Let JUTFString takes ownership

LSPosed · Dec 7, 2023 · 1322920 · 1322920
1 parent 92a6a72
commit 1322920
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Showing 2 changed files with 38 additions and 42 deletions.
diff --git a/lsplant/src/main/jni/include/utils/jni_helper.hpp b/lsplant/src/main/jni/include/utils/jni_helper.hpp
@@ -4,6 +4,8 @@
 #include <jni.h>
 
 #include <string>
+#include <memory>
+#include <functional>
 #include <string_view>
 
 #pragma clang diagnostic push
@@ -30,6 +32,7 @@ concept JObject = std::is_base_of_v<std::remove_pointer_t<_jobject>, std::remove
 
 template <JObject T>
 class ScopedLocalRef {
+    friend class JUTFString;
 public:
     using BaseType [[maybe_unused]] = T;
 
@@ -181,56 +184,55 @@ inline auto JNI_NewStringUTF(JNIEnv *env, std::string_view sv) {
 
 class JUTFString {
 public:
-    JUTFString(JNIEnv *env, jstring jstr) : JUTFString(env, jstr, nullptr) {}
+    JUTFString(JNIEnv *env, jstring jstr, const char *default_cstr = nullptr) : JUTFString(ScopedLocalRef<jstring>(env, (jstring) env->NewLocalRef(jstr)), default_cstr) {}
 
     JUTFString(const ScopedLocalRef<jstring> &jstr)
-        : JUTFString(jstr.env_, jstr.local_ref_, nullptr) {}
-
-    JUTFString(JNIEnv *env, jstring jstr, const char *default_cstr)
-        : env_(env), jstr_(jstr) {
-        if (env_ && jstr_)
-            cstr_ = env_->GetStringUTFChars(jstr, nullptr);
-        else
-            cstr_ = default_cstr;
+        : JUTFString(jstr.clone(), nullptr) {}
+
+    JUTFString(ScopedLocalRef<jstring> &&jstr, const char *default_cstr = nullptr)
+        : jstr_(std::move(jstr)) {
+        if (jstr_)
+            jstr_.env_->GetStringUTFChars(jstr, nullptr);
+        else {
+            if (default_cstr) {
+                auto len = strlen(default_cstr);
+                auto str = new char[len + 1];
+                memcpy(str, default_cstr, len + 1);
+                str_.reset(str);
+            }
+            jstr_.reset();
+        }
     }
 
-    operator const char *() const { return cstr_; }
+    operator const char *() const { return str_.get(); }
 
-    operator const std::string() const { return cstr_; }
+    operator const std::string() const { return str_ ? str_.get() : ""; }
 
-    operator const bool() const { return cstr_ != nullptr; }
+    operator const bool() const { return str_ != nullptr; }
 
-    auto get() const { return cstr_; }
-
-    ~JUTFString() {
-        if (env_ && jstr_) env_->ReleaseStringUTFChars(jstr_, cstr_);
-    }
+    auto get() const { return str_.get(); }
 
     JUTFString(JUTFString &&other)
-        : env_(std::move(other.env_)),
-          jstr_(std::move(other.jstr_)),
-          cstr_(std::move(other.cstr_)) {
-        other.cstr_ = nullptr;
+        : jstr_(std::move(other.jstr_)),
+        str_(std::move(other.str_)) {
     }
 
     JUTFString &operator=(JUTFString &&other) {
-        if (&other != this) {
-            env_ = std::move(other.env_);
-            jstr_ = std::move(other.jstr_);
-            cstr_ = std::move(other.cstr_);
-            other.cstr_ = nullptr;
-        }
+        jstr_ = std::move(other.jstr_);
+        str_ = std::move(other.str_);
         return *this;
     }
 
 private:
-    JNIEnv *env_;
-    jstring jstr_;
-    const char *cstr_;
-
-    JUTFString(const JUTFString &) = delete;
+    ScopedLocalRef<jstring> jstr_;
+    std::unique_ptr<const char[], std::function<void(const char *)>> str_ {nullptr, [this](const char str[]) {
+        if (jstr_)
+            jstr_.env_->ReleaseStringUTFChars(jstr_, str);
+        else
+            std::default_delete<const char[]>()(str);
+    }};
 
-    JUTFString &operator=(const JUTFString &) = delete;
+    DISALLOW_COPY_AND_ASSIGN(JUTFString);
 };
 
 template <typename Func, typename... Args>

diff --git a/lsplant/src/main/jni/lsplant.cc b/lsplant/src/main/jni/lsplant.cc
@@ -714,19 +714,13 @@ using ::lsplant::IsHooked;
 
     ScopedLocalRef<jclass> built_class{env};
     {
-        auto callback_name =
-            JNI_Cast<jstring>(JNI_CallObjectMethod(env, callback_method, method_get_name));
-        JUTFString callback_method_name(callback_name);
-        auto target_name =
-            JNI_Cast<jstring>(JNI_CallObjectMethod(env, target_method, method_get_name));
-        JUTFString target_method_name(target_name);
+        JUTFString callback_method_name(JNI_Cast<jstring>(JNI_CallObjectMethod(env, callback_method, method_get_name)));
+        JUTFString target_method_name(JNI_Cast<jstring>(JNI_CallObjectMethod(env, target_method, method_get_name)));
         auto callback_class = JNI_Cast<jclass>(
             JNI_CallObjectMethod(env, callback_method, method_get_declaring_class));
         auto callback_class_loader =
             JNI_CallObjectMethod(env, callback_class, class_get_class_loader);
-        auto callback_class_name =
-            JNI_Cast<jstring>(JNI_CallObjectMethod(env, callback_class, class_get_name));
-        JUTFString class_name(callback_class_name);
+        JUTFString class_name(JNI_Cast<jstring>(JNI_CallObjectMethod(env, callback_class, class_get_name)));
         if (!JNI_IsInstanceOf(env, hooker_object, callback_class)) {
             LOGE("callback_method is not a method of hooker_object");
             return nullptr;