FFI

Types for safe Foreign Function Interface interoperability.

All types live under the FFI namespace (re-exported from std::ffi/cstring).

Types

Type	Source file	Description
`FFI::CString`	cstring.ign	Owned, NUL-terminated C string with RAII cleanup
`FFI::NulError`	cstring.ign	Error: input contained interior NUL bytes

CString vs String vs str

Type	Ownership	NUL-terminated	Interior NULs	Use Case
`str`	Borrowed	Yes (contract)	Allowed	String literals
`String`	Owned	Yes (runtime)	Allowed	General-purpose
`FFI::CString`	Owned	Yes (guaranteed)	Prohibited	FFI, C interop

Safety

FFI::CString guarantees:

No interior NUL bytes (checked at construction)
Always NUL-terminated
Owned buffer freed automatically on drop

Example

import FFI from "std::ffi";
import LibC from "std::libc";
import Result from "std::result";

function main(): i32 {
  let result: Result<FFI::CString, FFI::NulError> = FFI::CString::new("/tmp/file.txt");

  if (result.isOk()) {
    let cstr: FFI::CString = result.unwrap();
    let ptr: LibC::CType::CConstStr = cstr.asStr();
    // Pass ptr to C function expecting const char*
    return 0;
  }

  return 1;
}