include/nativehelper/ScopedUtfChars.h

/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef SCOPED_UTF_CHARS_H_included
#define SCOPED_UTF_CHARS_H_included

#include "JNIHelp.h"
#include <string.h>

// A smart pointer that provides read-only access to a Java string's UTF chars.
// Unlike GetStringUTFChars, we throw NullPointerException rather than abort if
// passed a null jstring, and c_str will return NULL.
// This makes the correct idiom very simple:
//
//   ScopedUtfChars name(env, java_name);
//   if (name.c_str() == NULL) {
//     return NULL;
//   }
class ScopedUtfChars {
 public:
  ScopedUtfChars(JNIEnv* env, jstring s) : env_(env), string_(s) {
    if (s == NULL) {
      utf_chars_ = NULL;
      jniThrowNullPointerException(env, NULL);
    } else {
      utf_chars_ = env->GetStringUTFChars(s, NULL);
    }
  }

  ~ScopedUtfChars() {
    if (utf_chars_) {
      env_->ReleaseStringUTFChars(string_, utf_chars_);
    }
  }

  const char* c_str() const {
    return utf_chars_;
  }

  size_t size() const {
    return strlen(utf_chars_);
  }

  const char& operator[](size_t n) const {
    return utf_chars_[n];
  }

 private:
  JNIEnv* const env_;
  const jstring string_;
  const char* utf_chars_;

  DISALLOW_COPY_AND_ASSIGN(ScopedUtfChars);
};

#endif  // SCOPED_UTF_CHARS_H_included