107 lines
3.3 KiB
JavaScript
107 lines
3.3 KiB
JavaScript
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"use strict";
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var utils = require("./utils");
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var support = require("./support");
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// private property
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var _keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
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// public method for encoding
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exports.encode = function(input) {
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var output = [];
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var chr1, chr2, chr3, enc1, enc2, enc3, enc4;
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var i = 0, len = input.length, remainingBytes = len;
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var isArray = utils.getTypeOf(input) !== "string";
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while (i < input.length) {
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remainingBytes = len - i;
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if (!isArray) {
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chr1 = input.charCodeAt(i++);
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chr2 = i < len ? input.charCodeAt(i++) : 0;
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chr3 = i < len ? input.charCodeAt(i++) : 0;
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} else {
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chr1 = input[i++];
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chr2 = i < len ? input[i++] : 0;
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chr3 = i < len ? input[i++] : 0;
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}
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enc1 = chr1 >> 2;
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enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
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enc3 = remainingBytes > 1 ? (((chr2 & 15) << 2) | (chr3 >> 6)) : 64;
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enc4 = remainingBytes > 2 ? (chr3 & 63) : 64;
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output.push(_keyStr.charAt(enc1) + _keyStr.charAt(enc2) + _keyStr.charAt(enc3) + _keyStr.charAt(enc4));
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}
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return output.join("");
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};
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// public method for decoding
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exports.decode = function(input) {
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var chr1, chr2, chr3;
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var enc1, enc2, enc3, enc4;
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var i = 0, resultIndex = 0;
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var dataUrlPrefix = "data:";
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if (input.substr(0, dataUrlPrefix.length) === dataUrlPrefix) {
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// This is a common error: people give a data url
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// (data:image/png;base64,iVBOR...) with a {base64: true} and
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// wonders why things don't work.
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// We can detect that the string input looks like a data url but we
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// *can't* be sure it is one: removing everything up to the comma would
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// be too dangerous.
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throw new Error("Invalid base64 input, it looks like a data url.");
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}
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input = input.replace(/[^A-Za-z0-9+/=]/g, "");
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var totalLength = input.length * 3 / 4;
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if(input.charAt(input.length - 1) === _keyStr.charAt(64)) {
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totalLength--;
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}
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if(input.charAt(input.length - 2) === _keyStr.charAt(64)) {
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totalLength--;
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}
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if (totalLength % 1 !== 0) {
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// totalLength is not an integer, the length does not match a valid
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// base64 content. That can happen if:
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// - the input is not a base64 content
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// - the input is *almost* a base64 content, with a extra chars at the
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// beginning or at the end
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// - the input uses a base64 variant (base64url for example)
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throw new Error("Invalid base64 input, bad content length.");
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}
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var output;
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if (support.uint8array) {
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output = new Uint8Array(totalLength|0);
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} else {
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output = new Array(totalLength|0);
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}
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while (i < input.length) {
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enc1 = _keyStr.indexOf(input.charAt(i++));
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enc2 = _keyStr.indexOf(input.charAt(i++));
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enc3 = _keyStr.indexOf(input.charAt(i++));
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enc4 = _keyStr.indexOf(input.charAt(i++));
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chr1 = (enc1 << 2) | (enc2 >> 4);
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chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
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chr3 = ((enc3 & 3) << 6) | enc4;
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output[resultIndex++] = chr1;
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if (enc3 !== 64) {
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output[resultIndex++] = chr2;
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}
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if (enc4 !== 64) {
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output[resultIndex++] = chr3;
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}
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}
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return output;
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};
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