StringSink
Documentation |
#include <cryptopp/filters.h> |
A StringSink serves as a destination for string data in the pipelining paradigm. The data can be binary or ASCII.
The StringSink takes a reference to a string. Because a reference is taken, the StringSink doe not own output, and therefore will not destroy output. See ownership for more details.
A StringSink is a specialization of StringSinkTemplate and declared in filters.h as:
typedef StringSinkTemplate<std::string> StringSink;
Constructors
StringSink(string &output)
output is the string to store the data. The sink can store binary or ASCII data in the string.
Examples
The following example demonstrates creation of a StringSink.
string s; StringSink sink( s );
The following example demonstrates reading a file using a FileSource, and placing the contents of the file in a string. This is known as pipelining.
string s; FileSource file( filename, true, new StringSink( s ) ); cout << s << endl;
true indicates the FileSource should porpagate to all filters in the chain. A slightly more complicated example of pipelining is below. Before the FileSource is placed in the string, it is hex encoded.
string s; FileSource( filename, true, new HexEncoder( new StringSink( s ) ) ); cout << s << endl;
From above, note that the HexEncoder and StringSink created with new do not require explicit destruction - the FileSource will call delete on the HexEncoder, which in turns calls delete on the StringSink when it (the FileSource) is destroyed.
byte data[] = { 0x00, 0x01, 0x02, 0x03 }; string sink; HexEncoder encoder; encoder.Attach( new StringSink( sink ) ); encoder.Put( data, sizeof( data ) ); encoder.MessageEnd(); cout << sink << endl;
At times, Crypto++ will require a reference to a BufferedTransformation object. For example, when saving a key to storage. To accomodate, StringSink offers Ref:
AutoSeededRandomPool rng; // Generate Private Key DSA::PrivateKey PrivateKey; PrivateKey.GenerateRandomWithKeySize(rng, 1024); ... string encodedPrivateKey; // DER Encode Keys (PKCS #8) PrivateKey.Save( StringSink(encodedPrivateKey).Ref() ); ...