Viewing file:  FileChangeChecker.h (6.3 KB) -rw-r--r--
Select action/file-type:
 (+) |  (+) |  (+) | Code (+) | Session (+) |  (+) | SDB (+) |  (+) |  (+) |  (+) |  (+) |  (+) |
/*
* Phusion Passenger - https://www.phusionpassenger.com/
* Copyright (c) 2010-2018 Phusion Holding B.V.
*
* "Passenger", "Phusion Passenger" and "Union Station" are registered
* trademarks of Phusion Holding B.V.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#ifndef _PASSENGER_CHANGE_FILE_CHECKER_H_
#define _PASSENGER_CHANGE_FILE_CHECKER_H_
#include <string>
#include <cerrno>
#include <Utils/CachedFileStat.hpp>
#include <SystemTools/SystemTime.h>
namespace Passenger {
using namespace std;
using namespace oxt;
/**
* A utility class for checking for file changes. Example:
*
* @code
* FileChangeChecker checker;
* checker.changed("foo.txt"); // false
* writeToFile("foo.txt");
* checker.changed("foo.txt"); // true
* checker.changed("foo.txt"); // false
* @endcode
*
* FileChangeChecker uses stat() to retrieve file information. It also
* supports throttling in order to limit the number of actual stat() calls.
* This can improve performance on systems where disk I/O is a problem.
*/
class FileChangeChecker {
private:
struct Entry {
string filename;
time_t lastMtime;
time_t lastCtime;
Entry(const string &filename) {
this->filename = filename;
this->lastMtime = 0;
this->lastCtime = 0;
}
};
typedef boost::shared_ptr<Entry> EntryPtr;
typedef list<EntryPtr> EntryList;
typedef map<string, EntryList::iterator> EntryMap;
CachedFileStat cstat;
unsigned int maxSize;
EntryList entries;
EntryMap fileToEntry;
public:
/**
* Create a FileChangeChecker object.
*
* @param maxSize The maximum size of the internal file list. A size of 0 means unlimited.
*/
FileChangeChecker(unsigned int maxSize = 0)
: cstat(maxSize)
{
this->maxSize = maxSize;
}
/**
* Checks whether, since the last call to changed() with this filename,
* the file's timestamp has changed or whether the file has been created
* or removed. If the stat() call fails for any other reason (e.g. the
* directory is not readable) then this method will return false.
*
* If this method was called with this filename for the first time, or if
* information about this file has since been removed from the internal
* file list, then this method will return whether the file is stat()-able.
* That is, if the file doesn't exist then it will return false, but if
* the directory is not readable then it will also return false.
*
* @param filename The file to check. Note that two different filename
* strings are treated as two different files, so you should
* use absolute filenames if you change working directory
* often.
* @param throttleRate When set to a non-zero value, throttling will be
* enabled. stat() will be called at most once per
* throttleRate seconds.
* @throws TimeRetrievalException Something went wrong while retrieving the
* system time.
* @throws boost::thread_interrupted
*/
bool changed(const string &filename, unsigned int throttleRate = 0) {
EntryMap::iterator it(fileToEntry.find(filename));
EntryPtr entry;
struct stat buf;
bool result, newEntry = false;
int ret;
if (it == fileToEntry.end()) {
// Filename not in file list.
// If file list is full, remove the least recently used
// file list entry.
if (maxSize != 0 && fileToEntry.size() == maxSize) {
EntryList::iterator listEnd(entries.end());
listEnd--;
string filename((*listEnd)->filename);
entries.pop_back();
fileToEntry.erase(filename);
}
// Add to file list as most recently used.
entry = EntryPtr(new Entry(filename));
entries.push_front(entry);
fileToEntry[filename] = entries.begin();
newEntry = true;
} else {
// Filename is in file list.
entry = *it->second;
// Mark this entry as most recently used.
entries.erase(it->second);
entries.push_front(entry);
fileToEntry[filename] = entries.begin();
}
ret = cstat.stat(filename, &buf, throttleRate);
if (newEntry) {
// The file's information isn't in the file list.
if (ret == -1) {
entry->lastMtime = 0;
entry->lastCtime = 0;
return false;
} else {
entry->lastMtime = buf.st_mtime;
entry->lastCtime = buf.st_ctime;
return true;
}
} else {
// The file's information was already in the file list.
if (ret == -1 && errno == ENOENT) {
result = false;
entry->lastMtime = 0;
entry->lastCtime = 0;
} else if (ret == -1) {
result = false;
} else {
result = entry->lastMtime != buf.st_mtime || entry->lastCtime != buf.st_ctime;
entry->lastMtime = buf.st_mtime;
entry->lastCtime = buf.st_ctime;
}
return result;
}
}
/**
* Change the maximum size of the internal file list.
*
* A size of 0 means unlimited.
*/
void setMaxSize(unsigned int maxSize) {
if (maxSize != 0) {
int toRemove = fileToEntry.size() - maxSize;
for (int i = 0; i < toRemove; i++) {
string filename(entries.back()->filename);
entries.pop_back();
fileToEntry.erase(filename);
}
}
this->maxSize = maxSize;
cstat.setMaxSize(maxSize);
}
/**
* Returns whether <tt>filename</tt> is in the internal file list.
*/
bool knows(const string &filename) const {
return fileToEntry.find(filename) != fileToEntry.end();
}
};
} // namespace Passenger
#endif /* _PASSENGER_CHANGE_FILE_CHECKER_H_ */
|