C语言简单实现：将C注释转化为C++注释

                       C语言简单实现：将C注释转化为C++注释

我们首先考虑一下都会出现什么情况：

总结下来就是如下图：

因此我们需要封装三个函数。

测试部分(test.c)如下：

#include"CommentConvert.h"

void test()
{
  enum STATE state = NUL_STATE;
  FILE *pfIn;
  pfIn = fopen("input.c", "r");
  if (pfIn == NULL)
  {
    perror("open file for read\n");
    exit(EXIT_FAILURE);
  }
  FILE *pfOut;
  pfOut = fopen("output.c", "w");
  if (pfOut == NULL)
  {
    perror("close file for write\n");
    fclose(pfIn);
    exit(EXIT_FAILURE);
  }

  while (state != END_STATE)
  {
    switch (state)
    {
    case NUL_STATE:
      DoNulState(pfIn, pfOut, &state);
      break;
    case C_STATE:
      DoCState(pfIn, pfOut, &state);
      break;
    case CPP_STATE:
      DoCppState(pfIn, pfOut, &state);
      break;
    }
  }
  fclose(pfIn);
  fclose(pfOut);
}

int main()
{
  test();
  system("pause");
  return 0;
}

CommentConvert.h如下：

#ifndef __COMMENT_CONVERT_H__
#define __COMMENT_CONVERT_H__

#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
#include <stdlib.h>

enum STATE
{
  END_STATE,
  NUL_STATE,
  C_STATE,
  CPP_STATE
};

void DoNulState(FILE*pfIn, FILE*pfOut, enum STATE* s); 

void DoCState(FILE*pfIn, FILE*pfOut, enum STATE* s);

void DoCppState(FILE*pfIn, FILE*pfOut, enum STATE* s);

#endif //__COMMENT_CONVERT_H__

CommentConvert.c如下：

#include"CommentConvert.h"

void DoNulState(FILE*pfIn, FILE*pfOut, enum STATE* s)
{
    int first = fgetc(pfIn);
    switch (first)
    {
    case '/':
    {
                int second = fgetc(pfIn);
                switch (second)
                {                                
                case '*':
                    fputc('/', pfOut);               //遇到'/*'转化为'//',进入C状态
                    fputc('/', pfOut);
                    *s = C_STATE;
                    break;
                case '/':                         //遇到'//'，进入C++状态，直接输出
                    fputc(first, pfOut);
                    fputc(second, pfOut);
                    *s = CPP_STATE;
                    break;
                default:                          //遇到'/'又遇到文本，内容直接输出 
                    fputc(first, pfOut);
                    fputc(second, pfOut);
                    break;
                }
                break;
    }
    case EOF:                        //文档结束
        *s = END_STATE;
        break;
    default:                       //文本内容
        fputc(first, pfOut);
        break;
    }
}

void DoCState(FILE *pfIn, FILE *pfOut, enum STATE* s)          //C状态的处理
{
    int first = fgetc(pfIn);
    switch (first)
    {
    case '*':
    {   int second = 0;
        second = fgetc(pfIn);

        if (second == '/')                          //遇到'*/',C注释结束
        {
            int third = 0;
            third = fgetc(pfIn);

            //注释结束判断是否换行，如果不是'\n'，说明在second之后还有字符，因此需要换行
            if (third != '\n')                    
            {
                fputc('\n', pfOut);               //换行
                ungetc(third, pfIn);              //将读到的字符还给文档
                *s = NUL_STATE;
            }
            else
           {
                fputc(third, pfOut);
                *s = NUL_STATE;
            }
        }

        else if (second == '*')                  //处理连续的**/问题
        {
            char third = fgetc(pfIn);
            if (third == '/')
            {
                fputc(first, pfOut);            //最后一个*与/结合注释结束
                *s = NUL_STATE;
            }
            else                                
           {
                fputc(first, pfOut);
                fputc(second, pfOut);
            }
        }
        else                                    //处理*后是文本的情况
        {
            fputc(first, pfOut);
            fputc(second, pfOut);
        }
       break;
    }
    //如果'/*'后换行，转成C++必须换行后每行都加上注释
    case '\n':                              
        fputc(first, pfOut);
        fputc('/',pfOut);
        fputc('/', pfOut);
        break;
    case EOF:
        *s = END_STATE;
        break;
    default:
        fputc(first, pfOut);
        break;
    }
}

void DoCppState(FILE*pfIn, FILE*pfOut, enum STATE* s)         //C++状态处理
{
    int ch = fgetc(pfIn);
    switch (ch)
    {
    case '\n':
        fputc(ch, pfOut);
        *s = NUL_STATE;
        break;
    case EOF:
        *s = END_STATE;
        break;
    default:
        fputc(ch, pfOut);
        break;
    }
}