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Add additional comments to bookmarklet

This commit is contained in:
Jacob Strieb 2020-08-01 16:31:24 -04:00
parent f3653f8bc7
commit 0d82cb9822
1 changed files with 15 additions and 0 deletions
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15
bookmarklet.js
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@ -1,6 +1,7 @@
javascript:(() => { javascript:(() => {
/* Generate the b64 API functions */ /* Generate the b64 API functions */
var b64 = (() => { var b64 = (() => {
/* Generate a dictionary with {key: val} as {character: index in input string} */
function generateIndexDict(a) { function generateIndexDict(a) {
let result = {}; let result = {};
for (let i = 0; i < a.length; i++) { for (let i = 0; i < a.length; i++) {
@ -8,6 +9,8 @@ javascript:(() => {
} }
return result; return result;
} }
/* Decode URL safe even though it is not the primary encoding mechanism */
const _a = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; const _a = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
const _aRev = generateIndexDict(_a); const _aRev = generateIndexDict(_a);
_aRev["-"] = _aRev["+"]; _aRev["-"] = _aRev["+"];
@ -17,15 +20,19 @@ javascript:(() => {
const _dec = new TextDecoder("utf-8"); const _dec = new TextDecoder("utf-8");
return { return {
/* Decode base64 to a string */
encode: function(s) { encode: function(s) {
return this.binaryToBase64(this.asciiToBinary(s)); return this.binaryToBase64(this.asciiToBinary(s));
}, },
/* Convert a string to a Uint8Array */
asciiToBinary: function(text) { asciiToBinary: function(text) {
return _enc.encode(text); return _enc.encode(text);
}, },
/* Return a base64-encoded string from a Uint8Array input */
binaryToBase64: function(originalBytes) { binaryToBase64: function(originalBytes) {
/* Pad the output array to a multiple of 3 bytes */
let length = originalBytes.length; let length = originalBytes.length;
let added = (length % 3 == 0) ? 0 : (3 - length % 3); let added = (length % 3 == 0) ? 0 : (3 - length % 3);
let bytes = new Uint8Array(length + added); let bytes = new Uint8Array(length + added);
@ -33,12 +40,19 @@ javascript:(() => {
let output = ""; let output = "";
for (let i = 0; i < bytes.length; i += 3) { for (let i = 0; i < bytes.length; i += 3) {
/*
Convert 3 8-bit bytes into 4 6-bit indices and get a character from
the master list based on each 6-bit index
3 x 8-bit: |------ --|---- ----|-- ------|
=> 4 x 6-bit: |------|-- ----|---- --|------|
*/
output += _a[ bytes[i] >>> 2 ]; output += _a[ bytes[i] >>> 2 ];
output += _a[ ((bytes[i] & 0x3) << 4) | (bytes[i + 1] >>> 4) ]; output += _a[ ((bytes[i] & 0x3) << 4) | (bytes[i + 1] >>> 4) ];
output += _a[ ((bytes[i + 1] & 0xF) << 2) | (bytes[i + 2] >>> 6) ]; output += _a[ ((bytes[i + 1] & 0xF) << 2) | (bytes[i + 2] >>> 6) ];
output += _a[ bytes[i + 2] & 0x3F ]; output += _a[ bytes[i + 2] & 0x3F ];
} }
/* Turn the final "A" characters into "=" depending on necessary padding */
if (added > 0) { if (added > 0) {
output = output.slice(0, -added) + ("=".repeat(added)); output = output.slice(0, -added) + ("=".repeat(added));
} }
@ -52,6 +66,7 @@ javascript:(() => {
var api = { var api = {
VERSION: "0.2.0", VERSION: "0.2.0",
/* Return a link to view the page */
getViewLink: function(pageData) { getViewLink: function(pageData) {
var urlData = { var urlData = {
version: this.VERSION, version: this.VERSION,