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Asher
285
packages/requirefs/src/tarReader.ts
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285
packages/requirefs/src/tarReader.ts
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import * as path from "path";
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const textDecoder = new (typeof TextDecoder === "undefined" ? require("text-encoding").TextDecoder : TextDecoder)();
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/**
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* Tar represents a tar archive.
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*/
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export class Tar {
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/**
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* Return a tar object from a Uint8Array.
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*/
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public static fromUint8Array(array: Uint8Array): Tar {
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const reader = new Reader(array);
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const tar = new Tar();
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while (true) {
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try {
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const file = TarFile.fromReader(reader);
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if (file) {
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tar._files.set(path.normalize(file.name), file);
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}
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} catch (e) {
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if (e.message === "EOF") {
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break;
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}
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throw e;
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}
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}
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reader.unclamp();
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return tar;
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}
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private readonly _files: Map<string, TarFile>;
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private constructor() {
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this._files = new Map();
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}
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public get files(): ReadonlyMap<string, TarFile> {
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return this._files;
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}
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}
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/**
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* Represents a tar files location within a reader
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*/
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export class TarFile {
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/**
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* Locate a tar file from a reader.
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*/
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public static fromReader(reader: Reader): TarFile | undefined {
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const firstByte = reader.peek(1)[0];
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// If the first byte is nil, we know it isn't a filename
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if (firstByte === 0x00) {
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// The tar header is 512 bytes large. Its safe to skip here
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// because we know this block is not a header
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reader.skip(512);
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return undefined;
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}
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let name = reader.readString(100);
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reader.skip(8); // 100->108 mode
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reader.skip(8); // 108->116 uid
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reader.skip(8); // 116->124 gid
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const rawSize = reader.read(12); // 124->136 size
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reader.skip(12); // 136->148 mtime
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if (reader.jump(345).readByte()) {
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name = reader.jump(345).readString(155) + "/" + name;
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}
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const nums: number[] = [];
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rawSize.forEach((a) => nums.push(a));
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const parseSize = (): number => {
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let offset = 0;
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// While 48 (ASCII value of 0), the byte is nil and considered padding.
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while (offset < rawSize.length && nums[offset] === 48) {
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offset++;
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}
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const clamp = (index: number, len: number, defaultValue: number): number => {
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if (typeof index !== "number") {
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return defaultValue;
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}
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// Coerce index to an integer.
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index = ~~index;
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if (index >= len) {
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return len;
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}
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if (index >= 0) {
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return index;
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}
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index += len;
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if (index >= 0) {
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return index;
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}
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return 0;
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};
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// Checks for the index of the POSIX file-size terminating char.
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// Falls back to GNU's tar format. If neither characters are found
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// the index will default to the end of the file size buffer.
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let i = nums.indexOf(32, offset);
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if (i === -1) {
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i = nums.indexOf(0, offset);
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if (i === -1) {
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i = rawSize.length - 1;
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}
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}
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const end = clamp(i, rawSize.length, rawSize.length - 1);
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if (end === offset) {
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return 0;
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}
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return parseInt(textDecoder.decode(rawSize.slice(offset, end)), 8);
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};
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const size = parseSize();
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const overflow = ((): number => {
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let newSize = size;
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newSize &= 511;
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return newSize && 512 - newSize;
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})();
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reader.jump(512);
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const offset = reader.offset;
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reader.skip(overflow + size);
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reader.clamp();
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const tarFile = new TarFile(reader, {
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offset,
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name,
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size,
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});
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return tarFile;
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}
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public constructor(
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private readonly reader: Reader,
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private readonly data: {
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name: string;
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size: number;
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offset: number;
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},
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) { }
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public get name(): string {
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return this.data.name;
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}
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public get size(): number {
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return this.data.size;
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}
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/**
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* Check if the file type is a file.
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*/
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public isFile(): boolean {
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throw new Error("not implemented");
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}
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/**
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* Read the file as a string.
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*/
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public readAsString(): string {
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return textDecoder.decode(this.read());
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}
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/**
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* Read the file as Uint8Array.
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*/
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public read(): Uint8Array {
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return this.reader.jump(this.data.offset).read(this.data.size);
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}
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}
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/**
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* Reads within a Uint8Array.
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*/
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export class Reader {
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private array: Uint8Array;
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private _offset: number;
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private lastClamp: number;
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public constructor(array: Uint8Array) {
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this.array = array;
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this._offset = 0;
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this.lastClamp = 0;
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}
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public get offset(): number {
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return this._offset;
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}
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/**
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* Skip the specified amount of bytes.
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*/
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public skip(amount: number): boolean {
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if (this._offset + amount > this.array.length) {
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throw new Error("EOF");
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}
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this._offset += amount;
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return true;
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}
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/**
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* Clamp the reader at a position.
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*/
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public clamp(): void {
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this.lastClamp = this._offset;
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}
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/**
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* Unclamp the reader.
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*/
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public unclamp(): void {
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this.lastClamp = 0;
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}
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/**
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* Jump to a specific offset.
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*/
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public jump(offset: number): Reader {
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this._offset = offset + this.lastClamp;
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return this;
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}
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/**
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* Peek the amount of bytes.
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*/
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public peek(amount: number): Uint8Array {
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return this.array.slice(this.offset, this.offset + amount);
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}
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/**
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* Read a string.
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*/
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public readString(amount: number): string {
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// Replacing the 0s removes all nil bytes from the str
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return textDecoder.decode(this.read(amount)).replace(/\0/g, "");
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}
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/**
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* Read a byte in the array.
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*/
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public readByte(): number {
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const data = this.array[this._offset];
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this._offset++;
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return data;
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}
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/**
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* Read the amount of bytes.
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*/
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public read(amount: number): Uint8Array {
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if (this._offset > this.array.length) {
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throw new Error("EOF");
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}
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const data = this.array.slice(this._offset, this._offset + amount);
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this._offset += amount;
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return data;
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}
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}
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