llvm/lib/DebugInfo/Msf/MappedBlockStream.cpp - toolchain/llvm-project - Gitiles

 //===- MappedBlockStream.cpp - Reads stream data from an MSF file ---------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//

 #include "llvm/DebugInfo/Msf/MappedBlockStream.h"
 #include "llvm/DebugInfo/Msf/DirectoryStreamData.h"
 #include "llvm/DebugInfo/Msf/IMsfStreamData.h"
 #include "llvm/DebugInfo/Msf/IndexedStreamData.h"
 #include "llvm/DebugInfo/Msf/MsfError.h"

 using namespace llvm;
 using namespace llvm::msf;

 namespace {
 // This exists so that we can use make_unique (which requires a public default
 // constructor, while still keeping the constructor of MappedBlockStream
 // protected, forcing users to go through the `create` interface.
 class MappedBlockStreamImpl : public MappedBlockStream {
 public:
   MappedBlockStreamImpl(std::unique_ptr<IMsfStreamData> Data,
                         const IMsfFile &File)
       : MappedBlockStream(std::move(Data), File) {}
 };
 }

 typedef std::pair<uint32_t, uint32_t> Interval;
 static Interval intersect(const Interval &I1, const Interval &I2) {
   return std::make_pair(std::max(I1.first, I2.first),
                         std::min(I1.second, I2.second));
 }

 MappedBlockStream::MappedBlockStream(std::unique_ptr<IMsfStreamData> Data,
                                      const IMsfFile &File)
     : Msf(File), Data(std::move(Data)) {}

 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 > Data->getLength())
     return make_error<MsfError>(msf_error_code::insufficient_buffer);
   if (Offset > Data->getLength() - Size)
     return make_error<MsfError>(msf_error_code::insufficient_buffer);

   if (tryReadContiguously(Offset, Size, Buffer))
     return Error::success();

   auto CacheIter = CacheMap.find(Offset);
   if (CacheIter != CacheMap.end()) {
     // Try to find an alloc that was large enough for this request.
     for (auto &Entry : CacheIter->second) {
       if (Entry.size() >= Size) {
         Buffer = Entry.slice(0, Size);
         return Error::success();
       }
     }
   }

   // We couldn't find a buffer that started at the correct offset (the most
   // common scenario).  Try to see if there is a buffer that starts at some
   // other offset but overlaps the desired range.
   for (auto &CacheItem : CacheMap) {
     Interval RequestExtent = std::make_pair(Offset, Offset + Size);

     // We already checked this one on the fast path above.
     if (CacheItem.first == Offset)
       continue;
     // If the initial extent of the cached item is beyond the ending extent
     // of the request, there is no overlap.
     if (CacheItem.first >= Offset + Size)
       continue;

     // We really only have to check the last item in the list, since we append
     // in order of increasing length.
     if (CacheItem.second.empty())
       continue;

     auto CachedAlloc = CacheItem.second.back();
     // If the initial extent of the request is beyond the ending extent of
     // the cached item, there is no overlap.
     Interval CachedExtent =
         std::make_pair(CacheItem.first, CacheItem.first + CachedAlloc.size());
     if (RequestExtent.first >= CachedExtent.first + CachedExtent.second)
       continue;

     Interval Intersection = intersect(CachedExtent, RequestExtent);
     // Only use this if the entire request extent is contained in the cached
     // extent.
     if (Intersection != RequestExtent)
       continue;

     uint32_t CacheRangeOffset =
         AbsoluteDifference(CachedExtent.first, Intersection.first);
     Buffer = CachedAlloc.slice(CacheRangeOffset, Size);
     return Error::success();
   }

   // Otherwise allocate a large enough buffer in the pool, memcpy the data
   // into it, and return an ArrayRef to that.  Do not touch existing pool
   // allocations, as existing clients may be holding a pointer which must
   // not be invalidated.
   uint8_t *WriteBuffer = static_cast<uint8_t *>(Pool.Allocate(Size, 8));
   if (auto EC = readBytes(Offset, MutableArrayRef<uint8_t>(WriteBuffer, Size)))
     return EC;

   if (CacheIter != CacheMap.end()) {
     CacheIter->second.emplace_back(WriteBuffer, Size);
   } else {
     std::vector<CacheEntry> List;
     List.emplace_back(WriteBuffer, Size);
     CacheMap.insert(std::make_pair(Offset, List));
   }
   Buffer = ArrayRef<uint8_t>(WriteBuffer, Size);
   return Error::success();
 }

 Error MappedBlockStream::readLongestContiguousChunk(
     uint32_t Offset, ArrayRef<uint8_t> &Buffer) const {
   // Make sure we aren't trying to read beyond the end of the stream.
   if (Offset >= Data->getLength())
     return make_error<MsfError>(msf_error_code::insufficient_buffer);
   uint32_t First = Offset / Msf.getBlockSize();
   uint32_t Last = First;

   auto BlockList = Data->getStreamBlocks();
   while (Last < Msf.getBlockCount() - 1) {
     if (BlockList[Last] != BlockList[Last + 1] - 1)
       break;
     ++Last;
   }

   uint32_t OffsetInFirstBlock = Offset % Msf.getBlockSize();
   uint32_t BytesFromFirstBlock = Msf.getBlockSize() - OffsetInFirstBlock;
   uint32_t BlockSpan = Last - First + 1;
   uint32_t ByteSpan =
       BytesFromFirstBlock + (BlockSpan - 1) * Msf.getBlockSize();
   auto Result = Msf.getBlockData(BlockList[First], Msf.getBlockSize());
   if (!Result)
     return Result.takeError();
   Buffer = Result->drop_front(OffsetInFirstBlock);
   Buffer = ArrayRef<uint8_t>(Buffer.data(), ByteSpan);
   return Error::success();
 }

 uint32_t MappedBlockStream::getLength() const { return Data->getLength(); }

 Error MappedBlockStream::commit() const { 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 / Msf.getBlockSize();
   uint32_t OffsetInBlock = Offset % Msf.getBlockSize();
   uint32_t BytesFromFirstBlock =
       std::min(Size, Msf.getBlockSize() - OffsetInBlock);
   uint32_t NumAdditionalBlocks =
       llvm::alignTo(Size - BytesFromFirstBlock, Msf.getBlockSize()) /
       Msf.getBlockSize();

   auto BlockList = Data->getStreamBlocks();
   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];
   auto Result = Msf.getBlockData(FirstBlockAddr, Msf.getBlockSize());
   if (!Result) {
     consumeError(Result.takeError());
     return false;
   }
   auto Data = Result->drop_front(OffsetInBlock);
   Buffer = ArrayRef<uint8_t>(Data.data(), Size);
   return true;
 }

 Error MappedBlockStream::readBytes(uint32_t Offset,
                                    MutableArrayRef<uint8_t> Buffer) const {
   uint32_t BlockNum = Offset / Msf.getBlockSize();
   uint32_t OffsetInBlock = Offset % Msf.getBlockSize();

   // Make sure we aren't trying to read beyond the end of the stream.
   if (Buffer.size() > Data->getLength())
     return make_error<MsfError>(msf_error_code::insufficient_buffer);
   if (Offset > Data->getLength() - Buffer.size())
     return make_error<MsfError>(msf_error_code::insufficient_buffer);

   uint32_t BytesLeft = Buffer.size();
   uint32_t BytesWritten = 0;
   uint8_t *WriteBuffer = Buffer.data();
   auto BlockList = Data->getStreamBlocks();
   while (BytesLeft > 0) {
     uint32_t StreamBlockAddr = BlockList[BlockNum];

     auto Result = Msf.getBlockData(StreamBlockAddr, Msf.getBlockSize());
     if (!Result)
       return Result.takeError();

     auto Data = *Result;
     const uint8_t *ChunkStart = Data.data() + OffsetInBlock;
     uint32_t BytesInChunk =
         std::min(BytesLeft, Msf.getBlockSize() - OffsetInBlock);
     ::memcpy(WriteBuffer + BytesWritten, ChunkStart, BytesInChunk);

     BytesWritten += BytesInChunk;
     BytesLeft -= BytesInChunk;
     ++BlockNum;
     OffsetInBlock = 0;
   }

   return Error::success();
 }

 Error MappedBlockStream::writeBytes(uint32_t Offset,
                                     ArrayRef<uint8_t> Buffer) const {
   // Make sure we aren't trying to write beyond the end of the stream.
   if (Buffer.size() > Data->getLength())
     return make_error<MsfError>(msf_error_code::insufficient_buffer);

   if (Offset > Data->getLength() - Buffer.size())
     return make_error<MsfError>(msf_error_code::insufficient_buffer);

   uint32_t BlockNum = Offset / Msf.getBlockSize();
   uint32_t OffsetInBlock = Offset % Msf.getBlockSize();

   uint32_t BytesLeft = Buffer.size();
   auto BlockList = Data->getStreamBlocks();
   uint32_t BytesWritten = 0;
   while (BytesLeft > 0) {
     uint32_t StreamBlockAddr = BlockList[BlockNum];
     uint32_t BytesToWriteInChunk =
         std::min(BytesLeft, Msf.getBlockSize() - OffsetInBlock);

     const uint8_t *Chunk = Buffer.data() + BytesWritten;
     ArrayRef<uint8_t> ChunkData(Chunk, BytesToWriteInChunk);
     if (auto EC = Msf.setBlockData(StreamBlockAddr, OffsetInBlock, ChunkData))
       return EC;

     BytesLeft -= BytesToWriteInChunk;
     BytesWritten += BytesToWriteInChunk;
     ++BlockNum;
     OffsetInBlock = 0;
   }

   // If this write overlapped a read which previously came from the pool,
   // someone may still be holding a pointer to that alloc which is now invalid.
   // Compute the overlapping range and update the cache entry, so any
   // outstanding buffers are automatically updated.
   for (const auto &MapEntry : CacheMap) {
     // If the end of the written extent precedes the beginning of the cached
     // extent, ignore this map entry.
     if (Offset + BytesWritten < MapEntry.first)
       continue;
     for (const auto &Alloc : MapEntry.second) {
       // If the end of the cached extent precedes the beginning of the written
       // extent, ignore this alloc.
       if (MapEntry.first + Alloc.size() < Offset)
         continue;

       // If we get here, they are guaranteed to overlap.
       Interval WriteInterval = std::make_pair(Offset, Offset + BytesWritten);
       Interval CachedInterval =
           std::make_pair(MapEntry.first, MapEntry.first + Alloc.size());
       // If they overlap, we need to write the new data into the overlapping
       // range.
       auto Intersection = intersect(WriteInterval, CachedInterval);
       assert(Intersection.first <= Intersection.second);

       uint32_t Length = Intersection.second - Intersection.first;
       uint32_t SrcOffset =
           AbsoluteDifference(WriteInterval.first, Intersection.first);
       uint32_t DestOffset =
           AbsoluteDifference(CachedInterval.first, Intersection.first);
       ::memcpy(Alloc.data() + DestOffset, Buffer.data() + SrcOffset, Length);
     }
   }

   return Error::success();
 }

 uint32_t MappedBlockStream::getNumBytesCopied() const {
   return static_cast<uint32_t>(Pool.getBytesAllocated());
 }

 Expected<std::unique_ptr<MappedBlockStream>>
 MappedBlockStream::createIndexedStream(uint32_t StreamIdx,
                                        const IMsfFile &File) {
   if (StreamIdx >= File.getNumStreams())
     return make_error<MsfError>(msf_error_code::no_stream);

   auto Data = llvm::make_unique<IndexedStreamData>(StreamIdx, File);
   return llvm::make_unique<MappedBlockStreamImpl>(std::move(Data), File);
 }

 Expected<std::unique_ptr<MappedBlockStream>>
 MappedBlockStream::createDirectoryStream(uint32_t Length,
                                          ArrayRef<support::ulittle32_t> Blocks,
                                          const IMsfFile &File) {
   auto Data = llvm::make_unique<DirectoryStreamData>(Length, Blocks);
   return llvm::make_unique<MappedBlockStreamImpl>(std::move(Data), File);
 }
	//===- MappedBlockStream.cpp - Reads stream data from an MSF file ---------===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//

	#include "llvm/DebugInfo/Msf/MappedBlockStream.h"
	#include "llvm/DebugInfo/Msf/DirectoryStreamData.h"
	#include "llvm/DebugInfo/Msf/IMsfStreamData.h"
	#include "llvm/DebugInfo/Msf/IndexedStreamData.h"
	#include "llvm/DebugInfo/Msf/MsfError.h"

	using namespace llvm;
	using namespace llvm::msf;

	namespace {
	// This exists so that we can use make_unique (which requires a public default
	// constructor, while still keeping the constructor of MappedBlockStream
	// protected, forcing users to go through the `create` interface.
	class MappedBlockStreamImpl : public MappedBlockStream {
	public:
	MappedBlockStreamImpl(std::unique_ptr<IMsfStreamData> Data,
	const IMsfFile &File)
	: MappedBlockStream(std::move(Data), File) {}
	};
	}

	typedef std::pair<uint32_t, uint32_t> Interval;
	static Interval intersect(const Interval &I1, const Interval &I2) {
	return std::make_pair(std::max(I1.first, I2.first),
	std::min(I1.second, I2.second));
	}

	MappedBlockStream::MappedBlockStream(std::unique_ptr<IMsfStreamData> Data,
	const IMsfFile &File)
	: Msf(File), Data(std::move(Data)) {}

	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 > Data->getLength())
	return make_error<MsfError>(msf_error_code::insufficient_buffer);
	if (Offset > Data->getLength() - Size)
	return make_error<MsfError>(msf_error_code::insufficient_buffer);

	if (tryReadContiguously(Offset, Size, Buffer))
	return Error::success();

	auto CacheIter = CacheMap.find(Offset);
	if (CacheIter != CacheMap.end()) {
	// Try to find an alloc that was large enough for this request.
	for (auto &Entry : CacheIter->second) {
	if (Entry.size() >= Size) {
	Buffer = Entry.slice(0, Size);
	return Error::success();
	}
	}
	}

	// We couldn't find a buffer that started at the correct offset (the most
	// common scenario). Try to see if there is a buffer that starts at some
	// other offset but overlaps the desired range.
	for (auto &CacheItem : CacheMap) {
	Interval RequestExtent = std::make_pair(Offset, Offset + Size);

	// We already checked this one on the fast path above.
	if (CacheItem.first == Offset)
	continue;
	// If the initial extent of the cached item is beyond the ending extent
	// of the request, there is no overlap.
	if (CacheItem.first >= Offset + Size)
	continue;

	// We really only have to check the last item in the list, since we append
	// in order of increasing length.
	if (CacheItem.second.empty())
	continue;

	auto CachedAlloc = CacheItem.second.back();
	// If the initial extent of the request is beyond the ending extent of
	// the cached item, there is no overlap.
	Interval CachedExtent =
	std::make_pair(CacheItem.first, CacheItem.first + CachedAlloc.size());
	if (RequestExtent.first >= CachedExtent.first + CachedExtent.second)
	continue;

	Interval Intersection = intersect(CachedExtent, RequestExtent);
	// Only use this if the entire request extent is contained in the cached
	// extent.
	if (Intersection != RequestExtent)
	continue;

	uint32_t CacheRangeOffset =
	AbsoluteDifference(CachedExtent.first, Intersection.first);
	Buffer = CachedAlloc.slice(CacheRangeOffset, Size);
	return Error::success();
	}

	// Otherwise allocate a large enough buffer in the pool, memcpy the data
	// into it, and return an ArrayRef to that. Do not touch existing pool
	// allocations, as existing clients may be holding a pointer which must
	// not be invalidated.
	uint8_t WriteBuffer = static_cast<uint8_t >(Pool.Allocate(Size, 8));
	if (auto EC = readBytes(Offset, MutableArrayRef<uint8_t>(WriteBuffer, Size)))
	return EC;

	if (CacheIter != CacheMap.end()) {
	CacheIter->second.emplace_back(WriteBuffer, Size);
	} else {
	std::vector<CacheEntry> List;
	List.emplace_back(WriteBuffer, Size);
	CacheMap.insert(std::make_pair(Offset, List));
	}
	Buffer = ArrayRef<uint8_t>(WriteBuffer, Size);
	return Error::success();
	}

	Error MappedBlockStream::readLongestContiguousChunk(
	uint32_t Offset, ArrayRef<uint8_t> &Buffer) const {
	// Make sure we aren't trying to read beyond the end of the stream.
	if (Offset >= Data->getLength())
	return make_error<MsfError>(msf_error_code::insufficient_buffer);
	uint32_t First = Offset / Msf.getBlockSize();
	uint32_t Last = First;

	auto BlockList = Data->getStreamBlocks();
	while (Last < Msf.getBlockCount() - 1) {
	if (BlockList[Last] != BlockList[Last + 1] - 1)
	break;
	++Last;
	}

	uint32_t OffsetInFirstBlock = Offset % Msf.getBlockSize();
	uint32_t BytesFromFirstBlock = Msf.getBlockSize() - OffsetInFirstBlock;
	uint32_t BlockSpan = Last - First + 1;
	uint32_t ByteSpan =
	BytesFromFirstBlock + (BlockSpan - 1) * Msf.getBlockSize();
	auto Result = Msf.getBlockData(BlockList[First], Msf.getBlockSize());
	if (!Result)
	return Result.takeError();
	Buffer = Result->drop_front(OffsetInFirstBlock);
	Buffer = ArrayRef<uint8_t>(Buffer.data(), ByteSpan);
	return Error::success();
	}

	uint32_t MappedBlockStream::getLength() const { return Data->getLength(); }

	Error MappedBlockStream::commit() const { 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 / Msf.getBlockSize();
	uint32_t OffsetInBlock = Offset % Msf.getBlockSize();
	uint32_t BytesFromFirstBlock =
	std::min(Size, Msf.getBlockSize() - OffsetInBlock);
	uint32_t NumAdditionalBlocks =
	llvm::alignTo(Size - BytesFromFirstBlock, Msf.getBlockSize()) /
	Msf.getBlockSize();

	auto BlockList = Data->getStreamBlocks();
	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];
	auto Result = Msf.getBlockData(FirstBlockAddr, Msf.getBlockSize());
	if (!Result) {
	consumeError(Result.takeError());
	return false;
	}
	auto Data = Result->drop_front(OffsetInBlock);
	Buffer = ArrayRef<uint8_t>(Data.data(), Size);
	return true;
	}

	Error MappedBlockStream::readBytes(uint32_t Offset,
	MutableArrayRef<uint8_t> Buffer) const {
	uint32_t BlockNum = Offset / Msf.getBlockSize();
	uint32_t OffsetInBlock = Offset % Msf.getBlockSize();

	// Make sure we aren't trying to read beyond the end of the stream.
	if (Buffer.size() > Data->getLength())
	return make_error<MsfError>(msf_error_code::insufficient_buffer);
	if (Offset > Data->getLength() - Buffer.size())
	return make_error<MsfError>(msf_error_code::insufficient_buffer);

	uint32_t BytesLeft = Buffer.size();
	uint32_t BytesWritten = 0;
	uint8_t *WriteBuffer = Buffer.data();
	auto BlockList = Data->getStreamBlocks();
	while (BytesLeft > 0) {
	uint32_t StreamBlockAddr = BlockList[BlockNum];

	auto Result = Msf.getBlockData(StreamBlockAddr, Msf.getBlockSize());
	if (!Result)
	return Result.takeError();

	auto Data = *Result;
	const uint8_t *ChunkStart = Data.data() + OffsetInBlock;
	uint32_t BytesInChunk =
	std::min(BytesLeft, Msf.getBlockSize() - OffsetInBlock);
	::memcpy(WriteBuffer + BytesWritten, ChunkStart, BytesInChunk);

	BytesWritten += BytesInChunk;
	BytesLeft -= BytesInChunk;
	++BlockNum;
	OffsetInBlock = 0;
	}

	return Error::success();
	}

	Error MappedBlockStream::writeBytes(uint32_t Offset,
	ArrayRef<uint8_t> Buffer) const {
	// Make sure we aren't trying to write beyond the end of the stream.
	if (Buffer.size() > Data->getLength())
	return make_error<MsfError>(msf_error_code::insufficient_buffer);

	if (Offset > Data->getLength() - Buffer.size())
	return make_error<MsfError>(msf_error_code::insufficient_buffer);

	uint32_t BlockNum = Offset / Msf.getBlockSize();
	uint32_t OffsetInBlock = Offset % Msf.getBlockSize();

	uint32_t BytesLeft = Buffer.size();
	auto BlockList = Data->getStreamBlocks();
	uint32_t BytesWritten = 0;
	while (BytesLeft > 0) {
	uint32_t StreamBlockAddr = BlockList[BlockNum];
	uint32_t BytesToWriteInChunk =
	std::min(BytesLeft, Msf.getBlockSize() - OffsetInBlock);

	const uint8_t *Chunk = Buffer.data() + BytesWritten;
	ArrayRef<uint8_t> ChunkData(Chunk, BytesToWriteInChunk);
	if (auto EC = Msf.setBlockData(StreamBlockAddr, OffsetInBlock, ChunkData))
	return EC;

	BytesLeft -= BytesToWriteInChunk;
	BytesWritten += BytesToWriteInChunk;
	++BlockNum;
	OffsetInBlock = 0;
	}

	// If this write overlapped a read which previously came from the pool,
	// someone may still be holding a pointer to that alloc which is now invalid.
	// Compute the overlapping range and update the cache entry, so any
	// outstanding buffers are automatically updated.
	for (const auto &MapEntry : CacheMap) {
	// If the end of the written extent precedes the beginning of the cached
	// extent, ignore this map entry.
	if (Offset + BytesWritten < MapEntry.first)
	continue;
	for (const auto &Alloc : MapEntry.second) {
	// If the end of the cached extent precedes the beginning of the written
	// extent, ignore this alloc.
	if (MapEntry.first + Alloc.size() < Offset)
	continue;

	// If we get here, they are guaranteed to overlap.
	Interval WriteInterval = std::make_pair(Offset, Offset + BytesWritten);
	Interval CachedInterval =
	std::make_pair(MapEntry.first, MapEntry.first + Alloc.size());
	// If they overlap, we need to write the new data into the overlapping
	// range.
	auto Intersection = intersect(WriteInterval, CachedInterval);
	assert(Intersection.first <= Intersection.second);

	uint32_t Length = Intersection.second - Intersection.first;
	uint32_t SrcOffset =
	AbsoluteDifference(WriteInterval.first, Intersection.first);
	uint32_t DestOffset =
	AbsoluteDifference(CachedInterval.first, Intersection.first);
	::memcpy(Alloc.data() + DestOffset, Buffer.data() + SrcOffset, Length);
	}
	}

	return Error::success();
	}

	uint32_t MappedBlockStream::getNumBytesCopied() const {
	return static_cast<uint32_t>(Pool.getBytesAllocated());
	}

	Expected<std::unique_ptr<MappedBlockStream>>
	MappedBlockStream::createIndexedStream(uint32_t StreamIdx,
	const IMsfFile &File) {
	if (StreamIdx >= File.getNumStreams())
	return make_error<MsfError>(msf_error_code::no_stream);

	auto Data = llvm::make_unique<IndexedStreamData>(StreamIdx, File);
	return llvm::make_unique<MappedBlockStreamImpl>(std::move(Data), File);
	}

	Expected<std::unique_ptr<MappedBlockStream>>
	MappedBlockStream::createDirectoryStream(uint32_t Length,
	ArrayRef<support::ulittle32_t> Blocks,
	const IMsfFile &File) {
	auto Data = llvm::make_unique<DirectoryStreamData>(Length, Blocks);
	return llvm::make_unique<MappedBlockStreamImpl>(std::move(Data), File);
	}