Name: viR10068 Date: 11/16/2001


The current specification at http://java.sun.com/j2se/1.4/docs/guide/jni/jni-14.html
for function GetDirectBufferCapacity says:
"RETURNS

      Returns the capacity in bytes of the memory region associated with the
      buffer. Returns -1 if the given object is not a direct
      java.nio.Buffer, or if JNI access to direct buffers is not supported
      by this virtual machine."

However the call of this function for misaligned short (or int) buffer returns
-1 instead of buffer capacity. Note, that for aligned buffer
GetDirectBufferCapacity returns positive number as expected. See log for details.

Please, change the JVM behavior or clarify the specification.

Log:
%java -version && javac -d . gdbc00101m1.java && cc -G -KPIC -o libjckjni.so -Iinclude
gdbc00101m1.c && java -Xfuture javasoft.sqe.tests.vm.jni.gdbc001.gdbc00101m1.gdbc00101m1
java version "1.4.0-rc"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-rc-b86)
Java HotSpot(TM) Client VM (build 1.4.0-rc-b86, mixed mode)
misaligned buffer
shortBuf.capacity() is 2
getDirectBufferCapacity(shortBuf) is -1
aligned buffer
shortBuf1.capacity() is 2
getDirectBufferCapacity(shortBuf1) is 2
%

Sources:
=============================== gdbc00101m1.java
package javasoft.sqe.tests.vm.jni.gdbc001.gdbc00101m1;

import java.io.PrintStream;
import java.nio.ByteBuffer;
import java.nio.ShortBuffer;
import java.nio.IntBuffer;

public class gdbc00101m1 {

    private static native long getDirectBufferCapacity(Object buf);

    public static int testChecks(PrintStream out) {

        boolean res = false;

        // Positive tests
        try {
            ByteBuffer buf = ByteBuffer.allocateDirect(8);

            out.println("misaligned buffer");
            buf.position(3);
            ShortBuffer shortBuf = buf.asShortBuffer();
            out.println("shortBuf.capacity() is " + shortBuf.capacity());
            out.println("getDirectBufferCapacity(shortBuf) is " +
getDirectBufferCapacity(shortBuf));
            
            out.println("aligned buffer");
            buf.position(4);
            ShortBuffer shortBuf1 = buf.asShortBuffer();
            out.println("shortBuf1.capacity() is " + shortBuf1.capacity());
            out.println("getDirectBufferCapacity(shortBuf1) is " +
getDirectBufferCapacity(shortBuf1));
        } catch (Exception e) {
            e.printStackTrace();
            out.println("Unexpected exception: " + e);
            return 2/*STATUS_FAILED*/;
        }
        return 0/*STATUS_PASSED*/;
    }

    static String loadLibraryStatus = "";
    static {
        if(!loadLib("gdbc00101m1"))
            loadLib("jckjni");
    }

    static boolean loadLib(String libName){
        try {
            System.loadLibrary(libName);
            loadLibraryStatus = null;
            return true;
        } catch (SecurityException e) {
            loadLibraryStatus += "loadLibrary(\"" + libName + "\") throws: " + e + "\n";
        } catch (UnsatisfiedLinkError e) {
            loadLibraryStatus += "loadLibrary(\"" + libName + "\") throws: " + e + "\n";
        }
        return false;
    }

    public static int run(String argv[], PrintStream out) {

        if (loadLibraryStatus!=null) {
            out.println("Library loading:\n" + loadLibraryStatus);
        }
        return testChecks(out);
    }

    public static void main(String argv[]) {
        System.exit(run(argv, System.out) + 95/*STATUS_TEMP*/);
    }
}
=============================== gdba00101m1.c
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include "jckjni.h"

#ifdef __cplusplus
extern "C" {
#endif

#ifndef JNI_ENV_ARG

#ifdef __cplusplus
#define JNI_ENV_ARG(x, y) y
#define JNI_ENV_PTR(x) x
#else
#define JNI_ENV_ARG(x,y) x, y
#define JNI_ENV_PTR(x) (*x)
#endif

#endif


JNIEXPORT jlong JNICALL
Java_javasoft_sqe_tests_vm_jni_gdbc001_gdbc00101m1_gdbc00101m1_getDirectBufferCapacity
(JNIEnv *env, jobject obj, jobject buf) {
return JNI_ENV_PTR(env)->GetDirectBufferCapacity(JNI_ENV_ARG(env,buf));
}

#ifdef __cplusplus
}
#endif
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