用getc 和putc 复制一个程序代码到另一个文本中时怎么去掉//后面的部分

#include <stdio.h>

int main( void )
{
    FILE* in = fopen( "a.txt", "r" );
    if( !in )
    {
        puts( "[error] failed to open file \"a.txt\"" );
        return 1;
    }

    FILE* out = fopen( "b.txt", "w" );
    if( !out )
    {
        fclose( in );
        puts( "[error] failed to open file \"b.txt\"" );
        return 2;
    }

    int state = 0; // 状态1表示遇到第一个斜杠，状态2表示已遇到两个斜杠，状态0表示其它情况
    for( int ch; ch=getc(in), ch!=EOF; )
    {
        if( ch == '\n' )
        {
            if( state == 1 )
                putc( '/', out );
            state = 0;
            putc( ch, out );
        }
        else if( state == 2 )
        {
        }
        else if( ch=='/' && state==1 )
        {
            state = 2;
        }
        else if( ch == '/' )
        {
            state = 1;
        }
        else
        {
            if( state == 1 )
                putc( '/', out );
            state = 0;
            putc( ch, out );
        }
    }

    if( ferror(in) )
    {
        fclose( out );
        fclose( in );
        puts( "[error] failed to read file \"a.txt\"" );
        return 3;
    }
    if( ferror(out) )
    {
        fclose( out );
        fclose( in );
        puts( "[error] failed to write file \"b.txt\"" );
        return 4;
    }

    fclose( out );
    fclose( in );
    return 0;
}