1 /* CompressedOutputStream.java -- 2 Copyright (C) 2003, 2004 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.net.protocol.ftp; 40 41 import java.io.IOException; 42 import java.io.OutputStream; 43 44 /** 45 * A DTP output stream that implements the FTP compressed transfer mode. 46 * 47 * @author Chris Burdess (dog@gnu.org) 48 */ 49 class CompressedOutputStream 50 extends DTPOutputStream 51 { 52 53 static final byte RECORD = -128; // 0x80 54 static final byte EOF = 64; // 0x40 55 CompressedOutputStream(DTP dtp, OutputStream out)56 CompressedOutputStream(DTP dtp, OutputStream out) 57 { 58 super(dtp, out); 59 } 60 61 /** 62 * Just one byte cannot be compressed. 63 * It takes 5 bytes to transmit - hardly very compressed! 64 */ write(int c)65 public void write(int c) 66 throws IOException 67 { 68 if (transferComplete) 69 { 70 return; 71 } 72 byte[] buf = new byte[] 73 { 74 RECORD, /* record descriptor */ 75 0x00, 0x01, /* one byte */ 76 0x01, /* one uncompressed byte */ 77 (byte) c /* the byte */ 78 }; 79 out.write(buf, 0, 5); 80 } 81 write(byte[] b)82 public void write(byte[] b) 83 throws IOException 84 { 85 write(b, 0, b.length); 86 } 87 88 /** 89 * The larger len is, the better. 90 */ write(byte[] b, int off, int len)91 public void write(byte[] b, int off, int len) 92 throws IOException 93 { 94 if (transferComplete) 95 { 96 return; 97 } 98 byte[] buf = compress(b, off, len); 99 len = buf.length; 100 buf[0] = RECORD; /* record descriptor */ 101 buf[1] = (byte) ((len & 0x00ff) >> 8); /* high byte of bytecount */ 102 buf[2] = (byte) (len & 0xff00); /* low byte of bytecount */ 103 out.write(buf, 0, len); 104 } 105 106 /** 107 * Returns the compressed form of the given byte array. 108 * The first 3 bytes are left free for header information. 109 */ compress(byte[] b, int off, int len)110 byte[] compress(byte[] b, int off, int len) 111 { 112 byte[] buf = new byte[len]; 113 byte last = 0; 114 int pos = 0, raw_count = 0, rep_count = 1; 115 for (int i = off; i < len; i++) 116 { 117 byte c = b[i]; 118 if (i > off && c == last) // compress 119 { 120 if (raw_count > 0) // flush raw bytes to buf 121 { 122 // need to add raw_count+1 bytes 123 if (pos + (raw_count + 1) > buf.length) 124 { 125 buf = realloc(buf, len); 126 } 127 pos = flush_raw(buf, pos, b, (i - raw_count) - 1, 128 raw_count); 129 raw_count = 0; 130 } 131 rep_count++; // keep looking for same byte 132 } 133 else 134 { 135 if (rep_count > 1) // flush compressed bytes to buf 136 { 137 // need to add 2 bytes 138 if (pos + 2 > buf.length) 139 { 140 buf = realloc(buf, len); 141 } 142 pos = flush_compressed(buf, pos, rep_count, last); 143 rep_count = 1; 144 } 145 raw_count++; // keep looking for raw bytes 146 } 147 if (rep_count == 127) // flush compressed bytes 148 { 149 // need to add 2 bytes 150 if (pos + 2 > buf.length) 151 { 152 buf = realloc(buf, len); 153 } 154 pos = flush_compressed(buf, pos, rep_count, last); 155 rep_count = 1; 156 } 157 if (raw_count == 127) // flush raw bytes 158 { 159 // need to add raw_count+1 bytes 160 if (pos + (raw_count + 1) > buf.length) 161 { 162 buf = realloc(buf, len); 163 } 164 pos = flush_raw(buf, pos, b, (i - raw_count), raw_count); 165 raw_count = 0; 166 } 167 last = c; 168 } 169 if (rep_count > 1) // flush compressed bytes 170 { 171 // need to add 2 bytes 172 if (pos + 2 > buf.length) 173 { 174 buf = realloc(buf, len); 175 } 176 pos = flush_compressed(buf, pos, rep_count, last); 177 rep_count = 1; 178 } 179 if (raw_count > 0) // flush raw bytes 180 { 181 // need to add raw_count+1 bytes 182 if (pos + (raw_count + 1) > buf.length) 183 { 184 buf = realloc(buf, len); 185 } 186 pos = flush_raw(buf, pos, b, (len - raw_count), raw_count); 187 raw_count = 0; 188 } 189 byte[] ret = new byte[pos + 3]; 190 System.arraycopy(buf, 0, ret, 3, pos); 191 return ret; 192 } 193 flush_compressed(byte[] buf, int pos, int count, byte c)194 int flush_compressed(byte[] buf, int pos, int count, byte c) 195 { 196 buf[pos++] = (byte) (0x80 | count); 197 buf[pos++] = c; 198 return pos; 199 } 200 flush_raw(byte[] buf, int pos, byte[] src, int off, int len)201 int flush_raw(byte[] buf, int pos, byte[] src, int off, int len) 202 { 203 buf[pos++] = (byte) len; 204 System.arraycopy(src, off, buf, pos, len); 205 return pos + len; 206 } 207 realloc(byte[] buf, int len)208 byte[] realloc(byte[] buf, int len) 209 { 210 byte[] ret = new byte[buf.length + len]; 211 System.arraycopy(buf, 0, ret, 0, buf.length); 212 return ret; 213 } 214 close()215 public void close() 216 throws IOException 217 { 218 byte[] buf = new byte[] 219 { 220 EOF, /* eof descriptor */ 221 0x00, 0x00 /* no bytes */ 222 }; 223 out.write(buf, 0, 3); 224 out.close(); 225 } 226 227 } 228