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  • How bad is code using std::basic_string<t> as a contiguous buffer?

    - by BillyONeal
    I know technically the std::basic_string template is not required to have contiguous memory. However, I'm curious how many implementations exist for modern compilers that actually take advantage of this freedom. For example, if one wants code like the following it seems silly to allocate a vector just to turn around instantly and return it as a string: DWORD valueLength = 0; DWORD type; LONG errorCheck = RegQueryValueExW( hWin32, value.c_str(), NULL, &type, NULL, &valueLength); if (errorCheck != ERROR_SUCCESS) WindowsApiException::Throw(errorCheck); else if (valueLength == 0) return std::wstring(); std::wstring buffer; do { buffer.resize(valueLength/sizeof(wchar_t)); errorCheck = RegQueryValueExW( hWin32, value.c_str(), NULL, &type, &buffer[0], &valueLength); } while (errorCheck == ERROR_MORE_DATA); if (errorCheck != ERROR_SUCCESS) WindowsApiException::Throw(errorCheck); return buffer; I know code like this might slightly reduce portability because it implies that std::wstring is contiguous -- but I'm wondering just how unportable that makes this code. Put another way, how may compilers actually take advantage of the freedom having noncontiguous memory allows? Oh: And of course given what the code's doing this only matters for Windows compilers.

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  • What's the best way to resolve a filepath?

    - by BillyONeal
    Hello everyone :) I've got a series of filepaths that look something like this: C:\Windows\System32\svchost.exe -k LocalSystemNetworkRestricted C:\Windows\System32\svchost C:\Program Files (x86)\Common Files\Steam\SteamService.exe /RunAsService "C:\Program Files (x86)\Common Files\Steam\SteamService.exe" /RunAsService and I need to find these paths' actual locations. So, respectively, the above would be: C:\Windows\System32\svchost.exe C:\Windows\System32\svchost.exe C:\Program Files (x86)\Common Files\Steam\SteamService.exe C:\Program Files (x86)\Common Files\Steam\SteamService.exe What's the best way to go about doing this? Does windows have an API function to accomplish it? I essentially am trying to figure out what executable CreateProcess will call if I pass it that path. Thanks! Billy3

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  • Unit Testing Refcounted Critical Section Class

    - by BillyONeal
    Hello all :) I'm looking at a simple class I have to manage critical sections and locks, and I'd like to cover this with test cases. Does this make sense, and how would one go about doing it? It's difficult because the only way to verify the class works is to setup very complicated threading scenarios, and even then there's not a good way to test for a leak of a Critical Section in Win32. Is there a more direct way to make sure it's working correctly? Here's the code: CriticalSection.hpp: #pragma once #include <windows.h> namespace WindowsAPI { namespace Threading { class CriticalSection; class CriticalLock { std::size_t *instanceCount; CRITICAL_SECTION * criticalStructure; bool lockValid; friend class CriticalSection; CriticalLock(std::size_t *, CRITICAL_SECTION *, bool); public: bool IsValid() { return lockValid; }; void Unlock(); ~CriticalLock() { Unlock(); }; }; class CriticalSection { std::size_t *instanceCount; CRITICAL_SECTION * criticalStructure; public: CriticalSection(); CriticalSection(const CriticalSection&); CriticalSection& operator=(const CriticalSection&); CriticalSection& swap(CriticalSection&); ~CriticalSection(); CriticalLock Enter(); CriticalLock TryEnter(); }; }} CriticalSection.cpp: #include "CriticalSection.hpp" namespace WindowsAPI { namespace Threading { CriticalSection::CriticalSection() { criticalStructure = new CRITICAL_SECTION; instanceCount = new std::size_t; *instanceCount = 1; InitializeCriticalSection(criticalStructure); } CriticalSection::CriticalSection(const CriticalSection& other) { criticalStructure = other.criticalStructure; instanceCount = other.instanceCount; instanceCount++; } CriticalSection& CriticalSection::operator=(const CriticalSection& other) { CriticalSection copyOfOther(other); swap(copyOfOther); return *this; } CriticalSection& CriticalSection::swap(CriticalSection& other) { std::swap(other.instanceCount, instanceCount); std::swap(other.criticalStructure, other.criticalStructure); return *this; } CriticalSection::~CriticalSection() { if (!--(*instanceCount)) { DeleteCriticalSection(criticalStructure); delete criticalStructure; delete instanceCount; } } CriticalLock CriticalSection::Enter() { EnterCriticalSection(criticalStructure); (*instanceCount)++; return CriticalLock(instanceCount, criticalStructure, true); } CriticalLock CriticalSection::TryEnter() { bool lockAquired; if (TryEnterCriticalSection(criticalStructure)) { (*instanceCount)++; lockAquired = true; } else lockAquired = false; return CriticalLock(instanceCount, criticalStructure, lockAquired); } void CriticalLock::Unlock() { if (!lockValid) return; LeaveCriticalSection(criticalStructure); lockValid = false; if (!--(*instanceCount)) { DeleteCriticalSection(criticalStructure); delete criticalStructure; delete instanceCount; } } }}

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  • How can I quickly enumerate directories on Win32?

    - by BillyONeal
    Hello everyone :) I'm trying to speedup directory enumeration in C++, where I'm recursing into subdirectories. I currently have an app which spends 95% of it's time in FindFirst/FindNextFile APIs, and it takes several minutes to enumerate all the files on a given volume. I know it's possible to do this faster because there is an app that does: Everything. It enumerates my entire drive in seconds. How might I accomplish something like this?

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  • Is this a good way to manage initializations of COM?

    - by BillyONeal
    Hello everyone :) I'm very new to anything involving Component Object Model, and I'm wondering if this method of managing calls to CoInitalize/CoUninitalize makes sense: COM.hpp: #pragma once namespace WindowsAPI { namespace ComponentObjectModel { class COM { COM(); ~COM(); public: static void Setup(); }; }} COM.cpp: #include <Windows.h> #include "COM.hpp" namespace WindowsAPI { namespace ComponentObjectModel { COM::COM() { if (CoInitializeEx(NULL, COINIT_APARTMENTTHREADED) != S_OK) throw std::runtime_error("Couldn't start COM!"); } COM::~COM() { CoUninitialize(); } void COM::Setup() { static COM instance; } }} Then any component that needs COM just calls COM::Setup() and forgets about it. Does this make sense or am I breaking any "rules" of COM?

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  • How can I refactor this to use an inline function or template instead of a macro?

    - by BillyONeal
    Hello, everyone :) I have a useful macro here: #define PATH_PREFIX_RESOLVE(path, prefix, environment) \ if (boost::algorithm::istarts_with(path, prefix)) { \ ExpandEnvironmentStringsW(environment, buffer, MAX_PATH); \ path.replace(0, (sizeof(prefix)/sizeof(wchar_t)) - 1, buffer); \ if (Exists(path)) return path; \ } It's used about 6 times within the scope of a single function (that's it), but macros seem to have "bad karma" :P Anyway, the problem here is the sizeof(prefix) part of the macro. If I just replace this with a function taking a const wchar_t[], then the sizeof() will fail to deliver expected results. Simply adding a size member doesn't really solve the problem either. Making the user supply the size of the constant literal also results in a mess of duplicated constants at the call site. Any ideas on this one?

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  • Is it a good idea to create an STL iterator which is noncopyable?

    - by BillyONeal
    Most of the time, STL iterators are CopyConstructable, because several STL algorithms require this to improve performance, such as std::sort. However, I've been working on a pet project to wrap the FindXFile API (previously asked about), but the problem is it's impossible to implement a copyable iterator around this API. A find handle cannot be duplicated by any means -- DuplicateHandle specifically forbids passing handles to it. And if you just maintain a reference count to the find handle, then a single increment by any copy results in an increment of all copies -- clearly that is not what a copy constructed iterator is supposed to do. Since I can't satisfy the traditional copy constructible requirement for iterators here, is it even worth trying to create an "STL style" iterator? On one hand, creating some other enumeration method is going to not fall into normal STL conventions, but on the other, following STL conventions are going to confuse users of this iterator if they try to CopyConstruct it later. Which is the lesser of two evils?

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  • Have you been in cases where TDD increased development time?

    - by BillyONeal
    Hello everyone :) I was reading http://stackoverflow.com/questions/2512504/tdd-how-to-start-really-thinking-tdd and I noticed many of the answers indicate that tests + application should take less time than just writing the application. In my experience, this is not true. My problem though is that some 90% of the code I write has a TON of operating system calls. The time spent to actually mock these up takes much longer than just writing the code in the first place. Sometimes 4 or 5 times as long to write the test as to write the actual code. I'm curious if there are other developers in this kind of a scenario.

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  • Why does my finite state machine take so long to execute?

    - by BillyONeal
    Hello all :) I'm working on a state machine which is supposed to extract function calls of the form /* I am a comment */ //I am a comment perf("this.is.a.string.which\"can have QUOTES\"", 123456); where the extracted data would be perf("this.is.a.string.which\"can have QUOTES\"", 123456); from a file. Currently, to process a 41kb file, this process is taking close to a minute and a half. Is there something I'm seriously misunderstanding here about this finite state machine? #include <boost/algorithm/string.hpp> std::vector<std::string> Foo() { std::string fileData; //Fill filedata with the contents of a file std::vector<std::string> results; std::string::iterator begin = fileData.begin(); std::string::iterator end = fileData.end(); std::string::iterator stateZeroFoundLocation = fileData.begin(); std::size_t state = 0; for(; begin < end; begin++) { switch (state) { case 0: if (boost::starts_with(boost::make_iterator_range(begin, end), "pref(")) { stateZeroFoundLocation = begin; begin += 4; state = 2; } else if (*begin == '/') state = 1; break; case 1: state = 0; switch (*begin) { case '*': begin = boost::find_first(boost::make_iterator_range(begin, end), "*/").end(); break; case '/': begin = std::find(begin, end, L'\n'); } break; case 2: if (*begin == '"') state = 3; break; case 3: switch(*begin) { case '\\': state = 4; break; case '"': state = 5; } break; case 4: state = 3; break; case 5: if (*begin == ',') state = 6; break; case 6: if (*begin != ' ') state = 7; break; case 7: switch(*begin) { case '"': state = 8; break; default: state = 10; break; } break; case 8: switch(*begin) { case '\\': state = 9; break; case '"': state = 10; } break; case 9: state = 8; break; case 10: if (*begin == ')') state = 11; break; case 11: if (*begin == ';') state = 12; break; case 12: state = 0; results.push_back(std::string(stateZeroFoundLocation, begin)); }; } return results; } Billy3

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  • Can I use Visual Studio 2010's compiler with Visual Studio 2008's Runtime Library?

    - by BillyONeal
    Hello everyone :) I have an application that needs to operate on Windows 2000. I'd also like to use Visual Studio 2010 (mainly because of the change in the definition of the auto keyword). However, I'm in a bit of a bind because I need the app to be able to operate on older OS's, namely: Windows 2000 Windows XP RTM Windows XP SP1 Visual Studio 2010's runtime library depends on the EncodePointer / DecodePointer API which was introduced in Windows XP SP2. If using the alternate runtime library is possible, will this break code that relies on C++0x features added in VS2010, like std::regex?

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  • Is there any tool to standardize format of C++ code?

    - by BillyONeal
    Hello, all :) I'm looking for a tool that works on Windows to reformat some C++ code in my codebase. Essentially, I've got some code I wrote a while ago that I'd like to use, but it doesn't match the style I'm using in a more recent project. What's the best way to reformat C++ code in a standard manner? Billy3

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  • Can I use Visual Studio 2010's C++ compiler with Visual Studio 2008's C++ Runtime Library?

    - by BillyONeal
    I have an application that needs to operate on Windows 2000. I'd also like to use Visual Studio 2010 (mainly because of the change in the definition of the auto keyword). However, I'm in a bit of a bind because I need the app to be able to operate on older OS's, namely: Windows 2000 Windows XP RTM Windows XP SP1 Visual Studio 2010's runtime library depends on the EncodePointer / DecodePointer API which was introduced in Windows XP SP2. If using the alternate runtime library is possible, will this break code that relies on C++0x features added in VS2010, like std::regex?

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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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  • How might I wrap the FindXFile-style APIs to the STL-style Iterator Pattern in C++?

    - by BillyONeal
    Hello everyone :) I'm working on wrapping up the ugly innards of the FindFirstFile/FindNextFile loop (though my question applies to other similar APIs, such as RegEnumKeyEx or RegEnumValue, etc.) inside iterators that work in a manner similar to the Standard Template Library's istream_iterators. I have two problems here. The first is with the termination condition of most "foreach" style loops. STL style iterators typically use operator!= inside the exit condition of the for, i.e. std::vector<int> test; for(std::vector<int>::iterator it = test.begin(); it != test.end(); it++) { //Do stuff } My problem is I'm unsure how to implement operator!= with such a directory enumeration, because I do not know when the enumeration is complete until I've actually finished with it. I have sort of a hack together solution in place now that enumerates the entire directory at once, where each iterator simply tracks a reference counted vector, but this seems like a kludge which can be done a better way. The second problem I have is that there are multiple pieces of data returned by the FindXFile APIs. For that reason, there's no obvious way to overload operator* as required for iterator semantics. When I overload that item, do I return the file name? The size? The modified date? How might I convey the multiple pieces of data to which such an iterator must refer to later in an ideomatic way? I've tried ripping off the C# style MoveNext design but I'm concerned about not following the standard idioms here. class SomeIterator { public: bool next(); //Advances the iterator and returns true if successful, false if the iterator is at the end. std::wstring fileName() const; //other kinds of data.... }; EDIT: And the caller would look like: SomeIterator x = ??; //Construct somehow while(x.next()) { //Do stuff } Thanks! Billy3

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  • Is there a way to increase the efficiency of shared_ptr by storing the reference count inside the co

    - by BillyONeal
    Hello everyone :) This is becoming a common pattern in my code, for when I need to manage an object that needs to be noncopyable because either A. it is "heavy" or B. it is an operating system resource, such as a critical section: class Resource; class Implementation : public boost::noncopyable { friend class Resource; HANDLE someData; Implementation(HANDLE input) : someData(input) {}; void SomeMethodThatActsOnHandle() { //Do stuff }; public: ~Implementation() { FreeHandle(someData) }; }; class Resource { boost::shared_ptr<Implementation> impl; public: Resource(int argA) explicit { HANDLE handle = SomeLegacyCApiThatMakesSomething(argA); if (handle == INVALID_HANDLE_VALUE) throw SomeTypeOfException(); impl.reset(new Implementation(handle)); }; void SomeMethodThatActsOnTheResource() { impl->SomeMethodThatActsOnTheHandle(); }; }; This way, shared_ptr takes care of the reference counting headaches, allowing Resource to be copyable, even though the underlying handle should only be closed once all references to it are destroyed. However, it seems like we could save the overhead of allocating shared_ptr's reference counts and such separately if we could move that data inside Implementation somehow, like boost's intrusive containers do. If this is making the premature optimization hackles nag some people, I actually agree that I don't need this for my current project. But I'm curious if it is possible.

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  • Why do programmers sometimes refer to "C++/STL" like it's a separate language?

    - by BillyONeal
    This may seem a trivial question, but it's one that's bothered me a lot lately. Why do some programmers refer to "C++/STL" like it's a different language? The STL is part of the C++ standard library -- and therefore is part of the language, "C++". It's not a separate component, and it does not live alone in the scope of things C++. Yet some continually act like it's a different language altogether. Why?

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  • How do I include extremely long literals in C++ source?

    - by BillyONeal
    Hello everyone :) I've got a bit of a problem. Essentially, I need to store a large list of whitelisted entries inside my program, and I'd like to include such a list directly -- I don't want to have to distribute other libraries and such, and I don't want to embed the strings into a Win32 resource, for a bunch of reasons I don't want to go into right now. I simply included my big whitelist in my .cpp file, and was presented with this error: 1>ServicesWhitelist.cpp(2807): fatal error C1091: compiler limit: string exceeds 65535 bytes in length The string itself is about twice this allowed limit by VC++. What's the best way to include such a large literal in a program?

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  • Fast method of directory enumeration on Win32?

    - by BillyONeal
    Hello everyone :) I'm trying to speedup directory enumeration in C++, where I'm recursing into subdirectories. I currently have an app which spends 95% of it's time in FindFirst/FindNextFile APIs, and it takes several minutes to enumerate all the files on a given volume. I know it's possible to do this faster because there is an app that does: Everything. It enumerates my entire drive in seconds. How might I accomplish something like this?

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  • What is a good standard for code width?

    - by BillyONeal
    Hello everyone :) I've heard in several places that it's bad to have code that is too wide onscreen. For example: for (std::vector<EnumServiceInformation>::const_iterator currentService = services.begin(); currentService != services.end(); currentService++) However, I've heard many arguments for 80 character wide limits. I'm assuming this 80 character limit comes from the traditional command prompt, which is typically 80 characters wide. However -- most of us are working on something much better than a typical command prompt, and I feel that using an 80 character limit encourages use of variable names that are far too short and do not describe what the variable is used for. What is a reasonable limit for a new project with no existing coding width standard?

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