Day 25: Byte Serialization

Serialization converts data structures to bytes. This is fundamental for Solana where all account data is stored as bytes!

Why This Matters for Solana

Solana accounts store data as raw bytes (&[u8]). You need to serialize (write) and deserialize (read) your data structures.

Endianness

Byte order matters when converting multi-byte values:

let num: u32 = 0x12345678;

// Little-endian (Solana uses this)
// [0x78, 0x56, 0x34, 0x12]

// Big-endian
// [0x12, 0x34, 0x56, 0x78]

Converting Integers to Bytes

let n: u64 = 1000;

// To bytes (little-endian)
let bytes: [u8; 8] = n.to_le_bytes();

// From bytes
let restored = u64::from_le_bytes(bytes);

Manual Serialization

struct Transfer {
    amount: u64,
    recipient: [u8; 4],
}

impl Transfer {
    fn to_bytes(&self) -> [u8; 12] {
        let mut bytes = [0u8; 12];
        
        // Copy amount (8 bytes, little-endian)
        bytes[0..8].copy_from_slice(&self.amount.to_le_bytes());
        
        // Copy recipient (4 bytes)
        bytes[8..12].copy_from_slice(&self.recipient);
        
        bytes
    }
    
    fn from_bytes(data: &[u8; 12]) -> Self {
        let amount = u64::from_le_bytes(data[0..8].try_into().unwrap());
        let mut recipient = [0u8; 4];
        recipient.copy_from_slice(&data[8..12]);
        
        Self { amount, recipient }
    }
}

The Task

Implement to_bytes() and from_bytes() for the Transfer struct.

Requirements

Amount is serialized as little-endian u64 (8 bytes)
Recipient is copied directly (4 bytes)
Total: 12 bytes
Round-trip must preserve data

Hints

fn to_bytes(&self) -> [u8; 12] {
    let mut bytes = [0u8; 12];
    bytes[0..8].copy_from_slice(&self.amount.to_le_bytes());
    bytes[8..12].copy_from_slice(&self.recipient);
    bytes
}

fn from_bytes(data: &[u8; 12]) -> Self {
    let amount = u64::from_le_bytes(data[0..8].try_into().unwrap());
    let mut recipient = [0u8; 4];
    recipient.copy_from_slice(&data[8..12]);
    Self { amount, recipient }
}