path: root/libjava/sun/misc/natUnsafe.cc

// natUnsafe.cc - Implementation of sun.misc.Unsafe native methods.

/* Copyright (C) 2006
   Free Software Foundation

   This file is part of libgcj.

This software is copyrighted work licensed under the terms of the
Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
details.  */

#include <gcj/cni.h>
#include <gcj/field.h>
#include <gcj/javaprims.h>
#include <jvm.h>
#include <sun/misc/Unsafe.h>
#include <java/lang/System.h>
#include <java/lang/InterruptedException.h>

#include <java/lang/Thread.h>
#include <java/lang/Long.h>

#include "sysdep/locks.h"

// Use a spinlock for multi-word accesses
class spinlock
{
  static volatile obj_addr_t lock;

public:

spinlock ()
  {
    while (! compare_and_swap (&lock, 0, 1))
      ;
  }
  ~spinlock ()
  {
    release_set (&lock, 0);
  }
};
  
// This is a single lock that is used for all synchronized accesses if
// the compiler can't generate inline compare-and-swap operations.  In
// most cases it'll never be used, but the i386 needs it for 64-bit
// locked accesses and so does PPC32.  It's worth building libgcj with
// target=i486 (or above) to get the inlines.
volatile obj_addr_t spinlock::lock;


static inline bool
compareAndSwap (volatile jint *addr, jint old, jint new_val)
{
  jboolean result = false;
  spinlock lock;
  if ((result = (*addr == old)))
    *addr = new_val;
  return result;
}
  
static inline bool
compareAndSwap (volatile jlong *addr, jlong old, jlong new_val)
{
  jboolean result = false;
  spinlock lock;
  if ((result = (*addr == old)))
    *addr = new_val;
  return result;
}
  
static inline bool
compareAndSwap (volatile jobject *addr, jobject old, jobject new_val)
{
  jboolean result = false;
  spinlock lock;
  if ((result = (*addr == old)))
    *addr = new_val;
  return result;
}
  

jlong
sun::misc::Unsafe::objectFieldOffset (::java::lang::reflect::Field *field)
{
  _Jv_Field *fld = _Jv_FromReflectedField (field);
  // FIXME: what if it is not an instance field?
  return fld->getOffset();
}

jint
sun::misc::Unsafe::arrayBaseOffset (jclass arrayClass)
{
  // FIXME: assert that arrayClass is array.
  jclass eltClass = arrayClass->getComponentType();
  return (jint)(jlong) _Jv_GetArrayElementFromElementType (NULL, eltClass);
}

jint
sun::misc::Unsafe::arrayIndexScale (jclass arrayClass)
{
  // FIXME: assert that arrayClass is array.
  jclass eltClass = arrayClass->getComponentType();
  if (eltClass->isPrimitive())
    return eltClass->size();
  return sizeof (void *);
}

// These methods are used when the compiler fails to generate inline
// versions of the compare-and-swap primitives.

jboolean
sun::misc::Unsafe::compareAndSwapInt (jobject obj, jlong offset,
				      jint expect, jint update)
{
  jint *addr = (jint *)((char *)obj + offset);
  return compareAndSwap (addr, expect, update);
}

jboolean
sun::misc::Unsafe::compareAndSwapLong (jobject obj, jlong offset,
				       jlong expect, jlong update)
{
  volatile jlong *addr = (jlong*)((char *) obj + offset);
  return compareAndSwap (addr, expect, update);
}

jboolean
sun::misc::Unsafe::compareAndSwapObject (jobject obj, jlong offset,
					 jobject expect, jobject update)
{
  jobject *addr = (jobject*)((char *) obj + offset);
  return compareAndSwap (addr, expect, update);
}

void
sun::misc::Unsafe::putOrderedInt (jobject obj, jlong offset, jint value)
{
  volatile jint *addr = (jint *) ((char *) obj + offset);
  *addr = value;
}

void
sun::misc::Unsafe::putOrderedLong (jobject obj, jlong offset, jlong value)
{
  volatile jlong *addr = (jlong *) ((char *) obj + offset);
  spinlock lock;
  *addr = value;
}

void
sun::misc::Unsafe::putOrderedObject (jobject obj, jlong offset, jobject value)
{
  volatile jobject *addr = (jobject *) ((char *) obj + offset);
  *addr = value;
}

void
sun::misc::Unsafe::putIntVolatile (jobject obj, jlong offset, jint value)
{
  write_barrier ();
  volatile jint *addr = (jint *) ((char *) obj + offset);
  *addr = value;
}

void
sun::misc::Unsafe::putLongVolatile (jobject obj, jlong offset, jlong value)
{
  volatile jlong *addr = (jlong *) ((char *) obj + offset);
  spinlock lock;
  *addr = value;
}

void
sun::misc::Unsafe::putObjectVolatile (jobject obj, jlong offset, jobject value)
{
  write_barrier ();
  volatile jobject *addr = (jobject *) ((char *) obj + offset);
  *addr = value;
}

#if 0  // FIXME
void
sun::misc::Unsafe::putInt (jobject obj, jlong offset, jint value)
{
  jint *addr = (jint *) ((char *) obj + offset);
  *addr = value;
}
#endif

void
sun::misc::Unsafe::putLong (jobject obj, jlong offset, jlong value)
{
  jlong *addr = (jlong *) ((char *) obj + offset);
  spinlock lock;
  *addr = value;
}

void
sun::misc::Unsafe::putObject (jobject obj, jlong offset, jobject value)
{
  jobject *addr = (jobject *) ((char *) obj + offset);
  *addr = value;
}

jint
sun::misc::Unsafe::getIntVolatile (jobject obj, jlong offset)
{
  volatile jint *addr = (jint *) ((char *) obj + offset);
  jint result = *addr;
  read_barrier ();
  return result;
}

jobject
sun::misc::Unsafe::getObjectVolatile (jobject obj, jlong offset)
{
  volatile jobject *addr = (jobject *) ((char *) obj + offset);
  jobject result = *addr;
  read_barrier ();
  return result;
}

jlong
sun::misc::Unsafe::getLong (jobject obj, jlong offset)
{
  jlong *addr = (jlong *) ((char *) obj + offset);
  spinlock lock;
  return *addr;
}

jlong
sun::misc::Unsafe::getLongVolatile (jobject obj, jlong offset)
{
  volatile jlong *addr = (jlong *) ((char *) obj + offset);
  spinlock lock;
  return *addr;
}

void
sun::misc::Unsafe::unpark (::java::lang::Thread *thread)
{
  natThread *nt = (natThread *) thread->data;
  nt->park_helper.unpark ();
}

void
sun::misc::Unsafe::park (jboolean isAbsolute, jlong time)
{
  using namespace ::java::lang;
  Thread *thread = Thread::currentThread();
  natThread *nt = (natThread *) thread->data;
  nt->park_helper.park (isAbsolute, time);
}