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