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1 /* |
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2 * Copyright 1996-2005 Sun Microsystems, Inc. All Rights Reserved. |
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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4 * |
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5 * This code is free software; you can redistribute it and/or modify it |
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6 * under the terms of the GNU General Public License version 2 only, as |
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7 * published by the Free Software Foundation. Sun designates this |
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8 * particular file as subject to the "Classpath" exception as provided |
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9 * by Sun in the LICENSE file that accompanied this code. |
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10 * |
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11 * This code is distributed in the hope that it will be useful, but WITHOUT |
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12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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14 * version 2 for more details (a copy is included in the LICENSE file that |
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15 * accompanied this code). |
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16 * |
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17 * You should have received a copy of the GNU General Public License version |
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18 * 2 along with this work; if not, write to the Free Software Foundation, |
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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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20 * |
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21 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
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22 * CA 95054 USA or visit www.sun.com if you need additional information or |
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23 * have any questions. |
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24 */ |
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25 |
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26 package java.io; |
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27 |
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28 /** |
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29 * This class implements a character buffer that can be used as a |
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30 * character-input stream. |
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31 * |
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32 * @author Herb Jellinek |
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33 * @since JDK1.1 |
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34 */ |
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35 public class CharArrayReader extends Reader { |
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36 /** The character buffer. */ |
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37 protected char buf[]; |
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38 |
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39 /** The current buffer position. */ |
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40 protected int pos; |
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41 |
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42 /** The position of mark in buffer. */ |
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43 protected int markedPos = 0; |
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44 |
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45 /** |
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46 * The index of the end of this buffer. There is not valid |
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47 * data at or beyond this index. |
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48 */ |
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49 protected int count; |
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50 |
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51 /** |
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52 * Creates a CharArrayReader from the specified array of chars. |
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53 * @param buf Input buffer (not copied) |
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54 */ |
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55 public CharArrayReader(char buf[]) { |
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56 this.buf = buf; |
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57 this.pos = 0; |
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58 this.count = buf.length; |
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59 } |
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60 |
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61 /** |
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62 * Creates a CharArrayReader from the specified array of chars. |
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63 * |
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64 * <p> The resulting reader will start reading at the given |
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65 * <tt>offset</tt>. The total number of <tt>char</tt> values that can be |
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66 * read from this reader will be either <tt>length</tt> or |
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67 * <tt>buf.length-offset</tt>, whichever is smaller. |
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68 * |
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69 * @throws IllegalArgumentException |
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70 * If <tt>offset</tt> is negative or greater than |
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71 * <tt>buf.length</tt>, or if <tt>length</tt> is negative, or if |
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72 * the sum of these two values is negative. |
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73 * |
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74 * @param buf Input buffer (not copied) |
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75 * @param offset Offset of the first char to read |
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76 * @param length Number of chars to read |
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77 */ |
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78 public CharArrayReader(char buf[], int offset, int length) { |
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79 if ((offset < 0) || (offset > buf.length) || (length < 0) || |
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80 ((offset + length) < 0)) { |
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81 throw new IllegalArgumentException(); |
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82 } |
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83 this.buf = buf; |
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84 this.pos = offset; |
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85 this.count = Math.min(offset + length, buf.length); |
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86 this.markedPos = offset; |
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87 } |
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88 |
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89 /** Checks to make sure that the stream has not been closed */ |
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90 private void ensureOpen() throws IOException { |
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91 if (buf == null) |
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92 throw new IOException("Stream closed"); |
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93 } |
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94 |
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95 /** |
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96 * Reads a single character. |
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97 * |
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98 * @exception IOException If an I/O error occurs |
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99 */ |
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100 public int read() throws IOException { |
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101 synchronized (lock) { |
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102 ensureOpen(); |
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103 if (pos >= count) |
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104 return -1; |
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105 else |
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106 return buf[pos++]; |
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107 } |
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108 } |
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109 |
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110 /** |
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111 * Reads characters into a portion of an array. |
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112 * @param b Destination buffer |
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113 * @param off Offset at which to start storing characters |
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114 * @param len Maximum number of characters to read |
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115 * @return The actual number of characters read, or -1 if |
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116 * the end of the stream has been reached |
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117 * |
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118 * @exception IOException If an I/O error occurs |
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119 */ |
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120 public int read(char b[], int off, int len) throws IOException { |
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121 synchronized (lock) { |
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122 ensureOpen(); |
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123 if ((off < 0) || (off > b.length) || (len < 0) || |
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124 ((off + len) > b.length) || ((off + len) < 0)) { |
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125 throw new IndexOutOfBoundsException(); |
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126 } else if (len == 0) { |
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127 return 0; |
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128 } |
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129 |
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130 if (pos >= count) { |
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131 return -1; |
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132 } |
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133 if (pos + len > count) { |
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134 len = count - pos; |
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135 } |
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136 if (len <= 0) { |
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137 return 0; |
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138 } |
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139 System.arraycopy(buf, pos, b, off, len); |
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140 pos += len; |
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141 return len; |
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142 } |
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143 } |
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144 |
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145 /** |
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146 * Skips characters. Returns the number of characters that were skipped. |
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147 * |
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148 * <p>The <code>n</code> parameter may be negative, even though the |
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149 * <code>skip</code> method of the {@link Reader} superclass throws |
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150 * an exception in this case. If <code>n</code> is negative, then |
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151 * this method does nothing and returns <code>0</code>. |
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152 * |
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153 * @param n The number of characters to skip |
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154 * @return The number of characters actually skipped |
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155 * @exception IOException If the stream is closed, or an I/O error occurs |
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156 */ |
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157 public long skip(long n) throws IOException { |
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158 synchronized (lock) { |
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159 ensureOpen(); |
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160 if (pos + n > count) { |
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161 n = count - pos; |
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162 } |
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163 if (n < 0) { |
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164 return 0; |
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165 } |
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166 pos += n; |
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167 return n; |
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168 } |
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169 } |
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170 |
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171 /** |
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172 * Tells whether this stream is ready to be read. Character-array readers |
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173 * are always ready to be read. |
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174 * |
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175 * @exception IOException If an I/O error occurs |
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176 */ |
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177 public boolean ready() throws IOException { |
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178 synchronized (lock) { |
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179 ensureOpen(); |
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180 return (count - pos) > 0; |
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181 } |
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182 } |
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183 |
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184 /** |
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185 * Tells whether this stream supports the mark() operation, which it does. |
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186 */ |
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187 public boolean markSupported() { |
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188 return true; |
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189 } |
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190 |
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191 /** |
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192 * Marks the present position in the stream. Subsequent calls to reset() |
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193 * will reposition the stream to this point. |
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194 * |
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195 * @param readAheadLimit Limit on the number of characters that may be |
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196 * read while still preserving the mark. Because |
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197 * the stream's input comes from a character array, |
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198 * there is no actual limit; hence this argument is |
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199 * ignored. |
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200 * |
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201 * @exception IOException If an I/O error occurs |
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202 */ |
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203 public void mark(int readAheadLimit) throws IOException { |
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204 synchronized (lock) { |
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205 ensureOpen(); |
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206 markedPos = pos; |
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207 } |
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208 } |
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209 |
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210 /** |
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211 * Resets the stream to the most recent mark, or to the beginning if it has |
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212 * never been marked. |
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213 * |
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214 * @exception IOException If an I/O error occurs |
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215 */ |
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216 public void reset() throws IOException { |
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217 synchronized (lock) { |
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218 ensureOpen(); |
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219 pos = markedPos; |
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220 } |
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221 } |
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222 |
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223 /** |
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224 * Closes the stream and releases any system resources associated with |
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225 * it. Once the stream has been closed, further read(), ready(), |
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226 * mark(), reset(), or skip() invocations will throw an IOException. |
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227 * Closing a previously closed stream has no effect. |
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228 */ |
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229 public void close() { |
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230 buf = null; |
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231 } |
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232 } |