inline bool Writer::ScanWriteUnescapedString()

in src/main/cpp/sdk/common/rapidjson/writer.h [635:700]
56 lines of code
13 McCabe index (conditional complexity)

inline bool Writer<StringBuffer>::ScanWriteUnescapedString(StringStream& is, size_t length) {
    if (length < 16)
        return RAPIDJSON_LIKELY(is.Tell() < length);

    if (!RAPIDJSON_LIKELY(is.Tell() < length))
        return false;

    const char* p = is.src_;
    const char* end = is.head_ + length;
    const char* nextAligned = reinterpret_cast<const char*>((reinterpret_cast<size_t>(p) + 15) & static_cast<size_t>(~15));
    const char* endAligned = reinterpret_cast<const char*>(reinterpret_cast<size_t>(end) & static_cast<size_t>(~15));
    if (nextAligned > end)
        return true;

    while (p != nextAligned)
        if (*p < 0x20 || *p == '\"' || *p == '\\') {
            is.src_ = p;
            return RAPIDJSON_LIKELY(is.Tell() < length);
        }
        else
            os_->PutUnsafe(*p++);

    // The rest of string using SIMD
    const uint8x16_t s0 = vmovq_n_u8('"');
    const uint8x16_t s1 = vmovq_n_u8('\\');
    const uint8x16_t s2 = vmovq_n_u8('\b');
    const uint8x16_t s3 = vmovq_n_u8(32);

    for (; p != endAligned; p += 16) {
        const uint8x16_t s = vld1q_u8(reinterpret_cast<const uint8_t *>(p));
        uint8x16_t x = vceqq_u8(s, s0);
        x = vorrq_u8(x, vceqq_u8(s, s1));
        x = vorrq_u8(x, vceqq_u8(s, s2));
        x = vorrq_u8(x, vcltq_u8(s, s3));

        x = vrev64q_u8(x);                     // Rev in 64
        uint64_t low = vgetq_lane_u64(reinterpret_cast<uint64x2_t>(x), 0);   // extract
        uint64_t high = vgetq_lane_u64(reinterpret_cast<uint64x2_t>(x), 1);  // extract

        SizeType len = 0;
        bool escaped = false;
        if (low == 0) {
            if (high != 0) {
                unsigned lz = (unsigned)__builtin_clzll(high);
                len = 8 + (lz >> 3);
                escaped = true;
            }
        } else {
            unsigned lz = (unsigned)__builtin_clzll(low);
            len = lz >> 3;
            escaped = true;
        }
        if (RAPIDJSON_UNLIKELY(escaped)) {   // some of characters is escaped
            char* q = reinterpret_cast<char*>(os_->PushUnsafe(len));
            for (size_t i = 0; i < len; i++)
                q[i] = p[i];

            p += len;
            break;
        }
        vst1q_u8(reinterpret_cast<uint8_t *>(os_->PushUnsafe(16)), s);
    }

    is.src_ = p;
    return RAPIDJSON_LIKELY(is.Tell() < length);
}