Attribute Macro binrw::writer

#[writer]

Attribute macro used to generate write_with functions.

Rust functions are transformed by this macro to match the binrw API.

Attribute options

• #[writer(writer)] or #[writer(writer: $ident)]: Exposes the write stream to the function. If no variable name is given, writer is used.
• #[writer(endian)] or #[writer(endian: $ident)]: Exposes the endianness to the function. If no variable name is given, endian is used.

Options are comma-separated.

Function parameters

The first parameter is required and receives a reference to the object being written.

Subsequent parameters are transformed into either tuple-style arguments or raw arguments depending upon the function signature.

Tuple-style arguments

Use a normal function signature. The remaining parameters in the signature will be converted to a tuple. For example:

#[binrw::writer(writer: w, endian)]
fn custom_writer(obj: &Object, v0: u8, v1: i16) -> binrw::BinResult<()> {
    Ok(())
}

The transformed output for this function is:

use binrw::{BinResult, Endian, io::{Seek, Write}};
fn custom_writer<W: Write + Seek>(
    obj: &Object,
    w: &mut W,
    endian: Endian,
    (v0, v1): (u8, i16)
) -> BinResult<()> {
    Ok(())
}

Raw arguments

Use a variadic function signature with a second parameter. The name and type of the second parameter will be used as the raw argument. For example:

#[binrw::writer]
fn custom_writer(obj: &Object, args: ArgsType, ...) -> binrw::BinResult<()> {
    Ok(())
}

The transformed output for this function is:

use binrw::{BinResult, Endian, io::{Seek, Write}};
fn custom_writer<W: Write + Seek>(
    obj: &Object,
    _: &mut W,
    _: Endian,
    args: ArgsType
) -> BinResult<()> {
    Ok(())
}

Return value

The return value of a writer function must be BinResult<()>.