133 lines
3.1 KiB
JavaScript
133 lines
3.1 KiB
JavaScript
/**
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* Implementation of the [multibase](https://github.com/multiformats/multibase) specification.
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* @module Multibase
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*/
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'use strict'
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const { Buffer } = require('buffer')
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const constants = require('./constants')
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exports = module.exports = multibase
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exports.encode = encode
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exports.decode = decode
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exports.isEncoded = isEncoded
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exports.names = Object.freeze(Object.keys(constants.names))
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exports.codes = Object.freeze(Object.keys(constants.codes))
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const errNotSupported = new Error('Unsupported encoding')
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/**
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* Create a new buffer with the multibase varint+code.
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*
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* @param {string|number} nameOrCode - The multibase name or code number.
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* @param {Buffer} buf - The data to be prefixed with multibase.
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* @memberof Multibase
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* @returns {Buffer}
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*/
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function multibase (nameOrCode, buf) {
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if (!buf) {
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throw new Error('requires an encoded buffer')
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}
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const base = getBase(nameOrCode)
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const codeBuf = Buffer.from(base.code)
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const name = base.name
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validEncode(name, buf)
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return Buffer.concat([codeBuf, buf])
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}
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/**
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* Encode data with the specified base and add the multibase prefix.
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*
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* @param {string|number} nameOrCode - The multibase name or code number.
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* @param {Buffer} buf - The data to be encoded.
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* @returns {Buffer}
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* @memberof Multibase
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*/
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function encode (nameOrCode, buf) {
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const base = getBase(nameOrCode)
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const name = base.name
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return multibase(name, Buffer.from(base.encode(buf)))
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}
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/**
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* Takes a buffer or string encoded with multibase header, decodes it and
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* returns the decoded buffer
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*
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* @param {Buffer|string} bufOrString
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* @returns {Buffer}
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* @memberof Multibase
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*
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*/
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function decode (bufOrString) {
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if (Buffer.isBuffer(bufOrString)) {
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bufOrString = bufOrString.toString()
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}
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const code = bufOrString.substring(0, 1)
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bufOrString = bufOrString.substring(1, bufOrString.length)
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if (typeof bufOrString === 'string') {
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bufOrString = Buffer.from(bufOrString)
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}
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const base = getBase(code)
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return Buffer.from(base.decode(bufOrString.toString()))
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}
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/**
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* Is the given data multibase encoded?
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*
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* @param {Buffer|string} bufOrString
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* @returns {boolean}
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* @memberof Multibase
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*/
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function isEncoded (bufOrString) {
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if (Buffer.isBuffer(bufOrString)) {
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bufOrString = bufOrString.toString()
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}
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// Ensure bufOrString is a string
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if (Object.prototype.toString.call(bufOrString) !== '[object String]') {
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return false
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}
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const code = bufOrString.substring(0, 1)
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try {
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const base = getBase(code)
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return base.name
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} catch (err) {
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return false
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}
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}
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/**
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* @param {string} name
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* @param {Buffer} buf
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* @private
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* @returns {undefined}
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*/
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function validEncode (name, buf) {
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const base = getBase(name)
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base.decode(buf.toString())
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}
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function getBase (nameOrCode) {
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let base
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if (constants.names[nameOrCode]) {
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base = constants.names[nameOrCode]
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} else if (constants.codes[nameOrCode]) {
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base = constants.codes[nameOrCode]
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} else {
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throw errNotSupported
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}
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if (!base.isImplemented()) {
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throw new Error('Base ' + nameOrCode + ' is not implemented yet')
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}
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return base
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}
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