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Convert hex string to byte array: .NET 10 and span-bounded pointer loops #2317

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9436ae3
Convert hex string to byte array: move to .NET 10, bound pointer loop…
vladimir-pecanac-main Oct 18, 2026
7b72a97
Convert hex string to byte array: align two lines with the article's …
vladimir-pecanac-main Oct 18, 2026
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5 changes: 2 additions & 3 deletions ...ray/src/ConvertHexStringToByteArrayBenchmark/ConvertHexStringToByteArrayBenchmarks.csproj
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Original file line number Diff line number Diff line change
@@ -1,13 +1,12 @@
<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<OutputType>Exe</OutputType>
<TargetFramework>net7.0</TargetFramework>
<TargetFramework>net10.0</TargetFramework>
<ImplicitUsings>enable</ImplicitUsings>
<Nullable>enable</Nullable>
</PropertyGroup>
<ItemGroup>
<PackageReference Include="BenchmarkDotNet" Version="0.13.5" />
<PackageReference Include="CommunityToolkit.HighPerformance" Version="8.2.0" />
<PackageReference Include="BenchmarkDotNet" Version="0.15.8" />
</ItemGroup>
<ItemGroup>
<ProjectReference Include="..\ConvertHexStringToByteArrayLibrary\ConvertHexStringToByteArrayLibrary.csproj" />
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2 changes: 1 addition & 1 deletion ...ns-arrays/ConvertHexStringToByteArray/src/ConvertHexStringToByteArrayBenchmark/Program.cs
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@@ -1,4 +1,4 @@
using BenchmarkDotNet.Running;
using ConvertHexStringToByteArray.Benchmarks;

BenchmarkRunner.Run<ConvertHexStringToByteArrayBenchmarks>();
BenchmarkRunner.Run<ConvertHexStringToByteArrayBenchmarks>(args: args);
2 changes: 1 addition & 1 deletion ...yteArray/src/ConvertHexStringToByteArrayConsole/ConvertHexStringToByteArrayConsole.csproj
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@@ -1,7 +1,7 @@
<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<OutputType>Exe</OutputType>
<TargetFramework>net7.0</TargetFramework>
<TargetFramework>net10.0</TargetFramework>
<ImplicitUsings>enable</ImplicitUsings>
<Nullable>enable</Nullable>
</PropertyGroup>
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4 changes: 4 additions & 0 deletions ...ions-arrays/ConvertHexStringToByteArray/src/ConvertHexStringToByteArrayConsole/Program.cs
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Expand Up @@ -17,5 +17,9 @@
result = ConversionHelpers.FromHexWithLookup(input);
PrintResult(nameof(ConversionHelpers.FromHexWithLookup), result);

Span<byte> buffer = stackalloc byte[8];
var status = Convert.FromHexString("ABC", buffer, out var charsConsumed, out var bytesWritten);
Console.WriteLine($"odd: {status} consumed={charsConsumed} written={bytesWritten}");

static void PrintResult(string method, IEnumerable<byte> input) =>
Console.WriteLine($"{method}: \t[{string.Join(',', input)}]");
15 changes: 9 additions & 6 deletions ...s/ConvertHexStringToByteArray/src/ConvertHexStringToByteArrayLibrary/ConversionHelpers.cs
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Expand Up @@ -20,7 +20,7 @@ public static byte[] FromHexWithModularArithmetic(ReadOnlySpan<char> input)

var dest = new byte[input.Length >> 1];
for (int i = 0, j = 0; j < dest.Length; j++)
dest[j] = (byte)((PerformModularArithmeticCalculation(input[i++]) << 4) +
dest[j] = (byte) ((PerformModularArithmeticCalculation(input[i++]) << 4) +
PerformModularArithmeticCalculation(input[i++]));

return dest;
Expand Down Expand Up @@ -53,7 +53,8 @@ public static unsafe byte[] FromHexWithSwitchComputation(ReadOnlySpan<char> inpu
{
var destPtr = d;
var srcPtr = s;
while (*srcPtr != 0)
var srcEnd = s + input.Length;
while (srcPtr < srcEnd)
{
var result = (byte) (ComputeNibbleFromHexChar(*srcPtr++) << 4);
result |= ComputeNibbleFromHexChar(*srcPtr++);
Expand Down Expand Up @@ -89,7 +90,8 @@ public static unsafe byte[] FromHexWithBitManipulation(ReadOnlySpan<char> input)
{
var sPtr = &srcPtr[0];
var dPtr = &destPtr[0];
while (*sPtr != 0)
var sEnd = sPtr + input.Length;
while (sPtr < sEnd)
{
var hi = PerformBitManipulation(*sPtr++);
var lo = PerformBitManipulation(*sPtr++) & 0x0F;
Expand Down Expand Up @@ -127,14 +129,15 @@ public static unsafe byte[] FromHexWithLookup(ReadOnlySpan<char> input)
{
var s = &inputRef[0];
var d = destRef;
var end = s + input.Length;

while (*s != 0)
while (s < end)
{
byte lowValue;

if (*s > 102 || (*d = hiRef[*s++]) == 255 ||
*s > 102 || (lowValue = lowRef[*s++]) == 255 )
throw new ArgumentException($"Invalid character found in string: '{*s}'", nameof(input));
*s > 102 || (lowValue = lowRef[*s++]) == 255)
throw new ArgumentException("Input contains a non-hex character", nameof(input));

*d++ += lowValue;
}
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2 changes: 1 addition & 1 deletion ...yteArray/src/ConvertHexStringToByteArrayLibrary/ConvertHexStringToByteArrayLibrary.csproj
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<TargetFramework>net7.0</TargetFramework>
<TargetFramework>net10.0</TargetFramework>
<ImplicitUsings>enable</ImplicitUsings>
<Nullable>enable</Nullable>
<AllowUnsafeBlocks>true</AllowUnsafeBlocks>
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12 changes: 12 additions & 0 deletions ...exStringToByteArray/test/ConvertHexStringToByteArrayUnitTests/ConvertHexByteArrayTests.cs
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Expand Up @@ -142,4 +142,16 @@ public void GivenLookupMethod_WhenInvalidHexDataIsProvided_ThenThrowsArgumentExc
{
Assert.Throws<ArgumentException>(() => ConversionHelpers.FromHexWithLookup(source));
}
[Fact]
public void GivenSliceOfLongerString_WhenConverting_ThenEveryMethodStopsAtTheEndOfTheSlice()
{
var slice = "DEADZZ".AsSpan(0, 4);
var expected = new byte[] {222, 173};

Assert.Equal(expected, ConversionHelpers.FromHexWithModularArithmetic(slice));
Assert.Equal(expected, ConversionHelpers.FromHexWithSwitchComputation(slice));
Assert.Equal(expected, ConversionHelpers.FromHexWithBitManipulation(slice));
Assert.Equal(expected, ConversionHelpers.FromHexWithConvert(slice));
Assert.Equal(expected, ConversionHelpers.FromHexWithLookup(slice));
}
}
10 changes: 5 additions & 5 deletions ...ray/test/ConvertHexStringToByteArrayUnitTests/ConvertHexStringToByteArrayUnitTests.csproj
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@@ -1,19 +1,19 @@
<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<TargetFramework>net7.0</TargetFramework>
<TargetFramework>net10.0</TargetFramework>
<ImplicitUsings>enable</ImplicitUsings>
<Nullable>enable</Nullable>
<IsPackable>false</IsPackable>
<IsTestProject>true</IsTestProject>
</PropertyGroup>
<ItemGroup>
<PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.5.0" />
<PackageReference Include="xunit" Version="2.4.2" />
<PackageReference Include="xunit.runner.visualstudio" Version="2.4.5">
<PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.11.0" />
<PackageReference Include="xunit" Version="2.9.3" />
<PackageReference Include="xunit.runner.visualstudio" Version="4.0.1">
<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
<PrivateAssets>all</PrivateAssets>
</PackageReference>
<PackageReference Include="coverlet.collector" Version="3.2.0">
<PackageReference Include="coverlet.collector" Version="10.1.0">
<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
<PrivateAssets>all</PrivateAssets>
</PackageReference>
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