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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 "common_throws.h"
-#include "gc/accounting/card_table-inl.h"
-#include "jni_internal.h"
-#include "mirror/array.h"
-#include "mirror/class.h"
-#include "mirror/class-inl.h"
-#include "mirror/object-inl.h"
-#include "mirror/object_array-inl.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.
- */
-
-/*
- * Works like memmove(), except:
- * - if all arguments are at least 32-bit aligned, we guarantee that we
- * will use operations that preserve atomicity of 32-bit values
- * - if not, we guarantee atomicity of 16-bit values
- *
- * If all three arguments are not at least 16-bit aligned, the behavior
- * of this function is undefined. (We could remove this restriction by
- * testing for unaligned values and punting to memmove(), but that's
- * not currently useful.)
- *
- * TODO: add loop for 64-bit alignment
- * TODO: use __builtin_prefetch
- * TODO: write ARM/MIPS/x86 optimized versions
- */
-void MemmoveWords(void* dst, const void* src, size_t n) {
- DCHECK_EQ((((uintptr_t) dst | (uintptr_t) src | n) & 0x01), 0U);
-
- char* d = reinterpret_cast<char*>(dst);
- const char* s = reinterpret_cast<const char*>(src);
- size_t copyCount;
-
- // If the source and destination pointers are the same, this is
- // an expensive no-op. Testing for an empty move now allows us
- // to skip a check later.
- if (n == 0 || d == s) {
- return;
- }
-
- // Determine if the source and destination buffers will overlap if
- // we copy data forward (i.e. *dst++ = *src++).
- //
- // It's okay if the destination buffer starts before the source and
- // there is some overlap, because the reader is always ahead of the
- // writer.
- if (LIKELY((d < s) || ((size_t)(d - s) >= n))) {
- // Copy forward. We prefer 32-bit loads and stores even for 16-bit
- // data, so sort that out.
- if (((reinterpret_cast<uintptr_t>(d) | reinterpret_cast<uintptr_t>(s)) & 0x03) != 0) {
- // Not 32-bit aligned. Two possibilities:
- // (1) Congruent, we can align to 32-bit by copying one 16-bit val
- // (2) Non-congruent, we can do one of:
- // a. copy whole buffer as a series of 16-bit values
- // b. load/store 32 bits, using shifts to ensure alignment
- // c. just copy the as 32-bit values and assume the CPU
- // will do a reasonable job
- //
- // We're currently using (a), which is suboptimal.
- if (((reinterpret_cast<uintptr_t>(d) ^ reinterpret_cast<uintptr_t>(s)) & 0x03) != 0) {
- copyCount = n;
- } else {
- copyCount = 2;
- }
- n -= copyCount;
- copyCount /= sizeof(uint16_t);
-
- while (copyCount--) {
- *reinterpret_cast<uint16_t*>(d) = *reinterpret_cast<const uint16_t*>(s);
- d += sizeof(uint16_t);
- s += sizeof(uint16_t);
- }
- }
-
- // Copy 32-bit aligned words.
- copyCount = n / sizeof(uint32_t);
- while (copyCount--) {
- *reinterpret_cast<uint32_t*>(d) = *reinterpret_cast<const uint32_t*>(s);
- d += sizeof(uint32_t);
- s += sizeof(uint32_t);
- }
-
- // Check for leftovers. Either we finished exactly, or we have one remaining 16-bit chunk.
- if ((n & 0x02) != 0) {
- *(uint16_t*)d = *(uint16_t*)s;
- }
- } else {
- // Copy backward, starting at the end.
- d += n;
- s += n;
-
- if (((reinterpret_cast<uintptr_t>(d) | reinterpret_cast<uintptr_t>(s)) & 0x03) != 0) {
- // try for 32-bit alignment.
- if (((reinterpret_cast<uintptr_t>(d) ^ reinterpret_cast<uintptr_t>(s)) & 0x03) != 0) {
- copyCount = n;
- } else {
- copyCount = 2;
- }
- n -= copyCount;
- copyCount /= sizeof(uint16_t);
-
- while (copyCount--) {
- d -= sizeof(uint16_t);
- s -= sizeof(uint16_t);
- *reinterpret_cast<uint16_t*>(d) = *reinterpret_cast<const uint16_t*>(s);
- }
- }
-
- // Copy 32-bit aligned words.
- copyCount = n / sizeof(uint32_t);
- while (copyCount--) {
- d -= sizeof(uint32_t);
- s -= sizeof(uint32_t);
- *reinterpret_cast<uint32_t*>(d) = *reinterpret_cast<const uint32_t*>(s);
- }
-
- // Copy leftovers.
- if ((n & 0x02) != 0) {
- d -= sizeof(uint16_t);
- s -= sizeof(uint16_t);
- *reinterpret_cast<uint16_t*>(d) = *reinterpret_cast<const uint16_t*>(s);
- }
- }
-}
-
-#define move16 MemmoveWords
-#define move32 MemmoveWords
-
-namespace art {
-
-static void ThrowArrayStoreException_NotAnArray(const char* identifier, mirror::Object* array)
- SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
- std::string actualType(PrettyTypeOf(array));
- Thread* self = Thread::Current();
- ThrowLocation throw_location = self->GetCurrentLocationForThrow();
- self->ThrowNewExceptionF(throw_location, "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 (UNLIKELY(javaSrc == NULL)) {
- ThrowNullPointerException(NULL, "src == null");
- return;
- }
- if (UNLIKELY(javaDst == NULL)) {
- ThrowNullPointerException(NULL, "dst == null");
- return;
- }
-
- // Make sure source and destination are both arrays.
- mirror::Object* srcObject = soa.Decode<mirror::Object*>(javaSrc);
- mirror::Object* dstObject = soa.Decode<mirror::Object*>(javaDst);
- if (UNLIKELY(!srcObject->IsArrayInstance())) {
- ThrowArrayStoreException_NotAnArray("source", srcObject);
- return;
- }
- if (UNLIKELY(!dstObject->IsArrayInstance())) {
- ThrowArrayStoreException_NotAnArray("destination", dstObject);
- return;
- }
- mirror::Array* srcArray = srcObject->AsArray();
- mirror::Array* dstArray = dstObject->AsArray();
- mirror::Class* srcComponentType = srcArray->GetClass()->GetComponentType();
- mirror::Class* dstComponentType = dstArray->GetClass()->GetComponentType();
-
- // Bounds checking.
- if (UNLIKELY(srcPos < 0 || dstPos < 0 || length < 0 || srcPos > srcArray->GetLength() - length || dstPos > dstArray->GetLength() - length)) {
- ThrowLocation throw_location = soa.Self()->GetCurrentLocationForThrow();
- soa.Self()->ThrowNewExceptionF(throw_location, "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 (UNLIKELY(srcComponentType != dstComponentType)) {
- std::string srcType(PrettyTypeOf(srcArray));
- std::string dstType(PrettyTypeOf(dstArray));
- ThrowLocation throw_location = soa.Self()->GetCurrentLocationForThrow();
- soa.Self()->ThrowNewExceptionF(throw_location, "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(mirror::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);
-
- mirror::Object* const * srcObjects =
- reinterpret_cast<mirror::Object* const *>(srcBytes + srcPos * width);
- mirror::Object** dstObjects = reinterpret_cast<mirror::Object**>(dstBytes + dstPos * width);
- mirror::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.
- mirror::Class* lastAssignableElementClass = dstClass;
-
- mirror::Object* o = NULL;
- int i = 0;
- for (; i < length; ++i) {
- o = srcObjects[i];
- if (o != NULL) {
- mirror::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 (UNLIKELY(i != length)) {
- std::string actualSrcType(PrettyTypeOf(o));
- std::string dstType(PrettyTypeOf(dstArray));
- ThrowLocation throw_location = soa.Self()->GetCurrentLocationForThrow();
- soa.Self()->ThrowNewExceptionF(throw_location, "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);
- mirror::Object* o = soa.Decode<mirror::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