mcs/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                 public override bool CanRead {
  61                         get {
  62                                 return true;
  63                         }
  64                 }
  65
  66                 public override bool CanSeek {
  67                         get {
  68                                 return true;
  69                         }
  70                 }
  71
  72                 public override bool CanWrite {
  73                         get {
  74                                 return false;
  75                         }
  76                 }
  77
  78                 public override long Position {
  79                         get {
  80                                 return position;
  81                         }
  82
  83                         set {
  84                                 if (position < 0)
  85                                         throw new ArgumentOutOfRangeException ("Position", "Can not be negative");
  86                                 if (position > size)
  87                                         throw new ArgumentOutOfRangeException ("Position", "Pointer falls out of range");
  88
  89                                 position = (int) value;
  90                         }
  91                 }
  92
  93                 public override long Length {
  94                         get {
  95                                 return size;
  96                         }
  97                 }
  98
  99                 public override int Read (byte [] buffer, int offset, int count)
 100                 {
 101                         if (buffer == null)
 102                                 throw new ArgumentNullException ("buffer");
 103
 104                         if (offset < 0 || count < 0)
 105                                 throw new ArgumentOutOfRangeException ("offset or count less than zero.");
 106
 107                         if (buffer.Length - offset < count )
 108                                 throw new ArgumentException ("offset+count",
 109                                                               "The size of the buffer is less than offset + count.");
 110
 111                         if (closed)
 112                                 throw new ObjectDisposedException ("Stream has been closed");
 113
 114                         if (position >= size || count == 0)
 115                                 return 0;
 116
 117                         if (position > size - count)
 118                                 count = size - position;
 119
 120                         unsafe {
 121                                 Marshal.Copy ((IntPtr) (base_address + position), buffer, offset, count);
 122                         }
 123                         position += count;
 124                         return count;
 125                 }
 126
 127                 public override int ReadByte ()
 128                 {
 129                         if (position >= size)
 130                                 return -1;
 131
 132                         if (closed)
 133                                 throw new ObjectDisposedException ("Stream has been closed");
 134
 135                         unsafe {
 136                                 return base_address [position++];
 137                         }
 138                 }
 139
 140                 public override long Seek (long offset, SeekOrigin loc)
 141                 {
 142                         // It's funny that they don't throw this exception for < Int32.MinValue
 143                         if (offset > (long) Int32.MaxValue)
 144                                 throw new ArgumentOutOfRangeException ("Offset out of range. " + offset);
 145
 146                         if (closed)
 147                                 throw new ObjectDisposedException ("Stream has been closed");
 148
 149                         int ref_point;
 150                         switch (loc) {
 151                         case SeekOrigin.Begin:
 152                                 if (offset < 0)
 153                                         throw new IOException ("Attempted to seek before start of MemoryStream.");
 154                                 ref_point = 0;
 155                                 break;
 156                         case SeekOrigin.Current:
 157                                 ref_point = position;
 158                                 break;
 159                         case SeekOrigin.End:
 160                                 ref_point = size;
 161                                 break;
 162                         default:
 163                                 throw new ArgumentException ("loc", "Invalid SeekOrigin");
 164                         }
 165
 166                         checked {
 167                                 try {
 168                                         ref_point += (int) offset;
 169                                 } catch {
 170                                         throw new ArgumentOutOfRangeException ("Too large seek destination");
 171                                 }
 172
 173                                 if (ref_point < 0)
 174                                         throw new IOException ("Attempted to seek before start of MemoryStream.");
 175                         }
 176
 177                         position = ref_point;
 178                         return position;
 179                 }
 180
 181                 public override void SetLength (long value)
 182                 {
 183                         throw new NotSupportedException ("This stream can not change its size");
 184                 }
 185
 186                 public override void Write (byte [] buffer, int offset, int count)
 187                 {
 188                         throw new NotSupportedException ("This stream can not change its size");
 189                 }
 190
 191                 public override void WriteByte (byte value)
 192                 {
 193                         throw new NotSupportedException ("This stream can not change its size");
 194                 }
 195
 196                 public override void Flush ()
 197                 {
 198                 }
 199
 200                 public override void Close ()
 201                 {
 202                         closed = true;
 203
 204                         if (Closed != null)
 205                                 Closed (this, null);
 206                 }
 207         }
 208 }