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//===- Hash.cpp - PDB Hash Functions --------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "llvm/DebugInfo/PDB/Native/Hash.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/Support/CRC.h"
#include "llvm/Support/Endian.h"
#include <cstdint>
using namespace llvm;
using namespace llvm::support;
// Corresponds to `Hasher::lhashPbCb` in PDB/include/misc.h.
// Used for name hash table and TPI/IPI hashes.
uint32_t pdb::hashStringV1(StringRef Str) {
uint32_t Result = 0;
uint32_t Size = Str.size();
ArrayRef<ulittle32_t> Longs(reinterpret_cast<const ulittle32_t *>(Str.data()),
Size / 4);
for (auto Value : Longs)
Result ^= Value;
const uint8_t *Remainder = reinterpret_cast<const uint8_t *>(Longs.end());
uint32_t RemainderSize = Size % 4;
// Maximum of 3 bytes left. Hash a 2 byte word if possible, then hash the
// possibly remaining 1 byte.
if (RemainderSize >= 2) {
uint16_t Value = *reinterpret_cast<const ulittle16_t *>(Remainder);
Result ^= static_cast<uint32_t>(Value);
Remainder += 2;
RemainderSize -= 2;
}
// hash possible odd byte
if (RemainderSize == 1) {
Result ^= *(Remainder++);
}
const uint32_t toLowerMask = 0x20202020;
Result |= toLowerMask;
Result ^= (Result >> 11);
return Result ^ (Result >> 16);
}
// Corresponds to `HasherV2::HashULONG` in PDB/include/misc.h.
// Used for name hash table.
uint32_t pdb::hashStringV2(StringRef Str) {
uint32_t Hash = 0xb170a1bf;
ArrayRef<char> Buffer(Str.begin(), Str.end());
ArrayRef<ulittle32_t> Items(
reinterpret_cast<const ulittle32_t *>(Buffer.data()),
Buffer.size() / sizeof(ulittle32_t));
for (ulittle32_t Item : Items) {
Hash += Item;
Hash += (Hash << 10);
Hash ^= (Hash >> 6);
}
Buffer = Buffer.slice(Items.size() * sizeof(ulittle32_t));
for (uint8_t Item : Buffer) {
Hash += Item;
Hash += (Hash << 10);
Hash ^= (Hash >> 6);
}
return Hash * 1664525U + 1013904223U;
}
// Corresponds to `SigForPbCb` in langapi/shared/crc32.h.
uint32_t pdb::hashBufferV8(ArrayRef<uint8_t> Buf) {
JamCRC JC(/*Init=*/0U);
JC.update(Buf);
return JC.getCRC();
}
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