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Invalid parameter implementing GetMenuItemInfoW with JNA

I am invoking the win32 API function GetMenuItemInfoW. When I invoke the function I it returns false, and Native.getLastError() returns 87:
ERROR_INVALID_PARAMETER 87 (0x57) The parameter is incorrect.
I think that my error is in my implementation of the structure MenuItemInfoW:
#Structure.FieldOrder({"cbSize", "fMask", "fType", "fState", "wId", "hSubMenu", "hBmpChecked", "hBmpUnchecked", "dwItemData", "dwTypeData", "cch", "hbmpItem"})
public class MENUITEMINFOW extends Structure {
public int cbSize;
public int fMask;
public int fType;
public int fState;
public int wId;
public Pointer hSubMenu;
public Pointer hBmpChecked;
public Pointer hBmpUnchecked;
public WinDef.ULONGByReference dwItemData;
public WString dwTypeData;
public int cch;
public Pointer hbmpItem;
public MENUITEMINFOW() {
super();
}
public MENUITEMINFOW(Pointer pointer) {
super(pointer);
}
}
And this is my code for invoking the function:
MENUITEMINFOW menuiteminfow = new MENUITEMINFOW();
menuiteminfow.fMask = 0x00000040 | 0x00000080 | 0x00000004 | 0x00000002;
menuiteminfow.fType = 0x00000000;
menuiteminfow.cch = 256;
menuiteminfow.dwTypeData = new WString(String.join("", Collections.nCopies(256, " ")));
menuiteminfow.cbSize = Native.getNativeSize(menuiteminfow.getClass());
WinDef.BOOL result = User32Ex.INSTANCE.GetMenuItemInfoW(hMenu.getPointer(), 0, true, menuiteminfow.getPointer());
if (!result.booleanValue()) {
int errorCode = Native.getLastError();
System.out.println("Error Code: " + errorCode);
}
I have edited my editing my code for your tip, but I get the same error 87. This is my new code:
MENUITEMINFOW menuiteminfow = new MENUITEMINFOW();
menuiteminfow.fMask = 0x00000040 | 0x00000080 | 0x00000004 | 0x00000002;
menuiteminfow.fType = 0x00000000;
menuiteminfow.cch = 0;
menuiteminfow.dwTypeData = Pointer.NULL;
menuiteminfow.cbSize = Native.getNativeSize(menuiteminfow.getClass());
WinDef.BOOL result = User32Ex.INSTANCE.GetMenuItemInfoW(hMenu.getPointer(),
new WinDef.UINT(0), new WinDef.BOOL(true), menuiteminfow.getPointer());
if (!result.booleanValue()) {
int errorCode = Native.getLastError();
System.out.println("Error Code: " + errorCode);
}
And this is new version of my structure:
#Structure.FieldOrder({"cbSize", "fMask", "fType", "fState", "wId", "hSubMenu", "hBmpChecked", "hBmpUnchecked", "dwItemData", "dwTypeData", "cch", "hbmpItem"})
public class MENUITEMINFOW extends Structure {
public int cbSize;
public int fMask;
public int fType;
public int fState;
public int wId;
public Pointer hSubMenu;
public Pointer hBmpChecked;
public Pointer hBmpUnchecked;
public BaseTSD.LONG_PTR dwItemData;
public Pointer dwTypeData;
public int cch;
public WinDef.HBITMAP hbmpItem;
public MENUITEMINFOW() {
super();
}
public MENUITEMINFOW(Pointer pointer) {
super(pointer);
this.read();
}
}
Thank you for your response.

Your structure mapping can be improved.
First, a ULONG_PTR is not the same as a WinDef.ULONGByReference. The ULONG_PTR is a pointer-sized value, but it does not actually point to anything.
JNA has a built-in BaseTSD.LONG_PTR type which you could use here.
While a Pointer technically works for hbmpItem and the other bitmap fields, the type WinDef.HBITMAP is already defined in JNA so you should use that mapping.
Finally, and the likely cause of your error, dwTypeData receives a String, but it is a buffer that you need to allocate and fill. From the MENUITEMINFO docs:
To retrieve a menu item of type MFT_STRING, first find the size of the string by setting the dwTypeData member of MENUITEMINFO to NULL and then calling GetMenuItemInfo. The value of cch+1 is the size needed. Then allocate a buffer of this size, place the pointer to the buffer in dwTypeData, increment cch, and call GetMenuItemInfo once again to fill the buffer with the string.
So in this case, you'd want to map a Pointer to dwTypeData, call the function the first time with that pointer set to Pointer.NULL, and then alloating memory for it based on incrementing cch:
menuiteminfow.cch++;
// allocate 2 bytes per widechar
menuiteminfow.dwTypeData = new Memory(cch * 2);
You can fetch the string from there after the function call with menuiteminfow.dwTypeData.getWideString().

Can a package final variable be changed through reflection?

Can a package final variable be changed through reflection?
Say I have this:
public class Widget {
final int val = 23;
}
Can the val be changed through reflection if made accessible?
If so, is there any way to prevent it that without using the security manager?

YES. Try this code:
public static void main(String[] args) throws Exception {
Widget w = new Widget ();
Field m = Widget.class.getDeclaredField("val");
m.setAccessible(true);
m.set(w, 233);
System.out.println(m.get(w)); /// PRINT 233
}

Turns out, changing final members causes reflection-obtained values to differ from values returned by regular code! This is quite scary.
import java.lang.reflect.Field;
public class Test {
private static final class Widget {
private final int val = 23;
public int getVal() {
return val;
}
}
public static void main(String[] args) throws Exception {
Widget w = new Widget ();
Field m = Widget.class.getDeclaredField("val");
m.setAccessible(true);
m.set(w, 233);
Field m1 = Widget.class.getDeclaredField("val");
m1.setAccessible(true);
System.out.println(m.get(w)); /// PRINT 233
System.out.println(w.getVal()); /// PRINT 23
System.out.println(m1.get(w)); /// PRINT 233
}
}

Try this.
Widget() {
checkPerMission();
}
private void checkPerMission() {
Class self = sun.reflect.Reflection.getCallerClass(1);
Class caller = sun.reflect.Reflection.getCallerClass(3);
if (self != caller) {
throw new java.lang.IllegalAccessError();
}
}

JNA getFieldOrder() results in names not matching in HashSet() comparison (JNA's Structure.java, line 925)

Running into a maddening blocking error:
Exception in thread "main" java.lang.Error: Structure.getFieldOrder() on class com.luke.generator.GeneratorEngine$VERSION_INFO returns names ([BuildString, ProtocolMajorVer, ProtocolMinorVer]) which do not match declared field names ([BiuldString, ProtocolMajorVer, ProtocolMinorVer])
at com.sun.jna.Structure.getFields(Structure.java:925)
at com.sun.jna.Structure.deriveLayout(Structure.java:1058)
at com.sun.jna.Structure.calculateSize(Structure.java:982)
at com.sun.jna.Structure.calculateSize(Structure.java:949)
at com.sun.jna.Structure.allocateMemory(Structure.java:375)
at com.sun.jna.Structure.<init>(Structure.java:184)
at com.sun.jna.Structure.<init>(Structure.java:172)
at com.sun.jna.Structure.<init>(Structure.java:159)
at com.sun.jna.Structure.<init>(Structure.java:151)
at com.luke.generator.GeneratorEngine$.<init>(GeneratorEngine.java:108)
at com.luke.generator.connectionVersion(GeneratorEngine.java:297)
at com.luke.generator.Main.main(Main.java:161)
Platform: Intel, Windows 8
JRE 1.7, 32-bit (x86)
Eclipse Kepler, Default encoding UTF-8
jna-4.1.0.jar
32-bit CPP DLL - I can confirm that I am loading the library and calling functions that do not include parameters. I also tried passing WStrings and Strings, but that did not address the issue.
Source:
CPP struct:
typedef struct {
UINT32 ProtocolMajorVer;
UINT32 ProtocolMinorVer;
UI_STRING BuildString; // Build version for the application.
} VERSION_INFO;
CPP Function
DLL_EXPORTS RETURN_TYPES ConnectionVersion (VERSION_INFO &Version) {<body omitted>}
Java code:
//Interface definition
public interface UiApi extends StdCallLibrary {
UiApi INSTANCE = (UiApi) Native.loadLibrary(UiApiPath,UiApi.class);
final String PROTOCOLMAJORVERSION = new String("ProtocolMajorVer");
final String PROTOCOLMINORVERSION = new String("ProtocolMinorVer");
final String BUILDSTRING = new String("BuildString");
public static class VERSION_INFO extends Structure {
public static class ByReference extends VERSION_INFO implements Structure.ByReference {}
public static class ByValue extends VERSION_INFO implements Structure.ByValue {}
public int ProtocolMajorVer;
public int ProtocolMinorVer;
public byte[] BiuldString;
protected List getFieldOrder() {
return Arrays.asList(new String[] { "ProtocolMajorVer","ProtocolMinorVer","BuildString" });
}
}
//Connection
public int Connect(byte[] strServerName);
public int Disconnect();
public int CloseProject();
public int ConnectionVersion(VERSION_INFO result);
public int ConnectionVersion(VERSION_INFO.ByReference result);
public int ConnectionVersion(VERSION_INFO.ByValue result);
}
//Engine.connectionVersion() method
public static int connectionVersion() {
int nReturn = 0;
String str = new String("This is my build version\n");
UiApi uiapilib;
uiapilib = UiApi.INSTANCE;
try {
UiApi.VERSION_INFO.ByReference result = new UiApi.VERSION_INFO.ByReference();
result.ProtocolMajorVer = 0;
result.ProtocolMinorVer = 0;
result.BiuldString = str.getBytes();
nReturn = uiapilib.ConnectionVersion(result);
}
catch (Exception e) {
System.out.println("Error=" + e.getLocalizedMessage());
}
return nReturn;
}
//This is the code in main that results in exception
private static Engine engine;
engine = new GeneratorEngine();
engine.connectionVersion();
I must be missing something basic. Is there something in Eclipse that could possibly be causing the HashSet name comparisons in JNA's Structure.java (line 925) that would result in names not matching? From the exception thrown, these definitions look identical.
Thanks for any tips, guidance, fresh perspectives you can offer.

Check your spelling - the field is called BiuldString not BuildString, you have the i and u reversed.

Syntax error, telling me it wants ; and several other things

Just trying to run through some code for an assignment I'm doing. It is probably simple but for the life of me I can't figure out why I get the above error at the first line
(public WaterLog.......).
Later I want to pass it this line:
[ log = new WaterLog(8, damCapacity); ]
Any help would be appreciated, I am new to this sorry.
public class WaterLog(Integer windowSize, Integer maxEntry) {
private Integer size = windowSize;
private Integer max = maxEntry;
private ArrayList theLog(int windowSize);
private int counter = 0;
public void addEntry(Integer newEntry) throws SimulationException {
theLog.add(0, newEntry);
counter++;
}
public Integer getEntry(Integer index) throws SimulationException {
If (thelog.isEmpty() || thelog.size() < index) {
return null;
}
return thelog.get(index);
}
public Integer variation() throws SimulationException {
int old, recent = 0;
recent = thelog.get(0);
old = thelog.get(thelog.size-1);
return recent-old;
}
public Integer numEntries() {
return counter;
}
}

Assuming SimulationException is defined correctly:
class WaterLog{
private Integer size;
private Integer max ;
private ArrayList<Integer> theLog; //parameterize your lists
private int counter = 0;
public WaterLog(Integer windowSize, Integer maxEntry) //this is the behavior you were looking for
{
this.size = windowSize;
this.max = maxEntry;
theLog = new ArrayList<Integer>(windowSize);
}
public void addEntry(Integer newEntry) throws SimulationException {
theLog.add(0, newEntry);
counter++;
}
public Integer getEntry(Integer index) throws SimulationException {
if (theLog.isEmpty() || theLog.size() < index) { //Java is case sensitive
return null;
}
return theLog.get(index);
}
public Integer variation() throws SimulationException {
int old, recent = 0;
recent = theLog.get(0);
old = theLog.get(theLog.size()-1); //again, watch case, also size is a method
return recent-old;
}
public Integer numEntries() {
return counter;
}
}
See the comments I added.
EDIT: To explain a bit further what was going on, let's take a look at what you were doing.
public class WaterLog(Integer windowSize, Integer maxEntry) {
private Integer size = windowSize;
private Integer max = maxEntry;
private ArrayList theLog(int windowSize);
private int counter = 0;
You seem to have confused a class with a constructor. The variables you defined were attributes, which was correct. You needed to use the syntax I showed in my answer to create a constructor. For that same reason, you don't have access to variables like windowSize. To remedy this, we allow them to still be defined outside the constructor, but assigned values inside it, where we have access to windowSize and maxEntry.

If you want to pass some parameters to this class you need a constructor. By default Each and EVERY class comes with a default constructor - which is there, you just don't see it ( but can declare it). What you can then do is make an overloaded construcotr ( which takes some arguments ) and this is what you want so..
if you have a class
class WaterLog {
// no constructor
}
the above is really a
class WaterLog {
public WaterLog() {
// this is the constructor - if you do not declare it its still here, you just dont see it. Ofcourse you have option to declare it.
}
}
The overloaded constructor is something like this
class WaterLog {
public WaterLog() {
//default constructor
}
public WaterLog(Integer int, String string, etc...) {
//overloaded constructor
}
}
and the above is what you need in order to pass arguments to this class constructor. I am not briliant at explaining things but if you need more clarification just let me know :)

JNA GetIfTable error

I need to get the index of a Network Interface in Windows.
There is NetworkInterface.getIndex() method to do this, but it's only available starting Java 7.
The requirement from the Boss is that the app needs to run in Java 6.
After some searching, I found JNA lib to call Win API functions.
The function itself is GetIfTable (http://msdn.microsoft.com/en-us/library/windows/desktop/aa365943(v=vs.85).aspx)
However, I've not been able to successfully call this function using JNA.
The return value of GetIfTable is always 122 which means ERROR_INSUFFICIENT_BUFFER. Even if I keep adding buffer it still says insufficient buffer, until when the supplied value reach certain number, then "Invalid memory access" error shows up.
Here's what I already did:
public interface IpHlpAPI extends StdCallLibrary {
IpHlpAPI INSTANCE = (IpHlpAPI) Native.loadLibrary("IpHlpAPI", IpHlpAPI.class);
public static class MIB_IFTABLE extends Structure {
public int dwNumEntries;
public MIB_IFROW table[] = new IpHlpAPI.MIB_IFROW[1];
public MIB_IFTABLE() {}
public MIB_IFTABLE(int size) {
this.allocateMemory(size);
}
#Override
protected List getFieldOrder() {
return Arrays.asList(new String[]{"dwNumEntries", "table"});
}
}
public static class MIB_IFROW extends Structure {
public char wszName[] = new char[256];
public int dwIndex;
public int dwType;
public int dwMtu;
public int dwSpeed;
public int dwPhysAddrLen;
public byte bPhysAddr[] = new byte[8];
public int dwAdminStatus;
public int dwOperStatus;
public int dwLastChange;
public int dwInOctets;
public int dwInUcastPkts;
public int dwInNUcastPkts;
public int dwInDiscards;
public int dwInErrors;
public int dwInUnknownProtos;
public int dwOutOctets;
public int dwOutUcastPkts;
public int dwOutNUcastPkts;
public int dwOutDiscards;
public int dwOutErrors;
public int dwOutQLen;
public int dwDescrLen;
public byte bDescr[] = new byte[256];
#Override
protected List getFieldOrder() {
return Arrays.asList(new String[]{"wszName", "dwIndex", "dwType", "dwMtu",
"dwSpeed", "dwPhysAddrLen", "bPhysAddr", "dwAdminStatus", "dwOperStatus",
"dwLastChange", "dwInOctets", "dwInUcastPkts", "dwInNUcastPkts", "dwInDiscards",
"dwInErrors", "dwInUnknownProtos", "dwOutOctets", "dwOutUcastPkts",
"dwOutNUcastPkts", "dwOutDiscards", "dwOutErrors", "dwOutQLen", "dwDescrLen", "bDescr"});
}
}
int GetIfTable(MIB_IFTABLE pIfTable, IntByReference pdwSize, boolean bOrder);
}
public static void main(String[] args) {
IpHlpAPI ipHlpApi = IpHlpAPI.INSTANCE;
IpHlpAPI.MIB_IFTABLE ifTable = new IpHlpAPI.MIB_IFTABLE();
IntByReference psize = new IntByReference(ifTable.size());
int status = ipHlpApi.GetIfTable(ifTable, psize, false);
if (status == 122) {
// Calculate the required number of elements in the MIB_IFROW array
ifTable = new IpHlpAPI.MIB_IFTABLE((psize.getValue() - 4) / ifTable.table[0].size());
psize.setValue(ifTable.size());
status = ipHlpApi.GetIfTable(ifTable, psize, false);
System.out.println(status);
}
System.exit(0);
}
Any ideas why is this happening?

Your input structure isn't large enough. You need to reallocate the table field to be sufficiently large based on the value returned in the pdwSize parameter.
Add a constructor to MIB_IFTABLE that indicates the size of the table array and initializes it accordingly. That will automatically give you a bigger buffer.
MIB_IFTABLE ifTable = new MIB_IFTABLE();
IntByReference psize = new IntByReference(ifTable.size());
int status = ipHlpApi.GetIfTable(ifTable, psize, false);
if (status == 122) {
// Calculate the required number of elements in the MIB_IFROW array
ifTable = new MIB_IFTABLE((psize.getValue() - 4) / ifTable.table[0].size());
psize.setValue(ifTable.size());
status = ipHlpApi.GetIfTable(ifTable, psize, false);
// If status is still 122, then there's an issue with the MIB_IFROW definition
// ...
}
EDIT
Change your constructor:
public MIB_IFTABLE(int nentries) {
this.dwNumEntries = nentries;
this.table = (MIB_IFROW[])new MIB_IFROW().toArray(nentries);
}
You should probably initialize your other ctor to have a default value for dwNumEntries; as it is you'll be passing in a default value of zero, which will guarantee you get a return value of 122 on the first call. I'm assuming dwNumEntries refers to the size of the array.