snippets

commit c43d0d5761f899d25f3531a0a6fc1969def3be80
parent e4eef5e3a00968b5c3077d3fda514a6fbcb43e49
Author: Vetle Haflan <vetle@haflan.dev>
Date:   Wed, 23 Nov 2022 21:04:07 +0100

deflate64: go snippet for compressing and base64 encoding (for kroki)

Diffstat:
A
deflate64.go
 | 
69
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 69 insertions(+), 0 deletions(-)
diff --git a/deflate64.go b/deflate64.go
@@ -0,0 +1,69 @@
+// Compress and encode, or decode and decompress
+// with base64 and deflate (zlib).
+// This can be useful for sending any data as text,
+// and it's the format used by kroki (https://kroki.io/).
+
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"compress/zlib"
+	"encoding/base64"
+	"fmt"
+	"io"
+	"os"
+)
+
+// Encode takes a string and returns an encoded string in deflate + base64 format
+// (stolen from https://docs.kroki.io/kroki/setup/encode-diagram/#go)
+
+func Encode(input string) (string, error) {
+	var buffer bytes.Buffer
+	writer, err := zlib.NewWriterLevel(&buffer, 9)
+	if err != nil {
+		return "", fmt.Errorf("failed to create the writer: %w", err)
+	}
+	_, err = writer.Write([]byte(input))
+	writer.Close()
+	if err != nil {
+		return "", fmt.Errorf("fail to create the payload: %w", err)
+	}
+	result := base64.URLEncoding.EncodeToString(buffer.Bytes())
+	return result, nil
+}
+
+func Decode(zippedB64 string) (string, error) {
+	result, err := base64.URLEncoding.DecodeString(zippedB64)
+	if err != nil {
+		return "", fmt.Errorf("failed to decode base64: %w", err)
+	}
+	rbuf := bytes.NewReader([]byte(result))
+	r, err := zlib.NewReader(rbuf)
+	if err != nil {
+		return "", fmt.Errorf("failed to create the reader: %w", err)
+	}
+	var buf bytes.Buffer
+	_, err = io.Copy(bufio.NewWriter(&buf), r)
+	return buf.String(), err
+}
+
+func main() {
+	if len(os.Args) < 3 {
+		fmt.Printf("Use: %v [encode|decode] <input>", os.Args[0])
+		os.Exit(1)
+	}
+	var result string
+	var err error
+	switch os.Args[1] {
+	case "decode":
+		result, err = Decode(os.Args[2])
+	default:
+		result, err = Encode(os.Args[2])
+	}
+	if err != nil {
+		fmt.Println("error:", err)
+	} else {
+		fmt.Println(result)
+	}
+}