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Rlp.Encode skip second array creation for length #8440

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merged 2 commits into from
Mar 31, 2025
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Rlp.Encode skip second array creation for length #8440

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Rlp.Encode skip second array creation for length
benaadams Mar 29, 2025
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benaadams Mar 31, 2025
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133 changes: 62 additions & 71 deletions src/Nethermind/Nethermind.Serialization.Rlp/Rlp.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -407,7 +407,7 @@ public static int Encode(Span<byte> buffer, int position, ReadOnlySpan<byte> inp
int lengthOfLength = LengthOfLength(input.Length);
byte prefix = (byte)(183 + lengthOfLength);
buffer[position++] = prefix;
SerializeLength(buffer, position, input.Length);
SerializeLength(input.Length, buffer[position..]);
}

input.CopyTo(buffer.Slice(position, input.Length));
Expand Down Expand Up @@ -437,34 +437,47 @@ static void ThrowArgumentOutOfRangeException()
}
}

[SkipLocalsInit]
public static Rlp Encode(ReadOnlySpan<byte> input)
{
if (input.Length == 0)
// Handle special cases first
int length = input.Length;
if (length == 0)
{
return OfEmptyByteArray;
}

if (input.Length == 1 && input[0] < 128)
// If it's a single byte less than 128, it encodes to itself.
if (length == 1 && input[0] < 128)
{
return new Rlp(input[0]);
}

if (input.Length < 56)
// For lengths < 56, the encoding is one byte of prefix + the data
if (length < 56)
{
byte smallPrefix = (byte)(input.Length + 128);
byte[] rlpResult = new byte[input.Length + 1];
rlpResult[0] = smallPrefix;
// Allocate exactly what we need: 1 prefix byte + input length
byte[] rlpResult = GC.AllocateUninitializedArray<byte>(1 + length);
// First byte is 0x80 + length
rlpResult[0] = (byte)(0x80 + length);
// Copy input after the prefix
input.CopyTo(rlpResult.AsSpan(1));
return new Rlp(rlpResult);
}
else
{
byte[] serializedLength = SerializeLength(input.Length);
byte prefix = (byte)(183 + serializedLength.Length);
byte[] rlpResult = new byte[1 + serializedLength.Length + input.Length];
rlpResult[0] = prefix;
serializedLength.CopyTo(rlpResult.AsSpan(1));
input.CopyTo(rlpResult.AsSpan(1 + serializedLength.Length));
// For length >= 56, we need to encode the length itself (Big-Endian) and prepend a prefix
Span<byte> lengthBuffer = stackalloc byte[4]; // Enough for 32-bit lengths
int lengthOfLength = SerializeLength(length, lengthBuffer);
// Total size = 1 prefix byte + lengthOfLength + data length
int totalSize = 1 + lengthOfLength + length;
byte[] rlpResult = GC.AllocateUninitializedArray<byte>(totalSize);
// Prefix: 0xb7 (183) + number of bytes in length
rlpResult[0] = (byte)(0xb7 + lengthOfLength);
// Then copy length bytes
lengthBuffer[..lengthOfLength].CopyTo(rlpResult.AsSpan(1));
// Finally copy the actual input
input.CopyTo(rlpResult.AsSpan(1 + lengthOfLength));
return new Rlp(rlpResult);
}
}
Expand All @@ -474,30 +487,32 @@ public static Rlp Encode(byte[]? input)
return input is null ? OfEmptyByteArray : Encode(input.AsSpan());
}

public static int SerializeLength(Span<byte> buffer, int position, int value)
private static int SerializeLength(int value, Span<byte> destination)
{
if (value < 1 << 8)
// We assume 0 <= value <= int.MaxValue
if (value < (1 << 8))
{
buffer[position] = (byte)value;
return position + 1;
destination[0] = (byte)value;
return 1;
}

if (value < 1 << 16)
if (value < (1 << 16))
{
BinaryPrimitives.WriteUInt16BigEndian(buffer[position..], (ushort)value);
return position + 2;
BinaryPrimitives.WriteUInt16BigEndian(destination, (ushort)value);
return 2;
}

if (value < 1 << 24)
if (value < (1 << 24))
{
buffer[position] = (byte)(value >> 16);
buffer[position + 1] = ((byte)(value >> 8));
buffer[position + 2] = ((byte)value);
return position + 3;
destination[2] = (byte)value;
destination[1] = (byte)(value >> 8);
destination[0] = (byte)(value >> 16);
return 3;
}

BinaryPrimitives.WriteInt32BigEndian(buffer[position..], value);
return position + 4;
// Otherwise, 4 bytes
BinaryPrimitives.WriteInt32BigEndian(destination, value);
return 4;
}

public static int LengthOfLength(int value)
Expand All @@ -506,40 +521,6 @@ public static int LengthOfLength(int value)
return (bits + 7) / 8;
}

public static byte[] SerializeLength(int value)
{
if (value < 1 << 8)
{
return new[] { (byte)value };
}

if (value < 1 << 16)
{
return new[]
{
(byte) (value >> 8),
(byte) value,
};
}

if (value < 1 << 24)
{
return new[]
{
(byte) (value >> 16),
(byte) (value >> 8),
(byte) value,
};
}

return new[]
{
(byte) (value >> 24),
(byte) (value >> 16),
(byte) (value >> 8),
(byte) value
};
}

public static Rlp Encode(Hash256? keccak)
{
Expand Down Expand Up @@ -575,14 +556,15 @@ public static int StartSequence(Span<byte> buffer, int position, int sequenceLen
}
else
{
afterLength = SerializeLength(buffer, beforeLength, sequenceLength);
afterLength = beforeLength + SerializeLength(sequenceLength, buffer[beforeLength..]);
prefix = (byte)(247 + afterLength - beforeLength);
}

buffer[position] = prefix;
return afterLength;
}

[SkipLocalsInit]
public static Rlp Encode(params Rlp[] sequence)
{
int contentLength = 0;
Expand All @@ -591,34 +573,43 @@ public static Rlp Encode(params Rlp[] sequence)
contentLength += sequence[i].Length;
}

byte[] serializedLength = null;
Span<byte> lengthBuffer = stackalloc byte[4];
int lengthOfLength = 0;
byte prefix;

if (contentLength < 56)
{
prefix = (byte)(192 + contentLength);
// Single-byte prefix: 0xc0 + length
prefix = (byte)(0xc0 + contentLength);
}
else
{
serializedLength = SerializeLength(contentLength);
prefix = (byte)(247 + serializedLength.Length);
// Multi-byte prefix: 0xf7 + lengthOfLength
lengthOfLength = SerializeLength(contentLength, lengthBuffer);
prefix = (byte)(0xf7 + lengthOfLength);
}

int lengthOfPrefixAndSerializedLength = 1 + (serializedLength?.Length ?? 0);
byte[] allBytes = new byte[lengthOfPrefixAndSerializedLength + contentLength];
// Allocate the final buffer exactly once (prefix + optional length + content).
int totalSize = 1 + lengthOfLength + contentLength;
byte[] allBytes = GC.AllocateUninitializedArray<byte>(totalSize);

// Write prefix and length.
allBytes[0] = prefix;
int offset = 1;
if (serializedLength is not null)
if (lengthOfLength > 0)
{
Buffer.BlockCopy(serializedLength, 0, allBytes, offset, serializedLength.Length);
offset += serializedLength.Length;
lengthBuffer[..lengthOfLength].CopyTo(allBytes.AsSpan(offset));
offset += lengthOfLength;
}

// Copy the content from all Rlp items.
for (int i = 0; i < sequence.Length; i++)
{
Buffer.BlockCopy(sequence[i].Bytes, 0, allBytes, offset, sequence[i].Length);
offset += sequence[i].Length;
}

// Wrap in Rlp and return.
return new Rlp(allBytes);
}

Expand Down
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