C转C++可能遇到的问题：
//1.一般情况
/* int i = 0; */
// 2.换行问题
/* int i = 0; */ int j = 0;
/* int i = 0; */
int j = 0;
// 3.匹配问题
/*int i = 0;/*xxxxx*/
// 4.多行注释问题
/*
int i=0;
int j = 0;
int k = 0;
*/int k = 0;
// 5.连续注释问题
/**//**/
// 6.连续的**/问题
/***/
// 7.C++注释问题
// /*xxxxxxxxxxxx*/
我们可以发现注释转换需要考虑的情况是非常多的，这对于我们写程序是非常不利的，为解决这类问题，我们引入有限状态机的概念。
有限状态机简称状态机，是表示有限个状态以及在这些状态之间转移的行为的 模型。有限状态机是闭环系统，可以用有限的状态处理无穷的状态。
通常我们使用switch case语句来处理有限状态机，
switch (state )
{
case 1:
// ...
break ;
case 2:
// ...
break ;
case 3:
// ...
break ;
.
.
case n :
break ;
default :
}
主要代码设计：
1，我们要声明一个枚举（enum）类型来存放四种状态
typedef enum CONVERT_STATE
{
NULL_STATE,
C_STATE,
CPP_STATE,
END_STATE,
}StateType;
定义全局变量state，初始状态为NULL_STATE.
2，声明一个打开input.c和output.c的函数
void CommentConvert()
{
FILE *pWrite=NULL ;
FILE *pRead = fopen("input.c" , "r");
if (pRead == NULL )
{
perror( "open file for read");
exit( EXIT_FAILURE);
}
pWrite = fopen( "output.c", "w" );
if (pWrite == NULL )
{
fclose(pRead);
perror( "open file for write");
exit( EXIT_FAILURE);
}
ConvertWork(pRead, pWrite);
fclose(pRead);
fclose(pWrite);
}
3，声明一个切换状态的函数
void ConvertWork(FILE *pRead, FILE *pWrite )
{
state = NULL_STATE;
while (state != END_STATE)
{
switch (state)
{
case NULL_STATE:
DoNullState( pRead, pWrite );
break;
case C_STATE:
DoCState( pRead, pWrite );
break;
case CPP_STATE:
DoCppState( pRead, pWrite );
break;
}
}
}
4,我们还要声明处理不同状态的函数
处理NULL_STATE的函数：
void DoNullState(FILE *read, FILE *write)
{
int first = fgetc(read );
int second = 0;
switch (first)
{
case ‘/‘ :
second = fgetc(read);
if (second == ‘*‘ )
{
fputc(first, write);
fputc( ‘/‘, write );
state = C_STATE;
}
else if (second == ‘/‘)
{
fputc(first, write);
fputc( ‘/‘, write );
state = CPP_STATE;
}
else
{
fputc(first, write);
fputc(second, write);
}
break;
case EOF :
fputc(first, write);
state = END_STATE;
break;
default:
fputc(first, write);
break;
}
}
处理C_STATE的的函数：
void DoCState(FILE *read, FILE *write)
{
int first = fgetc(read );
int second = 0;
switch (first)
{
case ‘/‘ :
second = fgetc( read);
if (second == ‘*‘ )
{
}
else if (second == ‘/‘)
{
}
else
{
fputc(first, write);
fputc(second, write);
}
break;
case ‘\n‘ :
fputc( ‘\n‘, write );
fputc( ‘/‘,write );
fputc( ‘/‘, write );
break;
case ‘*‘ :
second = fgetc( read);
if (second == ‘*‘ )
{
fputc(first, write);
first=fgetc( read);
if (first == ‘/‘ )
{
fputc( ‘\n‘, write );
state = NULL_STATE;
}
}
else if (second == ‘/‘)
{
fputc( ‘\n‘, write );
state = NULL_STATE;
}
else
{
fputc(first, write);
fputc(second, write);
}
break;
case EOF :
fputc(first, write);
state = END_STATE;
break;
default:
fputc(first, write);
break;
}
}
处理CPP_STATE的函数：
void DoCppState(FILE *read, FILE *write)
{
int first = fgetc(read );
int second = 0;
switch (first)
{
case ‘/‘ :
second = fgetc(read);
if (second == ‘*‘ )
{
}
else if (second == ‘/‘)
{
}
else
{
fputc(first, write);
fputc(second, write);
}
break;
case ‘\n‘ :
fputc(first, write);
state = NULL_STATE;
break;
case ‘*‘ :
second = fgetc(read);
if (second == ‘/‘ )
{
}
else
if (second == ‘*‘ )
{
fputc(first, write);
}
break;
case EOF :
fputc(first, write);
state = END_STATE;
break;
default:
fputc(first, write);
break;
}
}
如图：input.c
运行程序后打开output.c:
