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91 lines
2.4 KiB
JavaScript
91 lines
2.4 KiB
JavaScript
// Copyright (c) 2017 Matthew Brennan Jones <matthew.brennan.jones@gmail.com>
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// This software is licensed under a MIT License
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// https://github.com/workhorsy/uncompress.js
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"use strict";
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// Based on the information from:
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// https://en.wikipedia.org/wiki/Tar_(computing)
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(function() {
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const TAR_TYPE_FILE = 0;
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const TAR_TYPE_DIR = 5;
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const TAR_HEADER_SIZE = 512;
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const TAR_TYPE_OFFSET = 156;
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const TAR_TYPE_SIZE = 1;
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const TAR_SIZE_OFFSET = 124;
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const TAR_SIZE_SIZE = 12;
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const TAR_NAME_OFFSET = 0;
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const TAR_NAME_SIZE = 100;
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function _tarRead(view, offset, size) {
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return view.slice(offset, offset + size);
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}
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function tarGetEntries(filename, array_buffer) {
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let view = new Uint8Array(array_buffer);
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let offset = 0;
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let entries = [];
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while (offset + TAR_HEADER_SIZE < view.byteLength) {
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// Get entry name
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let entry_name = saneMap(_tarRead(view, offset + TAR_NAME_OFFSET, TAR_NAME_SIZE), String.fromCharCode);
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entry_name = entry_name.join('').replace(/\0/g, '');
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// No entry name, so probably the last block
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if (entry_name.length === 0) {
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break;
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}
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// Get entry size
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let entry_size = parseInt(saneJoin(saneMap(_tarRead(view, offset + TAR_SIZE_OFFSET, TAR_SIZE_SIZE), String.fromCharCode), ''), 8);
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let entry_type = saneMap(_tarRead(view, offset + TAR_TYPE_OFFSET, TAR_TYPE_SIZE), String.fromCharCode) | 0;
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// Save this as en entry if it is a file or directory
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if (entry_type === TAR_TYPE_FILE || entry_type === TAR_TYPE_DIR) {
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let entry = {
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name: entry_name,
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size: entry_size,
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is_file: entry_type == TAR_TYPE_FILE,
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offset: offset
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};
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entries.push(entry);
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}
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// Round the offset up to be divisible by TAR_HEADER_SIZE
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offset += (entry_size + TAR_HEADER_SIZE);
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if (offset % TAR_HEADER_SIZE > 0) {
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let even = (offset / TAR_HEADER_SIZE) | 0; // number of times it goes evenly into TAR_HEADER_SIZE
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offset = (even + 1) * TAR_HEADER_SIZE;
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}
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}
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return entries;
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}
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function tarGetEntryData(entry, array_buffer) {
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let view = new Uint8Array(array_buffer);
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let offset = entry.offset;
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let size = entry.size;
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// Get entry data
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let entry_data = _tarRead(view, offset + TAR_HEADER_SIZE, size);
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return entry_data;
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}
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// Figure out if we are running in a Window or Web Worker
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let scope = null;
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if (typeof window === 'object') {
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scope = window;
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} else if (typeof importScripts === 'function') {
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scope = self;
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}
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// Set exports
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scope.tarGetEntries = tarGetEntries;
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scope.tarGetEntryData = tarGetEntryData;
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})();
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