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_BINARYFORMAT_MSGPACKREADER_H
34#define LLVM_BINARYFORMAT_MSGPACKREADER_H
35
36#include "llvm/Support/Error.h"
37#include "llvm/Support/MemoryBuffer.h"
38#include "llvm/Support/raw_ostream.h"
39#include <cstdint>
40
41namespace llvm {
42namespace msgpack {
43
44/// MessagePack types as defined in the standard, with the exception of Integer
45/// being divided into a signed Int and unsigned UInt variant in order to map
46/// directly to C++ types.
47///
48/// The types map onto corresponding union members of the \c Object struct.
49enum class Type : uint8_t {
50 Int,
51 UInt,
52 Nil,
53 Boolean,
54 Float,
55 String,
56 Binary,
57 Array,
58 Map,
59 Extension,
60 Empty, // Used by MsgPackDocument to represent an empty node
61};
62
63/// Extension types are composed of a user-defined type ID and an uninterpreted
64/// sequence of bytes.
65struct ExtensionType {
66 /// User-defined extension type.
67 int8_t Type;
68 /// Raw bytes of the extension object.
69 StringRef Bytes;
70};
71
72/// MessagePack object, represented as a tagged union of C++ types.
73///
74/// All types except \c Type::Nil (which has only one value, and so is
75/// completely represented by the \c Kind itself) map to a exactly one union
76/// member.
77struct Object {
78 Type Kind;
79 union {
80 /// Value for \c Type::Int.
81 int64_t Int;
82 /// Value for \c Type::Uint.
83 uint64_t UInt;
84 /// Value for \c Type::Boolean.
85 bool Bool;
86 /// Value for \c Type::Float.
87 double Float;
88 /// Value for \c Type::String and \c Type::Binary.
89 StringRef Raw;
90 /// Value for \c Type::Array and \c Type::Map.
91 size_t Length;
92 /// Value for \c Type::Extension.
93 ExtensionType Extension;
94 };
95
96 Object() : Kind(Type::Int), Int(0) {}
97};
98
99/// Reads MessagePack objects from memory, one at a time.
100class Reader {
101public:
102 /// Construct a reader, keeping a reference to the \p InputBuffer.
103 Reader(MemoryBufferRef InputBuffer);
104 /// Construct a reader, keeping a reference to the \p Input.
105 Reader(StringRef Input);
106
107 Reader(const Reader &) = delete;
108 Reader &operator=(const Reader &) = delete;
109
110 /// Read one object from the input buffer, advancing past it.
111 ///
112 /// The \p Obj is updated with the kind of the object read, and the
113 /// corresponding union member is updated.
114 ///
115 /// For the collection objects (Array and Map), only the length is read, and
116 /// the caller must make and additional \c N calls (in the case of Array) or
117 /// \c N*2 calls (in the case of Map) to \c Read to retrieve the collection
118 /// elements.
119 ///
120 /// \param [out] Obj filled with next object on success.
121 ///
122 /// \returns true when object successfully read, false when at end of
123 /// input (and so \p Obj was not updated), otherwise an error.
124 Expected<bool> read(Object &Obj);
125
126private:
127 MemoryBufferRef InputBuffer;
128 StringRef::iterator Current;
129 StringRef::iterator End;
130
131 size_t remainingSpace() {
132 // The rest of the code maintains the invariant that End >= Current, so
133 // that this cast is always defined behavior.
134 return static_cast<size_t>(End - Current);
135 }
136
137 template <class T> Expected<bool> readRaw(Object &Obj);
138 template <class T> Expected<bool> readInt(Object &Obj);
139 template <class T> Expected<bool> readUInt(Object &Obj);
140 template <class T> Expected<bool> readLength(Object &Obj);
141 template <class T> Expected<bool> readExt(Object &Obj);
142 Expected<bool> createRaw(Object &Obj, uint32_t Size);
143 Expected<bool> createExt(Object &Obj, uint32_t Size);
144};
145
146} // end namespace msgpack
147} // end namespace llvm
148
149#endif // LLVM_BINARYFORMAT_MSGPACKREADER_H
150