/****************************************************************************
   
    OS/A65 Version 2.0.0
    Multitasking Operating System for 6502 Computers

    Copyright (C) 1989-1998 Andre Fachat 

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

****************************************************************************/

/*
 * exports checksum3, printpacket2, ECout, ETxtout, EHexout, EClfout
 *
 * Must be at the end of the code, because of #iflused constructs
 */

	.(
	.bss
tmp	.byt 0,0,0
len	.word 0
	.zero
&p	.word 0
	.text

	/* computes IP header checksum and returns it in a/x */
	/* packet length in a/y, x = zeropage address of pkt address pointer */
&checksum3 .(

	sec
	sbc #1
	sta len
	tya
	sbc #0
	sta len+1
	bcs uf
	rts
uf
	lda 0,x
	sta p
	lda 1,x
	sta p+1

#if 0 /* def DEBUGPKT */
DB("Check: ")
lda p+1:jsr EHexout: lda p: jsr EHexout:lda #" ": jsr ECout
lda len+1:jsr EHexout: lda len: jsr EHexout
#endif
	lda #0
	sta tmp
	sta tmp+1
	sta tmp+2
	ldy #0
loop	
	iny
	lda tmp
	clc
	adc (p),y
	sta tmp
	lda tmp+1
	dey
	adc (p),y
	sta tmp+1
	bcc l0
	inc tmp+2
l0
	iny
	iny
	bne l1
	inc p+1
l1	
	lda len
	sec
	sbc #2
	sta len
	bcs l1a
	lda len+1
	sbc #0
	sta len+1
	bcc loope	; underflow (even size) -> end
l1a	lda len		
	ora len+1
	bne loop

l1b	lda (p),y
	clc
	adc tmp+1
	sta tmp+1
	bcc loope
	inc tmp+2
loope
	lda tmp
	clc
	adc tmp+2
	pha
	lda tmp+1
	adc #0
	eor #$ff
	tax
	pla
	eor #$ff
#if 0 /* def DEBUGPKT */
	php
	pha
	DB(" -> ")
	txa
	jsr EHexout
	pla
	pha
	jsr EHexout
	jsr ECrlfout
	pla
	plp
#endif
	bne err
	cpx #0
	bne err
	clc
	rts
err	sec
	rts
	.)


#iflused printpacket2

&printpacket2 .(
	sta len
	sty len+1
	cmp #64
	bcs limit
	tya
	beq nolimit
limit	lda #48
	sta len
	lda #0
	sta len+1
nolimit
	lda 0,x
	sta p
	lda 1,x
	sta p+1

	ldy #0
l0
	lda (p),y
	jsr EHexout
	lda #" "
	jsr ECout
	iny
	cpy len
	beq lend
	tya
	and #7
	bne l0
	jsr ECrlfout
	jmp l0
lend
	DB("^m^jHeader Checksum=")
	lda #0
	sta tmp+1
	ldy #IPH_VER
	lda (p),y
	and #$0f
	asl
	asl
	sta tmp
	lda tmp
	ldy tmp+1
	ldx #p
	jsr checksum3
	pha
	txa
	jsr EHexout
	pla
	jsr EHexout

	jsr ECrlfout
	clc
	rts
	.)
#endif
	.)

/**********************************************************************/
/* Output on STDERR			 			      */

	.(
	.bss
XR	.byt 0
	.text

#iflused ECout
&ECout	.(
	stx XR
	ldx #STDERR
	sec
	jsr fputc
	ldx XR
	rts
	.)
#endif

#iflused ECrlfout
&ECrlfout .(
	stx XR
	ldx #STDERR
	lda #13
	sec
	jsr fputc
	lda #10
	sec
	jsr fputc
	ldx XR
	rts
	.)
#endif

#iflused EHexout
&EHexout  .(
	  stx XR
          pha
          lsr
          lsr
          lsr
          lsr
          jsr nibout
          pla
          and #$0f
nibout    ldx #STDERR
	  clc
          adc #"0"
          cmp #"9"+1
          bcc nibok
          adc #6
nibok     sec
	  jsr fputc
	  ldx XR
	  rts
          .)
#endif

#iflused ETxtout
&ETxtout
	  .(
	.zero
tp        .word
	.text

          sta tp
          sty tp+1
	  stx XR
	  ldx #STDERR
          ldy #0
tol       lda (tp),y
          beq tole
	  sec
          jsr fputc
          iny
          bne tol
          inc tp+1
          bne tol
tole
	  ldx XR
          clc
          rts
          .)
#endif
	.)