⚡ z85

A Go library for Z85 encoding and decoding, implementing the ZeroMQ Base-85 encoding.

Z85 encodes binary data into printable ASCII characters using an 85-character alphabet. Every 4 bytes of input produce 5 bytes of output, resulting in a 25% size increase (compared to 33% for Base64).

Installation

go get github.com/tortxof/z85

Library Usage

package main

import (
	"fmt"

	"github.com/tortxof/z85"
)

func main() {
	// Encode binary data
	data := []byte{0x86, 0x4F, 0xD2, 0x6F, 0xB5, 0x59, 0xF7, 0x5B}
	encoded := z85.Encode(data)
	fmt.Println(string(encoded)) // HelloWorld

	// Decode Z85 string
	decoded := z85.Decode([]byte("HelloWorld"))
	fmt.Printf("%x\n", decoded) // 864fd26fb559f75b
}

API

Byte Slice Functions

• Encode(data []byte) []byte - Encode a byte slice to Z85
• Decode(data []byte) []byte - Decode a Z85 byte slice to binary
• EncodeChunk(chunk [4]byte) [5]byte - Encode a single 4-byte chunk
• DecodeChunk(chunk [5]byte) [4]byte - Decode a single 5-byte chunk

Partial chunks are handled automatically with internal padding.

Note: The decode functions do not validate input. Bytes outside the Z85 alphabet are silently treated as the character '0' (value 0). Ensure input contains only valid Z85 characters if correctness is critical.

Streaming API

• NewEncoder(w io.Writer) io.WriteCloser - Create a streaming encoder
• NewDecoder(w io.Writer) io.WriteCloser - Create a streaming decoder

The streaming types implement io.WriteCloser. Data written to the encoder/decoder is processed and written to the underlying writer. Call Close() to flush any buffered partial chunks.

// Streaming encode
var buf bytes.Buffer
encoder := z85.NewEncoder(&buf)
encoder.Write([]byte{0x86, 0x4F, 0xD2, 0x6F})
encoder.Write([]byte{0xB5, 0x59, 0xF7, 0x5B})
encoder.Close()
fmt.Println(buf.String()) // HelloWorld

// Streaming decode
var out bytes.Buffer
decoder := z85.NewDecoder(&out)
io.Copy(decoder, strings.NewReader("HelloWorld"))
decoder.Close()
fmt.Printf("%x\n", out.Bytes()) // 864fd26fb559f75b

CLI Tools

Build the command-line tools:

go build ./cmd/z85encode
go build ./cmd/z85decode

Usage:

# Encode
echo -n "test" | ./z85encode
# Output: By/Jn

# Decode
echo -n "By/Jn" | ./z85decode
# Output: test

# Encode a file
./z85encode < input.bin > output.z85

# Decode a file
./z85decode < input.z85 > output.bin

Testing

# Run tests
go test ./...

# Run benchmarks
go test -bench=.

# Run fuzz tests
go test -fuzz=FuzzZ85RoundTrip
go test -fuzz=FuzzStreamRoundTrip

License

See LICENSE for details.