main.c

参照清华大学《编译原理》写的cmm语言词法分析程序

/*编译和运行环境
 * gcc4.3.2
 * Archlinux-2.6.26
 * 使用方法
 * 命令行输入 gcc main.c && ./a.out Test.cmm
 */
#include "cmm.h"

int main (int argc, char * argv[]) {
      bool nxtlev[symnum];
      fname = argv[1];
      fin = fopen(fname,"r");		/* 只读打开文件 */
      if (fin) {
            init();
            getsymdo;
            program(0);
      }
      else{
            printf("Can't open file! \n");
      }
      return 0;
}

void init() {
      int i;
      /* 初始化单字符的Token值 */
      for (i = 0; i <= 255; i++) {
            ssym[i] = nul;
      }
      ssym['+'] = plus;
      ssym['-'] = minus;
      ssym['*'] = times;
      ssym['/'] = slash;
      ssym['('] = lparen;
      ssym[')'] = rparen;
      ssym['['] = lbracket;
      ssym[']'] = rbracket;
      ssym['{'] = lbrace;
      ssym['}'] = rbrace;
      ssym['='] = assign;
      ssym[','] = comma;
      ssym['.'] = period;
      ssym[';'] = semicolon;

      /* 设置保留字的名字,按照字母顺序，便于折半查找 */
      strcpy(&(word[0][0]), "const");
      strcpy(&(word[1][0]), "else");
      strcpy(&(word[2][0]), "if");
      strcpy(&(word[3][0]), "int");
      strcpy(&(word[4][0]), "read");
      strcpy(&(word[5][0]), "real");
      strcpy(&(word[6][0]), "while");
      strcpy(&(word[7][0]), "write");

      /* 设置保留字对应的symbol */
      wsym[0] = constsym;
      wsym[1] = elsesym;
      wsym[2] = ifsym;
      wsym[3] = intsym;
      wsym[4] = readsym;
      wsym[5] =  realsym;
      wsym[6] =  whilesym;
      wsym[7] =  writesym;
}

/*
 * 漏掉空格,读取一个字符
 * 每次读一行,存入line缓冲区,line被getsym取空后再读一行
 * 被函数getsym调用
 */
int getch() {
      if ( cc == ll ) {		/* cc == ll说明当前行已经分析完成，或者开始分析第一行 */
            if ( feof(fin) ) {	/* 文件结束 */
                  printf("program incomplete");
                  return -1;
            }
            ll = 0;
            cc = 0;
            ch = ' ';
            /* 清空上一行余留的字符 */		
            memset(line,0,sizeof(line));
            while (ch != 10) {	/* 碰到换行符停止循环 */
                  if (EOF == fscanf(fin,"%c",&ch)) {		/* 文件结束 */
                        return -1;
                  }
                  line[ll] = ch;
                  ll++;
            }
            linenum++;
            //          printline();
      }
      ch = line[cc];
      cc++;
      return 0;
}

/* 词法分析，获取下一个Token */
int getsym() {
      int i, j, k;
      while ( ch == 0 || ch == ' ' || ch == 10 || ch == 9) {		/* 忽略空格，换行符和TAB */
            getchdo;		/* 忽略后获取下个字符 */
      }
      if (ch >= 'a' && ch <= 'z') {			/* 检测标识符和关键字 */
            k = 0;
            do {
                  if (k < al) {
                        a[k] = ch;
                        k++;
                  }
                  getchdo;
            }while (ch >= 'a' && ch <= 'z' || ch >= '0' && ch <= '9');
            a[k] = 0;
            strcpy(id,a);
            strcpy(value,a);
            i = 0;
            j = norw - 1;
            while (i <= j) {
                  k = (i+j)/2;
                  if (strcmp(id,word[k]) < 0) {		/* word[k] 表示 word[k][0]的地址 */
                        j = k-1;
                  }
                  else if (strcmp(id,word[k]) > 0) {
                        i = k+1;
                  }
                  else {
                        break;
                  }
            }
            if (i > j) {
                  sym = ident;		/* 设置当前符号为ident */
            }
            else {
                  sym = wsym[k];		/* 设置当前符号为某保留字的symbol */
            }
      }
      else {
            if (ch >= '0' && ch <= '9') {		/* 检测数字 */
                  k = 0;					/* 当前number的位数 */
                  num = 0;
                  sym = number;
                  do {					/* 继续检查后面的数字 */
                        if (ch == '.') {	/* 处理小数部分 */
                              sym = real;
                              realvalue = num;
                              e = 0.1;
                              k++;
                              getchdo;
                              while (ch >= '0' && ch <= '9') {
                                    int ich = ch-'0';
                                    realvalue += e*ich;
                                    e*=0.1;
                                    getchdo;
                              }
                        }
                        else {			/* 处理整数部分 */
                              num=10*num+ch-'0';
                              k++;
                              getchdo;
                        }
                  } while(ch >= '0' && ch <= '9' || ch == '.');
                  k--;
                  if( k > nmax){
                        printf("number too long!\n");
                        exit(0);
                  }
            }
            else {
                  if (ch == '=') {		/* 检测赋值符号和等于号 */
                        getchdo;
                        if (ch == '=') {
                              sym = eql;
                              getchdo;
                        }
                        else {
                              sym = assign;
                        }
                  }
                  else {
                        if (ch == '<') {	/* 检测小于号和小于等于号*/
                              getchdo;
                              if (ch == '=') {
                                    sym = leq;
                                    getchdo;
                              }
                              else {
                                    sym = lss;
                              }
                        }
                        else {
                              if (ch == '>') {	/* 检测大于号和大于等于号*/
                                    getchdo;
                                    if (ch == '=') {
                                          sym = geq;
                                          getchdo;
                                    }
                                    else {
                                          sym = gtr;
                                    }
                              }
                              else {
                                    if (ch == '!') {		/* 检测不等号 */
                                          getchdo;
                                          if (ch == '=') {
                                                sym = neq;
                                                getchdo;
                                          }
                                          else {
                                                sym = ssym['!'];
                                          }
                                    }
                                    else {		/* 当前符号不满足上述条件时,全部按照单字符号处理 */
                                          sym = ssym[ch];
                                          getchdo;
                                    }
                              }
                        }
                  }
            }
      }
      return 0;	
}
/** 
 * @brief  打印当前Token的值
 * 
 * @param offset 偏移量 
 * 
 * @returns void
 */
void printsym (int offset) {
      int i;
      if (sym != 0) {
            for (i = 0; i< offset; i++) {
                  printf(" ");
            }
            switch (sym) {
                  case ident : 
                        printf("identifier : %s\n",value);break;
                  case number : 
                        printf("number : %d\n",num);break;
                  case real : 
                        printf("real : %f\n",realvalue);break;
                  case plus : 
                        printf("plus : +\n");break;
                  case minus : 
                        printf("minus : -\n");break;
                  case times : 
                        printf("times : *\n");break;
                  case slash : 
                        printf("slash : /\n");break;
                  case eql : 
                        printf("equal : ==\n");break;
                  case neq : 
                        printf("not equal : !=\n");break;
                  case lss : 
                        printf("less than : <\n");break;
                  case leq : 
                        printf("less equal : <=\n");break;
                  case gtr : 
                        printf("greater than : >=\n");break;
                  case geq : 
                        printf("greater equal : >=\n");break;
                  case lparen : 
                        printf("lparen : (\n");break;
                  case assign : 
                        printf("assign : =\n");break;
                  case rparen : 
                        printf("rparen : )\n");break;
                  case lbracket : 
                        printf("lbracket : [\n");break;
                  case rbracket : 
                        printf("rbracket : ]\n");break;
                  case lbrace : 
                        printf("lbrace : {\n");break;
                  case rbrace : 
                        printf("rbrace : }\n");break;
                  case comma : 
                        printf("comma : ,\n");break;
                  case semicolon : 
                        printf("semicolon : ;\n");break;
                  case period : 
                        printf("period : .\n");break;
                  case constsym : 
                        printf("keyword : const\n");break;
                  case elsesym : 
                        printf("keyword : else\n");break;
                  case ifsym : 
                        printf("keyword : if\n");break;
                  case intsym : 
                        printf("keyword : int\n");break;
                  case readsym : 
                        printf("keyword : read\n");break;
                  case realsym : 
                        printf("keyword : real\n");break;
                  case whilesym : 
                        printf("keyword : while\n");break;
                  case writesym : 
                        printf("keyword : write\n");break;	
            }
      }
}

/* 打印当前行 */
void printline () {
      int i;
      printf(" %d: ",linenum);
      for (i = 0; i < sizeof(line); i++) {
            if (line[i] != 32 && line[i] != 10 && line[i] != 9) {
                  break;
            }
      }
      for (i;i < sizeof(line) && line[i] != '\n'; i++) {
            printf("%c",line[i]);
      }
      printf("\n");
}

int program(int lev) { 
      bool nxtlev[symnum]; 
      printspace(lev);
      printf("Program-->\n");
      while(sym == constsym) {
            constdeclaration(lev+iden);
      }
      while (sym == intsym || sym == realsym) {
            vardeclaration(lev+iden);
      }
      while (sym == ident || sym == ifsym || sym == whilesym || sym == readsym) {
            statement(lev+iden);
      }
}

int statement(int lev) {
      printspace(lev);
      switch (sym) {
            case ident:
                  printf("AssignStatement-->\n");
                  printspace(lev+iden);
                  printf("identifier:%s\n",id);
                  getsymdo;
                  while (sym == lbrace) {
                        printspace(lev+iden);
                        printf("lbracket:[\n");
                        getsymdo;
                        expression(lev+iden);
                        if (sym == rbrace) {
                              printspace(lev+iden);
                              printf("rbracket:]\n");
                              getsymdo;
                        }
                  }
                  if (sym == assign) {
                        printspace(lev+iden);
                        printspace(lev+iden);
                        printf("assign operator:=\n");
                        getsymdo;
                        expression(lev+iden);
                        if (sym == semicolon) {
                              printspace(lev+iden);
                              printf("semicolon:;\n");
                              getsymdo;
                        }
                  }
                  break;