Structure Language (StructLang)

StructLang is a data specification language used within the scope of this project. It uses a syntax similar to Rust and C to mathematically specify a syntax for binary data.

Comments

Comments begin with a // and continue until the end of the line. Alternatively, a comment block which begins with /* and ends with */ can be used.

Settings

Some global settings may be necessary to write a proper specification.

Syntax

set = "set" identifier "=" value;

Examples

set byte_bits = 32
set default_byte_order = big_endian
set default_signed_representation = twos_complement

List of Settings

Identifier	Type	Description
byte_bits	unsigned integer	number of bits in one byte
default_byte_order	modifier	default byte order (endianness) of types
default_signed_representation	modifier	default representation of signed integers

Type Definitions

Definitions define data types.

Syntax

def = "def" type "=" {modifier} base_type;

• type is the identifier of the type
• modifier a type modifier
• base_type the base type which this type is specializing

Example

def i32 = signed 32_bit twos_complement integer
def u8 = unsigned 8_bit integer
def string = null_terminated u8[]

Arrays

Arrays are blocks of one type which are stored using a single variable.

Syntax

array_type = type "[" size | "" "]";

Examples

u8[4096] buffer     // a constant-sized array

u32 size
u8[size] var_buffer // a variable-sized array

u8[] endless_buffer // an array which extends until the end of the data

Structures

Defines a structure of other types. These types can also be structures. The first (uppermost) type in a struct is also the first element in the serialized data.

Syntax

struct = "struct" identifier "{"
    type identifier
    ...
"}";

Example

struct Color {
    u8 red
    u8 green
    u8 blue
}

Enumerations

Defines a list of constants of some type.

Syntax

enum = "enum", identifier, ":", type, "{",
    {identifier, "=", value},
"}";

Examples

enum Size : string {
    SMALL = "S"
    MEDIUM = "M"
    LARGE = "L"
    EXTRA_LARGE = "XL"
}

enum ArgbColor : u32 {
    RED   = 0xffff0000
    GREEN = 0xff00ff00
    BLUE  = 0xff0000ff
}

Templated Structures

Sometimes a structure depends on content found in a header or other structures. Templates can change how a structure is laid out using variables.

Syntax

struct = "struct" type "<" type {identifier ","} ">" "{"
    ...
"}";

Example

struct varint<u8 bits> {
    if bits == 8 {
        u8 data
    }
    else if bits == 16 {
        u16 data
    }
    else if bits == 32 {
        u32 data
    }
    else {
        error "Invalid bits variable"
    }
}