1 /*
2  * Copyright (C) 2018 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 package com.android.car;
18 
19 import android.annotation.Nullable;
20 import android.annotation.RawRes;
21 import android.content.Context;
22 
23 import java.io.BufferedReader;
24 import java.io.IOException;
25 import java.io.InputStream;
26 import java.io.InputStreamReader;
27 import java.io.Reader;
28 
29 /**
30  * An implementation of {@link com.android.car.CarConfigurationService.JsonReader} that will
31  * parse a JSON file on the system that is mapped to {@code R.raw.car_config}.
32  */
33 public class JsonReaderImpl implements CarConfigurationService.JsonReader {
34     private static final int BUF_SIZE = 0x1000; // 2K chars (4K bytes)
35     private static final String JSON_FILE_ENCODING = "UTF-8";
36 
37     /**
38      * Takes a resource file that is considered to be a JSON file and parses it into a String that
39      * is returned.
40      *
41      * @param resId The resource id pointing to the json file.
42      * @return A {@code String} representing the file contents, or {@code null} if
43      */
44     @Override
45     @Nullable
jsonFileToString(Context context, @RawRes int resId)46     public String jsonFileToString(Context context, @RawRes int resId) {
47         InputStream is = context.getResources().openRawResource(resId);
48 
49         // Note: this "try" will close the Reader, thus closing the associated InputStreamReader
50         // and InputStream.
51         try (Reader reader = new BufferedReader(new InputStreamReader(is, JSON_FILE_ENCODING))) {
52             char[] buffer = new char[BUF_SIZE];
53             StringBuilder stringBuilder = new StringBuilder();
54 
55             int bufferedContent;
56             while ((bufferedContent = reader.read(buffer)) != -1) {
57                 stringBuilder.append(buffer, /* offset= */ 0, bufferedContent);
58             }
59 
60             return stringBuilder.toString();
61         } catch (IOException e) {
62             return null;
63         }
64     }
65 }
66