Add CopyTo() to ReadOnlySpan<T> (#3251)

***NO_CI***

Author: josesimoes

src/CLR/CorLib/corlib_native.cpp

@@ -702,6 +702,7 @@ static const CLR_RT_MethodHandler method_lookup[] =
     nullptr,
     nullptr,
     nullptr,
+    Library_corlib_native_System_ReadOnlySpan_1::CopyTo___VOID__SystemSpan_1,
     nullptr,
     nullptr,
     nullptr,
@@ -1613,7 +1614,7 @@ const CLR_RT_NativeAssemblyData g_CLR_AssemblyNative_mscorlib =
 
 #if (NANOCLR_REFLECTION == TRUE)
 
-    0xF1828DE7,
+    0x4619DD1E,
 
 #elif (NANOCLR_REFLECTION == FALSE)
 
@@ -1624,7 +1625,7 @@ const CLR_RT_NativeAssemblyData g_CLR_AssemblyNative_mscorlib =
 #endif
 
     method_lookup,
-    { 100, 22, 0, 0 }
+    { 100, 22, 0, 1 }
 };
 
 // clang-format on

src/CLR/CorLib/corlib_native.h

@@ -786,6 +786,7 @@ struct Library_corlib_native_System_ReadOnlySpan_1
     static const int FIELD___length = 2;
 
     NANOCLR_NATIVE_DECLARE(_ctor___VOID__VOIDptr__I4);
+    NANOCLR_NATIVE_DECLARE(CopyTo___VOID__SystemSpan_1);
     NANOCLR_NATIVE_DECLARE(NativeReadOnlySpanConstructor___VOID__SZARRAY_GENERICTYPE__I4__I4);
 
     //--//

src/CLR/CorLib/corlib_native_System_ReadOnlySpan_1.cpp

@@ -7,6 +7,7 @@
 #include "CorLib.h"
 
 typedef Library_corlib_native_System_Runtime_CompilerServices_RuntimeHelpers RuntimeHelpers;
+typedef Library_corlib_native_System_Span_1 Span_1;
 
 HRESULT Library_corlib_native_System_ReadOnlySpan_1::_ctor___VOID__VOIDptr__I4(CLR_RT_StackFrame &stack)
 {
@@ -105,6 +106,47 @@ HRESULT Library_corlib_native_System_ReadOnlySpan_1::_ctor___VOID__VOIDptr__I4(C
     NANOCLR_NOCLEANUP();
 }
 
+HRESULT Library_corlib_native_System_ReadOnlySpan_1::CopyTo___VOID__SystemSpan_1(CLR_RT_StackFrame &stack)
+{
+    NANOCLR_HEADER();
+
+    CLR_RT_HeapBlock_Array *sourceArray;
+    CLR_RT_HeapBlock_Array *destinationArray;
+    CLR_RT_HeapBlock *thisSpan = stack.This();
+    CLR_RT_HeapBlock *destinationSpan = stack.Arg1().Dereference();
+
+    // check lengths - destination must be at least as large as source
+    if (thisSpan[FIELD___length].NumericByRefConst().u4 >
+        destinationSpan[Span_1::FIELD___length].NumericByRefConst().u4)
+    {
+        NANOCLR_SET_AND_LEAVE(CLR_E_INVALID_PARAMETER);
+    }
+
+    // get pointers to the arrays
+    sourceArray = thisSpan[FIELD___array].DereferenceArray();
+    destinationArray = destinationSpan[Span_1::FIELD___array].DereferenceArray();
+
+    {
+        // sanity check for empty source array
+        if (thisSpan[FIELD___length].NumericByRefConst().s4 == 0)
+        {
+            NANOCLR_SET_AND_LEAVE(S_OK);
+        }
+
+        // prevent GC from moving the arrays while we copy the data
+        CLR_RT_ProtectFromGC gc1(*sourceArray);
+        CLR_RT_ProtectFromGC gc2(*destinationArray);
+
+        // use memmove to safely handle potential overlapping memory regions
+        memmove(
+            destinationArray->GetElement(0),
+            sourceArray->GetElement(0),
+            thisSpan[FIELD___length].NumericByRefConst().s4 * sourceArray->m_sizeOfElement);
+    }
+
+    NANOCLR_NOCLEANUP();
+}
+
 HRESULT Library_corlib_native_System_ReadOnlySpan_1::NativeReadOnlySpanConstructor___VOID__SZARRAY_GENERICTYPE__I4__I4(
     CLR_RT_StackFrame &stack)
 {