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 SCOPED_UTF_CHARS_H_ 18 #define SCOPED_UTF_CHARS_H_ 19 20 #include <string.h> 21 22 #include "jni.h" 23 #include "nativehelper_utils.h" 24 25 // A smart pointer that provides read-only access to a Java string's UTF chars. 26 // Unlike GetStringUTFChars, we throw NullPointerException rather than abort if 27 // passed a null jstring, and c_str will return nullptr. 28 // This makes the correct idiom very simple: 29 // 30 // ScopedUtfChars name(env, java_name); 31 // if (name.c_str() == nullptr) { 32 // return nullptr; 33 // } 34 class ScopedUtfChars { 35 public: ScopedUtfChars(JNIEnv * env,jstring s)36 ScopedUtfChars(JNIEnv* env, jstring s) : env_(env), string_(s) { 37 if (s == nullptr) { 38 utf_chars_ = nullptr; 39 jniThrowNullPointerException(env, nullptr); 40 } else { 41 utf_chars_ = env->GetStringUTFChars(s, nullptr); 42 } 43 } 44 ScopedUtfChars(ScopedUtfChars && rhs)45 ScopedUtfChars(ScopedUtfChars&& rhs) noexcept : 46 env_(rhs.env_), string_(rhs.string_), utf_chars_(rhs.utf_chars_) { 47 rhs.env_ = nullptr; 48 rhs.string_ = nullptr; 49 rhs.utf_chars_ = nullptr; 50 } 51 ~ScopedUtfChars()52 ~ScopedUtfChars() { 53 if (utf_chars_) { 54 env_->ReleaseStringUTFChars(string_, utf_chars_); 55 } 56 } 57 58 ScopedUtfChars& operator=(ScopedUtfChars&& rhs) noexcept { 59 if (this != &rhs) { 60 // Delete the currently owned UTF chars. 61 this->~ScopedUtfChars(); 62 63 // Move the rhs ScopedUtfChars and zero it out. 64 env_ = rhs.env_; 65 string_ = rhs.string_; 66 utf_chars_ = rhs.utf_chars_; 67 rhs.env_ = nullptr; 68 rhs.string_ = nullptr; 69 rhs.utf_chars_ = nullptr; 70 } 71 return *this; 72 } 73 c_str()74 const char* c_str() const { 75 return utf_chars_; 76 } 77 size()78 size_t size() const { 79 return strlen(utf_chars_); 80 } 81 82 const char& operator[](size_t n) const { 83 return utf_chars_[n]; 84 } 85 86 private: 87 JNIEnv* env_; 88 jstring string_; 89 const char* utf_chars_; 90 91 DISALLOW_COPY_AND_ASSIGN(ScopedUtfChars); 92 }; 93 94 #endif // SCOPED_UTF_CHARS_H_ 95