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//===- NameHashTable.cpp - PDB Name Hash Table ------------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/DebugInfo/PDB/Raw/NameHashTable.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/DebugInfo/PDB/Raw/ByteStream.h"
#include "llvm/DebugInfo/PDB/Raw/StreamReader.h"
#include "llvm/Support/Endian.h"
using namespace llvm;
using namespace llvm::support;
using namespace llvm::pdb;
typedef uint32_t *PUL;
typedef uint16_t *PUS;
static inline uint32_t 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 - Longs.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);
}
static inline uint32_t 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 * 1664525L + 1013904223L;
}
NameHashTable::NameHashTable() : Signature(0), HashVersion(0), NameCount(0) {}
std::error_code NameHashTable::load(StreamReader &Stream) {
struct Header {
support::ulittle32_t Signature;
support::ulittle32_t HashVersion;
support::ulittle32_t ByteSize;
};
Header H;
Stream.readObject(&H);
if (H.Signature != 0xEFFEEFFE)
return std::make_error_code(std::errc::illegal_byte_sequence);
if (H.HashVersion != 1 && H.HashVersion != 2)
return std::make_error_code(std::errc::not_supported);
Signature = H.Signature;
HashVersion = H.HashVersion;
NamesBuffer.initialize(Stream, H.ByteSize);
support::ulittle32_t HashCount;
Stream.readObject(&HashCount);
std::vector<support::ulittle32_t> BucketArray(HashCount);
Stream.readArray<support::ulittle32_t>(BucketArray);
IDs.assign(BucketArray.begin(), BucketArray.end());
if (Stream.bytesRemaining() < sizeof(support::ulittle32_t))
return std::make_error_code(std::errc::illegal_byte_sequence);
Stream.readInteger(NameCount);
return std::error_code();
}
StringRef NameHashTable::getStringForID(uint32_t ID) const {
if (ID == IDs[0])
return StringRef();
return StringRef(NamesBuffer.str().begin() + ID);
}
uint32_t NameHashTable::getIDForString(StringRef Str) const {
uint32_t Hash = (HashVersion == 1) ? HashStringV1(Str) : HashStringV2(Str);
size_t Count = IDs.size();
uint32_t Start = Hash % Count;
for (size_t I = 0; I < Count; ++I) {
// The hash is just a starting point for the search, but if it
// doesn't work we should find the string no matter what, because
// we iterate the entire array.
uint32_t Index = (Start + I) % Count;
uint32_t ID = IDs[Index];
StringRef S = getStringForID(ID);
if (S == Str)
return ID;
}
// IDs[0] contains the ID of the "invalid" entry.
return IDs[0];
}
ArrayRef<uint32_t> NameHashTable::name_ids() const {
return ArrayRef<uint32_t>(IDs).slice(1, NameCount);
}
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