Native C implementation for String#^

README.markdown

put both files into a directory run ruby extconfig.rb, then make in the directory. You should get a .so or .bundle as a result.

extconfig.rb

require 'mkmf'

create_makefile 'string_xor'

string_xor.c

#include <ruby.h>
#include <ruby/encoding.h>

VALUE
rb_string_xor(VALUE str1, VALUE str2)
{
    StringValue(str2);
    if (RSTRING_LEN(str1) != RSTRING_LEN(str2)) rb_raise(rb_eArgError, "Both strings must have the same length");

    VALUE str3 = rb_enc_str_new(0, RSTRING_LEN(str1), rb_ascii8bit_encoding());
    char *c1   = RSTRING_PTR(str1);
    char *c2   = RSTRING_PTR(str2);
    char *c3   = RSTRING_PTR(str3);
    long len   = RSTRING_LEN(str1);

    for(long i=0; i<len; i++) {
        c3[i] = c1[i] ^ c2[i];
    }
    RSTRING_PTR(str3)[RSTRING_LEN(str3)] = '\0';

    return str3;
}

void
Init_string_xor()
{
    rb_cString = rb_define_class("String", rb_cObject);

    rb_define_method(rb_cString, "^", rb_string_xor, 1);
}