!
!	NAME:  XTRANS
!
!	FUNCTION:  This is the transmit module for the XMODEM protocol
!	support on the AlphaMicro.  XRECV provides the receive support.
!	First, the receiver sends a NAK sequence to tell the sender to 
!	begin transmission.  Then the sender starts sending blocks.  Each
!	block consists of 1) SOH; 2) block number; 3) complemented block
!	number; 4) 128 data bytes; and 5) a one-byte checksum.  The
!	receiver responds with an ACK or a NAK depending on whether or
!	not the block was successfully received.  If not, it is resent.
!	If so, the next block is sent.  When the entire file has been
!	sent, the sender sends an EOT to which the receiver responds with
!	an ACK.  This program may be interrupted by hitting CTL-C three
!	times in a row.
!
!	AUTHOR:  Tom Dahlquist
!
!	EDIT HISTORY:
!	  When   Who What
!	01/17/85 TAD Written (from MTRANS).
!	01/24/85 TAD Allow either three DEL's or CTL-C's to kill us.
!
!	This map is for the entire contents of one XMODEM transmission.
!	First is the SOH, then the block #, then the inverted block #,
!	then 128 data bytes, and finally the checksum.
!
	MAP1 WHOLE'BLOCK,X
		MAP2 SOH,X,1,CHR$(1)
		MAP2 BLOCK'NUMBER,B,1,1
		MAP2 NOT'BLOCK'NUMBER,B,1
		MAP2 IO'BLOCK,X,128
		MAP2 CHECK'SUM'BYTE,X,1


	MAP1 BLOCK'LENGTH,F,,128
	MAP1 IN'CHR,X,1
	MAP1 TEST'CHR,X,1
	MAP1 OUT'CHR,X,1
	MAP1 DISK'FSPEC,S,25
	MAP1 OUT'UNIT,F,,0
	MAP1 CHECK'SUM,F
	MAP1 CTRLC,X,1,CHR$(3)
	MAP1 DEL,X,1,CHR$(255)
	MAP1 EOT,X,1,CHR$(4)
	MAP1 ACK,X,1,CHR$(6)
	MAP1 BELL,X,1,CHR$(7)
	MAP1 NAK,X,1,CHR$(21)
	MAP1 ESCAPE,X,1,CHR$(27)
	MAP1 I,F
	MAP1 COUNT'BLOCKS,F
	MAP1 GOT'NAK,F
	MAP1 DEBUG,F
	MAP1 TRUE,F,,-1
	MAP1 FALSE,F,,0
	MAP1 TIMER,F
	MAP1 CHOICE,F
	MAP1 AREA,X,616			! for FILEIN
	MAP1 LENGTH,F			! from FILEIN and TIMEIN
	MAP1 TIMEOUT,F

GET'FILENAME:
	INPUT LINE "Name of file to be transmitted:  ",DISK'FSPEC
	DISK'FSPEC=UCS(DISK'FSPEC)
	IF DISK'FSPEC[-2,-1]="/D" THEN &
		DISK'FSPEC=DISK'FSPEC[1,-3] : &
		OPEN #99,"XTRANS.LST",OUTPUT : &
		DEBUG=TRUE
	I=INSTR(1,DISK'FSPEC,".")
	IF I=0 THEN DISK'FSPEC=DISK'FSPEC+".DAT"
	LOOKUP DISK'FSPEC,I
	IF I=0 THEN &
		CALL TRY'AGAIN : &
		GOTO GET'FILENAME
	XCALL IMG
	XCALL FILEIN,1,AREA,DISK'FSPEC
!	OPEN #OUT'UNIT, "TRM:", OUTPUT
!	
!	We first wait for a NAK from the receiver.  Then we send
!	each block as SOH, block #, inverse block #, 128 data bytes, and
!	a one byte checksum.  Then we wait for an ACK; if we get a NAK,
!	we retransmit the block.  After the last block (of each fork) we
!	send an EOT and wait for an ACK.  That's all folks!
!
START:
	CALL GET'ONE
	IF TIMEOUT GOTO TIMEOUT
	IF IN'CHR=CTRLC THEN &
		CALL CTRLC'ABORT : &
		GOTO START
	IF IN'CHR=DEL THEN &
		CALL DEL'ABORT : &
		GOTO START
	IF IN'CHR#NAK GOTO START
	BLOCK'NUMBER=1
LOOP:
	XCALL FILEIN,2,AREA,IO'BLOCK,LENGTH
	IF LENGTH=0 GOTO EOF
RETRY'BLOCK:
	CALL SEND'BLOCK
	IF GOT'NAK OR TIMEOUT GOTO RETRY'BLOCK
	BLOCK'NUMBER = BLOCK'NUMBER+1
	GOTO LOOP

EOF:
	CALL SEND'EOT	
	XCALL FILEIN,3,AREA
	END

SEND'BLOCK:

	NOT'BLOCK'NUMBER=NOT BLOCK'NUMBER

!	CHECK'SUM = 0
!	FOR I = 1 TO 131
!	CHECK'SUM = CHECK'SUM+ASC(WHOLE'BLOCK[I;1])
!	NEXT
!	CHECK'SUM'BYTE=CHR$(CHECK'SUM AND 255)
	XCALL CMPCRC,IO'BLOCK,CHECK'SUM'BYTE

	IF DEBUG THEN &
		?#99,"-";STR(ASC(SOH)) : &
		?#99,"-";STR(BLOCK'NUMBER) : &
		?#99,"-";STR(NOT'BLOCK'NUMBER) : &
		?#99,"DATA BLOCK" : &
		?#99,"-";STR(ASC(CHECK'SUM'BYTE))
	PRINT #OUT'UNIT,WHOLE'BLOCK;
	CALL WAIT'ACK
	RETURN

WAIT'ACK:
	GOT'NAK=FALSE
	CALL GET'ONE
	IF TIMEOUT RETURN
	IF IN'CHR = CTRLC THEN &
		CALL CTRLC'ABORT : &
		GOTO WAIT'ACK
	IF IN'CHR=DEL THEN &
		CALL DEL'ABORT : &
		GOTO WAIT'ACK
	IF IN'CHR = NAK THEN &
		GOT'NAK=TRUE : &
		RETURN
	IF IN'CHR <> ACK GOTO WAIT'ACK
	RETURN
	
SEND'EOT:
	OUT'CHR=EOT
	CALL SEND'ONE
	CALL WAIT'ACK
	IF GOT'NAK GOTO SEND'EOT
	IF TIMEOUT GOTO TIMEOUT
	RETURN

GET'ONE:
	TIMEOUT=FALSE
	XCALL TIMEIN,60,IN'CHR,LENGTH
	IF DEBUG AND LENGTH#0 THEN &
		?#99,STR(ASC(IN'CHR))
	IF LENGTH=0 THEN TIMEOUT=TRUE
	RETURN

SEND'ONE:
	?#OUT'UNIT,OUT'CHR;
	IF DEBUG THEN &
		?#99,"-";STR(ASC(OUT'CHR))
	RETURN

DEL'ABORT:
	TEST'CHR=DEL
	GOTO TEST'ABORT
CTRLC'ABORT:
	TEST'CHR=CTRLC
TEST'ABORT:
	FOR I=1 TO 2
	XCALL TIMEIN,2,IN'CHR,LENGTH
	IF LENGTH=0 OR IN'CHR#TEST'CHR RETURN
	NEXT
	?"Ending due to operator interrupt!"
	IF DEBUG THEN &
		?#99,"Ended due to CTL-C"
	END

TIMEOUT:
	?"Sorry, your Mac isn't talking to me--ending."
	IF DEBUG THEN &
		?#99,"Timed out."
	END

BAD'FILE:
	END

!===================================================================
TRY'AGAIN:
		? "That file --- "DISK'FSPEC " --- could not be found. "
		?
		? "Would you like to: "
		? "                   1 -- Try Again! "
		? "                   2 -- Return to the Menu."
		INPUT " (enter the number of your choice ---  > ", CHOICE
		IF CHOICE=1 RETURN
		IF CHOICE#2 GOTO TRY'AGAIN
		END