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| Rev | Author | Line No. | Line |
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| 14 | pmbaty | 1 | //===- BinaryItemStream.h ---------------------------------------*- 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_BINARYITEMSTREAM_H |
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| 10 | #define LLVM_SUPPORT_BINARYITEMSTREAM_H |
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| 11 | |||
| 12 | #include "llvm/ADT/ArrayRef.h" |
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| 13 | #include "llvm/Support/BinaryStream.h" |
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| 14 | #include "llvm/Support/BinaryStreamError.h" |
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| 15 | #include "llvm/Support/Error.h" |
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| 16 | #include <cstddef> |
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| 17 | #include <cstdint> |
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| 18 | |||
| 19 | namespace llvm { |
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| 20 | |||
| 21 | template <typename T> struct BinaryItemTraits { |
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| 22 | static size_t length(const T &Item) = delete; |
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| 23 | static ArrayRef<uint8_t> bytes(const T &Item) = delete; |
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| 24 | }; |
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| 25 | |||
| 26 | /// BinaryItemStream represents a sequence of objects stored in some kind of |
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| 27 | /// external container but for which it is useful to view as a stream of |
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| 28 | /// contiguous bytes. An example of this might be if you have a collection of |
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| 29 | /// records and you serialize each one into a buffer, and store these serialized |
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| 30 | /// records in a container. The pointers themselves are not laid out |
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| 31 | /// contiguously in memory, but we may wish to read from or write to these |
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| 32 | /// records as if they were. |
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| 33 | template <typename T, typename Traits = BinaryItemTraits<T>> |
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| 34 | class BinaryItemStream : public BinaryStream { |
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| 35 | public: |
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| 36 | explicit BinaryItemStream(llvm::support::endianness Endian) |
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| 37 | : Endian(Endian) {} |
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| 38 | |||
| 39 | llvm::support::endianness getEndian() const override { return Endian; } |
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| 40 | |||
| 41 | Error readBytes(uint64_t Offset, uint64_t Size, |
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| 42 | ArrayRef<uint8_t> &Buffer) override { |
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| 43 | auto ExpectedIndex = translateOffsetIndex(Offset); |
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| 44 | if (!ExpectedIndex) |
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| 45 | return ExpectedIndex.takeError(); |
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| 46 | const auto &Item = Items[*ExpectedIndex]; |
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| 47 | if (auto EC = checkOffsetForRead(Offset, Size)) |
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| 48 | return EC; |
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| 49 | if (Size > Traits::length(Item)) |
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| 50 | return make_error<BinaryStreamError>(stream_error_code::stream_too_short); |
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| 51 | Buffer = Traits::bytes(Item).take_front(Size); |
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| 52 | return Error::success(); |
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| 53 | } |
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| 54 | |||
| 55 | Error readLongestContiguousChunk(uint64_t Offset, |
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| 56 | ArrayRef<uint8_t> &Buffer) override { |
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| 57 | auto ExpectedIndex = translateOffsetIndex(Offset); |
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| 58 | if (!ExpectedIndex) |
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| 59 | return ExpectedIndex.takeError(); |
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| 60 | Buffer = Traits::bytes(Items[*ExpectedIndex]); |
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| 61 | return Error::success(); |
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| 62 | } |
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| 63 | |||
| 64 | void setItems(ArrayRef<T> ItemArray) { |
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| 65 | Items = ItemArray; |
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| 66 | computeItemOffsets(); |
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| 67 | } |
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| 68 | |||
| 69 | uint64_t getLength() override { |
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| 70 | return ItemEndOffsets.empty() ? 0 : ItemEndOffsets.back(); |
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| 71 | } |
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| 72 | |||
| 73 | private: |
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| 74 | void computeItemOffsets() { |
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| 75 | ItemEndOffsets.clear(); |
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| 76 | ItemEndOffsets.reserve(Items.size()); |
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| 77 | uint64_t CurrentOffset = 0; |
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| 78 | for (const auto &Item : Items) { |
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| 79 | uint64_t Len = Traits::length(Item); |
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| 80 | assert(Len > 0 && "no empty items"); |
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| 81 | CurrentOffset += Len; |
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| 82 | ItemEndOffsets.push_back(CurrentOffset); |
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| 83 | } |
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| 84 | } |
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| 85 | |||
| 86 | Expected<uint32_t> translateOffsetIndex(uint64_t Offset) { |
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| 87 | // Make sure the offset is somewhere in our items array. |
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| 88 | if (Offset >= getLength()) |
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| 89 | return make_error<BinaryStreamError>(stream_error_code::stream_too_short); |
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| 90 | ++Offset; |
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| 91 | auto Iter = llvm::lower_bound(ItemEndOffsets, Offset); |
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| 92 | size_t Idx = std::distance(ItemEndOffsets.begin(), Iter); |
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| 93 | assert(Idx < Items.size() && "binary search for offset failed"); |
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| 94 | return Idx; |
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| 95 | } |
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| 96 | |||
| 97 | llvm::support::endianness Endian; |
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| 98 | ArrayRef<T> Items; |
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| 99 | |||
| 100 | // Sorted vector of offsets to accelerate lookup. |
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| 101 | std::vector<uint64_t> ItemEndOffsets; |
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| 102 | }; |
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| 103 | |||
| 104 | } // end namespace llvm |
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| 105 | |||
| 106 | #endif // LLVM_SUPPORT_BINARYITEMSTREAM_H |