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 using System.Globalization;
  12 using System.Runtime.InteropServices;
  13
  14 namespace System.IO {
  15         public sealed class BufferedStream : Stream {
  16                 Stream m_stream;
  17                 byte[] m_buffer;
  18                 int m_buffer_pos;
  19                 int m_buffer_read_ahead;
  20                 bool m_buffer_reading;
  21                 private bool disposed = false;
  22
  23                 public BufferedStream (Stream stream) : this (stream, 4096)
  24                 {
  25                 }
  26
  27                 public BufferedStream (Stream stream, int buffer_size)
  28                 {
  29                         if (stream == null)
  30                                 throw new ArgumentNullException ("stream");
  31                         // LAMESPEC: documented as < 0
  32                         if (buffer_size <= 0)
  33                                 throw new ArgumentOutOfRangeException ("buffer_size", "<= 0");
  34                         if (!stream.CanRead && !stream.CanWrite) {
  35                                 throw new ObjectDisposedException (
  36                                         Locale.GetText ("Cannot access a closed Stream."));
  37                         }
  38
  39                         m_stream = stream;
  40                         m_buffer = new byte [buffer_size];
  41                 }
  42
  43                 public override bool CanRead {
  44                         get {
  45                                 return m_stream.CanRead;
  46                         }
  47                 }
  48
  49                 public override bool CanWrite {
  50                         get {
  51                                 return m_stream.CanWrite;
  52                         }
  53                 }
  54
  55                 public override bool CanSeek {
  56                         get {
  57                                 return m_stream.CanSeek;
  58                         }
  59                 }
  60
  61                 public override long Length {
  62                         get {
  63                                 Flush ();
  64                                 return m_stream.Length;
  65                         }
  66                 }
  67
  68                 public override long Position {
  69                         get {
  70                                 CheckObjectDisposedException ();
  71                                 return m_stream.Position - m_buffer_read_ahead + m_buffer_pos;
  72                         }
  73
  74                         set {
  75                                 if (value < Position && (Position - value <= m_buffer_pos) && m_buffer_reading) {
  76                                         m_buffer_pos -= (int) (Position - value);
  77                                 }
  78                                 else if (value > Position && (value - Position < m_buffer_read_ahead - m_buffer_pos) && m_buffer_reading) {
  79                                         m_buffer_pos += (int) (value - Position);
  80                                 }
  81                                 else {
  82                                         Flush();
  83                                         m_stream.Position = value;
  84                                 }
  85                         }
  86                 }
  87
  88                 public override void Close ()
  89                 {
  90                         if (m_buffer != null)
  91                                 Flush();
  92
  93                         m_stream.Close();
  94                         m_buffer = null;
  95                         disposed = true;
  96                 }
  97
  98                 public override void Flush ()
  99                 {
 100                         CheckObjectDisposedException ();
 101
 102                         if (m_buffer_reading) {
 103                                 if (CanSeek)
 104                                         m_stream.Position = Position;
 105                         } else if (m_buffer_pos > 0) {
 106                                 m_stream.Write(m_buffer, 0, m_buffer_pos);
 107                         }
 108
 109                         m_buffer_read_ahead = 0;
 110                         m_buffer_pos = 0;
 111                 }
 112
 113                 public override long Seek (long offset, SeekOrigin origin)
 114                 {
 115                         CheckObjectDisposedException ();
 116                         if (!CanSeek) {
 117                                 throw new NotSupportedException (
 118                                         Locale.GetText ("Non seekable stream."));
 119                         }
 120                         Flush ();
 121                         return m_stream.Seek (offset, origin);
 122                 }
 123
 124                 public override void SetLength (long value)
 125                 {
 126                         CheckObjectDisposedException ();
 127
 128                         if (value < 0)
 129                                 throw new ArgumentOutOfRangeException ("value must be positive");
 130
 131                         if (!m_stream.CanWrite && !m_stream.CanSeek)
 132                                 throw new NotSupportedException ("the stream cannot seek nor write.");
 133
 134                         if ((m_stream == null) || (!m_stream.CanRead && !m_stream.CanWrite))
 135                                 throw new IOException ("the stream is not open");
 136
 137                         m_stream.SetLength(value);
 138                         if (Position > value)
 139                                 Position = value;
 140                 }
 141
 142                 public override int ReadByte ()
 143                 {
 144                         CheckObjectDisposedException ();
 145
 146                         byte[] b = new byte[1];
 147
 148                         if (Read(b, 0, 1) == 1) {
 149                                 return b[0];
 150                         } else {
 151                                 return -1;
 152                         }
 153                 }
 154
 155                 public override void WriteByte (byte value)
 156                 {
 157                         CheckObjectDisposedException ();
 158                         byte[] b = new byte[1];
 159
 160                         b[0] = value;
 161                         Write(b, 0, 1);
 162                 }
 163
 164                 public override int Read ([In,Out] byte[] array, int offset, int count)
 165                 {
 166                         if (array == null)
 167                                 throw new ArgumentNullException ("array");
 168                         CheckObjectDisposedException ();
 169                         if (!m_stream.CanRead) {
 170                                 throw new NotSupportedException (
 171                                         Locale.GetText ("Cannot read from stream"));
 172                         }
 173                         if (offset < 0)
 174                                 throw new ArgumentOutOfRangeException ("offset", "< 0");
 175                         if (count < 0)
 176                                 throw new ArgumentOutOfRangeException ("count", "< 0");
 177                         // re-ordered to avoid possible integer overflow
 178                         if (array.Length - offset < count)
 179                                 throw new ArgumentException ("array.Length - offset < count");
 180
 181                         if (!m_buffer_reading) {
 182                                 Flush();
 183                                 m_buffer_reading = true;
 184                         }
 185
 186                         if (count <= m_buffer_read_ahead - m_buffer_pos) {
 187                                 Array.Copy(m_buffer, m_buffer_pos, array, offset, count);
 188
 189                                 m_buffer_pos += count;
 190                                 if (m_buffer_pos == m_buffer_read_ahead) {
 191                                         m_buffer_pos = 0;
 192                                         m_buffer_read_ahead = 0;
 193                                 }
 194
 195                                 return count;
 196                         }
 197
 198                         int ret = m_buffer_read_ahead - m_buffer_pos;
 199                         Array.Copy(m_buffer, m_buffer_pos, array, offset, ret);
 200                         m_buffer_pos = 0;
 201                         m_buffer_read_ahead = 0;
 202                         offset += ret;
 203                         count -= ret;
 204
 205                         if (count >= m_buffer.Length) {
 206                                 ret += m_stream.Read(array, offset, count);
 207                         } else {
 208                                 m_buffer_read_ahead = m_stream.Read(m_buffer, 0, m_buffer.Length);
 209
 210                                 if (count < m_buffer_read_ahead) {
 211                                         Array.Copy(m_buffer, 0, array, offset, count);
 212                                         m_buffer_pos = count;
 213                                         ret += count;
 214                                 } else {
 215                                         Array.Copy(m_buffer, 0, array, offset, m_buffer_read_ahead);
 216                                         ret += m_buffer_read_ahead;
 217                                         m_buffer_read_ahead = 0;
 218                                 }
 219                         }
 220
 221                         return ret;
 222                 }
 223
 224                 public override void Write (byte[] array, int offset, int count)
 225                 {
 226                         if (array == null)
 227                                 throw new ArgumentNullException ("array");
 228                         CheckObjectDisposedException ();
 229                         if (!m_stream.CanWrite) {
 230                                 throw new NotSupportedException (
 231                                         Locale.GetText ("Cannot write to stream"));
 232                         }
 233                         if (offset < 0)
 234                                 throw new ArgumentOutOfRangeException ("offset", "< 0");
 235                         if (count < 0)
 236                                 throw new ArgumentOutOfRangeException ("count", "< 0");
 237                         // avoid possible integer overflow
 238                         if (array.Length - offset < count)
 239                                 throw new ArgumentException ("array.Length - offset < count");
 240
 241                         if (m_buffer_reading) {
 242                                 Flush();
 243                                 m_buffer_reading = false;
 244                         }
 245
 246                         // reordered to avoid possible integer overflow
 247                         if (m_buffer_pos >= m_buffer.Length - count) {
 248                                 Flush ();
 249                                 m_stream.Write (array, offset, count);
 250                         }
 251                         else {
 252                                 Array.Copy (array, offset, m_buffer, m_buffer_pos, count);
 253                                 m_buffer_pos += count;
 254                         }
 255                 }
 256
 257                 private void CheckObjectDisposedException ()
 258                 {
 259                         if (disposed) {
 260                                 throw new ObjectDisposedException ("BufferedStream",
 261                                         Locale.GetText ("Stream is closed"));
 262                         }
 263                 }
 264         }
 265 }