JNI Header Wrapper a lightweight alternative to JNA or JNR and a helper to resolve a native lib by name and libtool version.

Unlike JNR or JNA

• all macro constants are natively resolved.
• all structures will be natively allocated and its filed natively accessed. StructTermios in Termios.java and the jni bindings Termios_Termios.c and TermiosDefines.c and TermiosFunctions.c . Struct termios varies over the OS and even on Linux on different architectures like (i.e. mips is different from the rest).
• different sizes, alignments and offset of struct members are handled natively like stuct mcontext_t Tests testAlignOfMcontext_t testSizeOfMcontext_t in SignalTest.java. Examples for struct and union and function pointer are in teh exaples modules.
• it does not use sun.misc.Unsafe but allocate the memory by itself.
• callbacks from and calls of native functions are supported Callback_I_V_Impl.java, and its counterpart CallNative_J_V.java, and their common ancestor FunctionPtr_I_V.java.

A running "real life" comparison can be found here: JNHW-Example: Compare JNHW, JNR, JNA.

Add this dependency for POSIX.

<dependency>
    <groupId>de.ibapl.jnhw</groupId>
    <artifactId>de.ibapl.jnhw.posix</artifactId>
    <version>[3.0.0,4.0.0)</version>
</dependency>

and this for the Windows API

<dependency>
    <groupId>de.ibapl.jnhw</groupId>
    <artifactId>de.ibapl.jnhw.winapi</artifactId>
    <version>[3.0.0,4.0.0)</version>
</dependency>

If an native error occured and the called function flags an error condition to the caller. One calls for ISO C errno and for the windows API GetLastError(). this is done in the jni wrapper which throws the checked exception NativeErrorException in that case.

n.a. ... the VM and/or feature are not available.

See subdirectory it/hello-world/. run mvn exec:java -Dexec.mainClass="de.ibapl.jnhw.it.hello_world.App" in it/hello_world.

Import Unistd in a static manner so the code may become less noisy.

package de.ibapl.jnhw.it.hello_world;

import de.ibapl.jnhw.NativeErrorException;
//Import only the needed define from the wrapper of posix's unistd.h.h
import static de.ibapl.jnhw.posix.Unistd.STDOUT_FILENO;
//Import only the needed method from the wrapper of iso c's unistd.h.h
import static de.ibapl.jnhw.posix.Unistd.write;

public class Posix {

	public static void sayHello() throws NativeErrorException {
		int bytesWritten = write(STDOUT_FILENO, "Hello World! from POSIX\n".getBytes());
                System.out.println("Bytes written: "   bytesWritten);
	}

}

package de.ibapl.jnhw.it.hello_world;

import de.ibapl.jnhw.NativeErrorException;
//Import only the needed define from the wrapper of processenv.h
import static de.ibapl.jnhw.winapi.Winbase.STD_OUTPUT_HANDLE;
//Import only the needed method from the wrapper of processenv.h
import static de.ibapl.jnhw.winapi.ProcessEnv.GetStdHandle;
//Import only the needed method from the wrapper of fileapi.h
import static de.ibapl.jnhw.winapi.Fileapi.WriteFile;

public class Windows {

	public static void sayHello() throws NativeErrorException {
		int bytesWritten = WriteFile(GetStdHandle(STD_OUTPUT_HANDLE), "Hello World! from WIN API\n".getBytes());
                System.out.println("Bytes written: "   bytesWritten);
	}

}

create a file named test.c and include the needed headers. run

gcc  -dD -dI -E test.c  | less

to see the preprocessed defines