BBS in a Box 5/BBS in a Box -Volume V (BBS in a Box) (April 1992).iso/Files/Prog/M/Lex.cpt/Lex/LEXLIB.π folder/MAC_YYLEX.C

C/C++ Source or Header | 1990-06-04 | 5.0 KB | 220 lines | [TEXT/KAHL]

/*
  HEADER: CUG    nnn.nn;
  TITLE:    LEX - A Lexical Analyser Generator
  VERSION:       1.0 for IBM-PC
  DATE:    Jan 30, 1985
  DESCRIPTION:   A Lexical Analyser Generator. From UNIX
  KEYWORDS:      Lexical Analyser Generator YACC C PREP
  SYSTEM:    IBM-PC and Compatiables
  FILENAME:      YYLEX.C
  WARNINGS:      This program is not for the casual user. It will
    be useful primarily to expert developers.
  CRC:    N/A
  SEE-ALSO:      YACC and PREP
  AUTHORS:       Scott Guthery 11100 leafwood lane Austin, TX 78750
  COMPILERS:     DESMET-C
  REFERENCES:    UNIX Systems Manuals
*/
/*
 * Bob Denny 28-Aug-82  Remove reference to stdio.h
 * Remove code to default lexin, change to call to
 * llstin(), generated by lex depending upon setting
 * of "-s" switch.  Eliminates hardwired dependency
 * on standard I/O library.  Moved declaration of
 * lexin to lexgetc().
 *
 * Bob Denny 31-Aug-82  Add call to lexswitch() in
 * the generated file, to switch to the table whose
 * name was given in the "-t" switch (or to "lextab"
 * if "-t" wasn't given).  Removed hardwired setting
 * of _tabp --> "lextab" here. Now handled automagically.
 *
 * Bob Denny 21-Oct-82  Add llinit() function to re-initialize
 * yylex(), making it serially reusable.
 *
 * Initialize _tabp to NULL so lexswitch() to real table happens
 * only once.
 *
 * Bob Denny 15-Apr-83 Move NBPW to LEX.H and make it 32 on VAX native,
 *    else 16.
 * Scott Guthery 20-Nov-83      Adapt for IBM PC & DeSmet C
 *
 *    Maarten Meijer 20 Apr 1990 -- Port to THINK C on the Mac, added call
 *        to yyinit() to allow reading yyparse() tables from resources
 */

/*
 * yylex for lex tables
 */
#ifdef  THINK_C
#include <stdlib.h>
#endif

#include "lex.h"

#define ERROR   256     /* yacc's value */

SHORTINT    tst__b(register SHORTINT c, unsigned char tab[]);
SHORTINT    llinp(void);
SHORTINT    llset(void);
void        llinit(void);
SHORTINT    yylex(void);
void        llstin(void);

tst__b(c, tab)
register SHORTINT    c;
unsigned char    tab[];
{
    return(tab[(c >> 3) & 037] & (1 << (c & 07)) );
}

struct  lextab  *_tabp = 0;

extern char     *llsave[];    /* Right-context look ahead buffer    */
char            *llbuf = NULL;        /* work buffer    */
char            *llp1 ;        /*= &llbuf[0];    /* pointer to next avail.in token */
char            *llp2 ;        /*= &llbuf[0];    /* pointer to end of lookahead */
char            *llend;        /*= &llbuf[0];    /* pointer to end of token */
char            *llebuf;    /*= &llbuf[sizeof(llbuf)]; */
SHORTINT        llbufsize = 0;
SHORTINT        lleof;
SHORTINT        yyline  = 0;

SHORTINT
yylex()
{
    register SHORTINT c, llstate;
    SHORTINT final, l, llk, i;

    register struct lextab *lextabp;
    unsigned char *cp;

    /*
    * Call llstin() to default lexin to stdin
    * and assign _tabp to "real" table.
    */
    llstin();    /* Initialize yylex() variables */
loop:
    llk = 0;
    if (llset())
        return(0);    /* Prevent EOF loop     */
    llstate = 0;
    final = -1;
    lextabp = _tabp;

    do {
        if (lextabp->lllook && (l = lextabp->lllook[llstate]))
            {
            for (c = 0; c < NBPW; c++)
                if (l&(1<<c))
                    llsave[c] = llp1;
            llk++;
            }
        if ((i = lextabp->llfinal[llstate]) != -1)
            {
            final = i;
            llend = llp1;
            }
        if ((c = llinp()) < 0)
            break;

        if ((cp = lextabp->llbrk) && llk==0 && tst__b(c, cp)) /* break char */
            {
            llp1--;
            break;
            }
    } while ((llstate = (*lextabp->llmove)(lextabp, c, llstate)) != -1);


    if (llp2 < llp1)
        llp2 = llp1;
    if (final == -1)
        {
        llend = llp1;
        if (llstate == 0 && c < 0)
            return(0);
        if ((cp = lextabp->llill) && tst__b(c, cp))
            {
            lexerror("Illegal character: %c (%d)", c, c);
            goto loop;
            }
        return(ERROR);
        }
    if (c = (final >> 11) & 037)
        llend = llsave[c-1];
    if ((c = (*lextabp->llactr)(final & 03777)) >= 0)
        return(c);
    goto loop;
}

SHORTINT
llinp()
{

    register c;
    register struct lextab *lextabp;
    register unsigned char *cp;

    lextabp = _tabp;
    cp = lextabp->llign;    /* Ignore class    */
    for (;;)
        {
        /*
        * Get the next character from the save buffer (if possible)
        * If the save buffer's empty, then return EOF or the next
        * input character.  Ignore the character if it's in the
        * ignore class.
        */
        c = (llp1 < llp2) ? *llp1 & 0377 : (lleof) ? EOF : lexgetc();
        if(c == '\n')
            yyline++;    /* added 90/06/03 MM */
        if (c >= 0)
            {    /* Got a character?     */
            if (cp && tst__b(c, cp))
                continue;       /* Ignore it    */
            if (llp1 >= llebuf)
                {   /* No, is there room?   */
                lexerror("Token buffer overflow");
                exit(1);
                }
            *llp1 = c;    /* Store in token buff  */
            llp1++;
            }
        else
            lleof = 1;    /* Set EOF signal       */
        return(c);
        }
}

SHORTINT
llset()
/*
 * Return TRUE if EOF and nothing was moved in the look-ahead buffer
 */

{
    register char *lp1, *lp2;

    for (lp1 = llbuf, lp2 = llend; lp2 < llp2;) {
        *lp1 = *lp2++;
        lp1++;
        }
    llend = llp1 = llbuf;
    llp2 = lp1;
    return(lleof && lp1 == llbuf);
}

/*
 * Re-initialize yylex() so that it can be re-used on
 * another file.
 */
void
llinit()
   {
   extern    void yyinit(void);
   llp1 = llp2 = llend = &llbuf[0];
   llebuf = llbuf + llbufsize;
   lleof = yyline = 0;
   yyinit();    /* to check for resources */
   }