GResource

## GResource GResource — Resource framework |

## Synopsis

    #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;

## Description

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

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    <?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.

## Details

### GResource

    typedef struct _GResource GResource;

A resource bundle.

Since 2.32

### enum GResourceFlags

    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.

`G_RESOURCE_FLAGS_NONE` | No flags set.
`G_RESOURCE_FLAGS_COMPRESSED` | The file is compressed.

Since 2.32

### enum GResourceLookupFlags

    typedef enum {
      G_RESOURCE_LOOKUP_FLAGS_NONE       = 0
    } GResourceLookupFlags;

GResourceLookupFlags determine how resource path lookups are handled.

`G_RESOURCE_LOOKUP_FLAGS_NONE` | No flags set.

Since 2.32

### g_resource_load ()

    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()`.

`filename` : | the path of a filename to load, in the GLib filename encoding. [type filename]
`error` : | return location for a GError, or `NULL`
Returns : | a new GResource, or `NULL` on error. [transfer full]

Since 2.32

### g_resource_new_from_data ()

    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()`.

`data` : | A GBytes
`error` : | return location for a GError, or `NULL`
Returns : | a new GResource, or `NULL` on error. [transfer full]

Since 2.32

### g_resource_ref ()

    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.

`resource` : | A GResource
Returns : | The passed in GResource

Since 2.32

### g_resource_unref ()

    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.

`resource` : | A GResource

Since 2.32

### g_resource_lookup_data ()

    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.

`resource` : | A GResource
`path` : | A pathname inside the resource
`lookup_flags` : | A GResourceLookupFlags
`error` : | 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

### g_resource_open_stream ()

    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.

`resource` : | A GResource
`path` : | A pathname inside the resource
`lookup_flags` : | A GResourceLookupFlags
`error` : | 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

### g_resource_enumerate_children ()

    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.

`resource` : | A GResource
`path` : | A pathname inside the resource
`lookup_flags` : | A GResourceLookupFlags
`error` : | return location for a GError, or `NULL`
Returns : | an array of constant strings. [array zero-terminated=1][transfer full]

Since 2.32

### g_resource_get_info ()

    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.

`resource` : | A GResource
`path` : | A pathname inside the resource
`lookup_flags` : | A GResourceLookupFlags
`size` : | a location to place the length of the contents of the file, or `NULL` if the length is not needed. [out][allow-none]
`flags` : | a location to place the flags about the file, or `NULL` if the length is not needed. [out][allow-none]
`error` : | return location for a GError, or `NULL`
Returns : | `TRUE` if the file was found. `FALSE` if there were errors

Since 2.32

### g_resources_register ()

    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()`.

`resource` : | A GResource

Since 2.32

### g_resources_unregister ()

    void                g_resources_unregister              (GResource *resource);

Unregisters the resource from the process-global set of resources.

`resource` : | A GResource

Since 2.32

### g_resources_lookup_data ()

    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.

`path` : | A pathname inside the resource
`lookup_flags` : | A GResourceLookupFlags
`error` : | 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

### g_resources_open_stream ()

    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.

`path` : | A pathname inside the resource
`lookup_flags` : | A GResourceLookupFlags
`error` : | 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

### g_resources_enumerate_children ()

    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.

`path` : | A pathname inside the resource
`lookup_flags` : | A GResourceLookupFlags
`error` : | return location for a GError, or `NULL`
Returns : | an array of constant strings. [array zero-terminated=1][transfer full]

Since 2.32

### g_resources_get_info ()

    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.

`path` : | A pathname inside the resource
`lookup_flags` : | A GResourceLookupFlags
`size` : | a location to place the length of the contents of the file, or `NULL` if the length is not needed. [out][allow-none]
`flags` : | a location to place the flags about the file, or `NULL` if the length is not needed. [out][allow-none]
`error` : | return location for a GError, or `NULL`
Returns : | `TRUE` if the file was found. `FALSE` if there were errors

Since 2.32

### G_RESOURCE_ERROR

    #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.

### enum GResourceError

    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.

`G_RESOURCE_ERROR_NOT_FOUND` | no file was found at the requested path
`G_RESOURCE_ERROR_INTERNAL` | unknown error

Since 2.32