C# Span Examples - Dot Net Perls

Fill. This program creates a Span of ints by passing an int array to the Span constructor. It then calls fill to change all elements to the value 5.

using System; Span<int> span = new Span<int>(new int[] { 1, 2, 3 }); // Fill span with value 5. span.Fill(5); foreach (int value in span) { Console.WriteLine(value); }

5 5 5

ToArray. We can create a Span from a same-typed array. And in the same way, we can call ToArray to convert a span into an array of the same type.

using System; var animals = new string[] { "bird", "frog", "dog" }; Span<string> span = new Span<string>(animals); // Use ToArray to convert a span into an array. string[] result = span.ToArray(); Console.WriteLine("RESULT: {0}", string.Join(",", result)); Console.WriteLine("RESULT LENGTH: {0}", result.Length);

RESULT: bird,frog,dog RESULT LENGTH: 3

Slice. The Slice() method is like Substring for Spans—it receives a start index and an optional length as its arguments. It returns a new Span.

Part 1 We invoke Slice on the initial Span with 1 argument—this span starts at index 1 and covers the rest of the elements.

Part 2 We call Slice with 2 arguments. Argument 1 is the start index, and argument 2 is the desired length.

using System; Span<int> span = new Span<int>(new int[] { 1, 2, 3 }); // Part 1: take slice at index 1 through the end. var slice1 = span.Slice(1); Console.WriteLine(string.Join(",", slice1.ToArray())); // Part 2: take slice at index 0 with length 2. var slice2 = span.Slice(0, 2); Console.WriteLine(string.Join(",", slice2.ToArray()));

2,3 1,2

Pointer. We can create a Span from a pointer to memory in .NET Core. In this example, we use a fixed buffer as the pointer. We must specify the length of the span.

Part 1 We use the fixed keyword to assign to elements in the fixed buffer. We assign 3 elements.

fixed

Part 2 We create a Span from the fixed buffer struct. We then use the foreach-loop on the Span to print the elements to the screen.

foreach

Console.WriteLine

using System; unsafe struct FixedBufferExample { public fixed int _buffer[1024]; } class Program { static FixedBufferExample _fixedBufferExample; static void Main() { unsafe { // Part 1: store values in fixed buffer. fixed (int* buffer = _fixedBufferExample._buffer) { buffer[0] = 10; buffer[1] = 20; buffer[2] = 30; // Part 2: create span from fixed buffer struct. Span<int> span = new Span<int>(buffer, 3); foreach (int value in span) { Console.WriteLine("BUFFER ELEMENT: {0}", value); } } } } }

BUFFER ELEMENT: 10 BUFFER ELEMENT: 20 BUFFER ELEMENT: 30

Empty. To create an empty span, we can use the Span.Empty property. We must specify a type parameter on the Empty property. The resulting span has a length of 0.

using System; Span<char> span = Span<char>.Empty; Console.WriteLine("EMPTY LENGTH: {0}", span.Length);

EMPTY LENGTH: 0

ToString. Here we create a span of chars from a char array. We call ToCharArray to get a char array from a string. With a span, we can modify elements by assigning them.

String ToCharArray

char Array

Then We can call ToString to convert a span into its string representation. For a char Span, this is a useful method.

using System; Span<char> span = new Span<char>("bird".ToCharArray()); span[1] = 'a'; string result = span.ToString(); Console.WriteLine("RESULT: {0}", result);

RESULT: bard

Contains. Much like a string, we can use Contains to search a span. With a Span of chars, we can find a specific char—here we find the char "c" in the Span.

using System; Span<char> span = new Span<char>(new char[] { 'a', 'b', 'c' }); // Use Contains to search a span. if (span.Contains('c')) { Console.WriteLine("SPAN CONTAINS C"); }

SPAN CONTAINS C

Dot Net Perls is a collection of tested code examples. Pages are continually updated to stay current, with code correctness a top priority.

Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.

This page was last updated on May 13, 2023 (simplify).

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