D & ruby: std.stdio

readfile.d

import std.stdio;

import core.runtime;
extern(C) void lib_init() {
    Runtime.initialize();
}

import std.conv;
import std.string;
import core.memory;
import std.c.stdlib;

extern(C) void* file_open(const char* filename) {
    File* f = cast(File*)malloc(File.sizeof);
    emplace(f, to!string(filename));
    GC.addRange(f, File.sizeof);
    return f;
}

extern(C) void file_close(File* f) {
    f.close();
    GC.removeRange(f);
    free(cast(void*)f);
}

extern(C) immutable(char)* file_readln(File* f) {
    return toStringz(f.readln());
}

extern(C) bool file_eof(File* f) {
    return f.eof();
}

void main() {}

readfile.rb

require 'ffi'

module ReadFileLib
    extend FFI::Library
    ffi_lib './readfile.so'

    attach_function :lib_init, [], :void
    attach_function :file_open, [:string], :pointer
    attach_function :file_close, [:pointer], :void
    attach_function :file_eof, [:pointer], :bool
    attach_function :file_readln, [:pointer], :string

end

ReadFileLib.lib_init

ptr = ReadFileLib.file_open 'readfile.d'
while not ReadFileLib.file_eof(ptr) do
    puts ReadFileLib.file_readln(ptr)
end
ReadFileLib.file_close ptr