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  • inline and member initializers

    - by Alexander
    When should I inline a member function and when should I use member initializers? My code is below.. I would like to modify it so I could make use some inline when appropriate and member initializers: #include "Books.h" Book::Book(){ nm = (char*)""; thck = 0; wght = 0; } Book::Book(const char *name, int thickness, int weight){ nm = strdup(name); thck = thickness; wght = weight; } Book::~Book(){ } const char* Book::name(){ return nm; } int Book::thickness(){ return thck; } int Book::weight(){ return wght; } // // Prints information about the book using this format: // "%s (%d mm, %d dg)\n" // void Book::print(){ printf("%s (%d mm, %d dg)\n", nm, thck, wght); } Bookcase::Bookcase(int id){ my_id = id; no_shelf = 0; } int Bookcase::id(){ return my_id; } Bookcase::~Bookcase(){ for (int i = 0; i < no_shelf; i++) delete my_shelf[i]; } bool Bookcase::addShelf(int width, int capacity){ if(no_shelf == 10) return false; else{ my_shelf[no_shelf] = new Shelf(width, capacity); no_shelf++; return true; } } bool Bookcase::add(Book *bp){ int index = -1; int temp_space = -1; for (int i = 0; i < no_shelf; i++){ if (bp->weight() + my_shelf[i]->curCapacity() <= my_shelf[i]->capacity()){ if (bp->thickness() + my_shelf[i]->curWidth() <= my_shelf[i]->width() && temp_space < (my_shelf[i]->width() - my_shelf[i]->curWidth())){ temp_space = (my_shelf[i]->width()- my_shelf[i]->curWidth()); index = i; } } } if (index != -1){ my_shelf[index]->add(bp); return true; }else return false; } void Bookcase::print(){ printf("Bookcase #%d\n", my_id); for (int i = 0; i < no_shelf; i++){ printf("--- Shelf (%d mm, %d dg) ---\n", my_shelf[i]->width(), my_shelf[i]->capacity()); my_shelf[i]->print(); } }

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  • Endianness conversion and g++ warnings

    - by SuperBloup
    I've got the following C++ code : template <int isBigEndian, typename val> struct EndiannessConv { inline static val fromLittleEndianToHost( val v ) { union { val outVal __attribute__ ((used)); uint8_t bytes[ sizeof( val ) ] __attribute__ ((used)); } ; outVal = v; std::reverse( &bytes[0], &bytes[ sizeof(val) ] ); return outVal; } inline static void convertArray( val v[], uint32_t size ) { // TODO : find a way to map the array for (uint32_t i = 0; i < size; i++) for (uint32_t i = 0; i < size; i++) v[i] = fromLittleEndianToHost( v[i] ); } }; Which work and has been tested (without the used attributes). When compiling I obtain the following errors from g++ (version 4.4.1) || g++ -Wall -Wextra -O3 -o t t.cc || t.cc: In static member function 'static val EndiannessConv<isBigEndian, val>::fromLittleEndianToHost(val)': t.cc|98| warning: 'used' attribute ignored t.cc|99| warning: 'used' attribute ignored || t.cc: In static member function 'static val EndiannessConv<isBigEndian, val>::fromLittleEndianToHost(val) [with int isBigEndian = 1, val = double]': t.cc|148| instantiated from here t.cc|100| warning: unused variable 'outVal' t.cc|100| warning: unused variable 'bytes' I've tried to use the following code : template <int size, typename valType> struct EndianInverser { /* should not compile */ }; template <typename valType> struct EndianInverser<4, valType> { static inline valType reverseEndianness( const valType &val ) { uint32_t castedVal = *reinterpret_cast<const uint32_t*>( &val ); castedVal = (castedVal & 0x000000FF << (3 * 8)) | (castedVal & 0x0000FF00 << (1 * 8)) | (castedVal & 0x00FF0000 >> (1 * 8)) | (castedVal & 0xFF000000 >> (3 * 8)); return *reinterpret_cast<valType*>( &castedVal ); } }; but it break when enabling optimizations due to the type punning. So, why does my used attribute got ignored? Is there a workaround to convert endianness (I rely on the enum to avoid type punning) in templates?

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  • Why wont my while loop wont take new input (c++)

    - by Van
    I've written a program to get a string input from a user and parse it into tokens and move a robot according to the input. My problem is trying to issue more than one command. The code looks like: void Navigator::manualDrive() { const int bufSize = 42; char uinput[bufSize]; char delim[] = " "; char *token; while(true) { Navigator::parseInstruction(uinput); } } /* parseInstruction(char *c) -- parses cstring instructions received * and moves robot accordingly */ void Navigator::parseInstruction(char * c) { const int bufSize = 42; char uinput[bufSize]; char delim[] = " "; char *token; cout << "Enter your directions below: \n"; cin.ignore(); cin.getline (uinput, bufSize); token=strtok(uinput, delim); if(strcmp("forward", token) == 0) { int inches; token = strtok(NULL, delim); inches = atoi (token); Navigator::travel(inches); } if(strcmp("back",token) == 0) { int inches; token = strtok(NULL, delim); inches = atoi (token); double value = fabs(0.0735 * fabs(inches) - 0.0550); myRobot.backward(1/*speed*/, value/*time*/); } if(strcmp("turn",token) == 0) { int degrees; token = strtok(NULL, delim); if(strcmp("left",token) == 0) { token = strtok(uinput, delim); degrees = atoi (token); double value = fabs(0.0041 * degrees - 0.0523); myRobot.turnLeft(1/*speed*/, value/*time*/); } } if(strcmp("turn",token) == 0) { int degrees; token = strtok(NULL, delim); if(strcmp("right",token) == 0) { token = strtok(uinput, delim); degrees = atoi (token); double value = fabs(0.0041 * degrees - 0.0523); myRobot.turnRight(1/*speed*/, value/*time*/); } } if(strcmp("stop",token) == 0) { myRobot.motors(0,0); } } In the function manualDrive I have a while loop calling the function parseInstruction infinitely. The program outputs "Enter your directions below: " When I give the program instructions it executes them, and then it outputs "enter your directions below: " again and when I input my directions again it does not execute them and outputs "Enter your directions below: " instead. I'm sure this is a very simple fix I'm just very new to c++. So if you could please help me out and tell me why the program only takes the first set of directions. thanks

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  • How does one smooth an image used as a control skin?

    - by kevmoo
    I'm embedding an image like this: [Embed(source="/tool_deleteUp.png")] private static const c_deleteButton_styleUp:Class; I'm using it like this: _removeButton = new Button(); _removeButton.setStyle('upSkin', c_deleteButton_styleUp); When I rotate the button, the image doesn't scale smoothly. I know the tricks one uses to scale an image loaded in an Image control, but I'm banging my head against a wall trying to figure out how to do it here. Help!

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  • What is an overloaded operator in c++?

    - by Jeff
    I realize this is a basic question but I have searched online, been to cplusplus.com, read through my book, and I can't seem to grasp the concept of overloaded operators. A specific example from cplusplus.com is: // vectors: overloading operators example #include <iostream> using namespace std; class CVector { public: int x,y; CVector () {}; CVector (int,int); CVector operator + (CVector); }; CVector::CVector (int a, int b) { x = a; y = b; } CVector CVector::operator+ (CVector param) { CVector temp; temp.x = x + param.x; temp.y = y + param.y; return (temp); } int main () { CVector a (3,1); CVector b (1,2); CVector c; c = a + b; cout << c.x << "," << c.y; return 0; } from http://www.cplusplus.com/doc/tutorial/classes2/ but reading through it I'm still not understanding them at all. I just need a basic example of the point of the overloaded operator (which I assume is the "CVector CVector::operator+ (CVector param)"). There's also this example from wikipedia: Time operator+(const Time& lhs, const Time& rhs) { Time temp = lhs; temp.seconds += rhs.seconds; if (temp.seconds >= 60) { temp.seconds -= 60; temp.minutes++; } temp.minutes += rhs.minutes; if (temp.minutes >= 60) { temp.minutes -= 60; temp.hours++; } temp.hours += rhs.hours; return temp; } from "http://en.wikipedia.org/wiki/Operator_overloading" The current assignment I'm working on I need to overload a ++ and a -- operator. Thanks in advance for the information and sorry about the somewhat vague question, unfortunately I'm just not sure on it at all.

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  • C# hash password create salt question

    - by 5YrsLaterDBA
    If I create salt by using something like this: public class User { private const int Hash_Salt_Length = 8; private byte[] saltBytes = new byte[Hash_Salt_Length]; public User() { RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider(); rng.GetNonZeroBytes(saltBytes); } .... } The saltBytes bytes array will be different for each session (restart the application). How can I check password to allow user login our application?

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  • decltype, result_of, or typeof?

    - by Neil G
    I have: class A { public: B toCPD() const; And: template<typename T> class Ev { public: typedef result_of(T::toCPD()) D; After instantiating Ev<A>, the compiler says: meta.h:12: error: 'T::toCPD' is not a type neither decltype nor typeof work either.

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  • g++ compiler complains about conversions between related types (from int to enum, from void* to clas

    - by Slav
    g++ compiler complains about conversions between related types (from int to enum, from void* to class*, from const char* to unsigned char*, etc.). Compiler handles such convertions as errors and won't compile furthermore. It occurs only when I compile using Dev-C++ IDE, but when I compile the same code (using the compiler which Dev-C++ uses) such errors (even warnings) do not appears. How to mute errors of such types?

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  • How to generate correlated binary variables

    - by jonalm
    Dear All I need to generate a series of N random binary variables with a given correlation function. Let x = {x_i} be a series of binary variables (taking the value 0 or 1, i running form 1 to N). The marginal probability is given Pr(x_i = 1) = p, and the values should be correlated in the following way E[ x_i x_j ] = const * |i-j|^-alfa where alfa is a positive number. Is it possible to generate a series like this? preferably in python.

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  • Can I use a binary literal in C or C++?

    - by hamza
    I need to work with a binary number. I tried writing: const x = 00010000 ; But it didn't work. I know that I can use an hexadecimal number that has the same value as 00010000 but I want to know if there is a type in C++ for binary numbers & if there isn't, is there another solution for my problem?

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  • Is there an open source immutable dictionary for C#, with fast 'With/Without' methods?

    - by Strilanc
    I'm looking for a proper C# immutable dictionary, with fast update methods (that create a partial copy of the dictionary with slight changes). I've implemented one myself, using zippers to update a red-black tree, but it's not particularly fast. By 'immutable dictionary' I don't just mean readonly or const. I want something that has reasonably fast 'With' and 'Without', or equivalent, methods that return a thing with slight modifications without modifying the original. An example from another language is map in Scala

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  • infix operation to postfix using stacks

    - by Chris De La O
    We are writing a program that needs to convert an infix operation (4 5/3) to postfix (4 5 3 / ) using stacks. however my convert to postfix does not work as it doesnt not output the postFix array that is supposed to store the conversion from infix notation to postfix notation. here is the code for the convertToPostix fuction. //converts infix expression to postfix expression void ArithmeticExpression::convertToPostfix(char *const inFix, char *const postFix) { //create a stack2 object named cow Stack2<char> cow; cout<<postFix; char thing = '('; //push a left parenthesis onto the stack cow.push(thing); //append a right parenthesis to the end of inFix array strcat(inFix, ")"); int i = 0;//declare an int that will control posFix position //if the stack is not empty if (!cow.isEmpty()) { //loop to run until the last character in inFix array for (int x = 0; inFix[x]!= '\0'; x++ ) { //if the inFix element is a digit if (isdigit(inFix[x])) { postFix[i]=inFix[x];//it is assigned to the next element in postFix array i++;//move on to next element in postFix } //if the inFix element is a left parenthesis else if (inFix[x]=='(') { cow.push(inFix[x]);//push it unto the stack } //if the inFix element is an operator else if (isOperator(inFix[x])) { char oper2 = inFix[x];//char variable holds inFix operator if (isOperator(cow.stackTop()))//if the top node in the stack is an operator { while (isOperator(cow.stackTop()))//and while the top node in the stack is an operator { char oper1 = cow.stackTop();//char variable holds node operator if(precedence( oper1, oper2))//if the node operator has higher presedence than node operator { postFix[i] = cow.pop();//we pop such operator and insert it in postFix array's next element cow.push(inFix[x]);//and push inFix operator unto the stack i++;//move to the next element in posFix } } } //if the top node is not an operator //we push the current inFix operator unto the top of the stack else cow.push(inFix[x]); } //if the inFix element is a right parenthesis else if (inFix[x]==')') { //we pop everything in the stack and insert it in postFix //until we arrive at a left paranthesis while (cow.stackTop()!='(') { postFix[i] = cow.pop(); i++; } //we then pop and discard left parenthesis cow.pop(); } } postFix[i]='\0'; //print !!postFix array!! (not stack) print();//code for this is just cout<<postFix; }

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  • How can I break if gdb is attached, but continue if it is not?

    - by Michael Anderson
    I have some debugging code that if executed while running with GBD attached should break the execution of the application, but if GDB is not running it should continue. The code I'm working with looks something like this in structure: try { if( some_complex_expression ) { gdb_should_berak_here(); do_some_stuff(); throw MyException(); } } catch( const MyException & e ) { handle_exception_and_continue(); } What should gdb_should_break_here be?

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  • C++ Thread level constants

    - by Gokul
    Is there a way by which we can simulate thread level constants in C++? For example, if i have to make a call to template functions, then i need to mention the constants as template level parameters? I can use static const variables for template metaprogramming, but they are process level constants. I know, i am asking a question with a high probability of 'No'. Just thought of asking this to capitalize on the very rare probability :)) Thanks, Gokul.

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  • Registry key editing vb6 startup

    - by Francesco D.
    Is it possible that someone here could explain how to use this code. Please keep in mind i am a complete amateur, so simplifications may be needed. Private Const cPGM = "C:\VB Forum\startup\Example.exe" Dim oShell As IWshShell_Class Set oShell = New IWshShell_Class oShell.RegWrite "HKLM\Software\Microsoft\Windows\CurrentVersion\Run\MyVBApp", _ cPGM, "REG_SZ" How exactly is this code used? Is it saved as an .exe file and ran or what? Thanks for your prompt reply and informational feedback.

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  • emacs: how do I use edebug on code that is defined in a macro?

    - by Cheeso
    I don't even know the proper terminology for this lisp syntax, so I don't know if the words I'm using to ask the question, make sense. But the question makes sense, I'm sure. So let me just show you. cc-mode (cc-fonts.el) has things called "matchers" which are bits of code that run to decide how to fontify a region of code. That sounds simple enough, but the matcher code is in a form I don't completely understand, with babckticks and comma-atsign and just comma and so on, and furthermore it is embedded in a c-lang-defcost, which itself is a macro. And I want to run edebug on that code. Look: (c-lang-defconst c-basic-matchers-after "Font lock matchers for various things that should be fontified after generic casts and declarations are fontified. Used on level 2 and higher." t `(;; Fontify the identifiers inside enum lists. (The enum type ;; name is handled by `c-simple-decl-matchers' or ;; `c-complex-decl-matchers' below. ,@(when (c-lang-const c-brace-id-list-kwds) `((,(c-make-font-lock-search-function (concat "\\<\\(" (c-make-keywords-re nil (c-lang-const c-brace-id-list-kwds)) "\\)\\>" ;; Disallow various common punctuation chars that can't come ;; before the '{' of the enum list, to avoid searching too far. "[^\]\[{}();,/#=]*" "{") '((c-font-lock-declarators limit t nil) (save-match-data (goto-char (match-end 0)) (c-put-char-property (1- (point)) 'c-type 'c-decl-id-start) (c-forward-syntactic-ws)) (goto-char (match-end 0))))))) I am reading up on lisp syntax to figure out what those things are and what to call them, but aside from that, how can I run edebug on the code that follows the comment that reads ;; Fontify the identifiers inside enum lists. ? I know how to run edebug on a defun - just invoke edebug-defun within the function's definition, and off I go. Is there a corresponding thing I need to do to edebug the cc-mode matcher code forms?

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  • passing a class method as opposed to a function in std::sort

    - by memC
    hi, Within a class, I am trying to sort a vector, by passing a method of the same class. But it gives errors at the time of compilation. Can anyone tell what the problem is? Thank you! it gives the following error: argument of type bool (Sorter::)(D&, D&)' does not matchbool (Sorter::*)(D&, D&)' I have also tried using sortBynumber(D const& d1, D const& d2) #include<vector> #include<stdio.h> #include<iostream> #include<algorithm> class D { public: int getNumber(); D(int val); ~D(){}; private: int num; }; D::D(int val){ num = val; }; int D::getNumber(){ return num; }; class Sorter { public: void doSorting(); bool sortByNumber(D& d1, D& d2); std::vector<D> vec_D; Sorter(); ~Sorter(){}; private: int num; }; Sorter::Sorter(){ int i; for ( i = 0; i < 10; i++){ vec_D.push_back(D(i)); } }; bool Sorter::sortByNumber(D& d1, D& d2){ return d1.getNumber() < d2.getNumber(); }; void Sorter::doSorting(){ std::sort(vec_D.begin(), vec_D.end(), this->sortByNumber); }; int main(){ Sorter s; s.doSorting(); std::cout << "\nPress RETURN to continue..."; std::cin.get(); return 0; }

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  • [C++] std::string manipulation: whitespace, "newline escapes '\'" and comments #

    - by rubenvb
    Kind of looking for affirmation here. I have some hand-written code, which I'm not shy to say I'm proud of, which reads a file, removes leading whitespace, processes newline escapes '\' and removes comments starting with #. It also removes all empty lines (also whitespace-only ones). Any thoughts/recommendations? I could probably replace some std::cout's with std::runtime_errors... but that's not a priority here :) const int RecipeReader::readRecipe() { ifstream is_recipe(s_buffer.c_str()); if (!is_recipe) cout << "unable to open file" << endl; while (getline(is_recipe, s_buffer)) { // whitespace+comment removeLeadingWhitespace(s_buffer); processComment(s_buffer); // newline escapes + append all subsequent lines with '\' processNewlineEscapes(s_buffer, is_recipe); // store the real text line if (!s_buffer.empty()) v_s_recipe.push_back(s_buffer); s_buffer.clear(); } is_recipe.close(); return 0; } void RecipeReader::processNewlineEscapes(string &s_string, ifstream &is_stream) { string s_temp; size_t sz_index = s_string.find_first_of("\\"); while (sz_index <= s_string.length()) { if (getline(is_stream,s_temp)) { removeLeadingWhitespace(s_temp); processComment(s_temp); s_string = s_string.substr(0,sz_index-1) + " " + s_temp; } else cout << "Error: newline escape '\' found at EOF" << endl; sz_index = s_string.find_first_of("\\"); } } void RecipeReader::processComment(string &s_string) { size_t sz_index = s_string.find_first_of("#"); s_string = s_string.substr(0,sz_index); } void RecipeReader::removeLeadingWhitespace(string &s_string) { const size_t sz_length = s_string.size(); size_t sz_index = s_string.find_first_not_of(" \t"); if (sz_index <= sz_length) s_string = s_string.substr(sz_index); else if ((sz_index > sz_length) && (sz_length != 0)) // "empty" lines with only whitespace s_string.clear(); } Some extra info: the first s_buffer passed to the ifstream contains the filename, std::string s_buffer is a class data member, so is std::vector v_s_recipe. Any comment is welcome :)

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  • Should I consider memmove() O(n) or O(1) ?

    - by Andrei Ciobanu
    Hello, this may be a silly question, but I want to calculate the complexity of one of my algorithms, and I am not sure what complexity to consider for the memmove() function. Can you please help / explain ? void * memmove ( void * destination, const void * source, size_t num ); So is the complexity O(num) or O(1). I suppose it's O(num), but I am not sure as I lack for now the understanding of what's going on under the hood.

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  • Where can I find the IRQ number in request_irq function?

    - by sasayins
    Hi, Im learning device driver programming in Linux. And I'm wondering where I could the IRQ number in the request_irq function. int request_irq (unsigned int irq, void (*handler) (int, void *, struct pt_regs *), unsigned long irqflags, const char *devname, void *dev_id); In the irq parameter, what value or where could I find that value to put in the request_irq function? Thanks

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  • Qt inheriting from QGraphicsEllipseItem

    - by JHollanti
    I was trying to inherit from QGraphicsEllipseItem 'cause i wanted to add some functionality to it. However i was faced with this error, which probably has something to do with the compiler/precompiler or moc? error: 'staticMetaObject' is not a member of 'QGraphicsEllipseItem' And here's the class code: class MyEllipseItem : public QGraphicsEllipseItem { Q_OBJECT public: MyEllipseItem (const QRectF & outline) : QGraphicsEllipseItem(outline) { } };

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  • Implementing default constructors

    - by James
    Implement the default constructor, the constructors with one and two int parameters. The one-parameter constructor should initialize the first member of the pair, the second member of the pair is to be 0. Overload binary operator + to add the pairs as follows: (a, b) + (c, d) = (a + c, b + d); Overload the - analogously. Overload the * on pairs ant int as follows: (a, b) * c = (a * c, b * c). Write a program to test all the member functions and overloaded operators in your class definition. You will also need to write accessor (get) functions for each member. The definition of the class Pairs: class Pairs { public: Pairs(); Pairs(int first, int second); Pairs(int first); // other members and friends friend istream& operator>> (istream&, Pair&); friend ostream& operator<< (ostream&, const Pair&); private: int f; int s; }; Self-Test Exercise #17: istream& operator (istream& ins, Pair& second) { char ch; ins ch; // discard init '(' ins second.f; ins ch; // discard comma ',' ins second.s; ins ch; // discard final '(' return ins; } ostream& operator<< (ostream& outs, const Pair& second) { outs << '('; outs << second.f; outs << ", " ;// I followed the Author's suggestion here. outs << second.s; outs << ")"; return outs; }

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  • Problem with pointers and getstring function

    - by volting
    I am trying to write a function to get a string from the uart1. Its for an embedded system so I don't want to use malloc. The pointer that is passed to the getstring function seems to point to garbage after the gets_e_uart1() is called. I don't use pointers too often so I'm sure it is something really stupid and trivial that Im doing wrong. Regards, V int main() { char *ptr = 0; while(1) { gets_e_uart1(ptr, 100); puts_uart1(ptr); } return 0; }*end main*/ //------------------------------------------------------------------------- //gets a string and echos it //returns 0 if there is no error char getstring_e_uart1(char *stringPtr_, const int SIZE_) { char buffer_[SIZE_]; stringPtr_ = buffer_; int start_ = 0, end_ = SIZE_ - 1; char errorflag = 0; /*keep geting chars until newline char recieved*/ while((buffer_[start_++] = getchar_uart1())!= 0x0D) { putchar_uart1(buffer_[start_]);//echo it /*check for end of buffer wraparound if neccesary*/ if(start_ == end_) { start_ = 0; errorflag = 1; } } putchar_uart1('\n'); putchar_uart1('\r'); /*check for end of buffer wraparound if neccesary*/ if(start_ == end_) { buffer_[0] = '\0'; errorflag = 1; } else { buffer_[start_++] = '\0'; } return errorflag; } Update: I decided to go with approach of passing a pointer an array to the function. This works nicely, thanks to everyone for the informative answers. Updated Code: //------------------------------------------------------------------------- //argument 1 should be a pointer to an array, //and the second argument should be the size of the array //gets a string and echos it //returns 0 if there is no error char getstring_e_uart1(char *stringPtr_, const int SIZE_) { char *startPtr_ = stringPtr_; char *endPtr_ = startPtr_ + (SIZE_ - 1); char errorflag = 0; /*keep geting chars until newline char recieved*/ while((*stringPtr_ = getchar_uart1())!= 0x0D) { putchar_uart1(*stringPtr_);//echo it stringPtr_++; /*check for end of buffer wraparound if neccesary*/ if(stringPtr_ == endPtr_) { stringPtr_ = startPtr_; errorflag = 1; } } putchar_uart1('\n'); putchar_uart1('\r'); /*check for end of buffer wraparound if neccesary*/ if(stringPtr_ == endPtr_) { stringPtr_ = startPtr_; *stringPtr_ = '\0'; errorflag = 1; } else { *stringPtr_ = '\0'; } return errorflag; }

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