C++ append int to wstring

Question

Before(using ASCII) i was using std::string as buffer like this:

std::string test = ""; int value = 6; test.append("some string"); test.append((char*)value, 4); test.append("some string");

with expected value in test:

"some srtring\x6\x0\x0\x0somestring"

Now i am tring to use Unicode and i wanna keep the same "code" but trubles happens:

std::wstring test = ""; int value = 6; test.append("some string"); test.append((wchar_t*)value, 4); (buffer overflow cause reading 8 bytes) test.append("some string");

How can i append bytes like in std::string? Doing:

std::wstring test = ""; int value = 6; test.append("some string"); test.append((wchar_t*)value, 2); test.append("some string");

Solve partially the problem cause after i can't append bools.

EDIT: i can even use wstringstream if a binary copy is applied.(normally not)

Why don't you use std::to_string and std::to_wstring? (and use + for concat) — pergy
– pergy, Commented Mar 31, 2017 at 14:00
Casts are usually a bad idea. C-style casts are usually an even worse idea. Had you used a C++ cast, you'd find that static_cast<char*>(value) won't compile. Generally, a static_cast is at least safe. By not compiling, at least you might be deterred from trying to cast like that. (char*)value takes the bytes and reinterprets them as characters. Are you sure that's what you really want? Of course not, but the cast doesn't tell you that, like reinterpret_cast does. — Qaz
– Qaz, Commented Mar 31, 2017 at 14:10
i need a "binary" dynamic buffer, where i can add the real size of types(bool 1, int 4 etc) — Ixiodor
– Ixiodor, Commented Mar 31, 2017 at 14:28
@BoundaryImposition: And you don't use ASCII by using std::string, either :) — Christian Hackl
– Christian Hackl, Commented Mar 31, 2017 at 14:30

rwols · Accepted Answer · 2017-03-31 15:20:02Z

You're confusing unicode and character encodings. An std::string can represent unicode code points just fine, using the UTF-8 encoding.

Windows uses the UTF-16LE (or UTF-16 with a BOM, I believe) encoding to represent unicode glyphs. Most others use UTF-8.

An std::string which is encoded in UTF-8 and which uses only ASCII characters can actually be interpreted as an ASCII string. This is the beauty of UTF-8. It's a natural extension.

Anyway,

i need a "binary" dynamic buffer, where i can add the real size of types(bool 1, int 4 etc)

An std::vector<uint8_t> is probably more suitable for this task. It communicates that it is not something human-readable, per se. If you need to embed strings into this buffer, make sure that sizeof(char) == sizeof(uint8_t) on the platform, and then just write the data as-is to this buffer.

If you're saving this buffer on one machine and try to read it on another machine, you have to take care of endianness too.

user · Accepted Answer · 2017-03-31 14:24:10Z

You make a function that reads the stuff you want to put:

void putBytes(std::wstring& s, char* c, int numBytes) { while (numBytes-- > 0) s += (wchar_t)*c++; }

Then you can call it:

int value = 65; putBytes(s, reinterpret_cast<char*>(&value), sizeof(value));

Ixiodor · Accepted Answer · 2017-03-31 15:00:43Z

I think a IStream is a proper way to do this...i'll make an interface to handle different types. I was abusing std::string for an easy "dynamic binary array", with std::wstring this is not possible,for many reasons but most silly one is that require at least 2 bytes, so no room for a bool

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