class/corlib/System.IO/IntPtrStream.cs

   1 //
   2 // System.IO.IntPtrStream: A stream that is backed up by unmanaged memory
   3 //
   4 // Author:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //
   7 // Based on the code for MemoryStream.cs:
   8 //
   9 // Authors:     Marcin Szczepanski (marcins@zipworld.com.au)
  10 //              Patrik Torstensson
  11 //              Gonzalo Paniagua Javier (gonzalo@ximian.com)
  12 //
  13 // (c) 2001,2002 Marcin Szczepanski, Patrik Torstensson
  14 // (c) 2003 Ximian, Inc. (http://www.ximian.com)
  15 //
  16
  17 //
  18 // Copyright (C) 2004 Novell, Inc (http://www.novell.com)
  19 //
  20 // Permission is hereby granted, free of charge, to any person obtaining
  21 // a copy of this software and associated documentation files (the
  22 // "Software"), to deal in the Software without restriction, including
  23 // without limitation the rights to use, copy, modify, merge, publish,
  24 // distribute, sublicense, and/or sell copies of the Software, and to
  25 // permit persons to whom the Software is furnished to do so, subject to
  26 // the following conditions:
  27 //
  28 // The above copyright notice and this permission notice shall be
  29 // included in all copies or substantial portions of the Software.
  30 //
  31 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  32 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  33 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  34 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  35 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  36 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  37 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  38 //
  39
  40 using System.Runtime.InteropServices;
  41 namespace System.IO {
  42
  43         internal class IntPtrStream : Stream {
  44                 unsafe byte *base_address;
  45                 int size;
  46                 int position;
  47                 bool closed;
  48
  49                 public event EventHandler Closed;
  50
  51                 public IntPtrStream (IntPtr base_address, int size)
  52                 {
  53                         unsafe {
  54                                 this.base_address = (byte*)((void *)base_address);
  55                         }
  56                         this.size = size;
  57                         position = 0;
  58                 }
  59
  60                 internal IntPtr BaseAddress {
  61                         get {
  62                                 unsafe {
  63                                         return new IntPtr ((void*) base_address);
  64                                 }
  65                         }
  66                 }
  67
  68                 public override bool CanRead {
  69                         get {
  70                                 return true;
  71                         }
  72                 }
  73
  74                 public override bool CanSeek {
  75                         get {
  76                                 return true;
  77                         }
  78                 }
  79
  80                 public override bool CanWrite {
  81                         get {
  82                                 return false;
  83                         }
  84                 }
  85
  86                 public override long Position {
  87                         get {
  88                                 return position;
  89                         }
  90
  91                         set {
  92                                 if (position < 0)
  93                                         throw new ArgumentOutOfRangeException ("Position", "Can not be negative");
  94                                 if (position > size)
  95                                         throw new ArgumentOutOfRangeException ("Position", "Pointer falls out of range");
  96
  97                                 position = (int) value;
  98                         }
  99                 }
 100
 101                 public override long Length {
 102                         get {
 103                                 return size;
 104                         }
 105                 }
 106
 107                 public override int Read (byte [] buffer, int offset, int count)
 108                 {
 109                         if (buffer == null)
 110                                 throw new ArgumentNullException ("buffer");
 111
 112                         if (offset < 0 || count < 0)
 113                                 throw new ArgumentOutOfRangeException ("offset or count less than zero.");
 114
 115                         if (buffer.Length - offset < count )
 116                                 throw new ArgumentException ("offset+count",
 117                                                               "The size of the buffer is less than offset + count.");
 118
 119                         if (closed)
 120                                 throw new ObjectDisposedException ("Stream has been closed");
 121
 122                         if (position >= size || count == 0)
 123                                 return 0;
 124
 125                         if (position > size - count)
 126                                 count = size - position;
 127
 128                         unsafe {
 129                                 Marshal.Copy ((IntPtr) (base_address + position), buffer, offset, count);
 130                         }
 131                         position += count;
 132                         return count;
 133                 }
 134
 135                 public override int ReadByte ()
 136                 {
 137                         if (position >= size)
 138                                 return -1;
 139
 140                         if (closed)
 141                                 throw new ObjectDisposedException ("Stream has been closed");
 142
 143                         unsafe {
 144                                 return base_address [position++];
 145                         }
 146                 }
 147
 148                 public override long Seek (long offset, SeekOrigin loc)
 149                 {
 150                         // It's funny that they don't throw this exception for < Int32.MinValue
 151                         if (offset > (long) Int32.MaxValue)
 152                                 throw new ArgumentOutOfRangeException ("Offset out of range. " + offset);
 153
 154                         if (closed)
 155                                 throw new ObjectDisposedException ("Stream has been closed");
 156
 157                         int ref_point;
 158                         switch (loc) {
 159                         case SeekOrigin.Begin:
 160                                 if (offset < 0)
 161                                         throw new IOException ("Attempted to seek before start of MemoryStream.");
 162                                 ref_point = 0;
 163                                 break;
 164                         case SeekOrigin.Current:
 165                                 ref_point = position;
 166                                 break;
 167                         case SeekOrigin.End:
 168                                 ref_point = size;
 169                                 break;
 170                         default:
 171                                 throw new ArgumentException ("loc", "Invalid SeekOrigin");
 172                         }
 173
 174                         checked {
 175                                 try {
 176                                         ref_point += (int) offset;
 177                                 } catch {
 178                                         throw new ArgumentOutOfRangeException ("Too large seek destination");
 179                                 }
 180
 181                                 if (ref_point < 0)
 182                                         throw new IOException ("Attempted to seek before start of MemoryStream.");
 183                         }
 184
 185                         position = ref_point;
 186                         return position;
 187                 }
 188
 189                 public override void SetLength (long value)
 190                 {
 191                         throw new NotSupportedException ("This stream can not change its size");
 192                 }
 193
 194                 public override void Write (byte [] buffer, int offset, int count)
 195                 {
 196                         throw new NotSupportedException ("This stream can not change its size");
 197                 }
 198
 199                 public override void WriteByte (byte value)
 200                 {
 201                         throw new NotSupportedException ("This stream can not change its size");
 202                 }
 203
 204                 public override void Flush ()
 205                 {
 206                 }
 207
 208                 public override void Close ()
 209                 {
 210                         closed = true;
 211
 212                         if (Closed != null)
 213                                 Closed (this, null);
 214                 }
 215         }
 216 }