e204a6c9a3
With the forthcoming codeview::StringTable which a pdb::StringTable would hold an instance of as one member, this ambiguity becomes confusing. Rename to PDBStringTable to avoid this. llvm-svn: 301948
109 lines
3.3 KiB
C++
109 lines
3.3 KiB
C++
//===- PDBStringTableBuilder.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/PDBStringTableBuilder.h"
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#include "llvm/ADT/ArrayRef.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/BinaryStreamWriter.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 PDBStringTableBuilder::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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uint32_t PDBStringTableBuilder::getStringIndex(StringRef S) {
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auto Iter = Strings.find(S);
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assert(Iter != Strings.end());
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return Iter->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 PDBStringTableBuilder::finalize() {
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uint32_t Size = 0;
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Size += sizeof(PDBStringTableHeader);
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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 PDBStringTableBuilder::commit(BinaryStreamWriter &Writer) const {
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// Write a header
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PDBStringTableHeader H;
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H.Signature = PDBStringTableSignature;
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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.writeCString(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))
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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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return EC;
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return Error::success();
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}
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