1 /* 2 * Copyright (C) 2011 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 #pragma once 18 19 #include <stddef.h> 20 21 #include <jni.h> 22 23 #include "nativehelper_utils.h" 24 25 // A smart pointer that provides access to a jchar* given a JNI jstring. 26 // Unlike GetStringChars, we throw NullPointerException rather than abort if 27 // passed a null jstring, and get will return nullptr. 28 // This makes the correct idiom very simple: 29 // 30 // ScopedStringChars name(env, java_name); 31 // if (name.get() == nullptr) { 32 // return nullptr; 33 // } 34 class ScopedStringChars { 35 public: ScopedStringChars(JNIEnv * env,jstring s)36 ScopedStringChars(JNIEnv* env, jstring s) : env_(env), string_(s), size_(0) { 37 if (s == nullptr) { 38 chars_ = nullptr; 39 jniThrowNullPointerException(env); 40 } else { 41 chars_ = env->GetStringChars(string_, nullptr); 42 if (chars_ != nullptr) { 43 size_ = env->GetStringLength(string_); 44 } 45 } 46 } 47 ~ScopedStringChars()48 ~ScopedStringChars() { 49 if (chars_ != nullptr) { 50 env_->ReleaseStringChars(string_, chars_); 51 } 52 } 53 get()54 const jchar* get() const { 55 return chars_; 56 } 57 size()58 size_t size() const { 59 return size_; 60 } 61 62 const jchar& operator[](size_t n) const { 63 return chars_[n]; 64 } 65 66 private: 67 JNIEnv* const env_; 68 const jstring string_; 69 const jchar* chars_; 70 size_t size_; 71 72 DISALLOW_COPY_AND_ASSIGN(ScopedStringChars); 73 }; 74 75