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