can someone tell how to convert UaString to std::string in c++.
There is already a question which converts std::string to uastring:
How can i convert a std::string to UaString?
Thanks in advance!
e.g. You have UaString as below:
UaString sString("Test String");
Then you can make standard string as,
std::string myString(sString.toUtf8());
Reference:
UA Server SDK C++
C++ String Class
One way could be to use the toUtf8 member function which returns a const char* that can be used to construct a std::string.
std::string str(uastring.toUtf8());
An alternative if uastring may contain null terminators:
std::string str(uastring.toUtf8(), uastring.size());
Note that UaString::length() shouldn't be used in this case since it returns the number of UTF8 characters while UaString::size() returns the number of bytes (which may be greater).
Related
I'm receiving following error:
Debug Assertion Failed!
Expression: string iterators incompatible
When trying to run such a code:
std::string string_Dir(){return ".\\Dir\\";}
std::wstring wstring_Dir=std::wstring(
string_Dir().begin()
,string_Dir().end()
);
SetDllDirectory(wstring_Dir.c_str());
Does someone know why
BTW: I followed this.
You are calling string_Dir() twice and then using iterators from different std::string objects to initialize your std::wstring. That is why you are getting an incompatibility error. You must use iterators from the same std::string object, so call string_Dir() once and assign the return value to a variable:
std::string dir = string_Dir();
std::wstring wstring_Dir(dir.begin(), dir.end());
SetDllDirectory(wstring_Dir.c_str());
// or better: SetDllDirectoryW(wstring_Dir.c_str());
That being said, you are not converting from ANSI to UTF-16, so this code will only work correctly if string_Dir() returns a std::string that contains only 7bit ASCII characters. It will fail if the std::string contains any non-ASCII 8bit characters.
There is a simpler solution - you can call SetDllDirectoryA() instead. You don't need the std::wstring, and the OS can do the ANSI-to-UTF16 conversion for you:
SetDllDirectoryA(string_Dir().c_str());
According to the documentation, the value in the function call is supposed to be LPCTSTR instead of LPCTWSTR.
I'm new to c++ (I'm a c# developer).
I have an SQLite wrapper class that requires you to pass in a database name as a const char* , however I only have it as a Platform::String (after doing a file search).
I cant seem to find a way to convert the Platform::String to const char*.
Ive seen another question on StackOverflow that explain why it isnt straight-forward, but no sample code or end-to-end solution.
Can anyone help me ?
Thanks
Disclaimer: I know little about C++/CX, and I'm basing the answer on the documentation here.
The String class contains 16-bit Unicode characters, so you can't directly get a pointer to 8-bit char-typed characters; you'll need to convert the contents.
If the string is known to only contain ASCII characters, then you can convert it directly:
String s = whatever();
std::string narrow(s.Begin(), s.End());
function_requiring_cstring(narrow.c_str());
Otherwise, the string will need translating, which gets rather hairy. The following might do the right thing, converting the wide characters to multi-byte sequences of narrow characters:
String s = whatever();
std::wstring wide(s.Begin(), s.End());
std::vector<char> buffer(s.Length()+1); // We'll need at least that much
for (;;) {
size_t length = std::wcstombs(buffer.data(), wide.c_str(), buffer.size());
if (length == buffer.size()) {
buffer.resize(buffer.size()*2);
} else {
buffer.resize(length+1);
break;
}
}
function_requiring_cstring(buffer.data());
Alternatively, you may find it easier to ignore Microsoft's ideas about how strings should be handled, and use std::string instead.
I am using the following method to read a txt file
modelStream.open("file.txt", ios::in);
if (modelStream.fail())
exit(1);
model = new Model(modelStream);
but i want to know how i can pass in a string as a parameter
string STRING;
modelStream.open(STRING, ios::in);
if (modelStream.fail())
exit(1);
model = new Model(modelStream);
does anyone know if this is possible and if it is how would I do it?
For legacy reasons, iostreams in C++03 expects a C-style, null-terminated string as argument and doesn't understand std::string. Fortunately, std::string can produce a C-style, null-terminated string, with the function std::string::c_str():
modelStream.open(STRING.c_str(), ios::in);
This was actually "fixed" in C++11, so if you were using it your original code would be functional.
Also, an all-caps variable name is not recommended; neither is a variable called "string". Make the name describe the meaning.
Simply use c_str () method of std::string
modelStream.open(STRING.c_str (), ios::in);
the standard streams doesn't accept a standard string, only c-string! So pass the string using c_str():
modelStream.open(STRING.c_str(), ios::in);
I have a function that I cannot touch, Is a "log maker", It puts something to print in a file an show it up when I run the file. The problem is that the function only gets const string so if I want to print something I have to convert everything in this data type (I cannot use cout).
itoa & atoi functions are not standard functions so I cannot use it neither. C++ is very "special" with data types and doesn't accept conversions really easy, so this is my question:
How can I convert everytype of data into string for the log purposes?
Probably I should check data type on a function to convert things and returning them into a stringstream (witch I have to convert into a string, of course).
So, any advice on how to do that?
boost::lexical_cast encapsulates the use of ostringstream, so you
could use that. Otherwise, the code isn't that difficult:
template<typename T>
std::string
toString( T const& object )
{
std::ostringstream results;
results << object;
return results.str();
}
(There's no reason to use stringstream here; ostringstream is largely sufficient.
You can use
std::stringstream
or
boost lexical_cast<>
Yes, if you want arbitrary type in string representation stringstream intermediate sounds like a solution.
I assume the functions expects a const std::string & ?
Your approach with std::stringstream is correct. Alternatively you could simply write a toString() method for the class you wish to directly output. However, usually when one wants to output objects to a file, overloads the << operator for that particular type.
How to convert AS3 ByteArray into wchar_t const* filename?
So in my C code I have a function waiting for a file with void fun (wchar_t const* filename) how to send to that function my ByteArray? (Or, how should I re-write my function?)
A four month old question. Better late than never?
To convert a ByteArray to a String in AS3, there are two ways depending on how the String was stored. Firstly, if you use writeUTF it will write an unsigned short representing the String's length first, then write out the string data. The string is easiest to recover this way. Here's how it's done in AS3:
byteArray.position = 0;
var str:String = byteArray.readUTF();
Alternatively, toString also works in this case. The second way to store is with writeUTFBytes. This won't write the length to the beginning, so you'll need to track it independantly somehow. It sounds like you want the entire ByteArray to be a single String, so you can use the ByteArray's length.
byteArray.position = 0;
var str:String = byteArray.readUTFBytes(byteArray.length);
Since you want to do this with Alchemy, you just need to convert the above code. Here's a conversion of the second example:
std::string batostr(AS3_Val byteArray) {
AS3_SetS(byteArray, "position", AS3_Int(0));
return AS3_StringValue(AS3_CallS("readUTFBytes", byteArray,
AS3_Array("AS3ValType", AS3_GetS(byteArray, "length")) ));
}
This has a ridiculous amount of memory leaks, of course, since I'm not calling AS3_Release anywhere. I use a RAII wrapper for AS3_Val in my own code... for the sake of my sanity. As should you.
Anyway, the std::string my function returns will be UTF-8 multibyte. Any standard C++ technique for converting to wide characters should work from here. (search the site for endless reposts) I suggest leaving it is as it, though. I can't think of any advantage to using wide characters on this platform.