An AMQP message body can hold binary data using any encoding you like. AMQP also defines its own encoding and types. The AMQP encoding is often used in message bodies because it is supported by AMQP libraries on many languages and platforms. You also need to use the AMQP types to set and examine message properties.

Scalar types

Each type is identified by a proton::type_id.

C++ type	AMQP type_id	Description
bool	proton::BOOLEAN	Boolean true or false
uint8_t	proton::UBYTE	8-bit unsigned byte
int8_t	proton::BYTE	8-bit signed byte
uint16_t	proton::USHORT	16-bit unsigned integer
int16_t	proton::SHORT	16-bit signed integer
uint32_t	proton::UINT	32-bit unsigned integer
int32_t	proton::INT	32-bit signed integer
uint64_t	proton::ULONG	64-bit unsigned integer
int64_t	proton::LONG	64-bit signed integer
wchar_t	proton::CHAR	32-bit unicode code point
float	proton::FLOAT	32-bit binary floating point
double	proton::DOUBLE	64-bit binary floating point
proton::timestamp	proton::TIMESTAMP	64-bit signed milliseconds since 00:00:00 (UTC), 1 January 1970.
proton::decimal32	proton::DECIMAL32	32-bit decimal floating point
proton::decimal64	proton::DECIMAL64	64-bit decimal floating point
proton::decimal128	proton::DECIMAL128	128-bit decimal floating point
proton::uuid	proton::UUID	128-bit universally-unique identifier
std::string	proton::STRING	UTF-8 encoded Unicode string
proton::symbol	proton::SYMBOL	7-bit ASCII encoded string
proton::binary	proton::BINARY	Variable-length binary data

Holder types

proton::message::body() and other message-related data can contain different types of data at runtime. There are two "holder" types provided to hold runtime typed data:

proton::scalar can hold a scalar value of any type.
proton::value can hold any AMQP value, scalar or compound.

You can set the value in a holder by assignment, and use the proton::get() and proton::coerce() templates to extract data in a type-safe way. Holders also provide functions to query the type of value they contain.

Compound types

C++ type	AMQP type_id	Description
See below	proton::ARRAY	Sequence of values of the same type
See below	proton::LIST	Sequence of values of mixed types
See below	proton::MAP	Map of key-value pairs

A proton::value containing a proton::ARRAY can convert to and from C++ sequences of the corresponding C++ type: std::vector, std::deque, std::list, and std::forward_list.

proton::LIST converts to and from sequences of proton::value or proton::scalar, which can hold mixed types of data.

proton::MAP converts to and from std::map, std::unordered_map, and sequences of std::pair.

For example, you can decode a message body with any AMQP map as follows.

proton::message m = ...;
std::map<proton::value, proton::value> map;
proton::get(m.body(), map);

You can encode a message body with a map of string keys and uint64_t values like this:

std::unordered_map<std::string, uint64_t> map;
map["foo"] = 123;
m.body() = map;

Include files

proton/types.hpp includes all available type definitions and conversions. Alternatively, you can selectively include the .hpp files you want.