//---------------------------------------------------------------------------
//
// <copyright file="BitmapSourceSafeMILHandle.cs" company="Microsoft">
//    Copyright (C) Microsoft Corporation.  All rights reserved.
// </copyright>
//
//
// Description:
//      A sub-class of SafeMILHandle that can estimate size for bitmap
//      source objects.
//---------------------------------------------------------------------------
 
using System;
using System.Diagnostics;
using System.Security;
using MS.Internal;
using MS.Win32;
 
using UnsafeNativeMethods=MS.Win32.PresentationCore.UnsafeNativeMethods;
 
namespace System.Windows.Media.Imaging
{
    /// <summary>
    /// Constructor which computes size of the handle and delegates
    /// to baseclass safe handle.
    /// </summary>
 
    internal class BitmapSourceSafeMILHandle : SafeMILHandle
    {
        /// <SecurityNote>
        /// Critical - initializes critical static field (autogenerated ctor)
        /// TreatAsSafe - sets them to the correct values, it's ok
        /// </SecurityNote>
        [SecurityCritical, SecurityTreatAsSafe]
        static BitmapSourceSafeMILHandle() { }
 
        /// <summary>
        /// Use this constructor if the handle isn't ready yet and later
        /// set the handle with SetHandle.
        /// </summary>
        /// <SecurityNote>
        ///    Critical: This derives from a class that has a link demand and inheritance demand
        ///    TreatAsSafe: Ok to call constructor
        ///  </SecurityNote>
        [SecurityCritical,SecurityTreatAsSafe]
        internal BitmapSourceSafeMILHandle() : base()
        {
        }
 
        /// <summary>
        /// Use this constructor if the handle exists at construction time.
        /// SafeMILHandle owns the release of the parameter.
        /// </summary>
        /// <SecurityNote>
        ///    Critical: It is used to keep memory around
        ///  </SecurityNote>
        [SecurityCritical]
        internal BitmapSourceSafeMILHandle(IntPtr handle) : base()
        {
            SetHandle(handle);
        }
 
        /// <summary>
        /// Use this constructor if the handle exists at construction time and memory pressure
        /// should be shared with another SafeMILHandle.
        /// SafeMILHandle owns the release of the parameter.
        /// </summary>
        /// <SecurityNote>
        ///    Critical: It is used to keep memory around
        ///  </SecurityNote>
        [SecurityCritical]
        internal BitmapSourceSafeMILHandle(IntPtr handle, SafeMILHandle copyMemoryPressureFrom)
            : this(handle)
        {
            CopyMemoryPressure(copyMemoryPressureFrom);
        }
 
        /// <summary>
        /// Calculate the rough size for this handle
        /// </summary>
        /// <SecurityNote>
        /// Critical - access unmanaged code
        /// TreatAsSafe - queries size of the bitmap, safe operation
        ///
        /// Attributes are required for UnsafeNativeMethods.* calls
        /// </SecurityNote>
        [SecurityCritical,SecurityTreatAsSafe]
        internal void CalculateSize()
        {
            UpdateEstimatedSize(ComputeEstimatedSize(handle));
        }
 
        /// <summary>
        /// Compute a rough estimate of the size in bytes for the image
        /// </summary>
        /// <SecurityNote>
        /// Critical - access unmanaged code and takes an IntPtr
        /// </SecurityNote>
        [SecurityCritical]
        private static long ComputeEstimatedSize(IntPtr bitmapObject)
        {
            long estimatedSize = 0;
 
            if (bitmapObject != null && bitmapObject != IntPtr.Zero)
            {
                IntPtr wicBitmap;
 
                //
                // QueryInterface for the bitmap source to ensure we are
                // calling through the right vtable on the pinvoke.
                //
 
                int hr = UnsafeNativeMethods.MILUnknown.QueryInterface(
                    bitmapObject,
                    ref _uuidBitmap,
                    out wicBitmap
                    );
 
                if (hr == HRESULT.S_OK)
                {
                    Debug.Assert(wicBitmap != IntPtr.Zero);
 
                    //
                    // The safe handle will release the ref added by the above QI
                    //
                    // There's no need to copy memory pressure. Partly because this SafeMILHandle
                    // is temporary and will be collected after this method returns, partly
                    // because there might no memory pressure calculated yet.
                    //
                    SafeMILHandle bitmapSourceSafeHandle = new SafeMILHandle(wicBitmap);
 
                    uint pixelWidth = 0;
                    uint pixelHeight = 0;
 
                    hr = UnsafeNativeMethods.WICBitmapSource.GetSize(
                        bitmapSourceSafeHandle,
                        out pixelWidth,
                        out pixelHeight);
 
                    if (hr == HRESULT.S_OK)
                    {
                        Guid guidFormat;
 
                        hr = UnsafeNativeMethods.WICBitmapSource.GetPixelFormat(bitmapSourceSafeHandle, out guidFormat);
                        if (hr == HRESULT.S_OK)
                        {
                            //
                            // Go to long space to avoid overflow and check for overflow
                            //
                            PixelFormat pixelFormat = new PixelFormat(guidFormat);
 
                            long scanlineSize = (long)pixelWidth * pixelFormat.InternalBitsPerPixel / 8;
 
                            //
                            // Check that scanlineSize is small enough that we can multiply by pixelHeight
                            // without an overflow.  Since pixelHeight is a 32-bit value and we multiply by pixelHeight,
                            // then we can only have a 32-bit scanlineSize.  Since we need a sign bit as well,
                            // we need to check that scanlineSize can fit in 30 bits.
                            //
 
                            if (scanlineSize < 0x40000000)
                            {
                                estimatedSize = pixelHeight * scanlineSize;
                            }
                        }
                    }
                }
            }
 
            return estimatedSize;
        }
 
        /// <summary>
        /// This is overridden to prevent JIT'ing due to new behavior in the CLR. (#708970)
        /// </summary>
        /// <SecurityNote>
        /// Critical - Calls into other SecurityCritical code.  not treat as safe because
        ///            the caller must validate that the underlying handle is a valid COM object.
        /// </SecurityNote>
        [SecurityCritical]
        protected override bool ReleaseHandle()
        {
            return base.ReleaseHandle();
        }
 
        /// <summary>
        /// Guid for IWICBitmapSource
        /// </summary>
        /// <SecurityNote>
        /// Critical - guid used for COM interop, need to be careful not to overwrite
        /// </SecurityNote>
        [SecurityCritical]
        private static Guid _uuidBitmap = MILGuidData.IID_IWICBitmapSource;
 
    }
 
}