| | 1 | | using System.Buffers.Binary; |
| | 2 | | using System.Runtime.CompilerServices; |
| | 3 | |
|
| | 4 | | namespace NLightning.Domain.Utils; |
| | 5 | |
|
| | 6 | | using Interfaces; |
| | 7 | |
|
| 248 | 8 | | public class BitReader(byte[] buffer) : IBitReader |
| | 9 | | { |
| 248 | 10 | | private readonly byte[] _buffer = buffer ?? throw new ArgumentNullException(nameof(buffer)); |
| 248 | 11 | | private readonly int _totalBits = buffer.Length * 8; |
| | 12 | |
|
| | 13 | | private int _bitOffset; |
| | 14 | |
|
| | 15 | | [MethodImpl(MethodImplOptions.AggressiveInlining)] |
| | 16 | | public int ReadBits(Span<byte> value, int bitLength) |
| | 17 | | { |
| 2316 | 18 | | return ReadBits(value, 0, bitLength); |
| | 19 | | } |
| | 20 | |
|
| | 21 | | [MethodImpl(MethodImplOptions.AggressiveInlining)] |
| | 22 | | private int ReadBits(Span<byte> value, int valueOffset, int bitLength) |
| | 23 | | { |
| 2316 | 24 | | if (_bitOffset + bitLength > _totalBits) |
| | 25 | | { |
| 0 | 26 | | throw new InvalidOperationException( |
| 0 | 27 | | $"Not enough bits left to read. Requested {bitLength}, but only {_totalBits - _bitOffset} remain."); |
| | 28 | | } |
| | 29 | |
|
| 2316 | 30 | | var byteOffset = _bitOffset / 8; |
| 2316 | 31 | | var shift = (int)((uint)_bitOffset % 8); |
| | 32 | |
|
| 2316 | 33 | | if (shift == 0) |
| | 34 | | { |
| | 35 | | // copy bytes to value |
| 536 | 36 | | _buffer.AsSpan(byteOffset, bitLength / 8 + (bitLength % 8 == 0 ? 0 : 1)).CopyTo(value[valueOffset..]); |
| | 37 | |
|
| | 38 | | // mask extra bits |
| 536 | 39 | | if (bitLength % 8 != 0) |
| | 40 | | { |
| 472 | 41 | | value[valueOffset + bitLength / 8] &= (byte)(0xFF << (8 - bitLength % 8)); |
| | 42 | | } |
| | 43 | | } |
| | 44 | | else |
| | 45 | | { |
| 1780 | 46 | | var bytesToRead = bitLength / 8 + (shift > 0 ? 0 : -1); |
| 1780 | 47 | | var maxBytesToRead = value.Length - 1 - valueOffset; |
| 1780 | 48 | | if (bytesToRead > maxBytesToRead) |
| | 49 | | { |
| 52 | 50 | | bytesToRead = maxBytesToRead; |
| | 51 | | } |
| | 52 | |
|
| 20080 | 53 | | for (var i = 0; i <= bytesToRead; i++) |
| | 54 | | { |
| 8260 | 55 | | var left = (byte)(_buffer[byteOffset + i] << shift); |
| 8260 | 56 | | var right = (byte)((_buffer[byteOffset + i + 1] & |
| 8260 | 57 | | (i == bytesToRead + 1 ? 0xFF << (8 - bitLength % 8) : 0xFF)) >> (8 - shift)); |
| | 58 | |
|
| 8260 | 59 | | value[valueOffset + i] = (byte)(left | right); |
| | 60 | | } |
| | 61 | | } |
| | 62 | |
|
| 2316 | 63 | | _bitOffset += bitLength; |
| 2316 | 64 | | return bitLength; |
| | 65 | | } |
| | 66 | |
|
| | 67 | | public bool ReadBit() |
| | 68 | | { |
| 2848 | 69 | | if (_bitOffset >= _totalBits) |
| | 70 | | { |
| 4 | 71 | | throw new InvalidOperationException("No more bits to read."); |
| | 72 | | } |
| | 73 | |
|
| 2844 | 74 | | var byteIndex = _bitOffset / 8; |
| 2844 | 75 | | var bitIndex = _bitOffset % 8; |
| | 76 | |
|
| | 77 | | // Extract the bit at the current BitOffset |
| 2844 | 78 | | var bit = (_buffer[byteIndex] >> (7 - bitIndex)) & 1; |
| | 79 | |
|
| | 80 | | // Increment the BitOffset |
| 2844 | 81 | | _bitOffset++; |
| | 82 | |
|
| 2844 | 83 | | return bit == 1; |
| | 84 | | } |
| | 85 | |
|
| | 86 | | public byte ReadByteFromBits(int bits) |
| | 87 | | { |
| 940 | 88 | | Span<byte> bytes = stackalloc byte[sizeof(byte)]; |
| 940 | 89 | | ReadBits(bytes, bits); |
| 940 | 90 | | var mask = (1 << bits) - 1; |
| 940 | 91 | | return (byte)((bytes[0] >> (sizeof(byte) * 8 - bits)) & mask); |
| | 92 | | } |
| | 93 | |
|
| | 94 | | public short ReadInt16FromBits(int bits, bool bigEndian = true) |
| | 95 | | { |
| 896 | 96 | | Span<byte> bytes = stackalloc byte[sizeof(short)]; |
| 896 | 97 | | ReadBits(bytes, bits); |
| | 98 | |
|
| 896 | 99 | | if ((bigEndian && BitConverter.IsLittleEndian) || (!bigEndian && !BitConverter.IsLittleEndian)) |
| | 100 | | { |
| 892 | 101 | | bytes.Reverse(); |
| | 102 | | } |
| | 103 | |
|
| 896 | 104 | | var mask = (1 << bits) - 1; |
| 896 | 105 | | return (short)((BinaryPrimitives.ReadInt16LittleEndian(bytes) >> (sizeof(short) * 8 - bits)) & mask); |
| | 106 | | } |
| | 107 | |
|
| | 108 | | public ushort ReadUInt16FromBits(int bits, bool bigEndian = true) |
| | 109 | | { |
| 8 | 110 | | Span<byte> bytes = stackalloc byte[sizeof(ushort)]; |
| 8 | 111 | | ReadBits(bytes, bits); |
| | 112 | |
|
| 8 | 113 | | if ((bigEndian && BitConverter.IsLittleEndian) || (!bigEndian && !BitConverter.IsLittleEndian)) |
| | 114 | | { |
| 8 | 115 | | bytes.Reverse(); |
| | 116 | | } |
| | 117 | |
|
| 8 | 118 | | var mask = (1 << bits) - 1; |
| 8 | 119 | | return (ushort)((BinaryPrimitives.ReadUInt16LittleEndian(bytes) >> (sizeof(ushort) * 8 - bits)) & mask); |
| | 120 | | } |
| | 121 | |
|
| | 122 | | public int ReadInt32FromBits(int bits, bool bigEndian = true) |
| | 123 | | { |
| 64 | 124 | | Span<byte> bytes = stackalloc byte[sizeof(int)]; |
| 64 | 125 | | ReadBits(bytes, bits); |
| | 126 | |
|
| 64 | 127 | | if ((bigEndian && BitConverter.IsLittleEndian) || (!bigEndian && !BitConverter.IsLittleEndian)) |
| | 128 | | { |
| 64 | 129 | | bytes.Reverse(); |
| | 130 | | } |
| | 131 | |
|
| 64 | 132 | | var mask = bits != 32 ? (1 << bits) - 1 : -1; |
| 64 | 133 | | return (BinaryPrimitives.ReadInt32LittleEndian(bytes) >> (sizeof(int) * 8 - bits)) & mask; |
| | 134 | | } |
| | 135 | |
|
| | 136 | | public long ReadInt64FromBits(int bits, bool bigEndian = true) |
| | 137 | | { |
| 72 | 138 | | Span<byte> bytes = stackalloc byte[sizeof(long)]; |
| 72 | 139 | | ReadBits(bytes, bits); |
| | 140 | |
|
| 72 | 141 | | if ((bigEndian && BitConverter.IsLittleEndian) || (!bigEndian && !BitConverter.IsLittleEndian)) |
| | 142 | | { |
| 72 | 143 | | bytes.Reverse(); |
| | 144 | | } |
| | 145 | |
|
| 72 | 146 | | return BinaryPrimitives.ReadInt64LittleEndian(bytes) >> (sizeof(long) * 8 - bits); |
| | 147 | | } |
| | 148 | |
|
| | 149 | | public bool HasMoreBits(int requiredBits) |
| | 150 | | { |
| 1316 | 151 | | return _bitOffset + requiredBits <= _totalBits; |
| | 152 | | } |
| | 153 | |
|
| | 154 | | public void SkipBits(int v) |
| | 155 | | { |
| 32 | 156 | | if (_bitOffset + v > _totalBits) |
| | 157 | | { |
| 0 | 158 | | throw new InvalidOperationException($"Cannot skip {v} bits, only {_totalBits - _bitOffset} remain."); |
| | 159 | | } |
| | 160 | |
|
| 32 | 161 | | _bitOffset += v; |
| 32 | 162 | | } |
| | 163 | | } |