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