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//===- MappedBlockStream.cpp - Reads stream data from a PDBFile -----------===//
//
// 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/MappedBlockStream.h"
#include "llvm/DebugInfo/PDB/Raw/PDBFile.h"
#include "llvm/DebugInfo/PDB/Raw/RawError.h"
using namespace llvm;
using namespace llvm::pdb;
MappedBlockStream::MappedBlockStream(uint32_t StreamIdx, const PDBFile &File) : Pdb(File) {
if (StreamIdx >= Pdb.getNumStreams()) {
StreamLength = 0;
} else {
StreamLength = Pdb.getStreamByteSize(StreamIdx);
BlockList = Pdb.getStreamBlockList(StreamIdx);
}
}
Error MappedBlockStream::readBytes(uint32_t Offset, uint32_t Size,
ArrayRef<uint8_t> &Buffer) const {
// Make sure we aren't trying to read beyond the end of the stream.
if (Size > StreamLength)
return make_error<RawError>(raw_error_code::insufficient_buffer);
if (Offset > StreamLength - Size)
return make_error<RawError>(raw_error_code::insufficient_buffer);
if (tryReadContiguously(Offset, Size, Buffer))
return Error::success();
auto CacheIter = CacheMap.find(Offset);
if (CacheIter != CacheMap.end()) {
// In a more general solution, we would need to guarantee that the
// cached allocation is at least the requested size. In practice, since
// these are CodeView / PDB records, we know they are always formatted
// the same way and never change, so we should never be requesting two
// allocations from the same address with different sizes.
Buffer = ArrayRef<uint8_t>(CacheIter->second, Size);
return Error::success();
}
// Otherwise allocate a large enough buffer in the pool, memcpy the data
// into it, and return an ArrayRef to that.
uint8_t *WriteBuffer = Pool.Allocate<uint8_t>(Size);
if (auto EC = readBytes(Offset, MutableArrayRef<uint8_t>(WriteBuffer, Size)))
return EC;
CacheMap.insert(std::make_pair(Offset, WriteBuffer));
Buffer = ArrayRef<uint8_t>(WriteBuffer, Size);
return Error::success();
}
bool MappedBlockStream::tryReadContiguously(uint32_t Offset, uint32_t Size,
ArrayRef<uint8_t> &Buffer) const {
// Attempt to fulfill the request with a reference directly into the stream.
// This can work even if the request crosses a block boundary, provided that
// all subsequent blocks are contiguous. For example, a 10k read with a 4k
// block size can be filled with a reference if, from the starting offset,
// 3 blocks in a row are contiguous.
uint32_t BlockNum = Offset / Pdb.getBlockSize();
uint32_t OffsetInBlock = Offset % Pdb.getBlockSize();
uint32_t BytesFromFirstBlock =
std::min(Size, Pdb.getBlockSize() - OffsetInBlock);
uint32_t NumAdditionalBlocks =
llvm::alignTo(Size - BytesFromFirstBlock, Pdb.getBlockSize()) /
Pdb.getBlockSize();
uint32_t RequiredContiguousBlocks = NumAdditionalBlocks + 1;
uint32_t E = BlockList[BlockNum];
for (uint32_t I = 0; I < RequiredContiguousBlocks; ++I, ++E) {
if (BlockList[I + BlockNum] != E)
return false;
}
uint32_t FirstBlockAddr = BlockList[BlockNum];
StringRef Str = Pdb.getBlockData(FirstBlockAddr, Pdb.getBlockSize());
Str = Str.drop_front(OffsetInBlock);
Buffer =
ArrayRef<uint8_t>(reinterpret_cast<const uint8_t *>(Str.data()), Size);
return true;
}
Error MappedBlockStream::readBytes(uint32_t Offset,
MutableArrayRef<uint8_t> Buffer) const {
uint32_t BlockNum = Offset / Pdb.getBlockSize();
uint32_t OffsetInBlock = Offset % Pdb.getBlockSize();
// Make sure we aren't trying to read beyond the end of the stream.
if (Buffer.size() > StreamLength)
return make_error<RawError>(raw_error_code::insufficient_buffer);
if (Offset > StreamLength - Buffer.size())
return make_error<RawError>(raw_error_code::insufficient_buffer);
uint32_t BytesLeft = Buffer.size();
uint32_t BytesWritten = 0;
uint8_t *WriteBuffer = Buffer.data();
while (BytesLeft > 0) {
uint32_t StreamBlockAddr = BlockList[BlockNum];
StringRef Data = Pdb.getBlockData(StreamBlockAddr, Pdb.getBlockSize());
const char *ChunkStart = Data.data() + OffsetInBlock;
uint32_t BytesInChunk =
std::min(BytesLeft, Pdb.getBlockSize() - OffsetInBlock);
::memcpy(WriteBuffer + BytesWritten, ChunkStart, BytesInChunk);
BytesWritten += BytesInChunk;
BytesLeft -= BytesInChunk;
++BlockNum;
OffsetInBlock = 0;
}
return Error::success();
}
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