STR34-C. Cast characters to unsigned char before converting to larger Yes, I already tried, there is no error message. Method 1: Using string::c_str () function. Find centralized, trusted content and collaborate around the technologies you use most. Probably not. You should have been able to work out a solution based on the infoin the other posts in this thread. That said, I'm not even sure if Qt SLL would provide something useful for you. Are there nice walking/hiking trails around Shibu Onsen in November? Is it really in the format of your first string? Post a small, complete example of code which causes the error. There are two ways (I know two only)to solve this problem. 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. - SergeyA Sep 8, 2021 at 14:08 Add a comment 2 Answers Sorted by: Better explain first why you need const unsigned char * at all, then we can find a solution. Is a dropper post a good solution for sharing a bike between two riders? BTW: I would suggest to not use those old-style C arrays (like char/TCHAR something[MAX_LENGTH] and related old-style C functions, like strcpy_s), but insteadI would use CString (or CStringA or CStringW if you want to make it explicit that you need an ANSI/MBCS or Unicode string). Seems more like a generic buffer. yabansu Dec 27 '06 # 1 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*. We can call this function to get a const char* to the characters in the string. Connect and share knowledge within a single location that is structured and easy to search. In particular, only const_cast may be used to cast away (remove) constness or volatility. if I get it right, all you want to do is to convert the array plain [] to a hexadecimal string. The other way round can be done with QByteArray::fromHex (): const QString s = "0123456789ABCDEF" ; const . How can I convert a string to a const unsigned char*? In all cases, a copy of the string is made when converted to the new type. Please include an example string from the servers answer to the request. You can only copy the result into a buffer provided from outside. Way to get unsigned char into a std::string without reinterpret_cast? The correct way is to use reinterpret_cast. What are the advantages and disadvantages of the callee versus caller clearing the stack after a call? it is supposed to convert it to hex Do you mean that the string "1234" needs to become the number 0x1234? how to convert CString to const char If Unicode not enabled, below mentioned procedures will work. and using this function to convert it to QString: now I am trying to figure out SAME function to convert the QString again to unsigned char. Eligibility criteria to become the prime minister of India and what is "office of profit"? 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); Although it may be too late, thx a lot! Is there a good way to convert from unsigned char* to char*? How to convert string to const unsigned char* ? - C / C++ accommodate a string of virtually any size. the function is loaded by unsigned char: as well as it outputs the encrypted string in unsigned char, Hoewer because its a huge function which i understand just on basic logical concept i prefer not to use modify the function to insert string instead of char, as well as output, so i would prefer to convert it (i will be using this on many places, therefore the function is desired). Issues converting an uint32_t into a char* I find it odd that a function expecting a C-string would want unsigned chars. the local variable is destroyed when you leave the function. Invalid conversion from 'const unsigned char*' to 'const char Hi, I have written this code, and at the end, I am trying to write a vector of strings into a text file. This article shows how to convert various Visual C++ string types into other strings. Is it legal to intentionally wait before filing a copyright lawsuit to maximize profits? You can use wcstombs() method as below wcstombs(cstr, (TCHAR*)(const TCHAR*)str, MAX_LENGTH); But the disadvantage is string length is restricted to MAX_LENGTH. Visit Microsoft Q&A to post new questions. Using strcpy () function. 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. This topic has been deleted. Looks like your connection to Qt Forum was lost, please wait while we try to reconnect. 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));//. 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. Why? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Qstring to unsigned char conversion function. Now let's assume that payload was stored in memory at address 0x0100. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Check the. Spying on a smartphone remotely by the authorities: feasibility and operation, Defining states on von Neumann algebras from filters on the projection lattices. How to convert a std::string to const char* or char* 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. 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. char *cstr = str.GetBuffer(str.GetLength()); http://www.codeguru.com/forum/showthread.php?t=85534. * in order to put inside the signature not unsigned char but qstring directly? Using string::c_str function Would it be very dificult to modify those aes. 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. Is there any reason you cannot do this for your usage? Your code should look like this: CString str; const char* cstr = (LPCTSTR)str; however, I would put it like this: CString str; const TCHAR* cstr = (LPCTSTR)str; But if we enable Unicode in the project, then the above mentioned methods will not work. - Ignacio Vazquez-Abrams. Why add an increment/decrement operator when compound assignments exist? For skilled one it could be matrer of several minutes only :/. What is the significance of Headband of Intellect et al setting the stat to 19? (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! But again: you cannot return a pointer to a local variable! Convert a std::string to char* in C++ Any help would be great as I thought adding (String) . But this has potential overhead, so consider whether avoiding reinterpret_cast is worth it. Convert from std::string to unsigned char* - C / C++ e.g. Convert String to const unsigned char - Arduino Stack Exchange Either use QString str or (better) const QString &str as parameter. Iwould suggest trying this simple MFC-based method of conversion from Unicode: Yes. ChatGPT) is banned, Testing native, sponsored banner ads on Stack Overflow (starting July 6). 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: You can easily do this with: QString s = QByteArray (reinterpret_cast<const char*> (plain)).toHex () instead your complicated function. 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. Have you tried this? Not the answer you're looking for? return result; Note that you cannot do that! 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. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing, The correct way is using reinterpret_cast. Thanks for contributing an answer to Stack Overflow! 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. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. const char* is LPCSTR. https://forum.qt.io/topic/113070/qt-code-of-conduct. Also, https://github.com/SergeyBel/AES/blob/master/README.md shows how to use the functions. How to convert string to const unsigned char* ? If you want to use security functions, you should stick with well known and good tested libraries like openssl. main.cpp:25:12: error: cannot initialize return object of type 'unsigned char' with an lvalue of type 'const unsigned char *'. Heck, I don't even call the Qt classes/methods directly, I tend to provide wrappers for all of them! 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. 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). 1) Two possibly multilevel pointers to the same type may be converted between each other, regardless of cv-qualifiers at each level. unsigned char *out = aes.EncryptCBC(StringToChat(plain), BLOCK_BYTES_LENGTH, StringToChat(key), StringToChat(iv), len); @aha_1980 If youn want a String object, than you just need to assign the char array to your String object like this myStringObj = dta;. https://github.com/SergeyBel/AES/blob/master/README.md. Explanation Only the following conversions can be done with const_cast. On the initialization of the const char *. If we have predefined string length, then we can use this method. const char* c_str () const; If there is an exception thrown then there are no changes in the string. Your browser does not seem to support JavaScript. char * ) strings, you should use CStringA instead of CString. Edit 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. 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? Quote>But the disadvantage is string length is restricted to MAX_LENGTH. Please download a browser that supports JavaScript, or enable it if it's disabled (i.e. Implicit conversion from char** to const char**, convert String to type const char* using Arduino. 2. you're assigning a pointer to a single character. ur reply is also helpful to me! cannot convert 'String' to 'uint8_t {aka unsigned char}' in initialization. arduino ide - Cannot convert 'String' to 'uint8_t {aka unsigned char Simply use these functions the way they are supposed to be used. (Ep. Since you can get the length of the string using str.GetLength(), you can dynamically assign the cstr buffer using new or malloc to. You can use it within the function, but not outside. Context : Data is lying an an sd Card in the arduino. That means, you have to create local buffers for these parameters, and copy the data into the buffers. ). So, your code will work in both ANSI/MBCS and Unicode builds (Unicode build is the default build settingsince Visual C++ 2005). (Keeping the answer for posterity though!). Asking for help, clarification, or responding to other answers. Using Arduino Programming Questions gauravntpl August 16, 2017, 12:58pm 1 In the code I attached what I am trying to do is to save the "String password = "1234567890"; to EEPROM and than reading it from EEPROM.And after reading it from EEPROM I am converting it into "const char* pass2". Converting const unsigned Char* to String Python zip magic for classes instead of tuples, Asymptotic behaviour of an integral with power and exponential functions. std::cout << c; return 0; } Download Run Code. Output: std::string to char*. If you want a changed signature in a library, especially if it's just one function, the usual way is you write the desired wrapper function and go via that. The other way round can be done with QByteArray::fromHex(): many thanks for helping, so I have this then: which brings error on line const unsigned char: Convert String to const unsigned char - Displays - Arduino Forum When are complicated trig functions used? @shokarta said in Qstring to unsigned char conversion function: can you please show the function signature of that function? 1 You can do 2 static casts - one to the const void*, second from const void* to const unsigned char* It is also possible that a better container for you would be a vector of unsigned char, rather than std::string. Suppose if we have a string larger than MAX_LENGTH, then this method will fail to copy. its downloaded and used from here: rev2023.7.7.43526. Yes. On which line? stoull error: array initializer must be an initializer list or string literal.
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