“单词”分类说明
标识符(Identifier):变量名和函数名(字母或下划线开头)；
关键字(Keyword):系统保留字；
运算符(Operator): + - * / % = == != < <= > >= 等；
分隔符(Separator): , ; . ' " ( ) [ ] { } // /* */ #等；
常量(Constant): 字符串或字符常量；
注释(Note): 注释不参与编译。
程序清单：
/*
========================================================
词法分析器V1.0
(DFA，C语言描述，可分析C/C++词法)
Author:Estrong
2012.05.10
========================================================
*/
/*
说明：
标识符(Identifier):变量名和函数名(字母或下划线开头)；
关键字(Keyword):具有特定的功能系统保留字，不能移作他用；
运算符(Operator): + - * / % = == != < <= > >= 等；
分隔符(Separator): , ; . ' " ( ) [ ] { } // /米 米/ #等；
常量(Constant):字符串或字符常量；
注释(Note): 注释不参与编译。
*/
#include "stdio.h"
#include "string.h"
#define MAX_STR 256
#define MAX_KEYWORDS 62
#define MAX_OPERATORS 12
#define MAX_SEPARATORS 15
/* 定义分析状态 */
#define STA_START 1
#define STA_IDorKEYWORD 2 /* IDENTIFIER： 标识符 */
#define STA_NUMBER 3 /* NUMBER： 数字 */
#define STA_NOTE 4 /* NOTE: 注释 */
#define STA_CONSTANT 5 /* CONSTANT: 常量 */
#define STA_DONE 6 /* DONE： 完成 */
/* 定义所属类型 */
#define TYPE_KEYWORD 1 /* KEYWORD： 保留字 */
#define TYPE_IDENTIFIER 2 /* IDENTIFIER： 标识符 */
#define TYPE_NUMBER 3 /* NUMBER： 数字 */
#define TYPE_NOTE 4 /* NOTE: 注释 */
#define TYPE_CONSTANT 5 /* CONSTANT: 常量 */
#define TYPE_OPERATOR 6 /* OPERATOR: 运算符 */
#define TYPE_SEPARATOR 7 /* SEPARATOR: 分隔符 */
#define TYPE_ERROR 8 /* ERROR: 错误 */
#define TYPE_UNKNOWN 9 /* UNKNOWN: 未知 */
#define TYPE_ENDFILE 10 /* ENDFILE: 文件结束 */
char *Operators[MAX_OPERATORS] = {"+","-","*","/","%","=","==","!=","<","<=",">",">="};
char *Separators[MAX_SEPARATORS] ={",",";",".","'",""","(",")","[","]","{","}","//","/*","*/","#"};
char *Keywords[MAX_KEYWORDS] = {"include","define","auto","bool","break","case","catch","char","class",
"const","const_cast","continue","default","delete","do","double",
"dynamic_cast","else","enum","explicit","extern","false","float","for",
"friend","goto","if","inline","int","long","mutable","namespace","new",
"operator","private","protected","public","register","reinterpret_cast",
"return","short","signed","sizeof","static","static_cast","struct",
"switch","template","this","throw","true","try","typedef","typeid",
"typename","union","unsigned","using","virtual","void","volatile","while"};
/* 是否为运算符 */
int IsOperator(char c)
{
int i;
for(i=0;i<MAX_OPERATORS;i++)
if(Operators[i][0]==c)
return 1;
return 0;
}
/* 是否为分隔符 */
int IsSeparator(char c)
{
int i;
for(i=0;i<MAX_SEPARATORS;i++)
if(Separators[i][0]==c)
return 1;
return 0;
}
/* 是否为保留字 */
int IsKeyword(char *str)
{
int i;
for(i=0;i<MAX_KEYWORDS;i++)
if(strcmp(Keywords[i],str)==0)
return 1;
return 0;
}
/* DONE一次输出一次 */
void OutputOneDone(FILE *outf,int type,char *str)
{
if(IsKeyword(str)==1) type=TYPE_KEYWORD;
switch(type)
{
case TYPE_KEYWORD: fprintf(outf," KEYWORD: ");break;
case TYPE_IDENTIFIER: fprintf(outf," IDENTIFIER: ");break;
case TYPE_NUMBER: fprintf(outf," NUMBER: ");break;
case TYPE_NOTE: fprintf(outf," NOTE: ");break;
case TYPE_CONSTANT: fprintf(outf," CONSTANT: ");break;
case TYPE_OPERATOR: fprintf(outf," OPERATOR: ");break;
case TYPE_SEPARATOR: fprintf(outf," SEPARATOR: ");break;
case TYPE_ERROR: fprintf(outf," ERROR: ");break;
case TYPE_UNKNOWN: fprintf(outf," UNKNOWN: ");break;
default:break;
}
fprintf(outf,"%sn",str);
}
/* DFA词法分析函数 */
void LexAnalyse(FILE *inf,FILE *outf)
{
char c;
char str[MAX_STR];/* 过程字符串 */
int i;
int line_no=1;/* 行号 */
int state,type;
char flag_limit_one_line;/* 标志为 / * 注释 范围是一行 */
char flag_had_got_dot;/* 用于限定小数中只能有一个小数点 */
fprintf(outf,"Line %d--------------------------------------n",line_no);
while(!feof(inf))
{
i=0;
state=STA_START;
flag_limit_one_line=0;
flag_had_got_dot=0;
while(state!=STA_DONE)
{
c=fgetc(inf);
switch(state)
{
case STA_START:
if( c==' ' || c=='t');
else if(c=='n')
{
line_no++;
fprintf(outf,"Line %d--------------------------------------n",line_no);
}
else if( (c>='a' && c<='z') || (c>='A' && c<='Z') || c=='_')
{
state=STA_IDorKEYWORD;
type=TYPE_IDENTIFIER;
str[i]=c; i++;
}
else if(c>='0' && c<='9')
{
state=STA_NUMBER;
type=TYPE_NUMBER;
str[i]=c; i++;
}
else if(c=='/')
{
str[i]=c; i++;
c=fgetc(inf);
if(c=='/') /* //注释 */
{
flag_limit_one_line=1;
state=STA_NOTE;
type=TYPE_NOTE;
str[i]=c; i++;
}
else if(c=='*') /* / * 注释开始 */
{
state=STA_NOTE;
type=TYPE_NOTE;
str[i]=c; i++;
}
else
{
state=STA_DONE;
type=TYPE_OPERATOR;
fseek(inf, -1, SEEK_CUR);/* 文件流指针前移1个字节 */
i=1;/* str[1]=' '; */
}
}
else if(c=='<' || c=='>')
{
state=STA_DONE;
type=TYPE_OPERATOR;
str[0]=c;
c=fgetc(inf);
if(c=='=')
{
str[1]='=';i=2;/* str[2]=' ' */
}
else/* 暂未考虑<<,>>位移运算符的识别 */
{
fseek(inf, -1, SEEK_CUR);/* 文件流指针前移1个字节 */
i=1;/* str[1]=' '; */
}
}
else if(c=='!')
{
state=STA_DONE;
str[0]=c;
c=fgetc(inf);
if(c=='=') /* 是!= */
{
type=TYPE_OPERATOR;
str[1]='=';i=2;/* str[2]=' ' */
}
else /* 非!= */
{
type=TYPE_UNKNOWN;
fseek(inf, -1, SEEK_CUR);/* 文件流指针前移1个字节 */
i=1;/* str[1]=' '; */
}
}
else if(c=='"' || c==''')
{
state=STA_CONSTANT;
type=TYPE_CONSTANT;
str[0]=c; i=1;
}
else if(IsOperator(c))
{
state=STA_DONE;
type=TYPE_OPERATOR;
str[0]=c; i=1;/* str[1]=' '; */
}
else if(IsSeparator(c))
{
state=STA_DONE;
type=TYPE_SEPARATOR;
str[0]=c; i=1;/* str[1]=' '; */
}
else if(c==EOF)
{
state=STA_DONE;
type=TYPE_ENDFILE;
}
else
{
state=STA_DONE;
type=TYPE_UNKNOWN;
}
break;/* case STA */
case STA_IDorKEYWORD:
if((c>='a' && c<='z') || (c>='A' && c<='Z') || (c>='0' && c<='9') || c=='_' )
{
str[i]=c; i++;
}
else if(c=='.')
{
str[i]=c; i++;
c=fgetc(inf);
if((c>='a' && c<='z') || (c>='A' && c<='Z') || c=='_')
{
str[i]=c; i++;
/* type=TYPE_IDENTIFIER; */
}
else if(c==' ' || c=='t' || c=='n' || IsOperator(c) || IsSeparator(c))
{
fseek(inf, -1, SEEK_CUR);/* 文件流指针前移1个字节 */
state=STA_DONE;
type=TYPE_ERROR; /* 如 date. 或 date.1 标记为ERROR类型 */
}
else
{
str[i]=c; i++;
type=TYPE_ERROR;
}
}
else if(c==' ' || c=='t' || c=='n' || IsOperator(c) || IsSeparator(c))
{
state=STA_DONE;
fseek(inf, -1, SEEK_CUR);/* 文件流指针前移1个字节 */
}
else
{
state=STA_DONE;
type=TYPE_ERROR;
}
break;/* case STA */
case STA_NUMBER:
if(c>='0' && c<='9')
{
str[i]=c; i++;
}
else if(c=='.') /* 小数识别 */
{
str[i]=c; i++;
c=fgetc(inf);
if(flag_had_got_dot==0)
{
if(c>='0' && c<='9')
{
str[i]=c; i++;
/* type=TYPE_NUMBER; */
flag_had_got_dot=1;
}
else /* if(c==' ' || c=='t' || c=='n' || c>='0' && c<='9' || ...) */
{
fseek(inf, -1, SEEK_CUR);/* 文件流指针前移1个字节 */
state=STA_DONE;
type=TYPE_ERROR; /* 如 date. 或 date.1 标记为ERROR类型 */
}
}
else
{
type=TYPE_ERROR;
str[i]=c; i++;
}
}
else if(c==' ' || c=='t' || c=='n' || IsOperator(c) || IsSeparator(c))
{
state=STA_DONE;
fseek(inf, -1, SEEK_CUR);/* 文件流指针前移1个字节 */
}
else
{
str[i]=c; i++;
type=TYPE_ERROR;
}
break;/* case STA */
case STA_NOTE:
if(flag_limit_one_line==1) /* 是/ * 注释, 限定一行 */
{
if(c=='n')
{
state=STA_DONE;
fseek(inf, -1, SEEK_CUR);/* 文件流指针前移1个字节 */
}
else
{
str[i]=c; i++;
}
}
else /* 是 / * 注释 */
{
if(feof(inf))
{
state=STA_DONE;
type=TYPE_ERROR;
}
else if(c=='n')
{
line_no++;
str[i]=c; i++;
}
else if(c=='*')
{
str[i]=c; i++;
c=fgetc(inf);
if(c=='/')
{
state=STA_DONE;
str[i]=c; i++;
}
else
{
if(feof(inf))
{
state=STA_DONE;
type=TYPE_ERROR;
}
fseek(inf, -1, SEEK_CUR);/* 文件流指针前移1个字节 */
}
}
else
{
str[i]=c; i++;
}
}
break;/* case STA */
case STA_CONSTANT:
if(feof(inf))
{
state=STA_DONE;
type=TYPE_ERROR;
}
else if(c=='n')
{
line_no++;
str[i]=c; i++;
}
else if(c=='"' || c==''')
{
state=STA_DONE;
str[i]=c; i++;
}
else if(c=='\')
{
str[i]=c; i++;
c=fgetc(inf);
str[i]=c; i++;
}
else
{
str[i]=c; i++;
}
break;/* case STA */
case STA_DONE: break;/* case STA */
default: break;/* case STA */
}
}/* state=STA_DONE */
str[i]=' ';
OutputOneDone(outf,type,str);/* DONE一次输出一次 */
}/* feof(inf) */
}
/* 主函数 */
main()
{
FILE *input,*output;
if((input=fopen("input.c","r"))==NULL)
{
printf("Cannot find the file!nStrike any key to exit!n");
system("pause");
exit(1);
}
else
{
output=fopen("output.c","w");
LexAnalyse(input,output);
fprintf(output,"----------------------------------------------END OF FILE!n");
fclose(input);
fclose(output);
printf("Lexical Analyzer has finished the analyzation!nFor more information please see the file output.txt.n");
system("pause");
}
}
原文链接: https://www.cnblogs.com/Estrong/archive/2012/11/05/2744548.html
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