目录

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的常见应用场景包括：图像数据处理、视频编解码、跨进程内存共享等。开发流程通常包括：申请OH_NativeBuffer实例、获取内存属性和将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，否则会存在内存泄漏。
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内存从进程空间解除映射。
OH_NativeBuffer_GetSeqNum (OH_NativeBuffer *buffer) 获取OH_NativeBuffer的序列号。

详细的接口说明请参考OH_NativeBuffer。

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;