@file      bio_unbase64.c
   @author    Mitch Richling <https://www.mitchr.me/>
   @Copyright Copyright 2008 by Mitch Richling.  All rights reserved.
   @Revision  $Revision$ 
   @SCMdate   $Date$
   @brief     OpenSSL, BIO base64 decode example.@EOL
   @Keywords  none
   @Std       C89

              This program illustrates how to chain a BIO filter
              object to an output BIO object to seamlessly base64
              encode data passing through.  See bio_base64.c for an
              example of how to encode base64.

#include <openssl/ssl.h>
#include <openssl/bio.h>

int main(int argc, char *argv[]);

int main(int argc, char *argv[]) {

  BIO *bio_stdin, *bio_base64, *bio_stdout;
  char buf[512];
  int inlen;

  /* Creat two BIO objects */
  bio_stdin  = BIO_new_fp(stdin,  BIO_NOCLOSE);
  bio_stdout = BIO_new_fp(stdout, BIO_NOCLOSE);

  /* Create a base64 filter and connect it to the stdin bio */
  bio_base64 = BIO_new(BIO_f_base64());
  bio_stdin = BIO_push(bio_base64, bio_stdin);

  /* Now read from our in bio and write to out out bio. */
  while((inlen = BIO_read(bio_stdin, buf, 512)) > 0) {
    BIO_write(bio_stdout, buf, inlen);
  } /* end while */

  /* Tell the base64 bio that we are done, and to flush the rest */

  /* Use BIO_free_all to free whole chain (the stdout and bio_base64 too. */
  /* BIO_free is good enough here, but free_all wouild work too. */

  return 0;
} /* end func main */