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