How to Read Multiline Responses with CR/LF Delimiter in Go?

Reading Multiline Responses with CR/LF Delimiter in Go

When implementing a Beanstalkd client in Go, it's necessary to read multiline responses that are delimited by both the newline character (n) and the carriage return character (r). The default function bufio.ReadLine only supports delimiting by n.

Reading Until CRLF

To read until the CRLF delimiter, you can use bufio.Scanner with a custom SplitFunc function:

<code class="go">import (
    "bufio"
    "fmt"
    "io"

    "bytes"
)

func ScanCRLF(data []byte, atEOF bool) (advance int, token []byte, err error) {
    if atEOF && len(data) == 0 {
        return 0, nil, nil
    }
    if i := bytes.Index(data, []byte{'\r', '\n'}); i >= 0 {
        return i + 2, dropCR(data[0:i]), nil
    }
    if atEOF {
        return len(data), dropCR(data), nil
    }
    return 0, nil, nil
}</code>

In this case, dropCR removes the trailing 'r' character from the token.

You can then use a bufio.Scanner with the ScanCRLF function to read the data:

<code class="go">scanner := bufio.NewScanner(this.reader)
scanner.Split(ScanCRLF)
for scanner.Scan() {
    fmt.Println(scanner.Text())
}</code>

Alternatively, bufio.NewReaderSize can be used to read a specific length:

<code class="go">var nr_of_bytes int
nr_of_bytes, _ = strconv.Atoi(res)
buf := make([]byte, nr_of_bytes)
_, _ = io.ReadAtLeast(this.reader,buf, nr_of_bytes)</code>

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