decodebase64.js

decodebase64.js

import { ERRORTYPES as error } from "./error";

export default function decodebase64(str) {
  function atob(input) {
    var str = String(input).replace(/=+$/, "");
    if (str.length % 4 == 1) {
      return error.value;
    }
    for (

initialize result and counters

      var bc = 0, bs, buffer, idx = 0, output = "";

¶

get next character
```
      (buffer = str.charAt(idx++));
```

character found in table? initialize bit storage and add its ascii value;

      ~buffer &&
      ((bs = bc % 4 ? bs * 64 + buffer : buffer),

and if not first of each 4 characters, convert the first 8 bits to one ascii character

      bc++ % 4)
        ? (output += String.fromCharCode(255 & (bs >> ((-2 * bc) & 6))))
        : 0
    ) {

try to find character in table (0-63, not found => -1)

      buffer = chars.indexOf(buffer);
    }
    return output;
  }

  if (typeof window !== "undefined" && typeof atob !== "undefined") {
    return window.atob(str);
  } else if (typeof module !== "undefined" && module.exports) {
    return new Buffer(str, "base64").toString();
  } else {
    var chars =
      "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

    return atob(str);
  }
}