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Unexpected error when unit testing nested JNA Structure objects


Iterating through a Collection, avoiding ConcurrentModificationException when removing objects in a loopHow to unit test abstract classes: extend with stubs?“cannot find symbol method drawImage(java.awt.image.BufferedImage,<nulltype>,int,int)”linux to windows C++ byte arrayJUnit test of the same objectWhy this class should implement java.io.Serializable when I using hibernate?Type mismatch in key from map: expected .. Text, received … LongWritablewhy spill failure happens for Custom Data Type in HadoopFatal error with JNA structureWhen I run The Junit Test Case in Eclispe I am getting The errr






.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;








1















The following unit test is intended to verify that a nested JNA data structure is properly parsed based on the data that gets passed into the constructor. The unit test properly checks when JNA initializes the 'parent' structure. However, the test fails when testing member variables of a nested structure. I suspect the problem to be that the unit test sets a pointer to a memory location that contains the data for the nested structure. Perhaps the Java Pointer isn't translating one-to-one to how C does it.



I tried placing the WlanBssEntry at the start of WlanBssEntry[] but that didn't provide any different results than how it is currently implemented. When I tried placing it contiguously, I did not call pointerToMem.setPointer(8, ...)



This is the unit test:



package com.sevensignal.EyeQAgent.Util.win32.struct;

import com.sevensignal.EyeQAgent.Models.Platform;
import com.sevensignal.EyeQAgent.Util.Utils;
import com.sun.jna.Memory;
import com.sun.jna.Pointer;
import com.sun.jna.platform.win32.WinDef;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

import static org.hamcrest.CoreMatchers.equalTo;
import static org.junit.Assert.*;
import static org.junit.Assume.assumeThat;

@RunWith(PowerMockRunner.class)
@PrepareForTest(Utils.class)
public class WlanBssListTest 

 Pointer pWlanBssList;

 private final static long OFFSET_TO_FIRST_WLAN_BSS_ENTRY = 1024;

 @Before
 public void setUp() 
 assumeThat(Utils.getPlatform(), equalTo(Platform.WINDOWS));
 pWlanBssList = allocateMemory(65536);
 initWlanBssEntryMemory(pWlanBssList, OFFSET_TO_FIRST_WLAN_BSS_ENTRY, 50);
 initWlanBssListMemory(pWlanBssList, 12, 1, OFFSET_TO_FIRST_WLAN_BSS_ENTRY);
 

 @Test
 public void shouldSetTotalSize() 
 WlanBssList subject = new WlanBssList(pWlanBssList);
 assertEquals("should set total size", new WinDef.DWORD(12), subject.dwTotalSize);
 

 @Test
 public void shouldSetNumberOfItems() 
 WlanBssList subject = new WlanBssList(pWlanBssList);
 assertEquals("should set number of items", new WinDef.DWORD(1), subject.dwNumberOfItems);
 

 @Test
 public void shouldInitWlanBssEntries() 
 WlanBssList subject = new WlanBssList(pWlanBssList);
 assertEquals("should init WLAN BSS Entries", 1, subject.wlanBssEntries.length);
 assertEquals("should init WLAN BSS Entry data struct", new WinDef.LONG(50), subject.wlanBssEntries[0].uPhyId);
 

 @Test
 public void shouldInitWlanBssEntriesWhenNoEntriesExist() 
 pWlanBssList.setInt(4, 0);
 WlanBssList subject = new WlanBssList(pWlanBssList);
 assertEquals("should init WLAN BSS Entries when no entries exist", 0, subject.wlanBssEntries.length);
 

 private Pointer allocateMemory(long size) 
 return new Memory(size).share(0);
 

 private void initWlanBssListMemory(Pointer pointerToMem, int dwTotalSize, int dwNumberOfItems, long offsetToWlanBssEntry) 
 pointerToMem.setInt(0, dwTotalSize);
 pointerToMem.setInt(4, dwNumberOfItems);
 pointerToMem.setPointer(8, pointerToMem.share(offsetToWlanBssEntry));
 

 private void initWlanBssEntryMemory(Pointer pointerToMem, long offsetToWlanBssEntry, long uPhyId) 
 final int PHY_ID_OFFSET = 40;
 pointerToMem.setLong(offsetToWlanBssEntry + 0, 3);
 pointerToMem.setByte(offsetToWlanBssEntry + 8, (byte)'T');
 pointerToMem.setByte(offsetToWlanBssEntry + 9, (byte)'S');
 pointerToMem.setByte(offsetToWlanBssEntry + 10, (byte)'T');
 pointerToMem.setLong(offsetToWlanBssEntry + PHY_ID_OFFSET, uPhyId);



This is the WlanBssList class which is the highest level structure:



package com.sevensignal.EyeQAgent.Util.win32.struct;

import com.sun.jna.Pointer;
import com.sun.jna.Structure;
import com.sun.jna.platform.win32.WinDef.DWORD;

import java.util.Arrays;
import java.util.List;

public class WlanBssList extends Structure 

 public DWORD dwTotalSize;
 public DWORD dwNumberOfItems;
 public WlanBssEntry[] wlanBssEntries;

 public static class ByReference extends WlanBssList implements Structure.ByReference
 
 public ByReference()
 

 

 public ByReference(Pointer p)
 
 super(p);
 
 

 public WlanBssList() 
 wlanBssEntries = new WlanBssEntry[1];
 

 public WlanBssList(Pointer p) 
 super(p);
 dwTotalSize = new DWORD(p.getInt(0));
 dwNumberOfItems = new DWORD(p.getInt(4));
 if(dwNumberOfItems.intValue() > 0) 
 wlanBssEntries = new WlanBssEntry[dwNumberOfItems.intValue()];
 readField("wlanBssEntries");
 else 
 wlanBssEntries = new WlanBssEntry[0];
 
 

 @Override
 protected List<String> getFieldOrder() 
 return Arrays.asList("dwTotalSize", "dwNumberOfItems", "wlanBssEntries");



And these are the nested structures:



package com.sevensignal.EyeQAgent.Util.win32.struct;

import com.sevensignal.EyeQAgent.Models.InformationElementGetter;
import com.sun.jna.Structure;
import com.sun.jna.platform.win32.WinDef.LONG;
import com.sun.jna.platform.win32.WinDef.ULONG;
import com.sun.jna.platform.win32.WinDef.ULONGLONG;
import com.sun.jna.platform.win32.WinDef.USHORT;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.NoArgsConstructor;

import java.util.Arrays;
import java.util.List;

@Builder
@NoArgsConstructor
@AllArgsConstructor
public class WlanBssEntry extends Structure implements InformationElementGetter 

 public DOT11_SSID dot11Ssid;
 public ULONG uPhyId;
 public DOT11_MAC_ADDRESS dot11Bssid;
 public int dot11BssType;
 public int dot11BssPhyType;
 public LONG lRssi;
 public ULONG uLinkQuality;
 public boolean bInRegDomain;
 public USHORT usBeaconPeriod;
 public ULONGLONG ullTimestamp;
 public ULONGLONG ullHostTimestamp;
 public USHORT usCapabilityInformation;
 public ULONG ulChCenterFrequency;
 public WlanRateSet wlanRateSet;
 public ULONG ulIeOffset;
 public ULONG ulIeSize;

 @Override
 protected List<String> getFieldOrder()
 
 return Arrays.asList("dot11Ssid",
 "uPhyId",
 "dot11Bssid",
 "dot11BssType",
 "dot11BssPhyType",
 "lRssi",
 "uLinkQuality",
 "bInRegDomain",
 "usBeaconPeriod",
 "ullTimestamp",
 "ullHostTimestamp",
 "usCapabilityInformation",
 "ulChCenterFrequency",
 "wlanRateSet",
 "ulIeOffset",
 "ulIeSize");
 

 public byte[] getInformationElement() 
 return this.getPointer()
 .getByteArray(this.ulIeOffset.intValue(), this.ulIeSize.intValue());
 



package com.sevensignal.EyeQAgent.Util.win32.struct;

import com.sun.jna.Structure;
import com.sun.jna.platform.win32.WinDef.*;

import java.util.Arrays;
import java.util.List;

public class DOT11_SSID extends Structure

 public static class ByReference extends DOT11_SSID implements Structure.ByReference
 

 

 public static int DOT11_SSID_MAX_LENGTH = 32;

 /**
 * The length, in bytes, of the ucSSID array.
 */
 public ULONG uSSIDLength;

 /**
 * The SSID. DOT11_SSID_MAX_LENGTH is set to 32.
 */
 public byte[] ucSSID;

 public DOT11_SSID()
 
 ucSSID = new byte[DOT11_SSID_MAX_LENGTH];
 

 @Override
 protected List<String> getFieldOrder()
 
 return Arrays.asList("uSSIDLength", "ucSSID");
 

 @Override
 public String toString() 
 if(uSSIDLength != null) 
 int ssidArrayLength = uSSIDLength.intValue();
 if (ssidArrayLength > DOT11_SSID_MAX_LENGTH) 
 ssidArrayLength = DOT11_SSID_MAX_LENGTH;
 

 return new String(Arrays.copyOfRange(ucSSID, 0, ssidArrayLength));
 else 
 return "";



The results of the unit test are:



java.lang.AssertionError: should init WLAN BSS Entry data struct 
Expected :50
Actual :0


The assertion that fails is:



assertEquals("should init WLAN BSS Entry data struct", new WinDef.LONG(50), subject.wlanBssEntries[0].uPhyId);






java windows junit jna







share|improve this question



















  • 1





    Welcome to Stack Overflow! I'm not sure but think your array initialization wlanBssEntries = new WlanBssEntry[dwNumberOfItems.intValue()]; won't work. You should do wlanBssEntries = (new WlanBssEntry()).toArray(dwNumberOfItems.intValue());. (Also JNA doesn't support 0 length arrays so the second part of your conditional is impossible: always initialize with at least 1 element.)

    – Daniel Widdis
    Mar 27 at 21:06






  • 1





    to be more clear, the new foo[] structure array only works on the Java side and does not initialize the structure object. You would have to initialize every individual foo in the array (non-contiguous native memory which wouldn't work well as an array parameter) or use toArray() to initialize the structures with contiguous native memory.

    – Daniel Widdis
    Mar 27 at 21:14






  • 1





    JNA iterates over the fields in your FieldOrder list, using reflection to get the mapped class so it knows their native size so it knows the offset. Are you sure your calculated offsets are correct?

    – Daniel Widdis
    Mar 28 at 15:39






  • 1





    I figured it out. I'll post my answer later but wanted to let you know so you don't spend your valuable time. In short, my problem was two fold. First, I did have an offset problem in the data that I was initializing. Second, I didn't place the data I was initializing at the "end" of the WlanBssList (starting at offset 8). Thank you for your help. Your mention of toArray helped and having another sounding board was all it took.

    – Aaron Bauman
    Mar 28 at 18:15






  • 1





    Glad you fixed it and that I could help!

    – Daniel Widdis
    Mar 28 at 18:33

















1















The following unit test is intended to verify that a nested JNA data structure is properly parsed based on the data that gets passed into the constructor. The unit test properly checks when JNA initializes the 'parent' structure. However, the test fails when testing member variables of a nested structure. I suspect the problem to be that the unit test sets a pointer to a memory location that contains the data for the nested structure. Perhaps the Java Pointer isn't translating one-to-one to how C does it.



I tried placing the WlanBssEntry at the start of WlanBssEntry[] but that didn't provide any different results than how it is currently implemented. When I tried placing it contiguously, I did not call pointerToMem.setPointer(8, ...)



This is the unit test:



package com.sevensignal.EyeQAgent.Util.win32.struct;

import com.sevensignal.EyeQAgent.Models.Platform;
import com.sevensignal.EyeQAgent.Util.Utils;
import com.sun.jna.Memory;
import com.sun.jna.Pointer;
import com.sun.jna.platform.win32.WinDef;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

import static org.hamcrest.CoreMatchers.equalTo;
import static org.junit.Assert.*;
import static org.junit.Assume.assumeThat;

@RunWith(PowerMockRunner.class)
@PrepareForTest(Utils.class)
public class WlanBssListTest 

 Pointer pWlanBssList;

 private final static long OFFSET_TO_FIRST_WLAN_BSS_ENTRY = 1024;

 @Before
 public void setUp() 
 assumeThat(Utils.getPlatform(), equalTo(Platform.WINDOWS));
 pWlanBssList = allocateMemory(65536);
 initWlanBssEntryMemory(pWlanBssList, OFFSET_TO_FIRST_WLAN_BSS_ENTRY, 50);
 initWlanBssListMemory(pWlanBssList, 12, 1, OFFSET_TO_FIRST_WLAN_BSS_ENTRY);
 

 @Test
 public void shouldSetTotalSize() 
 WlanBssList subject = new WlanBssList(pWlanBssList);
 assertEquals("should set total size", new WinDef.DWORD(12), subject.dwTotalSize);
 

 @Test
 public void shouldSetNumberOfItems() 
 WlanBssList subject = new WlanBssList(pWlanBssList);
 assertEquals("should set number of items", new WinDef.DWORD(1), subject.dwNumberOfItems);
 

 @Test
 public void shouldInitWlanBssEntries() 
 WlanBssList subject = new WlanBssList(pWlanBssList);
 assertEquals("should init WLAN BSS Entries", 1, subject.wlanBssEntries.length);
 assertEquals("should init WLAN BSS Entry data struct", new WinDef.LONG(50), subject.wlanBssEntries[0].uPhyId);
 

 @Test
 public void shouldInitWlanBssEntriesWhenNoEntriesExist() 
 pWlanBssList.setInt(4, 0);
 WlanBssList subject = new WlanBssList(pWlanBssList);
 assertEquals("should init WLAN BSS Entries when no entries exist", 0, subject.wlanBssEntries.length);
 

 private Pointer allocateMemory(long size) 
 return new Memory(size).share(0);
 

 private void initWlanBssListMemory(Pointer pointerToMem, int dwTotalSize, int dwNumberOfItems, long offsetToWlanBssEntry) 
 pointerToMem.setInt(0, dwTotalSize);
 pointerToMem.setInt(4, dwNumberOfItems);
 pointerToMem.setPointer(8, pointerToMem.share(offsetToWlanBssEntry));
 

 private void initWlanBssEntryMemory(Pointer pointerToMem, long offsetToWlanBssEntry, long uPhyId) 
 final int PHY_ID_OFFSET = 40;
 pointerToMem.setLong(offsetToWlanBssEntry + 0, 3);
 pointerToMem.setByte(offsetToWlanBssEntry + 8, (byte)'T');
 pointerToMem.setByte(offsetToWlanBssEntry + 9, (byte)'S');
 pointerToMem.setByte(offsetToWlanBssEntry + 10, (byte)'T');
 pointerToMem.setLong(offsetToWlanBssEntry + PHY_ID_OFFSET, uPhyId);



This is the WlanBssList class which is the highest level structure:



package com.sevensignal.EyeQAgent.Util.win32.struct;

import com.sun.jna.Pointer;
import com.sun.jna.Structure;
import com.sun.jna.platform.win32.WinDef.DWORD;

import java.util.Arrays;
import java.util.List;

public class WlanBssList extends Structure 

 public DWORD dwTotalSize;
 public DWORD dwNumberOfItems;
 public WlanBssEntry[] wlanBssEntries;

 public static class ByReference extends WlanBssList implements Structure.ByReference
 
 public ByReference()
 

 

 public ByReference(Pointer p)
 
 super(p);
 
 

 public WlanBssList() 
 wlanBssEntries = new WlanBssEntry[1];
 

 public WlanBssList(Pointer p) 
 super(p);
 dwTotalSize = new DWORD(p.getInt(0));
 dwNumberOfItems = new DWORD(p.getInt(4));
 if(dwNumberOfItems.intValue() > 0) 
 wlanBssEntries = new WlanBssEntry[dwNumberOfItems.intValue()];
 readField("wlanBssEntries");
 else 
 wlanBssEntries = new WlanBssEntry[0];
 
 

 @Override
 protected List<String> getFieldOrder() 
 return Arrays.asList("dwTotalSize", "dwNumberOfItems", "wlanBssEntries");



And these are the nested structures:



package com.sevensignal.EyeQAgent.Util.win32.struct;

import com.sevensignal.EyeQAgent.Models.InformationElementGetter;
import com.sun.jna.Structure;
import com.sun.jna.platform.win32.WinDef.LONG;
import com.sun.jna.platform.win32.WinDef.ULONG;
import com.sun.jna.platform.win32.WinDef.ULONGLONG;
import com.sun.jna.platform.win32.WinDef.USHORT;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.NoArgsConstructor;

import java.util.Arrays;
import java.util.List;

@Builder
@NoArgsConstructor
@AllArgsConstructor
public class WlanBssEntry extends Structure implements InformationElementGetter 

 public DOT11_SSID dot11Ssid;
 public ULONG uPhyId;
 public DOT11_MAC_ADDRESS dot11Bssid;
 public int dot11BssType;
 public int dot11BssPhyType;
 public LONG lRssi;
 public ULONG uLinkQuality;
 public boolean bInRegDomain;
 public USHORT usBeaconPeriod;
 public ULONGLONG ullTimestamp;
 public ULONGLONG ullHostTimestamp;
 public USHORT usCapabilityInformation;
 public ULONG ulChCenterFrequency;
 public WlanRateSet wlanRateSet;
 public ULONG ulIeOffset;
 public ULONG ulIeSize;

 @Override
 protected List<String> getFieldOrder()
 
 return Arrays.asList("dot11Ssid",
 "uPhyId",
 "dot11Bssid",
 "dot11BssType",
 "dot11BssPhyType",
 "lRssi",
 "uLinkQuality",
 "bInRegDomain",
 "usBeaconPeriod",
 "ullTimestamp",
 "ullHostTimestamp",
 "usCapabilityInformation",
 "ulChCenterFrequency",
 "wlanRateSet",
 "ulIeOffset",
 "ulIeSize");
 

 public byte[] getInformationElement() 
 return this.getPointer()
 .getByteArray(this.ulIeOffset.intValue(), this.ulIeSize.intValue());
 



package com.sevensignal.EyeQAgent.Util.win32.struct;

import com.sun.jna.Structure;
import com.sun.jna.platform.win32.WinDef.*;

import java.util.Arrays;
import java.util.List;

public class DOT11_SSID extends Structure

 public static class ByReference extends DOT11_SSID implements Structure.ByReference
 

 

 public static int DOT11_SSID_MAX_LENGTH = 32;

 /**
 * The length, in bytes, of the ucSSID array.
 */
 public ULONG uSSIDLength;

 /**
 * The SSID. DOT11_SSID_MAX_LENGTH is set to 32.
 */
 public byte[] ucSSID;

 public DOT11_SSID()
 
 ucSSID = new byte[DOT11_SSID_MAX_LENGTH];
 

 @Override
 protected List<String> getFieldOrder()
 
 return Arrays.asList("uSSIDLength", "ucSSID");
 

 @Override
 public String toString() 
 if(uSSIDLength != null) 
 int ssidArrayLength = uSSIDLength.intValue();
 if (ssidArrayLength > DOT11_SSID_MAX_LENGTH) 
 ssidArrayLength = DOT11_SSID_MAX_LENGTH;
 

 return new String(Arrays.copyOfRange(ucSSID, 0, ssidArrayLength));
 else 
 return "";



The results of the unit test are:



java.lang.AssertionError: should init WLAN BSS Entry data struct 
Expected :50
Actual :0


The assertion that fails is:



assertEquals("should init WLAN BSS Entry data struct", new WinDef.LONG(50), subject.wlanBssEntries[0].uPhyId);






java windows junit jna







share|improve this question



















  • 1





    Welcome to Stack Overflow! I'm not sure but think your array initialization wlanBssEntries = new WlanBssEntry[dwNumberOfItems.intValue()]; won't work. You should do wlanBssEntries = (new WlanBssEntry()).toArray(dwNumberOfItems.intValue());. (Also JNA doesn't support 0 length arrays so the second part of your conditional is impossible: always initialize with at least 1 element.)

    – Daniel Widdis
    Mar 27 at 21:06






  • 1





    to be more clear, the new foo[] structure array only works on the Java side and does not initialize the structure object. You would have to initialize every individual foo in the array (non-contiguous native memory which wouldn't work well as an array parameter) or use toArray() to initialize the structures with contiguous native memory.

    – Daniel Widdis
    Mar 27 at 21:14






  • 1





    JNA iterates over the fields in your FieldOrder list, using reflection to get the mapped class so it knows their native size so it knows the offset. Are you sure your calculated offsets are correct?

    – Daniel Widdis
    Mar 28 at 15:39






  • 1





    I figured it out. I'll post my answer later but wanted to let you know so you don't spend your valuable time. In short, my problem was two fold. First, I did have an offset problem in the data that I was initializing. Second, I didn't place the data I was initializing at the "end" of the WlanBssList (starting at offset 8). Thank you for your help. Your mention of toArray helped and having another sounding board was all it took.

    – Aaron Bauman
    Mar 28 at 18:15






  • 1





    Glad you fixed it and that I could help!

    – Daniel Widdis
    Mar 28 at 18:33













1












1








1








The following unit test is intended to verify that a nested JNA data structure is properly parsed based on the data that gets passed into the constructor. The unit test properly checks when JNA initializes the 'parent' structure. However, the test fails when testing member variables of a nested structure. I suspect the problem to be that the unit test sets a pointer to a memory location that contains the data for the nested structure. Perhaps the Java Pointer isn't translating one-to-one to how C does it.



I tried placing the WlanBssEntry at the start of WlanBssEntry[] but that didn't provide any different results than how it is currently implemented. When I tried placing it contiguously, I did not call pointerToMem.setPointer(8, ...)



This is the unit test:



package com.sevensignal.EyeQAgent.Util.win32.struct;

import com.sevensignal.EyeQAgent.Models.Platform;
import com.sevensignal.EyeQAgent.Util.Utils;
import com.sun.jna.Memory;
import com.sun.jna.Pointer;
import com.sun.jna.platform.win32.WinDef;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

import static org.hamcrest.CoreMatchers.equalTo;
import static org.junit.Assert.*;
import static org.junit.Assume.assumeThat;

@RunWith(PowerMockRunner.class)
@PrepareForTest(Utils.class)
public class WlanBssListTest 

 Pointer pWlanBssList;

 private final static long OFFSET_TO_FIRST_WLAN_BSS_ENTRY = 1024;

 @Before
 public void setUp() 
 assumeThat(Utils.getPlatform(), equalTo(Platform.WINDOWS));
 pWlanBssList = allocateMemory(65536);
 initWlanBssEntryMemory(pWlanBssList, OFFSET_TO_FIRST_WLAN_BSS_ENTRY, 50);
 initWlanBssListMemory(pWlanBssList, 12, 1, OFFSET_TO_FIRST_WLAN_BSS_ENTRY);
 

 @Test
 public void shouldSetTotalSize() 
 WlanBssList subject = new WlanBssList(pWlanBssList);
 assertEquals("should set total size", new WinDef.DWORD(12), subject.dwTotalSize);
 

 @Test
 public void shouldSetNumberOfItems() 
 WlanBssList subject = new WlanBssList(pWlanBssList);
 assertEquals("should set number of items", new WinDef.DWORD(1), subject.dwNumberOfItems);
 

 @Test
 public void shouldInitWlanBssEntries() 
 WlanBssList subject = new WlanBssList(pWlanBssList);
 assertEquals("should init WLAN BSS Entries", 1, subject.wlanBssEntries.length);
 assertEquals("should init WLAN BSS Entry data struct", new WinDef.LONG(50), subject.wlanBssEntries[0].uPhyId);
 

 @Test
 public void shouldInitWlanBssEntriesWhenNoEntriesExist() 
 pWlanBssList.setInt(4, 0);
 WlanBssList subject = new WlanBssList(pWlanBssList);
 assertEquals("should init WLAN BSS Entries when no entries exist", 0, subject.wlanBssEntries.length);
 

 private Pointer allocateMemory(long size) 
 return new Memory(size).share(0);
 

 private void initWlanBssListMemory(Pointer pointerToMem, int dwTotalSize, int dwNumberOfItems, long offsetToWlanBssEntry) 
 pointerToMem.setInt(0, dwTotalSize);
 pointerToMem.setInt(4, dwNumberOfItems);
 pointerToMem.setPointer(8, pointerToMem.share(offsetToWlanBssEntry));
 

 private void initWlanBssEntryMemory(Pointer pointerToMem, long offsetToWlanBssEntry, long uPhyId) 
 final int PHY_ID_OFFSET = 40;
 pointerToMem.setLong(offsetToWlanBssEntry + 0, 3);
 pointerToMem.setByte(offsetToWlanBssEntry + 8, (byte)'T');
 pointerToMem.setByte(offsetToWlanBssEntry + 9, (byte)'S');
 pointerToMem.setByte(offsetToWlanBssEntry + 10, (byte)'T');
 pointerToMem.setLong(offsetToWlanBssEntry + PHY_ID_OFFSET, uPhyId);



This is the WlanBssList class which is the highest level structure:



package com.sevensignal.EyeQAgent.Util.win32.struct;

import com.sun.jna.Pointer;
import com.sun.jna.Structure;
import com.sun.jna.platform.win32.WinDef.DWORD;

import java.util.Arrays;
import java.util.List;

public class WlanBssList extends Structure 

 public DWORD dwTotalSize;
 public DWORD dwNumberOfItems;
 public WlanBssEntry[] wlanBssEntries;

 public static class ByReference extends WlanBssList implements Structure.ByReference
 
 public ByReference()
 

 

 public ByReference(Pointer p)
 
 super(p);
 
 

 public WlanBssList() 
 wlanBssEntries = new WlanBssEntry[1];
 

 public WlanBssList(Pointer p) 
 super(p);
 dwTotalSize = new DWORD(p.getInt(0));
 dwNumberOfItems = new DWORD(p.getInt(4));
 if(dwNumberOfItems.intValue() > 0) 
 wlanBssEntries = new WlanBssEntry[dwNumberOfItems.intValue()];
 readField("wlanBssEntries");
 else 
 wlanBssEntries = new WlanBssEntry[0];
 
 

 @Override
 protected List<String> getFieldOrder() 
 return Arrays.asList("dwTotalSize", "dwNumberOfItems", "wlanBssEntries");



And these are the nested structures:



package com.sevensignal.EyeQAgent.Util.win32.struct;

import com.sevensignal.EyeQAgent.Models.InformationElementGetter;
import com.sun.jna.Structure;
import com.sun.jna.platform.win32.WinDef.LONG;
import com.sun.jna.platform.win32.WinDef.ULONG;
import com.sun.jna.platform.win32.WinDef.ULONGLONG;
import com.sun.jna.platform.win32.WinDef.USHORT;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.NoArgsConstructor;

import java.util.Arrays;
import java.util.List;

@Builder
@NoArgsConstructor
@AllArgsConstructor
public class WlanBssEntry extends Structure implements InformationElementGetter 

 public DOT11_SSID dot11Ssid;
 public ULONG uPhyId;
 public DOT11_MAC_ADDRESS dot11Bssid;
 public int dot11BssType;
 public int dot11BssPhyType;
 public LONG lRssi;
 public ULONG uLinkQuality;
 public boolean bInRegDomain;
 public USHORT usBeaconPeriod;
 public ULONGLONG ullTimestamp;
 public ULONGLONG ullHostTimestamp;
 public USHORT usCapabilityInformation;
 public ULONG ulChCenterFrequency;
 public WlanRateSet wlanRateSet;
 public ULONG ulIeOffset;
 public ULONG ulIeSize;

 @Override
 protected List<String> getFieldOrder()
 
 return Arrays.asList("dot11Ssid",
 "uPhyId",
 "dot11Bssid",
 "dot11BssType",
 "dot11BssPhyType",
 "lRssi",
 "uLinkQuality",
 "bInRegDomain",
 "usBeaconPeriod",
 "ullTimestamp",
 "ullHostTimestamp",
 "usCapabilityInformation",
 "ulChCenterFrequency",
 "wlanRateSet",
 "ulIeOffset",
 "ulIeSize");
 

 public byte[] getInformationElement() 
 return this.getPointer()
 .getByteArray(this.ulIeOffset.intValue(), this.ulIeSize.intValue());
 



package com.sevensignal.EyeQAgent.Util.win32.struct;

import com.sun.jna.Structure;
import com.sun.jna.platform.win32.WinDef.*;

import java.util.Arrays;
import java.util.List;

public class DOT11_SSID extends Structure

 public static class ByReference extends DOT11_SSID implements Structure.ByReference
 

 

 public static int DOT11_SSID_MAX_LENGTH = 32;

 /**
 * The length, in bytes, of the ucSSID array.
 */
 public ULONG uSSIDLength;

 /**
 * The SSID. DOT11_SSID_MAX_LENGTH is set to 32.
 */
 public byte[] ucSSID;

 public DOT11_SSID()
 
 ucSSID = new byte[DOT11_SSID_MAX_LENGTH];
 

 @Override
 protected List<String> getFieldOrder()
 
 return Arrays.asList("uSSIDLength", "ucSSID");
 

 @Override
 public String toString() 
 if(uSSIDLength != null) 
 int ssidArrayLength = uSSIDLength.intValue();
 if (ssidArrayLength > DOT11_SSID_MAX_LENGTH) 
 ssidArrayLength = DOT11_SSID_MAX_LENGTH;
 

 return new String(Arrays.copyOfRange(ucSSID, 0, ssidArrayLength));
 else 
 return "";



The results of the unit test are:



java.lang.AssertionError: should init WLAN BSS Entry data struct 
Expected :50
Actual :0


The assertion that fails is:



assertEquals("should init WLAN BSS Entry data struct", new WinDef.LONG(50), subject.wlanBssEntries[0].uPhyId);






java windows junit jna







share|improve this question














The following unit test is intended to verify that a nested JNA data structure is properly parsed based on the data that gets passed into the constructor. The unit test properly checks when JNA initializes the 'parent' structure. However, the test fails when testing member variables of a nested structure. I suspect the problem to be that the unit test sets a pointer to a memory location that contains the data for the nested structure. Perhaps the Java Pointer isn't translating one-to-one to how C does it.



I tried placing the WlanBssEntry at the start of WlanBssEntry[] but that didn't provide any different results than how it is currently implemented. When I tried placing it contiguously, I did not call pointerToMem.setPointer(8, ...)



This is the unit test:



package com.sevensignal.EyeQAgent.Util.win32.struct;

import com.sevensignal.EyeQAgent.Models.Platform;
import com.sevensignal.EyeQAgent.Util.Utils;
import com.sun.jna.Memory;
import com.sun.jna.Pointer;
import com.sun.jna.platform.win32.WinDef;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

import static org.hamcrest.CoreMatchers.equalTo;
import static org.junit.Assert.*;
import static org.junit.Assume.assumeThat;

@RunWith(PowerMockRunner.class)
@PrepareForTest(Utils.class)
public class WlanBssListTest 

 Pointer pWlanBssList;

 private final static long OFFSET_TO_FIRST_WLAN_BSS_ENTRY = 1024;

 @Before
 public void setUp() 
 assumeThat(Utils.getPlatform(), equalTo(Platform.WINDOWS));
 pWlanBssList = allocateMemory(65536);
 initWlanBssEntryMemory(pWlanBssList, OFFSET_TO_FIRST_WLAN_BSS_ENTRY, 50);
 initWlanBssListMemory(pWlanBssList, 12, 1, OFFSET_TO_FIRST_WLAN_BSS_ENTRY);
 

 @Test
 public void shouldSetTotalSize() 
 WlanBssList subject = new WlanBssList(pWlanBssList);
 assertEquals("should set total size", new WinDef.DWORD(12), subject.dwTotalSize);
 

 @Test
 public void shouldSetNumberOfItems() 
 WlanBssList subject = new WlanBssList(pWlanBssList);
 assertEquals("should set number of items", new WinDef.DWORD(1), subject.dwNumberOfItems);
 

 @Test
 public void shouldInitWlanBssEntries() 
 WlanBssList subject = new WlanBssList(pWlanBssList);
 assertEquals("should init WLAN BSS Entries", 1, subject.wlanBssEntries.length);
 assertEquals("should init WLAN BSS Entry data struct", new WinDef.LONG(50), subject.wlanBssEntries[0].uPhyId);
 

 @Test
 public void shouldInitWlanBssEntriesWhenNoEntriesExist() 
 pWlanBssList.setInt(4, 0);
 WlanBssList subject = new WlanBssList(pWlanBssList);
 assertEquals("should init WLAN BSS Entries when no entries exist", 0, subject.wlanBssEntries.length);
 

 private Pointer allocateMemory(long size) 
 return new Memory(size).share(0);
 

 private void initWlanBssListMemory(Pointer pointerToMem, int dwTotalSize, int dwNumberOfItems, long offsetToWlanBssEntry) 
 pointerToMem.setInt(0, dwTotalSize);
 pointerToMem.setInt(4, dwNumberOfItems);
 pointerToMem.setPointer(8, pointerToMem.share(offsetToWlanBssEntry));
 

 private void initWlanBssEntryMemory(Pointer pointerToMem, long offsetToWlanBssEntry, long uPhyId) 
 final int PHY_ID_OFFSET = 40;
 pointerToMem.setLong(offsetToWlanBssEntry + 0, 3);
 pointerToMem.setByte(offsetToWlanBssEntry + 8, (byte)'T');
 pointerToMem.setByte(offsetToWlanBssEntry + 9, (byte)'S');
 pointerToMem.setByte(offsetToWlanBssEntry + 10, (byte)'T');
 pointerToMem.setLong(offsetToWlanBssEntry + PHY_ID_OFFSET, uPhyId);



This is the WlanBssList class which is the highest level structure:



package com.sevensignal.EyeQAgent.Util.win32.struct;

import com.sun.jna.Pointer;
import com.sun.jna.Structure;
import com.sun.jna.platform.win32.WinDef.DWORD;

import java.util.Arrays;
import java.util.List;

public class WlanBssList extends Structure 

 public DWORD dwTotalSize;
 public DWORD dwNumberOfItems;
 public WlanBssEntry[] wlanBssEntries;

 public static class ByReference extends WlanBssList implements Structure.ByReference
 
 public ByReference()
 

 

 public ByReference(Pointer p)
 
 super(p);
 
 

 public WlanBssList() 
 wlanBssEntries = new WlanBssEntry[1];
 

 public WlanBssList(Pointer p) 
 super(p);
 dwTotalSize = new DWORD(p.getInt(0));
 dwNumberOfItems = new DWORD(p.getInt(4));
 if(dwNumberOfItems.intValue() > 0) 
 wlanBssEntries = new WlanBssEntry[dwNumberOfItems.intValue()];
 readField("wlanBssEntries");
 else 
 wlanBssEntries = new WlanBssEntry[0];
 
 

 @Override
 protected List<String> getFieldOrder() 
 return Arrays.asList("dwTotalSize", "dwNumberOfItems", "wlanBssEntries");



And these are the nested structures:



package com.sevensignal.EyeQAgent.Util.win32.struct;

import com.sevensignal.EyeQAgent.Models.InformationElementGetter;
import com.sun.jna.Structure;
import com.sun.jna.platform.win32.WinDef.LONG;
import com.sun.jna.platform.win32.WinDef.ULONG;
import com.sun.jna.platform.win32.WinDef.ULONGLONG;
import com.sun.jna.platform.win32.WinDef.USHORT;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.NoArgsConstructor;

import java.util.Arrays;
import java.util.List;

@Builder
@NoArgsConstructor
@AllArgsConstructor
public class WlanBssEntry extends Structure implements InformationElementGetter 

 public DOT11_SSID dot11Ssid;
 public ULONG uPhyId;
 public DOT11_MAC_ADDRESS dot11Bssid;
 public int dot11BssType;
 public int dot11BssPhyType;
 public LONG lRssi;
 public ULONG uLinkQuality;
 public boolean bInRegDomain;
 public USHORT usBeaconPeriod;
 public ULONGLONG ullTimestamp;
 public ULONGLONG ullHostTimestamp;
 public USHORT usCapabilityInformation;
 public ULONG ulChCenterFrequency;
 public WlanRateSet wlanRateSet;
 public ULONG ulIeOffset;
 public ULONG ulIeSize;

 @Override
 protected List<String> getFieldOrder()
 
 return Arrays.asList("dot11Ssid",
 "uPhyId",
 "dot11Bssid",
 "dot11BssType",
 "dot11BssPhyType",
 "lRssi",
 "uLinkQuality",
 "bInRegDomain",
 "usBeaconPeriod",
 "ullTimestamp",
 "ullHostTimestamp",
 "usCapabilityInformation",
 "ulChCenterFrequency",
 "wlanRateSet",
 "ulIeOffset",
 "ulIeSize");
 

 public byte[] getInformationElement() 
 return this.getPointer()
 .getByteArray(this.ulIeOffset.intValue(), this.ulIeSize.intValue());
 



package com.sevensignal.EyeQAgent.Util.win32.struct;

import com.sun.jna.Structure;
import com.sun.jna.platform.win32.WinDef.*;

import java.util.Arrays;
import java.util.List;

public class DOT11_SSID extends Structure

 public static class ByReference extends DOT11_SSID implements Structure.ByReference
 

 

 public static int DOT11_SSID_MAX_LENGTH = 32;

 /**
 * The length, in bytes, of the ucSSID array.
 */
 public ULONG uSSIDLength;

 /**
 * The SSID. DOT11_SSID_MAX_LENGTH is set to 32.
 */
 public byte[] ucSSID;

 public DOT11_SSID()
 
 ucSSID = new byte[DOT11_SSID_MAX_LENGTH];
 

 @Override
 protected List<String> getFieldOrder()
 
 return Arrays.asList("uSSIDLength", "ucSSID");
 

 @Override
 public String toString() 
 if(uSSIDLength != null) 
 int ssidArrayLength = uSSIDLength.intValue();
 if (ssidArrayLength > DOT11_SSID_MAX_LENGTH) 
 ssidArrayLength = DOT11_SSID_MAX_LENGTH;
 

 return new String(Arrays.copyOfRange(ucSSID, 0, ssidArrayLength));
 else 
 return "";



The results of the unit test are:



java.lang.AssertionError: should init WLAN BSS Entry data struct 
Expected :50
Actual :0


The assertion that fails is:



assertEquals("should init WLAN BSS Entry data struct", new WinDef.LONG(50), subject.wlanBssEntries[0].uPhyId);






java windows junit jna




java windows junit jna






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked Mar 27 at 20:27









Aaron BaumanAaron Bauman

163 bronze badges




163 bronze badges










  • 1





    Welcome to Stack Overflow! I'm not sure but think your array initialization wlanBssEntries = new WlanBssEntry[dwNumberOfItems.intValue()]; won't work. You should do wlanBssEntries = (new WlanBssEntry()).toArray(dwNumberOfItems.intValue());. (Also JNA doesn't support 0 length arrays so the second part of your conditional is impossible: always initialize with at least 1 element.)

    – Daniel Widdis
    Mar 27 at 21:06






  • 1





    to be more clear, the new foo[] structure array only works on the Java side and does not initialize the structure object. You would have to initialize every individual foo in the array (non-contiguous native memory which wouldn't work well as an array parameter) or use toArray() to initialize the structures with contiguous native memory.

    – Daniel Widdis
    Mar 27 at 21:14






  • 1





    JNA iterates over the fields in your FieldOrder list, using reflection to get the mapped class so it knows their native size so it knows the offset. Are you sure your calculated offsets are correct?

    – Daniel Widdis
    Mar 28 at 15:39






  • 1





    I figured it out. I'll post my answer later but wanted to let you know so you don't spend your valuable time. In short, my problem was two fold. First, I did have an offset problem in the data that I was initializing. Second, I didn't place the data I was initializing at the "end" of the WlanBssList (starting at offset 8). Thank you for your help. Your mention of toArray helped and having another sounding board was all it took.

    – Aaron Bauman
    Mar 28 at 18:15






  • 1





    Glad you fixed it and that I could help!

    – Daniel Widdis
    Mar 28 at 18:33












  • 1





    Welcome to Stack Overflow! I'm not sure but think your array initialization wlanBssEntries = new WlanBssEntry[dwNumberOfItems.intValue()]; won't work. You should do wlanBssEntries = (new WlanBssEntry()).toArray(dwNumberOfItems.intValue());. (Also JNA doesn't support 0 length arrays so the second part of your conditional is impossible: always initialize with at least 1 element.)

    – Daniel Widdis
    Mar 27 at 21:06






  • 1





    to be more clear, the new foo[] structure array only works on the Java side and does not initialize the structure object. You would have to initialize every individual foo in the array (non-contiguous native memory which wouldn't work well as an array parameter) or use toArray() to initialize the structures with contiguous native memory.

    – Daniel Widdis
    Mar 27 at 21:14






  • 1





    JNA iterates over the fields in your FieldOrder list, using reflection to get the mapped class so it knows their native size so it knows the offset. Are you sure your calculated offsets are correct?

    – Daniel Widdis
    Mar 28 at 15:39






  • 1





    I figured it out. I'll post my answer later but wanted to let you know so you don't spend your valuable time. In short, my problem was two fold. First, I did have an offset problem in the data that I was initializing. Second, I didn't place the data I was initializing at the "end" of the WlanBssList (starting at offset 8). Thank you for your help. Your mention of toArray helped and having another sounding board was all it took.

    – Aaron Bauman
    Mar 28 at 18:15






  • 1





    Glad you fixed it and that I could help!

    – Daniel Widdis
    Mar 28 at 18:33







1




1





Welcome to Stack Overflow! I'm not sure but think your array initialization wlanBssEntries = new WlanBssEntry[dwNumberOfItems.intValue()]; won't work. You should do wlanBssEntries = (new WlanBssEntry()).toArray(dwNumberOfItems.intValue());. (Also JNA doesn't support 0 length arrays so the second part of your conditional is impossible: always initialize with at least 1 element.)

– Daniel Widdis
Mar 27 at 21:06





Welcome to Stack Overflow! I'm not sure but think your array initialization wlanBssEntries = new WlanBssEntry[dwNumberOfItems.intValue()]; won't work. You should do wlanBssEntries = (new WlanBssEntry()).toArray(dwNumberOfItems.intValue());. (Also JNA doesn't support 0 length arrays so the second part of your conditional is impossible: always initialize with at least 1 element.)

– Daniel Widdis
Mar 27 at 21:06




1




1





to be more clear, the new foo[] structure array only works on the Java side and does not initialize the structure object. You would have to initialize every individual foo in the array (non-contiguous native memory which wouldn't work well as an array parameter) or use toArray() to initialize the structures with contiguous native memory.

– Daniel Widdis
Mar 27 at 21:14





to be more clear, the new foo[] structure array only works on the Java side and does not initialize the structure object. You would have to initialize every individual foo in the array (non-contiguous native memory which wouldn't work well as an array parameter) or use toArray() to initialize the structures with contiguous native memory.

– Daniel Widdis
Mar 27 at 21:14




1




1





JNA iterates over the fields in your FieldOrder list, using reflection to get the mapped class so it knows their native size so it knows the offset. Are you sure your calculated offsets are correct?

– Daniel Widdis
Mar 28 at 15:39





JNA iterates over the fields in your FieldOrder list, using reflection to get the mapped class so it knows their native size so it knows the offset. Are you sure your calculated offsets are correct?

– Daniel Widdis
Mar 28 at 15:39




1




1





I figured it out. I'll post my answer later but wanted to let you know so you don't spend your valuable time. In short, my problem was two fold. First, I did have an offset problem in the data that I was initializing. Second, I didn't place the data I was initializing at the "end" of the WlanBssList (starting at offset 8). Thank you for your help. Your mention of toArray helped and having another sounding board was all it took.

– Aaron Bauman
Mar 28 at 18:15





I figured it out. I'll post my answer later but wanted to let you know so you don't spend your valuable time. In short, my problem was two fold. First, I did have an offset problem in the data that I was initializing. Second, I didn't place the data I was initializing at the "end" of the WlanBssList (starting at offset 8). Thank you for your help. Your mention of toArray helped and having another sounding board was all it took.

– Aaron Bauman
Mar 28 at 18:15




1




1





Glad you fixed it and that I could help!

– Daniel Widdis
Mar 28 at 18:33





Glad you fixed it and that I could help!

– Daniel Widdis
Mar 28 at 18:33












1 Answer
1






active

oldest

votes


















1















I fixed the failing unit test. There were 2 problems when the data was initialized in the allocated memory.



First of all, the offset into the uPhyId was off by 4 because I thought the length field of the dot11Ssid was 8 rather than 4.



Secondly, the memory for the first WlanBssEntry is located at an offset of 8 into the WlanBssList structure.



Lastly, I changed how wlanBssEntries gets initialized to guarantee that the array of WlanBssEntry instances appear contiguously in memory. My unit tests passed even without this change. But per @Daniel Widdis recommendations plus some online documentation I figured it's best to follow recommended procedures. It gets initialized as follows:



wlanBssEntries = (WlanBssEntry[])(new WlanBssEntry()).toArray(dwNumberOfItems.intValue());



Here is the code for the passing unit test:



package com.sevensignal.EyeQAgent.Util.win32.struct;

import com.sevensignal.EyeQAgent.Models.Platform;
import com.sevensignal.EyeQAgent.Util.Utils;
import com.sun.jna.Memory;
import com.sun.jna.Pointer;
import com.sun.jna.platform.win32.WinDef;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

import static org.hamcrest.CoreMatchers.equalTo;
import static org.junit.Assert.*;
import static org.junit.Assume.assumeThat;

@RunWith(PowerMockRunner.class)
@PrepareForTest(Utils.class)
public class WlanBssListTest 

 Pointer pWlanBssList;

 private final static long OFFSET_TO_FIRST_WLAN_BSS_ENTRY = 8;
 private final static int PHY_ID_OFFSET = 36;
 private final static int WLAN_BSS_ENTRY_LENGTH = 360;

 @Before
 public void setUp() 
 assumeThat(Utils.getPlatform(), equalTo(Platform.WINDOWS));
 pWlanBssList = allocateMemory(65536);
 

 @Test
 public void shouldSetTotalSize() 
 initWlanBssListMemory(pWlanBssList, 12, 1);
 WlanBssList subject = new WlanBssList(pWlanBssList);
 assertEquals("should set total size", new WinDef.DWORD(12), subject.dwTotalSize);
 

 @Test
 public void shouldSetNumberOfItems() 
 initWlanBssListMemory(pWlanBssList, 12, 1);
 WlanBssList subject = new WlanBssList(pWlanBssList);
 assertEquals("should set number of items", new WinDef.DWORD(1), subject.dwNumberOfItems);
 

 @Test
 public void shouldInitWlanBssEntries() 
 initWlanBssListMemory(pWlanBssList, 12, 1);
 WlanBssList subject = new WlanBssList(pWlanBssList);
 assertArrayEquals("should init SSID entry in WLAN BSS Entry data struct",
 new byte[]
 (byte)'I', (byte)'D', (byte)'1', (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
 (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
 (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
 (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00
 ,
 subject.wlanBssEntries[0].dot11Ssid.ucSSID);
 assertEquals("should init WLAN BSS Entry data struct", new WinDef.LONG(51), subject.wlanBssEntries[0].uPhyId);
 

 @Test
 public void shouldInitTwoWlanBssEntries() 
 initWlanBssListMemory(pWlanBssList, 12, 2);
 WlanBssList subject = new WlanBssList(pWlanBssList);
 assertArrayEquals("should init SSID entry in WLAN BSS Entry data struct",
 new byte[]
 (byte)'I', (byte)'D', (byte)'1', (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
 (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
 (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
 (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00
 ,
 subject.wlanBssEntries[0].dot11Ssid.ucSSID);
 assertEquals("should init WLAN BSS Entry data struct", new WinDef.LONG(51), subject.wlanBssEntries[0].uPhyId);

 assertArrayEquals("should init SSID entry in WLAN BSS Entry data struct",
 new byte[]
 (byte)'I', (byte)'D', (byte)'2', (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
 (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
 (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
 (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00
 ,
 subject.wlanBssEntries[1].dot11Ssid.ucSSID);
 assertEquals("should init WLAN BSS Entry data struct", new WinDef.LONG(0xC2), subject.wlanBssEntries[1].uPhyId);
 

 @Test
 public void shouldInitWlanBssEntriesWhenNoEntriesExist() 
 initWlanBssListMemory(pWlanBssList, 12, 0);
 WlanBssList subject = new WlanBssList(pWlanBssList);
 assertEquals("should init WLAN BSS Entries when no entries exist", 0, subject.wlanBssEntries.length);
 

 private Pointer allocateMemory(long size) 
 return new Memory(size).share(0);
 

 private void initWlanBssListMemory(Pointer pointerToMem, int dwTotalSize, int dwNumberOfItems) 
 pointerToMem.setInt(0, dwTotalSize);
 pointerToMem.setInt(4, dwNumberOfItems);
 initWlanBssEntryMemory(pointerToMem);
 

 private void initWlanBssEntryMemory(Pointer pointerToWlanBssEntryMem) 
 pointerToWlanBssEntryMem.setLong(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 0, 3);
 pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 4, (byte)'I');
 pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 5, (byte)'D');
 pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 6, (byte)'1');
 pointerToWlanBssEntryMem.setMemory(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 7, 29, (byte)0);
 pointerToWlanBssEntryMem.setLong(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + PHY_ID_OFFSET, 51);

 pointerToWlanBssEntryMem.setLong(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 0, 3);
 pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 4, (byte)'I');
 pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 5, (byte)'D');
 pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 6, (byte)'2');
 pointerToWlanBssEntryMem.setMemory(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 7, 29, (byte)0);
 pointerToWlanBssEntryMem.setLong(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + PHY_ID_OFFSET, 0xC2);






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    I fixed the failing unit test. There were 2 problems when the data was initialized in the allocated memory.



    First of all, the offset into the uPhyId was off by 4 because I thought the length field of the dot11Ssid was 8 rather than 4.



    Secondly, the memory for the first WlanBssEntry is located at an offset of 8 into the WlanBssList structure.



    Lastly, I changed how wlanBssEntries gets initialized to guarantee that the array of WlanBssEntry instances appear contiguously in memory. My unit tests passed even without this change. But per @Daniel Widdis recommendations plus some online documentation I figured it's best to follow recommended procedures. It gets initialized as follows:



    wlanBssEntries = (WlanBssEntry[])(new WlanBssEntry()).toArray(dwNumberOfItems.intValue());



    Here is the code for the passing unit test:



    package com.sevensignal.EyeQAgent.Util.win32.struct;

    import com.sevensignal.EyeQAgent.Models.Platform;
    import com.sevensignal.EyeQAgent.Util.Utils;
    import com.sun.jna.Memory;
    import com.sun.jna.Pointer;
    import com.sun.jna.platform.win32.WinDef;
    import org.junit.Before;
    import org.junit.Test;
    import org.junit.runner.RunWith;
    import org.powermock.core.classloader.annotations.PrepareForTest;
    import org.powermock.modules.junit4.PowerMockRunner;

    import static org.hamcrest.CoreMatchers.equalTo;
    import static org.junit.Assert.*;
    import static org.junit.Assume.assumeThat;

    @RunWith(PowerMockRunner.class)
    @PrepareForTest(Utils.class)
    public class WlanBssListTest 

     Pointer pWlanBssList;

     private final static long OFFSET_TO_FIRST_WLAN_BSS_ENTRY = 8;
     private final static int PHY_ID_OFFSET = 36;
     private final static int WLAN_BSS_ENTRY_LENGTH = 360;

     @Before
     public void setUp() 
     assumeThat(Utils.getPlatform(), equalTo(Platform.WINDOWS));
     pWlanBssList = allocateMemory(65536);
     

     @Test
     public void shouldSetTotalSize() 
     initWlanBssListMemory(pWlanBssList, 12, 1);
     WlanBssList subject = new WlanBssList(pWlanBssList);
     assertEquals("should set total size", new WinDef.DWORD(12), subject.dwTotalSize);
     

     @Test
     public void shouldSetNumberOfItems() 
     initWlanBssListMemory(pWlanBssList, 12, 1);
     WlanBssList subject = new WlanBssList(pWlanBssList);
     assertEquals("should set number of items", new WinDef.DWORD(1), subject.dwNumberOfItems);
     

     @Test
     public void shouldInitWlanBssEntries() 
     initWlanBssListMemory(pWlanBssList, 12, 1);
     WlanBssList subject = new WlanBssList(pWlanBssList);
     assertArrayEquals("should init SSID entry in WLAN BSS Entry data struct",
     new byte[]
     (byte)'I', (byte)'D', (byte)'1', (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
     (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
     (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
     (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00
     ,
     subject.wlanBssEntries[0].dot11Ssid.ucSSID);
     assertEquals("should init WLAN BSS Entry data struct", new WinDef.LONG(51), subject.wlanBssEntries[0].uPhyId);
     

     @Test
     public void shouldInitTwoWlanBssEntries() 
     initWlanBssListMemory(pWlanBssList, 12, 2);
     WlanBssList subject = new WlanBssList(pWlanBssList);
     assertArrayEquals("should init SSID entry in WLAN BSS Entry data struct",
     new byte[]
     (byte)'I', (byte)'D', (byte)'1', (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
     (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
     (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
     (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00
     ,
     subject.wlanBssEntries[0].dot11Ssid.ucSSID);
     assertEquals("should init WLAN BSS Entry data struct", new WinDef.LONG(51), subject.wlanBssEntries[0].uPhyId);

     assertArrayEquals("should init SSID entry in WLAN BSS Entry data struct",
     new byte[]
     (byte)'I', (byte)'D', (byte)'2', (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
     (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
     (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
     (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00
     ,
     subject.wlanBssEntries[1].dot11Ssid.ucSSID);
     assertEquals("should init WLAN BSS Entry data struct", new WinDef.LONG(0xC2), subject.wlanBssEntries[1].uPhyId);
     

     @Test
     public void shouldInitWlanBssEntriesWhenNoEntriesExist() 
     initWlanBssListMemory(pWlanBssList, 12, 0);
     WlanBssList subject = new WlanBssList(pWlanBssList);
     assertEquals("should init WLAN BSS Entries when no entries exist", 0, subject.wlanBssEntries.length);
     

     private Pointer allocateMemory(long size) 
     return new Memory(size).share(0);
     

     private void initWlanBssListMemory(Pointer pointerToMem, int dwTotalSize, int dwNumberOfItems) 
     pointerToMem.setInt(0, dwTotalSize);
     pointerToMem.setInt(4, dwNumberOfItems);
     initWlanBssEntryMemory(pointerToMem);
     

     private void initWlanBssEntryMemory(Pointer pointerToWlanBssEntryMem) 
     pointerToWlanBssEntryMem.setLong(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 0, 3);
     pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 4, (byte)'I');
     pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 5, (byte)'D');
     pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 6, (byte)'1');
     pointerToWlanBssEntryMem.setMemory(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 7, 29, (byte)0);
     pointerToWlanBssEntryMem.setLong(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + PHY_ID_OFFSET, 51);

     pointerToWlanBssEntryMem.setLong(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 0, 3);
     pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 4, (byte)'I');
     pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 5, (byte)'D');
     pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 6, (byte)'2');
     pointerToWlanBssEntryMem.setMemory(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 7, 29, (byte)0);
     pointerToWlanBssEntryMem.setLong(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + PHY_ID_OFFSET, 0xC2);






    share|improve this answer





























      1















      I fixed the failing unit test. There were 2 problems when the data was initialized in the allocated memory.



      First of all, the offset into the uPhyId was off by 4 because I thought the length field of the dot11Ssid was 8 rather than 4.



      Secondly, the memory for the first WlanBssEntry is located at an offset of 8 into the WlanBssList structure.



      Lastly, I changed how wlanBssEntries gets initialized to guarantee that the array of WlanBssEntry instances appear contiguously in memory. My unit tests passed even without this change. But per @Daniel Widdis recommendations plus some online documentation I figured it's best to follow recommended procedures. It gets initialized as follows:



      wlanBssEntries = (WlanBssEntry[])(new WlanBssEntry()).toArray(dwNumberOfItems.intValue());



      Here is the code for the passing unit test:



      package com.sevensignal.EyeQAgent.Util.win32.struct;

      import com.sevensignal.EyeQAgent.Models.Platform;
      import com.sevensignal.EyeQAgent.Util.Utils;
      import com.sun.jna.Memory;
      import com.sun.jna.Pointer;
      import com.sun.jna.platform.win32.WinDef;
      import org.junit.Before;
      import org.junit.Test;
      import org.junit.runner.RunWith;
      import org.powermock.core.classloader.annotations.PrepareForTest;
      import org.powermock.modules.junit4.PowerMockRunner;

      import static org.hamcrest.CoreMatchers.equalTo;
      import static org.junit.Assert.*;
      import static org.junit.Assume.assumeThat;

      @RunWith(PowerMockRunner.class)
      @PrepareForTest(Utils.class)
      public class WlanBssListTest 

       Pointer pWlanBssList;

       private final static long OFFSET_TO_FIRST_WLAN_BSS_ENTRY = 8;
       private final static int PHY_ID_OFFSET = 36;
       private final static int WLAN_BSS_ENTRY_LENGTH = 360;

       @Before
       public void setUp() 
       assumeThat(Utils.getPlatform(), equalTo(Platform.WINDOWS));
       pWlanBssList = allocateMemory(65536);
       

       @Test
       public void shouldSetTotalSize() 
       initWlanBssListMemory(pWlanBssList, 12, 1);
       WlanBssList subject = new WlanBssList(pWlanBssList);
       assertEquals("should set total size", new WinDef.DWORD(12), subject.dwTotalSize);
       

       @Test
       public void shouldSetNumberOfItems() 
       initWlanBssListMemory(pWlanBssList, 12, 1);
       WlanBssList subject = new WlanBssList(pWlanBssList);
       assertEquals("should set number of items", new WinDef.DWORD(1), subject.dwNumberOfItems);
       

       @Test
       public void shouldInitWlanBssEntries() 
       initWlanBssListMemory(pWlanBssList, 12, 1);
       WlanBssList subject = new WlanBssList(pWlanBssList);
       assertArrayEquals("should init SSID entry in WLAN BSS Entry data struct",
       new byte[]
       (byte)'I', (byte)'D', (byte)'1', (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
       (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
       (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
       (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00
       ,
       subject.wlanBssEntries[0].dot11Ssid.ucSSID);
       assertEquals("should init WLAN BSS Entry data struct", new WinDef.LONG(51), subject.wlanBssEntries[0].uPhyId);
       

       @Test
       public void shouldInitTwoWlanBssEntries() 
       initWlanBssListMemory(pWlanBssList, 12, 2);
       WlanBssList subject = new WlanBssList(pWlanBssList);
       assertArrayEquals("should init SSID entry in WLAN BSS Entry data struct",
       new byte[]
       (byte)'I', (byte)'D', (byte)'1', (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
       (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
       (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
       (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00
       ,
       subject.wlanBssEntries[0].dot11Ssid.ucSSID);
       assertEquals("should init WLAN BSS Entry data struct", new WinDef.LONG(51), subject.wlanBssEntries[0].uPhyId);

       assertArrayEquals("should init SSID entry in WLAN BSS Entry data struct",
       new byte[]
       (byte)'I', (byte)'D', (byte)'2', (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
       (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
       (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
       (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00
       ,
       subject.wlanBssEntries[1].dot11Ssid.ucSSID);
       assertEquals("should init WLAN BSS Entry data struct", new WinDef.LONG(0xC2), subject.wlanBssEntries[1].uPhyId);
       

       @Test
       public void shouldInitWlanBssEntriesWhenNoEntriesExist() 
       initWlanBssListMemory(pWlanBssList, 12, 0);
       WlanBssList subject = new WlanBssList(pWlanBssList);
       assertEquals("should init WLAN BSS Entries when no entries exist", 0, subject.wlanBssEntries.length);
       

       private Pointer allocateMemory(long size) 
       return new Memory(size).share(0);
       

       private void initWlanBssListMemory(Pointer pointerToMem, int dwTotalSize, int dwNumberOfItems) 
       pointerToMem.setInt(0, dwTotalSize);
       pointerToMem.setInt(4, dwNumberOfItems);
       initWlanBssEntryMemory(pointerToMem);
       

       private void initWlanBssEntryMemory(Pointer pointerToWlanBssEntryMem) 
       pointerToWlanBssEntryMem.setLong(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 0, 3);
       pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 4, (byte)'I');
       pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 5, (byte)'D');
       pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 6, (byte)'1');
       pointerToWlanBssEntryMem.setMemory(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 7, 29, (byte)0);
       pointerToWlanBssEntryMem.setLong(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + PHY_ID_OFFSET, 51);

       pointerToWlanBssEntryMem.setLong(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 0, 3);
       pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 4, (byte)'I');
       pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 5, (byte)'D');
       pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 6, (byte)'2');
       pointerToWlanBssEntryMem.setMemory(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 7, 29, (byte)0);
       pointerToWlanBssEntryMem.setLong(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + PHY_ID_OFFSET, 0xC2);






      share|improve this answer



























        1














        1










        1









        I fixed the failing unit test. There were 2 problems when the data was initialized in the allocated memory.



        First of all, the offset into the uPhyId was off by 4 because I thought the length field of the dot11Ssid was 8 rather than 4.



        Secondly, the memory for the first WlanBssEntry is located at an offset of 8 into the WlanBssList structure.



        Lastly, I changed how wlanBssEntries gets initialized to guarantee that the array of WlanBssEntry instances appear contiguously in memory. My unit tests passed even without this change. But per @Daniel Widdis recommendations plus some online documentation I figured it's best to follow recommended procedures. It gets initialized as follows:



        wlanBssEntries = (WlanBssEntry[])(new WlanBssEntry()).toArray(dwNumberOfItems.intValue());



        Here is the code for the passing unit test:



        package com.sevensignal.EyeQAgent.Util.win32.struct;

        import com.sevensignal.EyeQAgent.Models.Platform;
        import com.sevensignal.EyeQAgent.Util.Utils;
        import com.sun.jna.Memory;
        import com.sun.jna.Pointer;
        import com.sun.jna.platform.win32.WinDef;
        import org.junit.Before;
        import org.junit.Test;
        import org.junit.runner.RunWith;
        import org.powermock.core.classloader.annotations.PrepareForTest;
        import org.powermock.modules.junit4.PowerMockRunner;

        import static org.hamcrest.CoreMatchers.equalTo;
        import static org.junit.Assert.*;
        import static org.junit.Assume.assumeThat;

        @RunWith(PowerMockRunner.class)
        @PrepareForTest(Utils.class)
        public class WlanBssListTest 

         Pointer pWlanBssList;

         private final static long OFFSET_TO_FIRST_WLAN_BSS_ENTRY = 8;
         private final static int PHY_ID_OFFSET = 36;
         private final static int WLAN_BSS_ENTRY_LENGTH = 360;

         @Before
         public void setUp() 
         assumeThat(Utils.getPlatform(), equalTo(Platform.WINDOWS));
         pWlanBssList = allocateMemory(65536);
         

         @Test
         public void shouldSetTotalSize() 
         initWlanBssListMemory(pWlanBssList, 12, 1);
         WlanBssList subject = new WlanBssList(pWlanBssList);
         assertEquals("should set total size", new WinDef.DWORD(12), subject.dwTotalSize);
         

         @Test
         public void shouldSetNumberOfItems() 
         initWlanBssListMemory(pWlanBssList, 12, 1);
         WlanBssList subject = new WlanBssList(pWlanBssList);
         assertEquals("should set number of items", new WinDef.DWORD(1), subject.dwNumberOfItems);
         

         @Test
         public void shouldInitWlanBssEntries() 
         initWlanBssListMemory(pWlanBssList, 12, 1);
         WlanBssList subject = new WlanBssList(pWlanBssList);
         assertArrayEquals("should init SSID entry in WLAN BSS Entry data struct",
         new byte[]
         (byte)'I', (byte)'D', (byte)'1', (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
         (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
         (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
         (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00
         ,
         subject.wlanBssEntries[0].dot11Ssid.ucSSID);
         assertEquals("should init WLAN BSS Entry data struct", new WinDef.LONG(51), subject.wlanBssEntries[0].uPhyId);
         

         @Test
         public void shouldInitTwoWlanBssEntries() 
         initWlanBssListMemory(pWlanBssList, 12, 2);
         WlanBssList subject = new WlanBssList(pWlanBssList);
         assertArrayEquals("should init SSID entry in WLAN BSS Entry data struct",
         new byte[]
         (byte)'I', (byte)'D', (byte)'1', (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
         (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
         (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
         (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00
         ,
         subject.wlanBssEntries[0].dot11Ssid.ucSSID);
         assertEquals("should init WLAN BSS Entry data struct", new WinDef.LONG(51), subject.wlanBssEntries[0].uPhyId);

         assertArrayEquals("should init SSID entry in WLAN BSS Entry data struct",
         new byte[]
         (byte)'I', (byte)'D', (byte)'2', (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
         (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
         (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
         (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00
         ,
         subject.wlanBssEntries[1].dot11Ssid.ucSSID);
         assertEquals("should init WLAN BSS Entry data struct", new WinDef.LONG(0xC2), subject.wlanBssEntries[1].uPhyId);
         

         @Test
         public void shouldInitWlanBssEntriesWhenNoEntriesExist() 
         initWlanBssListMemory(pWlanBssList, 12, 0);
         WlanBssList subject = new WlanBssList(pWlanBssList);
         assertEquals("should init WLAN BSS Entries when no entries exist", 0, subject.wlanBssEntries.length);
         

         private Pointer allocateMemory(long size) 
         return new Memory(size).share(0);
         

         private void initWlanBssListMemory(Pointer pointerToMem, int dwTotalSize, int dwNumberOfItems) 
         pointerToMem.setInt(0, dwTotalSize);
         pointerToMem.setInt(4, dwNumberOfItems);
         initWlanBssEntryMemory(pointerToMem);
         

         private void initWlanBssEntryMemory(Pointer pointerToWlanBssEntryMem) 
         pointerToWlanBssEntryMem.setLong(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 0, 3);
         pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 4, (byte)'I');
         pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 5, (byte)'D');
         pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 6, (byte)'1');
         pointerToWlanBssEntryMem.setMemory(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 7, 29, (byte)0);
         pointerToWlanBssEntryMem.setLong(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + PHY_ID_OFFSET, 51);

         pointerToWlanBssEntryMem.setLong(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 0, 3);
         pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 4, (byte)'I');
         pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 5, (byte)'D');
         pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 6, (byte)'2');
         pointerToWlanBssEntryMem.setMemory(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 7, 29, (byte)0);
         pointerToWlanBssEntryMem.setLong(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + PHY_ID_OFFSET, 0xC2);






        share|improve this answer













        I fixed the failing unit test. There were 2 problems when the data was initialized in the allocated memory.



        First of all, the offset into the uPhyId was off by 4 because I thought the length field of the dot11Ssid was 8 rather than 4.



        Secondly, the memory for the first WlanBssEntry is located at an offset of 8 into the WlanBssList structure.



        Lastly, I changed how wlanBssEntries gets initialized to guarantee that the array of WlanBssEntry instances appear contiguously in memory. My unit tests passed even without this change. But per @Daniel Widdis recommendations plus some online documentation I figured it's best to follow recommended procedures. It gets initialized as follows:



        wlanBssEntries = (WlanBssEntry[])(new WlanBssEntry()).toArray(dwNumberOfItems.intValue());



        Here is the code for the passing unit test:



        package com.sevensignal.EyeQAgent.Util.win32.struct;

        import com.sevensignal.EyeQAgent.Models.Platform;
        import com.sevensignal.EyeQAgent.Util.Utils;
        import com.sun.jna.Memory;
        import com.sun.jna.Pointer;
        import com.sun.jna.platform.win32.WinDef;
        import org.junit.Before;
        import org.junit.Test;
        import org.junit.runner.RunWith;
        import org.powermock.core.classloader.annotations.PrepareForTest;
        import org.powermock.modules.junit4.PowerMockRunner;

        import static org.hamcrest.CoreMatchers.equalTo;
        import static org.junit.Assert.*;
        import static org.junit.Assume.assumeThat;

        @RunWith(PowerMockRunner.class)
        @PrepareForTest(Utils.class)
        public class WlanBssListTest 

         Pointer pWlanBssList;

         private final static long OFFSET_TO_FIRST_WLAN_BSS_ENTRY = 8;
         private final static int PHY_ID_OFFSET = 36;
         private final static int WLAN_BSS_ENTRY_LENGTH = 360;

         @Before
         public void setUp() 
         assumeThat(Utils.getPlatform(), equalTo(Platform.WINDOWS));
         pWlanBssList = allocateMemory(65536);
         

         @Test
         public void shouldSetTotalSize() 
         initWlanBssListMemory(pWlanBssList, 12, 1);
         WlanBssList subject = new WlanBssList(pWlanBssList);
         assertEquals("should set total size", new WinDef.DWORD(12), subject.dwTotalSize);
         

         @Test
         public void shouldSetNumberOfItems() 
         initWlanBssListMemory(pWlanBssList, 12, 1);
         WlanBssList subject = new WlanBssList(pWlanBssList);
         assertEquals("should set number of items", new WinDef.DWORD(1), subject.dwNumberOfItems);
         

         @Test
         public void shouldInitWlanBssEntries() 
         initWlanBssListMemory(pWlanBssList, 12, 1);
         WlanBssList subject = new WlanBssList(pWlanBssList);
         assertArrayEquals("should init SSID entry in WLAN BSS Entry data struct",
         new byte[]
         (byte)'I', (byte)'D', (byte)'1', (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
         (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
         (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
         (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00
         ,
         subject.wlanBssEntries[0].dot11Ssid.ucSSID);
         assertEquals("should init WLAN BSS Entry data struct", new WinDef.LONG(51), subject.wlanBssEntries[0].uPhyId);
         

         @Test
         public void shouldInitTwoWlanBssEntries() 
         initWlanBssListMemory(pWlanBssList, 12, 2);
         WlanBssList subject = new WlanBssList(pWlanBssList);
         assertArrayEquals("should init SSID entry in WLAN BSS Entry data struct",
         new byte[]
         (byte)'I', (byte)'D', (byte)'1', (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
         (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
         (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
         (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00
         ,
         subject.wlanBssEntries[0].dot11Ssid.ucSSID);
         assertEquals("should init WLAN BSS Entry data struct", new WinDef.LONG(51), subject.wlanBssEntries[0].uPhyId);

         assertArrayEquals("should init SSID entry in WLAN BSS Entry data struct",
         new byte[]
         (byte)'I', (byte)'D', (byte)'2', (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
         (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
         (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
         (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00
         ,
         subject.wlanBssEntries[1].dot11Ssid.ucSSID);
         assertEquals("should init WLAN BSS Entry data struct", new WinDef.LONG(0xC2), subject.wlanBssEntries[1].uPhyId);
         

         @Test
         public void shouldInitWlanBssEntriesWhenNoEntriesExist() 
         initWlanBssListMemory(pWlanBssList, 12, 0);
         WlanBssList subject = new WlanBssList(pWlanBssList);
         assertEquals("should init WLAN BSS Entries when no entries exist", 0, subject.wlanBssEntries.length);
         

         private Pointer allocateMemory(long size) 
         return new Memory(size).share(0);
         

         private void initWlanBssListMemory(Pointer pointerToMem, int dwTotalSize, int dwNumberOfItems) 
         pointerToMem.setInt(0, dwTotalSize);
         pointerToMem.setInt(4, dwNumberOfItems);
         initWlanBssEntryMemory(pointerToMem);
         

         private void initWlanBssEntryMemory(Pointer pointerToWlanBssEntryMem) 
         pointerToWlanBssEntryMem.setLong(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 0, 3);
         pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 4, (byte)'I');
         pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 5, (byte)'D');
         pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 6, (byte)'1');
         pointerToWlanBssEntryMem.setMemory(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + 7, 29, (byte)0);
         pointerToWlanBssEntryMem.setLong(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + PHY_ID_OFFSET, 51);

         pointerToWlanBssEntryMem.setLong(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 0, 3);
         pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 4, (byte)'I');
         pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 5, (byte)'D');
         pointerToWlanBssEntryMem.setByte(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 6, (byte)'2');
         pointerToWlanBssEntryMem.setMemory(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + 7, 29, (byte)0);
         pointerToWlanBssEntryMem.setLong(OFFSET_TO_FIRST_WLAN_BSS_ENTRY + WLAN_BSS_ENTRY_LENGTH + PHY_ID_OFFSET, 0xC2);







        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered Mar 28 at 20:48









        Aaron BaumanAaron Bauman

        163 bronze badges




        163 bronze badges





















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