/vm/native/java_lang_System.cpp
C++ | 373 lines | 227 code | 36 blank | 110 comment | 53 complexity | b5f76e25c71618538e15c3c134a39c91 MD5 | raw file
- /*
- * 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.
- */
- /*
- * java.lang.Class native methods
- */
- #include "Dalvik.h"
- #include "native/InternalNativePriv.h"
- /*
- * The VM makes 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() and memmove()
- * 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 dest/src are aligned
- * appropriately for the element type, and that n is a multiple of the
- * element size.
- */
- #ifdef __BIONIC__
- /* always present in bionic libc */
- #define HAVE_MEMMOVE_WORDS
- #endif
- #ifdef HAVE_MEMMOVE_WORDS
- extern "C" void _memmove_words(void* dest, const void* src, size_t n);
- #define move16 _memmove_words
- #define move32 _memmove_words
- #else
- static void move16(void* dest, const void* src, size_t n)
- {
- assert((((uintptr_t) dest | (uintptr_t) src | n) & 0x01) == 0);
- uint16_t* d = (uint16_t*) dest;
- const uint16_t* s = (uint16_t*) src;
- n /= sizeof(uint16_t);
- if (d < s) {
- /* copy forward */
- while (n--) {
- *d++ = *s++;
- }
- } else {
- /* copy backward */
- d += n;
- s += n;
- while (n--) {
- *--d = *--s;
- }
- }
- }
- static void move32(void* dest, const void* src, size_t n)
- {
- assert((((uintptr_t) dest | (uintptr_t) src | n) & 0x03) == 0);
- uint32_t* d = (uint32_t*) dest;
- const uint32_t* s = (uint32_t*) src;
- n /= sizeof(uint32_t);
- if (d < s) {
- /* copy forward */
- while (n--) {
- *d++ = *s++;
- }
- } else {
- /* copy backward */
- d += n;
- s += n;
- while (n--) {
- *--d = *--s;
- }
- }
- }
- #endif /*HAVE_MEMMOVE_WORDS*/
- /*
- * public static void arraycopy(Object src, int srcPos, Object dest,
- * int destPos, int length)
- *
- * The description of this function is long, and describes a multitude
- * of checks and exceptions.
- */
- static void Dalvik_java_lang_System_arraycopy(const u4* args, JValue* pResult)
- {
- ArrayObject* srcArray = (ArrayObject*) args[0];
- int srcPos = args[1];
- ArrayObject* dstArray = (ArrayObject*) args[2];
- int dstPos = args[3];
- int length = args[4];
- /* Check for null pointers. */
- if (srcArray == NULL) {
- dvmThrowNullPointerException("src == null");
- RETURN_VOID();
- }
- if (dstArray == NULL) {
- dvmThrowNullPointerException("dst == null");
- RETURN_VOID();
- }
- /* Make sure source and destination are arrays. */
- if (!dvmIsArray(srcArray)) {
- dvmThrowArrayStoreExceptionNotArray(((Object*)srcArray)->clazz, "source");
- RETURN_VOID();
- }
- if (!dvmIsArray(dstArray)) {
- dvmThrowArrayStoreExceptionNotArray(((Object*)dstArray)->clazz, "destination");
- RETURN_VOID();
- }
- /* avoid int overflow */
- if (srcPos < 0 || dstPos < 0 || length < 0 ||
- srcPos > (int) srcArray->length - length ||
- dstPos > (int) dstArray->length - length)
- {
- dvmThrowExceptionFmt(gDvm.exArrayIndexOutOfBoundsException,
- "src.length=%d srcPos=%d dst.length=%d dstPos=%d length=%d",
- srcArray->length, srcPos, dstArray->length, dstPos, length);
- RETURN_VOID();
- }
- ClassObject* srcClass = srcArray->clazz;
- ClassObject* dstClass = dstArray->clazz;
- char srcType = srcClass->descriptor[1];
- char dstType = dstClass->descriptor[1];
- /*
- * If one of the arrays holds a primitive type, the other array must
- * hold the same type.
- */
- bool srcPrim = (srcType != '[' && srcType != 'L');
- bool dstPrim = (dstType != '[' && dstType != 'L');
- if (srcPrim || dstPrim) {
- if (srcPrim != dstPrim || srcType != dstType) {
- dvmThrowArrayStoreExceptionIncompatibleArrays(srcClass, dstClass);
- RETURN_VOID();
- }
- if (false) ALOGD("arraycopy prim[%c] dst=%p %d src=%p %d len=%d",
- srcType, dstArray->contents, dstPos,
- srcArray->contents, srcPos, length);
- switch (srcType) {
- case 'B':
- case 'Z':
- /* 1 byte per element */
- memmove((u1*) dstArray->contents + dstPos,
- (const u1*) srcArray->contents + srcPos,
- length);
- break;
- case 'C':
- case 'S':
- /* 2 bytes per element */
- move16((u1*) dstArray->contents + dstPos * 2,
- (const u1*) srcArray->contents + srcPos * 2,
- length * 2);
- break;
- case 'F':
- case 'I':
- /* 4 bytes per element */
- move32((u1*) dstArray->contents + dstPos * 4,
- (const u1*) srcArray->contents + srcPos * 4,
- length * 4);
- break;
- case 'D':
- case 'J':
- /*
- * 8 bytes per element. We don't need to guarantee atomicity
- * of the entire 64-bit word, so we can use the 32-bit copier.
- */
- move32((u1*) dstArray->contents + dstPos * 8,
- (const u1*) srcArray->contents + srcPos * 8,
- length * 8);
- break;
- default: /* illegal array type */
- ALOGE("Weird array type '%s'", srcClass->descriptor);
- dvmAbort();
- }
- } else {
- /*
- * Neither class is primitive. See if elements in "src" are instances
- * of elements in "dst" (e.g. copy String to String or String to
- * Object).
- */
- const int width = sizeof(Object*);
- if (srcClass->arrayDim == dstClass->arrayDim &&
- dvmInstanceof(srcClass, dstClass))
- {
- /*
- * "dst" can hold "src"; copy the whole thing.
- */
- if (false) ALOGD("arraycopy ref dst=%p %d src=%p %d len=%d",
- dstArray->contents, dstPos * width,
- srcArray->contents, srcPos * width,
- length * width);
- move32((u1*)dstArray->contents + dstPos * width,
- (const u1*)srcArray->contents + srcPos * width,
- length * width);
- dvmWriteBarrierArray(dstArray, dstPos, dstPos+length);
- } else {
- /*
- * The arrays are not fundamentally 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.
- */
- Object** srcObj;
- int copyCount;
- ClassObject* clazz = NULL;
- srcObj = ((Object**)(void*)srcArray->contents) + srcPos;
- if (length > 0 && srcObj[0] != NULL)
- {
- clazz = srcObj[0]->clazz;
- if (!dvmCanPutArrayElement(clazz, dstClass))
- clazz = NULL;
- }
- for (copyCount = 0; copyCount < length; copyCount++)
- {
- if (srcObj[copyCount] != NULL &&
- srcObj[copyCount]->clazz != clazz &&
- !dvmCanPutArrayElement(srcObj[copyCount]->clazz, dstClass))
- {
- /* can't put this element into the array */
- break;
- }
- }
- if (false) ALOGD("arraycopy iref dst=%p %d src=%p %d count=%d of %d",
- dstArray->contents, dstPos * width,
- srcArray->contents, srcPos * width,
- copyCount, length);
- move32((u1*)dstArray->contents + dstPos * width,
- (const u1*)srcArray->contents + srcPos * width,
- copyCount * width);
- dvmWriteBarrierArray(dstArray, 0, copyCount);
- if (copyCount != length) {
- dvmThrowArrayStoreExceptionIncompatibleArrayElement(srcPos + copyCount,
- srcObj[copyCount]->clazz, dstClass);
- RETURN_VOID();
- }
- }
- }
- RETURN_VOID();
- }
- /*
- * static long currentTimeMillis()
- *
- * Current time, in miliseconds. This doesn't need to be internal to the
- * VM, but we're already handling java.lang.System here.
- */
- static void Dalvik_java_lang_System_currentTimeMillis(const u4* args,
- JValue* pResult)
- {
- struct timeval tv;
- UNUSED_PARAMETER(args);
- gettimeofday(&tv, (struct timezone *) NULL);
- long long when = tv.tv_sec * 1000LL + tv.tv_usec / 1000;
- RETURN_LONG(when);
- }
- /*
- * static long nanoTime()
- *
- * Current monotonically-increasing time, in nanoseconds. This doesn't
- * need to be internal to the VM, but we're already handling
- * java.lang.System here.
- */
- static void Dalvik_java_lang_System_nanoTime(const u4* args, JValue* pResult)
- {
- UNUSED_PARAMETER(args);
- u8 when = dvmGetRelativeTimeNsec();
- RETURN_LONG(when);
- }
- /*
- * static int identityHashCode(Object x)
- *
- * Returns that hash code that the default hashCode()
- * method would return for "x", even if "x"s class
- * overrides hashCode().
- */
- static void Dalvik_java_lang_System_identityHashCode(const u4* args,
- JValue* pResult)
- {
- Object* thisPtr = (Object*) args[0];
- RETURN_INT(dvmIdentityHashCode(thisPtr));
- }
- static void Dalvik_java_lang_System_mapLibraryName(const u4* args,
- JValue* pResult)
- {
- StringObject* nameObj = (StringObject*) args[0];
- StringObject* result = NULL;
- char* name;
- char* mappedName;
- if (nameObj == NULL) {
- dvmThrowNullPointerException("userLibName == null");
- RETURN_VOID();
- }
- name = dvmCreateCstrFromString(nameObj);
- mappedName = dvmCreateSystemLibraryName(name);
- if (mappedName != NULL) {
- result = dvmCreateStringFromCstr(mappedName);
- dvmReleaseTrackedAlloc((Object*) result, NULL);
- }
- free(name);
- free(mappedName);
- RETURN_PTR(result);
- }
- const DalvikNativeMethod dvm_java_lang_System[] = {
- { "arraycopy", "(Ljava/lang/Object;ILjava/lang/Object;II)V",
- Dalvik_java_lang_System_arraycopy },
- { "currentTimeMillis", "()J",
- Dalvik_java_lang_System_currentTimeMillis },
- { "identityHashCode", "(Ljava/lang/Object;)I",
- Dalvik_java_lang_System_identityHashCode },
- { "mapLibraryName", "(Ljava/lang/String;)Ljava/lang/String;",
- Dalvik_java_lang_System_mapLibraryName },
- { "nanoTime", "()J",
- Dalvik_java_lang_System_nanoTime },
- { NULL, NULL, NULL },
- };