66 lines
1.6 KiB
JavaScript
66 lines
1.6 KiB
JavaScript
var chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
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// Use a lookup table to find the index.
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var lookup = new Uint8Array(256);
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for (var i = 0; i < chars.length; i++) {
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lookup[chars.charCodeAt(i)] = i;
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}
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function encode(arraybuffer) {
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var bytes = new Uint8Array(arraybuffer),
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i,
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len = bytes.length,
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base64 = "";
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for (i = 0; i < len; i += 3) {
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base64 += chars[bytes[i] >> 2];
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base64 += chars[((bytes[i] & 3) << 4) | (bytes[i + 1] >> 4)];
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base64 += chars[((bytes[i + 1] & 15) << 2) | (bytes[i + 2] >> 6)];
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base64 += chars[bytes[i + 2] & 63];
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}
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if (len % 3 === 2) {
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base64 = base64.substring(0, base64.length - 1) + "=";
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} else if (len % 3 === 1) {
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base64 = base64.substring(0, base64.length - 2) + "==";
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}
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return base64;
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}
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function decode(base64) {
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var bufferLength = base64.length * 0.75,
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len = base64.length,
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i,
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p = 0,
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encoded1,
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encoded2,
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encoded3,
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encoded4;
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if (base64[base64.length - 1] === "=") {
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bufferLength--;
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if (base64[base64.length - 2] === "=") {
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bufferLength--;
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}
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}
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var arraybuffer = new ArrayBuffer(bufferLength),
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bytes = new Uint8Array(arraybuffer);
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for (i = 0; i < len; i += 4) {
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encoded1 = lookup[base64.charCodeAt(i)];
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encoded2 = lookup[base64.charCodeAt(i + 1)];
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encoded3 = lookup[base64.charCodeAt(i + 2)];
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encoded4 = lookup[base64.charCodeAt(i + 3)];
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bytes[p++] = (encoded1 << 2) | (encoded2 >> 4);
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bytes[p++] = ((encoded2 & 15) << 4) | (encoded3 >> 2);
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bytes[p++] = ((encoded3 & 3) << 6) | (encoded4 & 63);
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}
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return arraybuffer;
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}
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module.exports = { encode, decode };
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