/********************************************************************************

* *

* This file is part of IfcOpenShell. *

* *

* IfcOpenShell is free software: you can redistribute it and/or modify *

* it under the terms of the Lesser GNU General Public License as published by *

* the Free Software Foundation, either version 3.0 of the License, or *

* (at your option) any later version. *

* *

* IfcOpenShell 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 *

* Lesser GNU General Public License for more details. *

* *

* You should have received a copy of the Lesser GNU General Public License *

* along with this program. If not, see <http://www.gnu.org/licenses/>. *

* *

********************************************************************************/

/********************************************************************************

* *

* Please consider this a placeholder for an actual GlobalId generation *

* algorithm. A real implementation could for example be based on Boost::uuid *

* *

********************************************************************************/

#include <time.h>

#include <stdlib.h>

#include <algorithm>

#include <boost/uuid/uuid.hpp>

#include <boost/uuid/uuid_generators.hpp>

#include <boost/uuid/uuid_io.hpp>

#include "../ifcparse/IfcWrite.h"

#include "../ifcparse/IfcException.h"

static const char* chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz_$";

// Converts an unsigned integer into a base64 string of length l

std::string base64(unsigned v, int l) {

std::string r;

r.reserve(l);

while ( v ) {

r.push_back(chars[v%64]);

v /= 64;

}

while ( r.size() != l ) r.push_back('0');

std::reverse(r.begin(),r.end());

return r;

}

// Converts a base64 string into an unsigned integer

unsigned from_base64(const std::string& s) {

std::string::size_type zeros = s.find_first_not_of('0');

unsigned r = 0;

if ( zeros != std::string::npos )

for ( std::string::const_iterator i = s.begin()+zeros; i != s.end(); ++ i ) {

r *= 64;

const char* c = strchr(chars,*i);

if ( !c ) throw IfcParse::IfcException("Failed to decode GlobalId");

r += (c-chars);

}

return r;

}

// Compresses the UUID byte array into a base64 representation

std::string compress(unsigned char* v) {

std::string r;

r.reserve(22);

r += base64(v[0],2);

for ( unsigned i = 1; i < 16; i += 3 ) {

r += base64((v[i]<<16) + (v[i+1]<<8) + v[i+2],4);

}

return r;

}

// Expands the base64 representation into a UUID byte array

void expand(const std::string& s, std::vector<unsigned char>& v) {

v.push_back(from_base64(s.substr(0,2)));

for( unsigned i = 0; i < 5; ++i ) {

unsigned d = from_base64(s.substr(2+4*i,4));

for ( unsigned j = 0; j < 3; ++ j ) {

v.push_back((d>>(8*(2-j))) % 256);

}

}

}

// A random number generator for the UUID

static boost::uuids::basic_random_generator<boost::mt19937> gen;

IfcWrite::IfcGuidHelper::IfcGuidHelper() {

boost::uuids::uuid u = gen();

std::vector<unsigned char> v(u.size());

std::copy(u.begin(), u.end(), v.begin());

data = compress(&v[0]);

std::vector<unsigned char> v2;

expand(data,v2);

boost::uuids::uuid u2;

std::copy(v2.begin(), v2.end(), u2.begin());

}

IfcWrite::IfcGuidHelper::operator std::string() const {

return data;

}

bool IfcWrite::IfcGuidHelper::seeded = false;