public static ReadOnlySpan <U> Cast <[Primitive] T, [Primitive] U>(this ReadOnlySpan <T> slice)
where T : struct
where U : struct
{
int countOfU;
/// This comparison is a jittime constant
if (UnsafeUtilities.SizeOf <T>() > UnsafeUtilities.SizeOf <U>())
{
IntPtr count = UnsafeUtilities.CountOfU <T, U>((uint)slice.Length);
unsafe
{
// We can't compare IntPtrs, so have to resort to pointer comparison
bool fits = (byte *)count <= (byte *)int.MaxValue;
Contract.Requires(fits);
countOfU = (int)count.ToPointer();
}
}
else
{
countOfU = slice.Length * UnsafeUtilities.SizeOf <T>() / UnsafeUtilities.SizeOf <U>();
}
object obj = slice.Object;
UIntPtr offset = slice.Offset;
if (countOfU == 0)
{
obj = null;
offset = (UIntPtr)0;
}
return(new ReadOnlySpan <U>(obj, offset, countOfU));
}
/// <summary>
/// Copies the contents of this span into another. The destination
/// must be at least as big as the source, and may be bigger.
/// </summary>
/// <param name="destination">The span to copy items into.</param>
public bool TryCopyTo(Span <T> destination)
{
// There are some benefits of making local copies. See https://github.com/dotnet/coreclr/issues/5556
var dest = destination;
var src = this;
if (src.Length > dest.Length)
{
return(false);
}
if (default(T) != null && MemoryUtils.IsPrimitiveValueType <T>())
{
UnsafeUtilities.CopyBlock(src.Object, src.Offset, dest.Object, dest.Offset,
src.Length * UnsafeUtilities.SizeOf <T>());
}
else
{
for (int i = 0; i < src.Length; i++)
{
// We don't check bounds here as we are surely within them
T value = UnsafeUtilities.Get <T>(src.Object, src.Offset, (UIntPtr)i);
UnsafeUtilities.Set(dest.Object, dest.Offset, (UIntPtr)i, value);
}
}
return(true);
}
/// <summary>
/// Determines whether two spans are structurally (byte-wise) equal by comparing the elements by using memcmp
/// </summary>
/// <param name="first">A span, of type T to compare to second.</param>
/// <param name="second">A span, of type U to compare to first.</param>
public static bool BlockEquals <[Primitive] T, [Primitive] U>(this ReadOnlySpan <T> first, ReadOnlySpan <U> second)
where T : struct
where U : struct
{
var bytesCount = first.Length * UnsafeUtilities.SizeOf <T>();
if (bytesCount != second.Length * UnsafeUtilities.SizeOf <U>())
{
return(false);
}
// perf: it is cheaper to compare 'n' long elements than 'n*8' bytes (in a loop)
if ((bytesCount & 0x00000007) == 0) // fast % sizeof(long)
{
return(SequenceEqual(Cast <T, long>(first), Cast <U, long>(second)));
}
if ((bytesCount & 0x00000003) == 0) // fast % sizeof(int)
{
return(SequenceEqual(Cast <T, int>(first), Cast <U, int>(second)));
}
if ((bytesCount & 0x00000001) == 0) // fast % sizeof(short)
{
return(SequenceEqual(Cast <T, short>(first), Cast <U, short>(second)));
}
return(SequenceEqual(Cast <T, byte>(first), Cast <U, byte>(second)));
}
public unsafe bool TryGetArray(void *dummy, out ArraySegment <T> array)
{
var a = Object as T[];
if (a == null)
{
array = new ArraySegment <T>();
return(false);
}
var offsetToData = SpanHelpers <T> .OffsetToArrayData;
var index = (int)((Offset.ToUInt32() - offsetToData) / UnsafeUtilities.SizeOf <T>());
array = new ArraySegment <T>(a, index, Length);
return(true);
}
public ReadOnlySpan(T[] array, int start, int length)
{
Contract.Requires(array != null);
Contract.RequiresInInclusiveRange(start, length, (uint)array.Length);
if (start < array.Length)
{
Object = array;
Offset = new UIntPtr(
(uint)(SpanHelpers <T> .OffsetToArrayData + (start * UnsafeUtilities.SizeOf <T>())));
Length = length;
}
else
{
Object = null;
Offset = UIntPtr.Zero;
Length = 0;
}
}
/// <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);
}
internal Span(T[] array, int start)
{
Contract.Requires(array != null);
Contract.Requires(default(T) != null || array.GetType() == typeof(T[]));
Contract.RequiresInInclusiveRange(start, (uint)array.Length);
if (start < array.Length)
{
Object = array;
Offset = new UIntPtr(
(uint)(SpanHelpers <T> .OffsetToArrayData + (start * UnsafeUtilities.SizeOf <T>())));
Length = array.Length - start;
}
else
{
Object = null;
Offset = UIntPtr.Zero;
Length = 0;
}
}
/// <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();
}
}
}
}
public ReadOnlySpan <T> Slice(uint start, uint length)
{
Contract.RequiresInInclusiveRange(start, length, (uint)Length);
return(new ReadOnlySpan <T>(
Object, Offset + (((int)start) * UnsafeUtilities.SizeOf <T>()), (int)length));
}
public ReadOnlySpan <T> Slice(int start)
{
Contract.RequiresInInclusiveRange(start, (uint)Length);
return(new ReadOnlySpan <T>(
Object, Offset + (start * UnsafeUtilities.SizeOf <T>()), Length - start));
}
public static void Write <[Primitive] T>(this Span <byte> slice, T value)
where T : struct
{
Contract.RequiresInInclusiveRange(UnsafeUtilities.SizeOf <T>(), (uint)slice.Length);
UnsafeUtilities.Set(slice.Object, slice.Offset, (UIntPtr)0, value);
}
public static T Read <[Primitive] T>(this ReadOnlySpan <byte> slice)
where T : struct
{
Contract.RequiresInInclusiveRange(UnsafeUtilities.SizeOf <T>(), (uint)slice.Length);
return(UnsafeUtilities.Get <T>(slice.Object, slice.Offset, (UIntPtr)0));
}
public Span <T> Slice(int start, int length)
{
Contract.RequiresInInclusiveRange(start, length, (uint)Length);
return(new Span <T>(
Object, Offset + (start * UnsafeUtilities.SizeOf <T>()), length));
}