Ruby Encoding Compatibility Check

encoding_compatibility.java

@Specialization(guards = {
        "firstEncoding != secondEncoding",
        "!isBroken(first, codeRangeNode)",
        "!isBroken(second, codeRangeNode)"
})
protected RubyEncoding commonCases(
        Rope first, RubyEncoding firstEncoding, Rope second, RubyEncoding secondEncoding) {
    final CodeRange firstCodeRange = getCodeRange(first);
    final CodeRange secondCodeRange = getCodeRange(second);

    assert firstCodeRange == CodeRange.CR_7BIT || firstCodeRange == CodeRange.CR_VALID;
    assert secondCodeRange == CodeRange.CR_7BIT || secondCodeRange == CodeRange.CR_VALID;

    if (firstEncoding == Encodings.UTF_8) {
        if (secondEncoding == Encodings.US_ASCII) {
            return Encodings.UTF_8;
        }

        if (secondEncoding == Encodings.BINARY) {
            if (secondCodeRange == CodeRange.CR_7BIT) {
                return Encodings.UTF_8;
            }

            if (secondCodeRange == CodeRange.CR_VALID) {
                if (firstCodeRange == CodeRange.CR_VALID && !second.isEmpty()) {
                    return null;
                }

                return Encodings.BINARY;
            }
        }
    } else if (firstEncoding == Encodings.US_ASCII) {
        if (secondEncoding == Encodings.UTF_8) {
            if (secondCodeRange == CodeRange.CR_VALID) {
                return secondEncoding;
            } else {
                return Encodings.US_ASCII;
            }
        }

        if (secondEncoding == Encodings.BINARY) {
            if (secondCodeRange == CodeRange.CR_VALID) {
                return Encodings.BINARY;
            } else {
                return Encodings.US_ASCII;
            }
        }
    } else if (firstEncoding == Encodings.BINARY) {
        if (secondEncoding == Encodings.UTF_8) {
            if (secondCodeRange == CodeRange.CR_7BIT || second.isEmpty()) {
                return Encodings.BINARY;
            }

            if (firstCodeRange == CodeRange.CR_VALID && secondCodeRange == CodeRange.CR_VALID &&
                    !first.isEmpty()) {
                return null;
            } else {
                return Encodings.UTF_8;
            }
        }

        if (secondEncoding == Encodings.US_ASCII) {
            return Encodings.BINARY;
        }
    }

    return compatibleEncodingForRopes(first, firstEncoding, second, secondEncoding);
}