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1 /*
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2 * ConnectBot: simple, powerful, open-source SSH client for Android
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3 * Copyright 2007 Kenny Root, Jeffrey Sharkey
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4 *
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5 * Licensed under the Apache License, Version 2.0 (the "License");
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6 * you may not use this file except in compliance with the License.
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7 * You may obtain a copy of the License at
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8 *
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9 * http://www.apache.org/licenses/LICENSE-2.0
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10 *
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11 * Unless required by applicable law or agreed to in writing, software
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12 * distributed under the License is distributed on an "AS IS" BASIS,
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13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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14 * See the License for the specific language governing permissions and
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15 * limitations under the License.
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16 */
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17
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18 package com.five_ten_sg.connectbot.service;
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19
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20 import java.util.concurrent.Semaphore;
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21
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22 import android.os.Handler;
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23 import android.os.Message;
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24
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25 /**
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26 * Helps provide a relay for prompts and responses between a possible user
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27 * interface and some underlying service.
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28 *
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29 * @author jsharkey
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30 */
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31 public class PromptHelper {
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32 private final Object tag;
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33
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34 private Handler handler = null;
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35
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36 private Semaphore promptToken;
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37 private Semaphore promptResponse;
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38
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39 public String promptInstructions = null;
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40 public String promptHint = null;
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41 public Object promptRequested = null;
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42 public boolean passwordRequested = true;
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43
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44 private Object response = null;
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45
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46 public PromptHelper(Object tag) {
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47 this.tag = tag;
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48 // Threads must acquire this before they can send a prompt.
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49 promptToken = new Semaphore(1);
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50 // Responses will release this semaphore.
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51 promptResponse = new Semaphore(0);
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52 }
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53
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54
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55 /**
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56 * Register a user interface handler, if available.
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57 */
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58 public void setHandler(Handler handler) {
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59 this.handler = handler;
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60 }
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61
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62 /**
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63 * Set an incoming value from an above user interface. Will automatically
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64 * notify any waiting requests.
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65 */
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66 public void setResponse(Object value) {
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67 response = value;
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68 promptRequested = null;
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69 promptInstructions = null;
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70 promptHint = null;
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71 promptResponse.release();
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72 }
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73
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74 /**
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75 * Return the internal response value just before erasing and returning it.
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76 */
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77 protected Object popResponse() {
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78 Object value = response;
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79 response = null;
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80 return value;
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81 }
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82
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83
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84 /**
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85 * Request a prompt response from parent. This is a blocking call until user
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86 * interface returns a value.
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87 * Only one thread can call this at a time. cancelPrompt() will force this to
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88 * immediately return.
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89 */
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90 private Object requestPrompt(String instructions, String hint, Object type) throws InterruptedException {
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91 Object response = null;
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92 promptToken.acquire();
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93
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94 try {
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95 promptInstructions = instructions;
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96 promptHint = hint;
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97 promptRequested = type;
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98
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99 // notify any parent watching for live events
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100 if (handler != null)
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101 Message.obtain(handler, -1, tag).sendToTarget();
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102
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103 // acquire lock until user passes back value
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104 promptResponse.acquire();
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105 response = popResponse();
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106 }
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107 finally {
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108 promptToken.release();
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109 }
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110
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111 return response;
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112 }
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113
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114 /**
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115 * Request a string response from parent. This is a blocking call until user
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116 * interface returns a value.
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117 * @param hint prompt hint for user to answer
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118 * @return string user has entered
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119 */
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120 public String requestStringPrompt(String instructions, String hint) {
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121 String value = null;
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122 passwordRequested = false;
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123
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124 try {
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125 value = (String)this.requestPrompt(instructions, hint, String.class);
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126 }
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127 catch (Exception e) {
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128 }
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129
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130 return value;
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131 }
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132
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133 /**
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134 * Request a password response from parent. This is a blocking call until user
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135 * interface returns a value.
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136 * @param hint prompt hint for user to answer
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137 * @return string user has entered
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138 */
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139 public String requestPasswordPrompt(String instructions, String hint) {
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140 String value = null;
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141 passwordRequested = true;
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142
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143 try {
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144 value = (String)this.requestPrompt(instructions, hint, String.class);
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145 }
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146 catch (Exception e) {
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147 }
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148
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149 return value;
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150 }
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151
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152 /**
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153 * Request a boolean response from parent. This is a blocking call until user
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154 * interface returns a value.
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155 * @param hint prompt hint for user to answer
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156 * @return choice user has made (yes/no)
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157 */
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158 public Boolean requestBooleanPrompt(String instructions, String hint) {
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159 Boolean value = null;
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160
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161 try {
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162 value = (Boolean)this.requestPrompt(instructions, hint, Boolean.class);
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163 }
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164 catch (Exception e) {
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165 }
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166
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167 return value;
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168 }
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169
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170 /**
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171 * Cancel an in-progress prompt.
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172 */
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173 public void cancelPrompt() {
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174 if (!promptToken.tryAcquire()) {
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175 // A thread has the token, so try to interrupt it
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176 response = null;
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177 promptResponse.release();
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178 }
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179 else {
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180 // No threads have acquired the token
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181 promptToken.release();
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182 }
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183 }
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184 }
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