NativeBuffer开发指导 (C/C++)

场景介绍

NativeBuffer模块提供共享内存功能，支持内存的申请、使用、查询和释放等操作。

NativeBuffer的常见开发场景：通过Native API申请OH_NativeBuffer实例，获取内存属性，将ION内存映射到进程空间。

接口说明

接口名	描述
OH_NativeBuffer_Alloc (const OH_NativeBuffer_Config *config)	通过OH_NativeBuffer_Config创建OH_NativeBuffer实例，每次调用都会产生一个新的OH_NativeBuffer实例。本接口需要与OH_NativeBuffer_Unreference接口配合使用，否则会存在内存泄露。
OH_NativeBuffer_Reference (OH_NativeBuffer *buffer)	将OH_NativeBuffer对象的引用计数增加1。
OH_NativeBuffer_Unreference (OH_NativeBuffer *buffer)	将OH_NativeBuffer对象的引用计数减1，当引用计数为0的时候，该NativeBuffer对象会被析构掉。
OH_NativeBuffer_GetConfig (OH_NativeBuffer *buffer, OH_NativeBuffer_Config *config)	用于获取OH_NativeBuffer的属性。
OH_NativeBuffer_Map (OH_NativeBuffer *buffer, void **virAddr)	将OH_NativeBuffer对应的ION内存映射到进程空间。
OH_NativeBuffer_Unmap (OH_NativeBuffer *buffer)	将OH_NativeBuffer对应的ION内存从进程空间移除。
OH_NativeBuffer_GetSeqNum (OH_NativeBuffer *buffer)	获取OH_NativeBuffer的序列号。

详细的接口说明请参考native_buffer。

开发步骤

以下步骤描述了如何使用NativeBuffer提供的Native API接口创建OH_NativeBuffer实例，获取内存属性信息，并将ION内存映射到进程空间。

添加动态链接库

CMakeLists.txt中添加以下lib。

libnative_buffer.so

头文件

#include <native_buffer/native_buffer.h>

1. 创建OH_NativeBuffer实例。

   OH_NativeBuffer_Config config {
       .width = 0x100,
       .height = 0x100,
       .format = NATIVEBUFFER_PIXEL_FMT_RGBA_8888,
       .usage = NATIVEBUFFER_USAGE_CPU_READ | NATIVEBUFFER_USAGE_CPU_WRITE | NATIVEBUFFER_USAGE_MEM_DMA,
   };
   
   OH_NativeBuffer *nativeBuffer = OH_NativeBuffer_Alloc(&config);
   if (nativeBuffer == nullptr) {
       LOGE("OH_NativeBuffer_Alloc fail, nativeBuffer is null");
   }

2. 将OH_NativeBuffer对应的ION内存映射到进程空间。

   应用如需访问buffer内存空间，可通过OH_NativeBuffer_Map接口将ION内存映射到进程空间。

   void* virAddr = nullptr;
   int32_t ret = OH_NativeBuffer_Map(nativeBuffer, &virAddr);
   if (ret != 0) {
       LOGE("OH_NativeBuffer_Map Failed");
   }
   // ...
   ret = OH_NativeBuffer_Unmap(nativeBuffer);
   if (ret != 0) {
       LOGE("OH_NativeBuffer_Unmap Failed");
   }

3. 获取内存的属性信息。

   OH_NativeBuffer_Config config2 = {};
   OH_NativeBuffer_GetConfig(nativeBuffer, &config2);
   uint32_t hwBufferID = OH_NativeBuffer_GetSeqNum(nativeBuffer);

4. 销毁OH_NativeBuffer。

   OH_NativeBuffer_Unreference(nativeBuffer);
   nativeBuffer = nullptr;