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| Rev | Author | Line No. | Line |
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| 14 | pmbaty | 1 | //===- BinaryStream.h - Base interface for a stream of data -----*- C++ -*-===// |
| 2 | // |
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| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
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| 4 | // See https://llvm.org/LICENSE.txt for license information. |
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| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
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| 6 | // |
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| 7 | //===----------------------------------------------------------------------===// |
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| 8 | |||
| 9 | #ifndef LLVM_SUPPORT_BINARYSTREAM_H |
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| 10 | #define LLVM_SUPPORT_BINARYSTREAM_H |
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| 11 | |||
| 12 | #include "llvm/ADT/ArrayRef.h" |
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| 13 | #include "llvm/ADT/BitmaskEnum.h" |
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| 14 | #include "llvm/Support/BinaryStreamError.h" |
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| 15 | #include "llvm/Support/Endian.h" |
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| 16 | #include "llvm/Support/Error.h" |
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| 17 | #include <cstdint> |
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| 18 | |||
| 19 | namespace llvm { |
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| 20 | |||
| 21 | enum BinaryStreamFlags { |
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| 22 | BSF_None = 0, |
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| 23 | BSF_Write = 1, // Stream supports writing. |
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| 24 | BSF_Append = 2, // Writing can occur at offset == length. |
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| 25 | LLVM_MARK_AS_BITMASK_ENUM(/* LargestValue = */ BSF_Append) |
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| 26 | }; |
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| 27 | |||
| 28 | /// An interface for accessing data in a stream-like format, but which |
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| 29 | /// discourages copying. Instead of specifying a buffer in which to copy |
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| 30 | /// data on a read, the API returns an ArrayRef to data owned by the stream's |
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| 31 | /// implementation. Since implementations may not necessarily store data in a |
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| 32 | /// single contiguous buffer (or even in memory at all), in such cases a it may |
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| 33 | /// be necessary for an implementation to cache such a buffer so that it can |
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| 34 | /// return it. |
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| 35 | class BinaryStream { |
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| 36 | public: |
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| 37 | virtual ~BinaryStream() = default; |
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| 38 | |||
| 39 | virtual llvm::support::endianness getEndian() const = 0; |
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| 40 | |||
| 41 | /// Given an offset into the stream and a number of bytes, attempt to |
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| 42 | /// read the bytes and set the output ArrayRef to point to data owned by the |
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| 43 | /// stream. |
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| 44 | virtual Error readBytes(uint64_t Offset, uint64_t Size, |
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| 45 | ArrayRef<uint8_t> &Buffer) = 0; |
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| 46 | |||
| 47 | /// Given an offset into the stream, read as much as possible without |
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| 48 | /// copying any data. |
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| 49 | virtual Error readLongestContiguousChunk(uint64_t Offset, |
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| 50 | ArrayRef<uint8_t> &Buffer) = 0; |
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| 51 | |||
| 52 | /// Return the number of bytes of data in this stream. |
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| 53 | virtual uint64_t getLength() = 0; |
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| 54 | |||
| 55 | /// Return the properties of this stream. |
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| 56 | virtual BinaryStreamFlags getFlags() const { return BSF_None; } |
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| 57 | |||
| 58 | protected: |
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| 59 | Error checkOffsetForRead(uint64_t Offset, uint64_t DataSize) { |
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| 60 | if (Offset > getLength()) |
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| 61 | return make_error<BinaryStreamError>(stream_error_code::invalid_offset); |
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| 62 | if (getLength() < DataSize + Offset) |
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| 63 | return make_error<BinaryStreamError>(stream_error_code::stream_too_short); |
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| 64 | return Error::success(); |
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| 65 | } |
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| 66 | }; |
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| 67 | |||
| 68 | /// A BinaryStream which can be read from as well as written to. Note |
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| 69 | /// that writing to a BinaryStream always necessitates copying from the input |
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| 70 | /// buffer to the stream's backing store. Streams are assumed to be buffered |
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| 71 | /// so that to be portable it is necessary to call commit() on the stream when |
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| 72 | /// all data has been written. |
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| 73 | class WritableBinaryStream : public BinaryStream { |
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| 74 | public: |
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| 75 | ~WritableBinaryStream() override = default; |
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| 76 | |||
| 77 | /// Attempt to write the given bytes into the stream at the desired |
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| 78 | /// offset. This will always necessitate a copy. Cannot shrink or grow the |
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| 79 | /// stream, only writes into existing allocated space. |
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| 80 | virtual Error writeBytes(uint64_t Offset, ArrayRef<uint8_t> Data) = 0; |
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| 81 | |||
| 82 | /// For buffered streams, commits changes to the backing store. |
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| 83 | virtual Error commit() = 0; |
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| 84 | |||
| 85 | /// Return the properties of this stream. |
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| 86 | BinaryStreamFlags getFlags() const override { return BSF_Write; } |
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| 87 | |||
| 88 | protected: |
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| 89 | Error checkOffsetForWrite(uint64_t Offset, uint64_t DataSize) { |
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| 90 | if (!(getFlags() & BSF_Append)) |
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| 91 | return checkOffsetForRead(Offset, DataSize); |
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| 92 | |||
| 93 | if (Offset > getLength()) |
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| 94 | return make_error<BinaryStreamError>(stream_error_code::invalid_offset); |
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| 95 | return Error::success(); |
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| 96 | } |
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| 97 | }; |
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| 98 | |||
| 99 | } // end namespace llvm |
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| 100 | |||
| 101 | #endif // LLVM_SUPPORT_BINARYSTREAM_H |