对 STL 字符串使用 fread/fwrite。正确吗？
我有一个包含字符串的结构。像这样的东西：
struct Chunk { 整数a； 字符串 b； 整数c; 因此
，我想我无法使用 fread 和 fwrite 函数从文件中写入和读取此结构。因为字符串可能保留不同的内存容量。 但这样的代码可以正常工作。
Chunk var;
fwrite(&var, sizeof(Chunk), 1, file);
fread(&var, sizeof(Chunk), 1, file );
这里面真的有问题吗？
I have a structure, that contain string. Something like that:
struct Chunk {
int a;
string b;
int c;
};
So, i suppose, that i cannot write and read this structure from file using fread and fwrite functions. Because string may reserve different memory capacity.
But such code works correctly.
Chunk var;
fwrite(&var, sizeof(Chunk), 1, file);
fread(&var, sizeof(Chunk), 1, file);
Is there really some problems in it?
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评论（3）
你有理由怀疑这一点。您应该仅使用
fwrite和fread流式传输 POD 类型，并且string不是POD。You are justified in doubting this. You should only stream POD types with
fwriteandfreadandstringis notPOD.您不应该这样做，因为不同的实现使用不同的
std::string结构。一般来说，你应该只序列化整型、布尔类型、二进制数据（如果你可以称之为序列化）。如果您考虑在平台之间共享序列化数据，请确保使用一种字节序。
小心浮点数、双精度数和指针。他们会变得非常讨厌。
您也必须注意 C/C++ 结构，因为它们可能包含不可预测的填充量。
You shouldn't do it like this, because different implementations use different structures of
std::string.In general you should only serialize integral types, the boolean type, binary data (if you can call it serializing). Make sure to use one endian-ness if you are thinking of sharing serialized data between platforms.
Watch out with floats, doubles and pointers. They can become very pesky.
You'll have to watch out with C/C++ structs too ebcause they can contain unpredictable amounts of padding.
您应该序列化数据。
您可能想手动执行此操作 - 当涉及
std::string时，请查看：const charT* std::string::c_str() constconst charT* std::string::data() const当涉及到更复杂的对象时，您可能会对 Google Protocol Buffers 和/或 Thrift 之类的东西。
You should serialize data.
You might like to do this manually - when it comes about
std::string, check out:const charT* std::string::c_str() constconst charT* std::string::data() constWhen it comes about more complex objects, you might be interested in things like Google Protocol Buffers and/or Thrift.