GS/OS ProDOS 8
Purpose:

To tell GS/OS to begin deferring all disk write operations that involve updating
volume bit map and directory blocks.
There is no equivalent ProDOS 8 command.
Parameter table:

GS/OS Input
or

bet Symbolic Name Result
+0to +1 pcount I

Descriptions of parameters:

Description

Number of parameters (0)

pcount The number of parameters in the GS/OS parameter table. The min-
imum value is 0; the maximum is 0.

Common error codes:
[none]

Comments:

Write-deferral sessions are useful where your application wants to transfer a group of
files from one disk to another as quickly as possible. If you don't use a write-deferral
session, copying operations slow down because the disk read/write head must sweep
across the disk medium to access volume bit map and directory blocks before and after
each file transfer. (These blocks are usually physically located far from the file's data
blocks.) By preventing these time-consuming head movements, you will maximize
performance.

At the end of the copying operation, use the EndSession command to write to disk the
blocks that were cached during the session. You must always balance every BeginSes-
sion call with an EndSession call.

92 GS/OS and ProDOS 8 Commands

BindInt
$2031

GS/OS ProDOS 8
Purpose:

To assign a GS/OS interrupt-handling subroutine to a particular interrupt source.
Under ProDOS 8, use the ALLOC - INTERRUPT command instead.
Parameter table:

GS/OS Input
or

C))Cset Symbolic Name Result
+0 to + 1 pcount I
+2 to +3 int~num R
+4 to +5 vrn I
+6to +9 intcode I

Descriptions of parameters:

Description

Number of parameters (3)
Interrupt reference number
Vector reference number
Pointer to interrupt handler

pcount The number of parameters in the GS/OS parameter table. The min-
imum value is 3; the maximum is 3.

int - num The reference number GS/OS assigns to the interrupt-handling sub-

routine. Use this number when you remove the subroutine with the
UnbindInt command.

vrn A reference number that identifies the type of system interrupt the
interrupt handler is to be assigned to:
$0008 AppleTalk (SCC)
$0009 Serial ports (SCC)
$000A Scan-line retrace
$000B Ensoniq waveform completion
$000C Vertical blanking signal (VBL)
$000D Mouse (movement or button)
$000E 1/4-second timer
$000F Keyboard

$0010 ADB response byte ready
$0011 ADB service request (SRQ)
$0012 Desk accessory request keystroke
$0013 Flush keyboard buffer request keystroke
$0014 Keyboard micro abort
$0015 1-second timer

Command Descriptions 93

$0016 Video Graphics Controller (external)
$0017 Other interrupt source

(SCC is the Serial Communications Controller; ADB is the Apple
Desktop Bus.)

If the interrupt emanates from a source that does not have a specific
vrn, set vrn = $0017.

int - code A pointer to the beginning of the interrupt-handling subroutine. See

Chapter 8 for a discussion of rules and conventions GS/OS interrupt-
handling subroutines must follow.

Important: Install an interrupt-handling subroutine before enabling interrupts on the
hardware device. If you don't, the system will crash if an interrupt occurs before
you've had a chance to install the handler.
Common error codes:

$25 The interrupt vector table is full. Solution: Remove one of the active
interrupt-handling subroutines (using UnbindInt) and try again.
Other possible error codes are $04, $07, $53.
Comments:

See chapter 6 for a discussion of how to handle interrupts in a GS/OS environment.

94 GS/OS and ProDOS 8 Commands

ChangePath
$2004

GS/OS ProDOS 8
Purpose:

To rename a file or a disk volume or to move a file from one directory to another on
the same disk volume. You can change the path of any closed file whose rename--
enabled access code bit is set to 1.

Under ProDOS 8, use the RENAME command to rename a file or disk volume. There
is no command for moving a file between two directories.

Parameter table:

GS/OS Input
or

C))Cset Symbolic Name Result
+0to +1 pcount I
+2to +5 pathname I
+6to +9 newpathname I

Descriptions of parameters:

Description

Number of parameters (2)
Pointer to the pathname string
Pointer to the new pathname string

pcount The number of parameters in the GS/OS parameter table. The min-
imum value is 2; the maximum is 2.

pathname A pointer to a class 1 GS/OS string describing the current pathname
of the file whose path is to be changed. If the pathname specified is
not preceded by a separator (/or:), the operating system appends the
name to the default prefix (the 0/ prefix) to create a full pathname.

newpathname A pointer to a class 1 GS/OS string describing the new pathname of
the file whose path is to be changed. If the pathname specified is not
preceded by a separator (/or :), the operating system appends the
name to the default prefix (the 0/ prefix) to create a full pathname.

Common error codes:

$2B The disk is write-protected.

$40 The pathname contains invalid characters, or a full pathname was not
specified (and no default prefix has been set up). Verify that the
filenames and directory names specified in the pathname adhere to
the naming rules described in Chapter 2 and, if a partial pathname
was specified, that a default prefix has been set up.

Command Descriptions 95

$44 A directory in the pathname was not found. Solution: Double-check
the spelling of the pathname, insert the disk containing the correct
directory, or change the default prefix.

$45 The volume directory was not found.
$46 The file was not found.

$47 The new pathname specified already exists. Solution: Give the file a
new pathname not used by any other file on the disk volume.

$4E The file cannot be accessed. Solution: Set the rename-enabled bit of
the file's access code to 1 using SetFileInfo.

$50 The file is open. ChangePath works with closed files only.
$5B The two pathnames indicate different volumes. You can use Change-
Path only for moving files within a single volume.

Other possible error codes are $07, $27, $4A, $4B, $52, $57, $58.
Programming example:

Suppose you want to move a file called MY.ACCESSORY from a subdirectory called
ASM: on the boot disk to the desk accessory directory on the boot disk. Here is the
code you would use:

_ChangePath CP_Parms
RTS

CP_Parms ANOP
DC I2'2' ;The number of parameters
DC I4'Curr_Name'
DC I4'New_Name'

Curr_Name GSString '*:ASM:MY.ACCESSORY'
New_Name GSString '*:SYSTEM:DESK.ACCS:MY.ACCESSORY'

Note that when ChangePath moves a file from one subdirectory to another on the
same disk, it moves only the file's subdirectory entry. The file's data stays put since
the new subdirectory entry for the file still points to it. When the two paths specified
describe files in the same subdirectory, ChangePath is equivalent to the ProDOS 8
RENAME command.

Note also that there are restrictions to keep in mind when moving a subdirectory into
another subdirectory. The subdirectory you're moving cannot be part of the pathname
for the target subdirectory.

96 GS/OS and ProDOS 8 Commands