.J
NEW
10 REM Text File Viewer
20 REM by Garry Lancaster, August 1995
30 *NAME VIEWER
40 ON ERROR K$=INKEY$(100):GOTO 100
100 CLS
110 VDU 1,ASC("R")
120 PRINT " File Viewer - by Garry Lancaster "
130 VDU 1,ASC("R")
140 PRINT:PRINT
150 INPUT "File to view: "F$
160 C=OPENIN(F$)
170 V$=LEFT$(("VIEW:"+F$),15)
180 OSCLI "*NAME "+V$
190 FL=EXT#C
200 N=200:MAX=9999999
210 DIM L(N)
220 P=1:E=1:F=1:L(P)=0
230 LI=1
240 VDU 1,ASC("C")
250 ON ERROR K$=INKEY$(100):GOTO 320
300 REM Main Loop
305 IF LI<1 THEN LI=1
307 IF LI>MAX THEN LI=MAX
310 PROCdisplay(LI)
320 K=GET
330 IF K<>0 GOTO 320
340 K=GET
350 IF K=255 AND LI>1 THEN LI=LI-1:GOTO 305
360 IF K=254 THEN PROCdownline:GOTO 320
370 IF K=251 AND LI>1 THEN LI=LI-7:GOTO 305
380 IF K=250 THEN LI=LI+7:GOTO 305
390 GOTO 320
9000 REM Ensure element number in range
9010 DEF FNelement(X)
9020   IF X<1 THEN X=X+N
9030   IF X>N THEN X=X-N
9040 =X
9100 REM Give element number for line
9110 DEF FNlinepos(X)=FNelement(X-F+P)
9200 REM Add pointer to line at end of list
9210 DEF PROCaddend(X)
9220   E=E+1
9230   L(FNlinepos(E))=X
9240   IF P=FNlinepos(E) THEN P=FNelement(P+1):F=F+1
9250 ENDPROC
9300 REM Add pointer to line at start of list
9310 DEF PROCaddstart(X)
9320   F=F-1
9330   P=FNelement(P-1)
9340   L(FNlinepos(F))=X
9350   IF P=FNlinepos(E) THEN E=E-1
9360 ENDPROC
9400 REM Display text from line X
9410 DEF PROCdisplay(X)
9415 LOCAL A
9420   IF X>MAX THEN X=MAX
9430   IF X<=E GOTO 9490
9440     PTR#C=L(FNlinepos(E))  
9450     INPUT#C,T$
9460     IF (FL-PTR#C)<2 MAX=E:GOTO 9420
9470     PROCaddend(PTR#C)
9480   GOTO 9430
9490   IF X>=F GOTO 9570
9500     A=L(FNlinepos(F))-256:IF A<0 THEN A=0
9510     PTR#C=A
9520     A=PTR#C
9530     INPUT#C,T$
9540     IF PTR#C<L(FNlinepos(F)) GOTO 9520
9550     PROCaddstart(A)
9560   GOTO 9490
9570   PTR#C=L(FNlinepos(X))
9580   CLS
9590   FOR A=1 TO 8  
9595     IF (FL-PTR#C)<2 GOTO 9640
9600     PROCdispnext(A-1)
9620     IF (FL-PTR#C)<2 GOTO 9640
9630     IF X+A>E PROCaddend(PTR#C)
9640   NEXT A
9650 ENDPROC
9700 REM Display a line
9710 DEF PROCdispnext(X)
9720   INPUT#C,T$
9725   IF ASC(T$)=10 THEN T$=MID$(T$,2)
9730   IF X THEN PRINT
9740   PRINT LEFT$(T$,80);
9750 ENDPROC
9800 REM Down a single line
9810 DEF PROCdownline
9820   IF (FL-PTR#C)<2 GOTO 9850
9830   PROCdispnext(1):LI=LI+1
9835   IF (FL-PTR#C)<2 GOTO 9850
9840   IF LI+7>E PROCaddend(PTR#C)
9850 ENDPROC