tarts.js

/*
This is part of the tartJS project license under the Apache License 2.0.

Github - https://github.com/tart/tartJShttps://github.com/tart/tartJS

License -

Copyright 2014 Startup Kitchen. All Rights Reserved.

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.
*/



const headers = {
    name: 100,
    mode: 8,
    uid: 8,
    gid: 8,
    size: 12,
    mtime: 12,
    chksum: 8,
    typeflag: 1,
    linkname: 100,
    magic: 5,
    version: 2,
    uname: 32,
    gname: 32,
    devmajor: 8,
    devminor: 8,
    prefix: 155,
    padding: 12
}

const offsets = {}
Object.keys(headers).reduce((acc, k) => {
    offsets[k] = acc
    return acc + headers[k]
}, 0)

const defaults = (f) => ({
    name: f.name,
    mode: '777',
    uid: 0,
    gid: 0,
    size: f.content.byteLength,
    mtime: Math.floor(Number(new Date()) / 1000),
    chksum: '        ',
    typeflag: '0',
    magic: 'ustar',
    version: '  ',
    uname: '',
    gname: ''
})

const nopad = ['name', 'linkname', 'magic', 'chksum', 'typeflag', 'version', 'uname', 'gname']
const bsize = 512

function pad(s, n) {
    s = s.toString(8)
    return ('000000000000' + s).slice(s.length + 12 - n)
}

function stringToUint8(s) {
    const a = new Uint8Array(s.length)
    for (let i = 0; i < s.length; i++) a[i] = s.charCodeAt(i)
    return a
}

function tarts(files) {
    return files.reduce((a, f) => {
        if (typeof f.content === 'string') f.content = stringToUint8(f.content)
        f = Object.assign(defaults(f), f)
        const b = new Uint8Array(Math.ceil((bsize + f.size) / bsize) * bsize)
        const checksum = Object.keys(headers).reduce((acc, k) => {
            if (!(k in f)) return acc
            const value = stringToUint8(nopad.indexOf(k) > -1 ? f[k] : pad(f[k], headers[k] - 1))
            b.set(value, offsets[k])
            return acc + value.reduce((a, b) => a + b, 0)
        }, 0)
        b.set(stringToUint8(pad(checksum, 7)), offsets.chksum)
        b.set(f.content, bsize)
        const sum = new Uint8Array(a.byteLength + b.byteLength)
        sum.set(a, 0)
        sum.set(b, a.byteLength)
        return sum
    }, new Uint8Array(0))
}

export default tarts