A4.S

; ========================================================================
; Name:	      Artem Golovin
; Email:      agolo124@mtroyal.ca
; Course:     COMP2655-001
; Due Date:   November 5th
; Assignment: 4
; Instructor: ppospisil
; Source:     A4.S
; Purpose:    To gain experience with branching and to implement
;	      "snaking" column representation for sorted data
; Details:    Linux "ls" command, by default displays output in columns
;	      whose format is snaking columns. The information is listed
;	      alphabetically in columns instead of rows. If the number of
;	      items is not evenly divisible by the number of columns,
;	      extra items are distributed in the columns from left to right
;	      
;	      Algorithm works this way:
;		- Calculate longest string in the file
;		- Read the file n times, where n is number of rows (incl. extra row)
;	      	- Read word from the file
;		- Skip first words if reading file not for the first time
;		- Print the word
;		- After new line is reached, skip words in file:
;		  - If there's an extra row:
;			- Skip rows - 1 words for m columns that contain extra row
;			- Skip rows - 2 words for the rest of the columns
;		  - Else: Skip rows - 1 words
;		- Calculate # of whitespaces
;			- Column Width - current string size
;		
; Assumptions & Limitations:
;	      It is assumed that provided files are already sorted
;	      alphabetically
;
; Register Table:
; register	usage
; ==========================================================
;    d0 	Mainly used to store character that was read
;		from file and to output a charcter to screen 
;    d1		Used to store current file size. Represents
;		EOF when reached 0		
;    d2
;    d3
;    d4
;    d5
;    d6
;    d7
;
;
;
;=========================================================================
	xref	FileOpen
	xref	FileCharRead
	xref	FileReset
	xref	FileClose
	xref	ScrnCharWrite
	xref	Exit


CR	equ	13
LF	equ	10
NULL	equ	0

WIDTH	equ	80
SPACE	equ	32

start:
	clr.l	d3
	jsr	FileOpen
	tst	d0
	bne	invalidFile
	tst	d1
	beq	emptyFile

initFileRead:
	jsr	FileCharRead
	sub.w	#1,d1
	tst.w	d1
	beq	doneInitRead
	cmp.b	#CR,d0
	beq	initFileRead	; get back to read LF
	cmp.b	#LF,d0
	beq	countWords	; count words if CRLF reached
	add.w	#1,d3
	bra	initFileRead

countWords:
	add.w	#1,d2
	cmp.w	d3,d4
	blt	longestWord
	clr.l	d3
	bra	initFileRead	; continue reading

longestWord:
	move.w	d3,d4
	clr.l	d3
	bra	initFileRead

doneInitRead:
	nop
	move.l	d4,d3
	clr.l	d4
	add.w	#1,d2		; add missing word to total word couter
	tst.w	d2		; check if file is not empty
	beq	emptyFile

calculate:
	clr.l	d0
	add.w	#1,d3		; column width
	swap	d2
	move.w	d3,d2		; words / col width
	clr.l	d3

	move.w	#WIDTH,d7
	divu.w	d2,d7
	move.w	d7,d3		; num of cols
	tst	d3
	beq	singleCol
	bne	continueCalc

singleCol:
	move.w	#1,d3
	bra	continueCalc

continueCalc:	
	clr.l	d7
	swap	d2
	move.w	d2,d7
	divu.w	d3,d7		; get rows and extra rows
	move.l	d7,d4		
	swap	d3
	move.w	d4,d3		; store rows with cols
	clr.w	d4
	swap	d4
	tst.w	d4
	bne	addExtraRow
	beq	startOutput

addExtraRow:
	addq.w	#1,d3
	bra	startOutput

startOutput:
	clr.l	d7
	swap	d4
	move.w	d3,d4

mainLoop:
	cmp.w	d3,d5		; currentRow(d5) < rows(d3.w) 
	bgt	doneProgram
	jsr	FileOpen
	sub.w	#1,d4
	swap	d4
				; skip over #currentRow files
	clr.l	d6
	clr.l	d0		; wordCounter
	tst	d5
	beq	readFileLoop
	
skipWordsOuterLoop:
	cmp.w	d5,d7
	bge	readFileLoop
skipWordsInnerLoop:
	jsr	FileCharRead
	sub.w	#1,d1
	cmp.b	#CR,d0
	beq	skipWordsInnerLoop
	cmp	#LF,d0
	beq	endSkipWordsOuterLoop
	bra	skipWordsInnerLoop
endSkipWordsOuterLoop:
	add.w	#1,d7			; currentRow++
	bra	skipWordsOuterLoop	

readFileLoop:
	clr.l	d6
	move.w	d4,d6
	swap	d6
showWord:
	jsr	FileCharRead
	sub.w	#1,d1		
	cmp.b	#CR,d0
	beq	skipCRLF
	jsr	ScrnCharWrite
	add.w	#1,d6
	bra	showWord

skipCRLF:
	jsr	FileCharRead
	sub.w	#1,d1
	cmp.b	#LF,d0
	beq	traverseFile
	
traverseFile:
	nop
	swap	d6
	clr.l	d0

	;move.w	d3,d0
	;sub.w	#1,d0
	;tst	d6
	;bne	continueTraverse
	;cmp.w	d5,d0
	;beq	endMainLoop

continueTraverse:
	tst.w	d4
	beq	skip1word		
	cmpi.w	#0,d6
	ble	skip2words
	bra	skip1word

skip2words:
	clr.w	d7
	clr.w	d0
	move.w	d3,d0
	sub.w	#2,d0
skip2wordsOuter:	
	cmp.w	d0,d7
	bge	showSpaces
skip2wordsInner:
	jsr	FileCharRead
	sub.w	#1,d1
	cmp.b	#CR,d0
	beq	skip2wordsInner
	cmp	#LF,d0
	beq	skip2wordsDone
	bra	skip2wordsInner
skip2wordsDone:
	move.w	d3,d0
	sub.w	#2,d0
	add.w	#1,d7
	bra	skip2wordsOuter

skip1word:
	clr.w	d7
	clr.w	d0
	move.w	d3,d0
	sub.w	#1,d0
skip1wordOuter:
	cmp.w	d0,d7
	bge	showSpaces
skip1wordInner:
	jsr	FileCharRead
	sub.w	#1,d1
	cmp.b	#CR,d0
	beq	skip1wordInner
	cmp	#LF,d0
	beq	skip1wordDone
	bra	skip1wordInner
skip1wordDone:
	move.w	d3,d0
	sub.w	#1,d0
	add.w	#1,d7
	bra	skip1wordOuter

showSpaces:
	swap	d2
	clr.w	d7
	move.w	d2,d7
	swap	d2
	swap	d6
	sub.w	d6,d7		; # of spaces to show
	swap	d6
	sub.w	#1,d6
spacesLoop:
	tst.w	d7
	beq	readNextWord
	move.w	#SPACE,d0
	jsr	ScrnCharWrite
	sub.w	#1,d7
	bra	spacesLoop

readNextWord:
	clr.l	d0
	move.w	d3,d0

	swap	d4
	tst.w	d4
	beq	doneProgram
	swap	d4
;	tst.w	d6
;	bne	contReadNextWord
;	cmp.w	d5,d0	
;	beq	endMainLoop

	swap	d6
	clr.w	d6	
contReadNextWord:
	cmp.w	#0,d1
	ble	endMainLoop
	bne	showWord

endMainLoop:
	clr.l	d1
	add.w	#1,d5
	move.b	#CR,d0
	jsr	ScrnCharWrite
	move.b	#LF,d0
	jsr	ScrnCharWrite
	swap	d6
	move.w	d4,d6
	swap	d6
	swap	d4
	jsr	FileClose
	bra	mainLoop

emptyFile:
	clr.l	d0
	move.l	#emptyFileMsg,a0
	bra	showErrorMessage
	
invalidFile:
	clr.l	d0
	move.l	#invalidFileMsg,a0
	bra 	showErrorMessage

showErrorMessage:
	move.b 	(a0)+,d0
	beq	doneProgram
	jsr	ScrnCharWrite
	bra	showErrorMessage

doneProgram:
	jsr	Exit

invalidFileMsg:
	dc.b 	"Invalid file/File doesn't exist",CR,LF,NULL
emptyFileMsg:
	dc.b	"Empty file",CR,LF,NULL

;fetchChar:
  ;move.w $FFE000,d0
  ;bmi fetchChar         ;Loop while reads a < 0 value
  ;Read something > 0 => got a character