pdf-lib
Version:
Create and modify PDF files with JavaScript
84 lines • 3 kB
JavaScript
/*
* The `chars`, `lookup`, `encode`, and `decode` members of this file are
* licensed under the following:
*
* base64-arraybuffer
* https://github.com/niklasvh/base64-arraybuffer
*
* Copyright (c) 2012 Niklas von Hertzen
* Licensed under the MIT license.
*
*/
var chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
// Use a lookup table to find the index.
var lookup = new Uint8Array(256);
for (var i = 0; i < chars.length; i++) {
lookup[chars.charCodeAt(i)] = i;
}
export var encodeToBase64 = function (bytes) {
var base64 = '';
var len = bytes.length;
for (var i = 0; i < len; i += 3) {
base64 += chars[bytes[i] >> 2];
base64 += chars[((bytes[i] & 3) << 4) | (bytes[i + 1] >> 4)];
base64 += chars[((bytes[i + 1] & 15) << 2) | (bytes[i + 2] >> 6)];
base64 += chars[bytes[i + 2] & 63];
}
if (len % 3 === 2) {
base64 = base64.substring(0, base64.length - 1) + '=';
}
else if (len % 3 === 1) {
base64 = base64.substring(0, base64.length - 2) + '==';
}
return base64;
};
export var decodeFromBase64 = function (base64) {
var bufferLength = base64.length * 0.75;
var len = base64.length;
var i;
var p = 0;
var encoded1;
var encoded2;
var encoded3;
var encoded4;
if (base64[base64.length - 1] === '=') {
bufferLength--;
if (base64[base64.length - 2] === '=') {
bufferLength--;
}
}
var bytes = new Uint8Array(bufferLength);
for (i = 0; i < len; i += 4) {
encoded1 = lookup[base64.charCodeAt(i)];
encoded2 = lookup[base64.charCodeAt(i + 1)];
encoded3 = lookup[base64.charCodeAt(i + 2)];
encoded4 = lookup[base64.charCodeAt(i + 3)];
bytes[p++] = (encoded1 << 2) | (encoded2 >> 4);
bytes[p++] = ((encoded2 & 15) << 4) | (encoded3 >> 2);
bytes[p++] = ((encoded3 & 3) << 6) | (encoded4 & 63);
}
return bytes;
};
// This regex is designed to be as flexible as possible. It will parse certain
// invalid data URIs.
var DATA_URI_PREFIX_REGEX = /^(data)?:?([\w\/\+]+)?;?(charset=[\w-]+|base64)?.*,/i;
/**
* If the `dataUri` input is a data URI, then the data URI prefix must not be
* longer than 100 characters, or this function will fail to decode it.
*
* @param dataUri a base64 data URI or plain base64 string
* @returns a Uint8Array containing the decoded input
*/
export var decodeFromBase64DataUri = function (dataUri) {
var trimmedUri = dataUri.trim();
var prefix = trimmedUri.substring(0, 100);
var res = prefix.match(DATA_URI_PREFIX_REGEX);
// Assume it's not a data URI - just a plain base64 string
if (!res)
return decodeFromBase64(trimmedUri);
// Remove the data URI prefix and parse the remainder as a base64 string
var fullMatch = res[0];
var data = trimmedUri.substring(fullMatch.length);
return decodeFromBase64(data);
};
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