Mine

svn_error_t *
foo (svn_stream_t* s, apr_pool_t *pool)
{
   unsigned char digest[APR_MD5_DIGESTSIZE];
   svn_stream_t *stream = svn_stream_checksummed (s, digest, NULL, pool);

   return SVN_NO_ERROR;
}


/* MD5 checked stream support */

struct md5_stream_baton
{
  apr_md5_ctx_t read_ctx, write_ctx;
  unsigned char *read_digest;
  unsigned char *write_digest;
  svn_stream_t *proxy;
};


static svn_error_t *
close_handler_md5 (void *baton)
{
  struct md5_stream_baton *btn = baton;
  unsigned char digest[APR_MD5_DIGESTSIZE];

  if (btn->read_digest)
    {
      apr_md5_final (digest, &btn->read_ctx);
      memcpy (btn->read_digest, digest, sizeof (digest));
    }

  if (btn->write_digest)
    {
      apr_md5_final (digest, &btn->write_ctx);
      memcpy (btn->write_digest, digest, sizeof (digest));
    }

  return SVN_NO_ERROR;
}



svn_stream_t *
svn_stream_checksummed (svn_stream_t *stream,
                        unsigned char *read_digest,
                        unsigned char *write_digest,
                        apr_pool_t *pool)
{
  svn_stream_t *s;
  struct md5_stream_baton *baton;

  if (! read_digest && ! write_digest)
    return stream;

  baton = apr_palloc (pool, sizeof (*baton));
  apr_md5_init (&baton->read_ctx);
  apr_md5_init (&baton->write_ctx);
  baton->read_digest = read_digest;
  baton->write_digest = write_digest;
  baton->proxy = stream;

  s = svn_stream_create (baton, pool);
  svn_stream_set_read (s, read_handler_md5);
  svn_stream_set_write (s, write_handler_md5);
  svn_stream_set_close (s, close_handler_md5);
  return s;
}