x::gcrypt::md
provides access to message digest or hash algorithms, such as MD5.
Methods and functions that use message digests generally message
digests specified by their
Libgcrypt identifiers, like GCRY_MD_MD5 or by name, like
“md5”.
#include <x/gcrypt/md.H> #include <x/join.H> std::set<std::string> algos; x::gcrypt::md::base::enumerate(algos); std::cout << join(algos, ", ") << std::endl;
enumerate() returns the names of all message digest
algorithms implemented in Libgcrypt.
The
name() and
number() functions
convert message digest names to
their assigned identifiers.
auto md=x::gcrypt::md::create("md5"); md->write(&buffer[0], buffer.size()); std::vector<unsigned char> digest; md->digest(digest);
x::gcrypt::md's methods are generally equivalent
to their gcry_md namesakes in Libgcrypt. The
notable differences are:
The reference-counted object's constructor creates the internal
Libgcrypt handle for the message digest, and the destructor
destroys it.
Passing another x::gcrypt::md
to the constructor ends up duplicating the message digest handle
using gcry_md_copy():
auto md1=x::gcrypt::md::create("md5"); // ... auto md2=x::gcrypt::md::create(md);
Errors are reported by throwing exceptions.
An overloaded digest() returns the digest in a
constructed
reference-counted vector:
#include <x/vector.H> x::vector<unsigned char> digest=md->digest();
hexdigest() converts the raw, binary, digest
into a hexadecimal string, using lowercase letters:
#include <x/vector.H> std::string h=md->hexdigest();
A more C++-ish way to calculate a digest is by using iterators.
x::gcrypt::md::base::iterator md5("md5"); *md5++='a'; *md5++='b'; *md5++='c'; auto digest=md5.digest(); std::string hexdigest=md5.hexdigest();
x::gcrypt::md::base::iterator
is an output iterator.
Iterating over an octet stream feeds it as the input for
the message digest hash.
std::vector<char> container; // ... auto digest=std::copy(container.begin(), container.end(), x::gcrypt::md::base::iterator("md5")).digest();
This example calculates an MD5 digest for a container, in one shot.