path: root/mkspecs/unsupported/macx-iosdevice-clang
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authorIgor Kushnir <>2021-11-13 14:21:40 +0200
committerIgor Kushnir <>2021-12-06 22:55:06 +0200
commitd797e3c88ed7be6e2b683984950334a8054728a9 (patch)
tree952034e2a5021b8767d250cd89697312ba9b440d /mkspecs/unsupported/macx-iosdevice-clang
parent6d6fb7846c664b3b15ae03542658f6beae96e0b2 (diff)
Optimize QMimeDatabase::mimeTypeForFile(f, MatchDefault)HEADdev
Open the file only if matching on content is needed. Use QFileInfo::filePath() instead of QFileInfo::absoluteFilePath() in QMimeDatabase::mimeTypeForFile(). filePath() does much less work, and so is faster. Thiago Macieira helpfully explained in a review comment why the absolute path is not useful for correctness here: "Nothing needs absolute paths within the same application that would resolve the relative path to absolute. You only need an absolute path if you're communicating with another application that may be in a different directory." QMimeDatabase::mimeTypeForFile() checks fileInfo.isDir(), so the fileName.endsWith(QLatin1Char('/')) check in QMimeDatabasePrivate::mimeTypeForFileNameAndData() was redundant when called from this function. The other two callers of that function now check this condition before opening IO devices. This improves performance of the two QMimeDatabase::mimeTypeForFileNameAndData() overloads in the corner case. Refactor and optimize QMimeDatabasePrivate::findByFileName() and its usages. Previously each caller constructed a QFileInfo object and passed QFileInfo::fileName() into this function. Now the callers simply pass an absolute or relative path to a file into this function, which then uses QFileSystemEntry::fileName() to exclude the path. Constructing QFileInfo is relatively expensive, so this change slightly improves performance. Optimize QMimeDatabasePrivate::loadProviders() by calling static QFileInfo::exists() instead of constructing a QFileInfo object and calling the non-static QFileInfo::exists() overload. Note that the QFileInfo object was always created, even if QFileInfo::exists() under an `if` and an `#if` was never called. The following table contains the average results of the added benchmark tst_QMimeDatabase::benchMimeTypeForFile() on my GNU/Linux system before and at this commit. The numbers denote milliseconds per iteration. data row tag before at MatchDefault: archive 0.029 0.016 OpenDocument Text 0.029 0.015 existent archive with extension 0.039 0.025 existent C with extension 0.033 0.020 existent text file with extension 0.033 0.020 existent C w/o extension 0.076 0.074 existent patch w/o extension 0.11 0.105 existent archive w/o extension 0.069 0.066 MatchExtension: archive 0.012 0.0115 OpenDocument Text 0.0115 0.011 existent archive with extension 0.017 0.016 existent C with extension 0.011 0.011 existent text file with extension 0.011 0.011 existent C w/o extension 0.016 0.0155 existent patch w/o extension 0.013 0.012 existent archive w/o extension 0.013 0.012 MatchContent: archive 0.019 0.012 OpenDocument Text 0.019 0.012 existent archive with extension 0.053 0.051 existent C with extension 0.056 0.0545 existent text file with extension 0.058 0.056 existent C w/o extension 0.0605 0.059 existent patch w/o extension 0.10 0.099 existent archive w/o extension 0.057 0.054 Change-Id: Idb541656e073a2c4822ace3f4da412f29f2351f8 Reviewed-by: Thiago Macieira <> Reviewed-by: David Faure <>
Diffstat (limited to 'mkspecs/unsupported/macx-iosdevice-clang')
0 files changed, 0 insertions, 0 deletions