等价于c ++中的Java的String.getBytes（“ UTF-8”）？

Question

I need to implement this Java code in (unmanaged) c++:

byte[] b = string.getBytes("UTF8");

I'm new to c++, and can't find anything to do this. It has to be platform independent, if possible. Using c++11 compiler.

Answer 1

Java String is roughly equivalent to std::u16string , a specialization of std::basic_string . I suggest you try something like...

std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t> convert;
std::string converted = convert.to_bytes(u"HELLO, WORLD!");
const char *bytes = converted.data();

Note this relies on C++11; it might be sometime before your compiler vendor fully supports these features.

Here, we utilize the newly introduced std::wstring_convert to convert from a wide-character UTF-16 string to the UTF-8 multibyte string via to_bytes (it also supports conversion in the other direction, too).

This is made possible via the (also newly introduced) std::codecvt_utf8_utf16 conversion facet. It takes care of the actual conversion for us nicely.

Besides that, it makes use of the new character literal prefixes added with C++11 -- in particular, u , which is for char16_t UTF-16 strings :-) There are also u8 and U for UTF-8 and UTF-32, respectively.

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PS data is (as of C++11) guaranteed to be equal to c_str and therefore can be relied upon to be NUL-terminated.

Answer 2

Solution Number 1:-

 char bytecpp[]= u8"You don't need strings.getbytes :P";

Solution Number 2:-

std::wstring_convert<std::codecvt_utf8_utf16<char16_t>> myconv;
std::string mbstring = myconv.to_bytes(u"Hello\n");
std::cout << mbstring;

Answer 3

Assuming the string is already in UTF-8, you can use:

char const *c = myString.c_str();

For read/write access, you could use:

std::vector<char> bytes(myString.begin(), myString.end());
bytes.push_back('\0');
char *c = &bytes[0];

Answer 4

A string in C++ is typically ASCII 1 byte per character. So you would have to take care of it before you marshaled it to C++ if you went with the typical std::string. However C++ does define a wide character string std::wstring, unfortunately(from the wikipedia article on wide characters):

The width of wchar_t is compiler-specific and can be as small as 8 bits. Consequently, programs that need to be portable across any C or C++ compiler should not use wchar_t for storing Unicode text. The wchar_t type is intended for storing compiler-defined wide characters, which may be Unicode characters in some compilers.

So we would have to know what C++ compiler you were going to use to answer the question completely. For the std::wstring class there is no to bytes type function, so what you want to do is use c_str() as mentioned in the other answers then use &(bit wise and) and a byte mask to split the wide characters in to bytes.

in visual C++ a wide character is 16 bits so you would want something like the following to process each characters in to bytes:

high_byte = wcharacter & 0xFF00;
low_byte = wcharacter & 0xFF;