Function lookup_code_index

csrc/cpu_ops.cpp:20–36

constexpr int kCodebookSize = 256;

inline unsigned char lookup_code_index(const float* codebook, float value) {
    value = std::clamp(value, -1.0f, 1.0f);
    const float* begin = codebook;
    const float* end = codebook + kCodebookSize;
    const float* right = std::lower_bound(begin, end, value);
    if (right == begin) {
        return 0;
    }
    if (right == end) {
        return static_cast<unsigned char>(kCodebookSize - 1);
    }
    const float* left = right - 1;
    const float dist_left = std::fabs(value - *left);
    const float dist_right = std::fabs(*right - value);
    const unsigned char idx = static_cast<unsigned char>(right - begin);
    return dist_right < dist_left ? idx : idx - 1;
}

} // namespace