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