IShellFolder support

CHANGES.md

@@ -12,6 +12,7 @@ Features
 * [#512](https://github.com/java-native-access/jna/pull/512): Make loading debug flags mutable [@lwahonen](https://github.com/lwahonen).
 * [#514](https://github.com/java-native-access/jna/pull/514): Added `host_processor_info` to `com.sun.jna.platform.mac.SystemB`  - [@dbwiddis](https://github.com/dbwiddis).
 * [#519](https://github.com/java-native-access/jna/pull/519): Added JNA functional overview - [@twall](https://github.com/twall).
+* [#524](https://github.com/java-native-access/jna/pull/524): Added IShellFolder interface plus necessary utility functions to Windows platform, and a sample for enumerating objects in My Computer - [@lwahonen](https://github.com/lwahonen).
 
 Bug Fixes
 ---------

contrib/platform/src/com/sun/jna/platform/win32/COM/IEnumIDList.java

@@ -0,0 +1,229 @@
+package com.sun.jna.platform.win32.COM;
+
+/*
+ * @author L W Ahonen, lwahonen@iki.fi
+ */
+
+import com.sun.jna.Function;
+import com.sun.jna.Pointer;
+import com.sun.jna.platform.win32.Guid;
+import com.sun.jna.platform.win32.Guid.IID;
+import com.sun.jna.platform.win32.Guid.REFIID;
+import com.sun.jna.platform.win32.WinDef;
+import com.sun.jna.platform.win32.WinNT;
+import com.sun.jna.platform.win32.WinNT.HRESULT;
+import com.sun.jna.ptr.IntByReference;
+import com.sun.jna.ptr.PointerByReference;
+
+public interface IEnumIDList {
+
+    /**
+     * The interface IID for QueryInterface et al
+     */
+    public final static IID IID_IEnumIDList = new IID(
+            "{000214F2-0000-0000-C000-000000000046}");
+
+    /**
+     *
+     * Retrieves pointers to the supported interfaces on an object.
+     * This method calls IUnknown::AddRef on the pointer it returns.
+     *
+     * @param riid
+     *            The identifier of the interface being requested.
+     *
+     * @param ppvObject
+     *            The address of a pointer variable that receives the interface pointer requested in the riid parameter. Upon successful
+     *            return, *ppvObject contains the requested interface pointer to the object. If the object does not support the
+     *            interface, *ppvObject is set to NULL.
+     *
+     * @return
+     *            This method returns S_OK if the interface is supported, and E_NOINTERFACE otherwise. If ppvObject is NULL, this method returns E_POINTER.
+     *            For any one object, a specific query for the IUnknown interface on any of the object's interfaces must always return the same pointer value.
+     *            This enables a client to determine whether two pointers point to the same component by calling QueryInterfacewith IID_IUnknown
+     *            and comparing the results. It is specifically not the case that queries for interfaces other than IUnknown (even the same interface
+     *            through the same pointer) must return the same pointer value.
+     *
+     *            There are four requirements for implementations of QueryInterface (In these cases, "must succeed" means "must succeed barring
+     *            catastrophic failure."):
+     *            The set of interfaces accessible on an object through QueryInterface must be static, not dynamic. This means that if a call
+     *            toQueryInterface for a pointer to a specified interface succeeds the first time, it must succeed again, and if it fails
+     *            the first time, it must fail on all subsequent queries.

+     *
+     *            It must be reflexive: if a client holds a pointer to an interface on an object, and queries for that interface, the call must succeed.

+     *
+     *            It must be symmetric: if a client holding a pointer to one interface queries successfully for another, a query through
+     *            the obtained pointer for the first interface must succeed.

+     *
+     *            It must be transitive: if a client holding a pointer to one interface queries successfully for a second, and through that
+     *            pointer queries successfully for a third interface, a query for the first interface through the pointer for the
+     *            third interface must succeed.

+     *            Notes to Implementers
+     *            Implementations of QueryInterface must never check ACLs. The main reason for this rule is that COM requires that an object supporting a
+     *            particular interface always return success when queried for that interface. Another reason is that checking ACLs on QueryInterface
+     *            does not provide any real security because any client who has access to a particular interface can hand it directly to another
+     *            client without any calls back to the server. Also, because COM caches interface pointers, it does not callQueryInterface on
+     *            the server every time a client does a query.
+     */
+    HRESULT QueryInterface(
+            REFIID riid,
+            PointerByReference ppvObject);
+
+    /**
+     *
+     * Increments the reference count for an interface on an object. This method should be called for every new copy of a pointer to an interface on an object.
+     * @return
+     *            The method returns the new reference count. This value is intended to be used only for test purposes.
+     *
+     *            Objects use a reference counting mechanism to ensure that the lifetime of the object includes the lifetime of references to it. You use AddRef
+     *            to stabilize a copy of an interface pointer. It can also be called when the life of a cloned pointer must extend beyond the
+     *            lifetime of the original pointer. The cloned pointer must be released by calling IUnknown::Release.
+     *
+     *            The internal reference counter that AddRef maintains should be a 32-bit unsigned integer.
+     *            Notes to Callers
+     *            Call this method for every new copy of an interface pointer that you make. For example, if you are passing a copy of a pointer
+     *            back from a method, you must call AddRef on that pointer. You must also call AddRef on a pointer before passing it as an in-out
+     *            parameter to a method; the method will call IUnknown::Release before copying the out-value on top of it.
+     */
+    int AddRef();
+
+    /**
+     * Decrements the reference count for an interface on an object.
+     *
+     * @return
+     *            The method returns the new reference count. This value is intended to be used only for test purposes.
+     *
+     *            When the reference count on an object reaches zero, Release must cause the interface pointer to free itself. When the released
+     *            pointer is the only existing reference to an object (whether the object supports single or multiple interfaces), the
+     *            implementation must free the object.
+     *
+     *            Note that aggregation of objects restricts the ability to recover interface pointers.
+     *            Notes to Callers
+     *            Call this method when you no longer need to use an interface pointer. If you are writing a method that takes an in-out
+     *            parameter, call Release on the pointer you are passing in before copying the out-value on top of it.
+     */
+    int Release();
+
+    /*
+    Retrieves the specified number of item identifiers in the enumeration sequence and advances the current position by the number of items retrieved.
+     * @param celt
+     *            The number of elements in the array referenced by the rgelt parameter.
+     * @param rgelt
+     *            The address of a pointer to an array of ITEMIDLIST pointers that receive the item identifiers.
+     *            The implementation must allocate these item identifiers using CoTaskMemAlloc.
+     *            The calling application is responsible for freeing the item identifiers using CoTaskMemFree.
+     *            The ITEMIDLIST structures returned in the array are relative to the IShellFolder being enumerated.
+     * @param pceltFetched
+     *            A pointer to a value that receives a count of the item identifiers actually returned in rgelt.
+     *            The count can be smaller than the value specified in the celt parameter. This parameter can be NULL on entry only if celt = 1,
+     *            because in that case the method can only retrieve one (S_OK) or zero (S_FALSE) items.
+     *
+     * @return HRESULT
+     *            Returns S_OK if the method successfully retrieved the requested celt elements.
+     *            This method only returns S_OK if the full count of requested items are successfully retrieved.
+     *            S_FALSE indicates that more items were requested than remained in the enumeration.
+     *            The value pointed to by the pceltFetched parameter specifies the actual number of items retrieved.
+     *            Note that the value will be 0 if there are no more items to retrieve.
+     *            Returns a COM-defined error value otherwise.
+     *
+     *            If this method returns a Component Object Model (COM) error code (as determined by the COMUtils.FAILED macro),
+     *            then no entries in the rgelt array are valid on exit. If this method returns a success code (such as S_OK or S_FALSE),
+     *            then the ULONG pointed to by the pceltFetched parameter determines how many entries in the rgelt array are valid on exit.
+     *
+     *            The distinction is important in the case where celt > 1. For example, if you pass celt=10 and there are only 3 elements left,
+     *            *pceltFetched will be 3 and the method will return S_FALSE meaning that you reached the end of the file.
+     *            The three fetched elements will be stored into rgelt and are valid.
+     */
+    HRESULT Next(
+            int celt,
+            PointerByReference rgelt,
+            IntByReference pceltFetched);
+
+    /**
+     * Skips the specified number of elements in the enumeration sequence.
+     * @param celt
+     *            The number of item identifiers to skip.
+     * @return HRESULT
+     *            Returns S_OK if successful, or a COM-defined error value otherwise.
+     */
+    HRESULT Skip(
+            int celt);
+
+    /**
+     * Returns to the beginning of the enumeration sequence.
+     * @return HRESULT
+     *            Returns S_OK if successful, or a COM-defined error value otherwise.
+     */
+
+    HRESULT Reset();
+
+    /**
+     * Creates a new item enumeration object with the same contents and state as the current one.
+     * @param ppenum
+     *                The address of a pointer to the new enumeration object. The calling application must eventually free the new object by calling its Release member function.
+     * @return HRESULT
+     *            Returns S_OK if successful, or a COM-defined error value otherwise.
+     */
+    HRESULT Clone(
+            PointerByReference ppenum);
+
+
+    /*
+    Use this like:
+
+    PointerByReference pbr=new PointerByReference();
+    HRESULT result=SomeCOMObject.QueryInterface(IID_IEnumIDList, pbr);
+    if(COMUtils.SUCCEEDED(result)) IENumIDList eil=IEnumIDList.Converter.PointerToIEnumIDList(pbr);
+
+     */
+    public static class Converter {
+        public static IEnumIDList PointerToIEnumIDList(final PointerByReference ptr) {
+            final Pointer interfacePointer = ptr.getValue();
+            final Pointer vTablePointer = interfacePointer.getPointer(0);
+            final Pointer[] vTable = new Pointer[7];
+            vTablePointer.read(0, vTable, 0, 7);
+            return new IEnumIDList() {
+
+                @Override
+                public WinNT.HRESULT QueryInterface(REFIID byValue, PointerByReference pointerByReference) {
+                    Function f = Function.getFunction(vTable[0], Function.ALT_CONVENTION);
+                    return new WinNT.HRESULT(f.invokeInt(new Object[]{interfacePointer, byValue, pointerByReference}));
+                }
+
+                @Override
+                public int AddRef() {
+                    Function f = Function.getFunction(vTable[1], Function.ALT_CONVENTION);
+                    return f.invokeInt(new Object[]{interfacePointer});
+                }
+
+                public int Release() {
+                    Function f = Function.getFunction(vTable[2], Function.ALT_CONVENTION);
+                    return f.invokeInt(new Object[]{interfacePointer});
+                }
+
+                @Override
+                public HRESULT Next(int celt, PointerByReference rgelt, IntByReference pceltFetched) {
+                    Function f = Function.getFunction(vTable[3], Function.ALT_CONVENTION);
+                    return new HRESULT(f.invokeInt(new Object[]{interfacePointer, celt, rgelt, pceltFetched}));
+                }
+
+                @Override
+                public HRESULT Skip(int celt) {
+                    Function f = Function.getFunction(vTable[4], Function.ALT_CONVENTION);
+                    return new HRESULT(f.invokeInt(new Object[]{interfacePointer, celt}));
+                }
+
+                @Override
+                public HRESULT Reset() {
+                    Function f = Function.getFunction(vTable[5], Function.ALT_CONVENTION);
+                    return new HRESULT(f.invokeInt(new Object[]{interfacePointer}));
+                }
+
+                @Override
+                public HRESULT Clone(PointerByReference ppenum) {
+                    Function f = Function.getFunction(vTable[6], Function.ALT_CONVENTION);
+                    return new HRESULT(f.invokeInt(new Object[]{interfacePointer, ppenum}));
+                }
+            };
+        }
+    }
+}