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Mojo Writer

The Mojo writer (headerkit.writers.mojo) generates idiomatic Mojo bindings with sys.ffi.DLHandle and CShim bridge support for consuming C and C++ libraries from Modular's Mojo language.

Features

  • Standard C FFI with sys.ffi.DLHandle: Generates a dynamic library wrapper struct with typed method signatures for loaded shared objects (.so, .dylib, .dll).
  • Mojo Type Mappings: Automatically maps C primitives and pointers to Mojo equivalents (Int32, UInt64, Float32, Float64, Bool, Int, UnsafePointer[T], UnsafePointer[NoneType]).
  • Structs & Enums: Emits C-compatible @value @register_passable("trivial") struct types.
  • C++ CShim Bridge: Bridges C++ classes shimmed via Headerkit's C-ABI shims into high-level Mojo OOP wrapper structs with constructor, destructor, and method forwarders.
  • Identifier Escaping: Automatically escapes reserved Mojo keywords (fn, var, struct, let, mut, inout, etc.).

Usage

headerkit mylib.h -w mojo -o mojo:mylib.mojo

from headerkit.writers import get_writer

writer = get_writer("mojo", library_name="FastMath")
mojo_code = writer.write(unit)

Example Output

Given a C header:

typedef struct {
    float x;
    float y;
} Point;

int add(int a, int b);

The Mojo writer produces:

# Auto-generated Mojo bindings by HeaderKit
from sys.ffi import DLHandle
from memory import UnsafePointer

@value
@register_passable("trivial")
struct Point:
    var x: Float32
    var y: Float32

struct Library:
    var handle: DLHandle

    fn __init__(out self, path: String) raises:
        self.handle = DLHandle(path)

    fn close(mut self):
        self.handle.close()

    fn add(self, a: Int32, b: Int32) -> Int32:
        var f = self.handle.get_function[fn(Int32, Int32) -> Int32]("add")
        return f(a, b)

API Reference

MojoWriter 

MojoWriter(*, library_name='Library', emit_classes=True)

Bases: BaseWriter

Writer that generates Mojo FFI bindings with sys.ffi.DLHandle and CShim support.

write_mojo 

write_mojo(header, *, library_name='Library', emit_classes=True)

Convenience function to generate Mojo bindings from Headerkit IR.