mcs/class/corlib/System.IO/BufferedStream.cs

   1 //
   2 // System.IO.BufferedStream
   3 //
   4 // Author:
   5 //   Matt Kimball (matt@kimball.net)
   6 //   Ville Palo <vi64pa@kolumbus.fi>
   7 //
   8 // Copyright (C) 2004 Novell (http://www.novell.com)
   9 //
  10
  11 //
  12 // Copyright (C) 2004 Novell, Inc (http://www.novell.com)
  13 //
  14 // Permission is hereby granted, free of charge, to any person obtaining
  15 // a copy of this software and associated documentation files (the
  16 // "Software"), to deal in the Software without restriction, including
  17 // without limitation the rights to use, copy, modify, merge, publish,
  18 // distribute, sublicense, and/or sell copies of the Software, and to
  19 // permit persons to whom the Software is furnished to do so, subject to
  20 // the following conditions:
  21 //
  22 // The above copyright notice and this permission notice shall be
  23 // included in all copies or substantial portions of the Software.
  24 //
  25 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  26 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  27 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  28 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  29 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  30 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  31 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  32 //
  33
  34 using System.Globalization;
  35 using System.Runtime.InteropServices;
  36
  37 namespace System.IO {
  38         public sealed class BufferedStream : Stream {
  39                 Stream m_stream;
  40                 byte[] m_buffer;
  41                 int m_buffer_pos;
  42                 int m_buffer_read_ahead;
  43                 bool m_buffer_reading;
  44                 private bool disposed = false;
  45
  46                 public BufferedStream (Stream stream) : this (stream, 4096)
  47                 {
  48                 }
  49
  50                 public BufferedStream (Stream stream, int buffer_size)
  51                 {
  52                         if (stream == null)
  53                                 throw new ArgumentNullException ("stream");
  54                         // LAMESPEC: documented as < 0
  55                         if (buffer_size <= 0)
  56                                 throw new ArgumentOutOfRangeException ("buffer_size", "<= 0");
  57                         if (!stream.CanRead && !stream.CanWrite) {
  58                                 throw new ObjectDisposedException (
  59                                         Locale.GetText ("Cannot access a closed Stream."));
  60                         }
  61
  62                         m_stream = stream;
  63                         m_buffer = new byte [buffer_size];
  64                 }
  65
  66                 public override bool CanRead {
  67                         get {
  68                                 return m_stream.CanRead;
  69                         }
  70                 }
  71
  72                 public override bool CanWrite {
  73                         get {
  74                                 return m_stream.CanWrite;
  75                         }
  76                 }
  77
  78                 public override bool CanSeek {
  79                         get {
  80                                 return m_stream.CanSeek;
  81                         }
  82                 }
  83
  84                 public override long Length {
  85                         get {
  86                                 Flush ();
  87                                 return m_stream.Length;
  88                         }
  89                 }
  90
  91                 public override long Position {
  92                         get {
  93                                 CheckObjectDisposedException ();
  94                                 return m_stream.Position - m_buffer_read_ahead + m_buffer_pos;
  95                         }
  96
  97                         set {
  98                                 if (value < Position && (Position - value <= m_buffer_pos) && m_buffer_reading) {
  99                                         m_buffer_pos -= (int) (Position - value);
 100                                 }
 101                                 else if (value > Position && (value - Position < m_buffer_read_ahead - m_buffer_pos) && m_buffer_reading) {
 102                                         m_buffer_pos += (int) (value - Position);
 103                                 }
 104                                 else {
 105                                         Flush();
 106                                         m_stream.Position = value;
 107                                 }
 108                         }
 109                 }
 110
 111                 public override void Close ()
 112                 {
 113                         if (m_buffer != null)
 114                                 Flush();
 115
 116                         m_stream.Close();
 117                         m_buffer = null;
 118                         disposed = true;
 119                 }
 120
 121                 public override void Flush ()
 122                 {
 123                         CheckObjectDisposedException ();
 124
 125                         if (m_buffer_reading) {
 126                                 if (CanSeek)
 127                                         m_stream.Position = Position;
 128                         } else if (m_buffer_pos > 0) {
 129                                 m_stream.Write(m_buffer, 0, m_buffer_pos);
 130                         }
 131
 132                         m_buffer_read_ahead = 0;
 133                         m_buffer_pos = 0;
 134                 }
 135
 136                 public override long Seek (long offset, SeekOrigin origin)
 137                 {
 138                         CheckObjectDisposedException ();
 139                         if (!CanSeek) {
 140                                 throw new NotSupportedException (
 141                                         Locale.GetText ("Non seekable stream."));
 142                         }
 143                         Flush ();
 144                         return m_stream.Seek (offset, origin);
 145                 }
 146
 147                 public override void SetLength (long value)
 148                 {
 149                         CheckObjectDisposedException ();
 150
 151                         if (value < 0)
 152                                 throw new ArgumentOutOfRangeException ("value must be positive");
 153
 154                         if (!m_stream.CanWrite && !m_stream.CanSeek)
 155                                 throw new NotSupportedException ("the stream cannot seek nor write.");
 156
 157                         if ((m_stream == null) || (!m_stream.CanRead && !m_stream.CanWrite))
 158                                 throw new IOException ("the stream is not open");
 159
 160                         m_stream.SetLength(value);
 161                         if (Position > value)
 162                                 Position = value;
 163                 }
 164
 165                 public override int ReadByte ()
 166                 {
 167                         CheckObjectDisposedException ();
 168
 169                         byte[] b = new byte[1];
 170
 171                         if (Read(b, 0, 1) == 1) {
 172                                 return b[0];
 173                         } else {
 174                                 return -1;
 175                         }
 176                 }
 177
 178                 public override void WriteByte (byte value)
 179                 {
 180                         CheckObjectDisposedException ();
 181                         byte[] b = new byte[1];
 182
 183                         b[0] = value;
 184                         Write(b, 0, 1);
 185                 }
 186
 187                 public override int Read ([In,Out] byte[] array, int offset, int count)
 188                 {
 189                         if (array == null)
 190                                 throw new ArgumentNullException ("array");
 191                         CheckObjectDisposedException ();
 192                         if (!m_stream.CanRead) {
 193                                 throw new NotSupportedException (
 194                                         Locale.GetText ("Cannot read from stream"));
 195                         }
 196                         if (offset < 0)
 197                                 throw new ArgumentOutOfRangeException ("offset", "< 0");
 198                         if (count < 0)
 199                                 throw new ArgumentOutOfRangeException ("count", "< 0");
 200                         // re-ordered to avoid possible integer overflow
 201                         if (array.Length - offset < count)
 202                                 throw new ArgumentException ("array.Length - offset < count");
 203
 204                         if (!m_buffer_reading) {
 205                                 Flush();
 206                                 m_buffer_reading = true;
 207                         }
 208
 209                         if (count <= m_buffer_read_ahead - m_buffer_pos) {
 210                                 Array.Copy(m_buffer, m_buffer_pos, array, offset, count);
 211
 212                                 m_buffer_pos += count;
 213                                 if (m_buffer_pos == m_buffer_read_ahead) {
 214                                         m_buffer_pos = 0;
 215                                         m_buffer_read_ahead = 0;
 216                                 }
 217
 218                                 return count;
 219                         }
 220
 221                         int ret = m_buffer_read_ahead - m_buffer_pos;
 222                         Array.Copy(m_buffer, m_buffer_pos, array, offset, ret);
 223                         m_buffer_pos = 0;
 224                         m_buffer_read_ahead = 0;
 225                         offset += ret;
 226                         count -= ret;
 227
 228                         if (count >= m_buffer.Length) {
 229                                 ret += m_stream.Read(array, offset, count);
 230                         } else {
 231                                 m_buffer_read_ahead = m_stream.Read(m_buffer, 0, m_buffer.Length);
 232
 233                                 if (count < m_buffer_read_ahead) {
 234                                         Array.Copy(m_buffer, 0, array, offset, count);
 235                                         m_buffer_pos = count;
 236                                         ret += count;
 237                                 } else {
 238                                         Array.Copy(m_buffer, 0, array, offset, m_buffer_read_ahead);
 239                                         ret += m_buffer_read_ahead;
 240                                         m_buffer_read_ahead = 0;
 241                                 }
 242                         }
 243
 244                         return ret;
 245                 }
 246
 247                 public override void Write (byte[] array, int offset, int count)
 248                 {
 249                         if (array == null)
 250                                 throw new ArgumentNullException ("array");
 251                         CheckObjectDisposedException ();
 252                         if (!m_stream.CanWrite) {
 253                                 throw new NotSupportedException (
 254                                         Locale.GetText ("Cannot write to stream"));
 255                         }
 256                         if (offset < 0)
 257                                 throw new ArgumentOutOfRangeException ("offset", "< 0");
 258                         if (count < 0)
 259                                 throw new ArgumentOutOfRangeException ("count", "< 0");
 260                         // avoid possible integer overflow
 261                         if (array.Length - offset < count)
 262                                 throw new ArgumentException ("array.Length - offset < count");
 263
 264                         if (m_buffer_reading) {
 265                                 Flush();
 266                                 m_buffer_reading = false;
 267                         }
 268
 269                         // reordered to avoid possible integer overflow
 270                         if (m_buffer_pos >= m_buffer.Length - count) {
 271                                 Flush ();
 272                                 m_stream.Write (array, offset, count);
 273                         }
 274                         else {
 275                                 Array.Copy (array, offset, m_buffer, m_buffer_pos, count);
 276                                 m_buffer_pos += count;
 277                         }
 278                 }
 279
 280                 private void CheckObjectDisposedException ()
 281                 {
 282                         if (disposed) {
 283                                 throw new ObjectDisposedException ("BufferedStream",
 284                                         Locale.GetText ("Stream is closed"));
 285                         }
 286                 }
 287         }
 288 }