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Often you have an array and you just want to use it. With the current design, you have to first construct a `BinaryByteStream`, and then create a `BinaryStreamRef` from it. Worse, the `BinaryStreamRef` holds a pointer to the `BinaryByteStream`, so you can't just create a temporary one to appease the compiler, you have to actually hold onto both the `ArrayRef` as well as the `BinaryByteStream` *AND* the `BinaryStreamReader` on top of that. This makes for very cumbersome code, often requiring one to store a `BinaryByteStream` in a class just to circumvent this. At the cost of some added complexity (not exposed to users, but internal to the library), we can do better than this. This patch allows us to construct `BinaryStreamReaders` and `BinaryStreamWriters` directly from source data (e.g. `StringRef`, `MutableArrayRef<uint8_t>`, etc). Not only does this reduce the amount of code you have to type and make it more obvious how to use it, but it solves real lifetime issues when it's inconvenient to hold onto a `BinaryByteStream` for a long time. The additional complexity is in the form of an added layer of indirection. Whereas before we simply stored a `BinaryStream*` in the ref, we now store both a `BinaryStream*` **and** a `std::shared_ptr<BinaryStream>`. When the user wants to construct a `BinaryStreamRef` directly from an `ArrayRef` etc, we allocate an internal object that holds ownership over a `BinaryByteStream` and forwards all calls, and store this in the `shared_ptr<>`. This also maintains the ref semantics, as you can copy it by value and references refer to the same underlying stream -- the one being held in the object stored in the `shared_ptr`. Differential Revision: https://reviews.llvm.org/D33293 llvm-svn: 303294
89 lines
2.9 KiB
C++
89 lines
2.9 KiB
C++
//===- BinaryStreamWriter.cpp - Writes objects to a BinaryStream ----------===//
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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/Support/BinaryStreamWriter.h"
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#include "llvm/Support/BinaryStreamError.h"
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#include "llvm/Support/BinaryStreamReader.h"
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#include "llvm/Support/BinaryStreamRef.h"
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using namespace llvm;
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BinaryStreamWriter::BinaryStreamWriter(WritableBinaryStreamRef Ref)
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: Stream(Ref) {}
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BinaryStreamWriter::BinaryStreamWriter(WritableBinaryStream &Stream)
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: Stream(Stream) {}
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BinaryStreamWriter::BinaryStreamWriter(MutableArrayRef<uint8_t> Data,
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llvm::support::endianness Endian)
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: Stream(Data, Endian) {}
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Error BinaryStreamWriter::writeBytes(ArrayRef<uint8_t> Buffer) {
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if (auto EC = Stream.writeBytes(Offset, Buffer))
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return EC;
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Offset += Buffer.size();
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return Error::success();
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}
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Error BinaryStreamWriter::writeCString(StringRef Str) {
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if (auto EC = writeFixedString(Str))
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return EC;
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if (auto EC = writeObject('\0'))
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return EC;
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return Error::success();
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}
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Error BinaryStreamWriter::writeFixedString(StringRef Str) {
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return writeBytes(ArrayRef<uint8_t>(Str.bytes_begin(), Str.bytes_end()));
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}
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Error BinaryStreamWriter::writeStreamRef(BinaryStreamRef Ref) {
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return writeStreamRef(Ref, Ref.getLength());
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}
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Error BinaryStreamWriter::writeStreamRef(BinaryStreamRef Ref, uint32_t Length) {
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BinaryStreamReader SrcReader(Ref.slice(0, Length));
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// This is a bit tricky. If we just call readBytes, we are requiring that it
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// return us the entire stream as a contiguous buffer. There is no guarantee
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// this can be satisfied by returning a reference straight from the buffer, as
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// an implementation may not store all data in a single contiguous buffer. So
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// we iterate over each contiguous chunk, writing each one in succession.
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while (SrcReader.bytesRemaining() > 0) {
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ArrayRef<uint8_t> Chunk;
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if (auto EC = SrcReader.readLongestContiguousChunk(Chunk))
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return EC;
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if (auto EC = writeBytes(Chunk))
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return EC;
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}
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return Error::success();
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}
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std::pair<BinaryStreamWriter, BinaryStreamWriter>
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BinaryStreamWriter::split(uint32_t Off) const {
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assert(getLength() >= Off);
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WritableBinaryStreamRef First = Stream.drop_front(Offset);
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WritableBinaryStreamRef Second = First.drop_front(Off);
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First = First.keep_front(Off);
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BinaryStreamWriter W1{First};
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BinaryStreamWriter W2{Second};
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return std::make_pair(W1, W2);
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}
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Error BinaryStreamWriter::padToAlignment(uint32_t Align) {
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uint32_t NewOffset = alignTo(Offset, Align);
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if (NewOffset > getLength())
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return make_error<BinaryStreamError>(stream_error_code::stream_too_short);
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Offset = NewOffset;
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return Error::success();
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}
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