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//===--- ExponentialGrowthAppendingBinaryByteStream.h -----------*- C++ -*-===//
// This source file is part of the open source project
// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
// See for license information
// See for the list of Swift project authors
/// Defines an \c llvm::WritableBinaryStream whose internal buffer grows
/// exponentially in size as data is written to it. It is thus more efficient
/// than llvm::AppendingBinaryByteStream if a lot of small data gets appended to
/// it.
#include "swift/Basic/LLVM.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/Support/BinaryByteStream.h"
namespace swift {
/// An implementation of WritableBinaryStream which can write at its end
/// causing the underlying data to grow. This class owns the underlying data.
class ExponentialGrowthAppendingBinaryByteStream
: public llvm::WritableBinaryStream {
/// The buffer holding the data.
SmallVector<uint8_t, 0> Data;
/// Data in the stream is always encoded in little-endian byte order.
const llvm::support::endianness Endian = llvm::support::endianness::little;
ExponentialGrowthAppendingBinaryByteStream() = default;
void reserve(size_t Size);
llvm::support::endianness getEndian() const override { return Endian; }
llvm::Error readBytes(uint32_t Offset, uint32_t Size,
ArrayRef<uint8_t> &Buffer) override;
llvm::Error readLongestContiguousChunk(uint32_t Offset,
ArrayRef<uint8_t> &Buffer) override;
MutableArrayRef<uint8_t> data() { return Data; }
uint32_t getLength() override { return Data.size(); }
llvm::Error writeBytes(uint32_t Offset, ArrayRef<uint8_t> Buffer) override;
/// This is an optimized version of \c writeBytes specifically for integers.
/// Integers are written in little-endian byte order.
template<typename T>
llvm::Error writeInteger(uint32_t Offset, T Value) {
static_assert(std::is_integral<T>::value, "Integer required.");
if (auto Error = checkOffsetForWrite(Offset, sizeof(T))) {
return Error;
// Resize the internal buffer if needed.
uint32_t RequiredSize = Offset + sizeof(T);
if (RequiredSize > Data.size()) {
llvm::support::endian::write<T, llvm::support::unaligned>( + Offset, Value, Endian);
return llvm::Error::success();
llvm::Error commit() override { return llvm::Error::success(); }
virtual llvm::BinaryStreamFlags getFlags() const override {
return llvm::BSF_Write | llvm::BSF_Append;
} // end namespace swift