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      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, javaName);
     29 //   if (name.c_str() == NULL) {
     30 //       return NULL;
     31 //   }
     32 class ScopedUtfChars {
     33 public:
     34     ScopedUtfChars(JNIEnv* env, jstring s)
     35     : mEnv(env), mString(s)
     36     {
     37         if (s == NULL) {
     38             mUtfChars = NULL;
     39             jniThrowNullPointerException(env, NULL);
     40         } else {
     41             mUtfChars = env->GetStringUTFChars(s, NULL);
     42         }
     43     }
     44 
     45     ~ScopedUtfChars() {
     46         if (mUtfChars) {
     47             mEnv->ReleaseStringUTFChars(mString, mUtfChars);
     48         }
     49     }
     50 
     51     const char* c_str() const {
     52         return mUtfChars;
     53     }
     54 
     55     size_t size() const {
     56         return strlen(mUtfChars);
     57     }
     58 
     59     // Element access.
     60     const char& operator[](size_t n) const {
     61         return mUtfChars[n];
     62     }
     63 
     64 private:
     65     JNIEnv* mEnv;
     66     jstring mString;
     67     const char* mUtfChars;
     68 
     69     // Disallow copy and assignment.
     70     ScopedUtfChars(const ScopedUtfChars&);
     71     void operator=(const ScopedUtfChars&);
     72 };
     73 
     74 #endif  // SCOPED_UTF_CHARS_H_included
     75