swapcase!(*args)
public
Equivalent to String#swapcase, but modifies the receiver in place,
returning str, or nil if no changes were made.
See String#downcase for meaning of
options and use with different encodings.
static VALUE
rb_str_swapcase_bang(int argc, VALUE *argv, VALUE str)
{
rb_encoding *enc;
OnigCaseFoldType flags = ONIGENC_CASE_UPCASE | ONIGENC_CASE_DOWNCASE;
flags = check_case_options(argc, argv, flags);
str_modify_keep_cr(str);
enc = STR_ENC_GET(str);
rb_str_check_dummy_enc(enc);
if (flags&ONIGENC_CASE_ASCII_ONLY)
rb_str_ascii_casemap(str, &flags, enc);
else
str_shared_replace(str, rb_str_casemap(str, &flags, enc));
if (ONIGENC_CASE_MODIFIED&flags) return str;
return Qnil;
}