@opentelemetry/sdk-metrics
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JavaScript
;
Object.defineProperty(exports, "__esModule", { value: true });
exports.ExponentMapping = void 0;
/*
* Copyright The OpenTelemetry Authors
* SPDX-License-Identifier: Apache-2.0
*/
const ieee754 = require("./ieee754");
const util = require("../util");
const types_1 = require("./types");
/**
* ExponentMapping implements exponential mapping functions for
* scales <=0. For scales > 0 LogarithmMapping should be used.
*/
class ExponentMapping {
_shift;
constructor(scale) {
this._shift = -scale;
}
/**
* Maps positive floating point values to indexes corresponding to scale
* @param value
* @returns {number} index for provided value at the current scale
*/
mapToIndex(value) {
if (value < ieee754.MIN_VALUE) {
return this._minNormalLowerBoundaryIndex();
}
const exp = ieee754.getNormalBase2(value);
// In case the value is an exact power of two, compute a
// correction of -1. Note, we are using a custom _rightShift
// to accommodate a 52-bit argument, which the native bitwise
// operators do not support
const correction = this._rightShift(ieee754.getSignificand(value) - 1, ieee754.SIGNIFICAND_WIDTH);
return (exp + correction) >> this._shift;
}
/**
* Returns the lower bucket boundary for the given index for scale
*
* @param index
* @returns {number}
*/
lowerBoundary(index) {
const minIndex = this._minNormalLowerBoundaryIndex();
if (index < minIndex) {
throw new types_1.MappingError(`underflow: ${index} is < minimum lower boundary: ${minIndex}`);
}
const maxIndex = this._maxNormalLowerBoundaryIndex();
if (index > maxIndex) {
throw new types_1.MappingError(`overflow: ${index} is > maximum lower boundary: ${maxIndex}`);
}
return util.ldexp(1, index << this._shift);
}
/**
* The scale used by this mapping
* @returns {number}
*/
get scale() {
if (this._shift === 0) {
return 0;
}
return -this._shift;
}
_minNormalLowerBoundaryIndex() {
let index = ieee754.MIN_NORMAL_EXPONENT >> this._shift;
if (this._shift < 2) {
index--;
}
return index;
}
_maxNormalLowerBoundaryIndex() {
return ieee754.MAX_NORMAL_EXPONENT >> this._shift;
}
_rightShift(value, shift) {
return Math.floor(value * Math.pow(2, -shift));
}
}
exports.ExponentMapping = ExponentMapping;
//# sourceMappingURL=ExponentMapping.js.map