class QResource¶

The QResource class provides an interface for reading directly from resources. More…

Synopsis¶

Methods¶

def __init__()
def absoluteFilePath()
def children()
def compressionAlgorithm()
def data()
def fileName()
def isDir()
def isFile()
def isValid()
def lastModified()
def locale()
def setFileName()
def setLocale()
def size()
def uncompressedData()
def uncompressedSize()

Note

This documentation may contain snippets that were automatically translated from C++ to Python. We always welcome contributions to the snippet translation. If you see an issue with the translation, you can also let us know by creating a ticket on https:/bugreports.qt.io/projects/PYSIDE

Detailed Description¶

QResource is an object that represents a set of data (and possibly children) relating to a single resource entity. QResource gives direct access to the bytes in their raw format. In this way direct access allows reading data without buffer copying or indirection. Indirection is often useful when interacting with the resource entity as if it is a file, this can be achieved with QFile . The data and children behind a QResource are normally compiled into an application/library, but it is also possible to load a resource at runtime. When loaded at run time the resource file will be loaded as one big set of data and then given out in pieces via references into the resource tree.

A QResource can either be loaded with an absolute path, either treated as a file system rooted with a / character, or in resource notation rooted with a : character. A relative resource can also be opened which will be found in the list of paths returned by searchPaths() .

A QResource that is representing a file will have data backing it, this data can possibly be compressed, in which case qUncompress() must be used to access the real data; this happens implicitly when accessed through a QFile . A QResource that is representing a directory will have only children and no data.

Dynamic Resource Loading¶

A resource can be left out of an application’s binary and loaded when it is needed at run-time by using the registerResource() function. The resource file passed into registerResource() must be a binary resource as created by rcc. Further information about binary resources can be found in The Qt Resource System documentation.

This can often be useful when loading a large set of application icons that may change based on a setting, or that can be edited by a user and later recreated. The resource is immediately loaded into memory, either as a result of a single file read operation, or as a memory mapped file.

This approach can prove to be a significant performance gain as only a single file will be loaded, and pieces of data will be given out via the path requested in setFileName() .

The unregisterResource() function removes a reference to a particular file. If there are QResource objects that currently reference resources related to the unregistered file, they will continue to be valid but the resource file itself will be removed from the resource roots, and thus no further QResource can be created pointing into this resource data. The resource itself will be unmapped from memory when the last QResource that points to it is destroyed.

Corruption and Security¶

The QResource class performs some checks on the file passed to determine whether it is supported by the current version of Qt. Those tests are only to check the file header does not request features (such as Zstandard decompression) that have not been compiled in or that the file is not of a future version of Qt. They do not confirm the validity of the entire file.

QResource should not be used on files whose provenance cannot be trusted. Applications should be designed to attempt to load only resource files whose provenance is at least as trustworthy as that of the application itself or its plugins.

See also

The Qt Resource System QFile QDir QFileInfo

class Compression¶

This enum is used by compressionAlgorithm() to indicate which algorithm the RCC tool used to compress the payload.

Constant

Description

QResource.NoCompression

Contents are not compressed

QResource.ZlibCompression

Contents are compressed using zlib and can be decompressed using the qUncompress() function.

QResource.ZstdCompression

Contents are compressed using zstd. To decompress, use the ZSTD_decompress function from the zstd library.

See also

compressionAlgorithm()

Constant	Description
QResource.NoCompression	Contents are not compressed
QResource.ZlibCompression	Contents are compressed using zlib and can be decompressed using the `qUncompress()` function.
QResource.ZstdCompression	Contents are compressed using zstd. To decompress, use the `ZSTD_decompress` function from the zstd library.

__init__([file=""[, locale=QLocale()]])¶

Parameters:

file – str
locale – QLocale

Constructs a QResource pointing to file. locale is used to load a specific localization of a resource data.

See also

QFileInfo searchPaths() setFileName() setLocale()

absoluteFilePath()¶

Return type:: str

Returns the real path that this QResource represents, if the resource was found via the searchPaths() it will be indicated in the path.

See also

fileName()

children()¶

Return type:: list of strings

Returns a list of all resources in this directory, if the resource represents a file the list will be empty.

See also

isDir()

compressionAlgorithm()¶

Return type:: Compression

Returns the compression type that this resource is compressed with, if any. If it is not compressed, this function returns NoCompression .

If this function returns ZlibCompression , you may decompress the data using the qUncompress() function. Up until Qt 5.13, this was the only possible compression algorithm.

If this function returns ZstdCompression , you need to use the Zstandard library functions (<zstd.h> header). Qt does not provide a wrapper.

See Zstandard manual .

See also

data() isFile()

data()¶

Return type:: PyObject

Returns a read only buffer object pointing to the segment of data that this resource represents. If the resource is compressed the data returns is compressed and qUncompress() must be used to access the data. If the resource is a directory None is returned.

fileName()¶

Return type:: str

Returns the full path to the file that this QResource represents as it was passed.

See also

setFileName() absoluteFilePath()

isDir()¶

Return type:: bool

Returns true if the resource represents a directory and thus may have children() in it, false if it represents a file.

See also

isFile()

isFile()¶

Return type:: bool

Returns true if the resource represents a file and thus has data backing it, false if it represents a directory.

See also

isDir()

isValid()¶

Return type:: bool

Returns true if the resource really exists in the resource hierarchy, false otherwise.

lastModified()¶

Return type:: QDateTime

Returns the date and time when the file was last modified before packaging into a resource.

locale()¶

Return type:: QLocale

Returns the locale used to locate the data for the QResource .

See also

setLocale()

static registerResource(rccFilename[, resourceRoot=""])¶

Parameters:

rccFilename – str
resourceRoot – str

Return type:

bool

Registers the resource with the given rccFileName at the location in the resource tree specified by mapRoot, and returns true if the file is successfully opened; otherwise returns false.

See also

unregisterResource()

static registerResourceData(rccData[, resourceRoot=""])¶

Parameters:

rccData – str
resourceRoot – str

Return type:

bool

setFileName(file)¶

Parameters:: file – str

Sets a QResource to point to file. file can either be absolute, in which case it is opened directly, if relative then the file will be tried to be found in searchPaths() .

See also

fileName() absoluteFilePath()

setLocale(locale)¶

Parameters:: locale – QLocale

Sets a QResource to only load the localization of resource to for locale. If a resource for the specific locale is not found then the C locale is used.

See also

locale() setFileName()

size()¶

Return type:: int

Returns the size of the stored data backing the resource.

If the resource is compressed, this function returns the size of the compressed data. See uncompressedSize() for the uncompressed size.

See also

data() uncompressedSize() isFile()

uncompressedData()¶

Return type:: QByteArray

Returns the resource data, decompressing it first, if the data was stored compressed. If the resource is a directory or an error occurs while decompressing, a null QByteArray is returned.

Note

If the data was compressed, this function will decompress every time it is called. The result is not cached between calls.