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 NULL.
26 // This makes the correct idiom very simple:
27 //
28 //   ScopedUtfChars name(env, java_name);
29 //   if (name.c_str() == NULL) {
30 //     return NULL;
31 //   }
32 class ScopedUtfChars {
33  public:
ScopedUtfChars(JNIEnv * env,jstring s)34   ScopedUtfChars(JNIEnv* env, jstring s) : env_(env), string_(s) {
35     if (s == NULL) {
36       utf_chars_ = NULL;
37       jniThrowNullPointerException(env, NULL);
38     } else {
39       utf_chars_ = env->GetStringUTFChars(s, NULL);
40     }
41   }
42 
~ScopedUtfChars()43   ~ScopedUtfChars() {
44     if (utf_chars_) {
45       env_->ReleaseStringUTFChars(string_, utf_chars_);
46     }
47   }
48 
c_str()49   const char* c_str() const {
50     return utf_chars_;
51   }
52 
size()53   size_t size() const {
54     return strlen(utf_chars_);
55   }
56 
57   const char& operator[](size_t n) const {
58     return utf_chars_[n];
59   }
60 
61  private:
62   JNIEnv* env_;
63   jstring string_;
64   const char* utf_chars_;
65 
66   // Disallow copy and assignment.
67   ScopedUtfChars(const ScopedUtfChars&);
68   void operator=(const ScopedUtfChars&);
69 };
70 
71 #endif  // SCOPED_UTF_CHARS_H_included
72