Golang bytes.Contains Function

The bytes.Contains function in Golang is part of the bytes package and is used to check if a specified byte slice is present within another byte slice. This function is useful for searching and matching patterns or substrings within larger byte slices.

Table of Contents

1. Introduction
2. bytes.Contains Function Syntax
3. Examples
   • Basic Usage
   • Case-Sensitive Search
   • Searching in Binary Data
4. Real-World Use Case
5. Conclusion

Introduction

The bytes.Contains function checks whether a specified byte slice is a sub-slice of another byte slice. It returns true if the sub-slice is found, and false otherwise. 

This function is particularly useful when you need to determine the presence of a specific pattern or substring within a larger byte slice, such as searching for keywords, tokens, or specific data sequences.

bytes.Contains Function Syntax

The syntax for the bytes.Contains function is as follows:

func Contains(b, subslice []byte) bool

Parameters:

• b: The byte slice in which to search.
• subslice: The byte slice to search for within b.

Returns:

• bool: true if subslice is found within b, false otherwise.

Examples

Basic Usage

This example demonstrates how to use the bytes.Contains function to check if a byte slice contains a specific sub-slice.

Example

package main

import (
	"bytes"
	"fmt"
)

func main() {
	// Define the main byte slice
	data := []byte("Hello, Golang!")

	// Define the sub-slice to search for
	subSlice := []byte("Golang")

	// Check if the sub-slice is contained within the main slice
	if bytes.Contains(data, subSlice) {
		fmt.Println("Sub-slice found!")
	} else {
		fmt.Println("Sub-slice not found.")
	}
}

Output:

Sub-slice found!

Case-Sensitive Search

The bytes.Contains function performs a case-sensitive search, meaning that it distinguishes between uppercase and lowercase letters.

Example

package main

import (
	"bytes"
	"fmt"
)

func main() {
	// Define the main byte slice
	data := []byte("Hello, Golang!")

	// Define a sub-slice with different casing
	subSlice := []byte("golang")

	// Check if the sub-slice is contained within the main slice
	if bytes.Contains(data, subSlice) {
		fmt.Println("Sub-slice found!")
	} else {
		fmt.Println("Sub-slice not found.")
	}
}

Output:

Sub-slice not found.

Searching in Binary Data

The bytes.Contains function can also be used to search for specific sequences in binary data.

Example

package main

import (
	"bytes"
	"fmt"
)

func main() {
	// Define the main binary data
	data := []byte{0x01, 0x02, 0x03, 0x04, 0x05}

	// Define the binary sub-slice to search for
	subSlice := []byte{0x03, 0x04}

	// Check if the binary sub-slice is contained within the main binary data
	if bytes.Contains(data, subSlice) {
		fmt.Println("Binary sub-slice found!")
	} else {
		fmt.Println("Binary sub-slice not found.")
	}
}

Output:

Binary sub-slice found!

Explanation:

• bytes.Contains is used to check if one byte slice is contained within another.
• The function performs a case-sensitive search, meaning that "Golang" and "golang" would be treated as different sub-slices.
• It can be used with both text and binary data.

Real-World Use Case

Searching for Keywords in a Byte Stream

In real-world applications, bytes.Contains can be used to search for specific keywords or patterns within a byte stream, such as scanning a log file for specific events, detecting tokens in network packets, or searching for metadata in a binary file.

Example: Searching for a Keyword in Log Data

package main

import (
	"bytes"
	"fmt"
)

func main() {
	// Simulate log data as a byte slice
	logData := []byte("INFO: Application started\nERROR: Failed to connect to the database\nINFO: Application stopped")

	// Define the keyword to search for
	keyword := []byte("ERROR")

	// Check if the keyword is present in the log data
	if bytes.Contains(logData, keyword) {
		fmt.Println("Error found in log data.")
	} else {
		fmt.Println("No errors found in log data.")
	}
}

Output:

Error found in log data.

Explanation:

• The example shows how bytes.Contains can be used to search for specific keywords within log data, helping to identify errors or important events.

Conclusion

The bytes.Contains function in Go is used for checking the presence of a sub-slice within a byte slice. Whether you're working with text or binary data, this function provides an efficient way to search for specific patterns, keywords, or sequences. Its case-sensitive nature makes it suitable for precise searches, and it's especially useful in scenarios where you need to detect specific data within a larger dataset, such as log analysis, token detection, or metadata extraction.