I am using JNA to access a custom DLL which seems to be using the FAR PASCAL Calling Conventions, but the JVM crashes every time i try to access it.
Development Guide of the dll says:
BOOL FAR PASCAL GetIomemVersion(LPSTR);
And Dependency Walker tells me:
_GetIomemVersion#4
public class PebblePrinter {
public interface Iomem extends StdCallLibrary {
boolean _GetIomemVersion(String version);
}
String version;
Iomem INSTANCE;
StdCallFunctionMapper myMapper;
public PebblePrinter() {
HashMap optionMap = new HashMap();
myMapper = new StdCallFunctionMapper();
optionMap.put(Library.OPTION_FUNCTION_MAPPER, myMapper);
INSTANCE = (Iomem)Native.loadLibrary("iomem", Iomem.class,optionMap);
}
public String getIomemVersion(){
INSTANCE._GetIomemVersion(version);
return version;
}
}
With C# code it works well using
[DllImport("iomem.dll", EntryPoint = "_GetIomemVersion#4")]
public static extern bool GetIomemVersion(IntPtr version);
Can you tell me what i am doing wrong?
Thanks in advance!!!
Problem solved,
I've just used the wrong parameter ..
GetIomemVersion needs a Pointer
boolean _GetIomemVersion(Pointer version);
public String getIomemVersion(){
Memory m = new Memory(1024);
Pointer x = m.getPointer(0);
INSTANCE._GetIomemVersion(x);
return x.getString(0);
}
Related
In Objects in Kotlin: Create safe singletons in one line of code (KAD 27) Antonio Leiva states:
In fact, an object is just a data type with a single implementation.
I would expect to see the term instance rather than implementation used here. Is there some nuance that I am missing?
Sure it does have a single instance after all, but I believe what they meant to say is that whatever you write in an object is final and you can not override it. Even if you make it open(for argument purpose), you can not make an anonymous object out of it since the anonymous class can't be used on a SingleTon instance.
So " data type with a single implementation" means, whatever you write is the final implementation. An instance is, after all, a result of some implementation.
For reference, I am adding a decompiled code of object declaration.
public final class Test {
#NotNull
private static final String testMember = "Test";
public static final Test INSTANCE;
#NotNull
public final String getTestMember() {
return testMember;
}
private Test() {
}
static {
Test var0 = new Test();
INSTANCE = var0;
testMember = "Test";
}
}
I have something like this
class Unilevel {
public $contador = 2;
public static function listarLevels($user_id){
if($contador <= 5){
echo '<h1>Nivel '.$contador.'</h1>';
$user = DB::table('matrices')->where('id_user', $user_id)->first();
$actual_user = DB::table('users')->where('id', $user->id_user)->first();
echo $actual_user->username.'<br>';
}
$contador++;
}
}
The function is not working but if i put the variable $contador inside listarLevels works
which is the problem? Thanks
This is how classes work in PHP.
To call $contador within the function when you've declared it as a class property, you use $this->contador
It may be helpful to read the manual on object oriented programming in PHP to get more familiar with it before diving into Laravel. http://php.net/manual/en/language.oop5.php
You can't access your class non static properties in static methods.
Try this.
class Unilevel {
public static $contador = 2;
public static function listarLevels($user_id){
//self::$contador = 4;
}
}
If your method is static you need make your property static too. Their are few other ways too like instantiating the object of the class. Read more about static in PHP.
I encounter what I believe to be a bug and I was just wondering if this is already known as a issue or if this is not a issue and why.
The problem related to Read Only Properties on a Type when compiling with the VB.Net Compiler in Visual Studio 2008.
Follows are the class definitions and a small C# program which will not compile. (And is correct in not compiling IMHO because the property being set in the Delegate is Read-only)
public interface ITest
{
bool PrivateBool { get; }
}
public class TestClass : ITest
{
bool privateBool = false;
public bool PrivateBool
{
get
{
return privateBool;
}
}
bool publicBool = false;
public bool PublicBool
{
get { return publicBool; }
set { publicBool = value; }
}
}
class Program
{
static void Main(string[] args)
{
TestClass tc = new TestClass();
//Compile Error
//tc.PrivateBool = false;
//Compile Error
//Action act = new Action(delegate()
//{
// tc.PrivateBool = false;
//});
//Action<TestClass> test = new Action<TestClass>(delegate(TestClass tcc)
//{
// tcc.PrivateBool = false;
//});
//Compile Time Error
//Action<TestClass> test = new Action<TestClass>( tz=> tz.PrivateBool = false);
//Compile Time Error
//Action test = new Action(tc.PrivateBool = false);
}
}
In VB.Net However this is a larger issue… the program will compile and execute with no exception. But the property is not set.
This was a nightmare to catch in the debugger at Run time and we feel that the compiler should have caught that we are assigning to a ready only property just as the CSharp compiler alerts you when compiling.
Module Module1
Sub Main()
Dim tc As New TestClass()
Dim setP = New Action(Of TestClass)(Function(d As TestClass) _
d.PrivateBool = False _
)
setP.Invoke(tc)
End Sub
End Module
Can anyone explain if this is correct logic and why?
I assume that someone will respond that the job of the compiler was fulfilled by examining the parameter type to the delegate and that the delegate was typed to accept that parameter just as it should when parsing a Method Body or a Function Body.
My rebuttal to this would be that the compiler DOES throw an error when that property is attempted to be set from within a method but not the delegate. Delegates should be parsed the same as a Method.
Is the C# compiler over extending itself? I think not. My experience is that this is a bug in the vb.net compiler and should be fixed by a patch to the IDE.
Last but surely not least what occurs when the Invoke happens?
The delegate surely does not use reflection to set the property automagically so I assume the CLR sees the read-only qualifier and a NOOP gets executed. Is that actually what occurs or is the behavior undefined?
Thank you for your time!
In VB.NET 2008, there are no statement lambdas. All lambdas are functions. They return a value, not perform an action.
Your VB lambda simply compares d.PrivateBool and False and returns the result of the comparison.
This is not a bug and by design. It is therefore advisable to avoid assigning VB.NET 2008's lambdas to an Action, this is highly confusing for an unprepared person.
Statement lambdas appeared in VB.NET 2010.
I am attempting to simply add a FilterInfo class to my FilterInfo collection. I'm having a terrible time trying to understand why the following code keeps throwing the error:
System::Collections::Generic::List::Add'
: cannot convert parameter 1 from
'Ziz::FilterInfo *' to
'Ziz::FilterInfo'
I'm only learning C++/CLI, as I'm a C# developer, and I'm sure it's something simple, but I sure could use some pointers. My stripped code is as follows:
public value class FilterInfo
{
public:
char* Address;
};
public ref class Ziz
{
private:
List<FilterInfo>^ _blockList;
public:
// Constructor
Ziz(){
_blockList = gcnew List<FilterInfo>();
}
List<FilterInfo>^ GetBlockList()
{
for each(_IPFILTERINFO ip in _packetFilter->GetBlockList())
{
// _IPFILTERINFO is the native C++ struct.
FilterInfo* f = new FilterInfo();
_blockList->Add(f);
}
return _blockList;
}
You declared _blockList as
List<FilterInfo>^ _blockList;
but you are trying to add
FilterInfo* f
to it. It cannot work since one is a pointer and the other one is a reference.
I'm not sure how "value" fits in but in
public value class FilterInfo
{
public:
char* Address;
};
You are derefore declaring an unmanaged class
to make it managed, you should use
public ref class FiterInfo
This will allow you to use FilterInfo* without having to manage memory explicitely.
Finally, char* is not so great in C++/CLI, I would recommend using System::String
_blockList->Add(*f);
You have to construct your FilterInfo with gcnew as well. You can't really mix and mash these together without marshaling.
FilterInfo is not FilterInfo*. If you want a List of pointers to FilterInfo, you need to say that List<FilterInfo*>. Since FilterInfo is a value class here though you'll likely just want to skip the new.
FilterInfo fi;
_blockList->Add(fi);
public ref class A
{
};
int main(array<System::String ^> ^args)
{
Console::WriteLine(L"Hello World");
ICollection<A^>^ oCollection = gcnew List<A^>();
oCollection->Add(gcnew A());
return 0;
}
Given the new dynamic support in C# 4, is it possible to write a class in such a way that if a method is invoked on an instance and that method is not present, dispatch is passed to another method? This might look something like:
public class Apple : ... {
// ...
private ... MethodMissing(string name, ...) {
if (name == "TurnIntoOrange") {
// do something
}
}
}
dynamic d = new Apple();
d.TurnIntoOrange(); // Not actually defined on Apple; will pass to MethodMissing.
Other languages would call this "method_missing support", under the more general heading of metaprogramming. I'm not sure what C# calls this specifically. But is it possible?
Absolutely. Either implement IDynamicMetaObjectProvider or derive from DynamicObject for a much simpler route. See the DLR documentation for some good examples.
Here's a quick example of DynamicObject:
using System;
using System.Dynamic;
public class MyDynamic : DynamicObject
{
public override bool TryInvokeMember
(InvokeMemberBinder binder,
object[] args,
out object result)
{
Console.WriteLine("I would have invoked: {0}",
binder.Name);
result = "dummy";
return true;
}
public string NormalMethod()
{
Console.WriteLine("In NormalMethod");
return "normal";
}
}
class Test
{
static void Main()
{
dynamic d = new MyDynamic();
Console.WriteLine(d.HelloWorld());
Console.WriteLine(d.NormalMethod());
}
}
<plug>
I have a bigger example of DynamicObject in the 2nd edition of C# in Depth but I haven't yet implemented IDyamicMetaObjectProvider. I'll do so before the book's release, but the early access edition only has the DynamicObject example at the moment. Btw, if you buy it today it's half price - use the code twtr0711. I'll edit this answer later on to remove that bit :)
</plug>