bool ParseRange()

in rapidjson/internal/regex.h [500:568]
62 lines of code
16 McCabe index (conditional complexity)

    bool ParseRange(DecodedStream<InputStream>& ds, SizeType* range) {
        bool isBegin = true;
        bool negate = false;
        int step = 0;
        SizeType start = kRegexInvalidRange;
        SizeType current = kRegexInvalidRange;
        unsigned codepoint;
        while ((codepoint = ds.Take()) != 0) {
            if (isBegin) {
                isBegin = false;
                if (codepoint == '^') {
                    negate = true;
                    continue;
                }
            }

            switch (codepoint) {
            case ']':
                if (start == kRegexInvalidRange)
                    return false;   // Error: nothing inside []
                if (step == 2) { // Add trailing '-'
                    SizeType r = NewRange('-');
                    RAPIDJSON_ASSERT(current != kRegexInvalidRange);
                    GetRange(current).next = r;
                }
                if (negate)
                    GetRange(start).start |= kRangeNegationFlag;
                *range = start;
                return true;

            case '\\':
                if (ds.Peek() == 'b') {
                    ds.Take();
                    codepoint = 0x0008; // Escape backspace character
                }
                else if (!CharacterEscape(ds, &codepoint))
                    return false;
                // fall through to default

            default:
                switch (step) {
                case 1:
                    if (codepoint == '-') {
                        step++;
                        break;
                    }
                    // fall through to step 0 for other characters

                case 0:
                    {
                        SizeType r = NewRange(codepoint);
                        if (current != kRegexInvalidRange)
                            GetRange(current).next = r;
                        if (start == kRegexInvalidRange)
                            start = r;
                        current = r;
                    }
                    step = 1;
                    break;

                default:
                    RAPIDJSON_ASSERT(step == 2);
                    GetRange(current).end = codepoint;
                    step = 0;
                }
            }
        }
        return false;
    }