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//===- MsgPackReader.h - Simple MsgPack reader ------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// \file
/// This is a MessagePack reader.
///
/// See https://github.com/msgpack/msgpack/blob/master/spec.md for the full
/// standard.
///
/// Typical usage:
/// \code
/// StringRef input = GetInput();
/// msgpack::Reader MPReader(input);
/// msgpack::Object Obj;
///
/// while (true) {
/// Expected<bool> ReadObj = MPReader.read(&Obj);
/// if (!ReadObj)
/// // Handle error...
/// if (!ReadObj.get())
/// break; // Reached end of input
/// switch (Obj.Kind) {
/// case msgpack::Type::Int:
// // Use Obj.Int
/// break;
/// // ...
/// }
/// }
/// \endcode
///
//===----------------------------------------------------------------------===//
#ifndef LLVM_BINARYFORMAT_MSGPACKREADER_H
#define LLVM_BINARYFORMAT_MSGPACKREADER_H
#include "llvm/Support/Error.h"
#include "llvm/Support/MemoryBufferRef.h"
#include <cstdint>
namespace llvm {
namespace msgpack {
/// MessagePack types as defined in the standard, with the exception of Integer
/// being divided into a signed Int and unsigned UInt variant in order to map
/// directly to C++ types.
///
/// The types map onto corresponding union members of the \c Object struct.
enum class Type : uint8_t {
Int,
UInt,
Nil,
Boolean,
Float,
String,
Binary,
Array,
Map,
Extension,
Empty, // Used by MsgPackDocument to represent an empty node
};
/// Extension types are composed of a user-defined type ID and an uninterpreted
/// sequence of bytes.
struct ExtensionType {
/// User-defined extension type.
int8_t Type;
/// Raw bytes of the extension object.
StringRef Bytes;
};
/// MessagePack object, represented as a tagged union of C++ types.
///
/// All types except \c Type::Nil (which has only one value, and so is
/// completely represented by the \c Kind itself) map to a exactly one union
/// member.
struct Object {
Type Kind;
union {
/// Value for \c Type::Int.
int64_t Int;
/// Value for \c Type::Uint.
uint64_t UInt;
/// Value for \c Type::Boolean.
bool Bool;
/// Value for \c Type::Float.
double Float;
/// Value for \c Type::String and \c Type::Binary.
StringRef Raw;
/// Value for \c Type::Array and \c Type::Map.
size_t Length;
/// Value for \c Type::Extension.
ExtensionType Extension;
};
Object() : Kind(Type::Int), Int(0) {}
};
/// Reads MessagePack objects from memory, one at a time.
class Reader {
public:
/// Construct a reader, keeping a reference to the \p InputBuffer.
Reader(MemoryBufferRef InputBuffer);
/// Construct a reader, keeping a reference to the \p Input.
Reader(StringRef Input);
Reader(const Reader &) = delete;
Reader &operator=(const Reader &) = delete;
/// Read one object from the input buffer, advancing past it.
///
/// The \p Obj is updated with the kind of the object read, and the
/// corresponding union member is updated.
///
/// For the collection objects (Array and Map), only the length is read, and
/// the caller must make and additional \c N calls (in the case of Array) or
/// \c N*2 calls (in the case of Map) to \c Read to retrieve the collection
/// elements.
///
/// \param [out] Obj filled with next object on success.
///
/// \returns true when object successfully read, false when at end of
/// input (and so \p Obj was not updated), otherwise an error.
Expected<bool> read(Object &Obj);
private:
MemoryBufferRef InputBuffer;
StringRef::iterator Current;
StringRef::iterator End;
size_t remainingSpace() {
// The rest of the code maintains the invariant that End >= Current, so
// that this cast is always defined behavior.
return static_cast<size_t>(End - Current);
}
template <class T> Expected<bool> readRaw(Object &Obj);
template <class T> Expected<bool> readInt(Object &Obj);
template <class T> Expected<bool> readUInt(Object &Obj);
template <class T> Expected<bool> readLength(Object &Obj);
template <class T> Expected<bool> readExt(Object &Obj);
Expected<bool> createRaw(Object &Obj, uint32_t Size);
Expected<bool> createExt(Object &Obj, uint32_t Size);
};
} // end namespace msgpack
} // end namespace llvm
#endif // LLVM_BINARYFORMAT_MSGPACKREADER_H
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