Mercurial > hg > svcore
view data/fileio/CachedFile.cpp @ 468:70b333085952
* complete switching the code to use CachedFile -- now to tidy & fix the
remaining flaws...
author | Chris Cannam |
---|---|
date | Mon, 27 Oct 2008 20:29:55 +0000 |
parents | c9b055f84326 |
children | a82645e788fc |
line wrap: on
line source
/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*- vi:set ts=8 sts=4 sw=4: */ /* Sonic Visualiser An audio file viewer and annotation editor. Centre for Digital Music, Queen Mary, University of London. This file copyright 2008 QMUL. 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. See the file COPYING included with this distribution for more information. */ #include "CachedFile.h" #include "base/TempDirectory.h" #include "base/ProgressReporter.h" #include "base/Exceptions.h" #include "FileSource.h" #include <QFileInfo> #include <QSettings> #include <QVariant> #include <QMap> #include <QDir> #include <QCryptographicHash> #include <iostream> QString CachedFile::getLocalFilenameFor(QUrl url) { QDir dir(getCacheDirectory()); QString filename = QString::fromLocal8Bit (QCryptographicHash::hash(url.toString().toLocal8Bit(), QCryptographicHash::Sha1).toHex()); return dir.filePath(filename); } QString CachedFile::getCacheDirectory() { QDir dir = TempDirectory::getInstance()->getContainingPath(); QString cacheDirName("cache"); QFileInfo fi(dir.filePath(cacheDirName)); if ((fi.exists() && !fi.isDir()) || (!fi.exists() && !dir.mkdir(cacheDirName))) { throw DirectoryCreationFailed(fi.filePath()); } return fi.filePath(); } CachedFile::CachedFile(QString origin, ProgressReporter *reporter) : m_origin(origin), m_localFilename(getLocalFilenameFor(m_origin)), m_reporter(reporter), m_ok(false) { std::cerr << "CachedFile::CachedFile: origin is \"" << origin.toStdString() << "\"" << std::endl; check(); } CachedFile::CachedFile(QUrl url, ProgressReporter *reporter) : m_origin(url.toString()), m_localFilename(getLocalFilenameFor(m_origin)), m_reporter(reporter), m_ok(false) { std::cerr << "CachedFile::CachedFile: url is \"" << url.toString().toStdString() << "\"" << std::endl; check(); } CachedFile::~CachedFile() { } bool CachedFile::isOK() const { return m_ok; } QString CachedFile::getLocalFilename() const { return m_localFilename; } void CachedFile::check() { //!!! n.b. obvious race condition here if different CachedFile // objects for same url used in more than one thread -- need to // lock appropriately. also consider race condition between // separate instances of the program if (!QFileInfo(m_localFilename).exists()) { std::cerr << "CachedFile::check: Local file does not exist, making a note that it hasn't been retrieved" << std::endl; updateLastRetrieval(false); // empirically! } QDateTime lastRetrieval = getLastRetrieval(); if (lastRetrieval.isValid()) { std::cerr << "CachedFile::check: Valid last retrieval at " << lastRetrieval.toString().toStdString() << std::endl; // this will not be the case if the file is missing, after // updateLastRetrieval(false) was called above m_ok = true; if (lastRetrieval.addDays(2) < QDateTime::currentDateTime()) { //!!! std::cerr << "CachedFile::check: Out of date; trying to retrieve again" << std::endl; // doesn't matter if retrieval fails -- we just don't // update the last retrieval time //!!! but we do want an additional last-attempted // timestamp so as to ensure we aren't retrying the // retrieval every single time if it isn't working if (retrieve()) { std::cerr << "CachedFile::check: Retrieval succeeded" << std::endl; updateLastRetrieval(true); } else { std::cerr << "CachedFile::check: Retrieval failed, will try again later (using existing file for now)" << std::endl; } } } else { std::cerr << "CachedFile::check: No valid last retrieval" << std::endl; // there is no acceptable file if (retrieve()) { std::cerr << "CachedFile::check: Retrieval succeeded" << std::endl; m_ok = true; updateLastRetrieval(true); } else { std::cerr << "CachedFile::check: Retrieval failed, remaining in invalid state" << std::endl; // again, we don't need to do anything here -- the last // retrieval timestamp is already invalid } } } bool CachedFile::retrieve() { //!!! need to work by retrieving the file to another name, and //!!! then "atomically" moving it to its proper place (I'm not //!!! sure we can do an atomic move to replace an existing file //!!! using Qt classes, but a plain delete then copy is probably //!!! good enough) FileSource fs(m_origin, m_reporter); if (!fs.isOK() || !fs.isAvailable()) { std::cerr << "CachedFile::retrieve: ERROR: FileSource reported unavailable or failure" << std::endl; return false; } fs.waitForData(); if (!fs.isOK()) { std::cerr << "CachedFile::retrieve: ERROR: FileSource reported failure during receive" << std::endl; return false; } QString tempName = fs.getLocalFilename(); QFile tempFile(tempName); if (!tempFile.exists()) { std::cerr << "CachedFile::retrieve: ERROR: FileSource reported success, but local temporary file \"" << tempName.toStdString() << "\" does not exist" << std::endl; return false; } QFile previous(m_localFilename); if (previous.exists()) { if (!previous.remove()) { std::cerr << "CachedFile::retrieve: ERROR: Failed to remove previous copy of cached file at \"" << m_localFilename.toStdString() << "\"" << std::endl; return false; } } //!!! This is not ideal, could leave us with nothing (old file //!!! removed, new file not able to be copied in because e.g. no //!!! disk space left) if (!tempFile.copy(m_localFilename)) { std::cerr << "CachedFile::retrieve: ERROR: Failed to copy newly retrieved file from \"" << tempName.toStdString() << "\" to \"" << m_localFilename.toStdString() << "\"" << std::endl; return false; } std::cerr << "CachedFile::retrieve: Successfully copied newly retrieved file \"" << tempName.toStdString() << "\" to its home at \"" << m_localFilename.toStdString() << "\"" << std::endl; return true; } QDateTime CachedFile::getLastRetrieval() { QSettings settings; settings.beginGroup("FileCache"); QString key("last-retrieval-times"); QMap<QString, QVariant> timeMap = settings.value(key).toMap(); QDateTime lastTime = timeMap[m_localFilename].toDateTime(); settings.endGroup(); return lastTime; } void CachedFile::updateLastRetrieval(bool successful) { //!!! note !successful does not mean "we failed to update the //!!! file" (and so it remains the same as before); it means "the //!!! file is not there at all" QSettings settings; settings.beginGroup("FileCache"); QString key("last-retrieval-times"); QMap<QString, QVariant> timeMap = settings.value(key).toMap(); QDateTime dt; if (successful) dt = QDateTime::currentDateTime(); timeMap[m_localFilename] = dt; settings.setValue(key, timeMap); settings.endGroup(); }