120 lines
3 KiB
JavaScript
120 lines
3 KiB
JavaScript
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// Reimplementation of https://source.dot.net/#System.Private.CoreLib/Random.cs,bb77e610694e64ca
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const MamiRNG = function(seed) {
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const MBIG = 0x7FFFFFFF;
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const MSEED = 161803398;
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if((typeof seed).toLowerCase() !== 'number')
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seed = Math.round(Date.now() / 1000);
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const seedArray = new Int32Array(56);
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const vars = new Int32Array(2);
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const mjVal = 0, mkVal = 1;
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let ii = 0;
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vars[mjVal] = seed;
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vars[mjVal] = (vars[mjVal] === -0x80000000) ? 0x7FFFFFFF : Math.abs(vars[mjVal]);
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vars[mjVal] = MSEED - vars[mjVal];
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seedArray[55] = vars[mjVal];
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vars[mkVal] = 1;
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for(let i = 1; i < 55; i++) {
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if((ii += 21) >= 55)
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ii -= 55;
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seedArray[ii] = vars[mkVal];
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vars[mkVal] = vars[mjVal] - vars[mkVal];
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if(vars[mkVal] < 0)
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vars[mkVal] += MBIG;
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vars[mjVal] = seedArray[ii];
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}
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for(let k = 1; k < 5; k++) {
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for(let i = 0; i < 56; i++) {
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let n = i + 30;
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if(n >= 55)
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n -= 55;
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seedArray[i] -= seedArray[1 + n];
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if(seedArray[i] < 0)
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seedArray[i] += MBIG;
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}
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}
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let inext = 0,
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inextp = 21;
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const internalSample = function() {
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const retVal = new Int32Array(1);
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let locINext = inext,
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locINextp = inextp;
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if(++locINext >= 56)
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locINext = 1;
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if(++locINextp >= 56)
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locINextp = 1;
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retVal[0] = seedArray[locINext];
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retVal[0] -= seedArray[locINextp];
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if(retVal[0] == MBIG)
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retVal[0]--;
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if(retVal[0] < 0)
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retVal[0] += MBIG;
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seedArray[locINext] = retVal[0];
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inext = locINext;
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inextp = locINextp;
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return retVal[0];
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};
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const sample = function() {
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return internalSample() * (1.0 / MBIG);
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};
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return {
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sample: sample,
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next: function(minValue, maxValue) {
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let hasMinVal = (typeof minValue).toLowerCase() === 'number',
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hasMaxVal = (typeof maxValue).toLowerCase() === 'number';
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const vars = new Int32Array(3),
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minVal = 0, maxVal = 1, retVal = 2;
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if(hasMinVal) {
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if(!hasMaxVal) {
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hasMinVal = false;
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hasMaxVal = true;
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vars[maxVal] = minValue;
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} else {
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vars[minVal] = minValue;
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vars[maxVal] = maxValue;
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}
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}
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if(hasMaxVal) {
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if(hasMinVal) {
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if(vars[minVal] > vars[maxVal])
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throw 'Argument out of range.';
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const range = vars[maxVal] - vars[minVal];
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vars[retVal] = sample() * range;
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vars[retVal] += vars[minVal];
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return vars[retVal];
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}
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vars[retVal] = sample() * vars[maxVal];
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return vars[retVal];
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}
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return internalSample();
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},
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};
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};
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