Initial commit - WPinternals 2.6

DiscUtils/StripedStream.cs

@@ -0,0 +1,229 @@
+//
+// Copyright (c) 2008-2011, Kenneth Bell
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the "Software"),
+// to deal in the Software without restriction, including without limitation
+// the rights to use, copy, modify, merge, publish, distribute, sublicense,
+// and/or sell copies of the Software, and to permit persons to whom the
+// Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+//
+
+namespace DiscUtils
+{
+    using System;
+    using System.Collections.Generic;
+    using System.IO;
+
+    internal class StripedStream : SparseStream
+    {
+        private List<SparseStream> _wrapped;
+        private long _stripeSize;
+        private Ownership _ownsWrapped;
+        private bool _canRead;
+        private bool _canWrite;
+        private long _length;
+
+        private long _position;
+
+        public StripedStream(long stripeSize, Ownership ownsWrapped, params SparseStream[] wrapped)
+        {
+            _wrapped = new List<SparseStream>(wrapped);
+            _stripeSize = stripeSize;
+            _ownsWrapped = ownsWrapped;
+
+            _canRead = _wrapped[0].CanRead;
+            _canWrite = _wrapped[0].CanWrite;
+            long subStreamLength = _wrapped[0].Length;
+
+            foreach (var stream in _wrapped)
+            {
+                if (stream.CanRead != _canRead || stream.CanWrite != _canWrite)
+                {
+                    throw new ArgumentException("All striped streams must have the same read/write permissions", "wrapped");
+                }
+
+                if (stream.Length != subStreamLength)
+                {
+                    throw new ArgumentException("All striped streams must have the same length", "wrapped");
+                }
+            }
+
+            _length = subStreamLength * wrapped.Length;
+        }
+
+        public override bool CanRead
+        {
+            get { return _canRead; }
+        }
+
+        public override bool CanSeek
+        {
+            get { return true; }
+        }
+
+        public override bool CanWrite
+        {
+            get { return _canWrite; }
+        }
+
+        public override long Length
+        {
+            get { return _length; }
+        }
+
+        public override long Position
+        {
+            get
+            {
+                return _position;
+            }
+
+            set
+            {
+                _position = value;
+            }
+        }
+
+        public override IEnumerable<StreamExtent> Extents
+        {
+            get
+            {
+                // Temporary, indicate there are no 'unstored' extents.
+                // Consider combining extent information from all wrapped streams in future.
+                yield return new StreamExtent(0, _length);
+            }
+        }
+
+        public override void Flush()
+        {
+            foreach (var stream in _wrapped)
+            {
+                stream.Flush();
+            }
+        }
+
+        public override int Read(byte[] buffer, int offset, int count)
+        {
+            if (!CanRead)
+            {
+                throw new InvalidOperationException("Attempt to read to non-readable stream");
+            }
+
+            int maxToRead = (int)Math.Min(_length - _position, count);
+
+            int totalRead = 0;
+            while (totalRead < maxToRead)
+            {
+                long stripe = _position / _stripeSize;
+                long stripeOffset = _position % _stripeSize;
+                int stripeToRead = (int)Math.Min(maxToRead - totalRead, _stripeSize - stripeOffset);
+
+                int streamIdx = (int)(stripe % _wrapped.Count);
+                long streamStripe = stripe / _wrapped.Count;
+
+                Stream targetStream = _wrapped[streamIdx];
+                targetStream.Position = (streamStripe * _stripeSize) + stripeOffset;
+
+                int numRead = targetStream.Read(buffer, offset + totalRead, stripeToRead);
+                _position += numRead;
+                totalRead += numRead;
+            }
+
+            return totalRead;
+        }
+
+        public override long Seek(long offset, SeekOrigin origin)
+        {
+            long effectiveOffset = offset;
+            if (origin == SeekOrigin.Current)
+            {
+                effectiveOffset += _position;
+            }
+            else if (origin == SeekOrigin.End)
+            {
+                effectiveOffset += _length;
+            }
+
+            if (effectiveOffset < 0)
+            {
+                throw new IOException("Attempt to move before beginning of stream");
+            }
+            else
+            {
+                _position = effectiveOffset;
+                return _position;
+            }
+        }
+
+        public override void SetLength(long value)
+        {
+            if (value != _length)
+            {
+                throw new InvalidOperationException("Changing the stream length is not permitted for striped streams");
+            }
+        }
+
+        public override void Write(byte[] buffer, int offset, int count)
+        {
+            if (!CanWrite)
+            {
+                throw new InvalidOperationException("Attempt to write to read-only stream");
+            }
+
+            if (_position + count > _length)
+            {
+                throw new IOException("Attempt to write beyond end of stream");
+            }
+
+            int totalWritten = 0;
+            while (totalWritten < count)
+            {
+                long stripe = _position / _stripeSize;
+                long stripeOffset = _position % _stripeSize;
+                int stripeToWrite = (int)Math.Min(count - totalWritten, _stripeSize - stripeOffset);
+
+                int streamIdx = (int)(stripe % _wrapped.Count);
+                long streamStripe = stripe / _wrapped.Count;
+
+                Stream targetStream = _wrapped[streamIdx];
+                targetStream.Position = (streamStripe * _stripeSize) + stripeOffset;
+                targetStream.Write(buffer, offset + totalWritten, stripeToWrite);
+
+                _position += stripeToWrite;
+                totalWritten += stripeToWrite;
+            }
+        }
+
+        protected override void Dispose(bool disposing)
+        {
+            try
+            {
+                if (disposing && _ownsWrapped == Ownership.Dispose && _wrapped != null)
+                {
+                    foreach (var stream in _wrapped)
+                    {
+                        stream.Dispose();
+                    }
+
+                    _wrapped = null;
+                }
+            }
+            finally
+            {
+                base.Dispose(disposing);
+            }
+        }
+    }
+}