using System;
using Unity.Collections.LowLevel.Unsafe;
namespace UnityEngine.InputSystem.Utilities
{
internal static unsafe class MemoryHelpers
{
public struct BitRegion
{
public uint bitOffset;
public uint sizeInBits;
public bool isEmpty => sizeInBits == 0;
public BitRegion(uint bitOffset, uint sizeInBits)
{
this.bitOffset = bitOffset;
this.sizeInBits = sizeInBits;
}
public BitRegion(uint byteOffset, uint bitOffset, uint sizeInBits)
{
this.bitOffset = byteOffset * 8 + bitOffset;
this.sizeInBits = sizeInBits;
}
public BitRegion Overlap(BitRegion other)
{
////REVIEW: too many branches; this can probably be done much smarter
var thisEnd = bitOffset + sizeInBits;
var otherEnd = other.bitOffset + other.sizeInBits;
if (thisEnd <= other.bitOffset || otherEnd <= bitOffset)
return default;
var end = Math.Min(thisEnd, otherEnd);
var start = Math.Max(bitOffset, other.bitOffset);
return new BitRegion(start, end - start);
}
}
public static bool Compare(void* ptr1, void* ptr2, BitRegion region)
{
if (region.sizeInBits == 1)
return ReadSingleBit(ptr1, region.bitOffset) == ReadSingleBit(ptr2, region.bitOffset);
return MemCmpBitRegion(ptr1, ptr2, region.bitOffset, region.sizeInBits);
}
public static uint ComputeFollowingByteOffset(uint byteOffset, uint sizeInBits)
{
return (uint)(byteOffset + sizeInBits / 8 + (sizeInBits % 8 > 0 ? 1 : 0));
}
public static void WriteSingleBit(void* ptr, uint bitOffset, bool value)
{
var byteOffset = bitOffset >> 3;
bitOffset &= 7;
if (value)
*((byte*)ptr + byteOffset) |= (byte)(1U << (int)bitOffset);
else
*((byte*)ptr + byteOffset) &= (byte)~(1U << (int)bitOffset);
}
public static bool ReadSingleBit(void* ptr, uint bitOffset)
{
var byteOffset = bitOffset >> 3;
bitOffset &= 7;
return (*((byte*)ptr + byteOffset) & (1U << (int)bitOffset)) != 0;
}
public static void MemCpyBitRegion(void* destination, void* source, uint bitOffset, uint bitCount)
{
var destPtr = (byte*)destination;
var sourcePtr = (byte*)source;
// If we're offset by more than a byte, adjust our pointers.
if (bitOffset >= 8)
{
var skipBytes = bitOffset / 8;
destPtr += skipBytes;
sourcePtr += skipBytes;
bitOffset %= 8;
}
// Copy unaligned prefix, if any.
if (bitOffset > 0)
{
var byteMask = 0xFF << (int)bitOffset;
if (bitCount + bitOffset < 8)
byteMask &= 0xFF >> (int)(8 - (bitCount + bitOffset));
*destPtr = (byte)(((*destPtr & ~byteMask) | (*sourcePtr & byteMask)) & 0xFF);
// If the total length of the memory region is equal or less than a byte,
// we're done.
if (bitCount + bitOffset <= 8)
return;
++destPtr;
++sourcePtr;
bitCount -= 8 - bitOffset;
}
// Copy contiguous bytes in-between, if any.
var byteCount = bitCount / 8;
if (byteCount >= 1)
UnsafeUtility.MemCpy(destPtr, sourcePtr, byteCount);
// Copy unaligned suffix, if any.
var remainingBitCount = bitCount % 8;
if (remainingBitCount > 0)
{
destPtr += byteCount;
sourcePtr += byteCount;
// We want the lowest remaining bits.
var byteMask = 0xFF >> (int)(8 - remainingBitCount);
*destPtr = (byte)(((*destPtr & ~byteMask) | (*sourcePtr & byteMask)) & 0xFF);
}
}
/// <summary>
/// Compare two memory regions that may be offset by a bit count and have a length expressed
/// in bits.
/// </summary>
/// <param name="ptr1">Pointer to start of first memory region.</param>
/// <param name="ptr2">Pointer to start of second memory region.</param>
/// <param name="bitOffset">Offset in bits from each of the pointers to the start of the memory region to compare.</param>
/// <param name="bitCount">Number of bits to compare in the memory region.</param>
/// <param name="mask">If not null, only compare bits set in the mask. This allows comparing two memory regions while
/// ignoring specific bits.</param>
/// <returns>True if the two memory regions are identical, false otherwise.</returns>
public static bool MemCmpBitRegion(void* ptr1, void* ptr2, uint bitOffset, uint bitCount, void* mask = null)
{
var bytePtr1 = (byte*)ptr1;
var bytePtr2 = (byte*)ptr2;
var maskPtr = (byte*)mask;
// If we're offset by more than a byte, adjust our pointers.
if (bitOffset >= 8)
{
var skipBytes = bitOffset / 8;
bytePtr1 += skipBytes;
bytePtr2 += skipBytes;
if (maskPtr != null)
maskPtr += skipBytes;
bitOffset %= 8;
}
// Compare unaligned prefix, if any.
if (bitOffset > 0)
{
// If the total length of the memory region is less than a byte, we need
// to mask out parts of the bits we're reading.
var byteMask = 0xFF << (int)bitOffset;
if (bitCount + bitOffset < 8)
byteMask &= 0xFF >> (int)(8 - (bitCount + bitOffset));
if (maskPtr != null)
{
byteMask &= *maskPtr;
++maskPtr;
}
var byte1 = *bytePtr1 & byteMask;
var byte2 = *bytePtr2 & byteMask;
if (byte1 != byte2)
return false;
// If the total length of the memory region is equal or less than a byte,
// we're done.
if (bitCount + bitOffset <= 8)
return true;
++bytePtr1;
++bytePtr2;
bitCount -= 8 - bitOffset;
}
// Compare contiguous bytes in-between, if any.
var byteCount = bitCount / 8;
if (byteCount >= 1)
{
if (maskPtr != null)
{
////REVIEW: could go int by int here for as long as we can
// Have to go byte-by-byte in order to apply the masking.
for (var i = 0; i < byteCount; ++i)
{
var byte1 = bytePtr1[i];
var byte2 = bytePtr2[i];
var byteMask = maskPtr[i];
if ((byte1 & byteMask) != (byte2 & byteMask))
return false;
}
}
else
{
if (UnsafeUtility.MemCmp(bytePtr1, bytePtr2, byteCount) != 0)
return false;
}
}
// Compare unaligned suffix, if any.
var remainingBitCount = bitCount % 8;
if (remainingBitCount > 0)
{
bytePtr1 += byteCount;
bytePtr2 += byteCount;
// We want the lowest remaining bits.
var byteMask = 0xFF >> (int)(8 - remainingBitCount);
if (maskPtr != null)
{
maskPtr += byteCount;
byteMask &= *maskPtr;
}
var byte1 = *bytePtr1 & byteMask;
var byte2 = *bytePtr2 & byteMask;
if (byte1 != byte2)
return false;
}
return true;
}
public static void MemSet(void* destination, int numBytes, byte value)
{
var to = (byte*)destination;
var pos = 0;
unchecked
{
// 64bit blocks.
#if UNITY_64
while (numBytes >= 8)
{
*(ulong*)&to[pos] = ((ulong)value << 56) | ((ulong)value << 48) | ((ulong)value << 40) | ((ulong)value << 32)
| ((ulong)value << 24) | ((ulong)value << 16) | ((ulong)value << 8) | value;
numBytes -= 8;
pos += 8;
}
#endif
// 32bit blocks.
while (numBytes >= 4)
{
*(uint*)&to[pos] = ((uint)value << 24) | ((uint)value << 16) | ((uint)value << 8) | value;
numBytes -= 4;
pos += 4;
}
// Remaining bytes.
while (numBytes > 0)
{
to[pos] = value;
numBytes -= 1;
pos += 1;
}
}
}
/// <summary>
/// Copy from <paramref name="source"/> to <paramref name="destination"/> all the bits that
/// ARE set in <paramref name="mask"/>.
/// </summary>
/// <param name="destination">Memory to copy to.</param>
/// <param name="source">Memory to copy from.</param>
/// <param name="numBytes">Number of bytes to copy.</param>
/// <param name="mask">Bitmask that determines which bits to copy. Bits that are set WILL be copied.</param>
public static void MemCpyMasked(void* destination, void* source, int numBytes, void* mask)
{
var from = (byte*)source;
var to = (byte*)destination;
var bits = (byte*)mask;
var pos = 0;
unchecked
{
// Copy 64bit blocks.
#if UNITY_64
while (numBytes >= 8)
{
*(ulong*)(to + pos) &= ~*(ulong*)(bits + pos); // Preserve unmasked bits.
*(ulong*)(to + pos) |= *(ulong*)(from + pos) & *(ulong*)(bits + pos); // Copy masked bits.
numBytes -= 8;
pos += 8;
}
#endif
// Copy 32bit blocks.
while (numBytes >= 4)
{
*(uint*)(to + pos) &= ~*(uint*)(bits + pos); // Preserve unmasked bits.
*(uint*)(to + pos) |= *(uint*)(from + pos) & *(uint*)(bits + pos); // Copy masked bits.
numBytes -= 4;
pos += 4;
}
// Copy remaining bytes.
while (numBytes > 0)
{
unchecked
{
to[pos] &= (byte)~bits[pos]; // Preserve unmasked bits.
to[pos] |= (byte)(from[pos] & bits[pos]); // Copy masked bits.
}
numBytes -= 1;
pos += 1;
}
}
}
/// <summary>
/// Reads bits memory region as unsigned int, up to and including 32 bits, least-significant bit first (LSB).
/// </summary>
/// <param name="ptr">Pointer to memory region.</param>
/// <param name="bitOffset">Offset in bits from the pointer to the start of the unsigned integer.</param>
/// <param name="bitCount">Number of bits to read.</param>
/// <returns>Read unsigned integer.</returns>
public static uint ReadMultipleBitsAsUInt(void* ptr, uint bitOffset, uint bitCount)
{
if (ptr == null)
throw new ArgumentNullException(nameof(ptr));
if (bitCount > sizeof(int) * 8)
throw new ArgumentException("Trying to read more than 32 bits as int", nameof(bitCount));
// Shift the pointer up on larger bitmasks and retry.
if (bitOffset > 32)
{
var newBitOffset = (int)bitOffset % 32;
var intOffset = ((int)bitOffset - newBitOffset) / 32;
ptr = (byte*)ptr + (intOffset * 4);
bitOffset = (uint)newBitOffset;
}
// Bits out of byte.
if (bitOffset + bitCount <= 8)
{
var value = *(byte*)ptr;
value >>= (int)bitOffset;
var mask = 0xFFu >> (8 - (int)bitCount);
return value & mask;
}
// Bits out of short.
if (bitOffset + bitCount <= 16)
{
var value = *(ushort*)ptr;
value >>= (int)bitOffset;
var mask = 0xFFFFu >> (16 - (int)bitCount);
return value & mask;
}
// Bits out of int.
if (bitOffset + bitCount <= 32)
{
var value = *(uint*)ptr;
value >>= (int)bitOffset;
var mask = 0xFFFFFFFFu >> (32 - (int)bitCount);
return value & mask;
}
throw new NotImplementedException("Reading int straddling int boundary");
}
/// <summary>
/// Writes unsigned int as bits to memory region, up to and including 32 bits, least-significant bit first (LSB).
/// </summary>
/// <param name="ptr">Pointer to memory region.</param>
/// <param name="bitOffset">Offset in bits from the pointer to the start of the unsigned integer.</param>
/// <param name="bitCount">Number of bits to read.</param>
/// <param name="value">Value to write.</param>
public static void WriteUIntAsMultipleBits(void* ptr, uint bitOffset, uint bitCount, uint value)
{
if (ptr == null)
throw new ArgumentNullException(nameof(ptr));
if (bitCount > sizeof(int) * 8)
throw new ArgumentException("Trying to write more than 32 bits as int", nameof(bitCount));
// Shift the pointer up on larger bitmasks and retry.
if (bitOffset > 32)
{
var newBitOffset = (int)bitOffset % 32;
var intOffset = ((int)bitOffset - newBitOffset) / 32;
ptr = (byte*)ptr + (intOffset * 4);
bitOffset = (uint)newBitOffset;
}
// Bits out of byte.
if (bitOffset + bitCount <= 8)
{
var byteValue = (byte)value;
byteValue <<= (int)bitOffset;
var mask = ~((0xFFU >> (8 - (int)bitCount)) << (int)bitOffset);
*(byte*)ptr = (byte)((*(byte*)ptr & mask) | byteValue);
return;
}
// Bits out of short.
if (bitOffset + bitCount <= 16)
{
var ushortValue = (ushort)value;
ushortValue <<= (int)bitOffset;
var mask = ~((0xFFFFU >> (16 - (int)bitCount)) << (int)bitOffset);
*(ushort*)ptr = (ushort)((*(ushort*)ptr & mask) | ushortValue);
return;
}
// Bits out of int.
if (bitOffset + bitCount <= 32)
{
var uintValue = (uint)value;
uintValue <<= (int)bitOffset;
var mask = ~((0xFFFFFFFFU >> (32 - (int)bitCount)) << (int)bitOffset);
*(uint*)ptr = (*(uint*)ptr & mask) | uintValue;
return;
}
throw new NotImplementedException("Writing int straddling int boundary");
}
/// <summary>
/// Reads bits memory region as two's complement integer, up to and including 32 bits, least-significant bit first (LSB).
/// For example reading 0xff as 8 bits will result in -1.
/// </summary>
/// <param name="ptr">Pointer to memory region.</param>
/// <param name="bitOffset">Offset in bits from the pointer to the start of the integer.</param>
/// <param name="bitCount">Number of bits to read.</param>
/// <returns>Read integer.</returns>
public static int ReadTwosComplementMultipleBitsAsInt(void* ptr, uint bitOffset, uint bitCount)
{
// int is already represented as two's complement
return (int)ReadMultipleBitsAsUInt(ptr, bitOffset, bitCount);
}
/// <summary>
/// Writes bits memory region as two's complement integer, up to and including 32 bits, least-significant bit first (LSB).
/// </summary>
/// <param name="ptr">Pointer to memory region.</param>
/// <param name="bitOffset">Offset in bits from the pointer to the start of the integer.</param>
/// <param name="bitCount">Number of bits to read.</param>
/// <param name="value">Value to write.</param>
public static void WriteIntAsTwosComplementMultipleBits(void* ptr, uint bitOffset, uint bitCount, int value)
{
// int is already represented as two's complement, so write as-is
WriteUIntAsMultipleBits(ptr, bitOffset, bitCount, (uint)value);
}
/// <summary>
/// Reads bits memory region as excess-K integer where K is set to (2^bitCount)/2, up to and including 32 bits, least-significant bit first (LSB).
/// For example reading 0 as 8 bits will result in -128. Reading 0xff as 8 bits will result in 127.
/// </summary>
/// <param name="ptr">Pointer to memory region.</param>
/// <param name="bitOffset">Offset in bits from the pointer to the start of the integer.</param>
/// <param name="bitCount">Number of bits to read.</param>
/// <returns>Read integer.</returns>
public static int ReadExcessKMultipleBitsAsInt(void* ptr, uint bitOffset, uint bitCount)
{
// https://en.wikipedia.org/wiki/Signed_number_representations#Offset_binary
var value = (long)ReadMultipleBitsAsUInt(ptr, bitOffset, bitCount);
var halfMax = (long)((1UL << (int)bitCount) / 2);
return (int)(value - halfMax);
}
/// <summary>
/// Writes bits memory region as excess-K integer where K is set to (2^bitCount)/2, up to and including 32 bits, least-significant bit first (LSB).
/// </summary>
/// <param name="ptr">Pointer to memory region.</param>
/// <param name="bitOffset">Offset in bits from the pointer to the start of the integer.</param>
/// <param name="bitCount">Number of bits to read.</param>
/// <param name="value">Value to write.</param>
public static void WriteIntAsExcessKMultipleBits(void* ptr, uint bitOffset, uint bitCount, int value)
{
// https://en.wikipedia.org/wiki/Signed_number_representations#Offset_binary
var halfMax = (long)((1UL << (int)bitCount) / 2);
var unsignedValue = halfMax + value;
WriteUIntAsMultipleBits(ptr, bitOffset, bitCount, (uint)unsignedValue);
}
/// <summary>
/// Reads bits memory region as normalized unsigned integer, up to and including 32 bits, least-significant bit first (LSB).
/// For example reading 0 as 8 bits will result in 0.0f. Reading 0xff as 8 bits will result in 1.0f.
/// </summary>
/// <param name="ptr">Pointer to memory region.</param>
/// <param name="bitOffset">Offset in bits from the pointer to the start of the unsigned integer.</param>
/// <param name="bitCount">Number of bits to read.</param>
/// <returns>Normalized unsigned integer.</returns>
public static float ReadMultipleBitsAsNormalizedUInt(void* ptr, uint bitOffset, uint bitCount)
{
var uintValue = ReadMultipleBitsAsUInt(ptr, bitOffset, bitCount);
var maxValue = (uint)((1UL << (int)bitCount) - 1);
return NumberHelpers.UIntToNormalizedFloat(uintValue, 0, maxValue);
}
/// <summary>
/// Writes bits memory region as normalized unsigned integer, up to and including 32 bits, least-significant bit first (LSB).
/// </summary>
/// <param name="ptr">Pointer to memory region.</param>
/// <param name="bitOffset">Offset in bits from the pointer to the start of the unsigned integer.</param>
/// <param name="bitCount">Number of bits to read.</param>
/// <param name="value">Normalized value to write.</param>
public static void WriteNormalizedUIntAsMultipleBits(void* ptr, uint bitOffset, uint bitCount, float value)
{
var maxValue = (uint)((1UL << (int)bitCount) - 1);
var uintValue = NumberHelpers.NormalizedFloatToUInt(value, 0, maxValue);
WriteUIntAsMultipleBits(ptr, bitOffset, bitCount, uintValue);
}
public static void SetBitsInBuffer(void* buffer, int byteOffset, int bitOffset, int sizeInBits, bool value)
{
if (buffer == null)
throw new ArgumentException("A buffer must be provided to apply the bitmask on", nameof(buffer));
if (sizeInBits < 0)
throw new ArgumentException("Negative sizeInBits", nameof(sizeInBits));
if (bitOffset < 0)
throw new ArgumentException("Negative bitOffset", nameof(bitOffset));
if (byteOffset < 0)
throw new ArgumentException("Negative byteOffset", nameof(byteOffset));
// If we're offset by more than a byte, adjust our pointers.
if (bitOffset >= 8)
{
var skipBytes = bitOffset / 8;
byteOffset += skipBytes;
bitOffset %= 8;
}
var bytePos = (byte*)buffer + byteOffset;
var sizeRemainingInBits = sizeInBits;
// Handle first byte separately if unaligned to byte boundary.
if (bitOffset != 0)
{
var mask = 0xFF << bitOffset;
if (sizeRemainingInBits + bitOffset < 8)
{
mask &= 0xFF >> (8 - (sizeRemainingInBits + bitOffset));
}
if (value)
*bytePos |= (byte)mask;
else
*bytePos &= (byte)~mask;
++bytePos;
sizeRemainingInBits -= 8 - bitOffset;
}
// Handle full bytes in-between.
while (sizeRemainingInBits >= 8)
{
*bytePos = value ? (byte)0xFF : (byte)0;
++bytePos;
sizeRemainingInBits -= 8;
}
// Handle unaligned trailing byte, if present.
if (sizeRemainingInBits > 0)
{
var mask = (byte)(0xFF >> 8 - sizeRemainingInBits);
if (value)
*bytePos |= mask;
else
*bytePos &= (byte)~mask;
}
Debug.Assert(bytePos <= (byte*)buffer +
ComputeFollowingByteOffset((uint)byteOffset, (uint)bitOffset + (uint)sizeInBits));
}
public static void Swap<TValue>(ref TValue a, ref TValue b)
{
var temp = a;
a = b;
b = temp;
}
public static uint AlignNatural(uint offset, uint sizeInBytes)
{
var alignment = Math.Min(8, sizeInBytes);
return offset.AlignToMultipleOf(alignment);
}
}
}