Android: lazy initialization for method id.

base/android/jni_generator/jni_generator.py

Index: base/android/jni_generator/jni_generator.py
diff --git a/base/android/jni_generator/jni_generator.py b/base/android/jni_generator/jni_generator.py
index 354e33a0f57023560d3a94c0eb9574f5f7172b94..f400ca03c196b51ac3c2b52e061a9245a10753a2 100755
--- a/base/android/jni_generator/jni_generator.py
+++ b/base/android/jni_generator/jni_generator.py
@@ -601,13 +601,9 @@ $FORWARD_DECLARATIONS
 // Step 2: method stubs.
 $METHOD_STUBS
 
-// Step 3: GetMethodIDs and RegisterNatives.
-static void GetMethodIDsImpl(JNIEnv* env) {
-$GET_METHOD_IDS_IMPL
-}
+// Step 3: RegisterNatives.
 
 static bool RegisterNativesImpl(JNIEnv* env) {
-  GetMethodIDsImpl(env);

[joth, 2012/10/04 17:59:59]

one thing I did remember this morning: currently if there's some build/config
problem we get a crash on startup if any (app custom class) method can't be
found. with this change, we'll only get the crash way down line when method is
called, so will rely on 100% code coverage to find such issues...
would is be worth leaving in a debug-only variant of GetMethodIDs here that
merely DCHECKS(HasMethod(...)) for each of the (non-system) method IDs? i.e.
leave the registrations themselves to use LazyGet, but still have the benefit of
debug startup sanity check on this?

[bulach, 2012/10/04 18:58:17]

I agree in principle, but for app classes, how can there be a mismatch?
 
I mean, unless we have a broken build system :) but other than that, the JNI
should surely match the classes that are in the APK?

 $REGISTER_NATIVES_IMPL
   return true;
 }
@@ -624,7 +620,6 @@ $CLOSE_NAMESPACE
         'FORWARD_DECLARATIONS': self.GetForwardDeclarationsString(),
         'METHOD_STUBS': self.GetMethodStubsString(),
         'OPEN_NAMESPACE': self.GetOpenNamespaceString(),
-        'GET_METHOD_IDS_IMPL': self.GetMethodIDsImplString(),
         'REGISTER_NATIVES_IMPL': self.GetRegisterNativesImplString(),
         'CLOSE_NAMESPACE': self.GetCloseNamespaceString(),
         'HEADER_GUARD': self.header_guard,
@@ -660,13 +655,6 @@ $CLOSE_NAMESPACE
         ret += [self.GetKMethodArrayEntry(native)]
     return '\n'.join(ret)
 
-  def GetMethodIDsImplString(self):
-    ret = []
-    ret += [self.GetFindClasses()]
-    for called_by_native in self.called_by_natives:
-      ret += [self.GetMethodIDImpl(called_by_native)]
-    return '\n'.join(ret)
-
   def GetRegisterNativesImplString(self):
     """Returns the implementation for RegisterNatives."""
     template = Template("""\
@@ -682,7 +670,7 @@ ${KMETHODS}
     return false;
   }
 """)
-    ret = []
+    ret = [self.GetFindClasses()]
     all_classes = self.GetUniqueClasses(self.natives)
     all_classes[self.class_name] = self.fully_qualified_class
     for clazz in all_classes:
@@ -791,14 +779,15 @@ ${FUNCTION_SIGNATURE} {""")
 ${FUNCTION_SIGNATURE} __attribute__ ((unused));
 ${FUNCTION_SIGNATURE} {""")
     template = Template("""
-static jmethodID g_${JAVA_CLASS}_${METHOD_ID_VAR_NAME} = 0;
+static base::subtle::AtomicWord g_${JAVA_CLASS}_${METHOD_ID_VAR_NAME} = 0;
 ${FUNCTION_HEADER}
   /* Must call RegisterNativesImpl()  */
   DCHECK(g_${JAVA_CLASS}_clazz);
-  DCHECK(g_${JAVA_CLASS}_${METHOD_ID_VAR_NAME});
+  jmethodID method_id =
+    ${GET_METHOD_ID_IMPL}
   ${RETURN_DECLARATION}
   ${PRE_CALL}env->${ENV_CALL}(${FIRST_PARAM_IN_CALL},
-      g_${JAVA_CLASS}_${METHOD_ID_VAR_NAME}${PARAMS_IN_CALL})${POST_CALL};
+      method_id${PARAMS_IN_CALL})${POST_CALL};
   ${CHECK_EXCEPTION}
   ${RETURN_CLAUSE}
 }""")
@@ -853,6 +842,7 @@ ${FUNCTION_HEADER}
         'PARAMS_IN_CALL': params_for_call,
         'METHOD_ID_VAR_NAME': called_by_native.method_id_var_name,
         'CHECK_EXCEPTION': check_exception,
+        'GET_METHOD_ID_IMPL': self.GetMethodIDImpl(called_by_native)
     }
     values['FUNCTION_SIGNATURE'] = (
         function_signature_template.substitute(values))
@@ -921,12 +911,14 @@ jclass g_${JAVA_CLASS}_clazz = NULL;""")
 
   def GetMethodIDImpl(self, called_by_native):
     """Returns the implementation of GetMethodID."""
-    template = Template("""\
-  g_${JAVA_CLASS}_${METHOD_ID_VAR_NAME} =
-      base::android::Get${STATIC}MethodID${SUFFIX}(
-          env, g_${JAVA_CLASS}_clazz,
-          "${JNI_NAME}",
-          ${JNI_SIGNATURE});
+    template = Template("""
+  base::android::MethodID::LazyGet<
+      base::android::MethodID::METHODTYPE_${STATIC},
+      base::android::MethodID::EXCEPTIONCHECK_${CHECK_EXCEPTION}>(
+      env, g_${JAVA_CLASS}_clazz,
+      "${JNI_NAME}",
+      ${JNI_SIGNATURE},
+      &g_${JAVA_CLASS}_${METHOD_ID_VAR_NAME});
 """)
     jni_name = called_by_native.name
     jni_return_type = called_by_native.return_type
@@ -937,8 +929,8 @@ jclass g_${JAVA_CLASS}_clazz = NULL;""")
         'JAVA_CLASS': called_by_native.java_class_name or self.class_name,
         'JNI_NAME': jni_name,
         'METHOD_ID_VAR_NAME': called_by_native.method_id_var_name,
-        'STATIC': 'Static' if called_by_native.static else '',
-        'SUFFIX': 'OrNull' if called_by_native.system_class else '',
+        'STATIC': 'STATIC' if called_by_native.static else 'NORMAL',
+        'CHECK_EXCEPTION': 'NO' if called_by_native.system_class else 'YES',
         'JNI_SIGNATURE': JniSignature(called_by_native.params,
                                       jni_return_type,
                                       True)