注释转换(C到C++)

7种转换情况

1.一般情况

/*int i = 0;*/

2.换行问题

/*int i = 0;*/int j = 0;
/*int i = 0*/

3.匹配问题

/*int i = 0;/* int j = 0;*/

4.多行注释问题

/*
int i = 0
int j = 0
*/int k = 0;

5.连续注释问题

/*int i = 0;*//*int j = 0;*/

6.连续的**/问题

/*int i = 0;**/

7.C++注释问题

// /* int i = 0;*/

分析

我们可以看到注释转换需要考虑的情况非常多的,这对于我们写程序是非常不利的，为了解决这个问题 我们引入了有限状态机的概念，
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。有限状态是闭环系统,可以用有限的状态处理无穷的状态

由此引入下面这张图

代码实现

Convert.h

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<assert.h>
#include<stdlib.h>
typedef enum CONVERT_STATE
{
    NORMAL_STATUS,
    C_STATUS,
    CPP_STATUS,
    END_STATUS,
}StateType;

void convertBegin();
void convertStatusMachine(FILE *in, FILE *out);
void doCPPStatus(FILE *in, FILE *out);
void doCStatus(FILE *in, FILE *out);
void doNormal(FILE *in, FILE *out);

Convert.c

#include"Convert.h"


//1，我们要声明一个枚举（enum）类型来存放四种状态
//定义全局变量state，初始状态为NULL_STATE.
StateType gStatus = NORMAL_STATUS;


//2，声明一个打开input.c和output.c的函数
void convertBegin()
{
    FILE *in = fopen("input.c", "r");
    if (NULL == in)
    {
        perror("fopen");
        exit(1);
    }
    FILE *out = fopen("output.c", "w");

    if (NULL == out)
    {
        perror("fopen");
        exit(2);
    }
    convertStatusMachine(in, out);
    fclose(in);
    fclose(out);
}
//3，声明一个切换状态的函数
void convertStatusMachine(FILE *in, FILE *out)
{
    assert(in);
    assert(out);
    while (gStatus != END_STATUS)
    {
        switch (gStatus)
        {
        case NORMAL_STATUS:
            doNormal(in, out);
            break;
        case C_STATUS:
            doCStatus(in, out);
            break;
        case CPP_STATUS:
            doCPPStatus(in, out);
            break;
        case END_STATUS:
            break;
        default:
            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 doNormal(FILE *in, FILE *out)
{
    int first = fgetc(in);
    int second = 0;
    assert(in);
    assert(out);
    switch (first)
    {
        case '/':
        {
            second = fgetc(in);
            if (second == '*')
            {
                fputc('/', out);
                fputc('/', out);
                gStatus = C_STATUS;
            }
            else if (second == '/')
            {
                fputc(first, out);
                fputc(second, out);
                gStatus = CPP_STATUS;
            }
            else
            {
                fputc(first, out);
                fputc(second, out);
            }
        }
        break;
        case EOF:
            gStatus = END_STATUS;
            break;
        default:
            fputc(first, out);
            break;
    }
}
//处理C_STATE的的函数 /*...*/可以注释多行
void doCStatus(FILE *in, FILE *out)
{
    int first = fgetc(in);
    int second = 0;
    assert(in);
    assert(out);
    switch (first)
    {
    case '*'://表示C语言注释状态 可能会结束
    {
        second = fgetc(in);
        if (second == '/')
        {
            int third = fgetc(in);
            if (third == '\n')
            {
                fputc(third, out);
            }
            else
            {
                fputc('\n', out);
                ungetc(third, in);
                gStatus = NORMAL_STATUS;
            }
        }
        else
        {
            fputc(first, out);
            ungetc(second, in);//将多余用来判断的字符撤销
        }
    }
    break;
    case '\n':
        fputc(first, out);
        fputc('/', out);
        fputc('/', out);
        break;
    case EOF:
        gStatus = END_STATUS;
        break;
    default:
        fputc(first, out);
        break;
    }
}
//处理CPP_STATE的函数,只能注释一行
void doCPPStatus(FILE *in, FILE *out)
{
    int first = fgetc(in);
    assert(in);
    assert(out);
    int second = 0;
    switch (first)
    {
    case '\n':
        fputc(first, out);
        gStatus = NORMAL_STATUS;
        break;
    case EOF:
        gStatus = END_STATUS;
        break;
    default:
        fputc(first, out);
        break;
    }
}

int main()
{
    convertBegin();
    printf("转换完成。\n");
    system("pause");
    return 0;
}