StringExtensions

Partially forked from Community Toolkit.

Utility class providing high performance extension methods for working with the string type.

StringExtensions is a utility class that provides extension methods for the string type, including getting references to string elements, and counting the number of occurrences of a character in a string.

Methods

DangerousGetReference

public static ref char DangerousGetReference(this string text)

Returns a reference to the first element within a given string, with no bounds checks. It is the caller's responsibility to perform bounds checks when dereferencing the returned value.

DangerousGetReferenceAt

public static ref char DangerousGetReferenceAt(this string text, int i)

Returns a reference to an element at a specified index within a given string, with no bounds checks. It is the caller's responsibility to ensure the i parameter is valid.

Count

public static int Count(this string text, char c)

Counts the number of occurrences of a given character in a target string instance.

GetHashCodeFast

SIMD method currently restricted to .NET 7+. PRs for backports are welcome.

Will produce different hashes depending on runtime or CPU.

Optimised for File Paths specifically

public static nuint GetHashCodeFast(string text)
public static unsafe nuint GetHashCodeFast(this ReadOnlySpan<char> text)

Faster hashcode for strings; but does not randomize between application runs.

Use this method if and only if 'Denial of Service' attacks are not a concern (i.e. never used for free-form user input), or are otherwise mitigated.

This method does not provide guarantees about producing the same hash across different machines or library versions, or runtime; only for the current process. Instead, it prioritises speed over all.

GetHashCodeLowerFast

SIMD method currently restricted to .NET 7+. PRs for backports are welcome.

Will produce different hashes depending on runtime or CPU.

Optimised for File Paths specifically

public static nuint GetHashCodeLowerFast(this string text)
public static unsafe nuint GetHashCodeLowerFast(this ReadOnlySpan<char> text)

Faster hashcode for strings, hashed in lower (invariant) case; does not randomize between application runs.

Use this method if and only if 'Denial of Service' attacks are not a concern (i.e. never used for free-form user input), or are otherwise mitigated.

This method does not provide guarantees about producing the same hash across different machines or library versions, or runtime; only for the current process. Instead, it prioritises speed over all.

ToLowerInvariantFast

public static string ToLowerInvariantFast(this string text)
public static unsafe void ToLowerInvariantFast(this ReadOnlySpan<char> text, Span<char> target)

Converts the given string to lower case (invariant casing) using the fastest possible implementation. This method is optimized for performance but currently has limitations for short non-ASCII inputs.

ToUpperInvariantFast

public static string ToUpperInvariantFast(this string text)
public static unsafe void ToUpperInvariantFast(this ReadOnlySpan<char> text, Span<char> target)

Converts the given string to upper case (invariant casing) using the fastest possible implementation. This method is optimized for performance but currently has limitations for short non-ASCII inputs.

Usage

Get Reference to First Element in String

string text = "Hello, world!";
ref char firstCharRef = ref text.DangerousGetReference();

Get Reference to Element at Index in String

string text = "Hello, world!";
int index = 4;
ref char charAtIndexRef = ref text.DangerousGetReferenceAt(index);

Count Character Occurrences in String

string text = "Hello, world!";
char targetChar = 'l';
int count = text.Count(targetChar);

Get Fast Hash Code

string text = "Hello, world!";
nuint fastHashCode = text.GetHashCodeFast();

Get Lower Case Hash Code

string text = "Hello, World!";
nuint lowerCaseHashCode = text.GetHashCodeLowerFast();

Convert String to Lower Case Invariant Fast

string text = "Hello, WORLD!";
string lowerInvariant = text.ToLowerInvariantFast(); // hello, world!

Convert String to Upper Case Invariant Fast

string text = "hello, world!";
string upperInvariant = text.ToUpperInvariantFast(); // HELLO, WORLD!

Convert ReadOnlySpan to Lower Case Invariant Fast

string text = "Hello, WORLD!";
Span<char> target = stackalloc char[textSpan.Length]; // Careful with string length!
text.AsSpan().ToLowerInvariantFast(target); // hello, world! (on stack)

Convert ReadOnlySpan to Upper Case Invariant Fast

string text = "hello, world!";
Span<char> target = stackalloc char[textSpan.Length]; // Careful with string length!
text.AsSpan().ToLowerInvariantFast(target); // HELLO, WORLD! (on stack)