源码
java: https://gitee.com/guangyang1314666/springboot-demo/tree/master/demo-modules/demo-javacpp
c++工程: https://gitee.com/guangyang1314666/javacpp-native-cpp
前言
关于JavaCP
JavaCPP 使得Java 应用可以在高效的访问本地C++方法，JavaCPP底层使用了JNI技术，可以广泛的用在Java SE应用中（也包括安卓），以下两个特性是JavaCPP的关键，稍后咱们会用到：
- 提供一些注解，将Java代码映射为C++代码
- 提供一个jar，用java -jar命令可以将C++代码转为java应用可以访问的动态链接库文件；
- 目前JavaCPP团队已经用JavaCPP为多个著名C++项目生成了完整的接口，这意味着咱们的java应用可以很方便的使用这些C++库
javacpp-1.5.7.jar 下载
github仓库地址: https://github.com/bytedeco/javacpp
maven地址: https://mvnrepository.com/artifact/org.bytedeco/javacpp
我的oss地址: oss://sgy-data-disk/javacpp/c++ 工程结构说明
application: 应用层, 主要用于对moudles层的调用, 形成一个业务逻辑体系
2. build: 存放构建结构
3. cmake: 存放封装的cmake相关工具
4. modules: 存放功能模块, Utils, algo等等
5. samples: 用于存放对modules测试的相关代码, 也可以对application层进行测试
直接生成的是可执行文件用于验证是否符合预期
8. build.sh: 用于构建c++工程脚本, 构建结果放到了build目录下javacpp如何生成的c++文件
javacpp通过InfoMap来定义java和c++的映射关系的, 叫做preset
preset文件放在什么位置?
- 必须放在org.bytedeco.${moduleName}.presets, 包下, 这是javacpp官网的规定
preset文件长什么样?
这里以javacpp_example为例
@Properties(inherit = {javacpp.class},target = "org.bytedeco.javacppexample.jni",global = "org.bytedeco.javacppexample.global.javacpp_example_global",value = {@Platform(// 如果c++中有智能指针等, 必须在这定义宏, 而不是在c++文件中定义, 否则会出现意向不到的事情// 比如编译报错// 如果你在c++文件中定义 #define SHARED_PTR_NAMESPACE std, 那编译也会报错, 因为javacpp将std// 当初了整形变量, 定义在XxxxGolbal中了// 如果你在c++文件中定义#define SHARED_PTR_NAMESPACE, 有可能编译不报错, 但是很有可能出现内存// 泄露或者程序运行一段时间崩溃的问题define = {"SHARED_PTR_NAMESPACE std","UNIQUE_PTR_NAMESPACE std"},value = {"linux-x86","linux-x86_64","macosx-x86_64","windows-x86","windows-x86_64"},include = {"javacpp_example.h"},link = { "javacpp_example"}),@Platform(value = "android", preload = ""),@Platform(value = "ios", preload = {"liblibjpeg", "liblibpng", "liblibprotobuf", "liblibwebp", "libzlib", "libopencv_core"}),@Platform(value = "linux", preloadpath = {"/usr/lib/", "/usr/lib32/", "/usr/lib64/"}),@Platform(value = "linux-armhf", preloadpath = {"/usr/arm-linux-gnueabihf/lib/", "/usr/lib/arm-linux-gnueabihf/"}),@Platform(value = "linux-arm64", preloadpath = {"/usr/aarch64-linux-gnu/lib/", "/usr/lib/aarch64-linux-gnu/"}),@Platform(value = "linux-x86", preloadpath = {"/usr/lib32/", "/usr/lib/"}),@Platform(value = "linux-x86_64", preloadpath = {"/usr/lib64/", "/usr/lib/"})})public class javacpp_example implements InfoMapper {// static { Loader.checkVersion("com.concise", "demo"); }@Overridepublic void map(InfoMap infoMap) {infoMap// .put(new Info("std::shared_ptr<ImageTrans>").valueTypes("ImageTrans"))// 1. 如果std::vector中嵌套 std::vector 或者 std::shared_ptr, 最后一个>前要空一格, 否则底层解析会报错// 错误示范: std::vector<std::shared_ptr<ImageTrans>>// 正确: std::vector<std::shared_ptr<ImageTrans> >// 2. std::vector嵌套std::vector或者std::shared_ptr, 则需要单独put一下new Info,// cppNams = std::shared_ptr<ImageTrans>, pointerTypes指定容器元素类型// 也即是说: javacpp每次只能处理一个嵌套层级std::vector<...> ,我估计内部是通过循环检查来实现的// .put(new Info("std::shared_ptr<ImageBuffer>").pointerTypes("ImageBuffer").define())// 用户传递对象集合数据.put(new Info("std::shared_ptr<ImageBuffer>").annotations("@SharedPtr").valueTypes("@Cast({\"\", \"std::shared_ptr<ImageBuffer>\"}) ImageBuffer").pointerTypes("ImageBuffer"))// .put(new Info("std::shared_ptr<ImageBuffer>&")// .annotations("@UniquePtr", "@Const")// .valueTypes("@Cast({\"\", \"std::shared_ptr<ImageBuffer>&\"}) ImageBuffer")// .pointerTypes("ImageBuffer"))// > > 之间一定要有一个空格, 且要加上.define().put(new Info("std::vector<std::shared_ptr<ImageBuffer> >").pointerTypes("ImageBufferVector").define())// 用于传递字符串集合数据.put(new Info("std::vector<std::string>").pointerTypes("StringVector").define())// .put(new Info("JavaCppExample::getImageData").javaText(// "public native @ByVal ImageBuffer getImageData();"))// java methods, 用于java和c++互相回调.put(new Info("JavaCppExample::callback1").javaText("@Virtual public native void callback1(@Cast(\"uint8_t*\") BytePointer img, int length);")).put(new Info("JavaCppExample::callback2").javaText("@Virtual public native void callback2(@SharedPtr @Cast({\"\", \"std::shared_ptr<ImageBuffer>\"}) ImageBuffer data);"));}}
动态库加载方式
当我们调用jni接口的时候, 会自动调用
Loader.load(), 内部会通过返回获取到类上@Properties注解指定的preset类@NoOffset @Properties(inherit = org.bytedeco.javacppexample.presets.image_buffer.class) public class ImageBuffer extends Pointer { static { Loader.load(); } // ... }
而javacpp会获取到image_buffer类上的@Properties注解数据, 并从中获取需要加载的动态库, 即如下注解的links属性, 如果指定了多个动态库, 那都将被加，所以, 如果你希望在加载一个类动态库的时候不希望加载另一个类动态库, 那必须单独写一个preset类, 并指定相应的动态库 (动态库分开)
@Properties(
inherit = {javacpp.class},
target = "org.bytedeco.javacppexample.jni",
global = "org.bytedeco.javacppexample.global.image_buffer_global",
value = {
@Platform(
// 如果c++中有智能指针等, 必须在这定义宏, 而不是在c++文件中定义, 否则会出现意向不到的事情
// 比如编译报错
// 如果你在c++文件中定义 #define SHARED_PTR_NAMESPACE std, 那编译也会报错, 因为javacpp将std
// 当初了整形变量, 定义在XxxxGolbal中了
// 如果你在c++文件中定义#define SHARED_PTR_NAMESPACE, 有可能编译不报错, 但是很有可能出现内存
// 泄露或者程序运行一段时间崩溃的问题
define = {
"SHARED_PTR_NAMESPACE std",
"UNIQUE_PTR_NAMESPACE std"
},
value = {
"linux-x86",
"linux-x86_64",
"macosx-x86_64",
"windows-x86",
"windows-x86_64"
},
include = {"image_buffer.h"},
link = {"jni_utils" }
),
@Platform(value = "android", preload = ""),
@Platform(value = "ios", preload = {"liblibjpeg", "liblibpng", "liblibprotobuf", "liblibwebp", "libzlib", "libopencv_core"}),
@Platform(value = "linux", preloadpath = {"/usr/lib/", "/usr/lib32/", "/usr/lib64/"}),
@Platform(value = "linux-armhf", preloadpath = {"/usr/arm-linux-gnueabihf/lib/", "/usr/lib/arm-linux-gnueabihf/"}),
@Platform(value = "linux-arm64", preloadpath = {"/usr/aarch64-linux-gnu/lib/", "/usr/lib/aarch64-linux-gnu/"}),
@Platform(value = "linux-x86", preloadpath = {"/usr/lib32/", "/usr/lib/"}),
@Platform(value = "linux-x86_64", preloadpath = {"/usr/lib64/", "/usr/lib/"})
}
)
public class image_buffer implements InfoMapper {
@Override
public void map(InfoMap infoMap) {
}
}
自动生成jni接口步骤
javacpp是支持根据c++的头文件生成jni接口的, 不需要我们手动编写jni，但是对于一些采用函数指针的方式回调java，需要我们自己编写jni接口, 然后使用javacpp, 通过jni生成c++的头文件的
- 编写c++头文件
- 在java端编写preset, 映射关系 ===> InfoMap
执行javacpp-1.5.7.jar命令, 生成jni接口
代码示例
presets文件编写
presets是一个java文件用于描述java和c++之间的映射关系的
常用注解
@Properties( inherit = {javacpp.class}, target = "org.bytedeco.javacppexample.jni", global = "org.bytedeco.javacppexample.global.javacpp_example_global", value = { @Platform( // 如果c++中有智能指针等, 必须在这定义宏, 而不是在c++文件中定义, 否则会出现意向不到的事情 // 比如编译报错 // 如果你在c++文件中定义 #define SHARED_PTR_NAMESPACE std, 那编译也会报错, 因为javacpp将std // 当初了整形变量, 定义在XxxxGolbal中了 // 如果你在c++文件中定义#define SHARED_PTR_NAMESPACE, 有可能编译不报错, 但是很有可能出现内存 // 泄露或者程序运行一段时间崩溃的问题 define = { "SHARED_PTR_NAMESPACE std", "UNIQUE_PTR_NAMESPACE std" }, value = { "linux-arm64", "linux-x86", "linux-x86_64", "macosx-x86_64", "windows-x86", "windows-x86_64" }, include = {"javacpp_example.h"}, link = { "javacpp_example"} ), @Platform(value = "android", preload = ""), @Platform(value = "ios", preload = {"liblibjpeg", "liblibpng", "liblibprotobuf", "liblibwebp", "libzlib", "libopencv_core"}), @Platform(value = "linux", preloadpath = {"/usr/lib/", "/usr/lib32/", "/usr/lib64/"}), @Platform(value = "linux-armhf", preloadpath = {"/usr/arm-linux-gnueabihf/lib/", "/usr/lib/arm-linux-gnueabihf/"}), @Platform(value = "linux-arm64", preloadpath = {"/usr/aarch64-linux-gnu/lib/", "/usr/lib/aarch64-linux-gnu/"}), @Platform(value = "linux-x86", preloadpath = {"/usr/lib32/", "/usr/lib/"}), @Platform(value = "linux-x86_64", preloadpath = {"/usr/lib64/", "/usr/lib/"}) } ) public class javacpp_example implements InfoMapper { // static { Loader.checkVersion("com.concise", "demo"); } @Override public void map(InfoMap infoMap) { } }
说明:
- target: 生成的jni类所存放的包名
- global：生成的全局类所存放的包名, 用于存放非类中的函数, 枚举， 宏定义等非类中内容数据
- Platform：构建动态库时配置
解决内存泄漏问题
javacpp中生成的jni类和指针类 (Pointer 以及子类), 需要调用 releaseReference() 函数释放引用, 否则会有内存问题
解决jni崩溃问题
c++返回的uchar*导致崩溃
错误现象
如何复现错误
通过grpc服务端流可以快速复现
proto
syntax = "proto3";
package demo;
option java_multiple_files = true;
option java_package = "com.concise.jni.javacpp.grpc.sdk";
option java_outer_classname = "DemoProto";
option objc_class_prefix = "HLW";
service JavacppDemoService {
// 以服务端流的形式发送数据 (给客户端发送数据)
rpc findDemo (FindDemoRequest) returns (stream FindDemoResponse){}
}
message FindDemoResponse {
string message = 1;
bytes image = 2;
}
message FindDemoRequest {
string message = 1;
}
grpc服务端代码
package com.concise.jni.javacpp.grpc;
import cn.hutool.core.io.FileUtil;
import com.concise.jni.javacpp.grpc.sdk.FindDemoRequest;
import com.concise.jni.javacpp.grpc.sdk.FindDemoResponse;
import com.concise.jni.javacpp.grpc.sdk.JavacppDemoServiceGrpc;
import com.google.protobuf.ByteString;
import io.grpc.stub.StreamObserver;
import net.devh.boot.grpc.server.service.GrpcService;
import org.bytedeco.javacpp.BytePointer;
import org.bytedeco.javacppexample.jni.JavaCppExample;
import org.bytedeco.javacppexample.jni.MediaData;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.nio.charset.StandardCharsets;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
/**
* @author shenguangyang
* @date 2022-05-15 16:12
*/
@GrpcService
public class JavacppDemoGrpcServer extends JavacppDemoServiceGrpc.JavacppDemoServiceImplBase {
private static final Logger log = LoggerFactory.getLogger(JavacppDemoGrpcServer.class);
private static final AtomicInteger requestNum = new AtomicInteger(1);
private static final String IMAGE_PATH_PRE = "/mnt/project/javacpp-native/images";
/**
*/
@Override
public void findDemo(FindDemoRequest request, StreamObserver<FindDemoResponse> responseObserver) {
String message = request.getMessage();
String id = String.valueOf(requestNum.addAndGet(1));
while (true) {
JavaCppExample javaCppExample = new JavaCppExample("hjw34er2345".getBytes(StandardCharsets.UTF_8), "测试数据", 34);
long count = 1;
while (count++ < 2000) {
MediaData mediaData = javaCppExample.demo10_1();
BytePointer imagePointer = mediaData.get_data();
try {
if (imagePointer == null) {
TimeUnit.MILLISECONDS.sleep(200);
continue;
}
long length = mediaData.get_length();
log.info("id: {}, start read image length: {}", id, length);
byte[] image = new byte[(int) length];
imagePointer.get(image, 0, (int) length);
log.info("id: {}, end read image length: {}", id, length);
if (count % 100 == 0) {
String imagePath = IMAGE_PATH_PRE + "/demo10-" + id + ".jpg";
log.info("id: {}, grpc demo10, count: {}, length: {}", id, count, length);
FileUtil.writeBytes(image, imagePath);
}
FindDemoResponse response = FindDemoResponse.newBuilder()
.setImage(ByteString.copyFrom(image)).build();
responseObserver.onNext(response);
} catch (Exception e) {
e.printStackTrace();
} finally {
if (imagePointer != null) {
imagePointer.releaseReference();
}
mediaData.releaseReference();
}
}
javaCppExample.releaseReference();
}
// responseObserver.onCompleted();
}
}
客户端代码， 注意, 不调用demo.next()方法可以快速复现崩溃问题
@Component
public class JavacppDemoGrpcClient {
private static final Logger log = LoggerFactory.getLogger(JavacppDemoGrpcClient.class);
/**
* 异步 stub
*/
@GrpcClient(value = "javacppDemoService")
JavacppDemoServiceGrpc.JavacppDemoServiceStub asyncStub;
/**
* 阻塞模式
* 拦截器需要在注解里写明
*/
@GrpcClient(value = "javacppDemoService")
JavacppDemoServiceGrpc.JavacppDemoServiceBlockingStub blockingStub;
public void findDemo() throws InterruptedException {
FindDemoRequest request = FindDemoRequest.newBuilder().build();
// 接收服务端不断返回的数据
Iterator<FindDemoResponse> demo = blockingStub.findDemo(request);
while (demo.hasNext()) {
// FindDemoResponse next = demo.next();
// log.info(demo.next().getMessage());
// TimeUnit.MILLISECONDS.sleep(10);
}
log.info("grpc client end ==> findDemo");
}
}
查找错误位置
查看/mnt/project/javacpp-native/java/jni/hs_err_pid32607.log日志
Stack: [0x00007fb0bd9d2000,0x00007fb0bdad3000], sp=0x00007fb0bdad1368, free space=1020k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
C [libc.so.6+0x18b733]
Java frames: (J=compiled Java code, j=interpreted, Vv=VM code)
j org.bytedeco.javacpp.BytePointer.get([BII)Lorg/bytedeco/javacpp/BytePointer;+0
j com.concise.jni.javacpp.grpc.JavacppDemoGrpcServer.findDemo(Lcom/concise/jni/javacpp/grpc/sdk/FindDemoRequest;Lio/grpc/stub/StreamObserver;)V+144
j com.concise.jni.javacpp.grpc.sdk.JavacppDemoServiceGrpc$MethodHandlers.invoke(Ljava/lang/Object;Lio/grpc/stub/StreamObserver;)V+33
j io.grpc.stub.ServerCalls$UnaryServerCallHandler$UnaryServerCallListener.onHalfClose()V+53
j io.grpc.PartialForwardingServerCallListener.onHalfClose()V+4
j io.grpc.ForwardingServerCallListener.onHalfClose()V+1
j io.grpc.ForwardingServerCallListener$SimpleForwardingServerCallListener.onHalfClose()V+1
j io.grpc.Contexts$ContextualizedServerCallListener.onHalfClose()V+9
j io.grpc.internal.ServerCallImpl$ServerStreamListenerImpl.halfClosed()V+39
j io.grpc.internal.ServerImpl$JumpToApplicationThreadServerStreamListener$1HalfClosed.runInContext()V+26
j io.grpc.internal.ContextRunnable.run()V+9
j io.grpc.internal.SerializingExecutor.run()V+31
j java.util.concurrent.ThreadPoolExecutor.runWorker(Ljava/util/concurrent/ThreadPoolExecutor$Worker;)V+95
j java.util.concurrent.ThreadPoolExecutor$Worker.run()V+5
j java.lang.Thread.run()V+11
v ~StubRoutines::call_stub
导致这个错误的地方是在java中调用了c++函数获取返回对象，并从返回对象中获取图片数据崩溃的, 位置是 imagePointer.get(image, 0, (int) length);
package com.concise.jni.javacpp.grpc;
import cn.hutool.core.io.FileUtil;
import com.concise.jni.javacpp.grpc.sdk.FindDemoRequest;
import com.concise.jni.javacpp.grpc.sdk.FindDemoResponse;
import com.concise.jni.javacpp.grpc.sdk.JavacppDemoServiceGrpc;
import com.google.protobuf.ByteString;
import io.grpc.stub.StreamObserver;
import net.devh.boot.grpc.server.service.GrpcService;
import org.bytedeco.javacpp.BytePointer;
import org.bytedeco.javacppexample.jni.JavaCppExample;
import org.bytedeco.javacppexample.jni.MediaData;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.nio.charset.StandardCharsets;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
/**
* @author shenguangyang
* @date 2022-05-15 16:12
*/
@GrpcService
public class JavacppDemoGrpcServer extends JavacppDemoServiceGrpc.JavacppDemoServiceImplBase {
private static final Logger log = LoggerFactory.getLogger(JavacppDemoGrpcServer.class);
private static final AtomicInteger requestNum = new AtomicInteger(1);
private static final String IMAGE_PATH_PRE = "/mnt/project/javacpp-native/images";
/**
*/
@Override
public void findDemo(FindDemoRequest request, StreamObserver<FindDemoResponse> responseObserver) {
String message = request.getMessage();
String id = String.valueOf(requestNum.addAndGet(1));
while (true) {
JavaCppExample javaCppExample = new JavaCppExample("hjw34er2345".getBytes(StandardCharsets.UTF_8), "测试数据", 34);
long count = 1;
while (count++ < 2000) {
MediaData mediaData = javaCppExample.demo10_1();
BytePointer imagePointer = mediaData.get_data();
try {
if (imagePointer == null) {
TimeUnit.MILLISECONDS.sleep(200);
continue;
}
long length = mediaData.get_length();
log.info("id: {}, start read image length: {}", id, length);
byte[] image = new byte[(int) length];
imagePointer.get(image, 0, (int) length);
log.info("id: {}, end read image length: {}", id, length);
if (count % 100 == 0) {
String imagePath = IMAGE_PATH_PRE + "/demo10-" + id + ".jpg";
log.info("id: {}, grpc demo10, count: {}, length: {}", id, count, length);
FileUtil.writeBytes(image, imagePath);
}
FindDemoResponse response = FindDemoResponse.newBuilder()
.setImage(ByteString.copyFrom(image)).build();
responseObserver.onNext(response);
} catch (Exception e) {
e.printStackTrace();
} finally {
if (imagePointer != null) {
imagePointer.releaseReference();
}
mediaData.releaseReference();
}
}
javaCppExample.releaseReference();
}
// responseObserver.onCompleted();
}
}
进入到BytePointer到get方法， 可以看到这是javacpp的native函数
/**
* Reads a portion of the native array into a Java array.
*
* @param array the array to write to
* @param offset the offset into the array where to start writing
* @param length the length of data to read and write
* @return this
*/
public native BytePointer get(byte[] array, int offset, int length);
接下来我们查看native中的函数
通过javacpp生成jni类和jni源文件, 在如下红框目录下执行命令
java -jar javacpp-1.5.7.jar -encoding "utf-8" -Xcompiler "-std=c++14" org/bytedeco/javacppexample/jni/*.java \
org/bytedeco/javacppexample/global/*.java
# 如果不想要编译和删除cpp文件, 添加-nocompile
java -jar javacpp-1.5.7.jar -encoding "utf-8" -nocompile -Xcompiler "-std=c++14" org/bytedeco/javacppexample/jni/*.java \
org/bytedeco/javacppexample/global/*.java
生成的文件中有一个叫javacpp文件，找到get对应的函数， 经过调试是在memcpy位置崩掉的, 那盲猜测应该是c++返回的uchar*有问题, 很有可能离开作用域变成了野指针, 后来也验证了这一点
JNIEXPORT jobject JNICALL Java_org_bytedeco_javacpp_BytePointer_get___3BII(JNIEnv* env, jobject obj, jbyteArray arg0, jint arg1, jint arg2) {
static int count = 1;
signed char* ptr = (signed char*)jlong_to_ptr(env->GetLongField(obj, JavaCPP_addressFID));
if (ptr == NULL) {
env->ThrowNew(JavaCPP_getClass(env, 20), "This pointer address is NULL.");
return 0;
}
jlong position = env->GetLongField(obj, JavaCPP_positionFID);
ptr += position;
signed char* ptr0 = arg0 == NULL ? NULL : (jbyte*)env->GetPrimitiveArrayCritical(arg0, NULL);
jobject rarg = obj;
memcpy(ptr0 + arg1, ptr, arg2 * sizeof(*ptr0));
if (arg0 != NULL) env->ReleasePrimitiveArrayCritical(arg0, ptr0, 0);
return rarg;
}
解决方案
进入到c++中查看对应的函数实现, std::vector
很有可能被c++给释放调了 (离开作用域) MediaData JavaCppExample::demo10_1() { MediaData media_data; cv::Mat tempFrame = this->frame.clone(); if (tempFrame.empty()) { std::cout << "cpp => demo10_1 ===> tempFrame is null" << std::endl; return media_data; } std::vector<uchar> buff; matToJpeg(tempFrame, buff); // 这种方式会有很多不确定因素, 比如在java端通过javacpp从uchar* 指针中拷贝数据到java的byte[]时候, 由于uchar* 很有可能变成野指针 //, 而javacpp拷贝是调用c++的memcpy, 你拷贝一个野指针到java的byte[], 你不崩溃谁崩溃 media_data.set_data(buff.data()); media_data.set_length(buff.size()); std::cout << "cpp => demo10_1 v1 ===> length: " << buff.size() << std::endl; return media_data; }
正确的写法
MediaData JavaCppExample::demo10_1()
{
MediaData media_data;
cv::Mat tempFrame = this->frame.clone();
if (tempFrame.empty())
{
std::cout << "cpp => demo10_1 ===> tempFrame is null" << std::endl;
return media_data;
}
std::vector<uchar> buff;
matToJpeg(tempFrame, buff);
// 这种方式会有很多不确定因素, 比如在java端通过javacpp从uchar* 指针中拷贝数据到java的byte[]时候, 由于uchar* 很有可能变成野指针
//, 而javacpp拷贝是调用c++的memcpy, 你拷贝一个野指针到java的byte[], 你不崩溃谁崩溃
// media_data.set_data(buff.data());
// 正确方式, 注意在析构要手动删除uchar*, delete[] data;
uchar* data = new uchar[buff.size()];
memcpy(data, buff.data(), buff.size());
media_data.set_data(data);
media_data.set_length(buff.size());
std::cout << "cpp => demo10_1 v1 ===> length: " << buff.size() << std::endl;
return media_data;
}
MediaData类
//
// Created by sheng on 2022/3/12.
//
#ifndef __MEDIA_DATA__H
#define __MEDIA_DATA__H
#include <iostream>
#include <unistd.h>
#include <string.h>
#include <memory>
#include <malloc.h>
#include <thread>
#include <pthread.h>
#include <time.h>
#include <vector>
typedef unsigned char uchar;
enum MediaType
{
IMAGE_JPEG, VIDEO_MP4
};
/**
* @brief 媒体信息, 只存放视频和图片
*
*/
class MediaData {
public:
MediaData() {
};
// 一定要加上析构函数，否则会有内存溢出问题
~MediaData() {
delete[] data;
std::cout << "release MediaData and delete data" << std::endl;
};
MediaData(uchar* data, long length) : data(data), length(length) {};
uchar* get_data() { return this->data; }
void set_data(uchar* data) { this->data = data; }
const long get_length() { return this->length; }
void set_length(const long length) { this->length = length; }
const MediaType get_type() { return this->type; }
void set_type(const MediaType type) { this->type = type; }
const int get_width() { return this->width; }
void set_width(const int width) { this->width = width; }
const int get_height() { return this->height; }
void set_height(const int height) { this->height = height; }
private:
// 对于jni调用, 需要通过new uchar[length]创建, 否则会有很有不确定因素
// 比如野指针
uchar* data = nullptr;
long length = 0;
MediaType type;
// 宽度和高度
int width = 0;
int height = 0;
};
#endif //__IMAGE_BUFFER_PLUS__H
注意事项(重要)
如果c++和java之间传输大量图片, 使用不当很有可能存在内存溢出问题
- BytePointer需要进行手动释放, 否则会有内存溢出的风险
- 假如，你的项目依赖了某些公共的cpp代码，而这个公共模块还是独立的，如果你修改了公共的代码，最好将依赖公共模块的工程重新编译，以及通过javacpp重新生成动态库, 防止出现意外问题
- 我在实际项目中，就是犯了这种错误，我修改了算法代码并重新编译了，而没有重新编译我自己的c++项目和jni，导致java调c++中某个函数且该函数中启动了一个线程调用了算法的动态库，每当运行一段时间就发生BytePointe (0 bytes)这种致命错误
如果c++中有使用智能指针, 需要在preset定义宏, 也可以定义一些其他的宏
package org.bytedeco.javacppexample.presets;
import org.bytedeco.javacpp.annotation.Platform;
import org.bytedeco.javacpp.annotation.Properties;
import org.bytedeco.javacpp.presets.javacpp;
import org.bytedeco.javacpp.tools.InfoMap;
import org.bytedeco.javacpp.tools.InfoMapper;
/**
* @author shenguangyang
* @date 2022-03-15 21:36
*/
@Properties(
inherit = {javacpp.class},
target = "org.bytedeco.javacppexample.jni",
global = "org.bytedeco.javacppexample.global.image_buffer_global",
value = {
@Platform(
// 如果c++中有智能指针等, 必须在这定义宏, 而不是在c++文件中定义, 否则会出现意向不到的事情
// 比如编译报错
// 如果你在c++文件中定义 #define SHARED_PTR_NAMESPACE std, 那编译也会报错, 因为javacpp将std
// 当初了整形变量, 定义在XxxxGolbal中了
// 如果你在c++文件中定义#define SHARED_PTR_NAMESPACE, 有可能编译不报错, 但是很有可能出现内存
// 泄露或者程序运行一段时间崩溃的问题
define = {
"SHARED_PTR_NAMESPACE std",
"UNIQUE_PTR_NAMESPACE std"
},
value = {
"linux-x86",
"linux-x86_64",
"macosx-x86_64",
"windows-x86",
"windows-x86_64"
},
include = {"image_buffer.h"},
link = {"jni_utils" }
),
@Platform(value = "android", preload = ""),
@Platform(value = "ios", preload = {"liblibjpeg", "liblibpng", "liblibprotobuf", "liblibwebp", "libzlib", "libopencv_core"}),
@Platform(value = "linux", preloadpath = {"/usr/lib/", "/usr/lib32/", "/usr/lib64/"}),
@Platform(value = "linux-armhf", preloadpath = {"/usr/arm-linux-gnueabihf/lib/", "/usr/lib/arm-linux-gnueabihf/"}),
@Platform(value = "linux-arm64", preloadpath = {"/usr/aarch64-linux-gnu/lib/", "/usr/lib/aarch64-linux-gnu/"}),
@Platform(value = "linux-x86", preloadpath = {"/usr/lib32/", "/usr/lib/"}),
@Platform(value = "linux-x86_64", preloadpath = {"/usr/lib64/", "/usr/lib/"})
}
)
public class image_buffer implements InfoMapper {
@Override
public void map(InfoMap infoMap) {
}
}
若有收获，就点个赞吧
0 人点赞
