Android SharedMemory 是一种进程间通信(IPC)机制,它允许不同进程访问同一块内存区域。在 Android 中,可以使用 Binder 框架来实现 SharedMemory。以下是如何在 Android 中使用 SharedMemory 读写数据的步骤:
- 创建 SharedMemory 对象:
#include
#include
#include
#include
#include
using namespace android;
status_t createSharedMemory(size_t size, sp *memory) {
sp sm = defaultServiceManager();
const String16 name("MySharedMemory");
return sm->addService(String16(name.string()), new SharedMemoryService(size), true);
}
- 实现 SharedMemoryService 类:
class SharedMemoryService : public BnMemory {
public:
SharedMemoryService(size_t size) : mSize(size) {
mHeap = new MemoryHeapBase(mSize);
}
virtual status_t onTransact(uint32_t code, const Parcel &data, Parcel *reply, uint32_t flags = 0) {
switch (code) {
case GET_SIZE: {
reply->writeInt32(mSize);
return NO_ERROR;
}
case READ_DATA: {
void *buffer = nullptr;
status_t status = mHeap->lock(0, mSize, &buffer, false);
if (status == NO_ERROR) {
memcpy(buffer, mData.get(), mSize);
mHeap->unlock(buffer);
reply->writeInt32(mSize);
} else {
reply->writeInt32(0);
}
return status;
}
case WRITE_DATA: {
void *buffer = nullptr;
status_t status = mHeap->lock(0, mSize, &buffer, true);
if (status == NO_ERROR) {
memcpy(buffer, data.data(), data.size());
mHeap->unlock(buffer);
reply->writeInt32(data.size());
} else {
reply->writeInt32(0);
}
return status;
}
default:
return BBinder::onTransact(code, data, reply, flags);
}
}
private:
size_t mSize;
sp mHeap;
Vector mData;
};
- 在客户端进程中读写 SharedMemory 数据:
#include
#include
#include
#include
#include
using namespace android;
status_t createSharedMemory(size_t size, sp *memory) {
sp sm = defaultServiceManager();
const String16 name("MySharedMemory");
return sm->addService(String16(name.string()), new SharedMemoryService(size), true);
}
void readSharedMemoryData(sp memory) {
void *buffer = nullptr;
status_t status = memory->lock(0, memory->getSize(), &buffer, false);
if (status == NO_ERROR) {
size_t size = memory->getSize();
memcpy(buffer, mData.get(), size);
memory->unlock(buffer);
}
}
void writeSharedMemoryData(sp memory, const uint8_t *data, size_t size) {
void *buffer = nullptr;
status_t status = memory->lock(0, memory->getSize(), &buffer, true);
if (status == NO_ERROR) {
memcpy(buffer, data, size);
memory->unlock(buffer);
}
}
注意:这里的示例代码仅供参考,实际使用时需要根据具体需求进行调整。在实际开发中,还需要考虑内存管理、错误处理等方面的问题。