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using System;
using System.Security;

namespace System.Reflection
{
    public delegate ref TField FieldAccessor<TField>(object target);

    public delegate ref TField FieldAccessor<TTarget, TField>(ref TTarget target);

    /// <summary>

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// Input: a 32-bit integer of the form [ 00wwwwww 00xxxxxx 00yyyyyy 00zzzzzz ]
// Output: a 32-bit integer where each input byte is mapped to its corresponding BASE64 ASCII byte
private static uint ByteToBase64(uint b)
{
    b += 0x41414141U; // 'A'
    return b
        + (0x06U * (((b + 0x25252525U) & 0x80808080U) >> 7))
        - (0x4BU * (((b + 0x0B0B0B0BU) & 0x80808080U) >> 7))
        - (0x0FU * (((b + 0x01010101U) & 0x80808080U) >> 7))
        + (0x03U * ((b & 0x80808080U) >> 7));

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; System_Private_CoreLib!System.Buffer.Memmove(Byte*, Byte*, UInt64):
00007ff8`1f759440 0f1f440000      nop     dword ptr [rax+rax]
00007ff8`1f759445 488bc1          mov     rax,rcx
00007ff8`1f759448 482bc2          sub     rax,rdx
00007ff8`1f75944b 493bc0          cmp     rax,r8
00007ff8`1f75944e 0f822f010000    jb      System_Private_CoreLib!System.Buffer.Memmove(Byte*, Byte*, UInt64)+0x143 (00007ff8`1f759583)
00007ff8`1f759454 488bc2          mov     rax,rdx
00007ff8`1f759457 482bc1          sub     rax,rcx
00007ff8`1f75945a 493bc0          cmp     rax,r8
00007ff8`1f75945d 0f8220010000    jb      System_Private_CoreLib!System.Buffer.Memmove(Byte*, Byte*, UInt64)+0x143 (00007ff8`1f759583)

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; System_Private_CoreLib!System.Buffer.Memmove(System.ByReference`1<Byte>, System.ByReference`1<Byte>, UInt64):
00007ff8`2c697e30 4883ec28        sub     rsp,28h
00007ff8`2c697e34 90              nop
00007ff8`2c697e35 488bc1          mov     rax,rcx
00007ff8`2c697e38 482bc2          sub     rax,rdx
00007ff8`2c697e3b 493bc0          cmp     rax,r8
00007ff8`2c697e3e 0f8233010000    jb      System_Private_CoreLib!System.Buffer.Memmove(System.ByReference`1<Byte>, System.ByReference`1<Byte>, UInt64)+0x147 (00007ff8`2c697f77)
00007ff8`2c697e44 488bc2          mov     rax,rdx
00007ff8`2c697e47 482bc1          sub     rax,rcx
00007ff8`2c697e4a 493bc0          cmp     rax,r8

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; System_Private_CoreLib!System.Buffer.Memmove(Byte*, Byte*, UInt32):
53c15f10 55              push    ebp
53c15f11 8bec            mov     ebp,esp
53c15f13 57              push    edi
53c15f14 56              push    esi
53c15f15 53              push    ebx
53c15f16 83ec08          sub     esp,8
53c15f19 8b4508          mov     eax,dword ptr [ebp+8]
53c15f1c 8bf1            mov     esi,ecx
53c15f1e 2bf2            sub     esi,edx

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; System_Private_CoreLib!System.Buffer.Memmove(System.ByReference`1<Byte>, System.ByReference`1<Byte>, UInt32):
53b9caec 55              push    ebp
53b9caed 8bec            mov     ebp,esp
53b9caef 57              push    edi
53b9caf0 56              push    esi
53b9caf1 53              push    ebx
53b9caf2 8b550c          mov     edx,dword ptr [ebp+0Ch]
53b9caf5 2b5508          sub     edx,dword ptr [ebp+8]
53b9caf8 8b4508          mov     eax,dword ptr [ebp+8]
53b9cafb 2b450c          sub     eax,dword ptr [ebp+0Ch]

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using System;
using System.Diagnostics;
using System.Runtime.CompilerServices;
using System.Threading;

namespace ConsoleApp3
{
    class Program
    {
        static void Main(string[] args)

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/*
 * !! WARNING !!
 * 
 * COMPLETELY UNTESTED CODE
 */

using Microsoft.Win32.SafeHandles;
using System.Diagnostics;
using System.Runtime.CompilerServices;
using System.Runtime.ConstrainedExecution;

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This tests the performance of MemoryExtensions.ToUpperInvariant(this ReadOnlySpan<char>, Span<char>), String.GetHashCode(), and String.GetHashCode(StringComparison.OrdinalIgnoreCase).

In below table:

• baseline coreclr = 3.0.0-preview1-26808-05
• local build (6) = local build from private dev Utf8String branch, 6th rev.
• local build (7) = local build from private dev Utf8String branch, 7th rev.

Method	Toolchain	StringLength	Mean	Error	StdDev	Scaled	ScaledSD
ToUpperInvariant	baseline coreclr	0	27.112 ns	0.7416 ns	1.1763 ns	1.00	0.00

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Usage, usability, and behaviors

The goal of this project is to make a type that mirrors System.String as much as practical. It should be a heapable, immutable, indexable, and pinnable type. The data may contain embedded null characters. When pinned, the pointer should represent a null-terminated UTF-8 string.

We should provide conversions between String and Utf8String, though due to the expense of conversion we should avoid these operations when possible. There are a few ways to avoid these, including:

• Adding Utf8String-based overloads to existing APIs like Console.WriteLine, File.WriteAllText, etc.
• Adding ToUtf8String methods on existing types like Int32.
• Implement utility classes like Utf8StringBuilder.
• Not having implicit or explicit conversion operators that could perform expensive transcodings, but instead having constructor overloads or some other obvious "this may be expensive" mechanism.