GPStream.cs source code in C# .NET

                        Code:
                         / DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / fx / src / CommonUI / System / Drawing / Advanced / GPStream.cs / 1 / GPStream.cs
                        
                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

namespace System.Drawing.Internal { 
 
    using System;
    using System.IO; 
    using System.Drawing;
    using System.Runtime.InteropServices;
    using System.Diagnostics.CodeAnalysis;
    using System.Security.Permissions; 

    internal class GPStream : UnsafeNativeMethods.IStream { 
        protected Stream dataStream; 

        // to support seeking ahead of the stream length... 
        long virtualPosition = -1;

        internal GPStream(Stream stream) {
            if (!stream.CanSeek) { 
                const int ReadBlock = 256;
                byte[] bytes = new byte[ReadBlock]; 
                int readLen; 
                int current = 0;
                do { 
                    if (bytes.Length < current + ReadBlock) {
                        byte[] newData = new byte[bytes.Length * 2];
                        Array.Copy(bytes, newData, bytes.Length);
                        bytes = newData; 
                    }
                    readLen = stream.Read(bytes, current, ReadBlock); 
                    current += readLen; 
                } while (readLen != 0);
 
                dataStream = new MemoryStream(bytes);
            }
            else {
                dataStream = stream; 
            }
        } 
 
        private void ActualizeVirtualPosition() {
            if (virtualPosition == -1) return; 

            if (virtualPosition > dataStream.Length)
                dataStream.SetLength(virtualPosition);
 
            dataStream.Position = virtualPosition;
 
            virtualPosition = -1; 
        }
 
        public virtual UnsafeNativeMethods.IStream Clone() {
            NotImplemented();
            return null;
        } 

        public virtual void Commit(int grfCommitFlags) { 
            dataStream.Flush(); 
            // Extend the length of the file if needed.
            ActualizeVirtualPosition(); 
        }

        [
            UIPermission(SecurityAction.Demand, Window=UIPermissionWindow.AllWindows), 
            SecurityPermission(SecurityAction.Assert, Flags=SecurityPermissionFlag.UnmanagedCode)
        ] 
        public virtual long CopyTo(UnsafeNativeMethods.IStream pstm, long cb, long[] pcbRead) { 

            int bufsize = 4096; // one page 
            IntPtr buffer = Marshal.AllocHGlobal(bufsize);
            if (buffer == IntPtr.Zero) throw new OutOfMemoryException();
            long written = 0;
            try { 
                while (written < cb) {
                    int toRead = bufsize; 
                    if (written + toRead > cb) toRead  = (int) (cb - written); 
                    int read = Read(buffer, toRead);
                    if (read == 0) break; 
                    if (pstm.Write(buffer, read) != read) {
                        throw EFail("Wrote an incorrect number of bytes");
                    }
                    written += read; 
                }
            } 
            finally { 
                Marshal.FreeHGlobal(buffer);
            } 
            if (pcbRead != null && pcbRead.Length > 0) {
                pcbRead[0] = written;
            }
 
            return written;
        } 
 
        public virtual Stream GetDataStream() {
            return dataStream; 
        }

        public virtual void LockRegion(long libOffset, long cb, int dwLockType) {
        } 

        protected static ExternalException EFail(string msg) { 
            throw new ExternalException(msg, SafeNativeMethods.E_FAIL); 
        }
 
        protected static void NotImplemented() {
            throw new ExternalException(SR.GetString(SR.NotImplemented), SafeNativeMethods.E_NOTIMPL);
        }
 
        public virtual int Read(IntPtr buf, /* cpr: int offset,*/  int length) {
            //        System.Text.Out.WriteLine("IStream::Read(" + length + ")"); 
            byte[] buffer = new byte[length]; 
            int count = Read(buffer, length);
            Marshal.Copy(buffer, 0, buf, length); 
            return count;
        }

        public virtual int Read(byte[] buffer, /* cpr: int offset,*/  int length) { 
            ActualizeVirtualPosition();
            return dataStream.Read(buffer, 0, length); 
        } 

        public virtual void Revert() { 
            NotImplemented();
        }

        public virtual long Seek(long offset, int origin) { 
            // Console.WriteLine("IStream::Seek("+ offset + ", " + origin + ")");
            long pos = virtualPosition; 
            if (virtualPosition == -1) { 
                pos = dataStream.Position;
            } 
            long len = dataStream.Length;
            switch (origin) {
                case SafeNativeMethods.StreamConsts.STREAM_SEEK_SET:
                    if (offset <= len) { 
                        dataStream.Position = offset;
                        virtualPosition = -1; 
                    } 
                    else {
                        virtualPosition = offset; 
                    }
                    break;
                case SafeNativeMethods.StreamConsts.STREAM_SEEK_END:
                    if (offset <= 0) { 
                        dataStream.Position = len + offset;
                        virtualPosition = -1; 
                    } 
                    else {
                        virtualPosition = len + offset; 
                    }
                    break;
                case SafeNativeMethods.StreamConsts.STREAM_SEEK_CUR:
                    if (offset+pos <= len) { 
                        dataStream.Position = pos + offset;
                        virtualPosition = -1; 
                    } 
                    else {
                        virtualPosition = offset + pos; 
                    }
                    break;
            }
            if (virtualPosition != -1) { 
                return virtualPosition;
            } 
            else { 
                return dataStream.Position;
            } 
        }

        public virtual void SetSize(long value) {
            dataStream.SetLength(value); 
        }
 
        public void Stat(IntPtr pstatstg, int grfStatFlag) { 
            STATSTG stats = new STATSTG();
            stats.cbSize = dataStream.Length; 
            Marshal.StructureToPtr(stats, pstatstg, true);
        }

        public virtual void UnlockRegion(long libOffset, long cb, int dwLockType) { 
        }
 
        public virtual int Write(IntPtr buf, /* cpr: int offset,*/ int length) { 
            byte[] buffer = new byte[length];
            Marshal.Copy(buf, buffer, 0, length); 
            return Write(buffer, length);
        }

        public virtual int Write(byte[] buffer, /* cpr: int offset,*/ int length) { 
            ActualizeVirtualPosition();
            dataStream.Write(buffer, 0, length); 
            return length; 
        }
 
        [StructLayout(LayoutKind.Sequential)]
        public class STATSTG {

            [SuppressMessage("Microsoft.Reliability", "CA2006:UseSafeHandleToEncapsulateNativeResources")] 
            public   IntPtr pwcsName = IntPtr.Zero;
            public   int type = 0; 
            [MarshalAs(UnmanagedType.I8)] 
            public   long cbSize;
            [MarshalAs(UnmanagedType.I8)] 
            public   long mtime = 0;
            [MarshalAs(UnmanagedType.I8)]
            public   long ctime = 0;
            [MarshalAs(UnmanagedType.I8)] 
            public   long atime = 0;
            [MarshalAs(UnmanagedType.I4)] 
            public   int grfMode = 0; 
            [MarshalAs(UnmanagedType.I4)]
            public   int grfLocksSupported = 0; 

            public   int clsid_data1 = 0;
            [MarshalAs(UnmanagedType.I2)]
            public   short clsid_data2 = 0; 
            [MarshalAs(UnmanagedType.I2)]
            public   short clsid_data3 = 0; 
            [MarshalAs(UnmanagedType.U1)] 
            public   byte clsid_b0 = 0;
            [MarshalAs(UnmanagedType.U1)] 
            public   byte clsid_b1 = 0;
            [MarshalAs(UnmanagedType.U1)]
            public   byte clsid_b2 = 0;
            [MarshalAs(UnmanagedType.U1)] 
            public   byte clsid_b3 = 0;
            [MarshalAs(UnmanagedType.U1)] 
            public   byte clsid_b4 = 0; 
            [MarshalAs(UnmanagedType.U1)]
            public   byte clsid_b5 = 0; 
            [MarshalAs(UnmanagedType.U1)]
            public   byte clsid_b6 = 0;
            [MarshalAs(UnmanagedType.U1)]
            public   byte clsid_b7 = 0; 
            [MarshalAs(UnmanagedType.I4)]
            public   int grfStateBits = 0; 
            [MarshalAs(UnmanagedType.I4)] 
            public   int reserved = 0;
        } 
    }
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007. 
// Copyright (c) Microsoft Corporation. All rights reserved.
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GPStream.cs source code in C# .NET

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