obj2gltf/lib/ArrayStorage.js

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"use strict";
const Cesium = require("cesium");
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const ComponentDatatype = Cesium.ComponentDatatype;
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module.exports = ArrayStorage;
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const initialLength = 1024; // 2^10
const doublingThreshold = 33554432; // 2^25 (~134 MB for a Float32Array)
const fixedExpansionLength = 33554432; // 2^25 (~134 MB for a Float32Array)
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/**
* Provides expandable typed array storage for geometry data. This is preferable to JS arrays which are
* stored with double precision. The resizing mechanism is similar to std::vector.
*
* @param {ComponentDatatype} componentDatatype The data type.
*
* @private
*/
function ArrayStorage(componentDatatype) {
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this.componentDatatype = componentDatatype;
this.typedArray = ComponentDatatype.createTypedArray(componentDatatype, 0);
this.length = 0;
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}
function resize(storage, length) {
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const typedArray = ComponentDatatype.createTypedArray(
storage.componentDatatype,
length
);
typedArray.set(storage.typedArray);
storage.typedArray = typedArray;
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}
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ArrayStorage.prototype.push = function (value) {
const length = this.length;
const typedArrayLength = this.typedArray.length;
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if (length === 0) {
resize(this, initialLength);
} else if (length === typedArrayLength) {
if (length < doublingThreshold) {
resize(this, typedArrayLength * 2);
} else {
resize(this, typedArrayLength + fixedExpansionLength);
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}
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}
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this.typedArray[this.length++] = value;
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};
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ArrayStorage.prototype.get = function (index) {
return this.typedArray[index];
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};
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const sizeOfUint16 = 2;
const sizeOfUint32 = 4;
const sizeOfFloat = 4;
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ArrayStorage.prototype.toUint16Buffer = function () {
const length = this.length;
const typedArray = this.typedArray;
const paddedLength = length + (length % 2 === 0 ? 0 : 1); // Round to next multiple of 2
const buffer = Buffer.alloc(paddedLength * sizeOfUint16);
for (let i = 0; i < length; ++i) {
buffer.writeUInt16LE(typedArray[i], i * sizeOfUint16);
}
return buffer;
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};
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ArrayStorage.prototype.toUint32Buffer = function () {
const length = this.length;
const typedArray = this.typedArray;
const buffer = Buffer.alloc(length * sizeOfUint32);
for (let i = 0; i < length; ++i) {
buffer.writeUInt32LE(typedArray[i], i * sizeOfUint32);
}
return buffer;
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};
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ArrayStorage.prototype.toFloatBuffer = function () {
const length = this.length;
const typedArray = this.typedArray;
const buffer = Buffer.alloc(length * sizeOfFloat);
for (let i = 0; i < length; ++i) {
buffer.writeFloatLE(typedArray[i], i * sizeOfFloat);
}
return buffer;
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};
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ArrayStorage.prototype.getMinMax = function (components) {
const length = this.length;
const typedArray = this.typedArray;
const count = length / components;
const min = new Array(components).fill(Number.POSITIVE_INFINITY);
const max = new Array(components).fill(Number.NEGATIVE_INFINITY);
for (let i = 0; i < count; ++i) {
for (let j = 0; j < components; ++j) {
const index = i * components + j;
const value = typedArray[index];
min[j] = Math.min(min[j], value);
max[j] = Math.max(max[j], value);
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}
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}
return {
min: min,
max: max,
};
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};