CODEWITHSUNDEEP
c++
user81993
user81993

Reputation: 6613

Initializing a lookup table in c++

Since I cant seem to make the constructor for my conversion class static, I tried faking it but its giving me an error about unresolved externals:

struct FloatConversions {
    static std::array<float, 256> ByteLUT;

    struct Initializer {
        Initializer() {
            for (double i = 0; i < 256; i++) {
                ByteLUT[i] = i / 255.0;
            }
        }
    };
    Initializer Init;

    static inline float ByteToFloat(int val) {
        return ByteLUT[val];
    }
    static inline uint8_t FloatToByte(float val) {
        return static_cast<uint8_t>(val * 255.0f);
    }
};
typedef FloatConversions FC;

what could be the problem?

Upvotes: 2

Views: 1298

Answers (1)

Neil Kirk
Neil Kirk

Reputation: 21773

Here is a simple solution that does the job.

float ByteToFloat(int val)
{
    static const struct FloatConversions
    {
        std::array<float, 256> ByteLUT;

        FloatConversions()
        {
            for (int i = 0; i < 256; i++)
            {
                ByteLUT[i] = i / 255.0f;
            }
        }
    } conveter;

    return conveter.ByteLUT[val];
}

Upvotes: 5

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