hyparquet/types/alp.d.ts

Parquet file parser for JavaScript

/**
 * ALP (Adaptive Lossless floating-Point) encoding decoder.
 * Supports FLOAT and DOUBLE types.
 *
 * ALP encodes floating-point values by converting them to integers using
 * decimal scaling, then applying frame of reference (FOR) encoding and
 * bit-packing. Values that cannot be losslessly converted are stored as exceptions.
 *
 * See https://github.com/apache/parquet-format/blob/master/AlpEncoding.md
 */
import type { DataReader, DecodedArray, ParquetType } from '../src/types.d.ts';
/**
 * Decode ALP encoded data.
 *
 * @import {DataReader, DecodedArray, ParquetType} from '../src/types.d.ts'
 * @param {DataReader} reader - data reader positioned at start of ALP data
 * @param {number} count - number of values to decode
 * @param {ParquetType} type - FLOAT or DOUBLE
 * @returns {DecodedArray} decoded float or double array
 */
export declare function alpDecode(reader: DataReader, count: number, type: ParquetType): DecodedArray;
/**
 * Decode ALP encoded float data.
 *
 * @param {DataReader} reader
 * @param {number} count
 * @returns {Float32Array}
 */
export declare function alpDecodeFloat(reader: DataReader, count: number): Float32Array;
/**
 * Decode ALP encoded double data.
 *
 * @param {DataReader} reader
 * @param {number} count
 * @returns {Float64Array}
 */
export declare function alpDecodeDouble(reader: DataReader, count: number): Float64Array;
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