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to reflect the new license. We understand that people may be surprised that we're moving the header entirely to discuss the new license. We checked this carefully with the Foundation's lawyer and we believe this is the correct approach. Essentially, all code in the project is now made available by the LLVM project under our new license, so you will see that the license headers include that license only. Some of our contributors have contributed code under our old license, and accordingly, we have retained a copy of our old license notice in the top-level files in each project and repository. llvm-svn: 351636
102 lines
3.7 KiB
C++
102 lines
3.7 KiB
C++
//===- BinaryStream.h - Base interface for a stream of data -----*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_SUPPORT_BINARYSTREAM_H
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#define LLVM_SUPPORT_BINARYSTREAM_H
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#include "llvm/ADT/ArrayRef.h"
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#include "llvm/ADT/BitmaskEnum.h"
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#include "llvm/Support/BinaryStreamError.h"
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#include "llvm/Support/Endian.h"
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#include "llvm/Support/Error.h"
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#include <cstdint>
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namespace llvm {
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enum BinaryStreamFlags {
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BSF_None = 0,
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BSF_Write = 1, // Stream supports writing.
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BSF_Append = 2, // Writing can occur at offset == length.
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LLVM_MARK_AS_BITMASK_ENUM(/* LargestValue = */ BSF_Append)
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};
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/// An interface for accessing data in a stream-like format, but which
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/// discourages copying. Instead of specifying a buffer in which to copy
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/// data on a read, the API returns an ArrayRef to data owned by the stream's
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/// implementation. Since implementations may not necessarily store data in a
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/// single contiguous buffer (or even in memory at all), in such cases a it may
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/// be necessary for an implementation to cache such a buffer so that it can
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/// return it.
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class BinaryStream {
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public:
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virtual ~BinaryStream() = default;
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virtual llvm::support::endianness getEndian() const = 0;
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/// Given an offset into the stream and a number of bytes, attempt to
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/// read the bytes and set the output ArrayRef to point to data owned by the
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/// stream.
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virtual Error readBytes(uint32_t Offset, uint32_t Size,
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ArrayRef<uint8_t> &Buffer) = 0;
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/// Given an offset into the stream, read as much as possible without
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/// copying any data.
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virtual Error readLongestContiguousChunk(uint32_t Offset,
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ArrayRef<uint8_t> &Buffer) = 0;
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/// Return the number of bytes of data in this stream.
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virtual uint32_t getLength() = 0;
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/// Return the properties of this stream.
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virtual BinaryStreamFlags getFlags() const { return BSF_None; }
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protected:
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Error checkOffsetForRead(uint32_t Offset, uint32_t DataSize) {
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if (Offset > getLength())
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return make_error<BinaryStreamError>(stream_error_code::invalid_offset);
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if (getLength() < DataSize + Offset)
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return make_error<BinaryStreamError>(stream_error_code::stream_too_short);
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return Error::success();
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}
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};
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/// A BinaryStream which can be read from as well as written to. Note
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/// that writing to a BinaryStream always necessitates copying from the input
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/// buffer to the stream's backing store. Streams are assumed to be buffered
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/// so that to be portable it is necessary to call commit() on the stream when
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/// all data has been written.
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class WritableBinaryStream : public BinaryStream {
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public:
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~WritableBinaryStream() override = default;
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/// Attempt to write the given bytes into the stream at the desired
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/// offset. This will always necessitate a copy. Cannot shrink or grow the
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/// stream, only writes into existing allocated space.
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virtual Error writeBytes(uint32_t Offset, ArrayRef<uint8_t> Data) = 0;
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/// For buffered streams, commits changes to the backing store.
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virtual Error commit() = 0;
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/// Return the properties of this stream.
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BinaryStreamFlags getFlags() const override { return BSF_Write; }
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protected:
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Error checkOffsetForWrite(uint32_t Offset, uint32_t DataSize) {
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if (!(getFlags() & BSF_Append))
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return checkOffsetForRead(Offset, DataSize);
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if (Offset > getLength())
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return make_error<BinaryStreamError>(stream_error_code::invalid_offset);
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return Error::success();
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}
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};
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} // end namespace llvm
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#endif // LLVM_SUPPORT_BINARYSTREAM_H
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