Crypt.cc

/*
	grive: an GPL program to sync a local directory with Google Drive
	Copyright (C) 2012  Wan Wai Ho

	This program is free software; you can redistribute it and/or
	modify it under the terms of the GNU General Public License
	as published by the Free Software Foundation version 2
	of the License.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program; if not, write to the Free Software
	Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
*/

#include "Crypt.hh"

#include "StdioFile.hh"
#include "Exception.hh"
#include "MemMap.hh"

#include <iomanip>
#include <sstream>

// dependent libraries
#include <gcrypt.h>
#include <boost/throw_exception.hpp>

namespace gr { namespace crypt {

// map 4MB of data at a time
const u64_t read_size = 1024 * 4096 ;

struct MD5::Impl
{
	gcry_md_hd_t hd ;
} ;

MD5::MD5() : m_impl( new Impl )
{
	::gcry_error_t err = ::gcry_md_open( &m_impl->hd, GCRY_MD_MD5, 0 ) ;
	if ( err != GPG_ERR_NO_ERROR )
	{
		BOOST_THROW_EXCEPTION( Exception() << expt::ErrMsg( ::gcry_strerror(err) ) ) ;
	}
}

MD5::~MD5()
{
	::gcry_md_close( m_impl->hd ) ;
}

void MD5::Write( const void *data, std::size_t size )
{
	::gcry_md_write( m_impl->hd, data, size ) ;
}

std::string MD5::Get() const
{
	unsigned char *md5 = ::gcry_md_read( m_impl->hd, GCRY_MD_MD5 ) ;
	unsigned int  len  = ::gcry_md_get_algo_dlen(GCRY_MD_MD5) ;
	
	// format the MD5 string
	std::ostringstream ss ;
	for ( unsigned int i = 0 ; i < len ; i++ )
		ss << std::hex << std::setw(2) << std::setfill('0') << static_cast<int>(md5[i]) ;

	return ss.str() ;
}

std::string MD5::Get( const fs::path& file )
{
	try
	{
		StdioFile sfile( file ) ;
		return Get( sfile ) ;
	}
	catch ( StdioFile::Error& )
	{
		return "" ;
	}
}

std::string MD5::Get( StdioFile& file )
{
	MD5 crypt ;
	
	u64_t size = file.Size() ;
	for ( u64_t i = 0 ; i < size ; i += read_size )
	{
		MemMap map( file, i, static_cast<std::size_t>(std::min(read_size, size-i)) ) ;
		crypt.Write( map.Addr(), map.Length() ) ;
	}

	return crypt.Get() ;
}

} } // end of namespaces