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/**************************************************************************
* *
* Regina - A Normal Surface Theory Calculator *
* Computational Engine *
* *
* Copyright (c) 1999-2025, Ben Burton *
* For further details contact Ben Burton (bab@debian.org). *
* *
* 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; either version 2 of the *
* License, or (at your option) any later version. *
* *
* As an exception, when this program is distributed through (i) the *
* App Store by Apple Inc.; (ii) the Mac App Store by Apple Inc.; or *
* (iii) Google Play by Google Inc., then that store may impose any *
* digital rights management, device limits and/or redistribution *
* restrictions that are required by its terms of service. *
* *
* 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, see <https://www.gnu.org/licenses/>. *
* *
**************************************************************************/
#include <cstdio>
#include <cstring>
#include <fstream>
#include <iostream>
#include "file/fileinfo.h"
#include "utilities/zstr.h"
namespace regina {
#define STARTS_FALSE 0
#define STARTS_TRUE 1
#define STARTS_COULD_NOT_OPEN 2
namespace {
/**
* Does the given file begin with the given set of characters?
*
* Returns STARTS_FALSE, STARTS_TRUE or STARTS_COULD_NOT_OPEN.
*/
int fileStartsWith(const char* file, const char* prefix) {
FILE* f = fopen(file, "rb");
if (! f)
return STARTS_COULD_NOT_OPEN;
int ans = STARTS_FALSE;
size_t len = strlen(prefix);
char* buf = new char[len];
if (fread(buf, sizeof(char), len, f) == len)
if (strncmp(buf, prefix, len) == 0)
ans = STARTS_TRUE;
delete[] buf;
fclose(f);
return ans;
}
}
std::optional<FileInfo> FileInfo::identify(std::string idPathname) {
// Check for an XML file.
int starts = fileStartsWith(idPathname.c_str(), "<?xml");
if (starts == STARTS_COULD_NOT_OPEN)
return std::nullopt;
bool compressed = false;
if (starts != STARTS_TRUE) {
// Try for compressed XML.
std::ifstream file(idPathname.c_str(),
std::ios_base::in | std::ios_base::binary);
if (! file)
return std::nullopt;
try {
zstr::istream in(file);
std::string s;
in >> s;
if ((! in.eof()) && (s == "<?xml"))
compressed = true;
else
return std::nullopt;
} catch (const zstr::Exception& e) {
return std::nullopt;
}
}
FileInfo ans;
ans.compressed_ = compressed;
ans.pathname_ = std::move(idPathname);
ans.format_ = FileFormat::Current;
// Note: we cannot use the idPathname argument from here on, since we moved its data out.
// We must use ans.pathname_ instead.
// Make it an invalid file until we know otherwise.
ans.invalid_ = true;
std::ifstream file(ans.pathname_.c_str(),
std::ios_base::in | std::ios_base::binary);
if (! file)
return ans;
try {
zstr::istream in(file); // Can handle compressed or uncompressed.
std::string s;
// Start by slurping in the opening "<?xml".
if (in.eof())
return ans;
in >> s;
if (s != "<?xml")
return ans;
// Hunt for the matching "...?>".
// Try skipping through several strings in case there are extra
// arguments in the XML prologue (such as encoding or standalone
// declarations).
int i;
for (i = 0; ; i++) {
if (in.eof())
return ans;
in >> s;
if (s.length() >= 2 &&
s[s.length() - 2] == '?' &&
s[s.length() - 1] == '>')
break;
// If we can't find it after enough tries, just give up.
// Ten tries should be more than sufficient, since the current XML
// spec supports only version, encoding and standalone arguments
// at present.
if (i >= 10)
return ans;
}
// The next thing we see should be the <reginadata ...> element.
if (in.eof())
return ans;
in >> s;
if (s == "<regina")
ans.format_ = FileFormat::XmlGen3;
else if (s == "<reginadata")
ans.format_ = FileFormat::XmlGen2;
else
return ans;
// Next should be the engine version.
if (in.eof())
return ans;
in >> s;
if (s.length() < 8)
return ans;
if (s.substr(0, 8).compare("engine=\"") != 0)
return ans;
// We've found the engine attribute; extract its value.
std::string::size_type pos = s.find('"', 8);
if (pos == std::string::npos)
return ans;
ans.engine_ = s.substr(8, pos - 8);
} catch (const zstr::Exception& e) {
return ans;
}
// That's as far as we need to go; we've extracted everything we want.
ans.invalid_ = false;
return ans;
}
void FileInfo::writeTextShort(std::ostream& out) const {
out << "Regina data: " << formatDescription();
if (compressed_)
out << ", compressed";
}
void FileInfo::writeTextLong(std::ostream& out) const {
// All supported file types are XML.
out << "Regina data: " << formatDescription();
if (compressed_)
out << ", compressed";
out << '\n';
if (invalid_)
out << "File contains invalid metadata.\n";
else
out << "Engine " << engine_ << '\n';
}
} // namespace regina
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