|
|
|
GIO Reference Manual | |
|---|---|---|---|---|
| Top | Description | ||||
#include <gio/gio.h>
GResource;
enum GResourceFlags;
enum GResourceLookupFlags;
GResource * g_resource_load (const gchar *filename,
GError **error);
GResource * g_resource_new_from_data (GBytes *data,
GError **error);
GResource * g_resource_ref (GResource *resource);
void g_resource_unref (GResource *resource);
GBytes * g_resource_lookup_data (GResource *resource,
const char *path,
GResourceLookupFlags lookup_flags,
GError **error);
GInputStream * g_resource_open_stream (GResource *resource,
const char *path,
GResourceLookupFlags lookup_flags,
GError **error);
char ** g_resource_enumerate_children (GResource *resource,
const char *path,
GResourceLookupFlags lookup_flags,
GError **error);
gboolean g_resource_get_info (GResource *resource,
const char *path,
GResourceLookupFlags lookup_flags,
gsize *size,
guint32 *flags,
GError **error);
void g_resources_register (GResource *resource);
void g_resources_unregister (GResource *resource);
GBytes * g_resources_lookup_data (const char *path,
GResourceLookupFlags lookup_flags,
GError **error);
GInputStream * g_resources_open_stream (const char *path,
GResourceLookupFlags lookup_flags,
GError **error);
char ** g_resources_enumerate_children (const char *path,
GResourceLookupFlags lookup_flags,
GError **error);
gboolean g_resources_get_info (const char *path,
GResourceLookupFlags lookup_flags,
gsize *size,
guint32 *flags,
GError **error);
#define G_RESOURCE_ERROR
enum GResourceError;
Applications and libraries often contain binary or textual data that is really part of the
application, rather than user data. For instance GtkBuilder .ui files, splashscreen images,
GMenu markup xml, CSS files, icons, etc. These are often shipped as files in $datadir/appname, or
manually included as literal strings in the code.
The GResource API and the glib-compile-resources program provide a convenient and efficient alternative to this which has some nice properties. You maintain the files as normal files, so its easy to edit them, but during the build the files are combined into a binary bundle that is linked into the executable. This means that loading the resource files are efficient (as they are already in memory, shared with other instances) and simple (no need to check for things like I/O errors or locate the files in the filesystem). It also makes it easier to create relocatable applications.
Resource files can also be marked as compressed. Such files will be included in the resource bundle in a compressed form, but will be automatically uncompressed when the resource is used. This is very useful e.g. for larger text files that are parsed once (or rarely) and then thrown away.
Resource files can also be marked to be preprocessed, by setting the value of the
preprocess attribute to a comma-separated list of preprocessing options.
The only options currently supported are:
xml-stripblanks which will use xmllint to strip
ignorable whitespace from the xml file. For this to work, the XMLLINT
environment variable must be set to the full path to the xmllint executable, or xmllint
must be in the PATH; otherwise the preprocessing step is skipped.
to-pixdata which will use gdk-pixbuf-pixdata to convert
images to the GdkPixdata format, which allows you to create pixbufs directly using the data inside
the resource file, rather than an (uncompressed) copy if it. For this, the gdk-pixbuf-pixdata
program must be in the PATH, or the GDK_PIXBUF_PIXDATA environment variable must be
set to the full path to the gdk-pixbuf-pixdata executable; otherwise the resource compiler will
abort.
Resource bundles are created by the glib-compile-resources program which takes an xml file that describes the bundle, and a set of files that the xml references. These are combined into a binary resource bundle.
Example 13. Example resource description
1 2 3 4 5 6 7 8 |
<?xml version="1.0" encoding="UTF-8"?> <gresources> <gresource prefix="/org/gtk/Example"> <file>data/splashscreen.png</file> <file compressed="true">dialog.ui</file> <file preprocess="xml-stripblanks">menumarkup.xml</file> </gresource> </gresources> |
This will create a resource bundle with the following files:
/org/gtk/Example/data/splashscreen.png /org/gtk/Example/dialog.ui /org/gtk/Example/menumarkup.xml
Note that all resources in the process share the same namespace, so use java-style path prefixes (like in the above example) to avoid conflicts.
You can then use glib-compile-resources to compile the xml to a
binary bundle that you can load with g_resource_load(). However, its more common to use the --generate-source and
--generate-header arguments to create a source file and header to link directly into your application.
Once a GResource has been created and registered all the data in it can be accessed globally in the process by
using API calls like g_resources_open_stream() to stream the data or g_resources_lookup_data() to get a direct pointer
to the data. You can also use uris like "resource:///org/gtk/Example/data/splashscreen.png" with GFile to access
the resource data.
There are two forms of the generated source, the default version uses the compiler support for constructor and destructor functions (where available) to automatically create and register the GResource on startup or library load time. If you pass --manual-register two functions to register/unregister the resource is instead created. This requires an explicit initialization call in your application/library, but it works on all platforms, even on the minor ones where this is not available. (Constructor support is available for at least Win32, MacOS and Linux.)
Note that resource data can point directly into the data segment of e.g. a library, so if you are unloading libraries during runtime you need to be very careful with keeping around pointers to data from a resource, as this goes away when the library is unloaded. However, in practice this is not generally a problem, since most resource accesses is for your own resources, and resource data is often used once, during parsing, and then released.
typedef enum {
G_RESOURCE_FLAGS_NONE = 0,
G_RESOURCE_FLAGS_COMPRESSED = (1<<0)
} GResourceFlags;
GResourceFlags give information about a particular file inside a resource bundle.
Since 2.32
typedef enum {
G_RESOURCE_LOOKUP_FLAGS_NONE = 0
} GResourceLookupFlags;
GResourceLookupFlags determine how resource path lookups are handled.
Since 2.32
GResource * g_resource_load (const gchar *filename,GError **error);
Loads a binary resource bundle and creates a GResource representation of it, allowing you to query it for data.
If you want to use this resource in the global resource namespace you need
to register it with g_resources_register().
|
the path of a filename to load, in the GLib filename encoding. [type filename] |
|
return location for a GError, or NULL
|
Returns : |
a new GResource, or NULL on error. [transfer full]
|
Since 2.32
GResource * g_resource_new_from_data (GBytes *data,GError **error);
Creates a GResource from a reference to the binary resource bundle.
This will keep a reference to data while the resource lives, so
the data should not be modified or freed.
If you want to use this resource in the global resource namespace you need
to register it with g_resources_register().
|
A GBytes |
|
return location for a GError, or NULL
|
Returns : |
a new GResource, or NULL on error. [transfer full]
|
Since 2.32
GResource * g_resource_ref (GResource *resource);
Atomically increments the reference count of array by one. This
function is MT-safe and may be called from any thread.
Since 2.32
void g_resource_unref (GResource *resource);
Atomically decrements the reference count of resource by one. If the
reference count drops to 0, all memory allocated by the array is
released. This function is MT-safe and may be called from any
thread.
|
A GResource |
Since 2.32
GBytes * g_resource_lookup_data (GResource *resource,const char *path,GResourceLookupFlags lookup_flags,GError **error);
Looks for a file at the specified path in the resource and
returns a GBytes that lets you directly access the data in
memory.
The data is always followed by a zero byte, so you can safely use the data as a C string. However, that byte is not included in the size of the GBytes.
For uncompressed resource files this is a pointer directly into the resource bundle, which is typically in some readonly data section in the program binary. For compressed files we allocate memory on the heap and automatically uncompress the data.
lookup_flags controls the behaviour of the lookup.
|
A GResource |
|
A pathname inside the resource |
|
A GResourceLookupFlags |
|
return location for a GError, or NULL
|
Returns : |
GBytes or NULL on error.
Free the returned object with g_bytes_unref(). [transfer full]
|
Since 2.32
GInputStream * g_resource_open_stream (GResource *resource,const char *path,GResourceLookupFlags lookup_flags,GError **error);
Looks for a file at the specified path in the resource and
returns a GInputStream that lets you read the data.
lookup_flags controls the behaviour of the lookup.
|
A GResource |
|
A pathname inside the resource |
|
A GResourceLookupFlags |
|
return location for a GError, or NULL
|
Returns : |
GInputStream or NULL on error.
Free the returned object with g_object_unref(). [transfer full]
|
Since 2.32
char ** g_resource_enumerate_children (GResource *resource,const char *path,GResourceLookupFlags lookup_flags,GError **error);
Returns all the names of children at the specified path in the resource.
The return result is a NULL terminated list of strings which should
be released with g_strfreev().
lookup_flags controls the behaviour of the lookup.
|
A GResource |
|
A pathname inside the resource |
|
A GResourceLookupFlags |
|
return location for a GError, or NULL
|
Returns : |
an array of constant strings. [array zero-terminated=1][transfer full] |
Since 2.32
gboolean g_resource_get_info (GResource *resource,const char *path,GResourceLookupFlags lookup_flags,gsize *size,guint32 *flags,GError **error);
Looks for a file at the specified path in the resource and
if found returns information about it.
lookup_flags controls the behaviour of the lookup.
|
A GResource |
|
A pathname inside the resource |
|
A GResourceLookupFlags |
|
a location to place the length of the contents of the file,
or NULL if the length is not needed. [out][allow-none]
|
|
a location to place the flags about the file,
or NULL if the length is not needed. [out][allow-none]
|
|
return location for a GError, or NULL
|
Returns : |
TRUE if the file was found. FALSE if there were errors |
Since 2.32
void g_resources_register (GResource *resource);
Registers the resource with the process-global set of resources.
Once a resource is registered the files in it can be accessed
with the global resource lookup functions like g_resources_lookup_data().
|
A GResource |
Since 2.32
void g_resources_unregister (GResource *resource);
Unregisters the resource from the process-global set of resources.
|
A GResource |
Since 2.32
GBytes * g_resources_lookup_data (const char *path,GResourceLookupFlags lookup_flags,GError **error);
Looks for a file at the specified path in the set of
globally registred resources and returns a GBytes that
lets you directly access the data in memory.
The data is always followed by a zero byte, so you can safely use the data as a C string. However, that byte is not included in the size of the GBytes.
For uncompressed resource files this is a pointer directly into the resource bundle, which is typically in some readonly data section in the program binary. For compressed files we allocate memory on the heap and automatically uncompress the data.
lookup_flags controls the behaviour of the lookup.
|
A pathname inside the resource |
|
A GResourceLookupFlags |
|
return location for a GError, or NULL
|
Returns : |
GBytes or NULL on error.
Free the returned object with g_bytes_unref(). [transfer full]
|
Since 2.32
GInputStream * g_resources_open_stream (const char *path,GResourceLookupFlags lookup_flags,GError **error);
Looks for a file at the specified path in the set of
globally registred resources and returns a GInputStream
that lets you read the data.
lookup_flags controls the behaviour of the lookup.
|
A pathname inside the resource |
|
A GResourceLookupFlags |
|
return location for a GError, or NULL
|
Returns : |
GInputStream or NULL on error.
Free the returned object with g_object_unref(). [transfer full]
|
Since 2.32
char ** g_resources_enumerate_children (const char *path,GResourceLookupFlags lookup_flags,GError **error);
Returns all the names of children at the specified path in the set of
globally registred resources.
The return result is a NULL terminated list of strings which should
be released with g_strfreev().
lookup_flags controls the behaviour of the lookup.
|
A pathname inside the resource |
|
A GResourceLookupFlags |
|
return location for a GError, or NULL
|
Returns : |
an array of constant strings. [array zero-terminated=1][transfer full] |
Since 2.32
gboolean g_resources_get_info (const char *path,GResourceLookupFlags lookup_flags,gsize *size,guint32 *flags,GError **error);
Looks for a file at the specified path in the set of
globally registred resources and if found returns information about it.
lookup_flags controls the behaviour of the lookup.
|
A pathname inside the resource |
|
A GResourceLookupFlags |
|
a location to place the length of the contents of the file,
or NULL if the length is not needed. [out][allow-none]
|
|
a location to place the flags about the file,
or NULL if the length is not needed. [out][allow-none]
|
|
return location for a GError, or NULL
|
Returns : |
TRUE if the file was found. FALSE if there were errors |
Since 2.32
#define G_RESOURCE_ERROR (g_resource_error_quark ())
Error domain for GResource. Errors in this domain will be from the GResourceError enumeration. See GError for more information on error domains.
typedef enum {
G_RESOURCE_ERROR_NOT_FOUND,
G_RESOURCE_ERROR_INTERNAL
} GResourceError;
An error code used with G_RESOURCE_ERROR in a GError returned
from a GResource routine.
| no file was found at the requested path | |
| unknown error |
Since 2.32