Android(安卓)Parcel机制

一．先从Serialize说起
   我们都知道JAVA中的Serialize机制，译成串行化、序列化……，其作用是能将数据对象存入字节流当中，在需要时重新生成对象。主要应用是利用外部存储设备保存对象状态，以及通过网络传输对象等。

   二．Android中的新的序列化机制
   在Android系统中，定位为针对内存受限的设备，因此对性能要求更高，另外系统中采用了新的IPC（进程间通信）机制，必然要求使用性能更出色的对象传输方式。在这样的环境下，Parcel被设计出来，其定位就是轻量级的高效的对象序列化和反序列化机制。

   三．Parcel类的背后
   在Framework中有parcel类，源码路径是：Frameworks/base/core/java/android/os/Parcel.java
   典型的源码片断如下：

java代码：

/**
* Write an integer value into the parcel at the current dataPosition(),
* growing dataCapacity() if needed.
*/
public final native void writeInt(int val);
/**
* Write a long integer value into the parcel at the current dataPosition(),
* growing dataCapacity() if needed.
*/
public final native void writeLong(long val);

复制代码
从中我们看到，从这个源程序文件中我们看不到真正的功能是如何实现的，必须透过JNI往下走了。于是，Frameworks/base/core/jni/android_util_Binder.cpp中找到了线索

java代码：

static void android_os_Parcel_writeInt(JNIEnv* env, jobject clazz, jint val)
{
Parcel* parcel = parcelForJavaObject(env, clazz);
if (parcel != NULL) {
const status_t err = parcel->writeInt32(val);
if (err != NO_ERROR) {
jniThrowException(env, “java/lang/OutOfMemoryError”, NULL);
}
}
}
static void android_os_Parcel_writeLong(JNIEnv* env, jobject clazz, jlong val)
{
Parcel* parcel = parcelForJavaObject(env, clazz);
if (parcel != NULL) {
const status_t err = parcel->writeInt64(val);
if (err != NO_ERROR) {
jniThrowException(env, “java/lang/OutOfMemoryError”, NULL);
}
}
}

复制代码
   从这里我们可以得到的信息是函数的实现依赖于Parcel指针，因此还需要找到Parcel的类定义，注意，这里的类已经是用C++语言实现的了。

   找到Frameworks/base/include/binder/parcel.h和Frameworks/base/libs/binder/parcel.cpp。终于找到了最终的实现代码了。

   有兴趣的朋友可以自己读一下，不难理解，这里把基本的思路总结一下：

   1. 整个读写全是在内存中进行，主要是通过malloc()、realloc()、memcpy()等内存操作进行，所以效率比JAVA序列化中使用外部存储器会高很多；
   2. 读写时是4字节对齐的，可以看到#define PAD_SIZE(s) (((s)+3)&~3)这句宏定义就是在做这件事情；
   3. 如果预分配的空间不够时newSize = ((mDataSize+len)*3)/2;会一次多分配50%；
   4. 对于普通数据，使用的是mData内存地址，对于IBinder类型的数据以及FileDescriptor使用的是mObjects内存地址。后者是通过flatten_binder()和unflatten_binder()实现的，目的是反序列化时读出的对象就是原对象而不用重新new一个新对象。

java代码：

/*
* Copyright (C) 2005 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.
*/
#ifndef ANDROID_PARCEL_H
#define ANDROID_PARCEL_H
#include
#include
#include
#include
#include
// —————————————————————————
namespace android {
class IBinder;
class ProcessState;
class String8;
class TextOutput;
class Flattenable;
struct flat_binder_object; // defined in support_p/binder_module.h
class Parcel
{
public:
Parcel();
~Parcel();
const uint8_t* data() const;
size_t dataSize() const;
size_t dataAvail() const;
size_t dataPosition() const;
size_t dataCapacity() const;
status_t setDataSize(size_t size);
void setDataPosition(size_t pos) const;
status_t setDataCapacity(size_t size);
status_t setData(const uint8_t* buffer, size_t len);
status_t appendFrom(Parcel *parcel, size_t start, size_t len);
bool hasFileDescriptors() const;

复制代码java代码：

status_t writeInterfaceToken(const String16& interface);
bool enforceInterface(const String16& interface) const;
bool checkInterface(IBinder*) const;
void freeData();
const size_t* objects() const;
size_t objectsCount() const;
status_t errorCheck() const;
void setError(status_t err);
status_t write(const void* data, size_t len);
void* writeInplace(size_t len);
status_t writeUnpadded(const void* data, size_t len);
status_t writeInt32(int32_t val);
status_t writeInt64(int64_t val);
status_t writeFloat(float val);
status_t writeDouble(double val);
status_t writeIntPtr(intptr_t val);
status_t writeCString(const char* str);
status_t writeString8(const String8& str);
status_t writeString16(const String16& str);
status_t writeString16(const char16_t* str, size_t len);
status_t writeStrongBinder(const sp& val);
status_t writeWeakBinder(const wp& val);
status_t write(const Flattenable& val);
// Place a native_handle into the parcel (the native_handle’s file-
// descriptors are dup’ed, so it is safe to delete the native_handle
// when this function returns).
// Doesn’t take ownership of the native_handle.
status_t writeNativeHandle(const native_handle* handle);
// Place a file descriptor into the parcel. The given fd must remain
// valid for the lifetime of the parcel.
status_t writeFileDescriptor(int fd);
// Place a file descriptor into the parcel. A dup of the fd is made, which
// will be closed once the parcel is destroyed.
status_t writeDupFileDescriptor(int fd);
status_t writeObject(const flat_binder_object& val, bool nullMetaData);
void remove(size_t start, size_t amt);
status_t read(void* outData, size_t len) const;
const void* readInplace(size_t len) const;
int32_t readInt32() const;
status_t readInt32(int32_t *pArg) const;
int64_t readInt64() const;
status_t readInt64(int64_t *pArg) const;
float readFloat() const;
status_t readFloat(float *pArg) const;
double readDouble() const;
status_t readDouble(double *pArg) const;
intptr_t readIntPtr() const;
status_t readIntPtr(intptr_t *pArg) const;
const char* readCString() const;
String8 readString8() const;
String16 readString16() const;
const char16_t* readString16Inplace(size_t* outLen) const;
sp readStrongBinder() const;
wp readWeakBinder() const;
status_t read(Flattenable& val) const;
// Retrieve native_handle from the parcel. This returns a copy of the
// parcel’s native_handle (the caller takes ownership). The caller
// must free the native_handle with native_handle_close() and
// native_handle_delete().
native_handle* readNativeHandle() const;
// Retrieve a file descriptor from the parcel. This returns the raw fd
// in the parcel, which you do not own — use dup() to get your own copy.
int readFileDescriptor() const;
const flat_binder_object* readObject(bool nullMetaData) const;
// Explicitly close all file descriptors in the parcel.
void closeFileDescriptors();
typedef void (*release_func)(Parcel* parcel,
const uint8_t* data, size_t dataSize,
const size_t* objects, size_t objectsSize,
void* cookie);
const uint8_t* ipcData() const;
size_t ipcDataSize() const;
const size_t* ipcObjects() const;
size_t ipcObjectsCount() const;
void ipcSetDataReference(const uint8_t* data, size_t dataSize,
const size_t* objects, size_t objectsCount,
release_func relFunc, void* relCookie);
void print(TextOutput& to, uint32_t flags = 0) const;
private:
Parcel(const Parcel& o);
Parcel& operator=(const Parcel& o);
status_t finishWrite(size_t len);
void releaseObjects();
void acquireObjects();
status_t growData(size_t len);
status_t restartWrite(size_t desired);
status_t continueWrite(size_t desired);
void freeDataNoInit();
void initState();
void scanForFds() const;
template
status_t readAligned(T *pArg) const;
template T readAligned() const;
template
status_t writeAligned(T val);
status_t mError;
uint8_t* mData;
size_t mDataSize;
size_t mDataCapacity;
mutable size_t mDataPos;
size_t* mObjects;
size_t mObjectsSize;
size_t mObjectsCapacity;
mutable size_t mNextObjectHint;
mutable bool mFdsKnown;
mutable bool mHasFds;
release_func mOwner;
void* mOwnerCookie;
};

复制代码java代码：

// —————————————————————————
inline TextOutput& operator<<(TextOutput& to, const Parcel& parcel)
{
parcel.print(to);
return to;
}
// ---------------------------------------------------------------------------
// Generic acquire and release of objects.
void acquire_object(const sp& proc,
const flat_binder_object& obj, const void* who);
void release_object(const sp& proc,
const flat_binder_object& obj, const void* who);
void flatten_binder(const sp& proc,
const sp& binder, flat_binder_object* out);
void flatten_binder(const sp& proc,
const wp& binder, flat_binder_object* out);
status_t unflatten_binder(const sp& proc,
const flat_binder_object& flat, sp* out);
status_t unflatten_binder(const sp& proc,
const flat_binder_object& flat, wp* out);
}; // namespace android
// —————————————————————————
#endif // ANDROID_PARCEL_H
view plain
/*
* Copyright (C) 2005 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.
*/
#define LOG_TAG “Parcel”
//#define LOG_NDEBUG 0
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#ifndef INT32_MAX
#define INT32_MAX ((int32_t)(2147483647))
#endif
#define LOG_REFS(…)
//#define LOG_REFS(…) LOG(LOG_DEBUG, “Parcel”, __VA_ARGS__)
// —————————————————————————
#define PAD_SIZE(s) (((s)+3)&~3)
// XXX This can be made public if we want to provide
// support for typed data.
struct small_flat_data
{
uint32_t type;
uint32_t data;
};
namespace android {
void acquire_object(const sp& proc,
const flat_binder_object& obj, const void* who)
{
switch (obj.type) {
case BINDER_TYPE_BINDER:
if (obj.binder) {
LOG_REFS(“Parcel %p acquiring reference on local %p”, who, obj.cookie);
static_cast(obj.cookie)->incStrong(who);
}
return;
case BINDER_TYPE_WEAK_BINDER:
if (obj.binder)
static_cast(obj.binder)->incWeak(who);
return;
case BINDER_TYPE_HANDLE: {
const sp b = proc->getStrongProxyForHandle(obj.handle);
if (b != NULL) {
LOG_REFS(“Parcel %p acquiring reference on remote %p”, who, b.get());
b->incStrong(who);
}
return;
}
case BINDER_TYPE_WEAK_HANDLE: {
const wp b = proc->getWeakProxyForHandle(obj.handle);
if (b != NULL) b.get_refs()->incWeak(who);
return;
}
case BINDER_TYPE_FD: {
// intentionally blank — nothing to do to acquire this, but we do
// recognize it as a legitimate object type.
return;
}
}
LOGD(“Invalid object type 0x%08lx”, obj.type);
}
void release_object(const sp& proc,
const flat_binder_object& obj, const void* who)
{
switch (obj.type) {
case BINDER_TYPE_BINDER:
if (obj.binder) {
LOG_REFS(“Parcel %p releasing reference on local %p”, who, obj.cookie);
static_cast(obj.cookie)->decStrong(who);
}
return;
case BINDER_TYPE_WEAK_BINDER:
if (obj.binder)
static_cast(obj.binder)->decWeak(who);
return;
case BINDER_TYPE_HANDLE: {
const sp b = proc->getStrongProxyForHandle(obj.handle);
if (b != NULL) {
LOG_REFS(“Parcel %p releasing reference on remote %p”, who, b.get());
b->decStrong(who);
}
return;
}
case BINDER_TYPE_WEAK_HANDLE: {
const wp b = proc->getWeakProxyForHandle(obj.handle);
if (b != NULL) b.get_refs()->decWeak(who);
return;
}
case BINDER_TYPE_FD: {
if (obj.cookie != (void*)0) close(obj.handle);
return;
}
}
LOGE(“Invalid object type 0x%08lx”, obj.type);
}
inline static status_t finish_flatten_binder(
const sp& binder, const flat_binder_object& flat, Parcel* out)
{
return out->writeObject(flat, false);
}
status_t flatten_binder(const sp& proc,
const sp& binder, Parcel* out)
{
flat_binder_object obj;
obj.flags = 0x7f | FLAT_BINDER_FLAG_ACCEPTS_FDS;
if (binder != NULL) {
IBinder *local = binder->localBinder();
if (!local) {
BpBinder *proxy = binder->remoteBinder();
if (proxy == NULL) {
LOGE(“null proxy”);
}
const int32_t handle = proxy ? proxy->handle() : 0;
obj.type = BINDER_TYPE_HANDLE;
obj.handle = handle;
obj.cookie = NULL;
} else {
obj.type = BINDER_TYPE_BINDER;
obj.binder = local->getWeakRefs();
obj.cookie = local;
}
} else {
obj.type = BINDER_TYPE_BINDER;
obj.binder = NULL;
obj.cookie = NULL;
}
return finish_flatten_binder(binder, obj, out);
}
status_t flatten_binder(const sp& proc,
const wp& binder, Parcel* out)
{
flat_binder_object obj;
obj.flags = 0x7f | FLAT_BINDER_FLAG_ACCEPTS_FDS;
if (binder != NULL) {
sp real = binder.promote();
if (real != NULL) {
IBinder *local = real->localBinder();
if (!local) {
BpBinder *proxy = real->remoteBinder();
if (proxy == NULL) {
LOGE(“null proxy”);
}
const int32_t handle = proxy ? proxy->handle() : 0;
obj.type = BINDER_TYPE_WEAK_HANDLE;
obj.handle = handle;
obj.cookie = NULL;
} else {
obj.type = BINDER_TYPE_WEAK_BINDER;
obj.binder = binder.get_refs();
obj.cookie = binder.unsafe_get();
}
return finish_flatten_binder(real, obj, out);
}

复制代码java代码：

// XXX How to deal? In order to flatten the given binder,
// we need to probe it for information, which requires a primary
// reference… but we don’t have one.
//
// The OpenBinder implementation uses a dynamic_cast<> here,
// but we can’t do that with the different reference counting
// implementation we are using.
LOGE(“Unable to unflatten Binder weak reference!”);
obj.type = BINDER_TYPE_BINDER;
obj.binder = NULL;
obj.cookie = NULL;
return finish_flatten_binder(NULL, obj, out);
} else {
obj.type = BINDER_TYPE_BINDER;
obj.binder = NULL;
obj.cookie = NULL;
return finish_flatten_binder(NULL, obj, out);
}
}
inline static status_t finish_unflatten_binder(
BpBinder* proxy, const flat_binder_object& flat, const Parcel& in)
{
return NO_ERROR;
}
status_t unflatten_binder(const sp& proc,
const Parcel& in, sp* out)
{
const flat_binder_object* flat = in.readObject(false);
if (flat) {
switch (flat->type) {
case BINDER_TYPE_BINDER:
*out = static_cast(flat->cookie);
return finish_unflatten_binder(NULL, *flat, in);
case BINDER_TYPE_HANDLE:
*out = proc->getStrongProxyForHandle(flat->handle);
return finish_unflatten_binder(
static_cast(out->get()), *flat, in);
}
}
return BAD_TYPE;
}
status_t unflatten_binder(const sp& proc,
const Parcel& in, wp* out)
{
const flat_binder_object* flat = in.readObject(false);
if (flat) {
switch (flat->type) {
case BINDER_TYPE_BINDER:
*out = static_cast(flat->cookie);
return finish_unflatten_binder(NULL, *flat, in);
case BINDER_TYPE_WEAK_BINDER:
if (flat->binder != NULL) {
out->set_object_and_refs(
static_cast(flat->cookie),
static_cast(flat->binder));
} else {
*out = NULL;
}
return finish_unflatten_binder(NULL, *flat, in);
case BINDER_TYPE_HANDLE:
case BINDER_TYPE_WEAK_HANDLE:
*out = proc->getWeakProxyForHandle(flat->handle);
return finish_unflatten_binder(
static_cast(out->unsafe_get()), *flat, in);
}
}
return BAD_TYPE;
}
// —————————————————————————
Parcel::Parcel()
{
initState();
}
Parcel::~Parcel()
{
freeDataNoInit();
}
const uint8_t* Parcel::data() const
{
return mData;
}
size_t Parcel::dataSize() const
{
return (mDataSize > mDataPos ? mDataSize : mDataPos);
}
size_t Parcel::dataAvail() const
{
// TODO: decide what to do about the possibility that this can
// report an available-data size that exceeds a Java int’s max
// positive value, causing havoc. Fortunately this will only
// happen if someone constructs a Parcel containing more than two
// gigabytes of data, which on typical phone hardware is simply
// not possible.
return dataSize() – dataPosition();
}
size_t Parcel::dataPosition() const
{
return mDataPos;
}
size_t Parcel::dataCapacity() const
{
return mDataCapacity;
}
status_t Parcel::setDataSize(size_t size)
{
status_t err;
err = continueWrite(size);
if (err == NO_ERROR) {
mDataSize = size;
LOGV(“setDataSize Setting data size of %p to %d/n”, this, mDataSize);
}
return err;
}
void Parcel::setDataPosition(size_t pos) const
{
mDataPos = pos;
mNextObjectHint = 0;
}
status_t Parcel::setDataCapacity(size_t size)
{
if (size > mDataSize) return continueWrite(size);
return NO_ERROR;
}
status_t Parcel::setData(const uint8_t* buffer, size_t len)
{
status_t err = restartWrite(len);
if (err == NO_ERROR) {
memcpy(const_cast(data()), buffer, len);
mDataSize = len;
mFdsKnown = false;
}
return err;
}
status_t Parcel::appendFrom(Parcel *parcel, size_t offset, size_t len)
{
const sp proc(ProcessState::self());
status_t err;
uint8_t *data = parcel->mData;
size_t *objects = parcel->mObjects;
size_t size = parcel->mObjectsSize;
int startPos = mDataPos;
int firstIndex = -1, lastIndex = -2;
if (len == 0) {
return NO_ERROR;
}
// range checks against the source parcel size
if ((offset > parcel->mDataSize)
|| (len > parcel->mDataSize)
|| (offset + len > parcel->mDataSize)) {
return BAD_VALUE;
}

复制代码java代码：

// Count objects in range
for (int i = 0; i < (int) size; i++) {
size_t off = objects[i];
if ((off >= offset) && (off < offset + len)) {
if (firstIndex == -1) {
firstIndex = i;
}
lastIndex = i;
}
}
int numObjects = lastIndex - firstIndex + 1;
// grow data
err = growData(len);
if (err != NO_ERROR) {
return err;
}
// append data
memcpy(mData + mDataPos, data + offset, len);
mDataPos += len;
mDataSize += len;
if (numObjects > 0) {
// grow objects
if (mObjectsCapacity < mObjectsSize + numObjects) {
int newSize = ((mObjectsSize + numObjects)*3)/2;
size_t *objects =
(size_t*)realloc(mObjects, newSize*sizeof(size_t));
if (objects == (size_t*)0) {
return NO_MEMORY;
}
mObjects = objects;
mObjectsCapacity = newSize;
}
// append and acquire objects
int idx = mObjectsSize;
for (int i = firstIndex; i <= lastIndex; i++) {
size_t off = objects[i] - offset + startPos;
mObjects[idx++] = off;
mObjectsSize++;
flat_binder_object* flat
= reinterpret_cast(mData + off);
acquire_object(proc, *flat, this);
if (flat->type == BINDER_TYPE_FD) {
// If this is a file descriptor, we need to dup it so the
// new Parcel now owns its own fd, and can declare that we
// officially know we have fds.
flat->handle = dup(flat->handle);
flat->cookie = (void*)1;
mHasFds = mFdsKnown = true;
}
}
}
return NO_ERROR;
}
bool Parcel::hasFileDescriptors() const
{
if (!mFdsKnown) {
scanForFds();
}
return mHasFds;
}
status_t Parcel::writeInterfaceToken(const String16& interface)
{
// currently the interface identification token is just its name as a string
return writeString16(interface);
}
bool Parcel::checkInterface(IBinder* binder) const
{
return enforceInterface(binder->getInterfaceDescriptor());
}
bool Parcel::enforceInterface(const String16& interface) const
{
const String16 str(readString16());
if (str == interface) {
return true;
} else {
LOGW(“**** enforceInterface() expected ‘%s’ but read ‘%s’/n”,
String8(interface).string(), String8(str).string());
return false;
}
}
const size_t* Parcel::objects() const
{
return mObjects;
}
size_t Parcel::objectsCount() const
{
return mObjectsSize;
}
status_t Parcel::errorCheck() const
{
return mError;
}
void Parcel::setError(status_t err)
{
mError = err;
}
status_t Parcel::finishWrite(size_t len)
{
//printf(“Finish write of %d/n”, len);
mDataPos += len;
LOGV(“finishWrite Setting data pos of %p to %d/n”, this, mDataPos);
if (mDataPos > mDataSize) {
mDataSize = mDataPos;
LOGV(“finishWrite Setting data size of %p to %d/n”, this, mDataSize);
}
//printf(“New pos=%d, size=%d/n”, mDataPos, mDataSize);
return NO_ERROR;
}
status_t Parcel::writeUnpadded(const void* data, size_t len)
{
size_t end = mDataPos + len;
if (end < mDataPos) {
// integer overflow
return BAD_VALUE;
}
if (end <= mDataCapacity) {
restart_write:
memcpy(mData+mDataPos, data, len);
return finishWrite(len);
}
status_t err = growData(len);
if (err == NO_ERROR) goto restart_write;
return err;
}
status_t Parcel::write(const void* data, size_t len)
{
void* const d = writeInplace(len);
if (d) {
memcpy(d, data, len);
return NO_ERROR;
}
return mError;
}
void* Parcel::writeInplace(size_t len)
{
const size_t padded = PAD_SIZE(len);
// sanity check for integer overflow
if (mDataPos+padded < mDataPos) {
return NULL;
}
if ((mDataPos+padded) <= mDataCapacity) {
restart_write:
//printf("Writing %ld bytes, padded to %ld/n", len, padded);
uint8_t* const data = mData+mDataPos;
// Need to pad at end?
if (padded != len) {
#if BYTE_ORDER == BIG_ENDIAN
static const uint32_t mask[4] = {
0x00000000, 0xffffff00, 0xffff0000, 0xff000000
};
#endif
#if BYTE_ORDER == LITTLE_ENDIAN
static const uint32_t mask[4] = {
0x00000000, 0x00ffffff, 0x0000ffff, 0x000000ff
};
#endif
//printf("Applying pad mask: %p to %p/n", (void*)mask[padded-len],
// *reinterpret_cast(data+padded-4));
*reinterpret_cast(data+padded-4) &= mask[padded-len];
}

复制代码java代码：

finishWrite(padded);
return data;
}
status_t err = growData(padded);
if (err == NO_ERROR) goto restart_write;
return NULL;
}
status_t Parcel::writeInt32(int32_t val)
{
return writeAligned(val);
}
status_t Parcel::writeInt64(int64_t val)
{
return writeAligned(val);
}
status_t Parcel::writeFloat(float val)
{
return writeAligned(val);
}
status_t Parcel::writeDouble(double val)
{
return writeAligned(val);
}
status_t Parcel::writeIntPtr(intptr_t val)
{
return writeAligned(val);
}
status_t Parcel::writeCString(const char* str)
{
return write(str, strlen(str)+1);
}
status_t Parcel::writeString8(const String8& str)
{
status_t err = writeInt32(str.bytes());
if (err == NO_ERROR) {
err = write(str.string(), str.bytes()+1);
}
return err;
}
status_t Parcel::writeString16(const String16& str)
{
return writeString16(str.string(), str.size());
}
status_t Parcel::writeString16(const char16_t* str, size_t len)
{
if (str == NULL) return writeInt32(-1);
status_t err = writeInt32(len);
if (err == NO_ERROR) {
len *= sizeof(char16_t);
uint8_t* data = (uint8_t*)writeInplace(len+sizeof(char16_t));
if (data) {
memcpy(data, str, len);
*reinterpret_cast(data+len) = 0;
return NO_ERROR;
}
err = mError;
}
return err;
}
status_t Parcel::writeStrongBinder(const sp& val)
{
return flatten_binder(ProcessState::self(), val, this);
}
status_t Parcel::writeWeakBinder(const wp& val)
{
return flatten_binder(ProcessState::self(), val, this);
}
status_t Parcel::writeNativeHandle(const native_handle* handle)
{
if (!handle || handle->version != sizeof(native_handle))
return BAD_TYPE;
status_t err;
err = writeInt32(handle->numFds);
if (err != NO_ERROR) return err;
err = writeInt32(handle->numInts);
if (err != NO_ERROR) return err;
for (int i=0 ; err==NO_ERROR && inumFds ; i++)
err = writeDupFileDescriptor(handle->data[i]);
if (err != NO_ERROR) {
LOGD(“write native handle, write dup fd failed”);
return err;
}
err = write(handle->data + handle->numFds, sizeof(int)*handle->numInts);
return err;
}
status_t Parcel::writeFileDescriptor(int fd)
{
flat_binder_object obj;
obj.type = BINDER_TYPE_FD;
obj.flags = 0x7f | FLAT_BINDER_FLAG_ACCEPTS_FDS;
obj.handle = fd;
obj.cookie = (void*)0;
return writeObject(obj, true);
}
status_t Parcel::writeDupFileDescriptor(int fd)
{
flat_binder_object obj;
obj.type = BINDER_TYPE_FD;
obj.flags = 0x7f | FLAT_BINDER_FLAG_ACCEPTS_FDS;
obj.handle = dup(fd);
obj.cookie = (void*)1;
return writeObject(obj, true);
}
status_t Parcel::write(const Flattenable& val)
{
status_t err;
// size if needed
size_t len = val.getFlattenedSize();
size_t fd_count = val.getFdCount();
err = this->writeInt32(len);
if (err) return err;
err = this->writeInt32(fd_count);
if (err) return err;
// payload
void* buf = this->writeInplace(PAD_SIZE(len));
if (buf == NULL)
return BAD_VALUE;
int* fds = NULL;
if (fd_count) {
fds = new int[fd_count];
}
err = val.flatten(buf, len, fds, fd_count);
for (size_t i=0 ; i err = this->writeDupFileDescriptor( fds[i] );
}
if (fd_count) {
delete [] fds;
}
return err;
}
status_t Parcel::writeObject(const flat_binder_object& val, bool nullMetaData)
{
const bool enoughData = (mDataPos+sizeof(val)) <= mDataCapacity;
const bool enoughObjects = mObjectsSize < mObjectsCapacity;
if (enoughData && enoughObjects) {
restart_write:
*reinterpret_cast(mData+mDataPos) = val;
// Need to write meta-data?
if (nullMetaData || val.binder != NULL) {
mObjects[mObjectsSize] = mDataPos;
acquire_object(ProcessState::self(), val, this);
mObjectsSize++;
}
// remember if it’s a file descriptor
if (val.type == BINDER_TYPE_FD) {
mHasFds = mFdsKnown = true;
}
return finishWrite(sizeof(flat_binder_object));
}
if (!enoughData) {
const status_t err = growData(sizeof(val));
if (err != NO_ERROR) return err;
}
if (!enoughObjects) {
size_t newSize = ((mObjectsSize+2)*3)/2;
size_t* objects = (size_t*)realloc(mObjects, newSize*sizeof(size_t));
if (objects == NULL) return NO_MEMORY;
mObjects = objects;
mObjectsCapacity = newSize;
}

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