Iota is the IDL and compiler of Sigma

Compiler

The iota compiler is iota.py and an example call looks like

python3 iota.py /path/to/some/idl/file.xml --generator cpp -o /path/to/some/header.hpp

Which will take /path/to/some/idl/file.xml and generate a C++ header in /path/to/some/header.hpp

IDL

The IDL is written in XML

The root node is a <iota> node with 2 required attributes version which describes the language version and module which describes the module it is in

An example is

<iota version="0.0.1" module="foo.bar">

Under the root node various <message> nodes exist which describe a message, it has 1 attribute name which tells us the name of the module

An example node would be

<message name="baz">

Under said <message> nodes <field> nodes exist which describe the varies entries in a message. It has 1 attribute type which has the following possible values:

• int8
• uint8
• int16
• uint16
• int32
• uint32
• int64
• uint64
• buffer: Array of uint8's
• string: Array of ASCII characters
• list: Array of uint64's

And in between the <field> and </field> nodes the name is placed

Under the root node various <enum> nodes can exist which describe an enumeration, it has 2 attributes name which tells us the name of the module and type which tells us the name of the enumeration

Possible types are

• int8
• uint8
• int16
• uint16
• int32
• uint32
• int64
• uint64

An example node would be

<enum name="baz" type="int32">

Under said <enum> nodes <entry> nodes exist which describe the varies entries in a enum. It has 1 attribute value which is the value of the entry

And in between the <field> and </field> nodes the name is placed

This makes for the following example node

<entry value="2">myEnumEntry</entry>

All together

In this way we can create an example IDL file

<iota version="0.0.1" module="foo">
    <enum name="request" type="uint8">
        <entry value="0">nop</entry>
        <entry value="1">open</entry>
        <entry value="2">close</entry>
    </enum>

    <message name="bar">
        <field type="uint64">test</field>
        <field type="uint32">abc</field>
        <field type="buffer">buf</field>
    </message>
</iota>

for other examples look in the examples/ directory