QMimeDatabase Class Reference

\inmodule QtCore More...

#include <qmimedatabase.h>

Collaboration diagram for QMimeDatabase:

Public Types
enum	MatchMode { MatchDefault = 0x0 , MatchExtension = 0x1 , MatchContent = 0x2 }
	This enum specifies how matching a file to a MIME type is performed. More...

Public Member Functions
	QMimeDatabase ()
	Constructs a QMimeDatabase object.
	~QMimeDatabase ()
	Destroys the QMimeDatabase object.
QMimeType	mimeTypeForName (const QString &nameOrAlias) const
	Returns a MIME type for nameOrAlias or an invalid one if none found.
QMimeType	mimeTypeForFile (const QString &fileName, MatchMode mode=MatchDefault) const
	Returns a MIME type for the file named fileName using mode.
QMimeType	mimeTypeForFile (const QFileInfo &fileInfo, MatchMode mode=MatchDefault) const
	Returns a MIME type for fileInfo.
QList< QMimeType >	mimeTypesForFileName (const QString &fileName) const
	Returns the MIME types for the file name fileName.
QMimeType	mimeTypeForData (const QByteArray &data) const
	Returns a MIME type for data.
QMimeType	mimeTypeForData (QIODevice *device) const
	Returns a MIME type for the data in device.
QMimeType	mimeTypeForUrl (const QUrl &url) const
	Returns a MIME type for url.
QMimeType	mimeTypeForFileNameAndData (const QString &fileName, QIODevice *device) const
	Returns a MIME type for the given fileName and device data.
QMimeType	mimeTypeForFileNameAndData (const QString &fileName, const QByteArray &data) const
	Returns a MIME type for the given fileName and device data.
QString	suffixForFileName (const QString &fileName) const
	Returns the suffix for the file fileName, as known by the MIME database.
QList< QMimeType >	allMimeTypes () const
	Returns the list of all available MIME types.

Detailed Description

\inmodule QtCore

The QMimeDatabase class maintains a database of MIME types.

Since

5.0

The MIME type database is provided by the freedesktop.org shared-mime-info project. If the MIME type database cannot be found on the system, as is the case on most Windows, \macos, and iOS systems, Qt will use its own copy of it.

Applications which want to define custom MIME types need to install an XML file into the locations searched for MIME definitions. These locations can be queried with

QStandardPaths::locateAll(QStandardPaths::GenericDataLocation, "mime/packages"_L1,
                          QStandardPaths::LocateDirectory);

On a typical Unix system, this will be /usr/share/mime/packages/, but it is also possible to extend the list of directories by setting the environment variable XDG_DATA_DIRS. For instance adding /opt/myapp/share to XDG_DATA_DIRS will result in /opt/myapp/share/mime/packages/ being searched for MIME definitions.

Here is an example of MIME XML:

<?xml version="1.0" encoding="UTF-8"?>
<mime-info xmlns="http://www.freedesktop.org/standards/shared-mime-info">
  <mime-type type="application/vnd.qt.qmakeprofile">
    <comment xml:lang="en">Qt qmake Profile</comment>
    <glob pattern="*.pro" weight="50"/>
  </mime-type>
</mime-info>

For more details about the syntax of XML MIME definitions, including defining "magic" in order to detect MIME types based on data as well, read the Shared Mime Info specification at http://standards.freedesktop.org/shared-mime-info-spec/shared-mime-info-spec-latest.html

On Unix systems, a binary cache is used for more performance. This cache is generated by the command "update-mime-database path", where path would be /opt/myapp/share/mime in the above example. Make sure to run this command when installing the MIME type definition file.

\threadsafe

QMimeDatabase db;
QMimeType mime = db.mimeTypeForFile(fileName);
if (mime.inherits("text/plain")) {
    // The file is plain text, we can display it in a QTextEdit
}

See also

QMimeType, {MIME Type Browser Example}

Definition at line 22 of file qmimedatabase.h.

Member Enumeration Documentation

MatchMode

enum QMimeDatabase::MatchMode

This enum specifies how matching a file to a MIME type is performed.

\value MatchDefault Both the file name and content are used to look for a match

\value MatchExtension Only the file name is used to look for a match

\value MatchContent The file content is used to look for a match

Enumerator
MatchDefault
MatchExtension
MatchContent

Definition at line 32 of file qmimedatabase.h.

Constructor & Destructor Documentation

QMimeDatabase()

QMimeDatabase::QMimeDatabase

(

)

Constructs a QMimeDatabase object.

It is perfectly OK to create an instance of QMimeDatabase every time you need to perform a lookup. The parsing of mimetypes is done on demand (when shared-mime-info is installed) or when the very first instance is constructed (when parsing XML files directly).

Definition at line 575 of file qmimedatabase.cpp.

~QMimeDatabase()

QMimeDatabase::~QMimeDatabase

(

)

Destroys the QMimeDatabase object.

Definition at line 584 of file qmimedatabase.cpp.

Member Function Documentation

allMimeTypes()

QList< QMimeType > QMimeDatabase::allMimeTypes

(

)

const

Returns the list of all available MIME types.

This can be useful for showing all MIME types to the user, for instance in a MIME type editor. Do not use unless really necessary in other cases though, prefer using the \l {mimeTypeForData()}{mimeTypeForXxx()} methods for performance reasons.

Definition at line 808 of file qmimedatabase.cpp.

References QMimeDatabasePrivate::allMimeTypes(), and QMimeDatabasePrivate::mutex.

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mimeTypeForData() [1/2]

QMimeType QMimeDatabase::mimeTypeForData

(

const QByteArray &

data

)

const

Returns a MIME type for data.

A valid MIME type is always returned. If data doesn't match any known MIME type data, the default MIME type (application/octet-stream) is returned.

Definition at line 695 of file qmimedatabase.cpp.

References QMimeDatabasePrivate::findByData(), and QMimeDatabasePrivate::mutex.

Referenced by QWasmAudioOutput::setSource(), QWasmVideoOutput::setSource(), and AVFAudioDecoder::setSourceDevice().

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mimeTypeForData() [2/2]

QMimeType QMimeDatabase::mimeTypeForData

(

QIODevice *

device

)

const

Returns a MIME type for the data in device.

A valid MIME type is always returned. If the data in device doesn't match any known MIME type data, the default MIME type (application/octet-stream) is returned.

Definition at line 710 of file qmimedatabase.cpp.

References device, QMimeDatabasePrivate::mimeTypeForData(), and QMimeDatabasePrivate::mutex.

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mimeTypeForFile() [1/2]

QMimeType QMimeDatabase::mimeTypeForFile	(	const QFileInfo &	fileInfo,
		MatchMode	mode = MatchDefault
	)		const

Returns a MIME type for fileInfo.

A valid MIME type is always returned.

The default matching algorithm looks at both the file name and the file contents, if necessary. The file extension has priority over the contents, but the contents will be used if the file extension is unknown, or matches multiple MIME types. If fileInfo is a Unix symbolic link, the file that it refers to will be used instead. If the file doesn't match any known pattern or data, the default MIME type (application/octet-stream) is returned.

When mode is set to MatchExtension, only the file name is used, not the file contents. The file doesn't even have to exist. If the file name doesn't match any known pattern, the default MIME type (application/octet-stream) is returned. If multiple MIME types match this file, the first one (alphabetically) is returned.

When mode is set to MatchContent, and the file is readable, only the file contents are used to determine the MIME type. This is equivalent to calling mimeTypeForData with a QFile as input device.

fileInfo may refer to an absolute or relative path.

See also

QMimeType::isDefault(), mimeTypeForData()

Definition at line 628 of file qmimedatabase.cpp.

References QFileInfo::filePath(), QMimeDatabasePrivate::mimeTypeForFile(), and QMimeDatabasePrivate::mutex.

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mimeTypeForFile() [2/2]

QMimeType QMimeDatabase::mimeTypeForFile	(	const QString &	fileName,
		MatchMode	mode = MatchDefault
	)		const

Returns a MIME type for the file named fileName using mode.

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Definition at line 640 of file qmimedatabase.cpp.

References fileName, MatchExtension, QMimeDatabasePrivate::mimeTypeForFile(), QMimeDatabasePrivate::mimeTypeForFileExtension(), and QMimeDatabasePrivate::mutex.

Referenced by QIcon::addFile(), fileType(), mimeTypeForUrl(), and QWasmAudioOutput::setSource().

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mimeTypeForFileNameAndData() [1/2]

QMimeType QMimeDatabase::mimeTypeForFileNameAndData	(	const QString &	fileName,
		const QByteArray &	data
	)		const

Returns a MIME type for the given fileName and device data.

This overload can be useful when the file is remote, and we started to download some of its data. This allows to do full MIME type matching for remote files as well.

A valid MIME type is always returned. If data doesn't match any known MIME type data, the default MIME type (application/octet-stream) is returned.

This method looks at both the file name and the file contents, if necessary. The file extension has priority over the contents, but the contents will be used if the file extension is unknown, or matches multiple MIME types.

Definition at line 789 of file qmimedatabase.cpp.

References directoryMimeType(), fileName, QMimeDatabasePrivate::mimeTypeForFileNameAndData(), QMimeDatabasePrivate::mimeTypeForName(), QMimeDatabasePrivate::mutex, and QIODeviceBase::ReadOnly.

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mimeTypeForFileNameAndData() [2/2]

QMimeType QMimeDatabase::mimeTypeForFileNameAndData	(	const QString &	fileName,
		QIODevice *	device
	)		const

Returns a MIME type for the given fileName and device data.

This overload can be useful when the file is remote, and we started to download some of its data in a device. This allows to do full MIME type matching for remote files as well.

If the device is not open, it will be opened by this function, and closed after the MIME type detection is completed.

A valid MIME type is always returned. If device data doesn't match any known MIME type data, the default MIME type (application/octet-stream) is returned.

This method looks at both the file name and the file contents, if necessary. The file extension has priority over the contents, but the contents will be used if the file extension is unknown, or matches multiple MIME types.

Definition at line 762 of file qmimedatabase.cpp.

References device, directoryMimeType(), fileName, QMimeDatabasePrivate::mimeTypeForFileNameAndData(), QMimeDatabasePrivate::mimeTypeForName(), and QMimeDatabasePrivate::mutex.

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mimeTypeForName()

QMimeType QMimeDatabase::mimeTypeForName

(

const QString &

nameOrAlias

)

const

Returns a MIME type for nameOrAlias or an invalid one if none found.

Definition at line 593 of file qmimedatabase.cpp.

References QMimeDatabasePrivate::mimeTypeForName(), and QMimeDatabasePrivate::mutex.

Referenced by QMediaFormat::mimeType(), and mimeTypeForUrl().

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mimeTypeForUrl()

QMimeType QMimeDatabase::mimeTypeForUrl

(

const QUrl &

url

)

const

Returns a MIME type for url.

If the URL is a local file, this calls mimeTypeForFile.

Otherwise the matching is done based on the file name only, except for schemes where file names don't mean much, like HTTP. This method always returns the default mimetype for HTTP URLs, use QNetworkAccessManager to handle HTTP URLs properly.

A valid MIME type is always returned. If url doesn't match any known MIME type data, the default MIME type (application/octet-stream) is returned.

Definition at line 731 of file qmimedatabase.cpp.

References QMimeDatabasePrivate::defaultMimeType(), QUrl::isLocalFile(), MatchExtension, mimeTypeForFile(), mimeTypeForName(), QUrl::path(), QUrl::scheme(), QString::startsWith(), QUrl::toLocalFile(), and url.

Referenced by QAndroidPlatformServices::openUrl(), and QHaikuServices::openUrl().

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mimeTypesForFileName()

QList< QMimeType > QMimeDatabase::mimeTypesForFileName

(

const QString &

fileName

)

const

Returns the MIME types for the file name fileName.

If the file name doesn't match any known pattern, an empty list is returned. If multiple MIME types match this file, they are all returned.

This function does not try to open the file. To also use the content when determining the MIME type, use mimeTypeForFile() or mimeTypeForFileNameAndData() instead.

See also

mimeTypeForFile()

Definition at line 664 of file qmimedatabase.cpp.

References QList< T >::append(), fileName, matches(), mime, QMimeDatabasePrivate::mimeTypeForFileName(), QMimeDatabasePrivate::mimeTypeForName(), QMimeDatabasePrivate::mutex, and QList< T >::reserve().

Referenced by AndroidContentFileEngine::open().

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suffixForFileName()

QString QMimeDatabase::suffixForFileName

(

const QString &

fileName

)

const

Returns the suffix for the file fileName, as known by the MIME database.

This allows to pre-select "tar.bz2" for foo.tar.bz2, but still only "txt" for my.file.with.dots.txt.

Definition at line 681 of file qmimedatabase.cpp.

References fileName, QMimeDatabasePrivate::findByFileName(), QMimeGlobMatchResult::m_knownSuffixLength, and QMimeDatabasePrivate::mutex.

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---

The documentation for this class was generated from the following files:

• qtbase/src/corelib/mimetypes/qmimedatabase.h
• qtbase/src/corelib/mimetypes/qmimedatabase.cpp