Use case for the BASE64 encoding

base64_usage.cpp

/*
  USE CASE: Set the Authorization header value in the HTTP response
            to the Basic Authentication challenge.

  EXAMPLE: Request headers:
             WWW-Authenticate: Basic realm="WallyWorld"
           Response headers:
             Authorization: Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==
 */

// Username and password to compute the credentials.
string username = ...,
       password = ...;

// Compute the header value by concatenating and converting complete strings.
string credentials = "Basic " +
    base64::encode<char>(username + ":" + password);
request << header("Authorization", credentials);

// Compute the header value by appending the complete encoded basic
// credentials to the credentials value.
string credentials = "Basic ";
base64::encode(username + ":" + password,
               back_inserter(credentials));
request << header("Authorization", credentials);

// Compute the header value by appending the complete encoded basic
// credentials to the credentials stream.
stringstream credentials;
credentials << "Basic ";
base64::encode(username + ":" + password,
               ostream_iterator<char>(credentials));
request << header("Authorization", credentials.str());

// Compute the header value by appending the encoded basic credentials
// to the credentials value.  Use stateful methods to encode by chunks.
string credentials = "Basic ";
back_insert_iterator<string> appender(credentials);
base64::state<char> rest;
base64::encode(username, appender, rest);
base64::encode(":", appender, rest);
base64::encode(password, appender, rest);
base64::encode_rest(appender, rest);
request << header("Authorization", credentials);

// Compute the header value by appending the encoded basic credentials
// to the credentials stream.  Use stateful methods to encode by chunks.
stringstream credentials;
credentials << "Basic ";
ostream_iterator<char> appender(credentials);
base64::encode(username, appender, rest);
base64::encode(":", appender, rest);
base64::encode(password, appender, rest);
base64::encode_rest(appender, rest);
request << header("Authorization", credentials.str());

// Compute the header value by writing the encoded basic credentials
// to the credentials stream.  Use manipulators to encode by chunks.
stringstream credentials;
credentials << "Basic " <<
               base64::io::encode(username) <<
               base64::io::encode(":") <<
               base64::io::encode(password) <<
               base64::encode_rest<char>;
request << header("Authorization", credentials.str());

Using the method overloads with state may seem too cumbersome in this example, because they're to be used more when all the input is not available at the same time, like the credentials here.