简单的protobuf序列化与反序列化的例子

protobuf是一个google提供的序列化与反序列化的项目

如果想使用protobuf,首先需要下载protobuf的编译器

下载地址:https://github.com/protocolbuffers/protobuf/releasesicon-default.png?t=M3C8https://github.com/protocolbuffers/protobuf/releases

根据系统选择对应的protoc编译器 下载完成后,需要在项目中声明一个*.proto的文件作为数据格式的声明文件

新建:Student.proto

syntax = "proto2";
//必须指定一个package
package com.mjy.protobuf;

option optimize_for = SPEED;
option java_package = "com.mjy.protobuf";
option java_outer_classname = "DataInfo";

message Student {

	//name = 1并不表示name的value为1,1为参数的一个序号
	required string name = 1;
	optional int32 age = 2;
	optional string address = 3;

}

 使用命令编译该文件

D:/middleware/protoc-3.20.0-win64/bin/protoc.exe --java_out=src/main/java src/main/resources/proto/Student.proto

编译后将在指定package中生成一个java类,注意生成的类不能修改:

public class TestProto {

	//使用google protobuf将数据序列化与反序列化
	public static void main(String[] args) throws Exception {
		Student student = DataInfo.Student.newBuilder().setName("张三").setAge(20).setAddress("北京").build();
		//序列化
		byte[] arr = student.toByteArray();
		System.out.println(arr.length);   //18
		//反序列化
		Student student2 = DataInfo.Student.parseFrom(arr);
		System.out.println(student2.getName());      //张三
		System.out.println(student2.getAge());       //20
		System.out.println(student2.getAddress());   //北京
	}

}
// Generated by the protocol buffer compiler.  DO NOT EDIT!
// source: src/main/resources/proto/Student.proto

package com.mjy.protobuf;

public final class DataInfo {
  private DataInfo() {}
  public static void registerAllExtensions(
      com.google.protobuf.ExtensionRegistryLite registry) {
  }

  public static void registerAllExtensions(
      com.google.protobuf.ExtensionRegistry registry) {
    registerAllExtensions(
        (com.google.protobuf.ExtensionRegistryLite) registry);
  }
  public interface StudentOrBuilder extends
      // @@protoc_insertion_point(interface_extends:com.mjy.protobuf.Student)
      com.google.protobuf.MessageOrBuilder {

    /**
     * <pre>
     *name = 1并不表示name的value为1,1为参数的一个序号
     * </pre>
     *
     * <code>required string name = 1;</code>
     * @return Whether the name field is set.
     */
    boolean hasName();
    /**
     * <pre>
     *name = 1并不表示name的value为1,1为参数的一个序号
     * </pre>
     *
     * <code>required string name = 1;</code>
     * @return The name.
     */
    java.lang.String getName();
    /**
     * <pre>
     *name = 1并不表示name的value为1,1为参数的一个序号
     * </pre>
     *
     * <code>required string name = 1;</code>
     * @return The bytes for name.
     */
    com.google.protobuf.ByteString
        getNameBytes();

    /**
     * <code>optional int32 age = 2;</code>
     * @return Whether the age field is set.
     */
    boolean hasAge();
    /**
     * <code>optional int32 age = 2;</code>
     * @return The age.
     */
    int getAge();

    /**
     * <code>optional string address = 3;</code>
     * @return Whether the address field is set.
     */
    boolean hasAddress();
    /**
     * <code>optional string address = 3;</code>
     * @return The address.
     */
    java.lang.String getAddress();
    /**
     * <code>optional string address = 3;</code>
     * @return The bytes for address.
     */
    com.google.protobuf.ByteString
        getAddressBytes();
  }
  /**
   * Protobuf type {@code com.mjy.protobuf.Student}
   */
  public static final class Student extends
      com.google.protobuf.GeneratedMessageV3 implements
      // @@protoc_insertion_point(message_implements:com.mjy.protobuf.Student)
      StudentOrBuilder {
  private static final long serialVersionUID = 0L;
    // Use Student.newBuilder() to construct.
    private Student(com.google.protobuf.GeneratedMessageV3.Builder<?> builder) {
      super(builder);
    }
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      address_ = "";
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    protected java.lang.Object newInstance(
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    public static final int ADDRESS_FIELD_NUMBER = 3;
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     * @return Whether the address field is set.
     */
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    @java.lang.Override
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    public static com.mjy.protobuf.DataInfo.Student parseFrom(
        java.nio.ByteBuffer data)
        throws com.google.protobuf.InvalidProtocolBufferException {
      return PARSER.parseFrom(data);
    }
    public static com.mjy.protobuf.DataInfo.Student parseFrom(
        java.nio.ByteBuffer data,
        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
        throws com.google.protobuf.InvalidProtocolBufferException {
      return PARSER.parseFrom(data, extensionRegistry);
    }
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        throws com.google.protobuf.InvalidProtocolBufferException {
      return PARSER.parseFrom(data);
    }
    public static com.mjy.protobuf.DataInfo.Student parseFrom(
        com.google.protobuf.ByteString data,
        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
        throws com.google.protobuf.InvalidProtocolBufferException {
      return PARSER.parseFrom(data, extensionRegistry);
    }
    public static com.mjy.protobuf.DataInfo.Student parseFrom(byte[] data)
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      return PARSER.parseFrom(data);
    }
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using System; //需要用到MemoryStream using System.IO; using UnityEngine; //引入ProtoBuf命名空间 using ProtoBuf; /// /// 测试类 /// public class TestProtobuf : MonoBehaviour { /// /// 用于测试的数据类 /// [ProtoContract] //声明这个类能被序列化 public class UserData { //声明每一个需要被序列化的成员,编号从1开始 [ProtoMember(1)] public int id; [ProtoMember(2)] public string name; [ProtoMember(3)] public int level; } //测试代码 void Start() { //将要被序列化的UserData示例 UserData user1 = new UserData (); user1.id = 1; user1.name = "User1"; user1.level = 10; //打印user1 Debug.Log (string.Format ("user1-> id:{0}, name:{1}, level:{2}", user1.id, user1.name, user1.level)); //序列化 byte[] buff = null; using (MemoryStream ms = new MemoryStream ()) { Serializer.Serialize (ms, user1); ms.Position = 0; int length = (int)ms.Length; buff = new byte[length]; ms.Read (buff, 0, length); } //输出字节数组 Debug.Log (string.Format("Serialized data-> {0}", BitConverter.ToString(buff))); //反序列化 UserData user2 = default(UserData); using (MemoryStream ms = new MemoryStream (buff)) { user2 = Serializer.Deserialize (ms); } //打印反序列化生成的user2 Debug.Log (string.Format ("user2-> id:{0}, name:{1}, level:{2}", user2.id, user2.name, user2.level)); } } 作者:qufangliu 链接:https://www.jianshu.com/p/d9be1b3d2446 來源:简书 著作权归作者所有。商业转载请联系作者获得授权,非商业转载请注明出处。
<think>我们已知用户想在C语言中实现Protocol Buffers的序列化反序列化。 根据引用[1]和引用[2]提供的信息,我们了解到protobuf具有高效、跨平台等优点,并且使用流程包括定义数据结构、编译.proto文件生成代码,然后使用生成的代码进行序列化反序列化。 但是,引用中主要提到的是C++的实现,而用户需要的是C语言的实现。 注意:Protocol Buffers官方提供了对C语言的支持,但相对于C++来说,C语言的API可能没有那么丰富,且使用方式有所不同。 实现步骤: 1. 定义.proto文件:描述数据结构。 2. 使用protoc编译器生成C语言代码:需要安装protobuf-c编译器(官方的protobuf不同,C语言有单独的protobuf-c项目)。 3. 在C代码中包含生成的头文件,调用生成的API进行序列化反序列化。 具体步骤: 一、安装protobuf-c 需要先安装protobuf(C++)和protobuf-c(C语言)的库和编译器。 二、编写.proto文件 例如,我们定义一个简单的消息:person.proto ``` syntax = "proto2"; message Person { required string name = 1; required int32 id = 2; optional string email = 3; } ``` 三、使用protoc-c(protobuf-c提供的编译器)生成C代码 命令:`protoc-c --c_out=. person.proto` 生成两个文件:person.pb-c.h 和 person.pb-c.c 四、在C程序中使用生成的代码 序列化步骤: 1. 初始化一个消息对象(如Person)。 2. 设置消息的字段值。 3. 调用打包函数将消息序列化为字节流。 4. 使用完毕后,释放消息对象。 反序列化步骤: 1. 初始化一个消息对象(如Person)。 2. 调用解包函数将字节流解析到消息对象中。 3. 读取消息字段。 4. 释放消息对象。 示例代码: ```c #include <stdio.h> #include <stdlib.h> #include "person.pb-c.h" int main() { // 序列化 Person person = PERSON__INIT; // 初始化消息对象 person.name = "Alice"; person.id = 123; person.email = "alice@example.com"; // 计算序列化后的长度 size_t len = person__get_packed_size(&person); uint8_t *buf = malloc(len); // 序列化 person__pack(&person, buf); // 此时buf中就是序列化后的数据,可以发送或存储 // 反序列化 Person *unpacked_person = person__unpack(NULL, len, buf); if (unpacked_person == NULL) { fprintf(stderr, "Error unpacking person.\n"); return -1; } printf("Name: %s\n", unpacked_person->name); printf("ID: %d\n", unpacked_person->id); if (unpacked_person->email) printf("Email: %s\n", unpacked_person->email); // 释放反序列化得到的对象 person__free_unpacked(unpacked_person, NULL); free(buf); return 0; } ``` 注意事项: 1. 在C语言中,字符串字段是char*类型,并且需要确保字符串是以空字符结尾的(protobuf-c会自动处理)。 2. 对于repeated字段,会有对应的数组和长度字段,需要按照数组方式处理。 3. 内存管理:序列化时分配的buf需要手动释放;反序列化得到的对象需要使用特定的释放函数(如person__free_unpacked)释放,而不是直接free。 4. 检查解包函数的返回值,确保反序列化成功。 引用说明: 上述实现参考了protobuf-c的官方文档和使用方式,引用[2]中的C++实现类似,但使用的是protobuf-c的API。 由于引用[1][2]中提供的是C++的例子,而用户需要C语言,因此我们按照C语言的规范进行实现。 编译链接: 在编译时需要链接protobuf-c库,例如: `gcc -o example example.c person.pb-c.c -lprotobuf-c` 五、错误处理 在序列化反序列化过程中,如果出现错误(如内存不足、无效数据等),解包函数会返回NULL,需要检查并处理。 六、重复字段(repeated)的处理 对于repeated字段,在生成的结构体中会有两个字段:一个是数组指针,一个是数组长度(通常以n_为前缀)。例如: message Test { repeated int32 samples = 1; } 在C结构体中: size_t n_samples; int32_t *samples; 需要动态分配数组内存,并设置长度。 七、内存管理注意事项 对于消息中字符串或字节数组等动态分配的内存,protobuf-c在打包时不会深拷贝,因此需要确保在序列化时这些内存仍然有效。 在释放消息对象时(使用person__free_unpacked),protobuf-c会递归释放所有动态分配的内存(包括字符串和重复字段的数组),所以不能单独释放这些成员。 因此,用户需要按照上述步骤在C语言中使用protobuf-c库来实现序列化反序列化。 相关问题: 1. 如何在C语言中安装protobuf-c? 2. 如何处理protobuf中的repeated字段? 3. 如何优化protobuf-c的序列化性能? 4. 在C语言中使用protobuf有哪些常见的错误和陷阱?</think>### C语言中实现Protocol Buffers序列化反序列化 Protocol Buffers(protobuf)在C语言中的实现需要使用官方提供的 **protobuf-c** 库(非C++版本)。以下是完整实现步骤: --- #### 一、环境准备 1. 安装依赖库: ```bash # Ubuntu/Debian sudo apt-get install autoconf automake libtool curl make g++ # 下载并编译protobuf-c git clone https://github.com/protobuf-c/protobuf-c.git cd protobuf-c ./autogen.sh && ./configure && make && sudo make install ``` --- #### 二、定义.proto文件 创建 `person.proto` 文件: ```proto syntax = "proto2"; message Person { required string name = 1; required int32 id = 2; optional string email = 3; repeated string phone = 4; // 重复字段示例 } ``` --- #### 三、生成C语言代码 使用 `protoc-c` 编译器生成代码: ```bash protoc-c --c_out=. person.proto ``` 生成文件: - `person.pb-c.h`(头文件) - `person.pb-c.c`(实现文件) --- #### 四、序列化实现 ```c #include <stdio.h> #include <stdlib.h> #include "person.pb-c.h" void serialize_person() { // 1. 初始化Person对象 Person person = PERSON__INIT; person.name = "Alice"; person.id = 123; person.email = "alice@example.com"; // 2. 添加重复字段 const char *phones[] = {"123-4567", "987-6543"}; person.n_phone = 2; person.phone = (char**)phones; // 3. 计算序列化长度并分配内存 size_t len = person__get_packed_size(&person); uint8_t *buf = malloc(len); // 4. 执行序列化 person__pack(&person, buf); // 此时buf包含序列化数据,可用于网络传输/存储 // ... (实际使用中发送或保存buf) free(buf); } ``` --- #### 五、反序列化实现 ```c void deserialize_person(const uint8_t *data, size_t len) { // 1. 解包数据 Person *person = person__unpack(NULL, len, data); if (!person) { fprintf(stderr, "反序列化失败\n"); return; } // 2. 访问字段 printf("Name: %s\nID: %d\n", person->name, person->id); if (person->email) printf("Email: %s\n", person->email); // 3. 处理重复字段 for (size_t i = 0; i < person->n_phone; i++) { printf("Phone %zu: %s\n", i+1, person->phone[i]); } // 4. 释放资源 person__free_unpacked(person, NULL); } ``` --- #### 六、关键API说明 | 函数 | 作用 | |------|------| | `person__get_packed_size()` | 计算序列化后数据长度 | | `person__pack()` | 执行序列化操作 | | `person__unpack()` | 反序列化二进制数据 | | `person__free_unpacked()` | 释放反序列化对象内存 | --- #### 七、编译运行 编译命令(需链接protobuf-c库): ```bash gcc -o demo main.c person.pb-c.c -lprotobuf-c ``` 运行注意事项: 1. 序列化后的数据是二进制格式,不可直接打印 2. 跨平台传输时需注意字节序(protobuf自动处理) 3. 必须检查 `person__unpack()` 返回值避免空指针 --- #### 八、性能优化建议 1. **复用内存**:对频繁调用的对象使用内存池 2. **避免拷贝**:直接操作二进制缓冲区(如网络接收缓冲区) 3. **选择性解析**:使用 `protobuf_c_message_unpack()` 的字段掩码参数 > 提示:protobuf的二进制编码比XML小3~10倍,序列化速度提升20~100倍[^1]。 --- ### 相关问题 1. 如何处理protobuf中的嵌套消息(Nested Messages)? 2. 在C语言中如何实现protobuf数据的网络传输? 3. protobuf-c官方C++版本有何主要差异? 4. 如何为现有项目升级protobuf数据格式(兼容性策略)? [^1]: Protocol Buffers通过二进制编码和高效的序列化算法实现高性能,适用于资源受限的嵌入式系统。 [^2]: 重复字段(`repeated`)在C中通过动态数组实现,需配合`n_`前缀字段管理长度。
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