mirror of
https://github.com/balena-io/etcher.git
synced 2025-04-24 23:37:18 +00:00
7c9f15d8a9
Changes: - Split out scanner into own file - Move `lib/shared/sdk` -> `lib/sdk` - Move `lib/image-stream` -> `lib/sdk/image-stream` - Move `lib/writer` -> `lib/sdk/writer` - Rename `sdk/standard` -> `sdk/blockdevice` - Move adapters into `sdk/adapters` subdirectory Change-Type: minor Changelog-Entry: Consolidate low-level components into Etcher SDK
73 lines
2.1 KiB
JavaScript
73 lines
2.1 KiB
JavaScript
/*
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* Copyright 2016 resin.io
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict'
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/**
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* @summary The byte length of ISIZE
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* @type {Number}
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* @constant
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* @description
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* See https://tools.ietf.org/html/rfc1952
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*/
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const ISIZE_LENGTH = 4
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/**
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* @summary Get the estimated uncompressed size of a gzip file
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* @function
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* @public
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*
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* @description
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* This function determines the uncompressed size of the gzip file
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* by reading its `ISIZE` field at the end of the file. The specification
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* clarifies that this value is just an estimation.
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*
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* @param {Object} options - options
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* @param {Number} options.size - file size
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* @param {Function} options.read - read function (position, count)
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* @fulfil {Number} - uncompressed size
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* @returns {Promise}
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*
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* @example
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* const fd = fs.openSync('path/to/image', 'r');
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*
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* gzip.getUncompressedSize({
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* size: fs.statSync('path/to/image.gz').size,
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* read: (position, count) => {
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* const buffer = Buffer.alloc(count);
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* return new Promise((resolve, reject) => {
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* fs.read(fd, buffer, 0, count, position, (error) => {
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* if (error) {
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* return reject(error);
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* }
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*
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* resolve(buffer);
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* });
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* });
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* }
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* }).then((uncompressedSize) => {
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* console.log(`The uncompressed size is: ${uncompressedSize}`);
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* fs.closeSync(fd);
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* });
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*/
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exports.getUncompressedSize = (options) => {
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const ISIZE_BUFFER_START = 0
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const ISIZE_POSITION = options.size - ISIZE_LENGTH
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return options.read(ISIZE_POSITION, ISIZE_LENGTH).then((buffer) => {
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return buffer.readUInt32LE(ISIZE_BUFFER_START)
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})
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}
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