Menggunakan Java Native Access (JNA) untuk memanggil MacOS API

pengenalan

Berikut ialah contoh mudah tentang cara menggunakan JNA dengan API MacOS. Saya tidak akan menerangkan perkara ini, kerana saya masih belajar, tetapi saya mengekalkan kod minimum untuk memudahkan pemahaman dan mendapatkan idea asas tentang cara melakukannya untuk tujuan lain.

Kebanyakan kod adalah daripada Intellij-Community (Lesen Apache).

Kebergantungan

Apa yang kita perlukan hanyalah jna-platform.

<dependency>
  <groupId>net.java.dev.jna</groupId>
  <artifactId>jna-platform</artifactId>
  <version>5.13.0</version>
</dependency>

Kod

Terdapat 4 fail kod sumber. ID disalin daripada IntelliJ tanpa pengubahsuaian. MyFoundation dan MyFoundationLibrary masing-masing dipangkas daripada Foundation dan FoundationLibrary.

Application.java

package org.example;

import com.sun.jna.Pointer;

import static org.example.MyFoundation.*;

public class Application {

    public static void main(String[] args) throws Exception {
        ID processInfoCls = getObjcClass("NSProcessInfo");
        Pointer processInfoSel = createSelector("processInfo");
        Pointer processNameSel = createSelector("processName");

        ID processInfo = invoke(processInfoCls, processInfoSel);
        ID processNameNSString = invoke(processInfo, processNameSel);
        String processName = toStringViaUTF8(processNameNSString);
        System.out.println(processName);
    }

}

ID.java

package org.example;

import com.sun.jna.NativeLong;

public final class ID extends NativeLong {

    public ID() {
    }

    public ID(long peer) {
        super(peer);
    }

    public static final ID NIL = new ID(0L);

    public boolean booleanValue() {
        return intValue() != 0;
    }
}

MyFoundationLibrary.java

public interface MyFoundationLibrary extends Library {

    int kCFStringEncodingUTF8 = 0x08000100;

    ID objc_getClass(String className);

    Pointer sel_registerName(String selectorName);

    int CFStringGetLength(ID theString);

    byte CFStringGetCString(ID theString, byte[] buffer, int bufferSize, int encoding);

}

MyFoundation.java

package org.example;

import com.sun.jna.*;

import java.lang.reflect.Proxy;
import java.util.Collections;

public class MyFoundation {
    private static final MyFoundationLibrary myFoundationLibrary;
    private static final Function myObjcMsgSend;

    static {
        myFoundationLibrary = Native.load("Foundation", MyFoundationLibrary.class, Collections.singletonMap("jna.encoding", "UTF8"));
        NativeLibrary nativeLibrary = ((Library.Handler) Proxy.getInvocationHandler(myFoundationLibrary)).getNativeLibrary();
        myObjcMsgSend = nativeLibrary.getFunction("objc_msgSend");
    }

    public static ID getObjcClass(String className) {
        return myFoundationLibrary.objc_getClass(className);
    }

    public static Pointer createSelector(String s) {
        return myFoundationLibrary.sel_registerName(s);
    }

    private static Object [] prepInvoke(ID id, Pointer selector, Object[] args) {
        Object[] invokArgs = new Object[args.length + 2];
        invokArgs[0] = id;
        invokArgs[1] = selector;
        System.arraycopy(args, 0, invokArgs, 2, args.length);
        return invokArgs;
    }

    public static ID invoke(final ID id, final Pointer selector, Object... args) {
        // objc_msgSend is called with the calling convention of the target method
        // on x86_64 this does not make a difference, but arm64 uses a different calling convention for varargs
        // it is therefore important to not call objc_msgSend as a vararg function
        return new ID(myObjcMsgSend.invokeLong(prepInvoke(id, selector, args)));
    }

    public static String toStringViaUTF8(ID cfString) {
        if (ID.NIL.equals(cfString)) return null;

        int lengthInChars = myFoundationLibrary.CFStringGetLength(cfString);
        int potentialLengthInBytes = 3 * lengthInChars + 1; // UTF8 fully escaped 16 bit chars, plus nul

        byte[] buffer = new byte[potentialLengthInBytes];
        byte ok = myFoundationLibrary.CFStringGetCString(cfString, buffer, buffer.length, MyFoundationLibrary.kCFStringEncodingUTF8);
        if (ok == 0) throw new RuntimeException("Could not convert string");
        return Native.toString(buffer);
    }

}

Atas ialah kandungan terperinci Menggunakan Java Native Access (JNA) untuk memanggil MacOS API. Untuk maklumat lanjut, sila ikut artikel berkaitan lain di laman web China PHP!