Advanced Usage

Advanced Usage

Now that you've gone through the quickstart tutorial, here is a more fleshed out guide on the details of this library.

Constraints & Limitations

Unsigned Integers

The user must be aware that Fortran does not support unsigned integers, while MessagePack uses them routinely in its specification. This library has utilities to deal with them, but in specific circumstances the user must deal with them on their own. See the Integer Format Family for more details.

The binary & extension format family store values with the signed byte type, whereas they are truly unsigned.

Endianness

The msgpack class will attempt to identify whether the host system is little endian or big endian during run-time. This library does not support other endian architectures.

Extensions

This library supports the timestamp format, and custom user extensions via registration of callbacks.

Data Structures & Format Families

All data types extend from mp_value_type. mp_arr_type and mp_map_type rely on mp_value_type_ptr to store messagepack values of any kind.

type :: mp_value_type_ptr
    class(mp_value_type), allocatable :: obj
end type

messagepack exports these logical functions for checking which format family that a mp_value_type object truly is:

function is_nil(obj) result(res) ! @returns whether the object is `mp_nil_type`
function is_bool(obj) result(res) ! @returns whether the object is `mp_bool_type`
function is_int(obj) result(res) ! @returns whether the object is a `mp_int_type`
function is_float(obj) result(res) ! @returns whether the object is a `mp_float_type`
function is_str(obj) result(res) ! @returns whether the object is a `mp_str_type`
function is_bin(obj) result(res) ! @returns whether the object is a `mp_bin_type`
function is_arr(obj) result(res) ! @returns whether the object is a `mp_arr_type`
function is_map(obj) result(res) ! @returns whether the object is a `mp_map_type`
function is_ext(obj) result(res) ! @returns whether the object is a `mp_ext_type`
function is_timestamp(obj) result(res) ! @returns whether the object is a `mp_timestamp_type`

Nil Format Family

type, extends(mp_value_type) :: mp_nil_type
    ! nothing here
    ...
end type

Bool Format Family

type, extends(mp_value_type) :: mp_bool_type
    logical :: value
    ...
end type

Integer Format Family

type, extends(mp_value_type) :: mp_int_type
    integer(kind=int64) :: value
    logical :: unsigned_64 = .false.
    ...
end type

Float Format Family

type, extends(mp_value_type) :: mp_float_type
    real(kind=real64) :: f64value
    real(kind=real32) :: f32value
    logical :: is_64 = .true.
    ...
end type

String Format Family

type, extends(mp_value_type) :: mp_str_type
    character(:), allocatable :: value
    ...
end type

Bin Format Family

type, extends(mp_value_type) :: mp_bin_type
    byte, allocatable, dimension(:) :: values
    ...
end type

Array Format Family

type, extends(mp_value_type) :: mp_arr_type
    class(mp_value_type_ptr), allocatable, dimension(:) :: values
    ...
end type

Map Format Family

type, extends(mp_value_type) :: mp_map_type
    class(mp_value_type_ptr), allocatable, dimension(:) :: keys
    class(mp_value_type_ptr), allocatable, dimension(:) :: values
    integer(kind=int64) :: ne
    ...
end type

Ext Format Family

type, extends(mp_value_type) :: mp_ext_type
    integer :: exttype
    byte, allocatable, dimension(:) :: values
    ...
end type

Timestamp Format Family

type, extends(mp_value_type) :: mp_timestamp_type
    integer(kind=int64) :: seconds
    integer(kind=int64) :: nanoseconds
    ...
end type