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More LEB optimizations around memory allocation
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@Gekctek
Gekctek committed Feb 1, 2023
1 parent 51b7402 commit 9cb916e
Showing 1 changed file with 112 additions and 61 deletions.
173 changes: 112 additions & 61 deletions src/Candid/Encodings/LEB128.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@
using EdjCase.ICP.Candid.Utilities;
using System;
using System.Buffers;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Linq;
Expand Down Expand Up @@ -104,29 +105,42 @@ public static void EncodeSigned(UnboundedInt value, IBufferWriter<byte> destinat
private static BigInteger Decode(Stream stream, bool isUnsigned)
{
IEnumerable<bool> bits = GetValueBits(stream, isUnsigned);
ArrayBufferWriter<byte> destination = new();
int i = 1;
byte byteValue = 0;
foreach (bool bit in bits)
byte[] pooledMemory = ArrayPool<byte>.Shared.Rent(10);
try
{
if (bit)
int bitIndex = 0;
int byteIndex = 0;
byte byteValue = 0;
foreach (bool bit in bits)
{
byteValue |= (byte)(1 << (i - 1));
if (bit)
{
// Set bit on byte
byteValue |= (byte)(1 << bitIndex);
}
if (bitIndex == 7)
{
SetPooledMemoryByte(ref pooledMemory, ref byteIndex, byteValue);
byteValue = 0; // Reset byte to empty
bitIndex = 0; // Reset index back to beginning of byte
}
else
{
bitIndex++;
}
}
if (i == 8)
if (bitIndex != 0)
{
destination.WriteOne(byteValue);
byteValue = 0;
i = 0;
// Expect 8 byte chunks
throw new EndOfStreamException();
}
i++;
return new BigInteger(pooledMemory.AsSpan()[..byteIndex], isUnsigned, isBigEndian: false);
}
if (i != 1)
finally
{
// Expect 8 byte chunks
throw new EndOfStreamException();
// Return shared memory
ArrayPool<byte>.Shared.Return(pooledMemory);
}
return new BigInteger(destination.WrittenSpan, isUnsigned, isBigEndian: false);
}
private static IEnumerable<bool> GetValueBits(Stream stream, bool isUnsigned)
{
Expand Down Expand Up @@ -197,25 +211,38 @@ private static void EncodeUnsigned(BigInteger value, IBufferWriter<byte> destina
// 0100110 0001110 1100101 Split into 7-bit groups
// 00100110 10001110 11100101 Add high 1 bits on all but last (most significant) group to form bytes

Span<byte> buffer = stackalloc byte[1];
while (value != 0)
byte[] pooledMemory = ArrayPool<byte>.Shared.Rent(10); // Use shared memory to avoid allocations
try
{
BigInteger nextByte = (value & 0b0111_1111); // Get the next 7 bits
Span<byte> buffer = stackalloc byte[1];
int byteIndex = 0;
while (value != 0)
{
BigInteger nextByte = (value & 0b0111_1111); // Get the next 7 bits

// Optimization to use the buffer to get byte value
nextByte.TryWriteBytes(buffer, out _, isUnsigned: true, isBigEndian: false);
// Optimization to use the buffer to get byte value
nextByte.TryWriteBytes(buffer, out _, isUnsigned: true, isBigEndian: false);

byte byteValue = buffer[0]; // Get next byte from the buffer
byte byteValue = buffer[0]; // Get next byte from the buffer


value = value >> 7; // Chop off last 7 bits
if (value != 0)
{
// Have most left of byte be 1 if there is another byte
byteValue |= 0b10000000;
value = value >> 7; // Chop off last 7 bits
if (value != 0)
{
// Have most left of byte be 1 if there is another byte
byteValue |= 0b10000000;
}

SetPooledMemoryByte(ref pooledMemory, ref byteIndex, byteValue);
}
destination.WriteOne(byteValue);
destination.Write(pooledMemory.AsSpan()[..byteIndex]); // Write to the
}
finally
{
// Return shared memory
ArrayPool<byte>.Shared.Return(pooledMemory);
}

}

private static void EncodeSigned(BigInteger value, IBufferWriter<byte> destination)
Expand All @@ -234,51 +261,62 @@ private static void EncodeSigned(BigInteger value, IBufferWriter<byte> destinati
// 1111000 0111011 1000000 Split into 7-bit groups
//01111000 10111011 11000000 Add high 1 bits on all but last (most significant) group to form bytes

bool more = true;
Span<byte> buffer = stackalloc byte[1];
while (more)
int byteIndex = 0;
byte[] pooledMemory = ArrayPool<byte>.Shared.Rent(10); // Use shared memory to avoid allocations
try
{
BigInteger nextByte = (value & 0b0111_1111); // Get the next 7 bits
bool more = true;
Span<byte> buffer = stackalloc byte[1];
while (more)
{
BigInteger nextByte = (value & 0b0111_1111); // Get the next 7 bits

// Optimization to use the buffer to get byte value
nextByte.TryWriteBytes(buffer, out _, isUnsigned: true, isBigEndian: false);
// Optimization to use the buffer to get byte value
nextByte.TryWriteBytes(buffer, out _, isUnsigned: true, isBigEndian: false);

byte byteValue = buffer[0]; // Get next byte from the buffer
byte byteValue = buffer[0]; // Get next byte from the buffer

value >>= 7; // Shift over 7 bits to setup the next byte
bool mostSignficantBitIsSet = (byteValue & 0b0100_0000) != 0;
if (value == 0) // no more bits => end
{
if (mostSignficantBitIsSet)
value >>= 7; // Shift over 7 bits to setup the next byte
bool mostSignficantBitIsSet = (byteValue & 0b0100_0000) != 0;
if (value == 0) // no more bits => end
{
// If last bit is a 1, add another 0 value byte
AddByteWithMoreFlag(byteValue);
AddByte(0b0000_0000);
if (mostSignficantBitIsSet)
{
// If last bit is a 1, add another 0 value byte
AddByteWithMoreFlag(byteValue);
AddByte(0b0000_0000);
break;
}
AddByte(byteValue);
break;
}
AddByte(byteValue);
break;
}
if (value == -1) // -1 == only bit remaining is a sign bit (with backfilled 1's from a right shift) => end
{
// -1 is equivalent to all 1's in the binary sequence/255 if unsigned
// AND since if the number is negative, 1 is used to fill vacated bit positions
// meaning the remaining value is just the sign bit
if (value == -1) // -1 == only bit remaining is a sign bit (with backfilled 1's from a right shift) => end
{
// -1 is equivalent to all 1's in the binary sequence/255 if unsigned
// AND since if the number is negative, 1 is used to fill vacated bit positions
// meaning the remaining value is just the sign bit

// IF the most signficant bit is not set, set the final byte to 0b0111_1111
// otherwise end
// IF the most signficant bit is not set, set the final byte to 0b0111_1111
// otherwise end

if (!mostSignficantBitIsSet)
{
// If last bit is a 1, add another 111_1111 value byte
AddByteWithMoreFlag(byteValue);
AddByte(0b0111_1111);
if (!mostSignficantBitIsSet)
{
// If last bit is a 1, add another 111_1111 value byte
AddByteWithMoreFlag(byteValue);
AddByte(0b0111_1111);
break;
}
AddByte(byteValue);
break;
}
AddByte(byteValue);
break;
AddByteWithMoreFlag(byteValue);
}
AddByteWithMoreFlag(byteValue);
destination.Write(pooledMemory.AsSpan()[..byteIndex]); // Write bytes to destination
}
finally
{
// Return shared memory
ArrayPool<byte>.Shared.Return(pooledMemory);
}

void AddByteWithMoreFlag(byte byteValue)
Expand All @@ -288,8 +326,21 @@ void AddByteWithMoreFlag(byte byteValue)

void AddByte(byte byteValue)
{
destination.WriteOne(byteValue);
SetPooledMemoryByte(ref pooledMemory, ref byteIndex, byteValue);
}
}

private static void SetPooledMemoryByte(ref byte[] pooledMemory, ref int byteIndex, byte byteValue)
{
if (byteIndex >= pooledMemory.Length)
{
// If pooled memory is too small, create bigger array
var newPooledMemory = ArrayPool<byte>.Shared.Rent(pooledMemory.Length + 10);
pooledMemory.AsSpan().CopyTo(newPooledMemory);
ArrayPool<byte>.Shared.Return(pooledMemory);
pooledMemory = newPooledMemory;
}
pooledMemory[byteIndex++] = byteValue;
}
}
}

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