140 lines
3.9 KiB
JavaScript
140 lines
3.9 KiB
JavaScript
"use strict";
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/**
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* A minimal base64 implementation for number arrays.
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* @memberof util
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* @namespace
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*/
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var base64 = exports;
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/**
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* Calculates the byte length of a base64 encoded string.
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* @param {string} string Base64 encoded string
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* @returns {number} Byte length
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*/
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base64.length = function length(string) {
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var p = string.length;
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if (!p)
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return 0;
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var n = 0;
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while (--p % 4 > 1 && string.charAt(p) === "=")
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++n;
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return Math.ceil(string.length * 3) / 4 - n;
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};
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// Base64 encoding table
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var b64 = new Array(64);
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// Base64 decoding table
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var s64 = new Array(123);
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// 65..90, 97..122, 48..57, 43, 47
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for (var i = 0; i < 64;)
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s64[b64[i] = i < 26 ? i + 65 : i < 52 ? i + 71 : i < 62 ? i - 4 : i - 59 | 43] = i++;
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/**
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* Encodes a buffer to a base64 encoded string.
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* @param {Uint8Array} buffer Source buffer
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* @param {number} start Source start
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* @param {number} end Source end
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* @returns {string} Base64 encoded string
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*/
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base64.encode = function encode(buffer, start, end) {
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var parts = null,
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chunk = [];
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var i = 0, // output index
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j = 0, // goto index
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t; // temporary
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while (start < end) {
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var b = buffer[start++];
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switch (j) {
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case 0:
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chunk[i++] = b64[b >> 2];
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t = (b & 3) << 4;
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j = 1;
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break;
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case 1:
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chunk[i++] = b64[t | b >> 4];
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t = (b & 15) << 2;
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j = 2;
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break;
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case 2:
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chunk[i++] = b64[t | b >> 6];
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chunk[i++] = b64[b & 63];
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j = 0;
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break;
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}
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if (i > 8191) {
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(parts || (parts = [])).push(String.fromCharCode.apply(String, chunk));
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i = 0;
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}
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}
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if (j) {
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chunk[i++] = b64[t];
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chunk[i++] = 61;
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if (j === 1)
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chunk[i++] = 61;
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}
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if (parts) {
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if (i)
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parts.push(String.fromCharCode.apply(String, chunk.slice(0, i)));
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return parts.join("");
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}
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return String.fromCharCode.apply(String, chunk.slice(0, i));
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};
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var invalidEncoding = "invalid encoding";
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/**
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* Decodes a base64 encoded string to a buffer.
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* @param {string} string Source string
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* @param {Uint8Array} buffer Destination buffer
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* @param {number} offset Destination offset
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* @returns {number} Number of bytes written
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* @throws {Error} If encoding is invalid
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*/
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base64.decode = function decode(string, buffer, offset) {
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var start = offset;
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var j = 0, // goto index
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t; // temporary
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for (var i = 0; i < string.length;) {
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var c = string.charCodeAt(i++);
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if (c === 61 && j > 1)
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break;
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if ((c = s64[c]) === undefined)
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throw Error(invalidEncoding);
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switch (j) {
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case 0:
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t = c;
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j = 1;
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break;
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case 1:
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buffer[offset++] = t << 2 | (c & 48) >> 4;
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t = c;
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j = 2;
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break;
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case 2:
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buffer[offset++] = (t & 15) << 4 | (c & 60) >> 2;
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t = c;
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j = 3;
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break;
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case 3:
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buffer[offset++] = (t & 3) << 6 | c;
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j = 0;
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break;
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}
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}
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if (j === 1)
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throw Error(invalidEncoding);
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return offset - start;
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};
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/**
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* Tests if the specified string appears to be base64 encoded.
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* @param {string} string String to test
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* @returns {boolean} `true` if probably base64 encoded, otherwise false
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*/
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base64.test = function test(string) {
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return /^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?$/.test(string);
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};
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