title: Convert base64 decoded string to unsigned char[32]
body: <p>I'm using <a href="https://github.com/floodyberry/ed25519-donna" rel="nofollow noreferrer">ed25519-donna</a> to digitally sign.</p>
  
  <p>The keys are <code>unsigned char[32]</code>, and the signatures are <code>unsigned char[64]</code>.</p>
  
  <p>I've found <a href="https://stackoverflow.com/a/180949/1382306">this base64 encoding</a>, but it only decodes into <code>string</code>.</p>
  
  <p>I've found and tried many techniques but am still unsure of how to convert.</p>
  
  <p>How can a base64 decoded <code>string</code> be converted to an <code>unsigned char[32]</code>?</p>