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Reading and Writing Files

Reading and Writing Files — Reading from and writing to open file handles.

Synopsis

enum                GnomeVFSSeekPosition;
GnomeVFSResult      gnome_vfs_read                      (GnomeVFSHandle *handle,
                                                         gpointer buffer,
                                                         GnomeVFSFileSize bytes,
                                                         GnomeVFSFileSize *bytes_read);
GnomeVFSResult      gnome_vfs_write                     (GnomeVFSHandle *handle,
                                                         gconstpointer buffer,
                                                         GnomeVFSFileSize bytes,
                                                         GnomeVFSFileSize *bytes_written);
GnomeVFSResult      gnome_vfs_seek                      (GnomeVFSHandle *handle,
                                                         GnomeVFSSeekPosition whence,
                                                         GnomeVFSFileOffset offset);
GnomeVFSResult      gnome_vfs_tell                      (GnomeVFSHandle *handle,
                                                         GnomeVFSFileSize *offset_return);
GnomeVFSResult      gnome_vfs_forget_cache              (GnomeVFSHandle *handle,
                                                         GnomeVFSFileOffset offset,
                                                         GnomeVFSFileSize size);

Description

Reading and writing operations are explained, also gnome_vfs_seek(), which is used to move the file pointer inside the file.

Details

enum GnomeVFSSeekPosition

typedef enum {
        GNOME_VFS_SEEK_START,
        GNOME_VFS_SEEK_CURRENT,
        GNOME_VFS_SEEK_END
} GnomeVFSSeekPosition;

This is used to specify the start position for seek operations.

GNOME_VFS_SEEK_START

Start of the file.

GNOME_VFS_SEEK_CURRENT

Current position.

GNOME_VFS_SEEK_END

End of the file.

gnome_vfs_read ()

GnomeVFSResult      gnome_vfs_read                      (GnomeVFSHandle *handle,
                                                         gpointer buffer,
                                                         GnomeVFSFileSize bytes,
                                                         GnomeVFSFileSize *bytes_read);

Read bytes from handle. As with Unix system calls, the number of bytes read can effectively be less than bytes on return and will be stored in bytes_read.

handle :

handle of the file to read data from.

buffer :

pointer to a buffer that must be at least bytes bytes large.

bytes :

number of bytes to read.

bytes_read :

pointer to a variable that will hold the number of bytes effectively read on return.

Returns :

an integer representing the result of the operation.

gnome_vfs_write ()

GnomeVFSResult      gnome_vfs_write                     (GnomeVFSHandle *handle,
                                                         gconstpointer buffer,
                                                         GnomeVFSFileSize bytes,
                                                         GnomeVFSFileSize *bytes_written);

Write bytes into the file opened through handle. As with Unix system calls, the number of bytes written can effectively be less than bytes on return and will be stored in bytes_written.

handle :

handle of the file to write data to.

buffer :

pointer to the buffer containing the data to be written.

bytes :

number of bytes to write.

bytes_written :

pointer to a variable that will hold the number of bytes effectively written on return.

Returns :

an integer representing the result of the operation.

gnome_vfs_seek ()

GnomeVFSResult      gnome_vfs_seek                      (GnomeVFSHandle *handle,
                                                         GnomeVFSSeekPosition whence,
                                                         GnomeVFSFileOffset offset);

Set the current position for reading/writing through handle.

handle :

handle for which the current position must be changed.

whence :

integer value representing the starting position.

offset :

number of bytes to skip from the position specified by whence. (a positive value means to move forward; a negative one to move backwards).

Returns :

an integer representing the result of the operation.

gnome_vfs_tell ()

GnomeVFSResult      gnome_vfs_tell                      (GnomeVFSHandle *handle,
                                                         GnomeVFSFileSize *offset_return);

Return the current position on handle. This is the point in the file pointed to by handle that reads and writes will occur on.

handle :

handle for which the current position must be retrieved.

offset_return :

pointer to a variable that will contain the current position on return.

Returns :

an integer representing the result of the operation.

gnome_vfs_forget_cache ()

GnomeVFSResult      gnome_vfs_forget_cache              (GnomeVFSHandle *handle,
                                                         GnomeVFSFileOffset offset,
                                                         GnomeVFSFileSize size);

With this call you can announce to gnome-vfs that you will no longer use the region of data starting at offset with the size of size. Any cached data for this region might then be freed.

This might be useful if you stream large files, for example.

handle :

handle of the file to affect.

offset :

start point of the region to be freed.

size :

length of the region to be freed (or until the end of the file if 0 is specified).

Returns :

an integer representing the result of the operation.

Since 2.12

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