Minimizing allocations in exception processing

gershnik · May 7, 2024 · ce81ce2 · ce81ce2
1 parent 2dd1015
commit ce81ce2
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Showing 3 changed files with 51 additions and 10 deletions.
diff --git a/src/java_exception.cpp b/src/java_exception.cpp
@@ -24,6 +24,11 @@
 
 using namespace smjni;
 
+static constexpr char g_defaultWhat[] = "smjni::java_exception";
+static constexpr char g_defaultWhatPrefix[] = "smjni::java_exception: ";
+
+
+
 const char * java_exception::what() const noexcept
 { 
     if (m_what.empty())
@@ -43,19 +48,15 @@ const char * java_exception::what() const noexcept
 
 std::string java_exception::do_what() const
 {
-    std::string ret = "smjni::java_exception";
-
     JNIEnv * jenv = jni_provider::get_jni();
     auto message = java_runtime::object().toString(jenv, m_throwable.c_ptr());
     if (!message)
-        return ret;
-    jsize len = java_string_get_length(jenv, message);
-    if (!len)
-        return ret;
-    std::vector<jchar> buf(len);
-    java_string_get_region(jenv, message, 0, len, &buf[0]);
-    ret += ": ";
-    utf16_to_utf8(buf.begin(), buf.end(), std::back_inserter(ret));
+        return g_defaultWhat;
+    java_string_access messageAccess(jenv, message);
+    std::string ret;
+    ret.reserve(std::size(g_defaultWhatPrefix) - 1 + messageAccess.size());
+    ret = g_defaultWhatPrefix;
+    utf16_to_utf8(messageAccess.begin(), messageAccess.end(), std::back_inserter(ret));
     return ret;
 }
 

diff --git a/tests/src/cpp/integration_tests.cpp b/tests/src/cpp/integration_tests.cpp
@@ -251,4 +251,25 @@ jByteBuffer JNICALL TestSimpleJNI::doTestDirectBuffer(JNIEnv * env, jclass, jByt
     return nullptr;
 }
 
+TEST_CASE( "testExceptionFromJava" ) 
+{
+    JNIEnv * env = jni_provider::get_jni();
+    CHECK_THROWS_WITH_AS(java_classes::get<TestSimpleJNI>().testExceptionFromJava(env), 
+                "smjni::java_exception: java.lang.RuntimeException: hello world", smjni::java_exception);
+}
+
+TEST_CASE( "testExceptionPassthrough" ) 
+{
+    JNIEnv * env = jni_provider::get_jni();
+    java_classes::get<TestSimpleJNI>().testExceptionPassthrough(env);
+}
+
+void JNICALL TestSimpleJNI::doTestExceptionPassthrough(JNIEnv * env, jclass) 
+{
+    NATIVE_PROLOG
+        java_classes::get<TestSimpleJNI>().testExceptionFromJava(env);
+    NATIVE_EPILOG
+}
+
+
 TEST_SUITE_END();
diff --git a/tests/src/java/smjni/tests/TestSimpleJNI.java b/tests/src/java/smjni/tests/TestSimpleJNI.java
@@ -158,4 +158,23 @@ private static void testDirectBuffer()
     }
 
     private static native ByteBuffer doTestDirectBuffer(ByteBuffer buffer);
+
+    @CalledByNative
+    private static void testExceptionFromJava() {
+        throw new RuntimeException("hello world");
+    }
+
+    @CalledByNative
+    private static void testExceptionPassthrough() {
+        try {
+            doTestExceptionPassthrough();
+            fail("exception not thrown");
+        } catch(RuntimeException ex) {
+            assertEquals(ex.toString(), "java.lang.RuntimeException: hello world");
+        } catch(Exception ex) {
+            fail("exception of wrong type thrown");
+        }
+    }
+
+    private static native void doTestExceptionPassthrough();
 }