SORT.ASM

TITLE   SORT FILTER FOR MS-DOS
;
; Sort  /R /+n
; /R -> reverse sort
; /+n -> sort on column n
;
; Written by:   Chris Peters
;
; Modification History:
;           3-18-83 MZ  Fix CR-LF at end of buffer
;                       Fix small file sorting
;                       Fix CR-LF line termination bug
;                       Comment the Damn source
;
FALSE   EQU     0
TRUE    EQU     NOT FALSE

;NOTE:	"internat" must be false if KANJI version
internat	equ	true
;NOTE:	see above

.xlist
.xcref
        INCLUDE DOSSYM.ASM
.cref
.list

sys     MACRO   name                    ; system call macro
        MOV     AH,name
        INT     21h
        ENDM
save    MACRO   reglist                 ; push those registers
IRP reg,<reglist>
        PUSH    reg
ENDM
ENDM
restore MACRO   reglist                 ; pop those registers
IRP reg,<reglist>
        POP     reg
ENDM
ENDM

MAXREC  EQU     256                     ; MAXIMUM NUL RECORD SIZE

SPACE   EQU     0                       ; Offset zero in the allocated block
BUFFER  EQU     MAXREC                  ; Offset MAXREC in the allocated block

SUBTTL  Segments used in load order


CODE    SEGMENT
CODE    ENDS

CONST   SEGMENT PUBLIC BYTE
CONST   ENDS

CSTACK  SEGMENT STACK
        DB 128 DUP (0)                  ; initial stack to be clear
CSTACK  ENDS

DG      GROUP   CODE,CONST,CSTACK

CODE    SEGMENT
ASSUME  CS:DG,DS:NOTHING,ES:NOTHING,SS:CSTACK

COLUMN  DW      0                       ; COLUMN TO USE FOR KEY + 1
SWITCH  DB      '/'

SORT:
;
; check for proper version number of system
;
        sys     GET_VERSION
        XCHG    AH,AL                   ; Turn it around to AH.AL
        CMP     AX,200H                 ; Version 2.00 only
        JAE     OKDOS                   ; Success
        MOV     DX,OFFSET DG:BADVER     ; Get error message
        PUSH    CS                      ; Get DS addressability
        POP     DS
        sys     STD_CON_STRING_OUTPUT   ; Send to STDOUT
        PUSH    ES                      ; long segment
        PUSH    COLUMN                  ; offset zero
LONG_RET    PROC    FAR
        RET                             ; long return to OS
LONG_RET    ENDP
;
; get proper switch character
;
OKDOS:
        MOV     AL,0                    ; Get current switch character
        sys     CHAR_OPER
        MOV     SWITCH,DL
;
; parse command line
;
        MOV     SI,80H                  ; pointer to command line
        CLD                             ; go left to right
        XOR     CX,CX
        LODSB
        MOV     CL,AL                   ; CX = length of command line
SWITCH_LOOP:
        CALL    GET_CHAR                ; get a character
        CMP     AL,SWITCH               ; beginning of switch?
        JNZ     SWITCH_LOOP             ; No, get next character
        CALL    GET_CHAR                ; get 1st char of switch
        CMP     AL,'+'                  ; Column to sort?
        JZ      SWITCH_NUMBER           ; Yes, parse a number
        OR      AL,20h                  ; convert to lower case
        CMP     AL,'r'                  ; Reverse sort?
        JNZ     SWITCH_LOOP             ; No, get next switch
        MOV     CS:CODE_PATCH,72h       ; sleaze JAE into JB
        JMP     SWITCH_LOOP             ; get next switch
SWITCH_NUMBER:
        MOV     COLUMN,0                ; start off at 0
SWITCH_NEXT_NUMBER:
        CALL    GET_CHAR                ; get supposed digit
        SUB     AL,'0'                  ; convert to number
        JB      SWITCH_LOOP             ; less than '0'
        CMP     AL,9                    ; is it a valid digit?
        JA      SWITCH_LOOP             ; nope, get next switch
        CBW                             ; make it a full word
        MOV     BX,AX                   ; save byte away
        MOV     AX,10                   ; decimal number system
        MUL     COLUMN                  ; take previous result
        ADD     AX,BX                   ; add in low order digit
        MOV     COLUMN,AX               ; save away value
        JMP     SWITCH_NEXT_NUMBER      ; get next character
GET_CHAR:
        JCXZ    END_GET                 ; End of line
        DEC     CX                      ; dec char count
        LODSB                           ; get the character
        RET                             ; return
END_GET:
        POP     AX                      ; nuke return on stack
;
; set up column for proper sort offset
;
END_SWITCH:
        ADD     COLUMN,2
        CMP     COLUMN,2
        JZ      GOT_COL
        DEC     COLUMN

;
; Get sorting area, no more than 64K
;
GOT_COL:
        MOV     BX,1000H                ; 64K worth of paragraphs
GET_MEM:
        sys     ALLOC                   ; allocate them from somewhere
        JNC     GOT_MEM                 ; if error, BX has amount free, try to get it
        OR      BX,BX                   ; but, is BX = 0?
        JNZ     GET_MEM                 ; nope, try to allocate it
        JMP     SIZERR                  ; complain

GOT_MEM:
        MOV     DS,AX                   ; Point DS to buffer
        MOV     ES,AX                   ; and point ES to buffer
        MOV     CL,4                    ; 2^4 bytes per paragraph
        SHL     BX,CL                   ; Find out how many bytes we have

;
; clear out temporary record area
;
        MOV     CX,MAXREC/2             ; Size of temporary buffer (words)
        MOV     AX,'  '                 ; Character to fill with
        MOV     DI,SPACE                ; Beginning of temp buffer
        REP     STOSW                   ; Blam.
;
; read in file from standard input
;
        MOV     DX,BUFFER + 2           ; DX = place to begin reading
        MOV     CX,BX                   ; CX is the max number to read
        SUB     CX,MAXREC + 2           ; remember offset of temp buffer
SORTL:
        XOR     BX,BX                   ; Standard input
        sys     READ                    ; Read it in
        ADD     DX,AX                   ; Bump pointer by count read
        SUB     CX,AX                   ; subtract from remaining the count read
        JZ      SIZERR                  ; if buffer is full then error
        OR      AX,AX                   ; no chars read -> end of file
        JNZ     SORTL                   ; there were chars read. go read again
        JMP     SHORT SIZOK             ; trim last ^Z terminated record
SIZERR:
        MOV     SI,OFFSET DG:ERRMSG     ; not enough memory error
ERROR_EXIT:
        PUSH    CS                      ; DS addressability
        POP     DS
        LODSW                           ; get length
        MOV     CX,AX                   ; put into appropriate register
        MOV     DX,SI                   ; get output destination
        MOV     BX,2                    ; output to standard error
        sys     WRITE                   ; and write it out
        MOV     AL,1                    ; return an error code
        sys     EXIT

;
; Look for a ^Z. Terminate buffer at 1st ^Z.
;
SIZOK:
        MOV     BX,DX                   ; save end pointer
        MOV     CX,DX                   ; get pointer to end of text
        SUB     CX,BUFFER+2             ; dif in pointers is count
        MOV     AL,1AH                  ; char is ^Z
        MOV     DI,BUFFER+2             ; point to beginning of text
        REPNZ   SCASB                   ; find one
        JNZ     NoBack                  ; nope, try to find CRLF
        DEC     BX                      ; pretend that we didn't see ^Z
NoBack:
        SUB     BX,CX                   ; sub from endpointer the number left
        SUB     BX,2                    ; Hope for a CR LF at end
        CMP     WORD PTR [BX],0A0Dh     ; Was there one there?
        JZ      GOTEND                  ; yep, here is the end
        ADD     BX,2                    ; nope, bump back to SCASB spot
        CMP     BYTE PTR [BX],AL        ; Was there ^Z there?
        JZ      GOTEND                  ; yep, chop it
        INC     BX                      ; Nope, skip last char
GOTEND:
        MOV     BP,BX                   ; BP = filesize-2(CRLF)+temp buffer+2
        MOV     WORD PTR DS:[BP],0      ; 0 at end of the file
;
;  We now turn the entire buffer into a linked list of chains by
;  replacing CRLFs with the length of the following line (with 2 for CRLF)
;
        MOV     BX,BUFFER               ; pointer to line head (length)
        MOV     DI,BUFFER+2             ; pointer to line text
REPLACE_LOOP:
        MOV     AL,13                   ; char to look for is CR
        MOV     CX,BP                   ; count = end pointer
        SUB     CX,DI                   ; chop off start point to get length
        INC     CX                      ; add 1???
REPLACE_SCAN:
        REPNZ   SCASB                   ; look for CR
        JNZ     REPLACE_SKIP            ; count exhausted
        CMP     BYTE PTR [DI],10        ; LF there?
        JNZ     REPLACE_SCAN            ; nope, continue scanning
REPLACE_SKIP:
        MOV     AX,DI                   ; AX to point after CR
        DEC     AX                      ; AX to point to CR
        save    <AX>                    ; save pointer
        SUB     AX,BX                   ; AX is length of line found
        MOV     [BX],AX                 ; stuff it in previous link
        restore <BX>                    ; get pointer to next
        INC     DI                      ; skip LF???
        JCXZ    END_REPLACE_LOOP        ; no more to scan -> go sort
        JMP     REPLACE_LOOP            ; look for next

END_REPLACE_LOOP:
        MOV     WORD PTR [BX],0         ; terminate file with nul
        LEA     BP,[BX+2]               ; remember the null line at end
        MOV     DI,BUFFER               ; DI is start of unsorted section

;
; begin sort. Outer loop steps over all unsorted lines
;
OUTER_SORT_LOOP:
        MOV     BX,DI                   ; BX is start of unsorted section
        MOV     SI,BX                   ; SI is scanning place link
        CMP     WORD PTR [BX],0         ; are we at the end of the buffer?
        JNZ     INNER_SORT_LOOP         ; No, do inner process
        JMP     END_OUTER_SORT_LOOP     ; yes, go dump out

;
; BX points to best guy found so far. We scan through the sorted section
; to find an appropriate insertion point
;
INNER_SORT_LOOP:
        ADD     SI,[SI]                 ; link to next fellow
        MOV     AX,[SI]                 ; get length of comparison guy
        OR      AX,AX                   ; test for end of buffer
        JZ      END_INNER_SORT_LOOP     ; if zero then figure out insertion
        save    <SI,DI>                 ; save SI,DI
        MOV     DI,BX                   ; DI = pointer to tester link
        SUB     AX,COLUMN               ; adjust length for column
        JA      AXOK                    ; more chars in tester than column?
        MOV     SI,SPACE                ; point SI to blank area
        MOV     AX,MAXREC               ; make AX be max length
AXOK:
        MOV     DX,[DI]                 ; get length of best guy
        SUB     DX,COLUMN               ; adjust length for column
        JA      DXOK                    ; there are more chars after column
        MOV     DI,SPACE                ; point air to a space
        MOV     DX,MAXREC               ; really big record
DXOK:
        MOV     CX,AX                   ; AX is shortest record
        CMP     AX,DX                   ; perhaps DX is shorter
        JB      SMALL                   ; nope, leace CX alone
        MOV     CX,DX                   ; DX is shorter, put length in CX
SMALL:
        ADD     DI,COLUMN               ; offset into record
        ADD     SI,COLUMN               ; offset into other record
if	not	internat
        REPZ    CMPSB                   ; compare every one
	endif
if	internat
	push	bx
	push	ax
	mov	bx,offset dg:table
tloop:	lodsb
	xlat	byte ptr cs:[bx]
	mov	ah,al
	mov	al,es:[di]
	inc	di
	xlat	byte ptr cs:[bx]
	cmp	ah,al
	loopz	tloop
	pop	ax
	pop	bx
	endif
        restore <DI,SI>                 ; get head pointers back
        JNZ     TESTED_NOT_EQUAL        ; didn't exhaust counter, conditions set
        CMP     AX,DX                   ; check string lengths
TESTED_NOT_EQUAL:
;
; note! jae is patched to a jbe if file is to be sorted in reverse!
;
CODE_PATCH LABEL BYTE
        JAE     INNER_SORT_LOOP         ; if this one wasn't better then go again
        MOV     BX,SI                   ; it was better, save header
        JMP     INNER_SORT_LOOP         ; and scan again

END_INNER_SORT_LOOP:
        MOV     SI,BX                   ; SI is now the best person
        CMP     SI,DI                   ; check best for current
        JZ      END_INSERT              ; best equals current, all done

;
; SI points to best line found so far
; DI points to a place to insert this line
; DI is guaranteed to be < SI
; make room for line at destination
;
        MOV     DX,[SI]                 ; get length of line
        save    <SI,DI>                 ; save positions of people
        STD                             ; go right to left
        MOV     CX,BP                   ; get end of file pointer
        SUB     CX,DI                   ; get length from destination to end
        MOV     SI,BP                   ; start from end
        DEC     SI                      ; SI points to end of file
        MOV     DI,SI                   ; destination is end of file
        ADD     DI,DX                   ; DI points to new end of file
        REP     MOVSB                   ; blam. Move every one up
        CLD                             ; back left to right
        restore <DI,SI>                 ; get old source and destination
;
;  MOVE NEW LINE INTO PLACE
;
        save    <DI>                    ; save destination
        ADD     SI,DX                   ; adjust for previous movement
        save    <SI>                    ; save this value
        MOV     CX,DX                   ; get number to move
        REP     MOVSB                   ; blam. move the new line in
        restore <SI,DI>                 ; get back destination and new source
;
;  DELETE LINE FROM OLD PLACE
;
        save    <DI>                    ; save destination
        MOV     CX,BP                   ; pointer to end
        ADD     CX,DX                   ; remember bump
        SUB     CX,SI                   ; get count of bytes to move
        INC     CX                      ; turn it into a word
        SHR     CX,1                    ; or a count of words
        MOV     DI,SI                   ; new destination of move
        ADD     SI,DX                   ; offset of block
        REP     MOVSW                   ; blam, squeeze out the space
        restore <DI>                    ; get back original destination
        MOV     WORD PTR DS:[BP-2],0    ; remake the end of file mark

END_INSERT:
        ADD     DI,[DI]                 ; link to next guy
        JMP     OUTER_SORT_LOOP         ; and continue
;
;       PUT BACK IN THE CR-LF
;
END_OUTER_SORT_LOOP:
        MOV     DI,BUFFER               ; start at beginning (where else)
        MOV     CX,[DI]                 ; count of butes

INSERT_LOOP:
        ADD     DI,CX                   ; point to next length
        MOV     CX,[DI]                 ; get length
        MOV     WORD PTR [DI],0A0DH     ; replace length with CRLF
        CMP     CX,0                    ; check for end of file
        JNZ     INSERT_LOOP             ; nope, try again

WRITE_FILE:
        MOV     DX,BUFFER+2             ; get starting point
        MOV     CX,BP                   ; pointer to end of buffer
        SUB     CX,DX                   ; dif in pointers is number of bytes
        MOV     BX,1                    ; to standard output
        sys     WRITE                   ; write 'em out
        JC      BADWRT                  ; some bizarre error -> flag it
        CMP     AX,CX                   ; did we write what was expected?
        JZ      WRTOK                   ; yes, say bye bye
BADWRT:
        MOV     SI,OFFSET dg:ERRMSG2    ; strange write error
        JMP     ERROR_EXIT              ; bye bye
WRTOK:
        XOR     AL,AL                   ; perfect return (by convention)
        sys     EXIT                    ; bye!

CODE    ENDS

CONST   SEGMENT PUBLIC BYTE
        EXTRN   BADVER:BYTE,ERRMSG:BYTE,ERRMSG2:BYTE
if	internat
	extrn	table:byte
	endif
CONST   ENDS

SUBTTL  Initialized Data
PAGE
CSTACK   SEGMENT STACK
         DB      96 dup (0)
CSTACK   ENDS

        END     SORT