@versatiles/container/dist/lib/decompress.js

A client library for reading VersaTiles containers

import zlib from 'zlib';
/**
 * Decompresses a buffer using the specified compression algorithm. Currently supports 'br' for Brotli and 'gzip' for GZIP.
 * If the specified algorithm is not supported, the function resolves the promise with the original buffer.
 *
 * @param {Buffer} buffer - The buffer to be decompressed.
 * @param {Compression} compression - The compression algorithm to use. Supported values are 'br' for Brotli and 'gzip' for GZIP.
 * @returns {Promise<Buffer>} A promise that, when resolved, provides the decompressed buffer. If the compression type is not recognized,
 * the promise will resolve with the original buffer. If decompression fails, the promise will be rejected with an error message.
 * @throws {Error} Throws an error if the decompression process encounters an error. The error includes the buffer's length and
 * the compression algorithm that was attempted.
 */
export async function decompress(buffer, compression) {
    return new Promise((resolve, reject) => {
        switch (compression) {
            case 'br':
                zlib.brotliDecompress(buffer, handle);
                break;
            case 'gzip':
                zlib.gunzip(buffer, handle);
                break;
            default:
                resolve(buffer);
                break;
        }
        /**
         * Handles the result of the decompression operation. If decompression is successful, the promise is resolved
         * with the decompressed buffer. If an error occurs during decompression, the promise is rejected with a descriptive
         * error message.
         *
         * @param {Error | null} error - The error object, if any, returned from the decompression operation.
         * @param {Buffer} result - The decompressed buffer returned from the decompression operation.
         * @throws {Error} Throws an error if decompression fails, including the buffer length and the attempted compression method.
         */
        function handle(error, result) {
            if (error) {
                reject(new Error(`Can not decompress buffer (length=${buffer.length}) with "${compression}": ${error.message}`));
                return;
            }
            else {
                resolve(result);
            }
        }
    });
}