java - 一般 JNA 问题(Discord Game SDK (C) -> Java)

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目标: 大家好，我正在尝试在 Java 中使用 Discord 的游戏 SDK。只是几个问题，提前感谢您的帮助!

问题 1:创建 JNA 结构时，我可以省略 setter/getter 吗？示例:

import com.sun.jna.Callback;
import com.sun.jna.Structure;

import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Objects;

/*
struct IDiscordCore {
    void (*destroy)(struct IDiscordCore* core);
    enum EDiscordResult (*run_callbacks)(struct IDiscordCore* core);
    void (*set_log_hook)(struct IDiscordCore* core, enum EDiscordLogLevel min_level, void* hook_data, void (*hook)(void* hook_data, enum EDiscordLogLevel level, const char* message));
    struct IDiscordApplicationManager* (*get_application_manager)(struct IDiscordCore* core);
    struct IDiscordUserManager* (*get_user_manager)(struct IDiscordCore* core);
    struct IDiscordImageManager* (*get_image_manager)(struct IDiscordCore* core);
    struct IDiscordActivityManager* (*get_activity_manager)(struct IDiscordCore* core);
    struct IDiscordRelationshipManager* (*get_relationship_manager)(struct IDiscordCore* core);
    struct IDiscordLobbyManager* (*get_lobby_manager)(struct IDiscordCore* core);
    struct IDiscordNetworkManager* (*get_network_manager)(struct IDiscordCore* core);
    struct IDiscordOverlayManager* (*get_overlay_manager)(struct IDiscordCore* core);
    struct IDiscordStorageManager* (*get_storage_manager)(struct IDiscordCore* core);
    struct IDiscordStoreManager* (*get_store_manager)(struct IDiscordCore* core);
    struct IDiscordVoiceManager* (*get_voice_manager)(struct IDiscordCore* core);
    struct IDiscordAchievementManager* (*get_achievement_manager)(struct IDiscordCore* core);
};
 */
public class IDiscordCore extends Structure {

    public interface OnDestroy extends Callback {
        void accept(IDiscordCore core);
    }

    public interface OnCallbacks extends Callback {
        EDiscordResult accept(IDiscordCore core);
    }

    private static final List<String> FIELD_ORDER = Collections.unmodifiableList(Arrays.asList(
            "destroy", "run_callbacks", "set_log_hook"
    ));

    public OnDestroy destroy;
    public OnCallbacks run_callbacks;
    public Object set_log_hook;

    @Override
    public boolean equals(Object o) {
        if(this == o)
            return true;
        if(!(o instanceof IDiscordCore))
            return false;
        IDiscordCore that = (IDiscordCore) o;
        return Objects.equals(destroy, that.destroy)
                && Objects.equals(run_callbacks, that.run_callbacks)
                && Objects.equals(set_log_hook, that.set_log_hook) ;
    }

    @Override
    public int hashCode() {
        return Objects.hash(destroy, run_callbacks, set_log_hook);
    }

    @Override
    protected List<String> getFieldOrder() {
        return FIELD_ORDER;
    }

}

问题 2:创建 JNA 结构时，我可以加载不打算用作 Java 对象的字段吗？示例:

import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Objects;

/*
//typedef int64_t DiscordClientId;
//typedef void* IDiscordCoreEvents;
struct DiscordCreateParams {
    DiscordClientId client_id;
    uint64_t flags;
    IDiscordCoreEvents* events;
    void* event_data;
    IDiscordApplicationEvents* application_events;
    DiscordVersion application_version;
    struct IDiscordUserEvents* user_events;
    DiscordVersion user_version;
    IDiscordImageEvents* image_events;
    DiscordVersion image_version;
    struct IDiscordActivityEvents* activity_events;
    DiscordVersion activity_version;
    struct IDiscordRelationshipEvents* relationship_events;
    DiscordVersion relationship_version;
    struct IDiscordLobbyEvents* lobby_events;
    DiscordVersion lobby_version;
    struct IDiscordNetworkEvents* network_events;
    DiscordVersion network_version;
    struct IDiscordOverlayEvents* overlay_events;
    DiscordVersion overlay_version;
    IDiscordStorageEvents* storage_events;
    DiscordVersion storage_version;
    struct IDiscordStoreEvents* store_events;
    DiscordVersion store_version;
    struct IDiscordVoiceEvents* voice_events;
    DiscordVersion voice_version;
    struct IDiscordAchievementEvents* achievement_events;
    DiscordVersion achievement_version;
};
 */
public class DiscordCreateParams extends Structure {

    public long client_id;

    public String flags;

    public Object events;

    public Object event_data;

    public Object application_events, application_version, user_events, user_version, image_events, image_version, activity_events, activity_version, relationship_events, relationship_version, lobby_events, lobby_version, network_events, network_version, overlay_events, overlay_version, storage_events, storage_version, store_events, store_version, voice_events, voice_version, achievement_events, achievement_version;

    private static final List<String> FIELD_ORDER = Collections.unmodifiableList(Arrays.asList("client_id", "flags", "events", "event_data", "application_events", "application_version", "user_events", "user_version", "image_events", "image_version", "activity_events", "activity_version", "relationship_events", "relationship_version", "lobby_events", "lobby_version", "network_events", "network_version", "overlay_events", "overlay_version", "storage_events", "storage_version", "store_events", "store_version", "voice_events", "voice_version", "achievement_events", "achievement_version"));

    @Override
    public boolean equals(Object o) {
        if(this == o)
            return true;
        if(!(o instanceof DiscordCreateParams))
            return false;
        DiscordCreateParams that = (DiscordCreateParams) o;
        return Objects.equals(client_id, that.client_id) && Objects.equals(flags, that.flags) && Objects.equals(events, that.events) && Objects.equals(event_data, that.event_data) && Objects.equals(application_events, that.application_events) && Objects.equals(application_version, that.application_version) && Objects.equals(user_events, that.user_events) && Objects.equals(user_version, that.user_version) && Objects.equals(image_events, that.image_events) && Objects.equals(image_version, that.image_version) && Objects.equals(activity_events, that.activity_events) && Objects.equals(activity_version, that.activity_version) && Objects.equals(relationship_events, that.relationship_events) && Objects.equals(relationship_version, that.relationship_version) && Objects.equals(lobby_events, that.lobby_events) && Objects.equals(lobby_version, that.lobby_version) && Objects.equals(network_events, that.network_events) && Objects.equals(network_version, that.network_version) && Objects.equals(overlay_events, that.overlay_events) && Objects.equals(overlay_version, that.overlay_version) && Objects.equals(storage_events, that.storage_events) && Objects.equals(store_version, that.store_version) && Objects.equals(voice_events, that.voice_events) && Objects.equals(voice_version, that.voice_version) && Objects.equals(achievement_events, that.achievement_events) && Objects.equals(achievement_version, that.achievement_version);
    }

    @Override
    public int hashCode() {
        return Objects.hash(client_id, flags, events, event_data, application_events, application_version, user_events, user_version, image_events, image_version, activity_events, activity_version, relationship_events, relationship_version, lobby_events, lobby_version, network_events, network_version, overlay_events, overlay_version, storage_events, storage_version, store_events, store_version, voice_events, voice_version, achievement_events, achievement_version);
    }

    @Override
    protected List<String> getFieldOrder() {
        return FIELD_ORDER;
    }

}

Answer 1

您可能想查看提交给 JNA 项目的许多用户映射，以了解总体思路，但您的问题的答案:

• 您不需要 setter/getter 。事实上，JNA 的 Structure 类要求您将每个元素声明为公共(public)，因此它们是不必要和多余的。它们有时被包含作为诸如将字符数组转换为字符串等操作的便捷方法，但通常被省略。

• 您必须包含要映射的 native 结构的每个元素，或至少包含等效的字节大小。如果它们是内联结构，则您必须实际使用映射。在上面的示例中，它们主要是指针 (struct *)，因此您只需在其位置放置一个 Pointer 对象即可消耗相同数量的内存。