Editing SmartBox OS (section)

== Starting Up ==

The setup procedure for setting up extension job calls is to:

# Claim the number of JobCodes you want
#:		if success:
# patch the internal_vec and unknownjob_vec vectors
# move LOMEM up to protect your program
# do anything else for initial startup you may want to do
# return back, ready and waiting

This in code looks like:

 <nowiki>execute
	LDX #no_of_calls	; Number of JobCodes wanted
	LDA #1			; CALLOS, function 1, Claim JobCodes
	JSR OS_CALLOS		; Call CALLOS
	CPX #0			; Check we were given some codes
	BEQ noinstall		; No, don't bother installing ourself
	STX call		; Store base address of JobCodes allocated
	STY job_id		; Store JOB ID given

	LDA internal_vec	; Get old internal_vec (LSB)
	STA ovec		; Store it
	LDA internal_vec+1	; Get old internal_vec (MSB)
	STA ovec+1		; Store it
	LDA #>internal_handle	; Our internal handler (LSB)
	STA internal_vec 	; Place it in the vector (LSB)
	LDA #<internal_handle	; Our internal handler (MSB)
	STA internal_vec+1	; Place it in the vector (MSB)

	LDA unknownjob_vec	; Get old unknownjob_vec (LSB)
	STA ovec2 		; Store it
	LDA unknownjob_vec+1	; Get old unknownjob_vec (MSB)
	STA ovec2+1		; Store it
	LDA #>job_handle	; Our unknown job handler (LSB)
	STA unknownjob_vec	; Place it in the vector (LSB)
	LDA #<job_handle	; Our unknown job handler (MSB)
	STA unknownjob_vec+1	; Place it in the vector (MSB)

	LDX #>WriteLomem	; Point to JobName
	LDY #<WriteLomem
	JSR findjob		; Find WriteLomem code
	BEQ noinstall		; Doesn't exist !
	LDX #>end_of_code	; End of code (LSB)
	LDY #<end_of_code	; End of code (MSB)
	STX jobin_buf		; Place it in jobin_buf (LSB)
	STY jobin_buf+1		; Place it in jobin_buf+1 (MSB)
	JSR OS_DECODEJOB	; Call JobCall handler

noinstall
	RTS			; End - return to OS

findjob
	STX zero.gp1		; Zero page
	STY zero.gp1+
	LDY #0
findthisjoblo
	LDA (zero.gp1),Y
	STA jobin.buf,Y		; Store name in jobin_buf
	INY
	CMP #13
	BNE findthisjoblo
	LDA #3			; NameCode
	JSR OS.DECODEJOB	; Call NameCode
	LDA jobout.buf		; Get returned value
	RTS

WriteLomem	STR "WriteLomem"</nowiki>

This will setup the various vectors and memory pointers for the
applicaion, the actual routines (internal_handle and job_handle) are fairly
straight forward and simple:

 <nowiki>internal_handle
	CMP #1			: Is it function call 1 (NameCode) ?
	BNE internal_handle_2	; No, check for function 2
	LDA job_id		; Get our JOB ID number
	STA zero_gp3		; Place it in zero_gp3 for CALLOS
	LDX #>job_names		; Our Job name table (LSB)
	LDY #<job_names		; Our Job name table (MSB)
	LDA #2			; CALLOS function 2
	JSR OS_CALLOS		; Call CALLOS
	BCC internal_yes	: Found, go off and claim call
	LDA #1			; Not found, restore A
	JMP (ovec)		; Call back to old vector

internal_handle_2
	CMP #2			; Is it function call 2 (CodeName) ?
	BNE internal_handle_3	; No, unknown, pass on
	LDA job_id		; Get our JOB ID
	STA zero_gp3		; Place it in zero_gp3 for CALLOS
	LDX #>job_names		; Our Job name table (LSB)
	LDY #<job_names		; Our Job name table (MSB)
	LDA #3			; CALLOS function 3
	JSR OS_CALLOS		; Call CALLOS
	BCC internal_yes	; Found, go off and claim call
	LDA #2			; Not found, restore A
	JMP (ovec)		; Call back to old vector

internal_yes
	LDA #0			; We want to claim call for some reason

internal_handle_3
	JMP (ovec)		; Call back to old vector

job_handle
	PHA			; Mark sure to preserve A
	CPY call		; Check call wanted against base of ours
	BCC job_handle_no	; Less than our base, so definately not ours
	TYA
	SBC #no_of_calls	; Subtract number of calls we have
	CMP call		; Now compare with base
	BCC job_handle2		; Yes, one of ours

job_handle.no
	PLA			; Restore A
	JMP (ovec2)		; Call back to old vector

job_handle2
	TYA
	SEC
	SBC call		; Subtract our base from call
	ASL A			; Times by 2 for offset into table
	TAY			; Place in Y
	LDA job_run_table,Y	; Get LSB of routine
	STA zero_gp1		; Store it for indirect jump (LSB)
	LDA job_run_table+1,Y	; Get MSB of routine
	STA zero_gp1+1		; Store it for indirect jump (MSB)
	PLA			; Restore A
	JMP (zero_gp1)		; Call our relevant routine

job_names			; List of our JobNames
	STR "TestJob"		; Test job name
	DFB &FF			; &FF - marks end of table

job_run_table			; List of routine addresses to match Jobs
	DFW job_TestJob		; Test job routine</nowiki>