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refactor: make EncodeState generic over TAlphabet to fold alphabet #5

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Merged
unsafePtr merged 1 commit into from
Apr 27, 2026
Merged

refactor: make EncodeState generic over TAlphabet to fold alphabet #5

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35 changes: 16 additions & 19 deletions src/Base58Encoding/Base58.Encode.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -78,7 +78,7 @@ private string EncodeGenericToString(ReadOnlySpan<byte> data)
{
Span<byte> digits = stackalloc byte[size];
int digitCount = ComputeGenericDigits(inputSpan, digits);
var state = new EncodeState(digits, 0, digitCount, TAlphabet.Characters, TAlphabet.FirstCharacter, leadingZeros);
var state = new EncodeState<TAlphabet>(digits, 0, digitCount, leadingZeros);
return string.Create(state.OutputLength, state, static (span, s) => s.EmitReverse(span));
}

Expand All @@ -91,7 +91,7 @@ private string EncodeGenericToStringLarge(ReadOnlySpan<byte> inputSpan, int lead
try
{
int digitCount = ComputeGenericDigits(inputSpan, rented);
var state = new EncodeState(rented, 0, digitCount, TAlphabet.Characters, TAlphabet.FirstCharacter, leadingZeros);
var state = new EncodeState<TAlphabet>(rented, 0, digitCount, leadingZeros);
return string.Create(state.OutputLength, state, static (span, s) => s.EmitReverse(span));
}
finally
Expand Down Expand Up @@ -129,7 +129,7 @@ private int EncodeGenericToBytes(ReadOnlySpan<byte> data, Span<byte> destination
ThrowHelper.ThrowDestinationTooSmall(nameof(destination));
}

var state = new EncodeState(digits, 0, digitCount, TAlphabet.Characters, TAlphabet.FirstCharacter, leadingZeros);
var state = new EncodeState<TAlphabet>(digits, 0, digitCount, leadingZeros);
state.EmitReverse(destination);
return outputLength;
}
Expand All @@ -149,7 +149,7 @@ private int EncodeGenericToBytesLarge(ReadOnlySpan<byte> inputSpan, int leadingZ
ThrowHelper.ThrowDestinationTooSmall(nameof(destination));
}

var state = new EncodeState(rented, 0, digitCount, TAlphabet.Characters, TAlphabet.FirstCharacter, leadingZeros);
var state = new EncodeState<TAlphabet>(rented, 0, digitCount, leadingZeros);
state.EmitReverse(destination);
return outputLength;
}
Expand Down Expand Up @@ -202,7 +202,7 @@ internal static string EncodeBitcoin32FastToString(ReadOnlySpan<byte> data)
Debug.Assert(skip >= 0, "rawLeadingZeros should always be >= inLeadingZeros by Base58 math");
int digitCount = Base58BitcoinTables.Raw58Sz32 - rawLeadingZeros;

var state = new EncodeState(rawBase58, rawLeadingZeros, digitCount, Base58BitcoinTables.BitcoinChars, (byte)'1', inLeadingZeros);
var state = new EncodeState<TAlphabet>(rawBase58, rawLeadingZeros, digitCount, inLeadingZeros);
return string.Create(state.OutputLength, state, static (span, s) => s.EmitForward(span));
}

Expand Down Expand Up @@ -235,7 +235,7 @@ private static int EncodeBitcoin32FastToBytes(ReadOnlySpan<byte> data, Span<byte
ThrowHelper.ThrowDestinationTooSmall(nameof(destination));
}

var state = new EncodeState(rawBase58, rawLeadingZeros, digitCount, Base58BitcoinTables.BitcoinChars, (byte)'1', inLeadingZeros);
var state = new EncodeState<TAlphabet>(rawBase58, rawLeadingZeros, digitCount, inLeadingZeros);
state.EmitForward(destination);
return outputLength;
}
Expand Down Expand Up @@ -311,7 +311,7 @@ internal static string EncodeBitcoin64FastToString(ReadOnlySpan<byte> data)
Debug.Assert(skip >= 0, "rawLeadingZeros should always be >= inLeadingZeros by Base58 math");
int digitCount = Base58BitcoinTables.Raw58Sz64 - rawLeadingZeros;

var state = new EncodeState(rawBase58, rawLeadingZeros, digitCount, Base58BitcoinTables.BitcoinChars, (byte)'1', inLeadingZeros);
var state = new EncodeState<TAlphabet>(rawBase58, rawLeadingZeros, digitCount, inLeadingZeros);
return string.Create(state.OutputLength, state, static (span, s) => s.EmitForward(span));
}

Expand Down Expand Up @@ -344,7 +344,7 @@ private static int EncodeBitcoin64FastToBytes(ReadOnlySpan<byte> data, Span<byte
ThrowHelper.ThrowDestinationTooSmall(nameof(destination));
}

var state = new EncodeState(rawBase58, rawLeadingZeros, digitCount, Base58BitcoinTables.BitcoinChars, (byte)'1', inLeadingZeros);
var state = new EncodeState<TAlphabet>(rawBase58, rawLeadingZeros, digitCount, inLeadingZeros);
state.EmitForward(destination);
return outputLength;
}
Expand Down Expand Up @@ -419,28 +419,23 @@ private static int ComputeBitcoin64FastRaw(ReadOnlySpan<byte> data, Span<byte> r
return rawLeadingZeros;
}

private readonly ref struct EncodeState
private readonly ref struct EncodeState<T>
where T : struct, IBase58Alphabet
{
public readonly ReadOnlySpan<byte> Digits;
public readonly ReadOnlySpan<byte> Alphabet;
public readonly int DigitStart;
public readonly int DigitCount;
public readonly byte LeadingFill;
public readonly int LeadingCount;

public EncodeState(
ReadOnlySpan<byte> digits,
int digitStart,
int digitCount,
ReadOnlySpan<byte> alphabet,
byte leadingFill,
int leadingCount)
{
Digits = digits;
DigitStart = digitStart;
DigitCount = digitCount;
Alphabet = alphabet;
LeadingFill = leadingFill;
LeadingCount = leadingCount;
}

Expand All @@ -451,14 +446,15 @@ public void EmitForward<TChar>(Span<TChar> destination)
{
if (LeadingCount > 0)
{
destination[..LeadingCount].Fill(TChar.CreateTruncating(LeadingFill));
destination[..LeadingCount].Fill(TChar.CreateTruncating(T.FirstCharacter));
}

int index = LeadingCount;
int end = DigitStart + DigitCount;
ReadOnlySpan<byte> alphabet = T.Characters;
for (int i = DigitStart; i < end; i++)
{
destination[index++] = TChar.CreateTruncating((ushort)Alphabet[Digits[i]]);
destination[index++] = TChar.CreateTruncating((ushort)alphabet[Digits[i]]);
}
}

Expand All @@ -467,13 +463,14 @@ public void EmitReverse<TChar>(Span<TChar> destination)
{
if (LeadingCount > 0)
{
destination[..LeadingCount].Fill(TChar.CreateTruncating(LeadingFill));
destination[..LeadingCount].Fill(TChar.CreateTruncating(T.FirstCharacter));
}

int index = LeadingCount;
ReadOnlySpan<byte> alphabet = T.Characters;
for (int i = DigitStart + DigitCount - 1; i >= DigitStart; i--)
{
destination[index++] = TChar.CreateTruncating((ushort)Alphabet[Digits[i]]);
destination[index++] = TChar.CreateTruncating((ushort)alphabet[Digits[i]]);
}
}
}
Expand Down
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