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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// ---------------------------------------------------------------------------
// Native Format Reader
//
// Utilities to read native data from images, that are written by the NativeFormatWriter engine
// ---------------------------------------------------------------------------
using System;
using System.Diagnostics;
using System.Runtime.CompilerServices;
namespace Internal.NativeFormat
{
// Minimal functionality that is low level enough for use in the managed runtime.
internal unsafe partial struct NativePrimitiveDecoder
{
public static byte ReadUInt8(ref byte* stream)
{
byte result = *(stream); // Assumes little endian and unaligned access
stream++;
return result;
}
public static ushort ReadUInt16(ref byte* stream)
{
ushort result = *(ushort*)(stream); // Assumes little endian and unaligned access
stream += 2;
return result;
}
public static uint ReadUInt32(ref byte* stream)
{
uint result = *(uint*)(stream); // Assumes little endian and unaligned access
stream += 4;
return result;
}
public static ulong ReadUInt64(ref byte* stream)
{
ulong result = *(ulong*)(stream); // Assumes little endian and unaligned access
stream += 8;
return result;
}
public static unsafe float ReadFloat(ref byte* stream)
{
uint value = ReadUInt32(ref stream);
return *(float*)(&value);
}
public static double ReadDouble(ref byte* stream)
{
ulong value = ReadUInt64(ref stream);
return *(double*)(&value);
}
public static uint GetUnsignedEncodingSize(uint value)
{
if (value < 128) return 1;
if (value < 128 * 128) return 2;
if (value < 128 * 128 * 128) return 3;
if (value < 128 * 128 * 128 * 128) return 4;
return 5;
}
public static uint DecodeUnsigned(ref byte* stream)
{
uint value = 0;
uint val = *stream;
if ((val & 1) == 0)
{
value = (val >> 1);
stream += 1;
}
else if ((val & 2) == 0)
{
value = (val >> 2) |
(((uint)*(stream + 1)) << 6);
stream += 2;
}
else if ((val & 4) == 0)
{
value = (val >> 3) |
(((uint)*(stream + 1)) << 5) |
(((uint)*(stream + 2)) << 13);
stream += 3;
}
else if ((val & 8) == 0)
{
value = (val >> 4) |
(((uint)*(stream + 1)) << 4) |
(((uint)*(stream + 2)) << 12) |
(((uint)*(stream + 3)) << 20);
stream += 4;
}
else if ((val & 16) == 0)
{
stream += 1;
value = ReadUInt32(ref stream);
}
else
{
Debug.Assert(false);
return 0;
}
return value;
}
public static int DecodeSigned(ref byte* stream)
{
int value = 0;
int val = *(stream);
if ((val & 1) == 0)
{
value = ((sbyte)val) >> 1;
stream += 1;
}
else if ((val & 2) == 0)
{
value = (val >> 2) |
(((int)*(sbyte*)(stream + 1)) << 6);
stream += 2;
}
else if ((val & 4) == 0)
{
value = (val >> 3) |
(((int)*(stream + 1)) << 5) |
(((int)*(sbyte*)(stream + 2)) << 13);
stream += 3;
}
else if ((val & 8) == 0)
{
value = (val >> 4) |
(((int)*(stream + 1)) << 4) |
(((int)*(stream + 2)) << 12) |
(((int)*(sbyte*)(stream + 3)) << 20);
stream += 4;
}
else if ((val & 16) == 0)
{
stream += 1;
value = (int)ReadUInt32(ref stream);
}
else
{
Debug.Assert(false);
return 0;
}
return value;
}
public static ulong DecodeUnsignedLong(ref byte* stream)
{
ulong value = 0;
byte val = *stream;
if ((val & 31) != 31)
{
value = DecodeUnsigned(ref stream);
}
else if ((val & 32) == 0)
{
stream += 1;
value = ReadUInt64(ref stream);
}
else
{
Debug.Assert(false);
return 0;
}
return value;
}
public static long DecodeSignedLong(ref byte* stream)
{
long value = 0;
byte val = *stream;
if ((val & 31) != 31)
{
value = DecodeSigned(ref stream);
}
else if ((val & 32) == 0)
{
stream += 1;
value = (long)ReadUInt64(ref stream);
}
else
{
Debug.Assert(false);
return 0;
}
return value;
}
}
}
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