1 //===- MsgPackReader.h - Simple MsgPack reader ------------------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 /// 9 /// \file 10 /// This is a MessagePack reader. 11 /// 12 /// See https://github.com/msgpack/msgpack/blob/master/spec.md for the full 13 /// standard. 14 /// 15 /// Typical usage: 16 /// \code 17 /// StringRef input = GetInput(); 18 /// msgpack::Reader MPReader(input); 19 /// msgpack::Object Obj; 20 /// 21 /// while (MPReader.read(Obj)) { 22 /// switch (Obj.Kind) { 23 /// case msgpack::Type::Int: 24 // // Use Obj.Int 25 /// break; 26 /// // ... 27 /// } 28 /// } 29 /// \endcode 30 /// 31 //===----------------------------------------------------------------------===// 32 33 #ifndef LLVM_SUPPORT_MSGPACKREADER_H 34 #define LLVM_SUPPORT_MSGPACKREADER_H 35 36 #include "llvm/Support/MemoryBuffer.h" 37 #include "llvm/Support/raw_ostream.h" 38 #include <cstdint> 39 40 namespace llvm { 41 namespace msgpack { 42 43 /// MessagePack types as defined in the standard, with the exception of Integer 44 /// being divided into a signed Int and unsigned UInt variant in order to map 45 /// directly to C++ types. 46 /// 47 /// The types map onto corresponding union members of the \c Object struct. 48 enum class Type : uint8_t { 49 Int, 50 UInt, 51 Nil, 52 Boolean, 53 Float, 54 String, 55 Binary, 56 Array, 57 Map, 58 Extension, 59 }; 60 61 /// Extension types are composed of a user-defined type ID and an uninterpreted 62 /// sequence of bytes. 63 struct ExtensionType { 64 /// User-defined extension type. 65 int8_t Type; 66 /// Raw bytes of the extension object. 67 StringRef Bytes; 68 }; 69 70 /// MessagePack object, represented as a tagged union of C++ types. 71 /// 72 /// All types except \c Type::Nil (which has only one value, and so is 73 /// completely represented by the \c Kind itself) map to a exactly one union 74 /// member. 75 struct Object { 76 Type Kind; 77 union { 78 /// Value for \c Type::Int. 79 int64_t Int; 80 /// Value for \c Type::Uint. 81 uint64_t UInt; 82 /// Value for \c Type::Boolean. 83 bool Bool; 84 /// Value for \c Type::Float. 85 double Float; 86 /// Value for \c Type::String and \c Type::Binary. 87 StringRef Raw; 88 /// Value for \c Type::Array and \c Type::Map. 89 size_t Length; 90 /// Value for \c Type::Extension. 91 ExtensionType Extension; 92 }; 93 ObjectObject94 Object() : Kind(Type::Int), Int(0) {} 95 }; 96 97 /// Reads MessagePack objects from memory, one at a time. 98 class Reader { 99 public: 100 /// Construct a reader, keeping a reference to the \p InputBuffer. 101 Reader(MemoryBufferRef InputBuffer); 102 /// Construct a reader, keeping a reference to the \p Input. 103 Reader(StringRef Input); 104 105 Reader(const Reader &) = delete; 106 Reader &operator=(const Reader &) = delete; 107 108 /// Read one object from the input buffer, advancing past it. 109 /// 110 /// The \p Obj is updated with the kind of the object read, and the 111 /// corresponding union member is updated. 112 /// 113 /// For the collection objects (Array and Map), only the length is read, and 114 /// the caller must make and additional \c N calls (in the case of Array) or 115 /// \c N*2 calls (in the case of Map) to \c Read to retrieve the collection 116 /// elements. 117 /// 118 /// \param [out] Obj filled with next object on success. 119 /// 120 /// \returns true when object successfully read, false when at end of 121 /// input (and so \p Obj was not updated), otherwise an error. 122 Expected<bool> read(Object &Obj); 123 124 private: 125 MemoryBufferRef InputBuffer; 126 StringRef::iterator Current; 127 StringRef::iterator End; 128 remainingSpace()129 size_t remainingSpace() { 130 // The rest of the code maintains the invariant that End >= Current, so 131 // that this cast is always defined behavior. 132 return static_cast<size_t>(End - Current); 133 } 134 135 template <class T> Expected<bool> readRaw(Object &Obj); 136 template <class T> Expected<bool> readInt(Object &Obj); 137 template <class T> Expected<bool> readUInt(Object &Obj); 138 template <class T> Expected<bool> readLength(Object &Obj); 139 template <class T> Expected<bool> readExt(Object &Obj); 140 Expected<bool> createRaw(Object &Obj, uint32_t Size); 141 Expected<bool> createExt(Object &Obj, uint32_t Size); 142 }; 143 144 } // end namespace msgpack 145 } // end namespace llvm 146 147 #endif // LLVM_SUPPORT_MSGPACKREADER_H 148