VC.net String to LPWSTR - visual-c++

How can I transform from string to LPWSTR
String^ str= "hello world";
LPWSTR apppath= (LPWSTR)(Marshal::StringToHGlobalAnsi(str).ToPointer());
But it doesn't work.After transformed:

You're trying to read single-byte characters (that's what Marshal::StringToHGlobalAnsi is returning) as wide characters (that's what an LPWSTR type points to), and you're getting whatever is in memory interpreted as a wide-character string.
You need to marshal the appropriate type, and you need to be aware of the lifetime of the result. Here's an example program that shows one way to do it, modified from the MSDN example in marshal_context::marshal_as:
// compile with: /clr
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <msclr\marshal.h>
using namespace System;
using namespace msclr::interop;
int main() {
marshal_context^ context = gcnew marshal_context();
String^ str = "hello world";
LPWSTR apppath = const_cast<wchar_t*>(context->marshal_as<const wchar_t*>(str));
wprintf(L"%s\n", apppath);
delete context;
return 0;
}
Note that a reference to apppath is likely to be bogus after the deletion of context.

Related

Cuda - printing string from object in __global__ function

I am new to CUDA and I am getting a strange error. I want to print a string from a passed object and I get the error "calling host function from global function is not allowed" and I don't know why. But if I want to print an integer (changing get method to return sk1), everything works fine. Here is the code:
class Duomenys {
private:
string simb;
int sk1;
double sk2;
public:
__device__ __host__ Duomenys(void): simb(""), sk1(0), sk2(0.0) {}
__device__ __host__~Duomenys() {}
__device__ __host__ Duomenys::Duomenys(string simb1, int sk11, double sk21)
: simb(simb1), sk1(sk11), sk2(sk21) {}
__device__ __host__ string Duomenys::get(){
return simb;
}
};
And here I am calling Duomenys::get from __global__ function:
__global__ void Vec_add(Duomenys a) {
printf(" %s \n",a.get());
}
EDIT: I am trying to read data from a file and print it in a global function. In this code I am trying read all data and print just one object to see if everything works. This is the error I'm getting:
calling a __host__ function("std::basic_string<char, std::char_traits<char>, std::allocator<char> >::~basic_string") from a __global__ function("Vec_add") is not allowed
Code:
#include <stdio.h>
#include <stdlib.h>
#include <cuda.h>
#include <cuda_runtime.h>
#include <vector>
#include <string>
#include <iostream>
#include <fstream>
#include <iomanip>
#include <string>
#include <sstream>
using namespace std;
class Duomenys {
private:
string simb;
int sk1;
double sk2;
public:
__device__ __host__ Duomenys(void): simb(""), sk1(0), sk2(0.0) {}
__device__ __host__~Duomenys() {}
__device__ __host__ Duomenys::Duomenys(string simb1, int sk11, double sk21)
: simb(simb1), sk1(sk11), sk2(sk21) {}
__device__ __host__ string Duomenys::print()
{
stringstream ss;
ss << left << setw(10) << simb << setw(10) << sk1 << setw(10) << sk2;
return ss.str();
}
};
__global__ void Vec_add(Duomenys a) {
printf(" %s \n",a.print());
}
/* Host code */
int main(int argc, char* argv[]) {
setlocale (LC_ALL,"");
vector<Duomenys> vienas;
vector<vector<Duomenys>> visi;
//data reading to vector "vienas" (it works without any errors)
Duomenys *darr;
const size_t sz = size_t(2) * sizeof(Duomenys);
cudaMalloc((void**)&darr, sz);
Vec_add<<<1, 1>>>(visi[0].at(0));
cudaDeviceSynchronize();
cudaMemcpy(darr, &visi[0].at(0), sz, cudaMemcpyHostToDevice);
return 0;
}
Your problem is not with printf function, but with string data type. You cannot use the C++ string type in a kernel. See related question here: Can we use the string data type in C++ within kernels
Why would you pass a string object to printf when the %s format specifier is expecting something else? When I try to do that in ordinary host code, I get warnings about "passing non-POD types through ellipsis (call will abort at runtime)". Note that this problem has nothing to do with CUDA.
But beyond that issue, presumably you're getting string from the C++ standard library. (It's better if you show a complete reproducer code, then I don't have to guess at where you're getting things or what you are including.)
If I get string as follows:
#include <string>
using namespace std;
Then I am using a function defined in the C++ Standard Library. CUDA supports the C++ language (mostly) but does not necessarily support usage of C++ libraries (or C libraries, for that matter) in device code. Libraries are (usually) composed of (at least some) compiled code (such as allocators, in this case), and this code has been compiled for CPUs, not for the GPU. When you try to use such a CPU compiled routine (e.g. an allocator associated with the string class) in device code, the compiler will bark at you. If you include the complete error message in the question, it will be more obvious specifically what (compiled-for-the-host) function is actually the issue.
Use a standard C style string instead (i.e. char[] and you will be able to use it directly in printf.
EDIT: In response to a question in the comments, here is a modified version of the code posted that demonstrates how to use an ordinary C-style string (i.e. char[]) and print from it in device code.
#include <stdio.h>
#include <stdlib.h>
#include <cuda.h>
#include <cuda_runtime.h>
#include <vector>
#include <iostream>
#include <fstream>
#include <iomanip>
#include <string>
#include <sstream>
#define STRSZ 32
using namespace std;
class Duomenys {
private:
char simb[STRSZ];
int sk1;
double sk2;
public:
__device__ __host__ Duomenys(void): sk1(0), sk2(0.0) {}
__device__ __host__~Duomenys() {}
__device__ __host__ Duomenys(char *simb1, int sk11, double sk21)
: sk1(sk11), sk2(sk21) {}
__device__ __host__ char * print()
{
return simb;
}
__device__ __host__ void store_str(const char *str)
{
for (int i=0; i< STRSZ; i++)
simb[i] = str[i];
}
};
__global__ void Vec_add(Duomenys a) {
printf(" %s \n",a.print());
}
/* Host code */
int main(int argc, char* argv[]) {
string host_string("hello\n");
setlocale (LC_ALL,"");
vector<Duomenys> vienas(3);
vienas[0].store_str(host_string.c_str());
vector<vector<Duomenys> > visi(3);
visi[0] = vienas;
//data reading to vector "vienas" (it works without any errors)
Duomenys *darr;
const size_t sz = size_t(2) * sizeof(Duomenys);
cudaMalloc((void**)&darr, sz);
Vec_add<<<1, 1>>>(visi[0].at(0));
cudaDeviceSynchronize();
cudaMemcpy(darr, &(visi[0].at(0)), sz, cudaMemcpyHostToDevice);
return 0;
}
Note that I didn't try to understand your code or fix everything that looked strange to me. However this should demonstrate one possible approach.

convert from std::string to String^

I have a function in C++ that have a value in std::string type and would like to convert it to String^.
void(String ^outValue)
{
std::string str("Hello World");
outValue = str;
}
From MSDN:
#include <string>
#include <iostream>
using namespace System;
using namespace std;
int main() {
string str = "test";
String^ newSystemString = gcnew String(str.c_str());
}
http://msdn.microsoft.com/en-us/library/ms235219.aspx
Googling reveals marshal_as (untested):
// marshal_as_test.cpp
// compile with: /clr
#include <stdlib.h>
#include <string>
#include <msclr\marshal_cppstd.h>
using namespace System;
using namespace msclr::interop;
int main() {
std::string message = "Test String to Marshal";
String^ result;
result = marshal_as<String^>( message );
return 0;
}
Also see Overview of Marshaling.
As far as I got it, at least the marshal_as approach (not sure about gcnew String) will lead to non ASCII UTF-8 characters in the std::string to be broken.
Based on what I've found on https://bytes.com/topic/c-sharp/answers/725734-utf-8-std-string-system-string I've build this solution which seems to work for me at least with German diacritics:
System::String^ StdStringToUTF16(std::string s)
{
cli::array<System::Byte>^ a = gcnew cli::array<System::Byte>(s.length());
int i = s.length();
while (i-- > 0)
{
a[i] = s[i];
}
return System::Text::Encoding::UTF8->GetString(a);
}

how to transfer contents of char[] to a String^ in C++/CLI

I've commandLine arguments in a C++/CLI program denoted by char* argv[].
I want to transfer all the contents getting concatenated to a String^ class.
Code:
String ^masterString = "Commands=>";
for(int i=0; argv[i] != nullptr; ++i)
masterString += String(argv[i]);
However, I find the above not working in the last statement where I use += operator.
What's the wrong usage here? Error here is No operators match the operands.
Any other better ways to store contents into String^ from char*?
Look into MSDN, mostly into this:
#include <stdlib.h>
#include <string.h>
#include <msclr\marshal.h>
using namespace System;
using namespace msclr::interop;
int main() {
const char* message = "Test String to Marshal";
String^ result;
result = marshal_as<String^>( message );
return 0;
}
btw: I didn't check this. Just googled it. But, I think, this would work, cause it posted in MSDN.

Inputting a string

Can't compile something as simple as this, yet when I change the variable type from
string to int, it compiles and runs fine. Any ideas why this is happening?
#include <iostream>
using namespace std;
void main()
{
string x;
cin>>x;
}
You need:
#include <string>
To get std::string in your application.

C++/CLI Converting from System::String^ to std::string

Can someone please post a simple code that would convert,
System::String^
To,
C++ std::string
I.e., I just want to assign the value of,
String^ originalString;
To,
std::string newString;
Don't roll your own, use these handy (and extensible) wrappers provided by Microsoft.
For example:
#include <msclr\marshal_cppstd.h>
System::String^ managed = "test";
std::string unmanaged = msclr::interop::marshal_as<std::string>(managed);
You can easily do this as follows
#include <msclr/marshal_cppstd.h>
System::String^ xyz="Hi boys";
std::string converted_xyz=msclr::interop::marshal_as< std::string >( xyz);
Check out System::Runtime::InteropServices::Marshal::StringToCoTaskMemUni() and its friends.
Sorry can't post code now; I don't have VS on this machine to check it compiles before posting.
This worked for me:
#include <stdlib.h>
#include <string.h>
#include <msclr\marshal_cppstd.h>
//..
using namespace msclr::interop;
//..
System::String^ clrString = (TextoDeBoton);
std::string stdString = marshal_as<std::string>(clrString); //String^ to std
//System::String^ myString = marshal_as<System::String^>(MyBasicStirng); //std to String^
prueba.CopyInfo(stdString); //MyMethod
//..
//Where: String^ = TextoDeBoton;
//and stdString is a "normal" string;
Here are some conversion routines I wrote many years ago for a c++/cli project, they should still work.
void StringToStlWString ( System::String const^ s, std::wstring& os)
{
String^ string = const_cast<String^>(s);
const wchar_t* chars = reinterpret_cast<const wchar_t*>((Marshal::StringToHGlobalUni(string)).ToPointer());
os = chars;
Marshal::FreeHGlobal(IntPtr((void*)chars));
}
System::String^ StlWStringToString (std::wstring const& os) {
String^ str = gcnew String(os.c_str());
//String^ str = gcnew String("");
return str;
}
System::String^ WPtrToString(wchar_t const* pData, int length) {
if (length == 0) {
//use null termination
length = wcslen(pData);
if (length == 0) {
System::String^ ret = "";
return ret;
}
}
System::IntPtr bfr = System::IntPtr(const_cast<wchar_t*>(pData));
System::String^ ret = System::Runtime::InteropServices::Marshal::PtrToStringUni(bfr, length);
return ret;
}
void Utf8ToStlWString(char const* pUtfString, std::wstring& stlString) {
//wchar_t* pString;
MAKE_WIDEPTR_FROMUTF8(pString, pUtfString);
stlString = pString;
}
void Utf8ToStlWStringN(char const* pUtfString, std::wstring& stlString, ULONG length) {
//wchar_t* pString;
MAKE_WIDEPTR_FROMUTF8N(pString, pUtfString, length);
stlString = pString;
}
I found an easy way to get a std::string from a String^ is to use sprintf().
char cStr[50] = { 0 };
String^ clrString = "Hello";
if (clrString->Length < sizeof(cStr))
sprintf(cStr, "%s", clrString);
std::string stlString(cStr);
No need to call the Marshal functions!
UPDATE Thanks to Eric, I've modified the sample code to check for the size of the input string to prevent buffer overflow.
I spent hours trying to convert a windows form listbox ToString value to a standard string so that I could use it with fstream to output to a txt file. My Visual Studio didn't come with marshal header files which several answers I found said to use. After so much trial and error I finally found a solution to the problem that just uses System::Runtime::InteropServices:
void MarshalString ( String ^ s, string& os ) {
using namespace Runtime::InteropServices;
const char* chars =
(const char*)(Marshal::StringToHGlobalAnsi(s)).ToPointer();
os = chars;
Marshal::FreeHGlobal(IntPtr((void*)chars));
}
//this is the code to use the function:
scheduleBox->SetSelected(0,true);
string a = "test";
String ^ c = gcnew String(scheduleBox->SelectedItem->ToString());
MarshalString(c, a);
filestream << a;
And here is the MSDN page with the example:
http://msdn.microsoft.com/en-us/library/1b4az623(v=vs.80).aspx
I know it's a pretty simple solution but this took me HOURS of troubleshooting and visiting several forums to finally find something that worked.
C# uses the UTF16 format for its strings.
So, besides just converting the types, you should also be conscious about the string's actual format.
When compiling for Multi-byte Character set Visual Studio and the Win API assumes UTF8 (Actually windows encoding which is Windows-28591 ).
When compiling for Unicode Character set Visual studio and the Win API assume UTF16.
So, you must convert the string from UTF16 to UTF8 format as well, and not just convert to std::string.
This will become necessary when working with multi-character formats like some non-latin languages.
The idea is to decide that std::wstring always represents UTF16.
And std::string always represents UTF8.
This isn't enforced by the compiler, it's more of a good policy to have.
#include "stdafx.h"
#include <string>
#include <codecvt>
#include <msclr\marshal_cppstd.h>
using namespace System;
int main(array<System::String ^> ^args)
{
System::String^ managedString = "test";
msclr::interop::marshal_context context;
//Actual format is UTF16, so represent as wstring
std::wstring utf16NativeString = context.marshal_as<std::wstring>(managedString);
//C++11 format converter
std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>> convert;
//convert to UTF8 and std::string
std::string utf8NativeString = convert.to_bytes(utf16NativeString);
return 0;
}
Or have it in a more compact syntax:
int main(array<System::String ^> ^args)
{
System::String^ managedString = "test";
msclr::interop::marshal_context context;
std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>> convert;
std::string utf8NativeString = convert.to_bytes(context.marshal_as<std::wstring>(managedString));
return 0;
}
I like to stay away from the marshaller.
Using CString newString(originalString);
Seems much cleaner and faster to me. No need to worry about creating and deleting a context.
// I used VS2012 to write below code-- convert_system_string to Standard_Sting
#include "stdafx.h"
#include <iostream>
#include <string>
using namespace System;
using namespace Runtime::InteropServices;
void MarshalString ( String^ s, std::string& outputstring )
{
const char* kPtoC = (const char*) (Marshal::StringToHGlobalAnsi(s)).ToPointer();
outputstring = kPtoC;
Marshal::FreeHGlobal(IntPtr((void*)kPtoC));
}
int _tmain(int argc, _TCHAR* argv[])
{
std::string strNativeString;
String ^ strManagedString = "Temp";
MarshalString(strManagedString, strNativeString);
std::cout << strNativeString << std::endl;
return 0;
}
For me, I was getting an error with some of these messages. I have an std::string. To convert it to String^, I had to do the following String^ sysString = gcnew String(stdStr.c_str()); where sysString is a System::String^ and stdStr is an std::string. Hope this helps someone
You may have to #include <string> for this to work

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