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  • Value get changed even though I'm not using reference

    - by atch
    In code: struct Rep { const char* my_data_; Rep* my_left_; Rep* my_right_; Rep(const char*); }; typedef Rep& list; ostream& operator<<(ostream& out, const list& a_list) { int count = 0; list tmp = a_list;//----->HERE I'M CREATING A LOCAL COPY for (;tmp.my_right_;tmp = *tmp.my_right_) { out << "Object no: " << ++count << " has name: " << tmp.my_data_; //tmp = *tmp.my_right_; } return out;//------>HERE a_list is changed } I've thought that if I'll create local copy to a_list object I'll be operating on completely separate object. Why isn't so? Thanks.

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  • Am I abusing Policies?

    - by pmr
    I find myself using policies a lot in my code and usually I'm very happy with that. But from time to time I find myself confronted with using that pattern in situations where the Policies are selected and runtime and I have developed habbits to work around such situations. Usually I start with something like that: class DrawArrays { protected: void sendDraw() const; }; class DrawElements { protected: void sendDraw() const; }; template<class Policy> class Vertices : public Policy { using Policy::sendDraw(); public: void render() const; }; When the policy is picked at runtime I have different choices of working around the situation. Different code paths: if(drawElements) { Vertices<DrawElements> vertices; } else { Vertices<DrawArrays> vertices; } Inheritance and virtual calls: class PureVertices { public: void render()=0; }; template<class Policy> class Vertices : public PureVertices, public Policy { //.. }; Both solutions feel wrong to me. The first creates an umaintainable mess and the second introduces the overhead of virtual calls that I tried to avoid by using policies in the first place. Am I missing the proper solutions or do I use the wrong pattern to solve the problem?

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  • How `is_base_of` works?

    - by Alexey Malistov
    Why the following code works? typedef char (&yes)[1]; typedef char (&no)[2]; template <typename B, typename D> struct Host { operator B*() const; operator D*(); }; template <typename B, typename D> struct is_base_of { template <typename T> static yes check(D*, T); static no check(B*, int); static const bool value = sizeof(check(Host<B,D>(), int())) == sizeof(yes); }; //Test sample class Base {}; class Derived : private Base {}; //Exspression is true. int test[is_base_of<Base,Derived>::value && !is_base_of<Derived,Base>::value]; Note that B is private base. Note that operator B*() is const. How does this work? Why this works? Why static yes check(D*, T); is better than static yes check(B*, int); ?

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  • cast operator to base class within a thin wrapper derived class

    - by miked
    I have a derived class that's a very thin wrapper around a base class. Basically, I have a class that has two ways that it can be compared depending on how you interpret it so I created a new class that derives from the base class and only has new constructors (that just delegate to the base class) and a new operator==. What I'd like to do is overload the operator Base&() in the Derived class so in cases where I need to interpret it as the Base. For example: class Base { Base(stuff); Base(const Base& that); bool operator==(Base& rhs); //typical equality test }; class Derived : public Base { Derived(stuff) : Base(stuff) {}; Derived(const Base& that) : Base(that) {}; Derived(const Derived& that) : Base(that) {}; bool operator==(Derived& rhs); //special case equality test operator Base&() { return (Base&)*this; //Is this OK? It seems wrong to me. } }; If you want a simple example of what I'm trying to do, pretend I had a String class and String==String is the typical character by character comparison. But I created a new class CaseInsensitiveString that did a case insensitive compare on CaseInsensitiveString==CaseInsensitiveString but in all other cases just behaved like a String. it doesn't even have any new data members, just an overloaded operator==. (Please, don't tell me to use std::string, this is just an example!) Am I going about this right? Something seems fishy, but I can't put my finger on it.

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  • Looks like COM object is created, but JScript fails to get a reference

    - by damix911
    I'm using the following code to create a COM component that I have developed and registered. var mycom = new ActiveXObject("Mirabilis.ComponentServices.1"); mycom.SetFirstNumber(5); mycom.SetSecondNumber(3); The first line runs fine, while if I alter the ProgID (that is, the string passed to ActiveXObject) I get the message Automation server can't create object. This suggests that at least the basics of the registration mechanism are working properly. I integrated some logging calls into the DLL. When I run the script I get the proof into the log file that both this call to QueryInterface: STDAPI DllGetClassObject( const CLSID &clsid, const IID &iid, void **ppv) { ... CAddFactory *pAddFact = new CAddFactory; ... HRESULT hr = pAddFact->QueryInterface(iid, ppv); if (hr == S_OK) writeToLogFile("Class QueryInterface returned S_OK"); else writeToLogFile("Class QueryInterface failed"); return hr; ... } and this one: HRESULT __stdcall CAddFactory::CreateInstance( IUnknown *pUnknownOuter, const IID &iid, void **ppv) { ... CAddObj *pObject = new CAddObj; ... HRESULT hr = pObject->QueryInterface(iid, ppv); if (hr == S_OK) writeToLogFile("Object QueryInterface returned S_OK"); else writeToLogFile("Object QueryInterface failed"); return hr; ... } return S_OK. However, when JScript gets to line 3 of the script, I get the following error message: 'mycom' is null or not an object Why is this happening? It looks like JScript should be able to obtain a reference. Some attempts I made I tried to return S_FALSE from DllCanUnloadNow to be sure that the DLL will not be unloaded, just in case, but with no luck.

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  • Potential g++ template bug?

    - by Evan Teran
    I've encountered some code which I think should compile, but doesn't. So I'm hoping some of the local standards experts here at SO can help :-). I basically have some code which resembles this: #include <iostream> template <class T = int> class A { public: class U { }; public: U f() const { return U(); } }; // test either the work around or the code I want... #ifndef USE_FIX template <class T> bool operator==(const typename A<T>::U &x, int y) { return true; } #else typedef A<int> AI; bool operator==(const AI::U &x, int y) { return true; } #endif int main() { A<int> a; std::cout << (a.f() == 1) << std::endl; } So, to describe what is going on here. I have a class template (A) which has an internal class (U) and at least one member function which can return an instance of that internal class (f()). Then I am attempting to create an operator== function which compares this internal type to some other type (in this case an int, but it doesn't seem to matter). When USE_FIX is not defined I get the following error: test.cc: In function 'int main()': test.cc:27:25: error: no match for 'operator==' in 'a.A<T>::f [with T = int]() == 1' Which seems odd, because I am clearly (I think) defining a templated operator== which should cover this, in fact if I just do a little of the work for the compiler (enable USE_FIX), then I no longer get an error. Unfortunately, the "fix" doesn't work generically, only for a specific instantiation of the template. Is this supposed to work as I expected? Or is this simply not allowed? BTW: if it matters I am using gcc 4.5.2.

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  • Trouble with an depreciated constructor visual basic visual studio 2010

    - by VBPRIML
    My goal is to print labels with barcodes and a date stamp from an entry to a zebra TLP 2844 when the user clicks the ok button/hits enter. i found what i think might be the code for this from zebras site and have been integrating it into my program but part of it is depreciated and i cant quite figure out how to update it. below is what i have so far. The printer is attached via USB and the program will also store the entered numbers in a database but i have that part done. any help would be greatly Appreciated.   Public Class ScanForm      Inherits System.Windows.Forms.Form    Public Const GENERIC_WRITE = &H40000000    Public Const OPEN_EXISTING = 3    Public Const FILE_SHARE_WRITE = &H2      Dim LPTPORT As String    Dim hPort As Integer      Public Declare Function CreateFile Lib "kernel32" Alias "CreateFileA" (ByVal lpFileName As String,                                                                           ByVal dwDesiredAccess As Integer,                                                                           ByVal dwShareMode As Integer, <MarshalAs(UnmanagedType.Struct)> ByRef lpSecurityAttributes As SECURITY_ATTRIBUTES,                                                                           ByVal dwCreationDisposition As Integer, ByVal dwFlagsAndAttributes As Integer,                                                                           ByVal hTemplateFile As Integer) As Integer          Public Declare Function CloseHandle Lib "kernel32" Alias "CloseHandle" (ByVal hObject As Integer) As Integer      Dim retval As Integer           <StructLayout(LayoutKind.Sequential)> Public Structure SECURITY_ATTRIBUTES          Private nLength As Integer        Private lpSecurityDescriptor As Integer        Private bInheritHandle As Integer      End Structure            Private Sub OKButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles OKButton.Click          Dim TrNum        Dim TrDate        Dim SA As SECURITY_ATTRIBUTES        Dim outFile As FileStream, hPortP As IntPtr          LPTPORT = "USB001"        TrNum = Me.ScannedBarcodeText.Text()        TrDate = Now()          hPort = CreateFile(LPTPORT, GENERIC_WRITE, FILE_SHARE_WRITE, SA, OPEN_EXISTING, 0, 0)          hPortP = New IntPtr(hPort) 'convert Integer to IntPtr          outFile = New FileStream(hPortP, FileAccess.Write) 'Create FileStream using Handle        Dim fileWriter As New StreamWriter(outFile)          fileWriter.WriteLine(" ")        fileWriter.WriteLine("N")        fileWriter.Write("A50,50,0,4,1,1,N,")        fileWriter.Write(Chr(34))        fileWriter.Write(TrNum) 'prints the tracking number variable        fileWriter.Write(Chr(34))        fileWriter.Write(Chr(13))        fileWriter.Write(Chr(10))        fileWriter.Write("A50,100,0,4,1,1,N,")        fileWriter.Write(Chr(34))        fileWriter.Write(TrDate) 'prints the date variable        fileWriter.Write(Chr(34))        fileWriter.Write(Chr(13))        fileWriter.Write(Chr(10))        fileWriter.WriteLine("P1")        fileWriter.Flush()        fileWriter.Close()        outFile.Close()        retval = CloseHandle(hPort)          'Add entry to database        Using connection As New SqlClient.SqlConnection("Data Source=MNGD-LABS-APP02;Initial Catalog=ScannedDB;Integrated Security=True;Pooling=False;Encrypt=False"), _        cmd As New SqlClient.SqlCommand("INSERT INTO [ScannedDBTable] (TrackingNumber, Date) VALUES (@TrackingNumber, @Date)", connection)            cmd.Parameters.Add("@TrackingNumber", SqlDbType.VarChar, 50).Value = TrNum            cmd.Parameters.Add("@Date", SqlDbType.DateTime, 8).Value = TrDate            connection.Open()            cmd.ExecuteNonQuery()            connection.Close()        End Using          'Prepare data for next entry        ScannedBarcodeText.Clear()        Me.ScannedBarcodeText.Focus()      End Sub

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  • Swig C++ Lua Pass class by reference

    - by Jeremy
    I don't know why I'm having a hard time with this. All I want to do is this: class foo { public: foo(){} ~foo(){} float a,b; }; class foo2 { public: foo2(){} foo2(const foo &f){*this = f;} ~foo2(){} void operator=(const foo& f){ x = f.a; y = f.b; } float x,y; }; /* Usage(cpp): foo f; foo2 f2(f); //or using the = operator f2 = f; */ The problem I'm having is that, after swigging this code, I can't figure out how to make the lua script play nice. /* Usage(lua) f = example.foo() f2 = example.foo2(f) --error */ The error I get is "Wrong arguments for overloaded function 'new_Foo2'": Possible c/c++ prototypes are: foo2() foo2(foo const &) The same thing happens if I try and use do f2 = f. As I understand it everything is stored as a pointer so I did try adding an additional constructor that took a pointer to foo but to no avail.

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  • From where starts the process' memory space and where does it end?

    - by nhaa123
    Hi, I'm trying to dump memory from my application where the variables lye. Here's the function: void MyDump(const void *m, unsigned int n) { const unsigned char *p = reinterpret_cast<const unsigned char *(m); char buffer[16]; unsigned int mod = 0; for (unsigned int i = 0; i < n; ++i, ++mod) { if (mod % 16 == 0) { mod = 0; std::cout << " | "; for (unsigned short j = 0; j < 16; ++j) { switch (buffer[j]) { case 0xa: case 0xb: case 0xd: case 0xe: case 0xf: std::cout << " "; break; default: std::cout << buffer[j]; } } std::cout << "\n0x" << std::setfill('0') << std::setw(8) << std::hex << (long)i << " | "; } buffer[i % 16] = p[i]; std::cout << std::setw(2) << std::hex << static_cast<unsigned int(p[i]) << " "; if (i % 4 == 0 && i != 1) std::cout << " "; } } Now, how can I know from which address starts my process memory space, where all the variables are stored? And how do I now, how long the area is? For instance: MyDump(0x0000 /* <-- Starts from here? */, 0x1000 /* <-- This much? */); Best regards, nhaa123

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  • Botan linking error on Windows MSVC

    - by Jake Petroules
    I am trying to compile a library linking to the version of Botan from the Qt Creator sources with MSVC 2008 but am receiving the following error. MinGW compiles and links it fine. What is the issue? databasecrypto.obj:-1: error: LNK2019: unresolved external symbol "public: static unsigned int const Botan::Pipe::DEFAULT_MESSAGE" (?DEFAULT_MESSAGE@Pipe@Botan@@2IB) referenced in function "private: static class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > __cdecl DatabaseCrypto::b64_encode(class Botan::SecureVector<unsigned char> const &)" (?b64_encode@DatabaseCrypto@@CA?AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@ABV?$SecureVector@E@Botan@@@Z) /*! Encodes the Botan byte array \a in as a base 64 string. \param in The Botan byte array to encode. */ std::string DatabaseCrypto::b64_encode(const SecureVector<Botan::byte> &in) { Pipe pipe(new Base64_Encoder); pipe.process_msg(in); return pipe.read_all_as_string(); // <-- default parameter here is Botan::Pipe::DEFAULT_MESSAGE }

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  • typename resolution in cases of ambiguity

    - by parapura rajkumar
    I was playing with Visual Studio and templates. Consider this code struct Foo { struct Bar { }; static const int Bar=42; }; template<typename T> void MyFunction() { typename T::Bar f; } int main() { MyFunction<Foo>(); return 0; } When I compile this is either Visual Studio 2008 and 11, I get the following error error C2146: syntax error : missing ';' before identifier 'f' Is Visual Studio correct in this regard ? Is the code violating any standards ? If I change the code to struct Foo { struct Bar { }; static const int Bar=42; }; void SecondFunction( const int& ) { } template<typename T> void MyFunction() { SecondFunction( T::Bar ); } int main() { MyFunction<Foo>(); return 0; } it compiles without any warnings. In Foo::BLAH a member preferred over a type in case of conflicts ?

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  • C++ Switch won't compile with externally defined variable used as case

    - by C Nielsen
    I'm writing C++ using the MinGW GNU compiler and the problem occurs when I try to use an externally defined integer variable as a case in a switch statement. I get the following compiler error: "case label does not reduce to an integer constant". Because I've defined the integer variable as extern I believe that it should compile, does anyone know what the problem may be? Below is an example: test.cpp #include <iostream> #include "x_def.h" int main() { std::cout << "Main Entered" << std::endl; switch(0) { case test_int: std::cout << "Case X" << std::endl; break; default: std::cout << "Case Default" << std::endl; break; } return 0; } x_def.h extern const int test_int; x_def.cpp const int test_int = 0; This code will compile correctly on Visual C++ 2008. Furthermore a Montanan friend of mine checked the ISO C++ standard and it appears that any const-integer expression should work. Is this possibly a compiler bug or have I missed something obvious? Here's my compiler version information: Reading specs from C:/MinGW/bin/../lib/gcc/mingw32/3.4.5/specs Configured with: ../gcc-3.4.5-20060117-3/configure --with-gcc --with-gnu-ld --with-gnu-as --host=mingw32 --target=mingw32 --prefix=/mingw --enable-threads --disable-nls --enable-languages=c,c++,f77,ada,objc,java --disable-win32-registry --disable-shared --enable-sjlj-exceptions --enable-libgcj --disable-java-awt --without-x --enable-java-gc=boehm --disable-libgcj-debug --enable-interpreter --enable-hash-synchronization --enable-libstdcxx-debug Thread model: win32 gcc version 3.4.5 (mingw-vista special r3)

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  • Returning c_str from a function

    - by user199421
    This is from a small library that I found online: const char* GetHandStateBrief(const PostFlopState* state) { static std::ostringstream out; ... rest of the function ... return out.str().c_str() Now in my code I am doing this: const char *d = GetHandStateBrief(&post); std::cout<< d << std::endl; Now, at first d contained garbage. I then realized that the c string I am getting from the function is destroyed when the function returns because std::ostringstream is allocated on the stack. So I added: return strdup( out.str().c_str()); And now I can get the text I need from the function. I have two questions: 1) Am I understanding this correctly? 2) I later noticed that the ostringstream was was allocated with static storage. Doesn't that mean that the object is supposed to stay in memory until the program terminates? and if so , then why can't I access the string?

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  • Unit Testing Private Method in Resource Managing Class (C++)

    - by BillyONeal
    I previously asked this question under another name but deleted it because I didn't explain it very well. Let's say I have a class which manages a file. Let's say that this class treats the file as having a specific file format, and contains methods to perform operations on this file: class Foo { std::wstring fileName_; public: Foo(const std::wstring& fileName) : fileName_(fileName) { //Construct a Foo here. }; int getChecksum() { //Open the file and read some part of it //Long method to figure out what checksum it is. //Return the checksum. } }; Let's say I'd like to be able to unit test the part of this class that calculates the checksum. Unit testing the parts of the class that load in the file and such is impractical, because to test every part of the getChecksum() method I might need to construct 40 or 50 files! Now lets say I'd like to reuse the checksum method elsewhere in the class. I extract the method so that it now looks like this: class Foo { std::wstring fileName_; static int calculateChecksum(const std::vector<unsigned char> &fileBytes) { //Long method to figure out what checksum it is. } public: Foo(const std::wstring& fileName) : fileName_(fileName) { //Construct a Foo here. }; int getChecksum() { //Open the file and read some part of it return calculateChecksum( something ); } void modifyThisFileSomehow() { //Perform modification int newChecksum = calculateChecksum( something ); //Apply the newChecksum to the file } }; Now I'd like to unit test the calculateChecksum() method because it's easy to test and complicated, and I don't care about unit testing getChecksum() because it's simple and very difficult to test. But I can't test calculateChecksum() directly because it is private. Does anyone know of a solution to this problem?

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  • Problem in printing array of char pointer passing from Python

    - by Yan Cheng CHEOK
    My following C code works quite well, till my Python code trying to pass an array of char pointer to it. The output I obtain is The file_name is python-file Another 3 string is not being printed out. Anything I had missed out? C Code #include <iostream> #include "c_interface.h" int foo(const char* file_name, const char** names) { std::cout << "The file_name is " << file_name << std::endl; while (*names) { std::cout << "The name is " << *names << std::endl; names++; } return 0; } /* int main() { const char *c[] = {"123gh", "456443432", "789", 0}; foo("hello", c); getchar(); } */ Python Code #!c:/Python27/python.exe -u from ctypes import * name0 = "NAME0" name1 = "NAME1" name2 = "NAME2" names = ((c_char_p * 1024) * 4)() names[0].value = name0 names[1].value = name1 names[2].value = name2 names[3].value = 0 libc = CDLL("foo.dll") libc.foo("python-file", names)

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  • boost::python string-convertible properties

    - by Checkers
    I have a C++ class, which has the following methods: class Bar { ... const Foo& getFoo() const; void setFoo(const Foo&); }; where class Foo is convertible to std::string (it has an implicit constructor from std::string and an std::string cast operator). I define a Boost.Python wrapper class, which, among other things, defines a property based on previous two functions: class_<Bar>("Bar") ... .add_property( "foo", make_function( &Bar::getFoo, return_value_policy<return_by_value>()), &Bar::setFoo) ... I also mark the class as convertible to/from std::string. implicitly_convertible<std::string, Foo>(); implicitly_convertible<Foo, std::string>(); But at runtime I still get a conversion error trying to access this property: TypeError: No to_python (by-value) converter found for C++ type: Foo How to achieve the conversion without too much boilerplate of wrapper functions? (I already have all the conversion functions in class Foo, so duplication is undesirable.

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  • map operator [] operands

    - by Jamie Cook
    Hi all I have the following in a member function int tt = 6; vector<set<int>>& temp = m_egressCandidatesByDestAndOtMode[tt]; set<int>& egressCandidateStops = temp.at(dest); and the following declaration of a member variable map<int, vector<set<int>>> m_egressCandidatesByDestAndOtMode; However I get an error when compiling (Intel Compiler 11.0) 1>C:\projects\svn\bdk\Source\ZenithAssignment\src\Iteration\PtBranchAndBoundIterationOriginRunner.cpp(85): error: no operator "[]" matches these operands 1> operand types are: const std::map<int, std::vector<std::set<int, std::less<int>, std::allocator<int>>, std::allocator<std::set<int, std::less<int>, std::allocator<int>>>>, std::less<int>, std::allocator<std::pair<const int, std::vector<std::set<int, std::less<int>, std::allocator<int>>, std::allocator<std::set<int, std::less<int>, std::allocator<int>>>>>>> [ const int ] 1> vector<set<int>>& temp = m_egressCandidatesByDestAndOtMode[tt]; 1> ^ I know it's got to be something silly but I can't see what I've done wrong.

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  • When and why can sprintf fail?

    - by Srekel
    I'm using swprintf to build a string into a buffer (using a loop among other things). const int MaxStringLengthPerCharacter = 10 + 1; wchar_t* pTmp = pBuffer; for ( size_t i = 0; i < nNumPlayers ; ++i) { const int nPlayerId = GetPlayer(i); const int nWritten = swprintf(pTmp, MaxStringLengthPerCharacter, TEXT("%d,"), nPlayerId); assert(nWritten >= 0 ); pTmp += nWritten; } *pTaskPlayers = '\0'; If during testing the assert never hits, can I be sure that it will never hit in live code? That is, do I need to check if nWritten < 0 and handle that, or can I safely assume that there won't be a problem? Under which circumstances can it return -1? The documentation more or less just states "If the function fails". In one place I've read that it will fail if it can't match the arguments (i.e. the formatting string to the varargs) but that doesn't worry me. I'm also not worried about buffer overrun in this case - I know the buffer is big enough.

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  • How can I determine PerlLogHandler performance impact?

    - by Timmy
    I want to create a custom Apache2 log handler, and the template that is found on the apache site is: #file:MyApache2/LogPerUser.pm #--------------------------- package MyApache2::LogPerUser; use strict; use warnings; use Apache2::RequestRec (); use Apache2::Connection (); use Fcntl qw(:flock); use File::Spec::Functions qw(catfile); use Apache2::Const -compile => qw(OK DECLINED); sub handler { my $r = shift; my ($username) = $r->uri =~ m|^/~([^/]+)|; return Apache2::Const::DECLINED unless defined $username; my $entry = sprintf qq(%s [%s] "%s" %d %d\n), $r->connection->remote_ip, scalar(localtime), $r->uri, $r->status, $r->bytes_sent; my $log_path = catfile Apache2::ServerUtil::server_root, "logs", "$username.log"; open my $fh, ">>$log_path" or die "can't open $log_path: $!"; flock $fh, LOCK_EX; print $fh $entry; close $fh; return Apache2::Const::OK; } 1; What is the performance cost of the flocks? Is this logging process done in parallel, or in serial with the HTTP request? In parallel the performance would not matter as much, but I wouldn't want the user to wait another split second to add something like this.

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  • iPhone --- 3DES Encryption returns "wrong" results?

    - by Jan Gressmann
    Hello fellow developers, I have some serious trouble with a CommonCrypto function. There are two existing applications for BlackBerry and Windows Mobile, both use Triple-DES encryption with ECB mode for data exchange. On either the encrypted results are the same. Now I want to implent the 3DES encryption into our iPhone application, so I went straight for CommonCrypto: http://www.opensource.apple.com/source/CommonCrypto/CommonCrypto-32207/CommonCrypto/CommonCryptor.h I get some results if I use CBC mode, but they do not correspond with the results of Java or C#. Anyway, I want to use ECB mode, but I don't get this working at all - there is a parameter error showing up... This is my call for the ECB mode... I stripped it a little bit: const void *vplainText; plainTextBufferSize = [@"Hello World!" length]; bufferPtrSize = (plainTextBufferSize + kCCBlockSize3DES) & ~(kCCBlockSize3DES - 1); plainText = (const void *) [@"Hello World!" UTF8String]; NSString *key = @"abcdeabcdeabcdeabcdeabcd"; ccStatus = CCCrypt(kCCEncrypt, kCCAlgorithm3DES, kCCOptionECBMode, key, kCCKeySize3DES, nil, // iv, not used with ECB plainText, plainTextBufferSize, (void *)bufferPtr, // output bufferPtrSize, &movedBytes); t is more or less the code from here: http://discussions.apple.com/thread.jspa?messageID=9017515 But as already mentioned, I get a parameter error each time... When I use kCCOptionPKCS7Padding instead of kCCOptionECBMode and set the same initialization vector in C# and my iPhone code, the iPhone gives me different results. Is there a mistake by getting my output from the bufferPtr? Currently I get the encrypted stuff this way: NSData *myData = [NSData dataWithBytes:(const void *)bufferPtr length:(NSUInteger)movedBytes]; result = [[NSString alloc] initWithData:myData encoding:NSISOLatin1StringEncoding]; It seems I almost tried every setting twice, different encodings and so on... where is my error?

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  • C++ Implicit Conversion Operators

    - by Imbue
    I'm trying to find a nice inheritance solution in C++. I have a Rectangle class and a Square class. The Square class can't publicly inherit from Rectangle, because it cannot completely fulfill the rectangle's requirements. For example, a Rectangle can have it's width and height each set separately, and this of course is impossible with a Square. So, my dilemma. Square obviously will share a lot of code with Rectangle; they are quite similar. For examlpe, if I have a function like: bool IsPointInRectangle(const Rectangle& rect); it should work for a square too. In fact, I have a ton of such functions. So in making my Square class, I figured I would use private inheritance with a publicly accessible Rectangle conversion operator. So my square class looks like: class Square : private Rectangle { public: operator const Rectangle&() const; }; However, when I try to pass a Square to the IsPointInRectangle function, my compiler just complains that "Rectangle is an inaccessible base" in that context. I expect it to notice the Rectangle operator and use that instead. Is what I'm trying to do even possible? If this can't work I'm probably going to refactor part of Rectangle into MutableRectangle class. Thanks.

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  • How to define and use a friend function to a temlate class with the same template?

    - by Narek
    I have written the following code: #include <iostream> using namespace std; template <class T> class AA { T a; public: AA() { a = 7; } friend void print(const AA<T> & z); }; template <class T> void print(const AA<T> & z) { cout<<"Print: "<<z.a<<endl; } void main() { AA<int> a; print<int>(a); } And getting the following error: error C2248: 'AA<T>::a' : cannot access private member declared in class 'AA<T>' 1> with 1> [ 1> T=int 1> ] 1> c:\users\narek\documents\visual studio 2008\projects\aaa\aaa\a.cpp(7) : see declaration of 'AA<T>::a' 1> with 1> [ 1> T=int 1> ] 1> c:\users\narek\documents\visual studio 2008\projects\aaa\aaa\a.cpp(30) : see reference to function template instantiation 'void print<int>(const AA<T> &)' being compiled 1> with 1> [ 1> T=int 1> ] What's wrong?

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  • Who deletes the copied instance in + operator ? (c++)

    - by Dima
    Hello, I searched how to implement + operator properly all over the internet and all the results i found do the following steps : const MyClass MyClass::operator+(const MyClass &other) const { MyClass result = *this; // Make a copy of myself. Same as MyClass result(*this); result += other; // Use += to add other to the copy. return result; // All done! } I have few questions about this "process" : Isn't that stupid to implement + operator this way, it calls the assignment operator(which copies the class) in the first line and then the copy constructor in the return (which also copies the class , due to the fact that the return is by value, so it destroys the first copy and creates a new one.. which is frankly not really smart ... ) When i write a=b+c, the b+c part creates a new copy of the class, then the 'a=' part copies the copy to himself. who deletes the copy that b+c created ? Is there a better way to implement + operator without coping the class twice, and also without any memory issues ? thanks in advance

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  • C++ using typedefs in non-inline functions

    - by ArunSaha
    I have a class like this template< typename T > class vector { public: typedef T & reference; typedef T const & const_reference; typedef size_t size_type; const_reference at( size_t ) const; reference at( size_t ); and later in the same file template< typename T > typename vector<T>::const_reference // Line X vector<T>::at( size_type i ) const { rangecheck(); return elems_[ i ]; } template< typename T > reference // Line Y vector<T>::at( size_type i ) { rangecheck(); return elems_[ i ]; } Line X compiles fine but Line Y does not compile. The error message from g++ (version 4.4.1) is: foo.h:Y: error: expected initializer before 'vector' From this I gather that, if I want to have non-inline functions then I have to fully qualify the typedef name as in Line X. (Note that, there is no problem for size_type.) However, at least to me, Line X looks clumsy. Is there any alternative approach?

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  • MMGR Questions, code use and thread-saftey

    - by chadb
    1) Is MMGR thread safe? 2) I was hoping someone could help me understand some code. I am looking at something where a macro is used, but I don't understand the macro. I know it contains a function call and an if check, however, the function is a void function. How does wrapping "(m_setOwner (FILE,_LINE_,FUNCTION),false)" ever change return types? #define someMacro (m_setOwner(__FILE__,__LINE__,__FUNCTION__),false) ? NULL : new ... void m_setOwner(const char *file, const unsigned int line, const char *func); 3) What is the point of the reservoir? 4) On line 770 ("void *operator new(size_t reportedSize)" there is the line "// ANSI says: allocation requests of 0 bytes will still return a valid value" Who/what is ANSI in this context? Do they mean the standards? 5) This is more of C++ standards, but where does "reportedSize" come from for "void *operator new(size_t reportedSize)"? 6) Is this the code that is actually doing the allocation needed? "au-actualAddress = malloc(au-actualSize);"

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