问题描述

什么是在 std::string 和 QByteArray 之间无损转换的正确方法...主要是为了处理二进制数据?

What is the correct way to convert losslessly between std::string and QByteArray... mostly for the purpose of handling binary data?

我正在使用:

QByteArray qba = QString::fromStdString(stdString).toAscii();

和

QString(qba).toStdString();

但我想检查一下这是否真的正确.

but I wanted to check whether this is actually correct.

推荐答案

对于二进制数据，您的解决方案是有问题的，因为非 ASCII 字符会被 QString:: 转换为 '?'toAscii().对于 QString 的内部表示，还有不必要的 UTF-16 转换开销.正如您可能已经猜到的那样，QString 仅应在数据是文本而非二进制数据时使用.

For binary data your solution is problematic since non-ASCII characters would be converted to '?' by QString::toAscii(). There is also the unnecessary overhead of UTF-16 conversion for the internal representation of QString. As you might have guessed, QString should only be used if the data is textual, not binary.

QByteArray 和 std::string 都有原始数据(C 字符串 + 长度)的构造函数，也有转换为 C 字符串 + 长度的构造函数.因此您可以使用它们进行转换:

Both QByteArray and std::string have constructors for raw data (C-string + length) and also a conversion to C-string + length. So you can use them for conversion:

// std::string => QByteArray
QByteArray byteArray(stdString.c_str(), stdString.length());

// QByteArray => std::string
std::string stdString(byteArray.constData(), byteArray.length());

它们都是二进制安全的，这意味着字符串可能包含 '' 字符并且不会被截断.数据也不会被触及(没有 UTF 转换)，所以这种转换是无损"的.

They are both binary-safe, meaning that the string may contain '' characters and doesn't get truncated. The data also doesn't get touched (there is no UTF conversion), so this conversion is "lossless".

确保使用长度作为第二个参数的构造函数(对于 QByteArray 和 std::string)，因为大多数其他构造函数会在之前截断数据第一次出现零.

Make sure to use the constructors with the length as the second argument (for both QByteArray and std::string), as most other constructors will truncate the data before the first occurrence of a zero.

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