The C Users' Group Library 1994 August/wc-cdrom-cusersgrouplibrary-1994-08.iso/listings/v_07_02/v7n2032a.txt

Text File | 1988-11-21 | 6KB | 183 lines

/*
 *  stgen.c - C++ program to GENerate State Tables.
 */

#include <stream.hpp>   /* Zortech uses ".hpp", not ".h" */
#include <stdlib.h>
#include <ctype.h>

const   MAXSYM  = 32+1; /* Maximum length of symbol     */
const   MAXSYMS = 100;  /* Max # of inputs or actions   */

enum toktype {
    END,    NAME,   NUMBER,     LPAREN = '(',   RPAREN = ')',
    COLON = ':',    NWLN = '\n'
    };

struct  symtab  {
    char    table[MAXSYMS][MAXSYM];
    int     n;      /* # of symbols in table */
    int     find(char *sym) {   /* find symbol in table */
        for(int i = 0; i < n; ++i)
            if(!strcmp(table[i], sym))
                return i;
        return -1;
        }
    };

int     linumb = 1;     /* current line number in input file */

main(int argc, char **argv) {
    void    getinpact(symtab *, symtab *);
    void    doheader(char *, symtab *, symtab *, char *, int);
    int     dostate(char *, symtab *, symtab *, symtab *, char *);
    void    synerr(char *);
    toktype lex(char *);
    char    tok[MAXSYM], matrix[MAXSYM], defact[MAXSYM];
    int     nstates;
    toktype tt;
    static  symtab  inputs, actions, allinputs;    /* too big for stack */

    while((tt=lex(matrix)) == NWLN) /* eat empty lines */
        ;
    if(tt != NAME)
        synerr( "Expecting name of state transition matrix." );
    if(lex(tok) != LPAREN)
        synerr( "Expecting left paren." );
    if(lex(defact) != NAME)
        synerr( "Expecting name of default action." );
    if(lex(tok) != RPAREN)
        synerr( "Expecting right paren after default action." );
    if(lex(tok) != NUMBER)
        synerr( "Expecting # of states after right paren." );
    else
        nstates = atoi(tok);
    if(lex(tok) != NWLN)
        synerr( "Expecting newline after # of states." );
    getinpact(&allinputs, &actions);
    doheader(matrix, &allinputs, &actions, defact, nstates);
    while((tt=lex(tok)) == NWLN)    /* eat empty lines */
        ;
    if(tt != NAME || lex(tok) != NWLN)
        synerr( "Expecting definition for state." );
    while(nstates-- && dostate(tok, &inputs, &actions, &allinputs, defact))
        ;
    if(nstates >= 0)
        synerr( "Expecting more states." );
    else
        cout << "};\n";
    }


toktype lex(char *buf) {    /* return next lexical token    */
    char    c;

    while(cin.get(c))   /* while not EOF */
        if(c == ')' || c == '(' || c == ':' || c == '\n') {
            if(c == '\n')
                ++linumb;
            return( c );
            }
        else if(c == '\\') {    /* delete backslash newline */
            if(cin.get(c))
                if(c != '\n')
                    cin.putback(c);
                else
                    ++linumb;
            }
        else if(c == '/') {     /* eat comment  */
            while(cin >> c)
                if(c == '*' && (cin >> c) && c == '/')
                    break;
            }
        else if(isdigit(c)) {
            for(*buf++ = c; cin.get(c) && isdigit(c); *buf++ = c)
                ;
            *buf++  = '\0'; /* terminate the string */
            cin.putback(c); /* put back char that stopped scan */
            return NUMBER;
            }
        else if( isalpha(c) || c == '_' ) {
            for(*buf++ = c; cin.get(c) && (isalnum(c) || c=='_'); *buf++ = c)
                ;
            *buf++  = '\0'; /* terminate the string */
            cin.putback(c); /* put back char that stopped scan */
            return NAME;
            }
    return END;
    }

void    synerr(char * msg) {
    cerr << "Line " << linumb << ": " << msg << "\n";
    exit( EXIT_FAILURE );   /* defined in stdlib.h  */
    }

/*
 *  getinpact - read list of inputs and actions in the form:
 *      inp1 ... inpN : act1 ... actN
 */
void    getinpact(symtab *inp, symtab *act) {
    toktype getlist(symtab *table);

    if(getlist(inp) != COLON)
        synerr( "Expecting colon after list of inputs." );
    else if(getlist(act) != NWLN)
        synerr( "Expecting newline after list of actions." );
    }

toktype getlist(symtab *t) { /* read list of names   */
    toktype tt;

    for(t->n = 0; (tt=lex(t->table[t->n])) == NAME; ++t->n)
        ;
    return tt;
    }

void    doheader(char *matname, symtab *inp, symtab *act,
                char *defact, int nstates) {
    cout << "/* Define machine inputs */\n";
    for(int i = 0; i < inp->n; ++i)
        cout << "#define " << inp->table[i] << " " << i << "\n";
    cout << "/* Define machine actions */\n";
    for(i = 0; i < act->n; ++i)
        cout << "#define " << act->table[i] << " "<< i << "\n";
    cout << "#define " << defact << " " << i << "  /* default */\n";
    cout << "\n" << matname << "[" << nstates << "]["
            << inp->n << "] = {\n";
    }

int     dostate(char *buf, symtab *inp, symtab *act,
                    symtab *allinp, char *defact) {
    char    state[MAXSYM];
    toktype tt;
    static  symtab  temp;

    strcpy(state, buf); /* remember state   */
    for(int i=0; i < MAXSYMS; ++i)  /* init with default action */
        strcpy(temp.table[i], defact);
    for(int lines=0; ; ++lines) {
        tt  = getlist(inp);
        if(inp->n <= 0 || (tt == NWLN && inp->n == 1))
            break;
        if(((tt=getlist(act)) != NWLN && tt != END) || act->n <= 0)
            synerr( "Expecting list of inputs : action." );
        if(act->n > 1)
            synerr( "Can't have more than one action per input." );
        for(i=0; i < inp->n; ++i) {
            int j = allinp->find(inp->table[i]);
            if(strcmp(temp.table[j], defact))
                synerr( "Can't have more than one action per input." );
            else
                strcpy(temp.table[j], inp->table[i]);
            }
        }
    strcpy(buf, inp->table[0]); /* name of next state */
    if(!lines)
        return( 0 );
    cout << "/* State '" << state << "' */\n{ ";
    for(i = 0; i < allinp->n; ++i)
        cout << (i?", ":"") << temp.table[i];
    cout << " },\n";
    return( 1 );
    }