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• ruby c extensions: character values over 127

  - by Adrian

  I am trying to make a C extension for Ruby that includes a method returning a string, which will sometimes have character values that need to be in an unsigned char. In http://github.com/shyouhei/ruby/blob/trunk/README.EXT, all of the functions listed for turning C strings into Ruby strings take signed chars. So I couldn't do this: unsigned char bytes[] = {0xf0, 0xf1, 0xf2}; return rb_str_new(bytes, 3); How could I make a method that returns these types of strings? In other words, how would I make a C extension with a method returning "\xff"?

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• Copying a java text file into a String.

  - by Deepak Konidena

  Hi, I run into the following errors when i try to store a large file into a string. Exception in thread "main" java.lang.OutOfMemoryError: Java heap space at java.util.Arrays.copyOf(Arrays.java:2882) at java.lang.AbstractStringBuilder.expandCapacity(AbstractStringBuilder.java:100) at java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:515) at java.lang.StringBuffer.append(StringBuffer.java:306) at rdr2str.ReaderToString.main(ReaderToString.java:52) As is evident, i am running out of heap space. Basically my pgm looks like something like this. FileReader fr = new FileReader(<filepath>); sb = new StringBuffer(); char[] b = new char[BLKSIZ]; while ((n = fr.read(b)) > 0) sb.append(b, 0, n); fileString = sb.toString(); Can someone suggest me why i am running into heap space error? Thanks.

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• Need help configuring SQL Server CE connections string in Fluent NHibernate

  - by Yoav

  Hi, I'm trying to return a session factory using this code: return Fluently.Configure() .Database(MsSqlCeConfiguration.Standard.ShowSql().ConnectionString(path)) .Mappings(m => m.FluentMappings.AddFromAssemblyOf<Project>()) .BuildSessionFactory(); Path is the full path to an .sdf file. And get this exception: System.ArgumentException: Format of the initialization string does not conform to specification starting at index 0. at System.Data.SqlServerCe.ConStringUtil.GetKeyValuePair(Char[] connectionString, Int32 currentPosition, String& key, Char[] valuebuf, Int32& vallength, Boolean& isempty) What am I doing wrong?

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• Is there an easy way to make `boost::ptr_vector` more debugger friendly in Visual Studio?

  - by Billy ONeal

  I'm considering using boost::ptr_container as a result of the responses from this question. My biggest problem with the library is that I cannot view the contents of the collection in the debugger, because the MSVC debugger doesn't recognize it, and therefore I cannot see the contents of the containers. (All the data gets stored as void * internally) I've heard MSVC has a feature called "debugger visualizers" which would allow the user to make the debugger smarter about these kinds of things, but I've never written anything like this, and I'm not hugely firmiliar with such things. For example, compare the behavior of boost::shared_ptr with MSVC's own std::tr1::shared_ptr. In the debugger (i.e. in the Watch window), the boost version shows up as a big mess of internal variables used for implementing the shared pointer, but the MSVC version shows up as a plain pointer to the object (and the shared_ptr's innards are hidden). How can I get started either using or implementing such a thing?

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• C++ input chaining in C#

  - by Monty

  I am trying to learn C# coming from C++. I am writing just some basic console stuff to get a feel for it and was wondering if it is possible to do simple chaining of inputs in C#. For example in C++: cout<<"Enter two numbers: "; cin >> int1 >> int2; You could then just input 3 5 and hit enter and the values will be fine. In C# however I have to split it up(as far as I can tell) like this: Console.Write("Enter the first number: "; int1 = (char)Console.Read(); Console.Writeline(""); Console.Write("Enter the second number: "; int2 = (char)Console.Read(); Maybe I am just missing something.

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• Can I mix compile time string comparison with MPL templates?

  - by Negative Zero

  I got this compile time string comparison from another thread using constexpr and C++11 (http://stackoverflow.com/questions/5721813/compile-time-assert-for-string-equality). It works with constant strings like "OK" constexpr bool isequal(char const *one, char const *two) { return (*one && *two) ? (*one == *two && isequal(one + 1, two + 1)) : (!*one && !*two); } I am trying to use it in the following context: static_assert(isequal(boost::mpl::c_str<boost::mpl::string<'ak'>>::value, "ak"), "should not fail"); But it gives me an compilation error of static_assert expression is not an constant integral expression. Can I do this?

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• JAVA: storing input into array

  - by Jann

  I need to write a program where the program would generate random letter and i would need to store this random character into an array char[] arrayRandom = new char[10]; for (int i = 0; i < 8; i++) { randomNumLet = (generator.nextInt(20) + 1); System.out.print(arrayRandomLetter[randomNumLet] + " "); arrayRandomLetter[randomNumLet] = arrayRandom[i]; } is there anything wrong with my code? because when i run this and printed the array i get boxes for all the values in the array and there are some letter that this line of code cannot print System.out.print(arrayRandomLetter[randomNumLet] + " "); Thanks

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• FreeRTOS, Eclipse IDE, and Syntax Errors

  - by MSumulong

  I have a slight annoyance when dealing with FreeRTOS code in Eclipse and I'm not sure if it's just me or if other people have this issue too but I see a lot of syntax errors highlighted in my code but it compiles/executes fine. The syntax errors seem to be caused by FreeRTOS specific code like: signed portCHAR *x; or vSemaphoreCreateBinary (semaphore); or signed portBASE_TYPE gpsTaskStart (void) { return xTaskCreate (vGPSTask, (const signed portCHAR * const) "GPS", configMINIMAL_STACK_SIZE, NULL, (tskIDLE_PRIORITY + 1), &taskHandles [TASKHANDLE_GPS]); } I was wondering if there was a way to configure Eclipse to parse this syntax properly.

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• Limiting input to specified regexp with uppercase chars in IE

  - by pixelboy

  I'm trying to limit what our users will be able to type in inputs, using javascript/jquery. Problem is, I have to limit this to Uppercase chars only, and numbers. Here's what I coded previously : $(input).keydown(function(e){ if ($(input).attr("class")=="populationReference"){ var ValidPattern = /^[A-Z_0-9]*$/; var char = String.fromCharCode(e.charCode); if (!ValidPattern.test(char) && e.charCode!=0){ return false; e.preventDefault(); } } }); If Firefox supports charCode, IE doesn't. How then, could I test if the user is typing uppercase or lowercase characters ? Thanks for any help !

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• MoveFileEx Problem

  - by rajivpradeep

  int i ; DWORD dw ; String^ Source = "c:\\ProtectedFlash\\Program\\test.exe" ; String^ Destination = "c:\\Program Files" ; // move to program Files Folder //pin_ptr<const wchar_t> WSource = PtrToStringChars(Source); // pin_ptr<const wchar_t> WDestination = PtrToStringChars(Destination); i = MoveFileEx(L"c:\\ProtectedFlash\\Program\\ProtectedFlash.exe",L"c:\\Program Files",MOVEFILE_REPLACE_EXISTING) ; dw = GetLastError() ; return 0; The status dw is valued as 5 , when i run the program. Whats the error

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• Entity Framework How to specify paramter type in generated SQL (SQLServer 2005) Nvarchar vs Varchar

  - by Gratzy

  In entity framework I have an Entity 'Client' that was generated from a database. There is a property called 'Account' it is defined in the storage model as: <Property Name="Account" Type="char" Nullable="false" MaxLength="6" /> And in the Conceptual Model as: <Property Name="Account" Type="String" Nullable="false" /> When select statements are generated using a variable for Account i.e. where m.Account == myAccount... Entity Framework generates a paramaterized query with a paramater of type NVarchar(6). The problem is that the column in the table is data type of char(6). When this is executed there is a large performance hit because of the data type difference. Account is an index on the table and instead of using the index I believe an Index scan is done. Anyone know how to force EF to not use Unicode for the paramater and use Varchar(6) instead?

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• Glib segfault g_free hash table

  - by Mike

  I'm not quite sure why if I try to free the data I get segfault. Any help will be appreciate it. static GHashTable *hashtable; static void add_inv(char *q) { gpointer old_key, old_value; if(!g_hash_table_lookup_extended(hashtable, q, &old_key, &old_value)){ g_hash_table_insert(hashtable, g_strdup(q), GINT_TO_POINTER(10)); }else{ (old_value)++; g_hash_table_insert(hashtable, g_strdup(q), old_value); g_hash_table_remove (hashtable, q); // segfault g_free(old_key); // segfault g_free(old_value); // segfault } } ... int main(int argc, char *argv[]){ hashtable = g_hash_table_new(g_str_hash, g_str_equal); ... g_hash_table_destroy(hashtable); }

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• What is the difference between NULL in C++ and null in Java?

  - by Stephano

  I've been trying to figure out why C++ is making me crazy typing NULL. Suddenly it hits me the other day; I've been typing null (lower case) in Java for years. Now suddenly I'm programming in C++ and that little chunk of muscle memory is making me crazy. Wikiperipatetic defines C++ NULL as part of the stddef: A macro that expands to a null pointer constant. It may be defined as ((void*)0), 0 or 0L depending on the compiler and the language. Sun's docs tells me this about Java's "null literal": The null type has one value, the null reference, represented by the literal null, which is formed from ASCII characters. A null literal is always of the null type. So this is all very nice. I know what a null pointer reference is, and thank you for the compiler notes. Now I'm a little fuzzy on the idea of a literal in Java so I read on... A literal is the source code representation of a fixed value; literals are represented directly in your code without requiring computation. There's also a special null literal that can be used as a value for any reference type. null may be assigned to any variable, except variables of primitive types. There's little you can do with a null value beyond testing for its presence. Therefore, null is often used in programs as a marker to indicate that some object is unavailable. Ok, so I think I get it now. In C++ NULL is a macro that, when compiled, defines the null pointer constant. In Java, null is a fixed value that any non-primitive can be assigned too; great for testing in a handy if statement. Java does not have pointers, so I can see why they kept null a simple value rather than anything fancy. But why did java decide to change the all caps NULL to null? Furthermore, am I missing anything here?

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• Delphi Typed Constants in Case Statements

  - by Andreas Rejbrand

  What is the most elegant (or least ugly) way of using typed constants in a case statement in Delphi? That is, assume for this question that you need to declare a typed constant as in const MY_CONST: cardinal = $12345678; ... Then the Delphi compiler will not accept case MyExpression of MY_CONST: { Do Something }; ... end; but you need to write case MyExpression of $12345678: { Do Something }; ... end; which is error-prone, hard to update, and not elegant. Is there any trick you can employ to make the compiler insert the value of the constant (preferably by checking the value of the constant under const in the source code, but maybe by looking-up the value at runtime)? We assume here that you will not alter the value of the "constant" at runtime.

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• Where to split a string literal

  - by quinmars

  Every time I have to split a long string literal into two (or more) pieces, because it does not fit into a single line, I have to decide if I split the text before or after a space. For example: const char * long_text1 = "This is a long text, which does not fit " "in one line"; /* or */ const char * long_text2 = "This is a long text, which does not fit" " in one line"; I tend to use the first way, but I do not have a real reason for it. So I wonder is there any advantage to favor one of them? I know this questions tend to be coding style question, but that's not my intend. I only want to know if there is a convincing reason why one of those two ways might be preferable.

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• Database design: Using hundred of fields for little values

  - by user964260

  I'm planning to develop a PHP Web App, it will mainly be used by registered users(sessions) While thinking about the DB design, I was contemplating that in order to give the best user experience possible there would be lots of options for the user to activate, deactivate, specify, etc. For example: - Options for each layout elements, dialog boxes, dashboard, grid, etc. - color, size, stay visible, invisible, don't ask again, show everytime, advanced mode, simple mode, etc. This would get like 100s of fields ranging from simple Yes/No or 1 to N values..., for each user. So, is it having a field for each of these options the way to go? or how do those CRMs or CMS or other Web Apps do it to store lots of 1-2 char long values? Do they group them on Text fields separated by a special char and then "explode" them as an array for runtime usage? thank you

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• Any socket programmers out there? How can I obtain the IPv4 address of the client?

  - by Dr Dork

  Hello! I'm prepping for a simple work project and am trying to familiarize myself with the basics of socket programming in a Unix dev environment. At this point, I have some basic server side code setup to listen for incoming TCP connection requests from clients after the parent socket has been created and is set to listen... int sockfd, newfd; unsigned int len; socklen_t sin_size; char msg[]="Test message sent"; char buf[MAXLEN]; int st, rv; struct addrinfo hints, *serverinfo, *p; struct sockaddr_storage client; char ip[INET6_ADDRSTRLEN]; . . //parent socket creation and listen code omitted for simplicity . //wait for connection requests from clients while(1) { //Returns the socketID and address of client connecting to socket if( ( newfd = accept(sockfd, (struct sockaddr *)&client, &len) ) == -1 ){ perror("Accept"); exit(-1); } if( (rv = recv(newfd, buf, MAXLEN-1, 0 )) == -1) { perror("Recv"); exit(-1); } struct sockaddr_in *clientAddr = ( struct sockaddr_in *) get_in_addr((struct sockaddr *)&client); inet_ntop(client.ss_family, clientAddr, ip, sizeof ip); printf("Receive from %s: query type is %s\n", ip, buf); if( ( st = send(newfd, msg, strlen(msg), 0)) == -1 ) { perror("Send"); exit(-1); } //ntohs is used to avoid big-endian and little endian compatibility issues printf("Send %d byte to port %d\n", ntohs(clientAddr->sin_port) ); close(newfd); } } I found the get_in_addr function online and placed it at the top of my code and use it to obtain the IP address of the client connecting... // get sockaddr, IPv4 or IPv6: void *get_in_addr(struct sockaddr *sa) { if (sa->sa_family == AF_INET) { return &(((struct sockaddr_in*)sa)->sin_addr); } return &(((struct sockaddr_in6*)sa)->sin6_addr); } but the function always returns the IPv6 IP address since thats what the sa_family property is set as. My question is, is the IPv4 IP address stored anywhere in the data I'm using and, if so, how can I access it? Thanks so much in advance for all your help!

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• QValidator for hex input

  - by Evan Teran

  I have a Qt widget which should only accept a hex string as input. It is very simple to restrict the input characters to [0-9A-Fa-f], but I would like to have it display with a delimiter between "bytes" so for example if the delimiter is a space, and the user types 0011223344 I would like the line edit to display 00 11 22 33 44 Now if the user presses the backspace key 3 times, then I want it to display 00 11 22 3. I almost have what i want, so far there is only one subtle bug involving using the delete key to remove a delimiter. Does anyone have a better way to implement this validator? Here's my code so far: class HexStringValidator : public QValidator { public: HexStringValidator(QObject * parent) : QValidator(parent) {} public: virtual void fixup(QString &input) const { QString temp; int index = 0; // every 2 digits insert a space if they didn't explicitly type one Q_FOREACH(QChar ch, input) { if(std::isxdigit(ch.toAscii())) { if(index != 0 && (index & 1) == 0) { temp += ' '; } temp += ch.toUpper(); ++index; } } input = temp; } virtual State validate(QString &input, int &pos) const { if(!input.isEmpty()) { // TODO: can we detect if the char which was JUST deleted // (if any was deleted) was a space? and special case this? // as to not have the bug in this case? const int char_pos = pos - input.left(pos).count(' '); int chars = 0; fixup(input); pos = 0; while(chars != char_pos) { if(input[pos] != ' ') { ++chars; } ++pos; } // favor the right side of a space if(input[pos] == ' ') { ++pos; } } return QValidator::Acceptable; } }; For now this code is functional enough, but I'd love to have it work 100% as expected. Obviously the ideal would be the just separate the display of the hex string from the actual characters stored in the QLineEdit's internal buffer but I have no idea where to start with that and I imagine is a non-trivial undertaking. In essence, I would like to have a Validator which conforms to this regex: "[0-9A-Fa-f]( [0-9A-Fa-f])*" but I don't want the user to ever have to type a space as delimiter. Likewise, when editing what they types, the spaces should be managed implicitly.

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• warning from Eclipse

  - by lego69

  can somebody please explain what does it mean : passing arg 1 of 'free' discards qualifiers from pointer target type thanks in advance

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• C++ Allocate Memory Without Activating Constructors

  - by schnozzinkobenstein

  I'm reading in values from a file which I will store in memory as I read them in. I've read on here that the correct way to handle memory location in C++ is to always use new/delete, but if I do: DataType* foo = new DataType[sizeof(DataType) * numDataTypes]; Then that's going to call the default constructor for each instance created, and I don't want that. I was going to do this: DataType* foo; char* tempBuffer=new char[sizeof(DataType) * numDataTypes]; foo=(DataType*) tempBuffer; But I figured that would be something poo-poo'd for some kind of type-unsafeness. So what should I do? And in researching for this question now I've seen that some people are saying arrays are bad and vectors are good. I was trying to use arrays more because I thought I was being a bad boy by filling my programs with (what I thought were) slower vectors. What should I be using???

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• JNI cached jclass global reference variables being garbage collected?

  - by bubbadoughball

  I'm working in the JNI Invocation API, calling into Java from C. I have some upfront initialization to cache 30+ Java classes into global references. The results of FindClass are passed into NewGlobalRef to acquire a global reference to the class. I'm caching these class variables to reuse them later. I have 30+ global references to classes (and 30+ global methodIDs for the class constructors). In the following sample, I've removed exception handling as well as JNI invocation for the purpose of shortening the code snippet. My working code has exception checks after every JNI call and I'm running with -Xcheck:jni. Here's the snippet: jclass aClass; jclass bClass; jmethodID aCtor; jmethodID bCtor; void getGlobalRef(const char* clazz, jclass* globalClass) { jclass local = (*jenv)->FindClass(jenv,clazz); if (local) { *globalClass = (jclass) (*jenv)->NewGlobalRef(jenv,local); (*jenv)->DeleteLocalRef(jenv,local); } } methodID getMethodID(jclass clazz, const char* method, const char* sig) { return (*jenv)->GetMethodID(jenv,clazz,method,sig); } void initializeJNI() { getGlobalRef("MyProj/Testclass1", &aclass); getGlobalRef("MyProj/Testclass2", &bclass); . . aCtor = getMethodID(aclass,"<init>","()V"); bCtor = getMethodID(bclass,"<init>","(I)V"); } The initializeJNI() function sets the global references for jclasses and method IDs for constructors as well as some jfieldID's and some initialization of C data structures. After initialization, when I call into a JNI function using some of the cached jclasses and ctor jmethodIDs, I get a bad global or local reference calling reported from the -Xcheck:jni. In gdb, I break at the last line of initializeJNI(), and print all jclasses and jmethodIDs and the ones causing problems look to have been turned into garbage or garbage-collected (i.e. 0x00 or 0x06). Is it possible for global references to be gc'ed? Any suggestions?

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• Binary Tree operator overloading and recursion

  - by furious.snail

  I was wondering how to overload the == operator for a binary tree to compare if two trees have identical data at same nodes. So far this is what I have: bool TreeType::operator==(const TreeType& otherTree) const { if((root == NULL) && (otherTree.root == NULL)) return true; //two null trees are equal else if((root != NULL) && (otherTree.root != NULL)) { return((root-info == otherTree.root-info) && //this part doesn't actually do anything recursively... //(root-left == otherTree.root-left) && //(root-right == otherTree.root-right)) } else return false; //one tree is null the other is not } I have a similar function that takes two TreeNode pointers as parameters but I've been stuck on how to convert it to this function.

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• Make Map Key Sorted According To Insert Sequence

  - by Yan Cheng CHEOK

  Without help from additional container (like vector), is it possible that I can make map's key sorted same sequence as insertion sequence? #include <map> #include <iostream> using namespace std; int main() { map<const char*, int> m; m["c"] = 2; m["b"] = 2; m["a"] = 2; m["d"] = 2; for (map<const char*, int>::iterator begin = m.begin(); begin != m.end(); begin++) { // How can I get the loop sequence same as my insert sequence. // c, b, a, d std::cout << begin->first << std::endl; } getchar(); }

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• How do I read input character-by-character in Java?

  - by Jergason

  I am used to the c-style getchar(), but it seems like there is nothing comparable for java. I am building a lexical analyzer, and I need to read in the input character by character. I know I can use the scanner to scan in a token or line and parse through the token char-by-char, but that seems unwieldy for strings spanning multiple lines. Is there a way to just get the next character from the input buffer in Java, or should I just plug away with the Scanner class? Edit: forgot to say where the input is coming from. The input is a file, not the keyboard.

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• Implementing operator< in C++

  - by Vulcan Eager

  I have a class with a few numeric fields such as: class Class1 { int a; int b; int c; public: // constructor and so on... bool operator<(const Class1& other) const; }; I need to use objects of this class as a key in an std::map. I therefore implement operator<. What is the simplest implementation of operator< to use here?

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