9e28eb4, 0x1167f94f2,
    0x07b3ff57a, 0x19385bf2e, 0x0c9c8b782, 0x0cec3662e,
    0x13a9cba9e, 0x0e417f38a, 0x093e106a4, 0x19329634a,
    0x167001a9c, 0x14e727980, 0x1ddffc5d4, 0x0e6fc4e6a,
    0x00df04680, 0x0d104b8fc, 0x02342001e, 0x08227bb8a,
    0x00a2a8d7e, 0x05b397730, 0x168763fa6, 0x0b0cd4768,
    0x1ed5a407a, 0x0e78eb416, 0x0d2c3ed1a, 0x13c2b89c4,
    0x0995a5724, 0x1641378f0, 0x19b1afbc4, 0x0d7a4825c,
    0x109ffedc0, 0x08d96551c, 0x0f2271e60, 0x10f5ff2ba,
    0x00b0bf8ca, 0x00bf80dd2, 0x123888b7a, 0x00167d312,
    0x1e888f7dc, 0x18dcddd1c, 0x002ee03b2, 0x0f6076544,
    0x183e8d8fe, 0x06a45d2b2, 0x133d7a042, 0x026f6a60a,
    0x116b0f50c, 0x1dd3e10e8, 0x05fabe670, 0x1a2adb74e,
    0x130004488, 0x0de87806c, 0x000bcf5f6, 0x19d34af3a,
    0x18f0c7078, 0x014338754, 0x017f27698, 0x049c3cc9c,
    0x058ca5f00, 0x15e3e77ee, 0x1af900c24, 0x068bce87a,
    0x0b5cfca28, 0x0dd07448e, 0x0ded288f8, 0x1524fa6c6,
    0x059f229bc, 0x1d8048348, 0x06d390dec, 0x16cba8aca,
    0x037170390, 0x0a3e3e02c, 0x06353c1cc, 0x042d98888,
    0x0c4584f5c, 0x0d73c7bea, 0x1f16a3418, 0x1329d9f7e,
    0x0531377e2, 0x185137662, 0x1d8d9ca7c, 0x1b1c69528,
    0x0b25b29f2, 0x18a08b5bc, 0x19fb2a8b0, 0x02178513a,
    0x1a08fe6ac, 0x1da758ae0, 0x045cddf4e, 0x0e0ac139e,
    0x1a91647f2, 0x169cf9eb0, 0x1a0f717c4, 0x0170076fa,
};

// Compute the crc32c value for buffer smaller than 8
#ifdef ROCKSDB_UBSAN_RUN
#if defined(__clang__)
__attribute__((__no_sanitize__("alignment")))
#elif defined(__GNUC__)
__attribute__((__no_sanitize_undefined__))
#endif
#endif
inline void align_to_8(
    size_t len,
    uint64_t& crc0, // crc so far, updated on return
    const unsigned char*& next) { // next data pointer, updated on return
  uint32_t crc32bit = static_cast<uint32_t>(crc0);
  if (len & 0x04) {
    crc32bit = _mm_crc32_u32(crc32bit, *(uint32_t*)next);
    next += sizeof(uint32_t);
  }
  if (len & 0x02) {
    crc32bit = _mm_crc32_u16(crc32bit, *(uint16_t*)next);
    next += sizeof(uint16_t);
  }
  if (len & 0x01) {
    crc32bit = _mm_crc32_u8(crc32bit, *(next));
    next++;
  }
  crc0 = crc32bit;
}

//
// CombineCRC performs pclmulqdq multiplication of 2 partial CRC's and a well
// chosen constant and xor's these with the remaining CRC.
//
inline uint64_t CombineCRC(
    size_t block_size,
    uint64_t crc0,
    uint64_t crc1,
    uint64_t crc2,
    const uint64_t* next2) {
  const auto multiplier =
      *(reinterpret_cast<const __m128i*>(clmul_constants) + block_size - 1);
  const auto crc0_xmm = _mm_set_epi64x(0, crc0);
  const auto res0 = _mm_clmulepi64_si128(crc0_xmm, multiplier, 0x00);
  const auto crc1_xmm = _mm_set_epi64x(0, crc1);
  const auto res1 = _mm_clmulepi64_si128(crc1_xmm, multiplier, 0x10);
  const auto res = _mm_xor_si128(res0, res1);
  crc0 = _mm_cvtsi128_si64(res);
  crc0 = crc0 ^ *((uint64_t*)next2 - 1);
  crc2 = _mm_crc32_u64(crc2, crc0);
  return crc2;
}

// Compute CRC-32C using the Intel hardware instruction.
#ifdef ROCKSDB_UBSAN_RUN
#if defined(__clang__)
__attribute__((__no_sanitize__("alignment")))
#elif defined(__GNUC__)
__attribute__((__no_sanitize_undefined__))
#endif
#endif
uint32_t crc32c_3way(uint32_t crc, const char* buf, size_t len) {
  const unsigned char* next = (const unsigned char*)buf;
  uint64_t count;
  uint64_t crc0, crc1, crc2;
  crc0 = crc ^ 0xffffffffu;


  if (len >= 8) {
    // if len > 216 then align and use triplets
    if (len > 216) {
      {
        // Work on the bytes (< 8) before the first 8-byte alignment addr starts
        uint64_t align_bytes = (8 - (uintptr_t)next) & 7;
        len -= align_bytes;
        align_to_8(align_bytes, crc0, next);
      }

      // Now work on the remaining blocks
      count = len / 24; // number of triplets
      len %= 24; // bytes remaining
      uint64_t n = count >> 7; // #blocks = first block + full blocks
      uint64_t block_size = count & 127;
      if (block_size == 0) {
        block_size = 128;
      } else {
        n++;
      }
      // points to the first byte of the next block
      const uint64_t* next0 = (uint64_t*)next + block_size;
      const uint64_t* next1 = next0 + block_size;
      const uint64_t* next2 = next1 + block_size;

      crc1 = crc2 = 0;
      // Use Duff's device, a for() loop inside a switch()
      // statement. This needs to execute at least once, round len
      // down to nearest triplet multiple
      switch (block_size) {
        case 128:
          do {
            // jumps here for a full block of len 128
            CRCtriplet(crc, next, -128);
	    FALLTHROUGH_INTENDED;
            case 127:
              // jumps here or below for the first block smaller
              CRCtriplet(crc, next, -127);
	      FALLTHROUGH_INTENDED;
            case 126:
              CRCtriplet(crc, next, -126); // than 128
	      FALLTHROUGH_INTENDED;
            case 125:
              CRCtriplet(crc, next, -125);
	      FALLTHROUGH_INTENDED;
            case 124:
              CRCtriplet(crc, next, -124);
	      FALLTHROUGH_INTENDED;
            case 123:
              CRCtriplet(crc, next, -123);
	      FALLTHROUGH_INTENDED;
            case 122:
              CRCtriplet(crc, next, -122);
	      FALLTHROUGH_INTENDED;
            case 121:
              CRCtriplet(crc, next, -121);
	      FALLTHROUGH_INTENDED;
            case 120:
              CRCtriplet(crc, next, -120);
              FALLTHROUGH_INTENDED;
            case 119:
              CRCtriplet(crc, next, -119);
              FALLTHROUGH_INTENDED;
            case 118:
              CRCtriplet(crc, next, -118);
              FALLTHROUGH_INTENDED;
            case 117:
              CRCtriplet(crc, next, -117);
              FALLTHROUGH_INTENDED;
            case 116:
              CRCtriplet(crc, next, -116);
              FALLTHROUGH_INTENDED;
            case 115:
              CRCtriplet(crc, next, -115);
              FALLTHROUGH_INTENDED;
            case 114:
              CRCtriplet(crc, next, -114);
              FALLTHROUGH_INTENDED;
            case 113:
              CRCtriplet(crc, next, -113);
              FALLTHROUGH_INTENDED;
            case 112:
              CRCtriplet(crc, next, -112);
              FALLTHROUGH_INTENDED;
            case 111:
              CRCtriplet(crc, next, -111);
              FALLTHROUGH_INTENDED;
            case 110:
              CRCtriplet(crc, next, -110);
              FALLTHROUGH_INTENDED;
            case 109:
              CRCtriplet(crc, next, -109);
              FALLTHROUGH_INTENDED;
            case 108:
              CRCtriplet(crc, next, -108);
              FALLTHROUGH_INTENDED;
            case 107:
              CRCtriplet(crc, next, -107);
              FALLTHROUGH_INTENDED;
            case 106:
              CRCtriplet(crc, next, -106);
              FALLTHROUGH_INTENDED;
            case 105:
              CRCtriplet(crc, next, -105);
              FALLTHROUGH_INTENDED;
            case 104:
              CRCtriplet(crc, next, -104);
              FALLTHROUGH_INTENDED;
            case 103:
              CRCtriplet(crc, next, -103);
              FALLTHROUGH_INTENDED;
            case 102:
              CRCtriplet(crc, next, -102);
              FALLTHROUGH_INTENDED;
            case 101:
              CRCtriplet(crc, next, -101);
              FALLTHROUGH_INTENDED;
            case 100:
              CRCtriplet(crc, next, -100);
              FALLTHROUGH_INTENDED;
            case 99:
              CRCtriplet(crc, next, -99);
              FALLTHROUGH_INTENDED;
            case 98:
              CRCtriplet(crc, next, -98);
              FALLTHROUGH_INTENDED;
            case 97:
              CRCtriplet(crc, next, -97);
              FALLTHROUGH_INTENDED;
            case 96:
              CRCtriplet(crc, next, -96);
              FALLTHROUGH_INTENDED;
            case 95:
              CRCtriplet(crc, next, -95);
              FALLTHROUGH_INTENDED;
            case 94:
              CRCtriplet(crc, next, -94);
              FALLTHROUGH_INTENDED;
            case 93:
              CRCtriplet(crc, next, -93);
              FALLTHROUGH_INTENDED;
            case 92:
              CRCtriplet(crc, next, -92);
              FALLTHROUGH_INTENDED;
            case 91:
              CRCtriplet(crc, next, -91);
              FALLTHROUGH_INTENDED;
            case 90:
              CRCtriplet(crc, next, -90);
              FALLTHROUGH_INTENDED;
            case 89:
              CRCtriplet(crc, next, -89);
              FALLTHROUGH_INTENDED;
            case 88:
              CRCtriplet(crc, next, -88);
              FALLTHROUGH_INTENDED;
            case 87:
              CRCtriplet(crc, next, -87);
              FALLTHROUGH_INTENDED;
            case 86:
              CRCtriplet(crc, next, -86);
              FALLTHROUGH_INTENDED;
            case 85:
              CRCtriplet(crc, next, -85);
              FALLTHROUGH_INTENDED;
            case 84:
              CRCtriplet(crc, next, -84);
              FALLTHROUGH_INTENDED;
            case 83:
              CRCtriplet(crc, next, -83);
              FALLTHROUGH_INTENDED;
            case 82:
              CRCtriplet(crc, next, -82);
              FALLTHROUGH_INTENDED;
            case 81:
              CRCtriplet(crc, next, -81);
              FALLTHROUGH_INTENDED;
            case 80:
              CRCtriplet(crc, next, -80);
              FALLTHROUGH_INTENDED;
            case 79:
              CRCtriplet(crc, next, -79);
              FALLTHROUGH_INTENDED;
            case 78:
              CRCtriplet(crc, next, -78);
              FALLTHROUGH_INTENDED;
            case 77:
              CRCtriplet(crc, next, -77);
              FALLTHROUGH_INTENDED;
            case 76:
              CRCtriplet(crc, next, -76);
              FALLTHROUGH_INTENDED;
            case 75:
              CRCtriplet(crc, next, -75);
              FALLTHROUGH_INTENDED;
            case 74:
              CRCtriplet(crc, next, -74);
              FALLTHROUGH_INTENDED;
            case 73:
              CRCtriplet(crc, next, -73);
              FALLTHROUGH_INTENDED;
            case 72:
              CRCtriplet(crc, next, -72);
              FALLTHROUGH_INTENDED;
            case 71:
              CRCtriplet(crc, next, -71);
              FALLTHROUGH_INTENDED;
            case 70:
              CRCtriplet(crc, next, -70);
              FALLTHROUGH_INTENDED;
            case 69:
              CRCtriplet(crc, next, -69);
              FALLTHROUGH_INTENDED;
            case 68:
              CRCtriplet(crc, next, -68);
              FALLTHROUGH_INTENDED;
            case 67:
              CRCtriplet(crc, next, -67);
              FALLTHROUGH_INTENDED;
            case 66:
              CRCtriplet(crc, next, -66);
              FALLTHROUGH_INTENDED;
            case 65:
              CRCtriplet(crc, next, -65);
              FALLTHROUGH_INTENDED;
            case 64:
              CRCtriplet(crc, next, -64);
              FALLTHROUGH_INTENDED;
            case 63:
              CRCtriplet(crc, next, -63);
              FALLTHROUGH_INTENDED;
            case 62:
              CRCtriplet(crc, next, -62);
              FALLTHROUGH_INTENDED;
            case 61:
              CRCtriplet(crc, next, -61);
              FALLTHROUGH_INTENDED;
            case 60:
              CRCtriplet(crc, next, -60);
              FALLTHROUGH_INTENDED;
            case 59:
              CRCtriplet(crc, next, -59);
              FALLTHROUGH_INTENDED;
            case 58:
              CRCtriplet(crc, next, -58);
              FALLTHROUGH_INTENDED;
            case 57:
              CRCtriplet(crc, next, -57);
              FALLTHROUGH_INTENDED;
            case 56:
              CRCtriplet(crc, next, -56);
              FALLTHROUGH_INTENDED;
            case 55:
              CRCtriplet(crc, next, -55);
              FALLTHROUGH_INTENDED;
            case 54:
              CRCtriplet(crc, next, -54);
              FALLTHROUGH_INTENDED;
            case 53:
              CRCtriplet(crc, next, -53);
              FALLTHROUGH_INTENDED;
            case 52:
              CRCtriplet(crc, next, -52);
              FALLTHROUGH_INTENDED;
            case 51:
              CRCtriplet(crc, next, -51);
              FALLTHROUGH_INTENDED;
            case 50:
              CRCtriplet(crc, next, -50);
              FALLTHROUGH_INTENDED;
            case 49:
              CRCtriplet(crc, next, -49);
              FALLTHROUGH_INTENDED;
            case 48:
              CRCtriplet(crc, next, -48);
              FALLTHROUGH_INTENDED;
            case 47:
              CRCtriplet(crc, next, -47);
              FALLTHROUGH_INTENDED;
            case 46:
              CRCtriplet(crc, next, -46);
              FALLTHROUGH_INTENDED;
            case 45:
              CRCtriplet(crc, next, -45);
              FALLTHROUGH_INTENDED;
            case 44:
              CRCtriplet(crc, next, -44);
              FALLTHROUGH_INTENDED;
            case 43:
              CRCtriplet(crc, next, -43);
              FALLTHROUGH_INTENDED;
            case 42:
              CRCtriplet(crc, next, -42);
              FALLTHROUGH_INTENDED;
            case 41:
              CRCtriplet(crc, next, -41);
              FALLTHROUGH_INTENDED;
            case 40:
              CRCtriplet(crc, next, -40);
              FALLTHROUGH_INTENDED;
            case 39:
              CRCtriplet(crc, next, -39);
              FALLTHROUGH_INTENDED;
            case 38:
              CRCtriplet(crc, next, -38);
              FALLTHROUGH_INTENDED;
            case 37:
              CRCtriplet(crc, next, -37);
              FALLTHROUGH_INTENDED;
            case 36:
              CRCtriplet(crc, next, -36);
              FALLTHROUGH_INTENDED;
            case 35:
              CRCtriplet(crc, next, -35);
              FALLTHROUGH_INTENDED;
            case 34:
              CRCtriplet(crc, next, -34);
              FALLTHROUGH_INTENDED;
            case 33:
              CRCtriplet(crc, next, -33);
              FALLTHROUGH_INTENDED;
            case 32:
              CRCtriplet(crc, next, -32);
              FALLTHROUGH_INTENDED;
            case 31:
              CRCtriplet(crc, next, -31);
              FALLTHROUGH_INTENDED;
            case 30:
              CRCtriplet(crc, next, -30);
              FALLTHROUGH_INTENDED;
            case 29:
              CRCtriplet(crc, next, -29);
              FALLTHROUGH_INTENDED;
            case 28:
              CRCtriplet(crc, next, -28);
              FALLTHROUGH_INTENDED;
            case 27:
              CRCtriplet(crc, next, -27);
              FALLTHROUGH_INTENDED;
            case 26:
              CRCtriplet(crc, next, -26);
              FALLTHROUGH_INTENDED;
            case 25:
              CRCtriplet(crc, next, -25);
              FALLTHROUGH_INTENDED;
            case 24:
              CRCtriplet(crc, next, -24);
              FALLTHROUGH_INTENDED;
            case 23:
              CRCtriplet(crc, next, -23);
              FALLTHROUGH_INTENDED;
            case 22:
              CRCtriplet(crc, next, -22);
              FALLTHROUGH_INTENDED;
            case 21:
              CRCtriplet(crc, next, -21);
              FALLTHROUGH_INTENDED;
            case 20:
              CRCtriplet(crc, next, -20);
              FALLTHROUGH_INTENDED;
            case 19:
              CRCtriplet(crc, next, -19);
              FALLTHROUGH_INTENDED;
            case 18:
              CRCtriplet(crc, next, -18);
              FALLTHROUGH_INTENDED;
            case 17:
              CRCtriplet(crc, next, -17);
              FALLTHROUGH_INTENDED;
            case 16:
              CRCtriplet(crc, next, -16);
              FALLTHROUGH_INTENDED;
            case 15:
              CRCtriplet(crc, next, -15);
              FALLTHROUGH_INTENDED;
            case 14:
              CRCtriplet(crc, next, -14);
              FALLTHROUGH_INTENDED;
            case 13:
              CRCtriplet(crc, next, -13);
              FALLTHROUGH_INTENDED;
            case 12:
              CRCtriplet(crc, next, -12);
              FALLTHROUGH_INTENDED;
            case 11:
              CRCtriplet(crc, next, -11);
              FALLTHROUGH_INTENDED;
            case 10:
              CRCtriplet(crc, next, -10);
              FALLTHROUGH_INTENDED;
            case 9:
              CRCtriplet(crc, next, -9);
              FALLTHROUGH_INTENDED;
            case 8:
              CRCtriplet(crc, next, -8);
              FALLTHROUGH_INTENDED;
            case 7:
              CRCtriplet(crc, next, -7);
              FALLTHROUGH_INTENDED;
            case 6:
              CRCtriplet(crc, next, -6);
              FALLTHROUGH_INTENDED;
            case 5:
              CRCtriplet(crc, next, -5);
              FALLTHROUGH_INTENDED;
            case 4:
              CRCtriplet(crc, next, -4);
              FALLTHROUGH_INTENDED;
            case 3:
              CRCtriplet(crc, next, -3);
              FALLTHROUGH_INTENDED;
            case 2:
              CRCtriplet(crc, next, -2);
              FALLTHROUGH_INTENDED;
            case 1:
              CRCduplet(crc, next, -1); // the final triplet is actually only 2
              //{ CombineCRC(); }
              crc0 = CombineCRC(block_size, crc0, crc1, crc2, next2);
              if (--n > 0) {
                crc1 = crc2 = 0;
                block_size = 128;
                // points to the first byte of the next block
                next0 = next2 + 128;
                next1 = next0 + 128; // from here on all blocks are 128 long
                next2 = next1 + 128;
              }
              FALLTHROUGH_INTENDED;
            case 0:;
          } while (n > 0);
      }
      next = (const unsigned char*)next2;
    }
    uint64_t count2 = len >> 3; // 216 of less bytes is 27 or less singlets
    len = len & 7;
    next += (count2 * 8);
    switch (count2) {
      case 27:
        CRCsinglet(crc0, next, -27 * 8);
        FALLTHROUGH_INTENDED;
      case 26:
        CRCsinglet(crc0, next, -26 * 8);
        FALLTHROUGH_INTENDED;
      case 25:
        CRCsinglet(crc0, next, -25 * 8);
        FALLTHROUGH_INTENDED;
      case 24:
        CRCsinglet(crc0, next, -24 * 8);
        FALLTHROUGH_INTENDED;
      case 23:
        CRCsinglet(crc0, next, -23 * 8);
        FALLTHROUGH_INTENDED;
      case 22:
        CRCsinglet(crc0, next, -22 * 8);
        FALLTHROUGH_INTENDED;
      case 21:
        CRCsinglet(crc0, next, -21 * 8);
        FALLTHROUGH_INTENDED;
      case 20:
        CRCsinglet(crc0, next, -20 * 8);
        FALLTHROUGH_INTENDED;
      case 19:
        CRCsinglet(crc0, next, -19 * 8);
        FALLTHROUGH_INTENDED;
      case 18:
        CRCsinglet(crc0, next, -18 * 8);
        FALLTHROUGH_INTENDED;
      case 17:
        CRCsinglet(crc0, next, -17 * 8);
        FALLTHROUGH_INTENDED;
      case 16:
        CRCsinglet(crc0, next, -16 * 8);
        FALLTHROUGH_INTENDED;
      case 15:
        CRCsinglet(crc0, next, -15 * 8);
        FALLTHROUGH_INTENDED;
      case 14:
        CRCsinglet(crc0, next, -14 * 8);
        FALLTHROUGH_INTENDED;
      case 13:
        CRCsinglet(crc0, next, -13 * 8);
        FALLTHROUGH_INTENDED;
      case 12:
        CRCsinglet(crc0, next, -12 * 8);
        FALLTHROUGH_INTENDED;
      case 11:
        CRCsinglet(crc0, next, -11 * 8);
        FALLTHROUGH_INTENDED;
      case 10:
        CRCsinglet(crc0, next, -10 * 8);
        FALLTHROUGH_INTENDED;
      case 9:
        CRCsinglet(crc0, next, -9 * 8);
        FALLTHROUGH_INTENDED;
      case 8:
        CRCsinglet(crc0, next, -8 * 8);
        FALLTHROUGH_INTENDED;
      case 7:
        CRCsinglet(crc0, next, -7 * 8);
        FALLTHROUGH_INTENDED;
      case 6:
        CRCsinglet(crc0, next, -6 * 8);
        FALLTHROUGH_INTENDED;
      case 5:
        CRCsinglet(crc0, next, -5 * 8);
        FALLTHROUGH_INTENDED;
      case 4:
        CRCsinglet(crc0, next, -4 * 8);
        FALLTHROUGH_INTENDED;
      case 3:
        CRCsinglet(crc0, next, -3 * 8);
        FALLTHROUGH_INTENDED;
      case 2:
        CRCsinglet(crc0, next, -2 * 8);
        FALLTHROUGH_INTENDED;
      case 1:
        CRCsinglet(crc0, next, -1 * 8);
        FALLTHROUGH_INTENDED;
      case 0:;
    }
  }
  {
    align_to_8(len, crc0, next);
    return (uint32_t)crc0 ^ 0xffffffffu;
  }
}

#endif //HAVE_SSE42 && HAVE_PCLMUL

static inline Function Choose_Extend() {
#ifndef HAVE_POWER8
  if (isSSE42()) {
    if (isPCLMULQDQ()) {
#if defined HAVE_SSE42  && defined HAVE_PCLMUL && !defined NO_THREEWAY_CRC32C
      return crc32c_3way;
#else
    return ExtendImpl<Fast_CRC32>; // Fast_CRC32 will check HAVE_SSE42 itself
#endif
    }
    else {  // no runtime PCLMULQDQ support but has SSE42 support
      return ExtendImpl<Fast_CRC32>;
    }
  } // end of isSSE42()
  else {
    return ExtendImpl<Slow_CRC32>;
  }
#else  //HAVE_POWER8
  return isAltiVec() ? ExtendPPCImpl : ExtendImpl<Slow_CRC32>;
#endif
}

static Function ChosenExtend = Choose_Extend();
uint32_t Extend(uint32_t crc, const char* buf, size_t size) {
  return ChosenExtend(crc, buf, size);
}


}  // namespace crc32c
}  // namespace rocksdb
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