How to use the io.LimitedReader to restrict the number of bytes read from an input source in Go?

In Go, the io.LimitedReader type allows you to limit the number of bytes read from an input source. It wraps an io.Reader and restricts the total number of bytes that can be read from it. Here's how to use it:

Import the necessary packages:

import (
	"io"
	"io/ioutil"
)

Create an io.Reader that represents your input source. It could be a file, network connection, or any other type that implements the io.Reader interface. In this example, let's use a bytes.Buffer as the input source:

input := bytes.NewBufferString("Hello, World!")

Create an io.LimitedReader by providing the input source and the maximum number of bytes to be read:

limit := int64(5) // Maximum of 5 bytes to be read
limitedReader := &io.LimitedReader{
    R: input,
    N: limit,
}

Read from the io.LimitedReader using the io.ReadFull() function or any other means of reading bytes from an io.Reader:

buffer := make([]byte, limit)
_, err := io.ReadFull(limitedReader, buffer)
if err != nil && err != io.ErrUnexpectedEOF {
    // Handle the error
}

In this example, io.ReadFull() attempts to read exactly limit number of bytes into the buffer. It returns io.ErrUnexpectedEOF if fewer than limit bytes are read.

Process or display the read data as needed:

fmt.Println(string(buffer))

In this case, it will print "Hello" as only the first 5 bytes were read.

By using io.LimitedReader, you can restrict the number of bytes read from an input source without modifying the source itself.