/// <summary>
/// Gets array if the slice is over an array, otherwise gets a pointer to memory.
/// </summary>
/// <returns>true if it's a span over an array; otherwise false (if over a pointer)</returns>
/// <remarks>This method can be used for interop, while we are waiting for proper pinning support. Make sure the array contents are read-only.</remarks>
public unsafe bool TryGetArrayElseGetPointer(out ArraySegment <T> array, out void *pointer)
{
var a = Object as T[];
if (a == null)
{
array = new ArraySegment <T>();
pointer = UnsafeUtilities.ComputeAddress(Object, Offset).ToPointer();
return(false);
}
var offsetToData = SpanHelpers <T> .OffsetToArrayData;
var index = (int)((Offset.ToUInt32() - offsetToData) / UnsafeUtilities.SizeOf <T>());
array = new ArraySegment <T>(a, index, Length);
pointer = null;
return(true);
}
/// <summary>
/// platform independent fast memory comparison
/// for x64 it is as fast as memcmp of msvcrt.dll, for x86 it is up to two times faster!!
/// </summary>
internal static bool MemCmp <[Primitive] T>(Span <T> first, Span <T> second)
where T : struct
{
if (first.Length != second.Length)
{
return(false);
}
unsafe
{
// prevent GC from moving memory
var firstPinnedHandle = GCHandle.Alloc(first.Object, GCHandleType.Pinned);
var secondPinnedHandle = GCHandle.Alloc(second.Object, GCHandleType.Pinned);
try
{
byte *firstPointer = (byte *)UnsafeUtilities.ComputeAddress(first.Object, first.Offset).ToPointer();
byte *secondPointer = (byte *)UnsafeUtilities.ComputeAddress(second.Object, second.Offset).ToPointer();
int step = sizeof(void *) * 5;
int totalBytesCount = first.Length * UnsafeUtilities.SizeOf <T>();
byte *firstPointerLimit = firstPointer + (totalBytesCount - step);
if (totalBytesCount > step)
{
while (firstPointer < firstPointerLimit)
{ // IMPORTANT: in order to get HUGE benefits of loop unrolling on x86 we use break instead of return
if (*((void **)firstPointer + 0) != *((void **)secondPointer + 0))
{
break;
}
if (*((void **)firstPointer + 1) != *((void **)secondPointer + 1))
{
break;
}
if (*((void **)firstPointer + 2) != *((void **)secondPointer + 2))
{
break;
}
if (*((void **)firstPointer + 3) != *((void **)secondPointer + 3))
{
break;
}
if (*((void **)firstPointer + 4) != *((void **)secondPointer + 4))
{
break;
}
firstPointer += step;
secondPointer += step;
}
if (firstPointer < firstPointerLimit) // the upper loop ended with break;
{
return(false);
}
}
firstPointerLimit += step; // lets check the remaining bytes
while (firstPointer < firstPointerLimit)
{
if (*firstPointer != *secondPointer)
{
break;
}
++firstPointer;
++secondPointer;
}
return(firstPointer == firstPointerLimit);
}
finally
{
if (firstPinnedHandle.IsAllocated)
{
firstPinnedHandle.Free();
}
if (secondPinnedHandle.IsAllocated)
{
secondPinnedHandle.Free();
}
}
}
}
