Constant V1_HEADER_LEN 

pub const V1_HEADER_LEN: usize = 24; // 24usize

Minimum v1 header length in bytes.

Layout (little-endian):

• magic: [u8; 4]
• flags: u16
• codec_id: u8
• header_len: u8
• schema_id: u64
• msg_type: u32
• msg_version: u16
• payload_len: u16