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  • How to use iterator in nested arraylist

    - by Muhammad Abrar
    I am trying to build an NFA with a special purpose of searching, which is totally different from regex. The State has following format class State implements List{ //GLOBAL DATA static int depth; //STATE VALUES String stateName; ArrayList<String> label = new ArrayList<>(); //Label for states //LINKS TO OTHER STATES boolean finalState; ArrayList<State> nextState ; // Link with multiple next states State preState; // previous state public State() { stateName = ""; finalState = true; nextState = new ArrayList<>(); } public void addlabel(String lbl) { if(!this.label.contains(lbl)) this.label.add(lbl); } public State(String state, String lbl) { this.stateName = state; if(!this.label.contains(lbl)) this.label.add(lbl); depth++; } public State(String state, String lbl, boolean fstate) { this.stateName = state; this.label.add(lbl); this.finalState = fstate; this.nextState = new ArrayList<>(); } void displayState() { System.out.print(this.stateName+" --> "); for(Iterator<String> it = label.iterator(); it.hasNext();) { System.out.print(it.next()+" , "); } System.out.println("\nNo of States : "+State.depth); } Next, the NFA class is public class NFA { static final String[] STATES= {"A","B","C","D","E","F","G","H","I","J","K","L","M" ,"N","O","P","Q","R","S","T","U","V","W","X","Y","Z"}; State startState; State currentState; static int level; public NFA() { startState = new State(); startState = null; currentState = new State(); currentState = null; startState = currentState; } /** * * @param st */ NFA(State startstate) { startState = new State(); startState = startstate; currentState = new State(); currentState = null; currentState = startState ; // To show that their is only one element in NFA } boolean insertState(State newState) { newState.nextState = new ArrayList<>(); if(currentState == null && startState == null ) //if empty NFA { newState.preState = null; startState = newState; currentState = newState; State.depth = 0; return true; } else { if(!Exist(newState.stateName))//Exist is used to check for duplicates { newState.preState = currentState ; currentState.nextState.add(newState); currentState = newState; State.depth++; return true; } } return false; } boolean insertState(State newState, String label) { newState.label.add(label); newState.nextState = null; newState.preState = null; if(currentState == null && startState == null) { startState = newState; currentState = newState; State.depth = 0; return true; } else { if(!Exist(newState.stateName)) { newState.preState = currentState; currentState.nextState.add(newState); currentState = newState; State.depth++; return true; } else { ///code goes here } } return false; } void markFinal(State s) { s.finalState = true; } void unmarkFinal(State s) { s.finalState = false; } boolean Exist(String s) { State temp = startState; if(startState.stateName.equals(s)) return true; Iterator<State> it = temp.nextState.iterator(); while(it.hasNext()) { Iterator<State> i = it ;//startState.nextState.iterator(); { while(i.hasNext()) { if(i.next().stateName.equals(s)) return true; } } //else // return false; } return false; } void displayNfa() { State st = startState; if(startState == null && currentState == null) { System.out.println("The NFA is empty"); } else { while(st != null) { if(!st.nextState.isEmpty()) { Iterator<State> it = st.nextState.iterator(); do { st.displayState(); st = it.next(); }while(it.hasNext()); } else { st = null; } } } System.out.println(); } /** * @param args the command line arguments */ /** * * @param args the command line arguments */ public static void main(String[] args) { // TODO code application logic here NFA l = new NFA(); State s = new State("A11", "a",false); NFA ll = new NFA(s); s = new State("A111", "a",false); ll.insertState(s); ll.insertState(new State("A1","0")); ll.insertState(new State("A1111","0")); ll.displayNfa(); int j = 1; for(int i = 0 ; i < 2 ; i++) { int rand = (int) (Math.random()* 10); State st = new State(STATES[rand],String.valueOf(i), false); if(l.insertState(st)) { System.out.println(j+" : " + STATES[rand]+" and "+String.valueOf(i)+ " inserted"); j++; } } l.displayNfa(); System.out.println("No of states inserted : "+ j--); } I want to do the following This program always skip to display the last state i.e. if there are 10 states inserted, it will display only 9. In exist() method , i used two iterator but i do not know why it is working I have no idea how to perform searching for the existing class name, when dealing with iterators. How should i keep track of current State, properly iterate through the nextState List, Label List in a depth first order. How to insert unique States i.e. if State "A" is inserted once, it should not insert it again (The exist method is not working) Best Regards

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  • Modify iterator

    - by isola009
    I have a iterator (ite) created from a set (a): var a = Set(1,2,3,4,5) var ite = a.iterator If I remove 2 element of my set: a -= 2 Now, if I move iterator for all elements, I get all elements (2 element included). It's ok, but... How I can tell to iteratator to delete 2 element?

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  • Iterator category

    - by Knowing me knowing you
    In code: //I know that to get this effect (being able to use it with std algorithms) I can inherit like I did in line below: class Iterator //: public std::iterator<std::bidirectional_iterator_tag,T> { private: T** itData_; public: //BUT I WOULD LIKE TO BE ABLE TO DO IT BY HAND AS WELL typedef std::bidirectional_iterator_tag iterator_category; typedef T* value_type;//SHOULD IT BE T AS value_type or T*? typedef std::ptrdiff_t difference_type; typedef T** pointer;//SHOULD IT BE T* AS pointer or T**? typedef T*& reference;//SHOULD IT BE T& AS reference or T*&? }; Basically what I'm asking is if I have my variable of type T** in iterator class is it right assumption that value type for this iterator will be T* and so on as I described in comments in code, right next to relevant lines. Thank you.

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  • Why is comparing against "end()" iterator legal?

    - by sharptooth
    According to C++ standard (3.7.3.2/4) using (not only dereferencing, but also copying, casting, whatever else) an invalid pointer is undefined behavior (in case of doubt also see this question). Now the typical code to traverse an STL containter looks like this: std::vector<int> toTraverse; //populate the vector for( std::vector<int>::iterator it = toTraverse.begin(); it != toTraverse.end(); ++it ) { //process( *it ); } std::vector::end() is an iterator onto the hypothetic element beyond the last element of the containter. There's no element there, therefore using a pointer through that iterator is undefined behavior. Now how does the != end() work then? I mean in order to do the comparison an iterator needs to be constructed wrapping an invalid address and then that invalid address will have to be used in a comparison which again is undefined behavior. Is such comparison legal and why?

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  • How to correctly inherit std::iterator.

    - by Knowing me knowing you
    Guys if I have class like below: template<class T> class X { T** myData_; public: class iterator : public iterator<random_access_iterator_tag,/*WHAT SHALL I PUT HERE? T OR T** AND WHY?*/> { T** itData_;//HERE I'M HAVING THE SAME TYPE AS MAIN CLASS ON WHICH ITERATOR WILL OPERATE }; }; Questions are in code next to appropriate lines. Thank you.

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  • Java LinkedList iterator being exhausted prematurely

    - by Sujeet
    I am using LinkedList and retrieving an Iterator object by using list.iterator(). After that, I am checking it.hasNext(), real issue is while checking it.hasNext(), sometimes it returns false. I need help why this is happening, though I have elements in the list. Some code: public synchronized void check(Object obj) throws Exception { Iterator itr = list.iterator(); while(itr.hasNext()) { //This Line I get false.. though i have list size is 1 Item p = (Item)itr.next(); if(p.getId() == null) {continue;} if(p.getId().getElemntId() == obj.getId() || obj.getId() == 0 ) { p.setResponse(obj); notifyAll(); return; } } Log.Error("validate failed obj.getId="+obj.getId()+" **list.size="+list.size()*This shows 1*); throw new Exception("InvalidData"); }

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  • Output iterator's value_type

    - by wilhelmtell
    The STL commonly defines an output iterator like so: template<class Cont> class insert_iterator : public iterator<output_iterator_tag,void,void,void,void> { // ... Why do output iterators define value_type as void? It would be useful for an algorithm to know what type of value it is supposed to output. For example, a function that translates a URL query "key1=value1&key2=value2&key3=value3" into any container that holds key-value strings elements. template<typename Ch,typename Tr,typename Out> void parse(const std::basic_string<Ch,Tr>& str, Out result) { std::basic_string<Ch,Tr> key, value; // loop over str, parse into p ... *result = typename iterator_traits<Out>::value_type(key, value); } The SGI reference page of value_type hints this is because it's not possible to dereference an output iterator. But that's not the only use of value_type: I might want to instantiate one in order to assign it to the iterator.

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  • Clean solution to this ruby iterator trickiness?

    - by mstksg
    k = [1,2,3,4,5] for n in k puts n if n == 2 k.delete(n) end end puts k.join(",") # Result: # 1 # 2 # 4 # 5 # [1,3,4,5] # Desired: # 1 # 2 # 3 # 4 # 5 # [1,3,4,5] This same effect happens with the other array iterator, k.each: k = [1,2,3,4,5] k.each do |n| puts n if n == 2 k.delete(n) end end puts k.join(",") has the same output. The reason this is happening is pretty clear...Ruby doesn't actually iterate through the objects stored in the array, but rather just turns it into a pretty array index iterator, starting at index 0 and each time increasing the index until it's over. But when you delete an item, it still increments the index, so it doesn't evaluate the same index twice, which I want it to. This might not be what's happening, but it's the best I can think of. Is there a clean way to do this? Is there already a built-in iterator that can do this? Or will I have to dirty it up and do an array index iterator, and not increment when the item is deleted?

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  • How to implement iterator as an attribute of a class in Java

    - by de3
    Hi, let's say I have this simple MyArray class, with two simple methods: add, delete and an iterator. In the main method we can see how it is supposed to be used: public class MyArray { int start; int end; int[] arr; myIterator it; public MyArray(){ this.start=0; this.end=0; this.arr=new int[500]; it=new myIterator(); } public void add(int el){ this.arr[this.end]=el; this.end++; } public void delete(){ this.arr[this.start]=0; this.start++; } public static void main(String[] args){ MyArray m=new MyArray(); m.add(3); m.add(299); m.add(19); m.add(27); while(m.it.hasNext()){ System.out.println(m.it.next()); } } And then MyIterator should be implemented somehow: import java.util.Iterator; public class myIterator implements Iterator{ @Override public boolean hasNext() { // TODO Auto-generated method stub return false; } @Override public Object next() { // TODO Auto-generated method stub return null; } @Override public void remove() { // TODO Auto-generated method stub } } MyIterator should iterate arr from MyArray class, from start to end values; both are also attributes of MyArray. So, as MyIterator should use MyArray attributes, how should MyIterator be implemented? Perhaps I can send the current object in the initialization: it=new myIterator(this); But I guess it's not the best soultion. Or maybe MyArray itself should implement Iterator interface? How is this solved?

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  • Using an iterator without its container

    - by User1
    I am mixing some C and C++ libraries and have only a single pointer available to do some work in a callback function. All I need to do is iterate through a vector. Here's a simplified, untested example: bool call_back(void* data){ done=... if (!done) cout << *data++ << endl; return done; } Note that this function is in an extern "C" block in C++. call_back will be called until true is returned. I want it to cout the next element each time it's called. data is a pointer to something that I can pass from elsewhere in the code (an iterator in the above example, but can be anything). Something from data will likely be used to calculate done. I see two obvious options to give to data: Have data point to my vector. Have data point to an iterator of my vector. I can't use an iterator without having the .end() method available, right? I can't use a vector alone (unless maybe I start removing its data). I could make a struct with both vector and iterator, but is there a better way? What would you do?

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  • Java: why can't iterate over an iterator?

    - by noamtm
    I read http://stackoverflow.com/questions/839178/why-is-javas-iterator-not-an-iterable and http://stackoverflow.com/questions/27240/why-arent-enumerations-iterable, but I still don't understand why this: void foo(Iterator<X> it) { for (X x : it) { bar(x); baz(x); } } was not made possible. In other words, unless I'm missing something, the above could have been nice and valid syntactic sugar for: void foo(Iterator<X> it) { for (X x; it.hasNext();) { x = it.next(); bar(x); baz(x); } }

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  • Function template accepting nothing less than a bidirectional iterator or a pointer

    - by san
    I need a function template that accepts two iterators that could be pointers. If the two arguments are random_access iterators I want the return type to be an object of std::iterator<random_access_iterator_tag, ...> type else a std::iterator<bidirectional_iterator_tag, ...> type. I also want the code to refuse compilation if the arguments are neither a bidirectional iterator, nor a pointer. I cannot have dependency on third party libraries e.g. Boost Could you help me with the signature of this function so that it accepts bidirectional iterators as well as pointers, but not say input_iterator, output_iterator, forward_iterators. One partial solution I can think of is the following template<class T> T foo( T iter1, T iter2) { const T tmp1 = reverse_iterator<T>(iter1); const T tmp2 = reverse_iterator<T>(iter2); // do something } The idea is that if it is not bidirectional the compiler will not let me construct a reverse_iterator from it.

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  • How to convert c++ std::list element to multimap iterator

    - by user63898
    Hello all, I have std::list<multimap<std::string,std::string>::iterator> > Now i have new element: multimap<std::string,std::string>::value_type aNewMmapValue("foo1","test") I want to avoid the need to set temp multimap and do insert to the new element just to get its iterator back so i could to push it back to the: std::list<multimap<std::string,std::string>::iterator> > can i somehow avoid this creation of the temp multimap. Thanks

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  • How to crete a Java Iterator that throws IOException

    - by Antonio
    I'd like to implement an iterator that retrieves objects from disk/network. Iterator itr = getRemoteIterator(); while(itr.hasNext()) { Object element = itr.next(); System.out.print(element + " "); } However the problem is that hasNext() and next() methods of the Iterator object does not allow to throw IOException. Is there any other standard interface work around this issue? Desired code is: public interface RemoteIterator<E> { boolean hasNext() throws IOException; E next() throws IOException; void remove(); }

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  • how to use iterator in c++?

    - by tsubasa
    I'm trying to calculate distance between 2 points. The 2 points I stored in a vector in c++: (0,0) and (1,1). I'm supposed to get results as 0 1.4 1.4 0 but the actual result that I got is 0 1 -1 0 I think there's something wrong with the way I use iterator in vector. Could somebody help? I posted the code below. typedef struct point { float x; float y; } point; float distance(point *p1, point *p2) { return sqrt((p1->x - p2->x)*(p1->x - p2->x) + (p1->y - p2->y)*(p1->y - p2->y)); } int main() { vector <point> po; point p1; p1.x=0; p1.y=0; point p2; p2.x=1; p2.y=1; po.push_back(p1); po.push_back(p2); vector <point>::iterator ii; vector <point>::iterator jj; for (ii=po.begin(); ii!=po.end(); ii++) { for (jj=po.begin(); jj!=po.end(); jj++) { cout<<distance(ii,jj)<<" "; } } return 0; }

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  • [c++/STL] Selective iterator

    - by rubenvb
    FYI: no boost, yes it has this, I want to reinvent the wheel ;) Is there some form of a selective iterator (possible) in C++? What I want is to seperate strings like this: some:word{or other to a form like this: some : word { or other I can do that with two loops and find_first_of(":") and ("{") but this seems (very) inefficient to me. I thought that maybe there would be a way to create/define/write an iterator that would iterate over all these values with for_each. I fear this will have me writing a full-fledged custom way-too-complex iterator class for a std::string. So I thought maybe this would do: std::vector<size_t> list; size_t index = mystring.find(":"); while( index != std::string::npos ) { list.push_back(index); index = mystring.find(":", list.back()); } std::for_each(list.begin(), list.end(), addSpaces(mystring)); This looks messy to me, and I'm quite sure a more elegant way of doing this exists. But I can't think of it. Anyone have a bright idea? Thanks PS: I did not test the code posted, just a quick write-up of what I would try

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  • parallel computation for an Iterator of elements in Java

    - by Brian Harris
    I've had the same need a few times now and wanted to get other thoughts on the right way to structure a solution. The need is to perform some operation on many elements on many threads without needing to have all elements in memory at once, just the ones under computation. As in, Iterables.partition is insufficient because it brings all elements into memory up front. Expressing it in code, I want to write a BulkCalc2 that does the same thing as BulkCalc1, just in parallel. Below is sample code that illustrates my best attempt. I'm not satisfied because it's big and ugly, but it does seem to accomplish my goals of keeping threads highly utilized until the work is done, propagating any exceptions during computation, and not having more than numThreads instances of BigThing necessarily in memory at once. I'll accept the answer which meets the stated goals in the most concise way, whether it's a way to improve my BulkCalc2 or a completely different solution. interface BigThing { int getId(); String getString(); } class Calc { // somewhat expensive computation double calc(BigThing bigThing) { Random r = new Random(bigThing.getString().hashCode()); double d = 0; for (int i = 0; i < 100000; i++) { d += r.nextDouble(); } return d; } } class BulkCalc1 { final Calc calc; public BulkCalc1(Calc calc) { this.calc = calc; } public TreeMap<Integer, Double> calc(Iterator<BigThing> in) { TreeMap<Integer, Double> results = Maps.newTreeMap(); while (in.hasNext()) { BigThing o = in.next(); results.put(o.getId(), calc.calc(o)); } return results; } } class SafeIterator<T> { final Iterator<T> in; SafeIterator(Iterator<T> in) { this.in = in; } synchronized T nextOrNull() { if (in.hasNext()) { return in.next(); } return null; } } class BulkCalc2 { final Calc calc; final int numThreads; public BulkCalc2(Calc calc, int numThreads) { this.calc = calc; this.numThreads = numThreads; } public TreeMap<Integer, Double> calc(Iterator<BigThing> in) { ExecutorService e = Executors.newFixedThreadPool(numThreads); List<Future<?>> futures = Lists.newLinkedList(); final Map<Integer, Double> results = new MapMaker().concurrencyLevel(numThreads).makeMap(); final SafeIterator<BigThing> it = new SafeIterator<BigThing>(in); for (int i = 0; i < numThreads; i++) { futures.add(e.submit(new Runnable() { @Override public void run() { while (true) { BigThing o = it.nextOrNull(); if (o == null) { return; } results.put(o.getId(), calc.calc(o)); } } })); } e.shutdown(); for (Future<?> future : futures) { try { future.get(); } catch (InterruptedException ex) { // swallowing is OK } catch (ExecutionException ex) { throw Throwables.propagate(ex.getCause()); } } return new TreeMap<Integer, Double>(results); } }

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  • Is there a writable iterator in Java?

    - by Lukasz Lew
    In C+ one can use iterators for writing to a sequence. Simplest example would be: vector<int> v; for (vector<int>::iterator it = v.begin(); it!=v.end(); ++it) { *it = 42; } I need something more complicated - keep iterator as a class member for a later use. But I don't know how to get this behavior from Java iterators. Are there writable iterators in Java at all? If not then what replaces them?

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  • Custom iterator for dictionary?

    - by aaginor
    Hi folks, in my C#-Application, I have a Dictionary object. When iterating over the object using foreach, I naturally get each element of the dictionary. But I want only certain elements to be iterated, depending on the value of a property of MyValue. class MyValue { public bool AmIIncludedInTheIteration { get; set; } ... } Whenever AmIIncludedInTheIteration is false, the item shall not be returned by foreach. I understand that I need to implement my own iterator and override the Dictionary-Iterator somewhere. Can anyone here give me a short HowTo? Thanks in advance, Frank

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  • Building a custom iterator.

    - by Isai
    I am making this class which is a custom Map based off a hash map. I have an add method where if you add an object the object will be the key, and its value will be 1 if the object is not currently in the list. However if you add object that is currently in the list its value will be bumped up by 1. So if I added 10 strings which were all the same, the key would be that string and the value will be 10. I understand in practice when I iterate through the map, there is actually only one object to iterate, however, I am trying to create a inner class that will define an iterator that will iterate the same object however many times its value is. I can do this by simply using for loops to construct an appropriate ArrayList and just create an iterator for that, but that is too inefficient. Is there an easy or more efficient way of doing this?

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  • Strange iterator's behaviour;

    - by A-ha
    #include "stdafx.h" int _tmain(int argc, _TCHAR* argv[]) { string s = "Haven't got an idea why."; auto beg = s.begin(); auto end = s.end(); while (beg < end) { cout << *beg << '\n'; if (*beg == 'a') {//whithout if construct it works perfectly beg = s.erase(beg); } ++beg; } return 0; } Why if I erase one or more chars from this string this code breaks? I suppose it has something to do with returned iterator after erase operation being created at higher address than end iterator but I'm not sure and it surely isn't right behaviour. Or is it?

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  • Strange iterator behaviour

    - by A-ha
    #include "stdafx.h" int _tmain(int argc, _TCHAR* argv[]) { string s = "Haven't got an idea why."; auto beg = s.begin(); auto end = s.end(); while (beg < end) { cout << *beg << '\n'; if (*beg == 'a') {//whithout if construct it works perfectly beg = s.erase(beg); } ++beg; } return 0; } Why if I erase one or more chars from this string this code breaks? I suppose it has something to do with returned iterator after erase operation being created at higher address than end iterator but I'm not sure and it surely isn't right behaviour. Or is it?

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  • GDI+ crashes when loading PNG from IStream

    - by konforce
    I wrote something to load PNG files from a custom C++ IStream via GDI+. It worked great until I ran it on Vista machines. Crashes every time. When compiled on VS 2008, I found that inserting code into the IStream::AddRef method, such as a cout, made the problem go away. When compiling with VS 2010, it still crashes regardless of that. I stripped the program down to its basics. I copied a FileStream straight from Microsoft's documentation. It can load PNGs when using Bitmap::FromFile. It can load JPEGs, GIFs, and BMPs via FromFile or FromStream. So in short: on Vista, PNG files loaded via Bitmap::FromStream crash. #pragma comment(lib, "gdiplus.lib") #include <iostream> #include <objidl.h> #include <gdiplus.h> class FileStream : public IStream { public: FileStream(HANDLE hFile) { _refcount = 1; _hFile = hFile; } ~FileStream() { if (_hFile != INVALID_HANDLE_VALUE) { ::CloseHandle(_hFile); } } public: HRESULT static OpenFile(LPCWSTR pName, IStream ** ppStream, bool fWrite) { HANDLE hFile = ::CreateFileW(pName, fWrite ? GENERIC_WRITE : GENERIC_READ, FILE_SHARE_READ, NULL, fWrite ? CREATE_ALWAYS : OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL); if (hFile == INVALID_HANDLE_VALUE) return HRESULT_FROM_WIN32(GetLastError()); *ppStream = new FileStream(hFile); if(*ppStream == NULL) CloseHandle(hFile); return S_OK; } virtual HRESULT STDMETHODCALLTYPE QueryInterface(REFIID iid, void ** ppvObject) { if (iid == __uuidof(IUnknown) || iid == __uuidof(IStream) || iid == __uuidof(ISequentialStream)) { *ppvObject = static_cast<IStream*>(this); AddRef(); return S_OK; } else return E_NOINTERFACE; } virtual ULONG STDMETHODCALLTYPE AddRef(void) { return (ULONG)InterlockedIncrement(&_refcount); } virtual ULONG STDMETHODCALLTYPE Release(void) { ULONG res = (ULONG) InterlockedDecrement(&_refcount); if (res == 0) delete this; return res; } // ISequentialStream Interface public: virtual HRESULT STDMETHODCALLTYPE Read(void* pv, ULONG cb, ULONG* pcbRead) { ULONG local_pcbRead; BOOL rc = ReadFile(_hFile, pv, cb, &local_pcbRead, NULL); if (pcbRead) *pcbRead = local_pcbRead; return (rc) ? S_OK : HRESULT_FROM_WIN32(GetLastError()); } virtual HRESULT STDMETHODCALLTYPE Write(void const* pv, ULONG cb, ULONG* pcbWritten) { BOOL rc = WriteFile(_hFile, pv, cb, pcbWritten, NULL); return rc ? S_OK : HRESULT_FROM_WIN32(GetLastError()); } // IStream Interface public: virtual HRESULT STDMETHODCALLTYPE SetSize(ULARGE_INTEGER) { return E_NOTIMPL; } virtual HRESULT STDMETHODCALLTYPE CopyTo(IStream*, ULARGE_INTEGER, ULARGE_INTEGER*, ULARGE_INTEGER*) { return E_NOTIMPL; } virtual HRESULT STDMETHODCALLTYPE Commit(DWORD) { return E_NOTIMPL; } virtual HRESULT STDMETHODCALLTYPE Revert(void) { return E_NOTIMPL; } virtual HRESULT STDMETHODCALLTYPE LockRegion(ULARGE_INTEGER, ULARGE_INTEGER, DWORD) { return E_NOTIMPL; } virtual HRESULT STDMETHODCALLTYPE UnlockRegion(ULARGE_INTEGER, ULARGE_INTEGER, DWORD) { return E_NOTIMPL; } virtual HRESULT STDMETHODCALLTYPE Clone(IStream **) { return E_NOTIMPL; } virtual HRESULT STDMETHODCALLTYPE Seek(LARGE_INTEGER liDistanceToMove, DWORD dwOrigin, ULARGE_INTEGER* lpNewFilePointer) { DWORD dwMoveMethod; switch(dwOrigin) { case STREAM_SEEK_SET: dwMoveMethod = FILE_BEGIN; break; case STREAM_SEEK_CUR: dwMoveMethod = FILE_CURRENT; break; case STREAM_SEEK_END: dwMoveMethod = FILE_END; break; default: return STG_E_INVALIDFUNCTION; break; } if (SetFilePointerEx(_hFile, liDistanceToMove, (PLARGE_INTEGER) lpNewFilePointer, dwMoveMethod) == 0) return HRESULT_FROM_WIN32(GetLastError()); return S_OK; } virtual HRESULT STDMETHODCALLTYPE Stat(STATSTG* pStatstg, DWORD grfStatFlag) { if (GetFileSizeEx(_hFile, (PLARGE_INTEGER) &pStatstg->cbSize) == 0) return HRESULT_FROM_WIN32(GetLastError()); return S_OK; } private: volatile HANDLE _hFile; volatile LONG _refcount; }; #define USE_STREAM int main() { Gdiplus::GdiplusStartupInput gdiplusStartupInput; ULONG_PTR gdiplusToken; Gdiplus::GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL); Gdiplus::Bitmap *bmp; #ifndef USE_STREAM bmp = Gdiplus::Bitmap::FromFile(L"test.png", false); if (!bmp) { std::cerr << " Unable to open image file." << std::endl; return 1; } #else IStream *s; if (FileStream::OpenFile(L"test.png", &s, false) != S_OK) { std::cerr << "Unable to open image file." << std::endl; return 1; } bmp = Gdiplus::Bitmap::FromStream(s, false); #endif std::cout << "Image is " << bmp->GetWidth() << " by " << bmp->GetHeight() << std::endl; Gdiplus::GdiplusShutdown(gdiplusToken); #ifdef USE_STREAM s->Release(); #endif return 0; } Tracing and debugging, shows that it does make some calls to the IStream class. It crashes inside of lastResult = DllExports::GdipCreateBitmapFromStream(stream, &bitmap); from GdiPlusBitmap.h, which is a static inline wrapper over the flat API. Other than the reference counting, the only IStream methods it calls is stat (for file size), read, and seek. Call stack looks like: ntdll.dll!_DbgBreakPoint@0() + 0x1 bytes ntdll.dll!_RtlpBreakPointHeap@4() + 0x28 bytes ntdll.dll!_RtlpValidateHeapEntry@12() + 0x70a3c bytes ntdll.dll!_RtlDebugFreeHeap@12() + 0x9a bytes ntdll.dll!@RtlpFreeHeap@16() + 0x13cdd bytes ntdll.dll!_RtlFreeHeap@12() + 0x2e49 bytes kernel32.dll!_HeapFree@12() + 0x14 bytes ole32.dll!CRetailMalloc_Free() + 0x1c bytes ole32.dll!_CoTaskMemFree@4() + 0x13 bytes GdiPlus.dll!GpPngDecoder::GetImageInfo() + 0x68 bytes GdiPlus.dll!GpDecodedImage::InternalGetImageInfo() + 0x3c bytes GdiPlus.dll!GpDecodedImage::GetImageInfo() + 0x18 bytes GdiPlus.dll!CopyOnWriteBitmap::CopyOnWriteBitmap() + 0x49 bytes GdiPlus.dll!CopyOnWriteBitmap::Create() + 0x1d bytes GdiPlus.dll!GpBitmap::GpBitmap() + 0x2c bytes I was unable to find anybody else with the same problem, so I assume there's something wrong with my implementation...

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