/* * Copyright 2017 resin.io * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ 'use strict' const _ = require('lodash') const Bluebird = require('bluebird') const fs = Bluebird.promisifyAll(require('fs')) const fileType = require('file-type') const mime = require('mime-types') const utils = require('./utils') /** * @summary The default MIME type * @type {String} * @constant */ exports.DEFAULT_MIME_TYPE = 'application/octet-stream' /** * @summary Get file's mime type, by reading the initial 262 bytes if necessary * @function * @public * * @param {String} filename - file path * @fulfil {String} - mime type * @returns {Promise} * * @example * mime.getMimeTypeFromFileName('path/to/raspberrypi.img.gz').then((mimeType) => { * console.log(mimeType); * }); */ exports.getMimeTypeFromFileName = (filename) => { const mimeType = mime.lookup(filename) if (mimeType) { return Bluebird.resolve(mimeType) } const FILE_TYPE_ID_START = 0 const FILE_TYPE_ID_BYTES = 262 return Bluebird.using(fs.openAsync(filename, 'r').disposer((fileDescriptor) => { return fs.closeAsync(fileDescriptor) }), (fileDescriptor) => { return utils.readBufferFromImageFileDescriptor(fileDescriptor, FILE_TYPE_ID_START, FILE_TYPE_ID_BYTES).then((buffer) => { return _.get(fileType(buffer), [ 'mime' ], exports.DEFAULT_MIME_TYPE) }) }) }