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BVolume

Derived from: none
Declared in:  be/storage/Volume.h
Library: libbe.so
Summary:  more...


The BVolume class lets you ask questions about specific "volumes," where a volume is any independent file system. Most applications are usually only interested in "persistent" volumes, such as hard disks, floppies, or CD-ROMs, but you can also create BVolumes to virtual file systems, such as /pipe. Here's what a BVolume knows:

Initializing a BVolume

There are two ways to initialize a BVolume:

Mount and Unmount

A BVolume object can't tell you directly whether the device that it represents is still mounted. If you want to ask, you can call a status_t-returning BVolume function; if the function returns B_BAD_VALUE, the device is no longer mounted.

Furthermore, you can't ask a BVolume to unmount itself. If you want to be told when devices are mounted and unmounted, you have to ask the Node Monitor to help you. Call watch_node() thus:

watch_node(NULL, B_WATCH_MOUNT, messenger);

messenger is a BMessenger object that acts as the target of subsequent mount and unmount notifications. See "The Node Monitor" section of this chapter for details.


Constructor and Destructor


BVolume()

BVolume(void)
BVolume(BVolume &volume)
BVolume(dev_t device)

Creates a new BVolume object and initializes it according to the argument. The status of the initialization is recorded by the InitCheck() function.


~BVolume

~BVolume()

Destroys the BVolume object.


Member Functions


Capacity() , FreeBytes()

off_t Capacity(void) const
off_t FreeBytes(void) const

Returns the volume's total storage capacity and the amount of storage that's currently unused. Both measurements are in bytes.


Device()

dev_t Device(void) const

Returns the object's dev_t number.


GetIcon()

status_t GetIcon(BBitmap *icon, icon_size which) const

Returns the volume's icon in icon. which specifies the icon to retrieve, either B_MINI_ICON (16x16) or B_LARGE_ICON (32x32).

See also: get_device_icon()


GetName()

status_t GetName(char *buffer) const

Copies the name of the volume into buffer.


GetRootDirectory()

status_t GetRootDirectory(BDirectory *dir) const

Initializes dir (which must be allocated) to refer to the volume's "root directory." The root directory stands at the "root" of the volume's file hierarchy. Note that this isn't necessarily the root of the entire file hierarchy.


InitCheck()

status_t InitCheck(void) const

Returns the status of the last initialization (from either the constructor or SetTo()).


IsPersistent() , IsRemovable() , IsReadOnly() , IsShared()

bool IsPersistent(void) const
bool IsRemovable(void) const
bool IsReadOnly(void) const
bool IsShared(void) const

These functions answer media-related questions about the volume:


KnowsAttr() , KnowsMime() , KnowsQuery()

bool KnowsAttr(void) const
bool KnowsMime(void) const
bool KnowsQuery(void) const

These functions answer questions about the file system on the volume:


SetTo() , Unset()

status_t SetTo(dev_t dev)
void Unset(void)

SetTo() initializes the BVolume object to represent the volume (device) identified by the argument.

Unset() uninitializes the BVolume.


Operators


= (assignment)

BVolume& operator = (const BEntry &volume)

In the expression

BVolume a = b;

BVolume a is initialized to refer to the same volume as b. To gauge the success of the assignment, you should call InitCheck() immediately afterwards. Assigning a BVolume to itself is safe.

Assigning from an uninitialized BVolume is "successful": The assigned-to BVolume will also be uninitialized (B_NO_INIT).


== , != (comparison)

bool operator == (const BVolume &volume) const
bool operator != (const BVolume &volume) const

Two BVolume objects are said to be equal if they refer to the same volume, or if they're both uninitialized.


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