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1: /* ChannelWriter.java -- nio / writer bridge 2: Copyright (C) 2006 Free Software Foundation, Inc. 3: 4: This file is part of GNU Classpath. 5: 6: GNU Classpath is free software; you can redistribute it and/or modify 7: it under the terms of the GNU General Public License as published by 8: the Free Software Foundation; either version 2, or (at your option) 9: any later version. 10: 11: GNU Classpath is distributed in the hope that it will be useful, but 12: WITHOUT ANY WARRANTY; without even the implied warranty of 13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14: General Public License for more details. 15: 16: You should have received a copy of the GNU General Public License 17: along with GNU Classpath; see the file COPYING. If not, write to the 18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 19: 02110-1301 USA. 20: 21: Linking this library statically or dynamically with other modules is 22: making a combined work based on this library. Thus, the terms and 23: conditions of the GNU General Public License cover the whole 24: combination. 25: 26: As a special exception, the copyright holders of this library give you 27: permission to link this library with independent modules to produce an 28: executable, regardless of the license terms of these independent 29: modules, and to copy and distribute the resulting executable under 30: terms of your choice, provided that you also meet, for each linked 31: independent module, the terms and conditions of the license of that 32: module. An independent module is a module which is not derived from 33: or based on this library. If you modify this library, you may extend 34: this exception to your version of the library, but you are not 35: obligated to do so. If you do not wish to do so, delete this 36: exception statement from your version. */ 37: 38: 39: package gnu.java.nio; 40: 41: import java.io.IOException; 42: import java.io.Writer; 43: import java.nio.ByteBuffer; 44: import java.nio.CharBuffer; 45: import java.nio.channels.WritableByteChannel; 46: import java.nio.charset.CharsetEncoder; 47: import java.nio.charset.CoderResult; 48: 49: /** 50: * A Writer implementation that works by wrapping an NIO channel. 51: */ 52: public class ChannelWriter 53: extends Writer 54: { 55: private static final int DEFAULT_BUFFER_CAP = 8192; 56: 57: /** 58: * The output channel. 59: */ 60: private WritableByteChannel byteChannel; 61: 62: /** 63: * The encoder to use. 64: */ 65: private CharsetEncoder enc; 66: 67: /** 68: * The byte buffer. Translated characters are stored here on their way out. 69: */ 70: private ByteBuffer byteBuffer; 71: 72: /** 73: * The character buffer. Characters are stored here on their way into 74: * the encoder. 75: */ 76: private CharBuffer charBuffer; 77: 78: private void writeBuffer() throws IOException 79: { 80: byteBuffer.flip(); 81: byteChannel.write(byteBuffer); 82: } 83: 84: /** 85: * Create a new instance, given the output byte channel, the encoder 86: * to use, and the minimum buffer capacity. 87: */ 88: public ChannelWriter(WritableByteChannel ch, CharsetEncoder enc, 89: int minBufferCap) 90: { 91: this.byteChannel = ch; 92: this.enc = enc; 93: if (minBufferCap == -1) 94: minBufferCap = DEFAULT_BUFFER_CAP; 95: this.byteBuffer 96: = ByteBuffer.allocate((int) (minBufferCap * enc.maxBytesPerChar())); 97: this.charBuffer = CharBuffer.allocate(minBufferCap); 98: this.charBuffer.clear(); 99: } 100: 101: /* (non-Javadoc) 102: * @see java.io.Writer#flush() 103: */ 104: public void flush() throws IOException 105: { 106: // Presumably if we have characters in our buffer, it is 107: // due to an underflow. So we don't bother trying to flush 108: // that here. 109: } 110: 111: /* (non-Javadoc) 112: * @see java.io.Writer#close() 113: */ 114: public void close() throws IOException 115: { 116: synchronized (lock) 117: { 118: if (enc == null) 119: throw new IOException("writer already closed"); 120: 121: byteBuffer.clear(); 122: charBuffer.flip(); 123: CoderResult res = enc.encode(charBuffer, byteBuffer, true); 124: if (res.isError() || res.isMalformed() || res.isUnmappable()) 125: res.throwException(); 126: writeBuffer(); 127: 128: byteBuffer.clear(); 129: res = enc.flush(byteBuffer); 130: if (res.isError() || res.isMalformed() || res.isUnmappable()) 131: res.throwException(); 132: writeBuffer(); 133: enc = null; 134: } 135: } 136: 137: /* (non-Javadoc) 138: * @see java.io.Writer#write(char[], int, int) 139: */ 140: public void write(char[] buf, int offset, int len) throws IOException 141: { 142: synchronized (lock) 143: { 144: if (enc == null) 145: throw new IOException("writer already closed"); 146: int lastLen = -1; 147: while (len > 0) 148: { 149: // Copy data into our character buffer. 150: int allowed = Math.min(charBuffer.remaining(), len); 151: charBuffer.put(buf, offset, allowed); 152: // Update for the next pass through the loop. 153: offset += allowed; 154: len -= allowed; 155: charBuffer.flip(); 156: // If we didn't make any progress, we want to clean up 157: // and save our state for the next write(). 158: if (len == lastLen) 159: { 160: if (len <= charBuffer.remaining()) 161: { 162: charBuffer.put(buf, offset, len); 163: charBuffer.flip(); 164: } 165: else 166: { 167: CharBuffer ncb = CharBuffer.allocate(charBuffer.length() 168: + len); 169: ncb.put(charBuffer); 170: ncb.put(buf, offset, len); 171: charBuffer = ncb; 172: } 173: break; 174: } 175: lastLen = len; 176: 177: // Convert. 178: byteBuffer.clear(); 179: CoderResult res = enc.encode(charBuffer, byteBuffer, false); 180: // Compact here, as we want to leave the buffer in the 181: // right state for any future put()s. 182: charBuffer.compact(); 183: if (res.isError() || res.isMalformed() || res.isUnmappable()) 184: res.throwException(); 185: // Write the byte buffer to the output channel. 186: writeBuffer(); 187: } 188: } 189: } 190: }