blob: 42bae22c4072f315232f97dd9612463299d9e091 [file] [log] [blame]
/*
* 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((((uintptr_t) dst | (uintptr_t) src | n) & 0x01) == 0);
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((((uintptr_t) dst | (uintptr_t) src | n) & 0x03) == 0);
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 {
namespace {
void ThrowArrayStoreException_NotAnArray(const char* identifier, Object* array) {
std::string actualType(PrettyTypeOf(array));
Thread::Current()->ThrowNewException("Ljava/lang/ArrayStoreException;", "%s is not an array: %s", identifier, actualType.c_str());
}
void System_arraycopy(JNIEnv* env, jclass, jobject javaSrc, jint srcPos, jobject javaDst, jint dstPos, jint length) {
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("src", srcObject);
return;
}
if (!dstObject->IsArrayInstance()) {
ThrowArrayStoreException_NotAnArray("dst", 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->ThrowNewException("Ljava/lang/ArrayIndexOutOfBoundsException;",
"src.length=%d srcPos=%d dst.length=%d dstPos=%d length=%d",
srcArray->GetLength(), srcPos, dstArray->GetLength(), dstPos, length);
return;
}
uint8_t* dstBytes = reinterpret_cast<uint8_t*>(dstArray->GetRawData());
const uint8_t* srcBytes = reinterpret_cast<const uint8_t*>(srcArray->GetRawData());
// 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->ThrowNewException("Ljava/lang/ArrayStoreException;",
"Incompatible types: src=%s, dst=%s", srcType.c_str(), dstType.c_str());
return;
}
switch (srcArray->GetClass()->GetComponentSize()) {
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*);
if (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);
Heap::WriteBarrier(dstArray);
return;
}
// The arrays are not trivially compatible. However, we
// may still be able to do this if the destination object is
// compatible (e.g. copy Object[] to String[], but the Object
// being copied is actually a String). We need to copy elements
// one by one until something goes wrong.
//
// Because of overlapping moves, what we really want to do
// is compare the types and count up how many we can move,
// then call move32() to shift the actual data. If we just
// start from the front we could do a smear rather than a move.
// TODO: this idea is flawed. a malicious caller could exploit the check-use
// race by modifying the source array after we check but before we copy,
// and cause us to copy incompatible elements.
Object* const * srcObj = reinterpret_cast<Object* const *>(srcBytes + srcPos * width);
Class* dstClass = dstArray->GetClass()->GetComponentType();
Class* initialElementClass = NULL;
if (length > 0 && srcObj[0] != NULL) {
initialElementClass = srcObj[0]->GetClass();
if (!dstClass->IsAssignableFrom(initialElementClass)) {
initialElementClass = NULL;
}
}
int copyCount;
for (copyCount = 0; copyCount < length; copyCount++) {
if (srcObj[copyCount] != NULL && srcObj[copyCount]->GetClass() != initialElementClass && !dstClass->IsAssignableFrom(srcObj[copyCount]->GetClass())) {
// Can't put this element into the array.
// We'll copy up to this point, then throw.
break;
}
}
move32(dstBytes + dstPos * width, srcBytes + srcPos * width, copyCount * width);
Heap::WriteBarrier(dstArray);
if (copyCount != length) {
std::string actualSrcType(PrettyTypeOf(srcObj[copyCount]));
std::string dstType(PrettyTypeOf(dstArray));
self->ThrowNewException("Ljava/lang/ArrayStoreException;",
"source[%d] of type %s cannot be stored in destination array of type %s",
srcPos + copyCount, actualSrcType.c_str(), dstType.c_str());
return;
}
}
jint System_identityHashCode(JNIEnv* env, jclass, jobject javaObject) {
Object* o = Decode<Object*>(env, javaObject);
return static_cast<jint>(reinterpret_cast<uintptr_t>(o));
}
JNINativeMethod gMethods[] = {
NATIVE_METHOD(System, arraycopy, "(Ljava/lang/Object;ILjava/lang/Object;II)V"),
NATIVE_METHOD(System, identityHashCode, "(Ljava/lang/Object;)I"),
};
} // namespace
void register_java_lang_System(JNIEnv* env) {
jniRegisterNativeMethods(env, "java/lang/System", gMethods, NELEM(gMethods));
}
} // namespace art