static RAPIDJSON_FORCEINLINE void ScanCopyUnescapedString()

in src/main/cpp/sdk/common/rapidjson/reader.h [1280:1344]
55 lines of code
11 McCabe index (conditional complexity)

    static RAPIDJSON_FORCEINLINE void ScanCopyUnescapedString(InsituStringStream& is, InsituStringStream& os) {
        RAPIDJSON_ASSERT(&is == &os);
        (void)os;

        if (is.src_ == is.dst_) {
            SkipUnescapedString(is);
            return;
        }

        char* p = is.src_;
        char *q = is.dst_;

        // Scan one by one until alignment (unaligned load may cross page boundary and cause crash)
        const char* nextAligned = reinterpret_cast<const char*>((reinterpret_cast<size_t>(p) + 15) & static_cast<size_t>(~15));
        while (p != nextAligned)
            if (RAPIDJSON_UNLIKELY(*p == '\"') || RAPIDJSON_UNLIKELY(*p == '\\') || RAPIDJSON_UNLIKELY(static_cast<unsigned>(*p) < 0x20)) {
                is.src_ = p;
                is.dst_ = q;
                return;
            }
            else
                *q++ = *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 += 16, q += 16) {
            const uint8x16_t s = vld1q_u8(reinterpret_cast<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 length = 0;
            bool escaped = false;
            if (low == 0) {
                if (high != 0) {
                    unsigned lz = (unsigned)__builtin_clzll(high);
                    length = 8 + (lz >> 3);
                    escaped = true;
                }
            } else {
                unsigned lz = (unsigned)__builtin_clzll(low);
                length = lz >> 3;
                escaped = true;
            }
            if (RAPIDJSON_UNLIKELY(escaped)) {   // some of characters is escaped
                for (const char* pend = p + length; p != pend; ) {
                    *q++ = *p++;
                }
                break;
            }
            vst1q_u8(reinterpret_cast<uint8_t *>(q), s);
        }

        is.src_ = p;
        is.dst_ = q;
    }