symbol.c

语法分析程序,使用是递归子程序法.自己写的程序,学习

/*
 * Author: zhangdi
 * Date: 2008-11-10
 * Description: symbol table, it has it's method to insert a symbol
 * and method to lookup a symbol, it also has a method to distinguish if the
 * identifier is a key word
 */
#include <string.h>
#include "global.h"
#include "error.h"

char lexemex[STRMAX];               /* array to store  */
int lastchar = -1;                  /* memorize the last char of array store */
struct entry symtable[ARRAYMAX];    /* symtable array */
int lastentry = 0;                  /* memorize the last entry of symtable */

/* look up if a identifier is in the symbol table */
int lookup(char str[])
{
    int position;
    for (position = lastentry; position > 0; position = position -1)
    {
        if (strcmp(symtable[position].lexptr, str) == 0)
            return position;
    }

    return 0;
}

/* insert identifier to symbol table */
int insert(char str[], int tok)
{
    int length;
    length = strlen(str);
    if (lastentry + 1 >= ARRAYMAX)
        error("symbol table full");
    if (lastchar + length + 1 >= STRMAX)
        error("lexemes array for symbol full");
    /* modify the last entry of symtable */
    lastentry += 1;
    symtable[lastentry].token = tok;
    symtable[lastentry].lexptr = &lexemex[lastchar + 1];
    /* modify the last char of store array */
    lastchar = lastchar + length + 1;
    strcpy(symtable[lastentry].lexptr, str);
    return lastentry;
}

/* distinguish a identifier is a symbol */
int searchkeyword(char key[])
{
    int position;
    for (position = 0; position < keynum; position++)
    {
        if (strcmp(keywords[position].lexptr, key) == 0)
            return position;
    }
    return -1;
}

/* output symtable to a txt file */
int symtabledisplay()
{
    int i;
    FILE * fwp;

    if ((fwp = fopen("symtable.txt", "wt")) == NULL)
    {
        fprintf(stderr, "can't create symtable.txt");
        exit(-1);
    }

    for (i=1; i <= lastentry; i++)
    {
        switch(symtable[i].token)
        {
            case IF:
                fprintf(fwp, "%s\tif\n", symtable[i].lexptr);
                break;
            case ELSE:
                fprintf(fwp, "%s\telse\n", symtable[i].lexptr);
                break;
            case WHILE:
                fprintf(fwp, "%s\twhile\n", symtable[i].lexptr);
                break;
            case INT:
                fprintf(fwp, "%s\tint\n", symtable[i].lexptr);
                break;
            case ID:
                fprintf(fwp, "%s\tid\n", symtable[i].lexptr);
                break;
            case FLOAT:
                fprintf(fwp, "%s\tfloat\n", symtable[i].lexptr);
                break;
            case NUM:
                fprintf(fwp, "%s\tnum\n", symtable[i].lexptr);
                break;
            case FNUM:
                fprintf(fwp, "%s\tfnum\n", symtable[i].lexptr);
                break;
            case RELOP:
                fprintf(fwp, "%s\trelop\n", symtable[i].lexptr);
                break;
            case ADDOP:
                fprintf(fwp, "%s\taddop\n", symtable[i].lexptr);
                break;
            case MULOP:
                fprintf(fwp, "%s\tmulop\n", symtable[i].lexptr);
                break;
            default:
                fprintf(fwp, "%s\t%c\n", symtable[i].lexptr, symtable[i].token);
                break;
        }
    }

    fclose(fwp);
    return 0;
}