we.cpp

关于汇编原理的代码。主要是扫描器的功能。有待改进。

#include   <stdio.h>   
  #include   <stdlib.h>   
  #include   <string.h>   
    
  #define   false   0   
  #define   true   1   
  #define   WORDLEN   20   
  /*单词编码表*/     
  const   char   *table[]   =   {"if","then","else","endif","while","do","enddo","var","int","real","void",   "+","-","*","/","%","++","--","=","<","<=",">","=","=","=","!","&","|",",",";","(",")","#"};   
    
  const   char   code[]   =   {"jtefwdrvacn+-*/%$@=<[>]^~!&|,;()#"};   
  /*DFA字符序列*/     
  char   COL_CHAR[]   =   "a0+-*/%=<>!&|,;()#";   
  /*状态转换矩阵   （DFA）   */   
  const   int   DFA[][19]   =   {   
              {1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,0},   
              {19,19},   
              {0,20},   
              {0,0,21},   
              {0,0,0,22},   
              {0},   
              {0},   
              {0},   
              {0,0,0,0,0,0,0,23},   
              {0,0,0,0,0,0,0,0,24},   
              {0,0,0,0,0,0,0,0,0,25},   
              {0,0,0,0,0,0,0,0,0,0,26},   
              {0},   
              {0},   
              {0},   
              {0},   
              {0},   
              {0},   
              {0},   
              {19,19},   
              {0,20},   
              {0},   
              {0},   
              {0},   
              {0},   
              {0},   
              {0}   
  };   
    
  struct   code_val{   
                char   code;   
                char   val[WORDLEN];   
  }   
    
  int   col(char);                                                                           /*列定位函数原型*/     
  void   concat(char[],char);                                     /*拼接函数原型*/     
  char   search_table(char[]);                               /*查单词二元式编码表函数原型*/     
  /*扫描器的控制程序*/     
  struct   code_val   scanner(char   *buf)             
  {   
                static   int   i   =   0;                                                           /*静态局部变量，扫描缓冲区指示器*/     
                struct   code_val   t   =   {'\0',"NUL"};   /*存放单词二元式，识别前清空*/     
                char   token[WORDLEN]   =   "";                 /*用于拼接单词，识别前清空*/     
                /*去除前导空格*/     
                while(buf[i]   ==   '   ')   i++;   
                /*从初态出发识别单词*/     
                int   cur_state   =   0;   
                while(DFA[cur_state][col(buf[i])])   {                                                                                     /*存在后继状态*/     
                                                                                      concat(token,buf[i]);                                                             /*拼接*/   
                                                                                      cur_state   =   DFA[cur_state][col(buf[i])];/*进入下一状态*/   
                                                                                      if(buf[++i]   ==   '\0')   break;                                           /*缓冲区内字符是否处理完*/   
                                                                                      }   
                t.code   =   search_table(token);                                                           /*查单词二元式*/   
                if(t.code   ==   '?')   {   
                                                    if(token[0]   >=   'a'   &&   token[0]   <=   'z')/*是标识符*/   
                                                                            t.code   =   'i';   
                                                    else                                                                                                       /*否则是整常数*/   
                                                                            t.code   =   'x';   
                                                    strcpy(t.val,token);   
                                                    }   
                return   t;                                                                                                                             /*返回当前单词的二元式*/   
  }   
  /*列定位函数*/   
  int   col(char   c)   
  {   
          int   i;   
          if(c   >=   'a'   &&   c   <=   'z')   c   =   'a';   
          if(c   >=   '0'   &&   c   <=   '9')   c   =   '0';   
          for(i   =   0;   i   <   strlen(COL_CHAR);   i++)   
          {                 
                          if(c   ==   COL_CHAR[i])   return   i;   
                          else   printf("Error   char   %c\n",   c);     
                                    exit(0);   
          }   
  }   
    
  char   search_table(char   token[])       /*根据token内容查单词二元式编码表，返回单词种别*/   
  {   
            int   i;   
            for(i   =   0;   i   <   strlen(code);   i++)   
                            if(strcmp(token,table[i])   ==   0)   return   code[i];   
                            else   return   '?';                                   /*'?'表示查表无果*/   
  }   
    
  void   concat(char   token[],   char   c)   
  {   
            int   i;   
            for(i   =   0;   token[i];   i++);                     /*找到尾*/     
                        token[i]   =   c;   
                        token[++i]   =   '\0';   
  }   
  /*预处理程序*/   
  void   call(char   *buf)   
  {   
            int   i   =   0;             /*计数器*/     
              
            FILE   *fp;   
            if((fp   =   fopen("source.txt","r"))   ==   NULL)   
            {   
                        printf("Can't   open   the   file.\n");   
                        exit(0);   
            }   
            char   old_c   =   '\0',cur_c;                                 /*前一个字符，当前字符*/   
            int   in_comment   =   false;                             /*false表示当前字符未处于注释中*/   
            while((cur_c   =   getc(fp))   !=   EOF)   
            {   
                    switch(in_comment)   
                    {   
                    case   false:   
                              if(old_c   ==   '/'   &&   cur_c   ==   '*')                   /*进入注释*/   
                              {   
                                                i--;                                                                                     /*去除已存入扫描缓冲区的字符'/'*/   
                                                in_comment   =   true;   
                              }   
                              else   
                              {   
                                      if(old_c   ==   '\\'   &&   cur_c   ==   '\n')         /*发现续行*/     
                                                        i--;                                                                               /*去除已存入扫描缓冲区的字符'\'*/   
                                      else   
                                      {   
                                              if(cur_c   >=   'A'   &&   cur_c   <=   'Z')     /*大写变小写*/   
                                                                cur_c   +=   32;   
                                              if(cur_c   ==   '\t'   ||   cur_c   ==   '\n')     /*空格取代Tab换行*/   
                                                                cur_c   =   '   ';   
                                              buf[i++]   =   cur_c;   
                                      }   
                              }   
                              break;   
                    case   true:   
                              if(old_c   ==   '*'   &&   cur_c   ==   '/')                         /*离开注释*/   
                                                in_comment   =   false;   
                    }   
                    old_c   =   cur_c;                                                                                   /*在源程序尾部添加字符'#'*/   
            }   
            buf[i++]   =   '#';   
            fclose(fp);   
  }   
    
  int   main()   
  {   
            int   i;   
            char   buf[4048]   =   {'\0'};                                   /*扫描缓冲区*/   
            call(buf);                                                                                   /*预处理*/   
            FILE   *fp;   
            if((fp   =   fopen("Lex_r.txt","w"))   ==   NULL)   
            {   
                          printf("Can't   open   the   file.\n");   
                          exit(0);   
            }   
            struct   code_val   t;   
            do   {   
                    t   =   scanner(buf);   
                    putc(t.code,fp);   
                    putc('\n',fp);   
                    }while(t.code   !=   '#');   
            printf("End   of   lexicalanalysis!\n");   
            fclose(fp);   
  }