Initial commit - WPinternals 2.6

DiscUtils/BuiltStream.cs

@@ -0,0 +1,327 @@
+//
+// 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 BuiltStream : SparseStream
+    {
+        private Stream _baseStream;
+        private long _length;
+        private List<BuilderExtent> _extents;
+
+        private BuilderExtent _currentExtent;
+        private long _position;
+
+        public BuiltStream(long length, List<BuilderExtent> extents)
+        {
+            _baseStream = new ZeroStream(length);
+            _length = length;
+            _extents = extents;
+
+            // Make sure the extents are sorted, so binary searches will work.
+            _extents.Sort(new ExtentStartComparer());
+        }
+
+        public override bool CanRead
+        {
+            get { return true; }
+        }
+
+        public override bool CanSeek
+        {
+            get { return true; }
+        }
+
+        public override bool CanWrite
+        {
+            get { return false; }
+        }
+
+        public override long Length
+        {
+            get { return _length; }
+        }
+
+        public override long Position
+        {
+            get { return _position; }
+            set { _position = value; }
+        }
+
+        public override IEnumerable<StreamExtent> Extents
+        {
+            get
+            {
+                foreach (var extent in _extents)
+                {
+                    foreach (var streamExtent in extent.StreamExtents)
+                    {
+                        yield return streamExtent;
+                    }
+                }
+            }
+        }
+
+        public override void Flush()
+        {
+            return;
+        }
+
+        public override int Read(byte[] buffer, int offset, int count)
+        {
+            if (_position >= _length)
+            {
+                return 0;
+            }
+
+            int totalRead = 0;
+            while (totalRead < count && _position < _length)
+            {
+                // If current region is outside the area of interest, clean it up
+                if (_currentExtent != null && (_position < _currentExtent.Start || _position >= _currentExtent.Start + _currentExtent.Length))
+                {
+                    _currentExtent.DisposeReadState();
+                    _currentExtent = null;
+                }
+
+                // If we need to find a new region, look for it
+                if (_currentExtent == null)
+                {
+                    using (SearchExtent searchExtent = new SearchExtent(_position))
+                    {
+                        int idx = _extents.BinarySearch(searchExtent, new ExtentRangeComparer());
+                        if (idx >= 0)
+                        {
+                            BuilderExtent extent = _extents[idx];
+                            extent.PrepareForRead();
+                            _currentExtent = extent;
+                        }
+                    }
+                }
+
+                int numRead = 0;
+
+                // If the block is outside any known extent, defer to base stream.
+                if (_currentExtent == null)
+                {
+                    _baseStream.Position = _position;
+                    BuilderExtent nextExtent = FindNext(_position);
+                    if (nextExtent != null)
+                    {
+                        numRead = _baseStream.Read(buffer, offset + totalRead, (int)Math.Min(count - totalRead, nextExtent.Start - _position));
+                    }
+                    else
+                    {
+                        numRead = _baseStream.Read(buffer, offset + totalRead, count - totalRead);
+                    }
+                }
+                else
+                {
+                    numRead = _currentExtent.Read(_position, buffer, offset + totalRead, count - totalRead);
+                }
+
+                _position += numRead;
+                totalRead += numRead;
+            }
+
+            return totalRead;
+        }
+
+        public override long Seek(long offset, SeekOrigin origin)
+        {
+            long newPos = offset;
+            if (origin == SeekOrigin.Current)
+            {
+                newPos += _position;
+            }
+            else if (origin == SeekOrigin.End)
+            {
+                newPos += _length;
+            }
+
+            _position = newPos;
+            return newPos;
+        }
+
+        public override void SetLength(long value)
+        {
+            throw new NotSupportedException();
+        }
+
+        public override void Write(byte[] buffer, int offset, int count)
+        {
+            throw new NotSupportedException();
+        }
+
+        protected override void Dispose(bool disposing)
+        {
+            try
+            {
+                if (disposing)
+                {
+                    if (_currentExtent != null)
+                    {
+                        _currentExtent.DisposeReadState();
+                        _currentExtent = null;
+                    }
+
+                    if (_baseStream != null)
+                    {
+                        _baseStream.Dispose();
+                        _baseStream = null;
+                    }
+                }
+            }
+            finally
+            {
+                base.Dispose(disposing);
+            }
+        }
+
+        private BuilderExtent FindNext(long pos)
+        {
+            int min = 0;
+            int max = _extents.Count - 1;
+
+            if (_extents.Count == 0 || (_extents[_extents.Count - 1].Start + _extents[_extents.Count - 1].Length) <= pos)
+            {
+                return null;
+            }
+
+            while (true)
+            {
+                if (min >= max)
+                {
+                    return _extents[min];
+                }
+
+                int mid = (max + min) / 2;
+                if (_extents[mid].Start < pos)
+                {
+                    min = mid + 1;
+                }
+                else if (_extents[mid].Start > pos)
+                {
+                    max = mid;
+                }
+                else
+                {
+                    return _extents[mid];
+                }
+            }
+        }
+
+        private class SearchExtent : BuilderExtent
+        {
+            public SearchExtent(long pos)
+                : base(pos, 1)
+            {
+            }
+
+            public override void Dispose()
+            {
+            }
+
+            internal override void PrepareForRead()
+            {
+                // Not valid to use this 'dummy' extent for actual construction
+                throw new NotSupportedException();
+            }
+
+            internal override int Read(long diskOffset, byte[] block, int offset, int count)
+            {
+                // Not valid to use this 'dummy' extent for actual construction
+                throw new NotSupportedException();
+            }
+
+            internal override void DisposeReadState()
+            {
+                // Not valid to use this 'dummy' extent for actual construction
+                throw new NotSupportedException();
+            }
+        }
+
+        private class ExtentRangeComparer : IComparer<BuilderExtent>
+        {
+            public int Compare(BuilderExtent x, BuilderExtent y)
+            {
+                if (x == null)
+                {
+                    throw new ArgumentNullException("x");
+                }
+
+                if (y == null)
+                {
+                    throw new ArgumentNullException("y");
+                }
+
+                if (x.Start + x.Length <= y.Start)
+                {
+                    // x < y, with no intersection
+                    return -1;
+                }
+                else if (x.Start >= y.Start + y.Length)
+                {
+                    // x > y, with no intersection
+                    return 1;
+                }
+
+                // x intersects y
+                return 0;
+            }
+        }
+
+        private class ExtentStartComparer : IComparer<BuilderExtent>
+        {
+            public int Compare(BuilderExtent x, BuilderExtent y)
+            {
+                if (x == null)
+                {
+                    throw new ArgumentNullException("x");
+                }
+
+                if (y == null)
+                {
+                    throw new ArgumentNullException("y");
+                }
+
+                long val = x.Start - y.Start;
+                if (val < 0)
+                {
+                    return -1;
+                }
+                else if (val > 0)
+                {
+                    return 1;
+                }
+                else
+                {
+                    return 0;
+                }
+            }
+        }
+    }
+}