C ++ fstream read&写 [英] C++ fstream read & write
问题描述
关于如何阅读文件，我有一个简短的问题。具体来说，你怎么能一次读取一个文件的大约100个字符，然后将相同的字符写入同一个文件。如果你想在一个文件上运行xor op而不使用除源之外的任何文件，那就好了。
我尝试过：
这个
无效main（）
{
int theSize = 32;
char * data = new char [36];
fstream fileStreamIn（in，ios :: in | ios :: out | ios :: binary）;
while（fileStreamIn）
{
fileStreamIn.read（data，theSize）;
size_t count = fileStreamIn.gcount（）;
cout<<数据;
fileStreamIn<<数据;
fileStreamIn.write（数据，计数）;
}
fileStreamIn.close（）;
系统（暂停）;
}
I have a brief question as to how you would read a file. Specifically how could you read about 100 characters of a file at a time then write the very same characters to the same file.Like if you wanted to run an xor op on a file without using any file other than the source.
What I have tried:
This
void main ()
{
int theSize = 32;
char *data = new char[36];
fstream fileStreamIn("in",ios::in | ios::out | ios::binary);
while(fileStreamIn)
{
fileStreamIn.read(data,theSize);
size_t count = fileStreamIn.gcount();
cout << data;
fileStreamIn << data;
fileStreamIn.write(data,count);
}
fileStreamIn.close();
system("pause");
}
推荐答案
阅读很简单：你已经这样做了。
写作很容易：你也是这样做的。
所需要的就是寻找职位： istream :: seekg - C ++参考 [ ^ ]
值得注意的是，如果您从Read切换到Write，反之亦然，那么无论如何都要寻找合适的位置是个好主意，因为有些系统确实保持独立输入和输出指针。
Reading is easy: you are already doing that.
And writing is easy: you are doing that as well.
All you need to is Seek the position: istream::seekg - C++ Reference[^]
It's worth noting that if you are switching from Read to Write or vice versa, it's a good idea to seek the right position anyway, as some systems do maintain independent input and output pointers.
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