Post a small, complete example of code which causes the error. the pointer was placed because QT gives me error and suggest to do that i have error on line const QbyteArray ba: That is no reason to do it like this. How to convert string to const unsigned char* ? - C / C++ Qstring to unsigned char conversion function. ur reply is also helpful to me! Some options: If you cannot change the type of input and do need a unsigned char* and you still must avoid reinterpret cast, then you could create the std::basic_string from the input using the transform view. Convert string to unsigned integer Parses str interpreting its content as an integral number of the specified base, which is returned as an unsigned long value. stoull If idx is not a null pointer, the function also sets the value of idx to the position of the first character in str after the number. C++ style cast from unsigned char * to const char *. @shokarta said in Qstring to unsigned char conversion function: can you please show the function signature of that function? Your browser does not seem to support JavaScript. Making statements based on opinion; back them up with references or personal experience. None of these parameters is const, so that means the function can modify in, key, and iv (not sure if it does modify these parameters, but it could). std::cout << c; return 0; } Download Run Code. if I get it right, all you want to do is to convert the array plain [] to a hexadecimal string. That is because the return value does not match the functions signature. Using string::c_str function Using a not widely used lib or modifying it yourself is just a hazard game. Although it may be too late, thx a lot! Spying on a smartphone remotely by the authorities: feasibility and operation, Defining states on von Neumann algebras from filters on the projection lattices. The CStringA meythod works, but only because of the (dangerous IMHO) conversion feature build into CString.I would just do: What reply? Seems more like a generic buffer. This topic has been deleted. (Ep. stoul Convert std::string to const char* in C++ | Techie Delight Accessing inactive union member and undefined behavior? The c_str () function is used to return a pointer to an array that contains a null-terminated sequence of characters representing the current value of the string. Generally problem comes when Unicode characterset was enabled in your project. I'd be curious to see the function. strcpy_s(g_sXPS8ServerAddress, numberOfElements, buf. Convert String to Char Array in C++ To learn more, see our tips on writing great answers. Hi, I have written this code, and at the end, I am trying to write a vector of strings into a text file. Better explain first why you need const unsigned char * at all, then we can find a solution. If you want to use security functions, you should stick with well known and good tested libraries like openssl. const char* c_str () const; If there is an exception thrown then there are no changes in the string. This forum has migrated to Microsoft Q&A. So, your code will work in both ANSI/MBCS and Unicode builds (Unicode build is the default build settingsince Visual C++ 2005). ChatGPT) is banned, Testing native, sponsored banner ads on Stack Overflow (starting July 6). Convert string to const char* in C++ - thisPointer I tried the above methods but it is failing as my project character set should support unicode also, But in that context the text in CString is normal ANSI characters only. If we have predefined string length, then we can use this method. Alternatively, I expect a blabla () function as the following: string str = "Hello"; const unsigned char* ptr = blabla (str); Thanks. Connect and share knowledge within a single location that is structured and easy to search. arduino ide - Cannot convert 'String' to 'uint8_t {aka unsigned char Using strcpy () function. - SergeyA Sep 8, 2021 at 14:08 Add a comment 2 Answers Sorted by: Why add an increment/decrement operator when compound assignments exist? Convert String to const unsigned char - Displays - Arduino Forum basicaly i hae dowloaded and used huge function to AES encode and decode string. 2. Quote>I have this message error : error C2440: 'type cast' : Quote>cannot convert from 'CString' to 'char *'. Ask Question Asked 7 years, 7 months ago Modified 7 years, 7 months ago Viewed 10k times 6 What would be the code to convert an std::string to unsigned char* and back? https://forum.qt.io/topic/113070/qt-code-of-conduct. But this has potential overhead, so consider whether avoiding reinterpret_cast is worth it. Here, the idea is to pass the const char* returned by the string::c_str or string::data functions to the strcpy () function, which internally copies it into the specified character array and returns a pointer it. yabansu 14 Hi, I just want to know if there is a way of converting a string variable into a const unsigned char pointer. Yes. When I debug this programm, it stop on the. unsigned short i, length;BYTE ByteBuffer [128]={0};TCHAR szCString [256]={0}; wsprintf(szCString,TEXT("%s"),szYourCStringString); i = 0;length = lstrlen(szCString);if (length && length < sizeof(ByteBuffer)){ do{ ByteBuffer=(BYTE)(TCHAR)szCString; }while (++i < length);}, ////SendCharStringToYourFunction((char*)ByteBuffer));//. You can use it within the function, but not outside. You'd have to do this anyway, even for the next step. Why? void f(const char* s){ std::cout << s << std::endl;}CString str = _T("Testing");f(CT2CA(str)); Suneel:Some of the answers in this thread are wrong, and others seem overly complicated. the local variable is destroyed when you leave the function. Thanks for contributing an answer to Stack Overflow! Cannot convert 'const char*' to 'unsigned char* If UNICODE is not defined LPCTSTR and LPCSTR are the same. The Arduino reads the data and tramnsmits it over BLE so you can plot the Data on your smartphone. The strings types that are covered include char *, wchar_t*, _bstr_t, CComBSTR, CString, basic_string, and System.String. if you want to develop code that builds fine on both ANSI/MBCS and Unicode builds), you should use CString, and you should use TCHAR instead of char, and _tcscpy_s instead of strcpy_s: I think that in your original code you defined your g_sXPS8ServerAddress as a char * string, maybe something like this: char g_sXPS8ServerAddress[ MAX_STRING_LENGTH ]; then you should change this definition to (using TCHAR): and your C++ code to copy the buffer into g_sXPS8ServerAddress should be: _countof( g_sXPS8ServerAddress ), // number of elements. For skilled one it could be matrer of several minutes only :/. NoScript). Eligibility criteria to become the prime minister of India and what is "office of profit"? Note the use of _countof to get the correctnumber of elements (expressed in count of char's in ANSI/MBCS builds, and in count of wchar_t's in Unicode builds). use strtol () or strtoul () for example (or strtoull () if you need an unsigned long long) Can I still have hopes for an offer as a software developer. e.g. Are there nice walking/hiking trails around Shibu Onsen in November? Convert std::string to const char* in C++ This post will discuss how to convert a std::string to const char* in C++. strcpy_s(g_sXPS8ServerAddress, numberOfElements, buf); Instead, if you want to code in a Unicode-neutral format (i.e. while ((*p++ = *_SRC++) != 0 && --available > 0). If UNICODE is not defined LPCTSTR and LPCSTR are the same. How can I learn wizard spells as a warlock without multiclassing? Convert from std::string to unsigned char* - C / C++ Convert String to const unsigned char coderx06 September 25, 2021, 12:46pm 1 String abc ="0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff"; const unsigned char displaydata []= {reinterpret_cast<const unsigned char*> (abc.c_str ())}; display.drawBitmap (displaydata, startX, startY, bmpWidth, bmpHeight, GxEPD_WHITE); Since you can get the length of the string using str.GetLength(), you can dynamically assign the cstr buffer using new or malloc to. This article shows how to convert various Visual C++ string types into other strings. If you only need an iterator to unsigned char and not necessarily a pointer, then you could use, You could change the function that expects. Unsolved Qstring to unsigned char conversion function I'm not an avoid fan of MFC, nor have I used it the last 6 or 7 years, but I seem to recall that you can cast it directly (it should have a user defined conversion operator). I have variable input type const std::string&: Now I need to convert this to const unsigned char* because this is the input of the function. Consider this: uint32_t payload = 0x00323130; The first line initializes a 32 bit int to a specific value, 0x00323130 in hex. 587), The Overflow #185: The hardest part of software is requirements, Starting the Prompt Design Site: A New Home in our Stack Exchange Neighborhood, Temporary policy: Generative AI (e.g. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. https://github.com/SergeyBel/AES/blob/master/README.md. As soon as you want the data you just walk by with your smartphone, connect over BLE and chose one of the folders availible on the SD Card. When are complicated trig functions used? The only reason I can come up with for you not being able to cast it is that you are compiling your application for unicode. How to convert a std::string to const char* or char* it is supposed to convert it to hex Do you mean that the string "1234" needs to become the number 0x1234? I need a routine like: std::string nth_word (const std::string &s, unsigned int n) { // return n-th word from the string, n is 0-based // if 's' contains too few words, return "" //. unsigned char *out = aes.EncryptCBC(StringToChat(plain), BLOCK_BYTES_LENGTH, StringToChat(key), StringToChat(iv), len); @aha_1980 @shokarta That said, I'm not even sure if Qt SLL would provide something useful for you. char *cstr = str.GetBuffer(str.GetLength()); http://www.codeguru.com/forum/showthread.php?t=85534. Only users with topic management privileges can see it. But if we enable Unicode in the project, then the above mentioned methods will not work. Convert String to const unsigned char - Arduino Stack Exchange Quote>Suppose if we have a string larger than MAX_LENGTH, then this method will fail to copy. But again: you cannot return a pointer to a local variable! Simply use these functions the way they are supposed to be used. Invalid conversion from 'const unsigned char*' to 'const char Let's see an example, If Unicode not enabled, below mentioned procedures will work. Any chance you and i can have any deal on that? We can call this function to get a const char* to the characters in the string. Context : Data is lying an an sd Card in the arduino. Do you want the ASCII value of the character or do you want to parse the string contents as a number? const char* is LPCSTR. Is there a good way to convert from unsigned char* to char*? Convert a std::string to char* in C++ There is a LPCTSTR operator defined for CString. cannot convert 'String' to 'uint8_t {aka unsigned char}' in initialization. Python zip magic for classes instead of tuples, Asymptotic behaviour of an integral with power and exponential functions. you're assigning a pointer to a single character. yabansu Dec 27 '06 # 1 * in order to put inside the signature not unsigned char but qstring directly? Iwould suggest trying this simple MFC-based method of conversion from Unicode: Yes. How can I convert a string to a const unsigned char*? str = "1234567891234567" unsigned char* unsignedStr = ConvertStrToUnsignedCharPointer (str); str1 = ConvertUnsignedCharToStr (unsignedStr); Please include an example string from the servers answer to the request. Now let's assume that payload was stored in memory at address 0x0100. Also, https://github.com/SergeyBel/AES/blob/master/README.md shows how to use the functions. That means, you have to create local buffers for these parameters, and copy the data into the buffers. Either use QString str or (better) const QString &str as parameter. Converting a string to an const unsigned char* - C / C++ I find it odd that a function expecting a C-string would want unsigned chars. Have you tried this? Find centralized, trusted content and collaborate around the technologies you use most. The other way round can be done with QByteArray::fromHex (): const QString s = "0123456789ABCDEF" ; const . It returns a const char pointer to the null terminated contents of the string. ). To strictly answer your question, there's this way: Is this any better than a reinterpret_cast? Would it be very dificult to modify those aes. Quote>It can't debug, and it stop on this line. Tested solution: Since gcc disallows conversion unsigned char* to const char* and vice versa, I therefore replaced methods EVP_PKEY_CTX_set1_pbe_pass and EVP_PKEY_derive params out.data() and password.data() cast to const char* and unsigned char*. In all cases, a copy of the string is made when converted to the new type. If youn want a String object, than you just need to assign the char array to your String object like this myStringObj = dta;. 1 How exactly is the server giving you the binary data? - chrisl Sep 25, 2021 at 14:19 With const unsigned char displaydata= {reinterpret_cast<const unsigned char*> (. main.cpp:25:12: error: cannot initialize return object of type 'unsigned char' with an lvalue of type 'const unsigned char *'. We can enable/disable Unicode by changing the Character Set property of the project. the better question is: Is this worse than, More than likely this will never fail, as all it is doing is a, How to convert string to const unsigned char* without using reinterpret_cast (modern approach), Why on earth are people paying for digital real estate? char buffer [32]; sprintf (buffer, " {data:%d}", payload); Then send buffer via a function that expects a C string. You can only copy the result into a buffer provided from outside. Type cast from unsigned const char * to char const *, Converting from C++ string to unsigned char* and back. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Output: std::string to char*. Convert unsigned char to String - General - Particle You can easily do this with: QString s = QByteArray(reinterpret_cast(plain)).toHex() instead your complicated function. What are the advantages and disadvantages of the callee versus caller clearing the stack after a call? Fix it please. Check the. Compliant Solution In this compliant solution, the result of the expression *c_str++ is cast to unsigned char before assignment to the int variable c: https://github.com/SergeyBel/AES, i have done no futher changes on these files, unsigned char *AES::EncryptCBC(unsigned char in[], unsigned int inLen, unsigned char key[], unsigned char * iv, unsigned int &outLen). STR34-C. Cast characters to unsigned char before converting to larger (string::c_str () converts the string to a signed char) As noted by Juha, a reinterpret_cast is safe and fine, but a question is whether you must convert to unsigned char const * (I presume that you want to preserve the constness! Apparently type punning with an union is UB so definitely don't do this. Sorry, I missed a star, I meant const unsigned char *plain = reinterpret_cast(ba.constData()); const unsigned char result = reinterpret_cast(ba.constData()); Over the years I have found it's often a good idea to write wrapper functions/classes for more or less every external library one uses, for all sorts of reasons. As a result, your viewing experience will be diminished, and you have been placed in read-only mode. String to const char* using "string.c_str ();" Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Suppose if we have a string larger than MAX_LENGTH, then this method will fail to copy. You should have been able to work out a solution based on the infoin the other posts in this thread.
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convert string to const unsigned char
convert string to const unsigned char
