src/java_lang_System.cc - platform/art - Git at Google

 /*
  * Copyright (C) 2008 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #include "jni_internal.h"
 #include "object.h"

 #include "JniConstants.h" // Last to avoid problems with LOG redefinition.

 /*
  * We make guarantees about the atomicity of accesses to primitive
  * variables.  These guarantees also apply to elements of arrays.
  * In particular, 8-bit, 16-bit, and 32-bit accesses must be atomic and
  * must not cause "word tearing".  Accesses to 64-bit array elements must
  * either be atomic or treated as two 32-bit operations.  References are
  * always read and written atomically, regardless of the number of bits
  * used to represent them.
  *
  * We can't rely on standard libc functions like memcpy(3) and memmove(3)
  * in our implementation of System.arraycopy, because they may copy
  * byte-by-byte (either for the full run or for "unaligned" parts at the
  * start or end).  We need to use functions that guarantee 16-bit or 32-bit
  * atomicity as appropriate.
  *
  * System.arraycopy() is heavily used, so having an efficient implementation
  * is important.  The bionic libc provides a platform-optimized memory move
  * function that should be used when possible.  If it's not available,
  * the trivial "reference implementation" versions below can be used until
  * a proper version can be written.
  *
  * For these functions, The caller must guarantee that dst/src are aligned
  * appropriately for the element type, and that n is a multiple of the
  * element size.
  */
 #ifdef __BIONIC__
 #define HAVE_MEMMOVE_WORDS
 #endif

 #ifdef HAVE_MEMMOVE_WORDS
 extern "C" void _memmove_words(void* dst, const void* src, size_t n);
 #define move16 _memmove_words
 #define move32 _memmove_words
 #else
 static void move16(void* dst, const void* src, size_t n) {
   DCHECK_EQ((((uintptr_t) dst | (uintptr_t) src | n) & 0x01), 0U);

   uint16_t* d = reinterpret_cast<uint16_t*>(dst);
   const uint16_t* s = reinterpret_cast<const uint16_t*>(src);

   n /= sizeof(uint16_t);

   if (d < s) {
     // Copy forwards.
     while (n--) {
       *d++ = *s++;
     }
   } else {
     // Copy backwards.
     d += n;
     s += n;
     while (n--) {
       *--d = *--s;
     }
   }
 }

 static void move32(void* dst, const void* src, size_t n) {
   DCHECK_EQ((((uintptr_t) dst | (uintptr_t) src | n) & 0x03), 0U);

   uint32_t* d = reinterpret_cast<uint32_t*>(dst);
   const uint32_t* s = reinterpret_cast<const uint32_t*>(src);

   n /= sizeof(uint32_t);

   if (d < s) {
     // Copy forwards.
     while (n--) {
       *d++ = *s++;
     }
   } else {
     // Copy backwards.
     d += n;
     s += n;
     while (n--) {
       *--d = *--s;
     }
   }
 }
 #endif // HAVE_MEMMOVE_WORDS

 namespace art {

 static void ThrowArrayStoreException_NotAnArray(const char* identifier, Object* array) {
   std::string actualType(PrettyTypeOf(array));
   Thread::Current()->ThrowNewExceptionF("Ljava/lang/ArrayStoreException;",
       "%s of type %s is not an array", identifier, actualType.c_str());
 }

 static void System_arraycopy(JNIEnv* env, jclass, jobject javaSrc, jint srcPos, jobject javaDst, jint dstPos, jint length) {
   ScopedThreadStateChange tsc(Thread::Current(), Thread::kRunnable);
   Thread* self = Thread::Current();

   // Null pointer checks.
   if (javaSrc == NULL) {
     self->ThrowNewException("Ljava/lang/NullPointerException;", "src == null");
     return;
   }
   if (javaDst == NULL) {
     self->ThrowNewException("Ljava/lang/NullPointerException;", "dst == null");
     return;
   }

   // Make sure source and destination are both arrays.
   Object* srcObject = Decode<Object*>(env, javaSrc);
   Object* dstObject = Decode<Object*>(env, javaDst);
   if (!srcObject->IsArrayInstance()) {
     ThrowArrayStoreException_NotAnArray("source", srcObject);
     return;
   }
   if (!dstObject->IsArrayInstance()) {
     ThrowArrayStoreException_NotAnArray("destination", dstObject);
     return;
   }
   Array* srcArray = srcObject->AsArray();
   Array* dstArray = dstObject->AsArray();
   Class* srcComponentType = srcArray->GetClass()->GetComponentType();
   Class* dstComponentType = dstArray->GetClass()->GetComponentType();

   // Bounds checking.
   if (srcPos < 0 || dstPos < 0 || length < 0 || srcPos > srcArray->GetLength() - length || dstPos > dstArray->GetLength() - length) {
     self->ThrowNewExceptionF("Ljava/lang/ArrayIndexOutOfBoundsException;",
         "src.length=%d srcPos=%d dst.length=%d dstPos=%d length=%d",
         srcArray->GetLength(), srcPos, dstArray->GetLength(), dstPos, length);
     return;
   }

   // Handle primitive arrays.
   if (srcComponentType->IsPrimitive() || dstComponentType->IsPrimitive()) {
     // If one of the arrays holds a primitive type the other array must hold the exact same type.
     if (srcComponentType->IsPrimitive() != dstComponentType->IsPrimitive() || srcComponentType != dstComponentType) {
       std::string srcType(PrettyTypeOf(srcArray));
       std::string dstType(PrettyTypeOf(dstArray));
       self->ThrowNewExceptionF("Ljava/lang/ArrayStoreException;",
           "Incompatible types: src=%s, dst=%s", srcType.c_str(), dstType.c_str());
       return;
     }

     size_t width = srcArray->GetClass()->GetComponentSize();
     uint8_t* dstBytes = reinterpret_cast<uint8_t*>(dstArray->GetRawData(width));
     const uint8_t* srcBytes = reinterpret_cast<const uint8_t*>(srcArray->GetRawData(width));

     switch (width) {
     case 1:
       memmove(dstBytes + dstPos, srcBytes + srcPos, length);
       break;
     case 2:
       move16(dstBytes + dstPos * 2, srcBytes + srcPos * 2, length * 2);
       break;
     case 4:
       move32(dstBytes + dstPos * 4, srcBytes + srcPos * 4, length * 4);
       break;
     case 8:
       // We don't need to guarantee atomicity of the entire 64-bit word.
       move32(dstBytes + dstPos * 8, srcBytes + srcPos * 8, length * 8);
       break;
     default:
       LOG(FATAL) << "Unknown primitive array type: " << PrettyTypeOf(srcArray);
     }

     return;
   }

   // Neither class is primitive. Are the types trivially compatible?
   const size_t width = sizeof(Object*);
   uint8_t* dstBytes = reinterpret_cast<uint8_t*>(dstArray->GetRawData(width));
   const uint8_t* srcBytes = reinterpret_cast<const uint8_t*>(srcArray->GetRawData(width));
   if (dstArray == srcArray || dstComponentType->IsAssignableFrom(srcComponentType)) {
     // Yes. Bulk copy.
     COMPILE_ASSERT(sizeof(width) == sizeof(uint32_t), move32_assumes_Object_references_are_32_bit);
     move32(dstBytes + dstPos * width, srcBytes + srcPos * width, length * width);
     Runtime::Current()->GetHeap()->WriteBarrierArray(dstArray, dstPos, length);
     return;
   }

   // The arrays are not trivially compatible. However, we may still be able to copy some or all of
   // the elements if the source objects are compatible (for example, copying an Object[] to
   // String[], the Objects being copied might actually be Strings).
   // We can't do a bulk move because that would introduce a check-use race condition, so we copy
   // elements one by one.

   // We already dealt with overlapping copies, so we don't need to cope with that case below.
   CHECK_NE(dstArray, srcArray);

   Object* const * srcObjects = reinterpret_cast<Object* const *>(srcBytes + srcPos * width);
   Object** dstObjects = reinterpret_cast<Object**>(dstBytes + dstPos * width);
   Class* dstClass = dstArray->GetClass()->GetComponentType();

   // We want to avoid redundant IsAssignableFrom checks where possible, so we cache a class that
   // we know is assignable to the destination array's component type.
   Class* lastAssignableElementClass = dstClass;

   Object* o = NULL;
   int i = 0;
   for (; i < length; ++i) {
     o = srcObjects[i];
     if (o != NULL) {
       Class* oClass = o->GetClass();
       if (lastAssignableElementClass == oClass) {
         dstObjects[i] = o;
       } else if (dstClass->IsAssignableFrom(oClass)) {
         lastAssignableElementClass = oClass;
         dstObjects[i] = o;
       } else {
         // Can't put this element into the array.
         break;
       }
     } else {
       dstObjects[i] = NULL;
     }
   }

   Runtime::Current()->GetHeap()->WriteBarrierArray(dstArray, dstPos, length);
   if (i != length) {
     std::string actualSrcType(PrettyTypeOf(o));
     std::string dstType(PrettyTypeOf(dstArray));
     self->ThrowNewExceptionF("Ljava/lang/ArrayStoreException;",
         "source[%d] of type %s cannot be stored in destination array of type %s",
         srcPos + i, actualSrcType.c_str(), dstType.c_str());
     return;
   }
 }

 static jint System_identityHashCode(JNIEnv* env, jclass, jobject javaObject) {
   Object* o = Decode<Object*>(env, javaObject);
   return static_cast<jint>(reinterpret_cast<uintptr_t>(o));
 }

 static JNINativeMethod gMethods[] = {
   NATIVE_METHOD(System, arraycopy, "(Ljava/lang/Object;ILjava/lang/Object;II)V"),
   NATIVE_METHOD(System, identityHashCode, "(Ljava/lang/Object;)I"),
 };

 void register_java_lang_System(JNIEnv* env) {
     jniRegisterNativeMethods(env, "java/lang/System", gMethods, NELEM(gMethods));
 }

 }  // namespace art
	/*
	* Copyright (C) 2008 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#include "jni_internal.h"
	#include "object.h"

	#include "JniConstants.h" // Last to avoid problems with LOG redefinition.

	/*
	* We make guarantees about the atomicity of accesses to primitive
	* variables. These guarantees also apply to elements of arrays.
	* In particular, 8-bit, 16-bit, and 32-bit accesses must be atomic and
	* must not cause "word tearing". Accesses to 64-bit array elements must
	* either be atomic or treated as two 32-bit operations. References are
	* always read and written atomically, regardless of the number of bits
	* used to represent them.
	*
	* We can't rely on standard libc functions like memcpy(3) and memmove(3)
	* in our implementation of System.arraycopy, because they may copy
	* byte-by-byte (either for the full run or for "unaligned" parts at the
	* start or end). We need to use functions that guarantee 16-bit or 32-bit
	* atomicity as appropriate.
	*
	* System.arraycopy() is heavily used, so having an efficient implementation
	* is important. The bionic libc provides a platform-optimized memory move
	* function that should be used when possible. If it's not available,
	* the trivial "reference implementation" versions below can be used until
	* a proper version can be written.
	*
	* For these functions, The caller must guarantee that dst/src are aligned
	* appropriately for the element type, and that n is a multiple of the
	* element size.
	*/
	#ifdef __BIONIC__
	#define HAVE_MEMMOVE_WORDS
	#endif

	#ifdef HAVE_MEMMOVE_WORDS
	extern "C" void _memmove_words(void* dst, const void* src, size_t n);
	#define move16 _memmove_words
	#define move32 _memmove_words
	#else
	static void move16(void* dst, const void* src, size_t n) {
	DCHECK_EQ((((uintptr_t) dst \| (uintptr_t) src \| n) & 0x01), 0U);

	uint16_t* d = reinterpret_cast<uint16_t*>(dst);
	const uint16_t* s = reinterpret_cast<const uint16_t*>(src);

	n /= sizeof(uint16_t);

	if (d < s) {
	// Copy forwards.
	while (n--) {
	d++ = s++;
	}
	} else {
	// Copy backwards.
	d += n;
	s += n;
	while (n--) {
	--d = --s;
	}
	}
	}

	static void move32(void* dst, const void* src, size_t n) {
	DCHECK_EQ((((uintptr_t) dst \| (uintptr_t) src \| n) & 0x03), 0U);

	uint32_t* d = reinterpret_cast<uint32_t*>(dst);
	const uint32_t* s = reinterpret_cast<const uint32_t*>(src);

	n /= sizeof(uint32_t);

	if (d < s) {
	// Copy forwards.
	while (n--) {
	d++ = s++;
	}
	} else {
	// Copy backwards.
	d += n;
	s += n;
	while (n--) {
	--d = --s;
	}
	}
	}
	#endif // HAVE_MEMMOVE_WORDS

	namespace art {

	static void ThrowArrayStoreException_NotAnArray(const char* identifier, Object* array) {
	std::string actualType(PrettyTypeOf(array));
	Thread::Current()->ThrowNewExceptionF("Ljava/lang/ArrayStoreException;",
	"%s of type %s is not an array", identifier, actualType.c_str());
	}

	static void System_arraycopy(JNIEnv* env, jclass, jobject javaSrc, jint srcPos, jobject javaDst, jint dstPos, jint length) {
	ScopedThreadStateChange tsc(Thread::Current(), Thread::kRunnable);
	Thread* self = Thread::Current();

	// Null pointer checks.
	if (javaSrc == NULL) {
	self->ThrowNewException("Ljava/lang/NullPointerException;", "src == null");
	return;
	}
	if (javaDst == NULL) {
	self->ThrowNewException("Ljava/lang/NullPointerException;", "dst == null");
	return;
	}

	// Make sure source and destination are both arrays.
	Object* srcObject = Decode<Object*>(env, javaSrc);
	Object* dstObject = Decode<Object*>(env, javaDst);
	if (!srcObject->IsArrayInstance()) {
	ThrowArrayStoreException_NotAnArray("source", srcObject);
	return;
	}
	if (!dstObject->IsArrayInstance()) {
	ThrowArrayStoreException_NotAnArray("destination", dstObject);
	return;
	}
	Array* srcArray = srcObject->AsArray();
	Array* dstArray = dstObject->AsArray();
	Class* srcComponentType = srcArray->GetClass()->GetComponentType();
	Class* dstComponentType = dstArray->GetClass()->GetComponentType();

	// Bounds checking.
	if (srcPos < 0 \|\| dstPos < 0 \|\| length < 0 \|\| srcPos > srcArray->GetLength() - length \|\| dstPos > dstArray->GetLength() - length) {
	self->ThrowNewExceptionF("Ljava/lang/ArrayIndexOutOfBoundsException;",
	"src.length=%d srcPos=%d dst.length=%d dstPos=%d length=%d",
	srcArray->GetLength(), srcPos, dstArray->GetLength(), dstPos, length);
	return;
	}

	// Handle primitive arrays.
	if (srcComponentType->IsPrimitive() \|\| dstComponentType->IsPrimitive()) {
	// If one of the arrays holds a primitive type the other array must hold the exact same type.
	if (srcComponentType->IsPrimitive() != dstComponentType->IsPrimitive() \|\| srcComponentType != dstComponentType) {
	std::string srcType(PrettyTypeOf(srcArray));
	std::string dstType(PrettyTypeOf(dstArray));
	self->ThrowNewExceptionF("Ljava/lang/ArrayStoreException;",
	"Incompatible types: src=%s, dst=%s", srcType.c_str(), dstType.c_str());
	return;
	}

	size_t width = srcArray->GetClass()->GetComponentSize();
	uint8_t* dstBytes = reinterpret_cast<uint8_t*>(dstArray->GetRawData(width));
	const uint8_t* srcBytes = reinterpret_cast<const uint8_t*>(srcArray->GetRawData(width));

	switch (width) {
	case 1:
	memmove(dstBytes + dstPos, srcBytes + srcPos, length);
	break;
	case 2:
	move16(dstBytes + dstPos * 2, srcBytes + srcPos * 2, length * 2);
	break;
	case 4:
	move32(dstBytes + dstPos * 4, srcBytes + srcPos * 4, length * 4);
	break;
	case 8:
	// We don't need to guarantee atomicity of the entire 64-bit word.
	move32(dstBytes + dstPos * 8, srcBytes + srcPos * 8, length * 8);
	break;
	default:
	LOG(FATAL) << "Unknown primitive array type: " << PrettyTypeOf(srcArray);
	}

	return;
	}

	// Neither class is primitive. Are the types trivially compatible?
	const size_t width = sizeof(Object*);
	uint8_t* dstBytes = reinterpret_cast<uint8_t*>(dstArray->GetRawData(width));
	const uint8_t* srcBytes = reinterpret_cast<const uint8_t*>(srcArray->GetRawData(width));
	if (dstArray == srcArray \|\| dstComponentType->IsAssignableFrom(srcComponentType)) {
	// Yes. Bulk copy.
	COMPILE_ASSERT(sizeof(width) == sizeof(uint32_t), move32_assumes_Object_references_are_32_bit);
	move32(dstBytes + dstPos * width, srcBytes + srcPos * width, length * width);
	Runtime::Current()->GetHeap()->WriteBarrierArray(dstArray, dstPos, length);
	return;
	}

	// The arrays are not trivially compatible. However, we may still be able to copy some or all of
	// the elements if the source objects are compatible (for example, copying an Object[] to
	// String[], the Objects being copied might actually be Strings).
	// We can't do a bulk move because that would introduce a check-use race condition, so we copy
	// elements one by one.

	// We already dealt with overlapping copies, so we don't need to cope with that case below.
	CHECK_NE(dstArray, srcArray);

	Object* const * srcObjects = reinterpret_cast<Object* const >(srcBytes + srcPos width);
	Object dstObjects = reinterpret_cast<Object>(dstBytes + dstPos * width);
	Class* dstClass = dstArray->GetClass()->GetComponentType();

	// We want to avoid redundant IsAssignableFrom checks where possible, so we cache a class that
	// we know is assignable to the destination array's component type.
	Class* lastAssignableElementClass = dstClass;

	Object* o = NULL;
	int i = 0;
	for (; i < length; ++i) {
	o = srcObjects[i];
	if (o != NULL) {
	Class* oClass = o->GetClass();
	if (lastAssignableElementClass == oClass) {
	dstObjects[i] = o;
	} else if (dstClass->IsAssignableFrom(oClass)) {
	lastAssignableElementClass = oClass;
	dstObjects[i] = o;
	} else {
	// Can't put this element into the array.
	break;
	}
	} else {
	dstObjects[i] = NULL;
	}
	}

	Runtime::Current()->GetHeap()->WriteBarrierArray(dstArray, dstPos, length);
	if (i != length) {
	std::string actualSrcType(PrettyTypeOf(o));
	std::string dstType(PrettyTypeOf(dstArray));
	self->ThrowNewExceptionF("Ljava/lang/ArrayStoreException;",
	"source[%d] of type %s cannot be stored in destination array of type %s",
	srcPos + i, actualSrcType.c_str(), dstType.c_str());
	return;
	}
	}

	static jint System_identityHashCode(JNIEnv* env, jclass, jobject javaObject) {
	Object* o = Decode<Object*>(env, javaObject);
	return static_cast<jint>(reinterpret_cast<uintptr_t>(o));
	}

	static JNINativeMethod gMethods[] = {
	NATIVE_METHOD(System, arraycopy, "(Ljava/lang/Object;ILjava/lang/Object;II)V"),
	NATIVE_METHOD(System, identityHashCode, "(Ljava/lang/Object;)I"),
	};

	void register_java_lang_System(JNIEnv* env) {
	jniRegisterNativeMethods(env, "java/lang/System", gMethods, NELEM(gMethods));
	}

	} // namespace art