threejs/examples/js/loaders/PRWMLoader.js

( function () {

	/**
 * See https://github.com/kchapelier/PRWM for more informations about this file format
 */

	let bigEndianPlatform = null;

	/**
	 * Check if the endianness of the platform is big-endian (most significant bit first)
	 * @returns {boolean} True if big-endian, false if little-endian
	 */
	function isBigEndianPlatform() {

		if ( bigEndianPlatform === null ) {

			const buffer = new ArrayBuffer( 2 ),
				uint8Array = new Uint8Array( buffer ),
				uint16Array = new Uint16Array( buffer );
			uint8Array[ 0 ] = 0xAA; // set first byte
			uint8Array[ 1 ] = 0xBB; // set second byte
			bigEndianPlatform = uint16Array[ 0 ] === 0xAABB;

		}

		return bigEndianPlatform;

	}

	// match the values defined in the spec to the TypedArray types
	const InvertedEncodingTypes = [ null, Float32Array, null, Int8Array, Int16Array, null, Int32Array, Uint8Array, Uint16Array, null, Uint32Array ];

	// define the method to use on a DataView, corresponding the TypedArray type
	const getMethods = {
		Uint16Array: 'getUint16',
		Uint32Array: 'getUint32',
		Int16Array: 'getInt16',
		Int32Array: 'getInt32',
		Float32Array: 'getFloat32',
		Float64Array: 'getFloat64'
	};
	function copyFromBuffer( sourceArrayBuffer, viewType, position, length, fromBigEndian ) {

		const bytesPerElement = viewType.BYTES_PER_ELEMENT;
		let result;
		if ( fromBigEndian === isBigEndianPlatform() || bytesPerElement === 1 ) {

			result = new viewType( sourceArrayBuffer, position, length );

		} else {

			const readView = new DataView( sourceArrayBuffer, position, length * bytesPerElement ),
				getMethod = getMethods[ viewType.name ],
				littleEndian = ! fromBigEndian;
			result = new viewType( length );
			for ( let i = 0; i < length; i ++ ) {

				result[ i ] = readView[ getMethod ]( i * bytesPerElement, littleEndian );

			}

		}

		return result;

	}

	function decodePrwm( buffer ) {

		const array = new Uint8Array( buffer ),
			version = array[ 0 ];
		let flags = array[ 1 ];
		const indexedGeometry = !! ( flags >> 7 & 0x01 ),
			indicesType = flags >> 6 & 0x01,
			bigEndian = ( flags >> 5 & 0x01 ) === 1,
			attributesNumber = flags & 0x1F;
		let valuesNumber = 0,
			indicesNumber = 0;
		if ( bigEndian ) {

			valuesNumber = ( array[ 2 ] << 16 ) + ( array[ 3 ] << 8 ) + array[ 4 ];
			indicesNumber = ( array[ 5 ] << 16 ) + ( array[ 6 ] << 8 ) + array[ 7 ];

		} else {

			valuesNumber = array[ 2 ] + ( array[ 3 ] << 8 ) + ( array[ 4 ] << 16 );
			indicesNumber = array[ 5 ] + ( array[ 6 ] << 8 ) + ( array[ 7 ] << 16 );

		}

		/** PRELIMINARY CHECKS **/

		if ( version === 0 ) {

			throw new Error( 'PRWM decoder: Invalid format version: 0' );

		} else if ( version !== 1 ) {

			throw new Error( 'PRWM decoder: Unsupported format version: ' + version );

		}

		if ( ! indexedGeometry ) {

			if ( indicesType !== 0 ) {

				throw new Error( 'PRWM decoder: Indices type must be set to 0 for non-indexed geometries' );

			} else if ( indicesNumber !== 0 ) {

				throw new Error( 'PRWM decoder: Number of indices must be set to 0 for non-indexed geometries' );

			}

		}

		/** PARSING **/

		let pos = 8;
		const attributes = {};
		for ( let i = 0; i < attributesNumber; i ++ ) {

			let attributeName = '';
			while ( pos < array.length ) {

				const char = array[ pos ];
				pos ++;
				if ( char === 0 ) {

					break;

				} else {

					attributeName += String.fromCharCode( char );

				}

			}

			flags = array[ pos ];
			const attributeType = flags >> 7 & 0x01;
			const cardinality = ( flags >> 4 & 0x03 ) + 1;
			const encodingType = flags & 0x0F;
			const arrayType = InvertedEncodingTypes[ encodingType ];
			pos ++;

			// padding to next multiple of 4
			pos = Math.ceil( pos / 4 ) * 4;
			const values = copyFromBuffer( buffer, arrayType, pos, cardinality * valuesNumber, bigEndian );
			pos += arrayType.BYTES_PER_ELEMENT * cardinality * valuesNumber;
			attributes[ attributeName ] = {
				type: attributeType,
				cardinality: cardinality,
				values: values
			};

		}

		pos = Math.ceil( pos / 4 ) * 4;
		let indices = null;
		if ( indexedGeometry ) {

			indices = copyFromBuffer( buffer, indicesType === 1 ? Uint32Array : Uint16Array, pos, indicesNumber, bigEndian );

		}

		return {
			version: version,
			attributes: attributes,
			indices: indices
		};

	}

	// Define the public interface

	class PRWMLoader extends THREE.Loader {

		constructor( manager ) {

			super( manager );

		}
		load( url, onLoad, onProgress, onError ) {

			const scope = this;
			const loader = new THREE.FileLoader( scope.manager );
			loader.setPath( scope.path );
			loader.setResponseType( 'arraybuffer' );
			loader.setRequestHeader( scope.requestHeader );
			loader.setWithCredentials( scope.withCredentials );
			url = url.replace( /\*/g, isBigEndianPlatform() ? 'be' : 'le' );
			loader.load( url, function ( arrayBuffer ) {

				try {

					onLoad( scope.parse( arrayBuffer ) );

				} catch ( e ) {

					if ( onError ) {

						onError( e );

					} else {

						console.error( e );

					}

					scope.manager.itemError( url );

				}

			}, onProgress, onError );

		}
		parse( arrayBuffer ) {

			const data = decodePrwm( arrayBuffer ),
				attributesKey = Object.keys( data.attributes ),
				bufferGeometry = new THREE.BufferGeometry();
			for ( let i = 0; i < attributesKey.length; i ++ ) {

				const attribute = data.attributes[ attributesKey[ i ] ];
				bufferGeometry.setAttribute( attributesKey[ i ], new THREE.BufferAttribute( attribute.values, attribute.cardinality, attribute.normalized ) );

			}

			if ( data.indices !== null ) {

				bufferGeometry.setIndex( new THREE.BufferAttribute( data.indices, 1 ) );

			}

			return bufferGeometry;

		}
		static isBigEndianPlatform() {

			return isBigEndianPlatform();

		}

	}

	THREE.PRWMLoader = PRWMLoader;

} )();