How to Get the Names of All Mounted Macintosh Disk Volumes (69211)

MORE INFORMATION

The Macintosh File Manager keeps information about mounted disk volumes in a volume-control-block queue; each entry consists of a volume control block. A volume control block is a 178-byte nonrelocatable block that contains volume-specific information. For a description of the structure of a volume control block, see page 176 of "Inside Macintosh," Volume 4, by Apple Computer Inc. (published by Addison-Wesley).

The location of the default volume control block is &H352. The first entry in each block is a pointer to the next entry. If this value is a zero, the end of the queue has been reached. The volume name is located at bytes 44 to 70 (27 bytes long) from the head of the block.

The following is a code example:

'Program to demonstrate the use of the Volume Control Block
'       to get the names of all mounted volumes

DIM VolName$(10)        'Array to hold the names
VolCount% = 0           'Counter to hold total number of volumes
ptr& = &H352            'Pointer to default Volume Control Block
vol& = PEEKL(ptr&)      'Get pointer to next entry in queue
WHILE vol& <> 0 'Loop until null pointer
        vol& = PEEKL(ptr&)
        ptr& = vol&
        IF vol& <> 0 THEN
                VolCount% = VolCount% + 1
                x$ = ""
                st = PEEK(vol& + 44)
                FOR i = 1 TO st 'Skip i = 0 (Length of String)
                        x$=x$ + CHR$(PEEK(vol& + 44 + i))
                NEXT i
                VolName$(VolCount%) = x$
                PRINT "[";VolName$(VolCount%);"]"
                INPUT a  ' pause program using input statement
        END IF
WEND