Byte Array ExampleCreate, test, and measure byte arrays. Byte arrays are similar to other kinds of arrays.
This page was last reviewed on Nov 14, 2022.
Byte array. With byte arrays, we can store binary data. This data may be part of a data file, image file, compressed file or downloaded server response.
Shows a byte array
Array info. With byte arrays, we have an ideal representation of this data. The byte array type allows us to store low-level representations. It is useful in optimization.
Display example. To begin, we create a small byte array in a C# program. Byte arrays can represent any values, but each individual byte can only hold a certain range.
Part 1 We create a byte array of 3 bytes. We store the minimum byte value, and the maximum byte value, in the array elements.
Part 2 We use a foreach-loop to display all the byte elements in the byte array.
Shows a byte array
using System; class Program { static void Main() { // Part 1: create byte array. byte[] data = new byte[3]; data[0] = byte.MinValue; data[1] = 0; data[2] = byte.MaxValue; // Part 2: display byte data. foreach (var element in data) { Console.WriteLine(element); } } }
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Memory example. Here we allocate a byte array on the managed heap. The program measures the memory usage of the managed heap before and after this allocation occurs.
Memory The GC.GetTotalMemory method gathers the memory usage figures from the system before and after the allocation of the byte array.
Then The byte array variable is assigned a reference to 3 million bytes in an array allocated on the managed heap.
Result Allocating a 3 million element array of bytes causes 3 million bytes to be added to the memory usage of the program.
Tip Here we find that a byte array is a precise representation of bytes, not a higher-level construct.
using System; class Program { static void Main() { byte[] array1 = null; // // Allocate three million bytes and measure memory usage. // long bytes1 = GC.GetTotalMemory(false); array1 = new byte[1000 * 1000 * 3]; array1[0] = 0; long bytes2 = GC.GetTotalMemory(false); Console.WriteLine(bytes2 - bytes1); } }
Read bytes. We read in a byte array from a file with the System.IO namespace. An easy way to read a file into a binary array is the File.ReadAllBytes method in the File class.
using System; using System.IO; class Program { static void Main() { byte[] array = File.ReadAllBytes("C:\\profiles\\file.bin"); Console.WriteLine(array[0]); Console.WriteLine(array[1]); Console.WriteLine(array[2]); } }
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ToBase64String. When we have a byte array, we do not just need to leave the data as a byte array. We can convert it to a string with ToBase64String.
Here We load a JPG image on the disk into a byte array, and then encode it as a string. This can be put in CSS or HTML files directly.
using System; using System.IO; class Program { static void Main() { byte[] data = File.ReadAllBytes(@"C:\perls\i\2d-adventurers-map-background.jpg"); // Get base 64. string result = Convert.ToBase64String(data); // Write first 20 chars. Console.WriteLine("BASE64: " + result.Substring(0, 20) + "..."); } }
BASE64: /9j/2wCEAAgGBgYGBggG...
Test byte array. A GZIP file must have certain bytes in its first few bytes. We use IsGZipHeader to test a byte array to see if it contains GZIP data.
Note The first part of Main reads in a GZIP file, "2About.gz". The result value from IsGZipHeader on this file is true.
GZipTool This class is a public static class, which means you can access it from other namespaces and files. It contains IsGZipHeader.
IsGZipHeader This method returns true if the byte data passed to it contains the values 31 and 139 in its first two bytes.
using System; using System.IO; class Program { static void Main() { byte[] gzip = File.ReadAllBytes("2About.gz"); Console.WriteLine(GZipTool.IsGZipHeader(gzip)); byte[] text = File.ReadAllBytes("Program.cs"); Console.WriteLine(GZipTool.IsGZipHeader(text)); } } /// <summary> /// GZIP utility methods. /// </summary> public static class GZipTool { /// <summary> /// Checks the first two bytes in a GZIP file, which must be 31 and 139. /// </summary> public static bool IsGZipHeader(byte[] arr) { return arr.Length >= 2 && arr[0] == 31 && arr[1] == 139; } }
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Seek, read. We use Seek() on some Stream classes to read a part of a file into a byte array. It is faster to read in an entire byte array at once. This uses the file system's buffering.
BinaryWrite. ASP.NET uses byte arrays in its internal code. We can use the BinaryWrite method and provide a byte array parameter to achieve a fast write to the HTTP response.
WebClient. We can download data over the Internet (or other net work) with a network connection with WebClient. We directly access the bytes of any server's response.
GZipStream. This allows us to use a byte array buffer for expanding or compressing GZIP-encoded data. This is an easy way to implement compression or decompression for web applications.
File system caching. With byte arrays, you are usually just storing the exact data from the file system in the memory of your program.
However In some cases, this actually duplicates the Windows file system cache mechanism that is optimized for this exact purpose.
Note Byte array caches on the file system can improve or degrade performance in various situations.
BinaryReader. This class allows us to imperatively read in a binary file with more helper methods than testing the bytes yourself.
A review. We looked at the byte array type, seeing its memory allocation statistics. Next we provided pointers to further information on the byte array type.
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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.
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