{-----------------------------}
{           SHOWNAME          }
{     by Jeff Duntemann       }
{                             }
{ Binary search demo program  }
{                             }
{      Turbo Pascal V2.0      }
{      Last Update 1/4/85     }
{-----------------------------}

{ Unlike most programs in this book, this program requires two }
{ external files to operate: FRIENDS.NAP and FRIENDS.KEY.  The }
{ two files will be included on the source listings diskette.  }
{ FRIENDS.NAP is a file of NAPREC containing some number of    }
{ name/address/phone records.  FRIENDS.KEY is a sorted key     }
{ file containing keys extracted from FRIENDS.NAP.  You can    }
{ write a utility to extract keys from a .NAP file and sort    }
{ them using either the SHELLSORT or QUIKSORT procedures given }
{ in Section 14. }


PROGRAM SHOWNAME;


TYPE STRING3     = STRING[3];
     STRING6     = STRING[6];
     STRING30    = STRING[30];
     STRING40    = STRING[40];
     STRING80    = STRING[80];
     STRING255   = STRING[255];
     PARM_ARRAY  = ARRAY[1..10] OF STRING40;

     NAPREC = RECORD
                NAME    : STRING30;
                ADDRESS : STRING30;
                CITY    : STRING30;
                STATE   : STRING3;
                ZIP     : STRING6
              END;

     NAPFILE = FILE OF NAPREC;

     KEY_REC = RECORD
                 REF : INTEGER;
                 KEY : STRING30
               END;

     KEY_FILE = FILE OF KEY_REC;


VAR I,J,K     : INTEGER;
    RAM_TAIL  : STRING[128] ABSOLUTE CSEG : $80;
    PARMS     : PARM_ARRAY;  { Holds command line parameters }
    RECNUM    : INTEGER;
    WORKREC   : NAPREC;
    WORKFILE  : NAPFILE;
    WORKKEY   : KEY_FILE;


{$I STRIPWHT.SRC }   { Described in Section 15.1 }

{$I PARSTAIL.SRC }   { Described in Section 15.2 }


{>>>>KEY_SEARCH<<<<}

FUNCTION KEY_SEARCH(VAR KEYS     : KEY_FILE;
                    VAR KEY_REF  : INTEGER;
                        MATCH_IT : STRING80) : BOOLEAN;

VAR HI,LO,MID   : INTEGER;
    REC_COUNT   : INTEGER;
    SEARCH_REC  : KEY_REC;
    FOUND       : BOOLEAN;
    COLLIDED    : BOOLEAN;

BEGIN
  KEY_REF := 0;
  REC_COUNT := FILESIZE(KEYS);
  HI := REC_COUNT;
  LO := 0;
  KEY_SEARCH := FALSE; FOUND := FALSE; COLLIDED := FALSE;

  MID := (LO + HI) DIV 2;    { Calc first midpoint }

  IF REC_COUNT > 0 THEN      { Don't search if file is empty }
    REPEAT
      SEEK(KEYS,MID);
      READ(KEYS,SEARCH_REC);

           { Was there a collision between MID & LO or MID & HI? }
      IF (LO = MID) OR (HI = MID) THEN COLLIDED := TRUE;
      IF MATCH_IT = SEARCH_REC.KEY THEN  { Found it! }
        BEGIN
          FOUND := TRUE;             { Set found flag... }
          KEY_SEARCH := TRUE;        { ...and function value... }
          KEY_REF := SEARCH_REC.REF  { ...and key into data file }
        END
      ELSE                  { No luck...divide and try again... }
        BEGIN
          IF MATCH_IT > SEARCH_REC.KEY THEN LO := MID
            ELSE HI := MID;             { Halve the field }
          MID := (LO + HI) DIV 2;       { Recalc the midpoint }
          KEY_REF := MID                { Save MID in KEY_REF }
        END
    UNTIL COLLIDED OR FOUND
  END;


{ SHOWNAME MAIN }

BEGIN
  CLRSCR;
  GOTOXY(1,10);
  PARSE_TAIL(I,PARMS);     { Parse the command tail }
  IF I < 1 THEN            { Missing parms error }
    BEGIN
      WRITELN('<<Error!>> You must enter a name on the command line:');
      WRITELN('           A>SHOWNAME Duntemann*Jeff ')
    END
  ELSE
    BEGIN
      ASSIGN(WORKFILE,'FRIENDS.NAP');  { Open the names data file }
      RESET(WORKFILE);
      ASSIGN(WORKKEY,'FRIENDS.KEY');   { Open the names key file }
      RESET(WORKKEY);
      IF KEY_SEARCH(WORKKEY,RECNUM,PARMS[1]) THEN  { If key is found...}
        BEGIN                          { We have record # into data file }
          SEEK(WORKFILE,RECNUM);       { Seek to record # in data file }
          READ(WORKFILE,WORKREC);      { Read data record from data file }
          WITH WORKREC DO              { and display the name/address data }
            BEGIN
              WRITELN('>>NAME    : ',NAME);
              WRITELN('  ADDRESS : ',ADDRESS);
              WRITELN('  CITY    : ',CITY);
              WRITELN('  STATE   : ',ZIP);
            END
        END
      ELSE
        WRITELN('>>Sorry, ',PARMS[1],' not found.');
    END
END.