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Merged
manigandham merged 12 commits into from
Apr 22, 2021
Merged

Speed and memory usage optimizations. #43

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9ca7ad8
Fix tests.
Daramant Apr 19, 2021
36bff2c
Added ReturnPooled() extension.
Daramant Apr 19, 2021
9000962
Renaming.
Daramant Apr 19, 2021
0ed33a2
Cached number powers.
Daramant Apr 19, 2021
fdac00e
Merge branch 'master' of https://github.com/ullmark/hashids.net
Daramant Apr 20, 2021
dac0c5f
Fix benchmark startup.
Daramant Apr 20, 2021
2dcc291
Small fixes.
Daramant Apr 20, 2021
b1c56d4
Fix conflicts.
Daramant Apr 21, 2021
953cfaa
Fix build.
Daramant Apr 21, 2021
75c14a8
Copy from original.
Daramant Apr 21, 2021
74d9b8c
Small fixes.
Daramant Apr 21, 2021
1e280f1
Speed and memory usage optimization.
Daramant Apr 21, 2021
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138 changes: 77 additions & 61 deletions src/Hashids.net/Hashids.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
using System.Text;
using System.Text.RegularExpressions;
using Microsoft.Extensions.ObjectPool;
using System.Buffers;

namespace HashidsNet
{
Expand All @@ -19,7 +20,10 @@ public partial class Hashids : IHashids
private const double SEP_DIV = 3.5;
private const double GUARD_DIV = 12.0;

private const int MaxNumberHashLength = 12; // Length of long.MaxValue;

private char[] _alphabet;
private long _alphabetLength;
private char[] _seps;
private char[] _guards;
private char[] _salt;
Expand Down Expand Up @@ -73,6 +77,8 @@ public Hashids(

SetupSeps();
SetupGuards();

_alphabetLength = _alphabet.Length;
}

private void SetupSeps()
Expand All @@ -85,9 +91,9 @@ private void SetupSeps()

ConsistentShuffle(_seps, _seps.Length, _salt, _salt.Length);

if (_seps.Length == 0 || ((float) _alphabet.Length / _seps.Length) > SEP_DIV)
if (_seps.Length == 0 || ((float)_alphabet.Length / _seps.Length) > SEP_DIV)
{
var sepsLength = (int) Math.Ceiling((float) _alphabet.Length / SEP_DIV);
var sepsLength = (int)Math.Ceiling((float)_alphabet.Length / SEP_DIV);

if (sepsLength == 1)
{
Expand All @@ -111,7 +117,7 @@ private void SetupSeps()

private void SetupGuards()
{
var guardCount = (int) Math.Ceiling(_alphabet.Length / GUARD_DIV);
var guardCount = (int)Math.Ceiling(_alphabet.Length / GUARD_DIV);

if (_alphabet.Length < 3)
{
Expand All @@ -131,7 +137,7 @@ private void SetupGuards()
/// </summary>
/// <param name="numbers">List of integers.</param>
/// <returns>Encoded hash string.</returns>
public virtual string Encode(params int[] numbers) => GenerateHashFrom(Array.ConvertAll(numbers, n => (long) n));
public virtual string Encode(params int[] numbers) => GenerateHashFrom(Array.ConvertAll(numbers, n => (long)n));

/// <summary>
/// Encodes the provided numbers into a hash string.
Expand Down Expand Up @@ -160,7 +166,7 @@ private void SetupGuards()
/// <param name="hash">Hash string to decode.</param>
/// <returns>Array of integers.</returns>
/// <exception cref="T:System.OverflowException">If the decoded number overflows integer.</exception>
public virtual int[] Decode(string hash) => Array.ConvertAll(GetNumbersFrom(hash), n => (int) n);
public virtual int[] Decode(string hash) => Array.ConvertAll(GetNumbersFrom(hash), n => (int)n);

/// <summary>
/// Decodes the provided hash into numbers.
Expand Down Expand Up @@ -202,8 +208,14 @@ public virtual string DecodeHex(string hash)
var numbers = DecodeLong(hash);

foreach (var number in numbers)
foreach (var ch in number.ToString("X").AsSpan().Slice(1))
builder.Append(ch);
{
var s = number.ToString("X");

for (var i = 1; i < s.Length; i++)
{
builder.Append(s[i]);
}
}

var result = builder.ToString();
_sbPool.Return(builder);
Expand All @@ -223,13 +235,14 @@ private string GenerateHashFrom(long[] numbers)

var builder = _sbPool.Get();

char[] buffer = null;
char[] shuffleBuffer = null;
var alphabet = _alphabet.CopyPooled();
var hashBuffer = ArrayPool<char>.Shared.Rent(MaxNumberHashLength);
try
{
var lottery = alphabet[numbersHashInt % _alphabet.Length];
var lottery = alphabet[numbersHashInt % _alphabetLength];
builder.Append(lottery);
buffer = CreatePooledBuffer(_alphabet.Length, lottery);
shuffleBuffer = CreatePooledBuffer(_alphabet.Length, lottery);

var startIndex = 1 + _salt.Length;
var length = _alphabet.Length - startIndex;
Expand All @@ -240,17 +253,20 @@ private string GenerateHashFrom(long[] numbers)

if (length > 0)
{
Array.Copy(alphabet, 0, buffer, startIndex, length);
Array.Copy(alphabet, 0, shuffleBuffer, startIndex, length);
}

ConsistentShuffle(alphabet, _alphabet.Length, shuffleBuffer, _alphabet.Length);
var hashLength = BuildReversedHash(number, alphabet, hashBuffer);

ConsistentShuffle(alphabet, _alphabet.Length, buffer, _alphabet.Length);
var last = Hash(number, alphabet, _alphabet.Length);

builder.Append(last);
for (var j = hashLength - 1; j > -1; j--)
{
builder.Append(hashBuffer[j]);
}

if (i + 1 < numbers.Length)
{
number %= last[0] + i;
number %= hashBuffer[hashLength - 1] + i;
var sepsIndex = number % _seps.Length;

builder.Append(_seps[sepsIndex]);
Expand All @@ -277,8 +293,8 @@ private string GenerateHashFrom(long[] numbers)

while (builder.Length < _minHashLength)
{
Array.Copy(alphabet, buffer, _alphabet.Length);
ConsistentShuffle(alphabet, _alphabet.Length, buffer, _alphabet.Length);
Array.Copy(alphabet, shuffleBuffer, _alphabet.Length);
ConsistentShuffle(alphabet, _alphabet.Length, shuffleBuffer, _alphabet.Length);
builder.Insert(0, alphabet, halfLength, _alphabet.Length - halfLength);
builder.Append(alphabet, 0, halfLength);

Expand All @@ -293,36 +309,35 @@ private string GenerateHashFrom(long[] numbers)
finally
{
alphabet.ReturnToPool();
buffer.ReturnToPool();
shuffleBuffer.ReturnToPool();
hashBuffer.ReturnToPool();
}

var result = builder.ToString();
_sbPool.Return(builder);
return result;
}

private char[] Hash(long input, char[] alphabet, int alphabetLength)
private int BuildReversedHash(long input, char[] alphabet, char[] hashBuffer)
{
var hash = new List<char>(4);

var length = 0;
do
{
hash.Add(alphabet[input % alphabetLength]);
input /= alphabetLength;
hashBuffer[length++] = alphabet[input % _alphabetLength];
input /= _alphabetLength;
} while (input > 0);

hash.Reverse();
return hash.ToArray();
return length;
}

private long Unhash(string input, char[] alphabet, int alphabetLength)
private long Unhash(string input, char[] alphabet)
{
long number = 0;

for (var i = 0; i < input.Length; i++)
{
var pos = Array.IndexOf(alphabet, input[i]);
number = number * alphabetLength + pos;
number = number * _alphabetLength + pos;
}

return number;
Expand All @@ -343,55 +358,56 @@ private long[] GetNumbersFrom(string hash)
i = 1;
}

var result = new List<long>();
var hashBreakdown = hashArray[i];
if (hashBreakdown[0] != default(char))
{
var lottery = hashBreakdown[0];
hashBreakdown = hashBreakdown.Substring(1);
var lottery = hashBreakdown[0];

hashArray = hashBreakdown.Split(_seps, StringSplitOptions.RemoveEmptyEntries);
if (lottery == default(char))
return Array.Empty<long>();

hashBreakdown = hashBreakdown.Substring(1);

char[] buffer = null;
var alphabet = _alphabet.CopyPooled();
try
{
buffer = CreatePooledBuffer(_alphabet.Length, lottery);
hashArray = hashBreakdown.Split(_seps, StringSplitOptions.RemoveEmptyEntries);

var startIndex = 1 + _salt.Length;
var length = _alphabet.Length - startIndex;
var result = new long[hashArray.Length];
char[] buffer = null;
var alphabet = _alphabet.CopyPooled();
try
{
buffer = CreatePooledBuffer(_alphabet.Length, lottery);

for (var j = 0; j < hashArray.Length; j++)
{
var subHash = hashArray[j];
var startIndex = 1 + _salt.Length;
var length = _alphabet.Length - startIndex;

if (length > 0)
{
Array.Copy(alphabet, 0, buffer, startIndex, length);
}
for (var j = 0; j < hashArray.Length; j++)
{
var subHash = hashArray[j];

ConsistentShuffle(alphabet, _alphabet.Length, buffer, _alphabet.Length);
result.Add(Unhash(subHash, alphabet, _alphabet.Length));
if (length > 0)
{
Array.Copy(alphabet, 0, buffer, startIndex, length);
}
}
finally
{
alphabet.ReturnToPool();
buffer.ReturnToPool();
}

if (EncodeLong(result.ToArray()) != hash)
{
result.Clear();
ConsistentShuffle(alphabet, _alphabet.Length, buffer, _alphabet.Length);
result[j] = Unhash(subHash, alphabet);
}
}
finally
{
alphabet.ReturnToPool();
buffer.ReturnToPool();
}

if (EncodeLong(result) == hash)
{
return result;
}

return result.ToArray();
return Array.Empty<long>();
}

private char[] CreatePooledBuffer(int alphabetLength, char lottery)
{
var buffer = System.Buffers.ArrayPool<char>.Shared.Rent(alphabetLength);
var buffer = ArrayPool<char>.Shared.Rent(alphabetLength);
buffer[0] = lottery;
Array.Copy(_salt, 0, buffer, 1, Math.Min(_salt.Length, alphabetLength - 1));
return buffer;
Expand Down
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