🚀 go-pugleaf

EMail : boyles@lux.latrobe.edu.au
        
Why does the Pascal version of this program behave exactly as expected while the
C++ version does not?




******************************* PASCAL VERSION *******************************

program show;


uses crt,dos,crt_,strings;


const maxstring=127;
      escape=chr(27);
      space=' ';
      up='H';
      down='P';
      pageup='I';
      pagedown='Q';
      left='K';
      right='M';
      home='G';
      end_='O';
      null=chr(0);


type nodetypeptr=^nodetype;
     nodetype=record
                   fileline:string;
                   filelinenum:integer;
                   next,previous:nodetypeptr;
              end;


function empty(posptr:nodetypeptr):boolean;

begin
     empty:=posptr=nil;
end;


procedure initialize(var listptr:nodetypeptr);

begin
     listptr:=nil;
end;


procedure add(var listptr:nodetypeptr;fileline:string;filelinenum:integer);

var newptr,tempptr:nodetypeptr;

begin
      new(newptr);
      newptr^.fileline:=fileline;
      newptr^.filelinenum:=filelinenum;
      if (listptr=nil) then
      begin
           (listptr):=newptr;
           (listptr)^.next:=nil;
           (listptr)^.previous:=nil;
      end
      else
      begin
           tempptr:=listptr;
           while (tempptr^.next<>nil) do
           begin
                tempptr:=tempptr^.next;
           end;
           tempptr^.next:=newptr;
           newptr^.next:=nil;
           newptr^.previous:=tempptr;
      end;
end;


procedure remove(var listptr:nodetypeptr);

var tempptr:nodetypeptr;

begin
     tempptr:=listptr;
     listptr:=listptr^.next;
     listptr^.previous:=nil;
     dispose(tempptr);
end;


procedure setpos(var posptr:nodetypeptr;filelinenum:integer);

begin
     while (posptr^.filelinenum<>filelinenum) do
     begin
          if (posptr^.filelinenum>filelinenum) then
          begin
               posptr:=posptr^.previous;
          end
          else if (posptr^.filelinenum<filelinenum) then
          begin
               posptr:=posptr^.next;
          end;
     end;
end;


procedure writescreenfull(width,height:word;posptr:nodetypeptr;stringpos:word);

var y,i:word;
    line1:string;

begin
     window(1,1,width,height);
     clrscr;
     window(1,1,width,height+1);
     y:=1;
     while (y<=height) and (not empty(posptr^.next)) do
     begin
          gotoxy(1,y);
          i:=stringpos;
          while (i<=length(posptr^.fileline)) and ((i-stringpos)<=width) do
          begin
               write(posptr^.fileline[i]+'');
               i:=i+1;
          end;
          writeln;
          posptr:=posptr^.next;
          y:=y+1;
     end;
end;


procedure main;

var infile:text;
    x,width,height,back,fore:word;
    ch:char;
    numfilelines,filelinenum:integer;
    listptr,posptr:nodetypeptr;
    fileline,bottomfileline:string;
    stringpos:word;

begin
     if (paramcount<1) then
     begin
          writeln;
          writeln('Show what . . .');
     end
     else
     begin
          {$I-}
          assign(infile,paramstr(1));
          {$I+}
          if (doserror<>0) then
          begin
               writeln;
               write('infile ');
               write(paramstr(1));
               writeln(' not found . . .');
          end
          else
          begin
               reset(infile);
               initialize(listptr);
               filelinenum:=0;
               while (not eof(infile)) do
               begin
                    readln(infile,fileline);
                    add(listptr,fileline,filelinenum);
                    filelinenum:=filelinenum+1;;
               end;
               numfilelines:=filelinenum-1;
               close(infile);
               posptr:=listptr;
               fore:=textattr and $0f;
               back:=(textattr and $70) div $10;
               height:=hi(windmax);
               width:=lo(windmax);
               bottomfileline:=' '+chr(24)+' '+chr(25)+' pgup  pgdn  s "string" : (search for string)  esc : (quit)';
               for x:=length(bottomfileline)+1 to width do
               begin
                    bottomfileline:=bottomfileline+' ';
               end;
               set_cursor(none);
               clrscr;
               textcolor(back);
               textbackground(fore);
               gotoxy(1,height);
               write(bottomfileline);
               textcolor(fore);
               textbackground(back);
               height:=height-1;
               filelinenum:=1;
               stringpos:=1;
               writescreenfull(width,height,posptr,stringpos);
               ch:=space;
               while (ch<>escape) do
               begin
                    while ((ch<>up) and (ch<>down) and (ch<>pageup) and
                           (ch<>pagedown) and (ch<>escape) and (ch<>left) and
                           (ch<>right) and (ch<>end_) and (ch<>home)) do
                    begin
                         ch:=readkey;
                         if (ch=null) then
                         begin
                              ch:=readkey;
                         end;
                    end;
                    if (ch=up) then
                    begin
                         if ((filelinenum-1)>=1) then
                         begin
                              filelinenum:=filelinenum-1;
                         end
                         else
                         begin
                              filelinenum:=1;
                         end;
                         setpos(posptr,filelinenum);

                    end
                    else if (ch=down) then
                    begin
                         if ((filelinenum+1+height)<=numfilelines) then
                         begin
                              filelinenum:=filelinenum+1
                         end
                         else
                         begin
                              filelinenum:=numfilelines-height+1;
                         end;
                         setpos(posptr,filelinenum);
                    end
                    else if (ch=pageup) then
                    begin
                         if ((filelinenum-height+1)>=1) then
                         begin
                              filelinenum:=filelinenum-height+1;
                         end
                         else
                         begin
                              filelinenum:=1;
                         end;
                         setpos(posptr,filelinenum);
                    end
                    else if (ch=pagedown) then
                    begin
                         if (((filelinenum+height-1)<=numfilelines) and
                             ((numfilelines-(filelinenum+height-1))>=(height-1))) then
                         begin
                              filelinenum:=filelinenum+height-1;
                         end
                         else
                         begin
                              filelinenum:=numfilelines-height+1;
                         end;
                         setpos(posptr,filelinenum);
                    end
                    else if (ch=left) then
                    begin
                         if (stringpos>1) then
                         begin
                              stringpos:=stringpos-1;
                         end;
                    end
                    else if (ch=right) then
                    begin
                         if (stringpos<=(maxstring-width)) then
                         begin
                              stringpos:=stringpos+1;
                         end;
                    end
                    else if (ch=end_) then
                    begin
                         stringpos:=maxstring-width+1;
                    end
                    else if (ch=home) then
                    begin
                         stringpos:=1;
                    end;
                    if (ch<>escape) then
                    begin
                         ch:=space;
                    end;
                    writescreenfull(width,height,posptr,stringpos);
               end;
               height:=height+1;
               window(1,1,width,height);
               clrscr;
               set_cursor(line);
               while (not empty(listptr)) do
               begin
                    remove(listptr);
               end;
          end;
     end;
end;


begin
     main;
end.




******************************** C++ VERSION *********************************

#include <stdio.h>
#include <conio.h>
#include <string.h>
#include <alloc.h>
#include <process.h>

const maxstring=127;
const lineend='\n';
const escape=27;
const null='\0';
const space=' ';
const up='H';
const down='P';
const pageup='I';
const pagedown='Q';
const left='K';
const right='M';
const home='G';
const end_='O';


typedef char string[maxstring];
typedef struct nodetypetag{string line;int linenum;struct nodetypetag *next,*previous;} nodetype;
typedef nodetype *nodetypeptr;

string line,line_,line1,bottomline;

char empty(nodetypeptr posptr)
{
     return(posptr==NULL);
}

void initialize(nodetypeptr *listptr)
{
     *listptr=NULL;
}

void add(nodetypeptr *listptr,char *fileline,int Linenum)
{
      nodetypeptr newptr,tempptr;

      newptr=(nodetypeptr)malloc(sizeof(nodetype));
      strcpy(newptr->line,fileline);
      newptr->linenum=Linenum;
      if (*listptr==NULL)
      {
           (*listptr)=newptr;
           (*listptr)->next=NULL;
           (*listptr)->previous=NULL;
      }
      else
      {
           tempptr=*listptr;
           while (tempptr->next!=NULL)
           {
                tempptr=tempptr->next;
           }
           tempptr->next=newptr;
           newptr->next=NULL;
           newptr->previous=tempptr;
      }
}

void remove(nodetypeptr *listptr)
{
     nodetypeptr tempptr;

     tempptr=*listptr;
     *listptr=(*listptr)->next;
     (*listptr)->previous=NULL;
     free(tempptr);
}

void setpos(nodetypeptr *posptr,int linenum)
{
     while ((*posptr)->linenum!=linenum)
     {
          if ((*posptr)->linenum>linenum)
          {
               *posptr=(*posptr)->previous;
          }
          else if ((*posptr)->linenum<linenum)
          {
               *posptr=(*posptr)->next;
          }
     }
}

void writescreenfull(char width,char height,nodetypeptr posptr,char stringpos)
{
     char y;

     window(1,1,width,height);
     clrscr();
     window(1,1,width,height+1);
     y=1;
     while ((y<=height) && (!empty(posptr->next)))
     {
          gotoxy(1,y);
          strcpy(line_,posptr->line);
          line__=&(line_[stringpos]);
          strncpy(line,line__,width-1);
          strcat(line,null);
          cputs(line);
          posptr=posptr->next;
          y++;
     }
}

void removelineends(char *strings,unsigned int maxstrings)
{
     unsigned int i;

     i=0;
     while ((i<maxstrings) && (strings[i]!=lineend))
     {
          i++;
     }
     strings[i]=null;
}

void main(int argc,char *argv[])
{
     FILE *file;
     char x,ch,width,height,back,fore,stringpos;
     int numlines,linenum;
     text_info info;
     nodetypeptr listptr,posptr;


     if (argc<2)
     {
          cputs("\nShow what . . .\n");
     }
     else
     {
          file=fopen(argv[1],"rt");
          if (file==NULL)
          {
               cprintf("\nFile %s not found . . .\n",argv[1]);
          }
          else
          {
               rewind(file);
               initialize(&listptr);
               linenum=0;
               while (fgets(line,maxstring,file)!=NULL)
               {
                    removelineends(line,maxstring);
                    add(&listptr,line,linenum);
                    linenum++;
               }
               numlines=linenum--;
               fclose(file);
               posptr=listptr;
               gettextinfo(&info);
               fore=info.attribute&0x0f;
               back=(info.attribute&0x70)/0x10;
               height=info.screenheight;
               width=info.screenwidth;
               strcpy(bottomline,"  \30  \31  pgup  pgdn  s <string> (search for string)  esc (quit)");
               for(x=strlen(bottomline)+1;x<width;x++)
               {
                    strcat(bottomline," ");
               }
               _setcursortype(_NOCURSOR);
               clrscr();
               textcolor(back);
               textbackground(fore);
               gotoxy(1,height);
               cputs(bottomline);
               textcolor(fore);
               textbackground(back);
               height--;
               linenum=1;
               stringpos=1;
               writescreenfull(width,height,posptr,stringpos);
               ch=space;
               while (ch!=escape)
               {
                    while ((ch!=up) && (ch!=down) && (ch!=pageup) &&
                           (ch!=pagedown) && (ch!=escape) && (ch!=left) &&
                           (ch!=right) && (ch!=end_) && (ch!=home))
                    {
                         ch=getch();
                         if (ch==null)
                         {
                              ch=getch();
                         }
                    }
                    if (ch==up)
                    {
                         if ((linenum-1)>=1)
                         {
                              linenum--;
                         }
                         else
                         {
                              linenum=1;
                         }
                         setpos(&posptr,linenum);

                    }
                    else if (ch==down)
                    {
                         if ((linenum+1+height)<=numlines)
                         {
                              linenum++;
                         }
                         else
                         {
                              linenum=numlines-height+1;
                         }
                         setpos(&posptr,linenum);
                    }
                    else if (ch==pageup)
                    {
                         if ((linenum-height+1)>=1)
                         {
                              linenum=linenum-height+1;
                         }
                         else
                         {
                              linenum=1;
                         }
                         setpos(&posptr,linenum);
                    }
                    else if (ch==pagedown)
                    {
                         if (((linenum+height-1)<=numlines) && ((numlines-(linenum+height-1))>=(height-1)))
                         {
                              linenum=linenum+height-1;
                         }
                         else
                         {
                              linenum=numlines-height+1;
                         }
                         setpos(&posptr,linenum);
                    }
                    else if (ch==left)
                    {
                         if (stringpos>1)
                         {
                              stringpos--;
                         }
                    }
                    else if (ch==right)
                    {
                         if (stringpos<=(maxstring-width))
                         {
                              stringpos++;
                         }
                    }
                    else if (ch==end_)
                    {
                         stringpos=maxstring-width+1;
                    }
                    else if (ch==home)
                    {
                         stringpos=1;
                    }
                    if (ch!=escape)
                    {
                         ch=space;
                    }
                    writescreenfull(width,height,posptr,stringpos);
               }
               height+=1;
               window(1,1,width,height);
               clrscr();
               _setcursortype(_NORMALCURSOR);
               while (!empty(listptr))
               {
                    remove(&listptr);
               }
          }
     }
}