Android Ashmem匿名共享内存 C++实例

~/Android/external/ashmem

----common

      ----ISharedBuffer.h

      ----ISharedBuffer.cpp

----server

      ----SharedBufferServer.cpp

      ----Android.mk

----client

      ----SharedBufferClient.cpp

      ----Android.mk

common/ISharedBuffer.h

#ifndef ISHAREDBUFFER_H_
#define ISHAREDBUFFER_H_

#include <utils/RefBase.h>
#include <binder/IInterface.h>
#include <binder/Parcel.h>

#define SHARED_BUFFER_SERVICE "shy.luo.SharedBuffer"
#define SHARED_BUFFER_SIZE 4
#define LOGD ALOGD
#define LOGE ALOGE
#define LOGI ALOGI
#define LOGW ALOGW

using namespace android;

class ISharedBuffer: public IInterface
{
public:
DECLARE_META_INTERFACE(SharedBuffer);
virtual sp<IMemory> getBuffer() = 0;

};

class BnSharedBuffer: public BnInterface<ISharedBuffer>
{
public:
virtual status_t onTransact (uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags = 0);
};
#endif

common/ISharedBuffer.cpp

#define LOG_TAG "ISharedBuffer"

#include <utils/Log.h>
#include <binder/MemoryBase.h>

#include "ISharedBuffer.h"

using namespace android;

enum
{
GET_BUFFER = IBinder::FIRST_CALL_TRANSACTION
};

class BpSharedBuffer: public BpInterface<ISharedBuffer>
{
public:
BpSharedBuffer(const sp<IBinder>& impl)
: BpInterface<ISharedBuffer>(impl)
{
}

sp<IMemory> getBuffer()
{
Parcel data;
data.writeInterfaceToken(ISharedBuffer::getInterfaceDescriptor());

Parcel reply;
remote()->transact(GET_BUFFER, data, &reply);

sp<IMemory> buffer = interface_cast<IMemory> (reply.readStrongBinder());

return buffer;
}
};

IMPLEMENT_META_INTERFACE(SharedBuffer, "shy.luo.ISharedBuffer");

status_t BnSharedBuffer::onTransact(uint32_t code, const Parcel & data, Parcel * reply, uint32_t flags)
{
switch(code)
{
case GET_BUFFER:
{
CHECK_INTERFACE(ISharedBuffer, data, reply);

sp<IMemory> buffer = getBuffer();
if(buffer != NULL)
{
reply->writeStrongBinder(buffer->asBinder(buffer));
}

return NO_ERROR;
}
default:
{
return BBinder::onTransact( code, data, reply, flags);
}
}
}

server/Android.mk

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE_TAGS := optional
LOCAL_SRC_FILES := ../common/ISharedBuffer.cpp \
SharedBufferServer.cpp
LOCAL_SHARED_LIBRARIES := libcutils libutils libbinder
LOCAL_MODULE := SharedBufferServer
include $(BUILD_EXECUTABLE)

server/SharedBufferServer.cpp

#define LOG_TAG "ISharedBufferServer"
#define TAG "[Server] "

#include <stdlib.h>
#include <fcntl.h>
#include <utils/Log.h>
#include <binder/MemoryBase.h>
#include <binder/MemoryHeapBase.h>
#include <binder/IServiceManager.h>
#include <binder/IPCThreadState.h>

#include "../common/ISharedBuffer.h"

class SharedBufferService : public BnSharedBuffer
{
public:
SharedBufferService ()
{
sp<MemoryHeapBase> heap = new MemoryHeapBase(SHARED_BUFFER_SIZE, 0, "SharedBuffer");
if(heap != NULL)
{
mMemory = new MemoryBase(heap, 0, SHARED_BUFFER_SIZE);

int32_t* data = (int32_t*)mMemory->pointer();
if(data != NULL)
{
*data = 0;
}
}
}

virtual ~SharedBufferService ()
{
mMemory = NULL;
}

public:
static void instantiate ()
{
defaultServiceManager ()->addService(String16(SHARED_BUFFER_SERVICE), new SharedBufferService());
}

virtual sp<IMemory> getBuffer()
{
return mMemory;
}

private:
sp<MemoryBase> mMemory;
};

int main(int argc, char** argv)
{
SharedBufferService::instantiate();

ProcessState::self()->startThreadPool();
IPCThreadState::self()->joinThreadPool();

return 0;
}

client/Android.mk

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE_TAGS := optional
LOCAL_SRC_FILES := ../common/ISharedBuffer.cpp \
SharedBufferClient.cpp
LOCAL_SHARED_LIBRARIES := libcutils libutils libbinder
LOCAL_MODULE := SharedBufferClient
include $(BUILD_EXECUTABLE)

client/SharedBufferClient.cpp

#define LOG_TAG "SharedBufferClient"

#include <utils/Log.h>
#include <binder/MemoryBase.h>
#include <binder/IServiceManager.h>
#include "../common/ISharedBuffer.h"

int main()
{
sp<IBinder> binder = defaultServiceManager()->getService(String16(SHARED_BUFFER_SERVICE));
if(binder == NULL){
printf("Failed to get service: %s.\n", SHARED_BUFFER_SERVICE);
return -1;
}

sp<ISharedBuffer> service = ISharedBuffer::asInterface(binder);
if(service == NULL){
return -2;
}

sp<IMemory> buffer = service->getBuffer();
if(buffer == NULL){
return -3;
}

int32_t* data = (int32_t*)buffer->pointer();
if(data == NULL){
return -4;
}

printf("The value of the shared buffer is %d. \n", *data);

*data = *data + 1;

printf("Add value 1 to the shared buffer. \n");

return 0;
}

运行结果：