MirageFileFilter

MirageFileFilter — File filter object.

Synopsis

#include <mirage-file-filter.h>

struct              MirageFileFilter;
struct              MirageFileFilterClass;
struct              MirageFileFilterInfo;
gboolean            mirage_file_filter_can_handle_data_format
                                                        (MirageFileFilter *self,
                                                         GError **error);
void                mirage_file_filter_generate_info    (MirageFileFilter *self,
                                                         const gchar *id,
                                                         const gchar *name,
                                                         gint num_types,
                                                         ...);
const MirageFileFilterInfo * mirage_file_filter_get_info
                                                        (MirageFileFilter *self);
goffset             mirage_file_filter_get_position     (MirageFileFilter *self);
void                mirage_file_filter_info_copy        (const MirageFileFilterInfo *info,
                                                         MirageFileFilterInfo *dest);
void                mirage_file_filter_info_free        (MirageFileFilterInfo *info);
void                mirage_file_filter_set_file_size    (MirageFileFilter *self,
                                                         gsize size);

Object Hierarchy

  GObject
   +----GInputStream
         +----GFilterInputStream
               +----MirageFileFilter

Implemented Interfaces

MirageFileFilter implements GSeekable and MirageContextual.

Description

MirageFileFilter is a basic unit of file access abstraction used in libMirage. It inherits from GFilterInputStream and implements GSeekable interface.

When opening a file with libMirage, mirage_context_create_file_stream() function should be used. It creates a chain of MirageFileFilter objects on top of a GFileInputStream, and returns the top object on the chain. This allows transparent access to, for example, compressed data stored in the file.

There are two ways to implement a MirageFileFilter. For full control over the logic for reading from parts and managing position in the stream, use "full interface", which requires implementation of three virtual functions: read, seek and tell. The second option is to use "simplified interface", which provides framework for stream position management and reading logic, and requires that file filter implements partial_read function. Additionally, it requires that file filter implementation sets the file stream size using mirage_file_filter_set_file_size() function. In partial_read, the current position in the stream, which is managed by the framework, can be obtained using mirage_file_filter_get_position().

Details

struct MirageFileFilter

struct MirageFileFilter;

All the fields in the MirageFileFilter structure are private to the MirageFileFilter implementation and should never be accessed directly.


struct MirageFileFilterClass

struct MirageFileFilterClass {
    GFilterInputStreamClass parent_class;

    /* Class members */
    gboolean (*can_handle_data_format) (MirageFileFilter *self, GError **error);


    /* Functions reimplemented from GInputStream: */
    gssize (*read) (MirageFileFilter *self, void *buffer, gsize count, GError **error);

    /* Functions reimplemented from GSeekable: */
    goffset (*tell) (MirageFileFilter *self);
    gboolean (*seek) (MirageFileFilter *self, goffset offset, GSeekType type, GError **error);

    /* Simplified interface */
    gssize (*partial_read) (MirageFileFilter *self, void *buffer, gsize count);
};

The class structure for the MirageFileFilter type.

GFilterInputStreamClass parent_class;

the parent class

can_handle_data_format ()

checks whether file filter can handle data stored in underyling stream

read ()

reads data from stream

tell ()

tells the current location within stream

seek ()

seeks to a location within stream

partial_read ()

reads a chunk of requested data from stream

struct MirageFileFilterInfo

struct MirageFileFilterInfo {
    gchar *id;
    gchar *name;
    gchar **description;
    gchar **mime_type;
};

A structure containing file filter information. It can be obtained with call to mirage_file_filter_get_info().

gchar *id;

file filter ID

gchar *name;

file filter name

gchar **description;

zero-terminated array of file type description strings. [array zero-terminated=1]

gchar **mime_type;

zero-terminated array of file type MIME strings. [array zero-terminated=1]

mirage_file_filter_can_handle_data_format ()

gboolean            mirage_file_filter_can_handle_data_format
                                                        (MirageFileFilter *self,
                                                         GError **error);

Checks whether file filter can handle data stored in underyling stream.

self :

a MirageFileFilter

error :

location to store error, or NULL. [out][allow-none]

Returns :

TRUE if file filter can handle data in underlying stream, FALSE if not

mirage_file_filter_generate_info ()

void                mirage_file_filter_generate_info    (MirageFileFilter *self,
                                                         const gchar *id,
                                                         const gchar *name,
                                                         gint num_types,
                                                         ...);

Generates file filter information from the input fields. It is intended as a function for creating file filter information in file filter implementations.

self :

a MirageFileFilter

id :

file filter ID. [in]

name :

file filter name. [in]

num_types :

number of MIME types. [in]

... :

description and MIME type string pairs, one for each defined type. [in]

mirage_file_filter_get_info ()

const MirageFileFilterInfo * mirage_file_filter_get_info
                                                        (MirageFileFilter *self);

Retrieves file filter information.

self :

a MirageFileFilter

Returns :

a pointer to file filter information structure. The structure belongs to object and therefore should not be modified. [transfer none]

mirage_file_filter_get_position ()

goffset             mirage_file_filter_get_position     (MirageFileFilter *self);

Retrieves position in the stream.

This function is intented for use in file filter implementations that are based on the simplified interface. It should be used by the implementation's partial_read function to determine position to read from without having to worry about position management and update.

self :

a MirageFileFilter

Returns :

position in the stream

mirage_file_filter_info_copy ()

void                mirage_file_filter_info_copy        (const MirageFileFilterInfo *info,
                                                         MirageFileFilterInfo *dest);

Copies parser information from info to dest.

info :

a MirageFileFilterInfo to copy data from. [in]

dest :

a MirageFileFilterInfo to copy data to. [in]

mirage_file_filter_info_free ()

void                mirage_file_filter_info_free        (MirageFileFilterInfo *info);

Frees the allocated fields in info (but not the structure itself!).

info :

a MirageFileFilterInfo to free. [in]

mirage_file_filter_set_file_size ()

void                mirage_file_filter_set_file_size    (MirageFileFilter *self,
                                                         gsize size);

Sets size of the stream.

This function is intented for use in file filter implementations that are based on the simplified interface. It should be used by the implementation to set the stream size during stream parsing; the set stream size is then used by the read function that is implemented by the simplified interface.

self :

a MirageFileFilter

size :

size of the stream. [in]

See Also

MirageContext