bianyi_c.rar_visual c_词法分析_词法分析器

#include <stdio.h> #include <ctype.h> #include <string.h> #define MAX 150 /*分析表的最大容量*/ #define MAXBUF 255 #define EOS '\0' #define format1 "%-20s\t%d\n" int k=1;/*(临时存放)当前符号表长度*/ char ch=' ';/*存放读入当前的输入字符*/ int line=1;/*程序行数*/ struct entry{ char lexptr[MAXBUF]; int token; };/*关键字表中的结构*/ struct entry symtable[MAX];/*符号表*/ char * str[] = {"DIM","IF","DO","STOP","END"}; /*初始化符号表*/ Initial() { int j; for(j=0; j<5; j++) { strcpy(symtable[j+1].lexptr,str[j]); symtable[j+1].token=j+1; k++; } } /* getbc()检查是否为空白,调用getchar直到进入非空 concat()将ch连接到strtoken */ int reserve(char *temp)/*查找保留字表,若是返回编码,否则返回0*/ { int j; for(j=1; j<k+1; j++) { if(!strcmp(symtable[j].lexptr,temp)) { return symtable[j].token; } } return(0); } /*retract()指示器返回1个字符*/ int insertid(char *temp)/*将strtoken中的标志符插入符号表,返回符号表指针*/ { strcpy(symtable[++k].lexptr,temp); symtable[k].token=6; } int insertconst(char *temp)/*将strtoken中的常数(整数)插入常数表,返回常数表指针*/ { strcpy(symtable[++k].lexptr,temp); symtable[k].token=7; } /* bool isletter(char ch) { return ((ch>='a'&&ch<='z')||(ch>'A'&&ch<'Z')); } bool IsDigit(char ch) { return (ch>='0'&&ch<='9'); }*/ void main() { FILE *in,*out; char strtoken[255];/*定义缓冲区*/ int i=0; char infile[20],outfile[20]; /*infile.txt是输入程序，结尾加 @ 易于判断*/ printf("please input the in filename(18)"); scanf("%s",infile); printf("please input the out filename(18)"); scanf("%s",outfile); if((in=fopen(infile,"r"))==NULL) { printf("can not open file\n"); exit(0); } if((out=fopen(outfile,"w"))==NULL) { printf("cannout open outfile\n"); exit(1);/*非正常终止程序*/ } Initial(); while((ch=fgetc(in))!=EOF)/*文件尾加@作判断用*/ { if(ch==' '||ch=='\t')/*去空格*/ { ; } else if(ch=='\n') { line++;/*记录行号，方便查找出错语句*/ } else if(isalpha(ch))/*判断标志符*/ {i=0; while(isalnum(ch)) { strtoken[i++]=ch; ch=fgetc(in); } strtoken[i++]=EOS; if (reserve(strtoken)) { fprintf(out,format1,strtoken,reserve(strtoken)); } else { insertid(strtoken); fprintf(out,format1,strtoken,6); } fseek(in,-1,1); } else if(isdigit(ch))/*判断数字*/ { i=0; while(isdigit(ch)) { strtoken[i++]=ch; ch=fgetc(in); } strtoken[i++]=EOS; if (reserve(strtoken)) { fprintf(out,format1,strtoken,reserve(strtoken)); } else { insertconst(strtoken); fprintf(out,format1,strtoken,7); } fseek(in,-1,1); } else if(ch=='*') { ch=fgetc(in); if(ch=='*') fprintf(out,format1,"**",11); else { fprintf(out,format1,"*",10); fseek(in,-1,1); } } else if(ch=='=')fprintf(out,format1,"=",8); else if(ch=='+')fprintf(out,format1,"+",9); else if(ch==',')fprintf(out,format1,",",12); else if(ch=='(')fprintf(out,format1,"(",13); else if(ch==')')fprintf(out,format1,")",14); else fprintf(out,"line:%d --> %c\n",line,ch); } fclose(in); fclose(out); exit(0); }