• <ins id="pjuwb"></ins>
    <blockquote id="pjuwb"><pre id="pjuwb"></pre></blockquote>
    <noscript id="pjuwb"></noscript>
          <sup id="pjuwb"><pre id="pjuwb"></pre></sup>
            <dd id="pjuwb"></dd>
            <abbr id="pjuwb"></abbr>
            posts - 17,  comments - 2,  trackbacks - 0


            System::String -> std::string
            A reader asks,
             
            Sender: Erik Brendengen
             
            Is there an easy way to convert from String^ to std::string?
                         Does String ^s = std::string( “bla”).c_str(); work the other way?
             
            This is a FAQ, one that I myself bumped into when I had to pass a System::String retrieved from System::Windows::Forms::TextBox to a native program that expected a std::string.
             
            There are generally two conversion strategies, depending on which side of the managed/native fence you wish to do the conversion work. Here are two methods making use of the PtrToStringChars( String^ ) utility from the vcclr.h header file that is part of Visual C++. Note that these are written in the new C++/CLI syntax – and that these are adapted from an internal FAQ ...
             
            #include <stdlib.h>
            #include <vcclr.h>
            #include <string>
            using namespace System;
             
            bool To_CharStar( String^ source, char*& target )
            {
                pin_ptr<const wchar_t> wch = PtrToStringChars( source );
                int len = (( source->Length+1) * 2);
                target = new char[ len ];
                return wcstombs( target, wch, len ) != -1;
            }
             
            bool To_string( String^ source, string &target )
            {
                pin_ptr<const wchar_t> wch = PtrToStringChars( source );
                int len = (( source->Length+1) * 2);
                char *ch = new char[ len ];
                bool result = wcstombs( ch, wch, len ) != -1;
                target = ch;
                delete ch;
                return result;
            }
             
            As to the second question, does String^ s = ns.c_str() work? Yes.
            Published Wednesday, June 02, 2004 2:56 PM by slippman
            Comments
             
            Are there any plans to, ahem, extend std::string to include constructors and extraction methods for String^, like ATL::CString currently has? 
            As a sidenote, this is not the first time I find myself wanting one or two features from CString in std::string, to make the decision for which of the two classes to use for a native Windows C++ application a bit easier... 
            Either way, I'm really looking forward to the new C++/CLI. Actually, the /clr switch works amazingly well even today.
            June 3, 2004 10:27 AM
             
            In Whidbey we'll be supplying much more direct approach to do this type of marshalling via a library. 

            void F( String^ s ) 

            string s1 = marshal_to<string>( s ); 
            String^ s2 = marshal_to<String^>( s1 ); 


            If you already have a char*, and want to get a System::String from it, all you have to do is this: 

            void F( const char* s ) 

            String^ s1 = gcnew String( s ); 
            }
            June 4, 2004 3:01 PM
             
            as david larsson's ahem indicates, extending the standard ISO-C++ string independent of a standard's body is, i think, unlikely at this point. however, as anson's mail indicates, there is lots of thought being given on how to help users interoperate between the native and managed platforms, and david's request for support in this is not at all unreasonable.
            June 17, 2004 9:26 AM
             
            Yves Dolce -- the conscience of the blogs -- rightly pointed out that they two conversion samples needlessly prolong the pinning of the internal System::Char array of the String, and has proposed the following preferred alternatives, 

            bool To_CharStar( String^ source, char*& target ) 



            int len = (( source->Length+1) * 2); 

            target = new char[ len ]; 

            pin_ptr<const wchar_t> wch = PtrToStringChars( source ); 

            return wcstombs( target, wch, len ) != -1; 





            bool To_string( String^ source, string &target ) 



            int len = (( source->Length+1) * 2); 

            char *ch = new char[ len ]; 

            bool result ; 



            pin_ptr<const wchar_t> wch = PtrToStringChars( source ); 

            result = wcstombs( ch, wch, len ) != -1; 



            target = ch; 

            delete ch; 

            return result; 



            June 17, 2004 12:16 PM
             
            In To_string(), shouldn't 

            delete ch; 

            actually be 

            delete[] ch; 

            Since you're allocating an array, you really should use the array deletion expression...
            July 2, 2004 5:00 AM
             
            you are correct. it is a bad habit for an old dog who was programming with the language before this was added, and of course in current implementations, its absence is actually both non-fatal and possibly more efficient.
            July 7, 2004 11:39 AM
            Anonymous comments are disabled
            posted on 2008-11-06 17:31 BeyondCN 閱讀(4610) 評論(1)  編輯 收藏 引用 所屬分類: .NET
            久久青青草视频| 久久精品一区二区国产| 久久久久av无码免费网| 伊人久久大香线蕉综合影院首页| 2021国产精品久久精品| 久久99精品久久只有精品| 99久久国产免费福利| 亚洲国产成人久久综合一区77| 久久棈精品久久久久久噜噜| 久久无码人妻精品一区二区三区| 亚洲精品无码久久久久久| 久久久久久一区国产精品| 欧美一区二区三区久久综| 久久久久亚洲AV无码专区首JN | 99久久国产亚洲综合精品| 国产一久久香蕉国产线看观看| 亚洲色欲久久久久综合网| 久久精品国产一区| 成人午夜精品无码区久久| 久久99精品久久久久久秒播| 青青青青久久精品国产h| 久久久久99这里有精品10 | 久久精品中文字幕一区| 国内精品久久久久久久久| 99久久99这里只有免费费精品| 久久一本综合| 国产69精品久久久久9999| 香蕉久久一区二区不卡无毒影院 | 久久99精品久久久久久秒播| 精品无码久久久久久午夜| 亚洲成色www久久网站夜月| 漂亮人妻被中出中文字幕久久| 久久国产精品免费一区二区三区 | 午夜精品久久久久久影视riav| 国产精品久久波多野结衣| 97精品久久天干天天天按摩| 亚洲精品无码专区久久久| 亚洲中文久久精品无码ww16| 国产精品久久久久久久app| 国产精品久久久久久久久软件 | 99久久无码一区人妻a黑|