forked from OSchip/llvm-project
69 lines
2.0 KiB
C++
69 lines
2.0 KiB
C++
//===--- CRC.cpp - Cyclic Redundancy Check implementation -----------------===//
|
|
//
|
|
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
|
|
// See https://llvm.org/LICENSE.txt for license information.
|
|
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file implements llvm::crc32 function.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "llvm/Support/CRC.h"
|
|
#include "llvm/Config/config.h"
|
|
#include "llvm/ADT/StringRef.h"
|
|
#include "llvm/Support/Threading.h"
|
|
#include <array>
|
|
|
|
using namespace llvm;
|
|
|
|
#if LLVM_ENABLE_ZLIB == 0 || !HAVE_ZLIB_H
|
|
using CRC32Table = std::array<uint32_t, 256>;
|
|
|
|
static void initCRC32Table(CRC32Table *Tbl) {
|
|
auto Shuffle = [](uint32_t V) {
|
|
return (V & 1) ? (V >> 1) ^ 0xEDB88320U : V >> 1;
|
|
};
|
|
|
|
for (size_t I = 0; I < Tbl->size(); ++I) {
|
|
uint32_t V = Shuffle(I);
|
|
V = Shuffle(V);
|
|
V = Shuffle(V);
|
|
V = Shuffle(V);
|
|
V = Shuffle(V);
|
|
V = Shuffle(V);
|
|
V = Shuffle(V);
|
|
(*Tbl)[I] = Shuffle(V);
|
|
}
|
|
}
|
|
|
|
uint32_t llvm::crc32(uint32_t CRC, StringRef S) {
|
|
static llvm::once_flag InitFlag;
|
|
static CRC32Table Tbl;
|
|
llvm::call_once(InitFlag, initCRC32Table, &Tbl);
|
|
|
|
const uint8_t *P = reinterpret_cast<const uint8_t *>(S.data());
|
|
size_t Len = S.size();
|
|
CRC ^= 0xFFFFFFFFU;
|
|
for (; Len >= 8; Len -= 8) {
|
|
CRC = Tbl[(CRC ^ *P++) & 0xFF] ^ (CRC >> 8);
|
|
CRC = Tbl[(CRC ^ *P++) & 0xFF] ^ (CRC >> 8);
|
|
CRC = Tbl[(CRC ^ *P++) & 0xFF] ^ (CRC >> 8);
|
|
CRC = Tbl[(CRC ^ *P++) & 0xFF] ^ (CRC >> 8);
|
|
CRC = Tbl[(CRC ^ *P++) & 0xFF] ^ (CRC >> 8);
|
|
CRC = Tbl[(CRC ^ *P++) & 0xFF] ^ (CRC >> 8);
|
|
CRC = Tbl[(CRC ^ *P++) & 0xFF] ^ (CRC >> 8);
|
|
CRC = Tbl[(CRC ^ *P++) & 0xFF] ^ (CRC >> 8);
|
|
}
|
|
while (Len--)
|
|
CRC = Tbl[(CRC ^ *P++) & 0xFF] ^ (CRC >> 8);
|
|
return CRC ^ 0xFFFFFFFFU;
|
|
}
|
|
#else
|
|
#include <zlib.h>
|
|
uint32_t llvm::crc32(uint32_t CRC, StringRef S) {
|
|
return ::crc32(CRC, (const Bytef *)S.data(), S.size());
|
|
}
|
|
#endif
|