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      1 /*
      2  * Copyright (C) 2010 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #ifndef JNI_CONSTANTS_H_included
     18 #define JNI_CONSTANTS_H_included
     19 
     20 #include "JNIHelp.h"
     21 
     22 /**
     23  * A cache to avoid calling FindClass at runtime.
     24  *
     25  * Class lookup is relatively expensive (2.5us on passion-eng at the time of writing), so we do
     26  * all such lookups eagerly at VM startup. This means that code that never uses, say,
     27  * java.util.zip.Deflater still has to pay for the lookup, but it means that on a device the cost
     28  * is definitely paid during boot and amortized. A central cache also removes the temptation to
     29  * dynamically call FindClass rather than add a small cache to each file that needs one. Another
     30  * cost is that each class cached here requires a global reference, though in practice we save
     31  * enough by not having a global reference for each file that uses a class such as java.lang.String
     32  * which is used in several files.
     33  *
     34  * FindClass is still called in a couple of situations: when throwing exceptions, and in some of
     35  * the serialization code. The former is clearly not a performance case, and we're currently
     36  * assuming that neither is the latter.
     37  *
     38  * TODO: similar arguments hold for field and method IDs; we should cache them centrally too.
     39  */
     40 struct JniConstants {
     41     static void init(JNIEnv* env);
     42 
     43     static jclass bidiRunClass;
     44     static jclass bigDecimalClass;
     45     static jclass booleanClass;
     46     static jclass byteArrayClass;
     47     static jclass byteClass;
     48     static jclass charsetICUClass;
     49     static jclass constructorClass;
     50     static jclass deflaterClass;
     51     static jclass doubleClass;
     52     static jclass errnoExceptionClass;
     53     static jclass fieldClass;
     54     static jclass fieldPositionIteratorClass;
     55     static jclass fileDescriptorClass;
     56     static jclass gaiExceptionClass;
     57     static jclass inet6AddressClass;
     58     static jclass inetAddressClass;
     59     static jclass inetSocketAddressClass;
     60     static jclass inflaterClass;
     61     static jclass integerClass;
     62     static jclass localeDataClass;
     63     static jclass longClass;
     64     static jclass methodClass;
     65     static jclass mutableIntClass;
     66     static jclass mutableLongClass;
     67     static jclass parsePositionClass;
     68     static jclass patternSyntaxExceptionClass;
     69     static jclass realToStringClass;
     70     static jclass socketClass;
     71     static jclass socketImplClass;
     72     static jclass stringArrayClass;
     73     static jclass stringClass;
     74     static jclass structAddrinfoClass;
     75     static jclass structFlockClass;
     76     static jclass structGroupReqClass;
     77     static jclass structLingerClass;
     78     static jclass structPasswdClass;
     79     static jclass structPollfdClass;
     80     static jclass structStatClass;
     81     static jclass structStatFsClass;
     82     static jclass structTimevalClass;
     83     static jclass structUtsnameClass;
     84 };
     85 
     86 #define NATIVE_METHOD(className, functionName, signature) \
     87     { #functionName, signature, reinterpret_cast<void*>(className ## _ ## functionName) }
     88 
     89 #endif  // JNI_CONSTANTS_H_included
     90