java-native-access/jna · error · UnsupportedOperationException

This pointer is opaque:

Error message

This pointer is opaque: 

What it means

JNA's Pointer.Opaque throws UnsupportedOperationException with the message "This pointer is opaque: " + this for every memory operation. This entry is the short[] write overload: opaque memory must not be mutated.

Solutions

1. Do not write via the opaque pointer; use it only to identify the native object.
2. Allocate a Memory buffer, write the short[] there, and pass it to a native function.
3. Check the pointer for opacity before writing.
4. Expose a native setter (e.g. void set(Handle, short*, int)) and call it with the handle.

Example fix

// before
Pointer opaque = lib.getHandle();
opaque.write(0, new short[]{1, 2}, 0, 2); // throws

// after
Memory mem = new Memory(4);
mem.write(0, new short[]{1, 2}, 0, 2);
lib.setHandleShorts(opaque, mem, 2);

if (p == null || p.toString().startsWith("opaque@")) {
    throw new IllegalArgumentException("cannot write short[] to opaque pointer");
}

public static boolean supportsWrite(Pointer p) {
    return p != null && !p.toString().startsWith("opaque@");
}

try {
    p.write(bOff, buf, 0, len);
} catch (UnsupportedOperationException e) {
    if (String.valueOf(e.getMessage()).contains("opaque")) {
        Memory mem = new Memory((long) len * 2);
        mem.write(0, buf, 0, len);
        nativeSetShorts(handle, mem, len);
        return;
    }
    throw e;
}

When it happens

Trigger: Calling Pointer.write(long bOff, short[] buf, int index, int length) on a Pointer.Opaque instance.

Common situations: Filling short arrays (e.g. audio samples, 16-bit data) through a handle obtained from Pointer.createOpaque or an opaque native return value.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• Bounds exceeds available space : size=
• Byte boundary must be a power of two
• Insufficient memory to align to the requested boundary
• Invalid offset
• Maximum argument count is

AI-assisted analysis of java-native-access/jna@d036ad9781 (2026-09-12). Data as JSON: /api/errors/73ad5539649bea80. Report an issue: GitHub.

Appendix: source

Thrown at src/com/sun/jna/Pointer.java:1260

        @Override
        public void read(long bOff, Pointer[] buf, int index, int length) {
            throw new UnsupportedOperationException(MSG);
        }
        @Override
        public void write(long bOff, byte[] buf, int index, int length) {
            throw new UnsupportedOperationException(MSG);
        }
        @Override
        public void write(long bOff, char[] buf, int index, int length) {
            throw new UnsupportedOperationException(MSG);
        }
        @Override
        public void write(long bOff, short[] buf, int index, int length) {
            throw new UnsupportedOperationException(MSG);
        }
        @Override
        public void write(long bOff, int[] buf, int index, int length) {
            throw new UnsupportedOperationException(MSG);
        }
        @Override
        public void write(long bOff, long[] buf, int index, int length) {
            throw new UnsupportedOperationException(MSG);
        }
        @Override
        public void write(long bOff, float[] buf, int index, int length) {
            throw new UnsupportedOperationException(MSG);
        }
        @Override
        public void write(long bOff, double[] buf, int index, int length) {
            throw new UnsupportedOperationException(MSG);
        }
        @Override
        public void write(long bOff, Pointer[] buf, int index, int length) {
            throw new UnsupportedOperationException(MSG);
        }
        @Override

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