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/*
* 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 "scoped_thread_state_change.h"
/*
* 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)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
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) {
ScopedObjectAccess soa(env);
// Null pointer checks.
if (javaSrc == NULL) {
soa.Self()->ThrowNewException("Ljava/lang/NullPointerException;", "src == null");
return;
}
if (javaDst == NULL) {
soa.Self()->ThrowNewException("Ljava/lang/NullPointerException;", "dst == null");
return;
}
// Make sure source and destination are both arrays.
Object* srcObject = soa.Decode<Object*>(javaSrc);
Object* dstObject = soa.Decode<Object*>(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) {
soa.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));
soa.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));
soa.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) {
ScopedObjectAccess soa(env);
Object* o = soa.Decode<Object*>(javaObject);
return static_cast<jint>(o->IdentityHashCode());
}
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) {
REGISTER_NATIVE_METHODS("java/lang/System");
}
} // namespace art