mirror of
https://github.com/IfcOpenShell/IfcOpenShell.git
synced 2026-08-09 09:21:46 +00:00
Thomas Krijnen
108 lines
4.3 KiB
C++
108 lines
4.3 KiB
C++
/********************************************************************************
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* *
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* This file is part of IfcOpenShell. *
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* *
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* IfcOpenShell is free software: you can redistribute it and/or modify *
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* it under the terms of the Lesser GNU General Public License as published by *
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* the Free Software Foundation, either version 3.0 of the License, or *
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* (at your option) any later version. *
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* *
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* IfcOpenShell is distributed in the hope that it will be useful, *
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* but WITHOUT ANY WARRANTY; without even the implied warranty of *
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
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* Lesser GNU General Public License for more details. *
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* *
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* You should have received a copy of the Lesser GNU General Public License *
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* along with this program. If not, see <http://www.gnu.org/licenses/>. *
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* *
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********************************************************************************/
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/********************************************************************************
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* *
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* Please consider this a placeholder for an actual GlobalId generation *
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* algorithm. A real implementation could for example be based on Boost::uuid *
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* *
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********************************************************************************/
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#include <time.h>
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#include <stdlib.h>
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#include <algorithm>
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#include <boost/uuid/uuid.hpp>
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#include <boost/uuid/uuid_generators.hpp>
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#include <boost/uuid/uuid_io.hpp>
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#include "../ifcparse/IfcWrite.h"
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#include "../ifcparse/IfcException.h"
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static const char* chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz_$";
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// Converts an unsigned integer into a base64 string of length l
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std::string base64(unsigned v, int l) {
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std::string r;
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r.reserve(l);
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while ( v ) {
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r.push_back(chars[v%64]);
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v /= 64;
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}
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while ( r.size() != l ) r.push_back('0');
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std::reverse(r.begin(),r.end());
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return r;
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}
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// Converts a base64 string into an unsigned integer
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unsigned from_base64(const std::string& s) {
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std::string::size_type zeros = s.find_first_not_of('0');
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unsigned r = 0;
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if ( zeros != std::string::npos )
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for ( std::string::const_iterator i = s.begin()+zeros; i != s.end(); ++ i ) {
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r *= 64;
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const char* c = strchr(chars,*i);
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if ( !c ) throw IfcParse::IfcException("Failed to decode GlobalId");
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r += (c-chars);
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}
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return r;
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}
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// Compresses the UUID byte array into a base64 representation
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std::string compress(unsigned char* v) {
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std::string r;
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r.reserve(22);
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r += base64(v[0],2);
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for ( unsigned i = 1; i < 16; i += 3 ) {
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r += base64((v[i]<<16) + (v[i+1]<<8) + v[i+2],4);
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}
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return r;
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}
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// Expands the base64 representation into a UUID byte array
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void expand(const std::string& s, std::vector<unsigned char>& v) {
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v.push_back(from_base64(s.substr(0,2)));
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for( unsigned i = 0; i < 5; ++i ) {
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unsigned d = from_base64(s.substr(2+4*i,4));
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for ( unsigned j = 0; j < 3; ++ j ) {
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v.push_back((d>>(8*(2-j))) % 256);
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}
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}
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}
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// A random number generator for the UUID
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static boost::uuids::basic_random_generator<boost::mt19937> gen;
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IfcWrite::IfcGuidHelper::IfcGuidHelper() {
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boost::uuids::uuid u = gen();
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std::vector<unsigned char> v(u.size());
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std::copy(u.begin(), u.end(), v.begin());
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data = compress(&v[0]);
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std::vector<unsigned char> v2;
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expand(data,v2);
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boost::uuids::uuid u2;
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std::copy(v2.begin(), v2.end(), u2.begin());
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}
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IfcWrite::IfcGuidHelper::operator std::string() const {
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return data;
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}
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bool IfcWrite::IfcGuidHelper::seeded = false;
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