src/starboard/android/shared/jni_env_ext.h

// Copyright 2017 The Cobalt Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef STARBOARD_ANDROID_SHARED_JNI_ENV_EXT_H_
#define STARBOARD_ANDROID_SHARED_JNI_ENV_EXT_H_

#include <android/native_activity.h>
#include <jni.h>

#include <cstdarg>
#include <cstring>
#include <string>

#include "starboard/common/log.h"

namespace starboard {
namespace android {
namespace shared {

// An extension to JNIEnv to simplify making JNI calls.
//
// Call the static Get() method to get an instance that is already attached to
// the JVM in the current thread.
//
// This extends the JNIEnv structure, which already has a C++ interface for
// calling JNI methods, so any JNIEnv method can be called directly on this.
//
// There are convenience methods to lookup and call Java methods on object
// instances in a single step, with even simpler methods to call Java methods on
// the StarboardBridge.
struct JniEnvExt : public JNIEnv {
  // One-time initialization to be called before starting the application.
  static void Initialize(JniEnvExt* jni_env, jobject starboard_bridge);

  // Called right before each native thread is about to be shutdown.
  static void OnThreadShutdown();

  // Returns the thread-specific instance of JniEnvExt.
  static JniEnvExt* Get();

  // Returns the StarboardBridge object.
  jobject GetStarboardBridge();

  // Lookup the class of an object and find a field in it.
  jfieldID GetStaticFieldIDOrAbort(jclass clazz,
                                   const char* name,
                                   const char* sig) {
    jfieldID field = GetStaticFieldID(clazz, name, sig);
    AbortOnException();
    return field;
  }

  jfieldID GetFieldIDOrAbort(jobject obj,
                             const char* name,
                             const char* sig) {
    jclass clazz = GetObjectClass(obj);
    AbortOnException();
    jfieldID field = GetFieldID(clazz, name, sig);
    AbortOnException();
    DeleteLocalRef(clazz);
    return field;
  }

  jint GetEnumValueOrAbort(jclass clazz, const char* name) {
    jfieldID field = GetStaticFieldIDOrAbort(clazz, name, "I");
    jint enum_value = GetStaticIntField(clazz, field);
    AbortOnException();
    return enum_value;
  }

  // Lookup the class of an object and find a method in it.
  jmethodID GetObjectMethodIDOrAbort(jobject obj,
                                     const char* name,
                                     const char* sig) {
    jclass clazz = GetObjectClass(obj);
    AbortOnException();
    jmethodID method_id = GetMethodID(clazz, name, sig);
    AbortOnException();
    DeleteLocalRef(clazz);
    return method_id;
  }

  jmethodID GetStaticMethodIDOrAbort(jclass clazz,
                                     const char* name,
                                     const char* sig) {
    jmethodID method = GetStaticMethodID(clazz, name, sig);
    AbortOnException();
    return method;
  }

  jobject GetObjectArrayElementOrAbort(jobjectArray array, jsize index) {
    jobject result = GetObjectArrayElement(array, index);
    AbortOnException();
    return result;
  }

  // Find a class by name using the application's class loader. This can load
  // both system classes and application classes, even when not in a JNI
  // stack frame (e.g. in a native thread that was attached the the JVM).
  // https://developer.android.com/training/articles/perf-jni.html#faq_FindClass
  jclass FindClassExtOrAbort(const char* name);

  jclass FindClassOrAbort(const char* name) {
    jclass result = FindClass(name);
    AbortOnException();
    return result;
  }

  // Convenience method to lookup and call a constructor.
  jobject NewObjectOrAbort(const char* class_name, const char* sig, ...) {
    va_list argp;
    va_start(argp, sig);
    jclass clazz = FindClassExtOrAbort(class_name);
    jmethodID methodID = GetMethodID(clazz, "<init>", sig);
    AbortOnException();
    jobject result = NewObjectV(clazz, methodID, argp);
    AbortOnException();
    DeleteLocalRef(clazz);
    va_end(argp);
    return result;
  }

  // Constructs a new java.lang.String object from an array of characters in
  // standard UTF-8 encoding. This differs from JNIEnv::NewStringUTF() which
  // takes JNI modified UTF-8.
  jstring NewStringStandardUTFOrAbort(const char* bytes) {
    const jstring charset = NewStringUTF("UTF-8");
    AbortOnException();
    const jbyteArray byte_array = NewByteArrayFromRaw(
        reinterpret_cast<const jbyte*>(bytes), strlen(bytes));
    AbortOnException();
    jstring result = static_cast<jstring>(NewObjectOrAbort(
        "java/lang/String", "([BLjava/lang/String;)V", byte_array, charset));
    DeleteLocalRef(byte_array);
    DeleteLocalRef(charset);
    return result;
  }

  // Returns a std::string representing the jstring in standard UTF-8 encoding.
  // This differs from JNIEnv::GetStringUTFChars() which returns modified UTF-8.
  // Also, the buffer of the returned bytes is managed by the std::string object
  // so it is not necessary to release it with JNIEnv::ReleaseStringUTFChars().
  std::string GetStringStandardUTFOrAbort(jstring str) {
    if (str == NULL) {
      return std::string();
    }
    const jstring charset = NewStringUTF("UTF-8");
    AbortOnException();
    const jbyteArray byte_array = static_cast<jbyteArray>(
        CallObjectMethodOrAbort(str, "getBytes", "(Ljava/lang/String;)[B",
                                charset));
    jsize array_length = GetArrayLength(byte_array);
    AbortOnException();
    void* bytes = GetPrimitiveArrayCritical(byte_array, NULL);
    AbortOnException();
    std::string result(static_cast<const char*>(bytes), array_length);
    ReleasePrimitiveArrayCritical(byte_array, bytes, JNI_ABORT);
    AbortOnException();
    DeleteLocalRef(byte_array);
    DeleteLocalRef(charset);
    return result;
  }

// Convenience methods to lookup and read a field or call a method all at once:
// Get[Type]FieldOrAbort() takes a jobject of an instance.
// Call[Type]MethodOrAbort() takes a jobject of an instance.
// CallStarboard[Type]MethodOrAbort() to call methods on the StarboardBridge.
#define X(_jtype, _jname)                                                      \
  _jtype Get##_jname##FieldOrAbort(jobject obj, const char* name,              \
                                   const char* sig) {                          \
    _jtype result = Get##_jname##Field(obj, GetFieldIDOrAbort(obj, name, sig));\
    AbortOnException();                                                        \
    return result;                                                             \
  }                                                                            \
                                                                               \
  _jtype GetStatic##_jname##FieldOrAbort(const char* class_name,               \
                                         const char* name, const char* sig) {  \
    jclass clazz = FindClassExtOrAbort(class_name);                            \
    return GetStatic##_jname##FieldOrAbort(clazz, name, sig);                  \
  }                                                                            \
                                                                               \
  _jtype GetStatic##_jname##FieldOrAbort(jclass clazz, const char* name,       \
                                         const char* sig) {                    \
    _jtype result = GetStatic##_jname##Field(                                  \
        clazz, GetStaticFieldIDOrAbort(clazz, name, sig));                     \
    AbortOnException();                                                        \
    return result;                                                             \
  }                                                                            \
                                                                               \
  _jtype Call##_jname##MethodOrAbort(jobject obj, const char* name,            \
                                     const char* sig, ...) {                   \
    va_list argp;                                                              \
    va_start(argp, sig);                                                       \
    _jtype result = Call##_jname##MethodVOrAbort(                              \
        obj, GetObjectMethodIDOrAbort(obj, name, sig), argp);                  \
    va_end(argp);                                                              \
    return result;                                                             \
  }                                                                            \
                                                                               \
  _jtype CallStarboard##_jname##MethodOrAbort(const char* name,                \
                                             const char* sig, ...) {           \
    va_list argp;                                                              \
    va_start(argp, sig);                                                       \
    jobject obj = GetStarboardBridge();                                        \
    _jtype result = Call##_jname##MethodVOrAbort(                              \
        obj, GetObjectMethodIDOrAbort(obj, name, sig), argp);                  \
    va_end(argp);                                                              \
    return result;                                                             \
  }                                                                            \
                                                                               \
  _jtype CallStatic##_jname##MethodOrAbort(                                    \
      const char* class_name, const char* method_name, const char* sig, ...) { \
    va_list argp;                                                              \
    va_start(argp, sig);                                                       \
    jclass clazz = FindClassExtOrAbort(class_name);                            \
    _jtype result = CallStatic##_jname##MethodVOrAbort(                        \
        clazz, GetStaticMethodIDOrAbort(clazz, method_name, sig), argp);       \
    DeleteLocalRef(clazz);                                                     \
    va_end(argp);                                                              \
    return result;                                                             \
  }                                                                            \
                                                                               \
  _jtype Call##_jname##MethodVOrAbort(jobject obj, jmethodID methodID,         \
                                      va_list args) {                          \
    _jtype result = Call##_jname##MethodV(obj, methodID, args);                \
    AbortOnException();                                                        \
    return result;                                                             \
  }                                                                            \
                                                                               \
  _jtype CallStatic##_jname##MethodVOrAbort(jclass clazz, jmethodID methodID,  \
                                            va_list args) {                    \
    _jtype result = CallStatic##_jname##MethodV(clazz, methodID, args);        \
    AbortOnException();                                                        \
    return result;                                                             \
  }

  X(jobject, Object)
  X(jboolean, Boolean)
  X(jbyte, Byte)
  X(jchar, Char)
  X(jshort, Short)
  X(jint, Int)
  X(jlong, Long)
  X(jfloat, Float)
  X(jdouble, Double)

#undef X

  void CallVoidMethod(jobject obj, const char* name, const char* sig, ...) {
    va_list argp;
    va_start(argp, sig);
    CallVoidMethodV(obj, GetObjectMethodIDOrAbort(obj, name, sig), argp);
    va_end(argp);
  }

  void CallVoidMethodOrAbort(jobject obj,
                             const char* name,
                             const char* sig,
                             ...) {
    va_list argp;
    va_start(argp, sig);
    CallVoidMethodVOrAbort(obj, GetObjectMethodIDOrAbort(obj, name, sig), argp);
    va_end(argp);
  }

  void CallVoidMethodVOrAbort(jobject obj, jmethodID methodID, va_list args) {
    CallVoidMethodV(obj, methodID, args);
    AbortOnException();
  }

  void CallStarboardVoidMethod(const char* name, const char* sig, ...) {
    va_list argp;
    va_start(argp, sig);
    jobject obj = GetStarboardBridge();
    CallVoidMethodV(obj, GetObjectMethodIDOrAbort(obj, name, sig), argp);
    va_end(argp);
  }

  void CallStarboardVoidMethodOrAbort(const char* name, const char* sig, ...) {
    va_list argp;
    va_start(argp, sig);
    jobject obj = GetStarboardBridge();
    CallVoidMethodVOrAbort(obj, GetObjectMethodIDOrAbort(obj, name, sig), argp);
    va_end(argp);
  }

  void CallStaticVoidMethod(const char* class_name,
                            const char* method_name,
                            const char* sig,
                            ...) {
    va_list argp;
    va_start(argp, sig);
    jclass clazz = FindClassExtOrAbort(class_name);
    CallStaticVoidMethodV(
        clazz, GetStaticMethodIDOrAbort(clazz, method_name, sig), argp);
    DeleteLocalRef(clazz);
    va_end(argp);
  }

  void CallStaticVoidMethodOrAbort(const char* class_name,
                                   const char* method_name,
                                   const char* sig,
                                   ...) {
    va_list argp;
    va_start(argp, sig);
    jclass clazz = FindClassExtOrAbort(class_name);
    CallStaticVoidMethodV(
        clazz, GetStaticMethodIDOrAbort(clazz, method_name, sig), argp);
    AbortOnException();
    DeleteLocalRef(clazz);
    va_end(argp);
  }

  jstring GetStringFieldOrAbort(jobject obj, const char* name) {
    return static_cast<jstring>(
        GetObjectFieldOrAbort(obj, name, "Ljava/lang/String;"));
  }

  jstring GetStaticStringFieldOrAbort(const char* class_name,
                                      const char* name) {
    return static_cast<jstring>(
        GetStaticObjectFieldOrAbort(class_name, name, "Ljava/lang/String;"));
  }

  jstring GetStaticStringFieldOrAbort(jclass clazz, const char* name) {
    return static_cast<jstring>(
        GetStaticObjectFieldOrAbort(clazz, name, "Ljava/lang/String;"));
  }

// Convenience method to create a j[Type]Array from raw, native data. It is
// the responsibility of clients to free the returned array when done with it
// by manually calling |DeleteLocalRef| on it.
#define X(_jtype, _jname)                                                   \
  _jtype##Array New##_jname##ArrayFromRaw(const _jtype* data, jsize size) { \
    SB_DCHECK(data);                                                        \
    SB_DCHECK(size >= 0);                                                   \
    _jtype##Array j_array = New##_jname##Array(size);                       \
    SB_CHECK(j_array) << "Out of memory making new array";                  \
    Set##_jname##ArrayRegion(j_array, 0, size, data);                       \
    return j_array;                                                         \
  }

  X(jboolean, Boolean)
  X(jbyte, Byte)
  X(jchar, Char)
  X(jshort, Short)
  X(jint, Int)
  X(jlong, Long)
  X(jfloat, Float)
  X(jdouble, Double)

#undef X

  jobject ConvertLocalRefToGlobalRef(jobject local) {
    jobject global = NewGlobalRef(local);
    DeleteLocalRef(local);
    return global;
  }

  void AbortOnException() {
    if (!ExceptionCheck()) {
      return;
    }
    ExceptionDescribe();
    SbSystemBreakIntoDebugger();
  }
};

SB_COMPILE_ASSERT(sizeof(JNIEnv) == sizeof(JniEnvExt),
                  JniEnvExt_must_not_add_fields);

}  // namespace shared
}  // namespace android
}  // namespace starboard

#endif  // STARBOARD_ANDROID_SHARED_JNI_ENV_EXT_H_