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40ea28492e
This is part of a larger effort to get the Stream code moved up to Support. I don't want to do it in one large patch, in part because the changes are so big that it will treat everything as file deletions and add, losing history in the process. Aside from that though, it's just a good idea in general to make small changes. So this change only changes the names of the Stream related source files, and applies necessary source fix ups. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296211 91177308-0d34-0410-b5e6-96231b3b80d8
104 lines
3.3 KiB
C++
104 lines
3.3 KiB
C++
//===- StringTableBuilder.cpp - PDB String Table ----------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/DebugInfo/PDB/Native/StringTableBuilder.h"
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#include "llvm/ADT/ArrayRef.h"
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#include "llvm/DebugInfo/MSF/BinaryStreamWriter.h"
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#include "llvm/DebugInfo/PDB/Native/Hash.h"
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#include "llvm/DebugInfo/PDB/Native/RawTypes.h"
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#include "llvm/Support/Endian.h"
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using namespace llvm;
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using namespace llvm::support;
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using namespace llvm::support::endian;
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using namespace llvm::pdb;
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uint32_t StringTableBuilder::insert(StringRef S) {
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auto P = Strings.insert({S, StringSize});
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// If a given string didn't exist in the string table, we want to increment
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// the string table size.
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if (P.second)
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StringSize += S.size() + 1; // +1 for '\0'
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return P.first->second;
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}
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static uint32_t computeBucketCount(uint32_t NumStrings) {
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// The /names stream is basically an on-disk open-addressing hash table.
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// Hash collisions are resolved by linear probing. We cannot make
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// utilization 100% because it will make the linear probing extremely
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// slow. But lower utilization wastes disk space. As a reasonable
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// load factor, we choose 80%. We need +1 because slot 0 is reserved.
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return (NumStrings + 1) * 1.25;
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}
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uint32_t StringTableBuilder::finalize() {
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uint32_t Size = 0;
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Size += sizeof(StringTableHeader);
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Size += StringSize;
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Size += sizeof(uint32_t); // Hash table begins with 4-byte size field.
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uint32_t BucketCount = computeBucketCount(Strings.size());
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Size += BucketCount * sizeof(uint32_t);
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Size +=
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sizeof(uint32_t); // The /names stream ends with the number of strings.
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return Size;
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}
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Error StringTableBuilder::commit(msf::StreamWriter &Writer) const {
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// Write a header
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StringTableHeader H;
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H.Signature = StringTableSignature;
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H.HashVersion = 1;
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H.ByteSize = StringSize;
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if (auto EC = Writer.writeObject(H))
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return EC;
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// Write a string table.
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uint32_t StringStart = Writer.getOffset();
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for (auto Pair : Strings) {
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StringRef S = Pair.first;
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uint32_t Offset = Pair.second;
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Writer.setOffset(StringStart + Offset);
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if (auto EC = Writer.writeZeroString(S))
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return EC;
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}
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Writer.setOffset(StringStart + StringSize);
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// Write a hash table.
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uint32_t BucketCount = computeBucketCount(Strings.size());
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if (auto EC = Writer.writeInteger(BucketCount, llvm::support::little))
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return EC;
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std::vector<ulittle32_t> Buckets(BucketCount);
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for (auto Pair : Strings) {
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StringRef S = Pair.first;
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uint32_t Offset = Pair.second;
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uint32_t Hash = hashStringV1(S);
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for (uint32_t I = 0; I != BucketCount; ++I) {
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uint32_t Slot = (Hash + I) % BucketCount;
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if (Slot == 0)
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continue; // Skip reserved slot
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if (Buckets[Slot] != 0)
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continue;
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Buckets[Slot] = Offset;
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break;
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}
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}
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if (auto EC = Writer.writeArray(ArrayRef<ulittle32_t>(Buckets)))
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return EC;
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if (auto EC = Writer.writeInteger(static_cast<uint32_t>(Strings.size()),
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llvm::support::little))
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return EC;
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return Error::success();
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}
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