varquantizeas.js

// Data type configuration constants
const DATA_TYPES = {
    int8: { size: 1, min: -128, max: 127, method: 'getInt8' },
    uint8: { size: 1, min: 0, max: 255, method: 'getUint8' },
    int16: { size: 2, min: -32768, max: 32767, method: 'getInt16' },
    uint16: { size: 2, min: 0, max: 65535, method: 'getUint16' },
    int32: { size: 4, min: -2147483648, max: 2147483647, method: 'getInt32' },
    uint32: { size: 4, min: 0, max: 4294967295, method: 'getUint32' }
};

// Pre-calculate normalization multipliers for each data type
const NORMALIZERS = Object.fromEntries(
    Object.entries(DATA_TYPES).map(([type, config]) => [
        type,
        {
            multiplier: 2 / (config.max - config.min),
            offset: config.min
        }
    ])
);

/**
 * Process binary data into normalized 3D points with colors using configurable quantization
 * @param {ArrayBuffer} buffer - The input binary data
 * @param {string} dataType - The data type to interpret the buffer as
 * @param {boolean} isLittleEndian - Whether to read as little endian
 * @param {number} quantizationBits - Number of bits for quantization (2-10)
 * @returns {{ points: Float32Array, colors: Float32Array, numPoints: number }}
 */
function quantizeProcessDataAs(buffer, dataType, isLittleEndian, quantizationBits = 10) {
    // Input validation
    if (!buffer || !(buffer instanceof ArrayBuffer)) {
        throw new Error('Invalid buffer provided - must be an ArrayBuffer');
    }
    
    const config = DATA_TYPES[dataType];
    if (!config) {
        throw new Error(`Unsupported data type: ${dataType}. Supported types: ${Object.keys(DATA_TYPES).join(', ')}`);
    }

    // Validate quantization bits
    if (!Number.isInteger(quantizationBits) || quantizationBits < 2 || quantizationBits > 10) {
        throw new Error('quantizationBits must be an integer between 2 and 10');
    }

    // Check if total bits would exceed safe integer limits
    const totalBits = quantizationBits * 3;
    if (totalBits > 30) {
        throw new Error(`Total quantization bits (${totalBits}) would exceed safe integer limits. Max 30 bits (10 bits per dimension)`);
    }
    
    const typeSize = config.size;
    const tupleSize = typeSize * 3;
    
    if (buffer.byteLength < tupleSize) {
        throw new Error(`Buffer too small for data type ${dataType}. Need at least ${tupleSize} bytes, got ${buffer.byteLength}`);
    }

    const view = new DataView(buffer);
    const maxOffset = buffer.byteLength - tupleSize;
    const maxTuples = Math.floor(buffer.byteLength / tupleSize);
    
    // Pre-allocate typed arrays for better performance
    const points = new Float32Array(maxTuples * 3);
    const colors = new Float32Array(maxTuples * 3);
    
    // Cache normalization values and methods
    const { multiplier, offset } = NORMALIZERS[dataType];
    const readMethod = view[config.method].bind(view);
    const normalize = value => ((value - offset) * multiplier) - 1;
    
    let pointIndex = 0;
    let baseOffset = 0;

    // Calculate quantization parameters based on bit count
    const qRange = 1 << quantizationBits; // 2^quantizationBits
    const qHalfRange = qRange / 2;
    const qMaxIndex = qRange - 1;

    // Bit array sized for qRange^3 possible quantized positions
    const totalQuantizedPositions = qRange * qRange * qRange;
    const bitArraySizeInUint32 = Math.ceil(totalQuantizedPositions / 32);
    const tupleBitArray = new Uint32Array(bitArraySizeInUint32); 
    
    // Calculate bit shift amounts for index creation
    const yShift = quantizationBits;
    const zShift = quantizationBits * 2;
    
    try {
        while (baseOffset <= maxOffset) {
            // Read and normalize all three coordinates
            const x = normalize(readMethod(baseOffset, isLittleEndian));
            const y = normalize(readMethod(baseOffset + typeSize, isLittleEndian));
            const z = normalize(readMethod(baseOffset + typeSize * 2, isLittleEndian));

            // Quantize coordinates: map [-1,1] to [0, qMaxIndex] with bounds checking
            const qx = Math.max(0, Math.min(qMaxIndex, Math.floor((x + 1) * qHalfRange)));
            const qy = Math.max(0, Math.min(qMaxIndex, Math.floor((y + 1) * qHalfRange)));
            const qz = Math.max(0, Math.min(qMaxIndex, Math.floor((z + 1) * qHalfRange)));

            // Create unique index for this quantized position using variable bit shifts
            const qIndex = (qz << zShift) | (qy << yShift) | qx;

            // Check if we've seen this quantized position before
            const elementIndex = qIndex >>> 5; // Use unsigned right shift for bit array indexing
            const bitPosition = qIndex & 0x1F;
            const mask = 1 << bitPosition;

            if ((tupleBitArray[elementIndex] & mask) === 0) {
                // Mark this position as seen
                tupleBitArray[elementIndex] |= mask;

                // Store points (original normalized coordinates, not quantized)
                points[pointIndex] = x;
                points[pointIndex + 1] = y;
                points[pointIndex + 2] = z;
                
                // Store colors (mapped from [-1,1] to [0,1] for Three.js)
                colors[pointIndex] = (x + 1) / 2;
                colors[pointIndex + 1] = (y + 1) / 2;
                colors[pointIndex + 2] = (z + 1) / 2;

                pointIndex += 3;
            }

            baseOffset += tupleSize;
        }
    } catch (e) {
        console.error(`Error processing data at offset: ${baseOffset}`, e);
        // Return what we've processed so far rather than failing completely
    }

    // Trim arrays to actual size used
    const actualPoints = new Float32Array(points.buffer, 0, pointIndex);
    const actualColors = new Float32Array(colors.buffer, 0, pointIndex);

    console.log(`Quantization completed: ${quantizationBits} bits, ${qRange}^3 possible positions, ${pointIndex / 3} unique points found`);

    return {
        points: actualPoints,
        colors: actualColors,
        numPoints: pointIndex / 3,
        quantizationBits: quantizationBits,
        quantizationRange: qRange
    };
}

export { quantizeProcessDataAs, DATA_TYPES };