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      1 /*
      2  * Copyright (C) 2015 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 package com.android.phone.common.mail;
     17 
     18 import java.util.HashMap;
     19 import java.util.Map;
     20 
     21 /**
     22  * A utility class for creating and modifying Strings that are tagged and packed together.
     23  *
     24  * Uses non-printable (control chars) for internal delimiters;  Intended for regular displayable
     25  * strings only, so please use base64 or other encoding if you need to hide any binary data here.
     26  *
     27  * Binary compatible with Address.pack() format, which should migrate to use this code.
     28  */
     29 public class PackedString {
     30 
     31     /**
     32      * Packing format is:
     33      *   element : [ value ] or [ value TAG-DELIMITER tag ]
     34      *   packed-string : [ element ] [ ELEMENT-DELIMITER [ element ] ]*
     35      */
     36     private static final char DELIMITER_ELEMENT = '\1';
     37     private static final char DELIMITER_TAG = '\2';
     38 
     39     private String mString;
     40     private HashMap<String, String> mExploded;
     41     private static final HashMap<String, String> EMPTY_MAP = new HashMap<String, String>();
     42 
     43     /**
     44      * Create a packed string using an already-packed string (e.g. from database)
     45      * @param string packed string
     46      */
     47     public PackedString(String string) {
     48         mString = string;
     49         mExploded = null;
     50     }
     51 
     52     /**
     53      * Get the value referred to by a given tag.  If the tag does not exist, return null.
     54      * @param tag identifier of string of interest
     55      * @return returns value, or null if no string is found
     56      */
     57     public String get(String tag) {
     58         if (mExploded == null) {
     59             mExploded = explode(mString);
     60         }
     61         return mExploded.get(tag);
     62     }
     63 
     64     /**
     65      * Return a map of all of the values referred to by a given tag.  This is a shallow
     66      * copy, don't edit the values.
     67      * @return a map of the values in the packed string
     68      */
     69     public Map<String, String> unpack() {
     70         if (mExploded == null) {
     71             mExploded = explode(mString);
     72         }
     73         return new HashMap<String,String>(mExploded);
     74     }
     75 
     76     /**
     77      * Read out all values into a map.
     78      */
     79     private static HashMap<String, String> explode(String packed) {
     80         if (packed == null || packed.length() == 0) {
     81             return EMPTY_MAP;
     82         }
     83         HashMap<String, String> map = new HashMap<String, String>();
     84 
     85         int length = packed.length();
     86         int elementStartIndex = 0;
     87         int elementEndIndex = 0;
     88         int tagEndIndex = packed.indexOf(DELIMITER_TAG);
     89 
     90         while (elementStartIndex < length) {
     91             elementEndIndex = packed.indexOf(DELIMITER_ELEMENT, elementStartIndex);
     92             if (elementEndIndex == -1) {
     93                 elementEndIndex = length;
     94             }
     95             String tag;
     96             String value;
     97             if (tagEndIndex == -1 || elementEndIndex <= tagEndIndex) {
     98                 // in this case the DELIMITER_PERSONAL is in a future pair (or not found)
     99                 // so synthesize a positional tag for the value, and don't update tagEndIndex
    100                 value = packed.substring(elementStartIndex, elementEndIndex);
    101                 tag = Integer.toString(map.size());
    102             } else {
    103                 value = packed.substring(elementStartIndex, tagEndIndex);
    104                 tag = packed.substring(tagEndIndex + 1, elementEndIndex);
    105                 // scan forward for next tag, if any
    106                 tagEndIndex = packed.indexOf(DELIMITER_TAG, elementEndIndex + 1);
    107             }
    108             map.put(tag, value);
    109             elementStartIndex = elementEndIndex + 1;
    110         }
    111 
    112         return map;
    113     }
    114 
    115     /**
    116      * Builder class for creating PackedString values.  Can also be used for editing existing
    117      * PackedString representations.
    118      */
    119     static public class Builder {
    120         HashMap<String, String> mMap;
    121 
    122         /**
    123          * Create a builder that's empty (for filling)
    124          */
    125         public Builder() {
    126             mMap = new HashMap<String, String>();
    127         }
    128 
    129         /**
    130          * Create a builder using the values of an existing PackedString (for editing).
    131          */
    132         public Builder(String packed) {
    133             mMap = explode(packed);
    134         }
    135 
    136         /**
    137          * Add a tagged value
    138          * @param tag identifier of string of interest
    139          * @param value the value to record in this position.  null to delete entry.
    140          */
    141         public void put(String tag, String value) {
    142             if (value == null) {
    143                 mMap.remove(tag);
    144             } else {
    145                 mMap.put(tag, value);
    146             }
    147         }
    148 
    149         /**
    150          * Get the value referred to by a given tag.  If the tag does not exist, return null.
    151          * @param tag identifier of string of interest
    152          * @return returns value, or null if no string is found
    153          */
    154         public String get(String tag) {
    155             return mMap.get(tag);
    156         }
    157 
    158         /**
    159          * Pack the values and return a single, encoded string
    160          */
    161         @Override
    162         public String toString() {
    163             StringBuilder sb = new StringBuilder();
    164             for (Map.Entry<String,String> entry : mMap.entrySet()) {
    165                 if (sb.length() > 0) {
    166                     sb.append(DELIMITER_ELEMENT);
    167                 }
    168                 sb.append(entry.getValue());
    169                 sb.append(DELIMITER_TAG);
    170                 sb.append(entry.getKey());
    171             }
    172             return sb.toString();
    173         }
    174     }
    175 }
    176