Solana Cookbook

Serializing Data

When we talk about serialization we mean both serializing data as well as deserialization of data.

Serialization comes into play at a few points along Solana program and program accounts lifecycle:

  1. Serializing instruction data on to client
  2. Deserializing instruction data on the program
  3. Serializing Account data on the program
  4. Deserializing Account Data on the client

It is important that the above actions are all supported by the same serialization approach. The included snippets are demonstrating serialization using Borsh.

The samples in the remainder of this document are excerpts as taken from the Solana CLI Program Template

Setting up for Borsh Serialization

Libraries for Borsh must be setup for the Rust program, Rust client, Node and/or Python client.

[package]
name = "solana-cli-template-program-bpf"
version = "0.1.0"
edition = "2018"
license = "WTFPL"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[features]
no-entrypoint = []

[dependencies]
borsh = "0.9.0"
lazy_static = "1.4.0"
num-derive = "0.3"
num_enum = "0.5.1"
num-integer = "0.1.44"
num-traits = "0.2"
sol-template-shared = {path = "../shared"}
solana-program = "1.8.2"
thiserror = "1.0"

[dev-dependencies]
solana-program-test = "1.8.2"
solana-sdk = "1.8.2"

[lib]
crate-type = ["cdylib", "lib"]

[package]
name = "cli-program-template"
version = "0.1.5"
edition = "2018"
license = "WTFPL"
publish = false

[dependencies]
borsh = "0.9.0"
clap = "2.33.3"
lazy_static = "1.4.0"
serde = { version = "1.0.125", features = ["derive"] }
serde_yaml = "0.8.17"
sol-template-shared = {path = "shared"}
solana-clap-utils = "1.8.2"
solana-cli-config = "1.8.2"
solana-client = "1.8.2"
solana-logger = "1.8.2"
solana-remote-wallet = "1.8.2"
solana-sdk = "1.8.2"
tokio = { version = "1", features = ["full"] }

[workspace]
members = [
    "program",
    "shared",
]
[dev-dependencies]
lazy_static = "1.4.0"
solana-validator = "1.8.2"
solana-streamer = "1.8.2"

{
  "name": "ts-program-template",
  "version": "0.1.0",
  "description": "Sample TS App",
  "main": "client/nmain.ts",
  "author": "",
  "keywords": [],
  "workspace": "client/",
  "repository": {
    "type": "git",
    "url": "https: //github.com/hashblock/solana-cli-program-template"
  },
  "homepage": "https: //github.com/hashblock/solana-cli-program-template",
  "scripts": {
    "test:all": "npm run build:client && npm run test:client",
    "build:client": "rm -rf ./.dist/client && tsc ",
    "start": "node ./node_modules/.bin/mocha .dist/client/main.js",
    "test:client": "npm run start",
    "lint": "eslint --ext .ts client/* && prettier --check \"client/**/*.ts\"",
    "lint:fix": "eslint --ext .ts client/* --fix",
    "pretty": "prettier --write '{,client/**/}*.ts'"
  },
  "devDependencies": {
    "@tsconfig/recommended": "^1.0.1",
    "@types/chai": "^4.3.0",
    "@types/eslint": "^7.28.2",
    "@types/eslint-plugin-prettier": "^3.1.0",
    "@types/mkdirp": "^1.0.2",
    "@types/mocha": "^9.0.0",
    "@types/prettier": "^2.4.1",
    "@typescript-eslint/eslint-plugin": "^5.6.0",
    "@typescript-eslint/parser": "^5.6.0",
    "chai": "^4.3.4",
    "eslint": "^8.2.0",
    "eslint-config-google": "^0.14.0",
    "eslint-config-prettier": "^8.3.0",
    "eslint-plugin-prettier": "^4.0.0",
    "html-webpack-plugin": "^5.5.0",
    "mocha": "^9.1.3",
    "prettier": "^2.4.1",
    "start-server-and-test": "^1.14.0",
    "ts-node": "^10.4.0",
    "typescript": "^4.5.2"
  },
  "dependencies": {
    "@solana/web3.js": "^1.31.0",
    "borsh": "^0.7.0",
    "env": "^0.0.2",
    "fs": "^0.0.1-security",
    "mkdirp": "^1.0.4",
    "npm-check-updates": "^12.0.3",
    "sync-request": "^6.1.0",
    "update": "^0.4.2"
  }
}

borsh-construct==0.1.0
solana==0.20.0

How to serialize instruction data on the client

Serialize Instruction Data

If you are serializing outbound instruction data to send to a program it must mirror how the program deserializes the inbound instruction data.

In this template, an instruction data block is a serialized array containing, with examples:

Instruction (Variant index)Serialized KeySerialized Value
Initialize (0)not applicable for instructionnot applicable for instruction
Mint (1)"foo""bar"
Transfer (2)"foo"not applicable for instruction
Burn (2)"foo"not applicable for instruction

In the following example we assume the program owned account has been initialized

// Include borsh functionality

import { serialize, deserialize, deserializeUnchecked } from "borsh";
import { Buffer } from "buffer";

// Get Solana
import {
  Keypair,
  Connection,
  PublicKey,
  Transaction,
  TransactionInstruction,
  sendAndConfirmTransaction,
} from "@solana/web3.js";

// Flexible class that takes properties and imbues them
// to the object instance
class Assignable {
  constructor(properties) {
    Object.keys(properties).map((key) => {
      return (this[key] = properties[key]);
    });
  }
}

// Our instruction payload vocabulary
class Payload extends Assignable {}

// Borsh needs a schema describing the payload
const payloadSchema = new Map([
  [
    Payload,
    {
      kind: "struct",
      fields: [
        ["id", "u8"],
        ["key", "string"],
        ["value", "string"],
      ],
    },
  ],
]);

// Instruction variant indexes
enum InstructionVariant {
  InitializeAccount = 0,
  MintKeypair,
  TransferKeypair,
  BurnKeypair,
}

/**
 * Mint a key value pair to account
 * @param {Connection} connection - Solana RPC connection
 * @param {PublicKey} progId - Sample Program public key
 * @param {PublicKey} account - Target program owned account for Mint
 * @param {Keypair} wallet - Wallet for signing and payment
 * @param {string} mintKey - The key being minted key
 * @param {string} mintValue - The value being minted
 * @return {Promise<Keypair>} - Keypair
 */

export async function mintKV(
  connection: Connection,
  progId: PublicKey,
  account: PublicKey,
  wallet: Keypair,
  mintKey: string,
  mintValue: string
): Promise<string> {
  // Construct the payload
  const mint = new Payload({
    id: InstructionVariant.MintKeypair,
    key: mintKey, // 'ts key'
    value: mintValue, // 'ts first value'
  });

  // Serialize the payload
  const mintSerBuf = Buffer.from(serialize(payloadSchema, mint));
  // console.log(mintSerBuf)
  // => <Buffer 01 06 00 00 00 74 73 20 6b 65 79 0e 00 00 00 74 73 20 66 69 72 73 74 20 76 61 6c 75 65>
  // let mintPayloadCopy = deserialize(schema, Payload, mintSerBuf)
  // console.log(mintPayloadCopy)
  // => Payload { id: 1, key: 'ts key', value: 'ts first value' }

  // Create Solana Instruction
  const instruction = new TransactionInstruction({
    data: mintSerBuf,
    keys: [
      { pubkey: account, isSigner: false, isWritable: true },
      { pubkey: wallet.publicKey, isSigner: false, isWritable: false },
    ],
    programId: progId,
  });

  // Send Solana Transaction
  const transactionSignature = await sendAndConfirmTransaction(
    connection,
    new Transaction().add(instruction),
    [wallet],
    {
      commitment: "singleGossip",
      preflightCommitment: "singleGossip",
    }
  );
  console.log("Signature = ", transactionSignature);
  return transactionSignature;
}

from borsh_construct import String, CStruct, U8
from enum import IntEnum
from solana.transaction import Transaction
from solders.pubkey import Pubkey
from solders.keypair import Keypair
from solders.instruction import Instruction, AccountMeta
from solders.rpc.responses import SendTransactionResp
from solana.rpc.api import Client


# Instruction variants for target program
class InstructionVariant(IntEnum):
    INITIALIZE = 0
    MINT = 1
    TRANSFER = 2
    BURN = 3


# Schema for sending instructionVariants to on-chain sample program
payload_schema = CStruct("id" / U8, "key" / String, "value" / String)


def construct_payload(instruction_variant: InstructionVariant, key: str, value: str):
    """Generate a serialized instructionVariant"""
    return payload_schema.build({"id": instruction_variant, "key": key, "value": value})


def mint_kv(
    client: Client,
    program_pk: Pubkey,
    account_pk: Pubkey,
    wallet_kp: Keypair,
    mint_key: str,
    mint_value: str,
) -> SendTransactionResp:
    """Mint with a key/value pair to an account"""
    # Construct the program payload for Mint invariant
    payload_ser = construct_payload(InstructionVariant.MINT, mint_key, mint_value)

    # print(payload_ser)
    # => b'\x01\n\x00\x00\x00python key\x0c\x00\x00\x00python value'
    # mint_payload_copy = payload_schema.parse(payload_ser)
    # print(mint_payload_copy)
    # => Container:
    # =>     initialized = 1
    # =>     key = u'python key' (total 10)
    # =>     value = u'python value' (total 12)

    # Construct the transaction with instructionVariant
    txn = Transaction().add(
        Instruction(
            accounts=[AccountMeta(account_pk, False, True)], program_id=program_pk, data=payload_ser
        )
    )
    return client.send_transaction(txn, wallet_kp)
    # => {'jsonrpc': '2.0', 'result': '4ZdpWNdovdVaLextWSiqEBWp67k9rNTTUaX3qviHDXWY9c98bVtaRt5sasPhYzMVXHqhex78gzNKytcBnVH5CSTZ', 'id': 2}


/// Instruction payload gets serialized
#[derive(BorshSerialize)]
pub struct Payload<'a> {
    variant: u8,
    key: &'a str,
    value: &'a str,
}

/// Perform a mint transaction consisting of a key/value pair
/// See submit_transaction below
pub fn mint_transaction(
    rpc_client: &RpcClient,
    accounts: &[AccountMeta],
    wallet_signer: &dyn Signer,
    mint_key: &str,
    mint_value: &str,
    mint_instruction_id: u8,
    commitment_config: CommitmentConfig,
) -> Result<Signature, Box<dyn std::error::Error>> {
    // Setup the payload. `mint_instruction_id` is instruction variant index = 1
    let data = Payload<`_> {
        variant: mint_instruction_id,
        key: mint_key,
        value: mint_value,
    };
    let instruction = Instruction::new_with_borsh(PROG_KEY.pubkey(), &data, accounts.to_vec());
    submit_transaction(rpc_client, wallet_signer, instruction, commitment_config)
}

/// Submits the program instruction as per the
/// instruction definition
pub fn submit_transaction(
    rpc_client: &RpcClient,
    wallet_signer: &dyn Signer,
    instruction: Instruction,
    commitment_config: CommitmentConfig,
) -> Result<Signature, Box<dyn std::error::Error>> {
    let mut transaction =
        Transaction::new_unsigned(Message::new(&[instruction], Some(&wallet_signer.pubkey())));
    let (recent_blockhash, _fee_calculator) = rpc_client
        .get_recent_blockhash()
        .map_err(|err| format!("error: unable to get recent blockhash: {}", err))?;
    transaction
        .try_sign(&vec![wallet_signer], recent_blockhash)
        .map_err(|err| format!("error: failed to sign transaction: {}", err))?;
    let signature = rpc_client
        .send_and_confirm_transaction_with_spinner_and_commitment(&transaction, commitment_config)
        .map_err(|err| format!("error: send transaction: {}", err))?;
    Ok(signature)
}

How to deserialize instruction data on the program

Deserialize Instruction Data
//! instruction Contains the main ProgramInstruction enum

use {
    crate::error::SampleError, borsh::BorshDeserialize, solana_program::program_error::ProgramError,
};

#[derive(Debug, PartialEq)]
/// All custom program instructions
pub enum ProgramInstruction {
    InitializeAccount,
    MintToAccount { key: String, value: String },
    TransferBetweenAccounts { key: String },
    BurnFromAccount { key: String },
    MintToAccountWithFee { key: String, value: String },
    TransferBetweenAccountsWithFee { key: String },
    BurnFromAccountWithFee { key: String },
}

/// Generic Payload Deserialization
#[derive(BorshDeserialize, Debug)]
struct Payload {
    variant: u8,
    arg1: String,
    arg2: String,
}

impl ProgramInstruction {
    /// Unpack inbound buffer to associated Instruction
    /// The expected format for input is a Borsh serialized vector
    pub fn unpack(input: &[u8]) -> Result<Self, ProgramError> {
        let payload = Payload::try_from_slice(input).unwrap();
        match payload.variant {
            0 => Ok(ProgramInstruction::InitializeAccount),
            1 => Ok(Self::MintToAccount {
                key: payload.arg1,
                value: payload.arg2,
            }),
            2 => Ok(Self::TransferBetweenAccounts { key: payload.arg1 }),
            3 => Ok(Self::BurnFromAccount { key: payload.arg1 }),
            4 => Ok(Self::MintToAccountWithFee {
                key: payload.arg1,
                value: payload.arg2,
            }),
            5 => Ok(Self::TransferBetweenAccountsWithFee { key: payload.arg1 }),
            6 => Ok(Self::BurnFromAccountWithFee { key: payload.arg1 }),
            _ => Err(SampleError::DeserializationFailure.into()),
        }
    }
}

How to serialize account data on the program

Account Data Serialization

The program account data block (from the sample repo) is layed out as

Byte 0Bytes 1-4Remaining Byte up to 1019
Initialized flaglength of serialized BTreeMapBTreeMap (where key value pairs are stored)

Pack

A word about the Packopen in new window trait

The Pack trait makes it easier to hide the details of account data serialization/deserialization from your core Program instruction processing. So instead of putting all the serialize/deserialize log in the program processing code, it encapsulates the details behind (3) functions:

  1. unpack_unchecked - Allows you to deserialize an account without checking if it has been initialized. This is useful when you are actually processing the Initialization function (variant index 0)
  2. unpack - Calls your Pack implementation of unpack_from_slice and checks if account has been initialized.
  3. pack - Calls your Pack implementation of pack_into_slice

Here is the implementation of the Pack trait for our sample program. This is followed with the actual processing of the account data using borsh.

//! @brief account_state manages account data

use crate::error::SampleError;
use sol_template_shared::ACCOUNT_STATE_SPACE;
use solana_program::{
    entrypoint::ProgramResult,
    program_error::ProgramError,
    program_pack::{IsInitialized, Pack, Sealed},
};
use std::collections::BTreeMap;

/// Maintains global accumulator
#[derive(Debug, Default, PartialEq)]
pub struct ProgramAccountState {
    is_initialized: bool,
    btree_storage: BTreeMap<String, String>,
}

impl ProgramAccountState {
    /// Returns indicator if this account has been initialized
    pub fn set_initialized(&mut self) {
        self.is_initialized = true;
    }
    /// Adds a new key/value pair to the account
    pub fn add(&mut self, key: String, value: String) -> ProgramResult {
        match self.btree_storage.contains_key(&key) {
            true => Err(SampleError::KeyAlreadyExists.into()),
            false => {
                self.btree_storage.insert(key, value);
                Ok(())
            }
        }
    }
    /// Removes a key from account and returns the keys value
    pub fn remove(&mut self, key: &str) -> Result<String, SampleError> {
        match self.btree_storage.contains_key(key) {
            true => Ok(self.btree_storage.remove(key).unwrap()),
            false => Err(SampleError::KeyNotFoundInAccount),
        }
    }
}

impl Sealed for ProgramAccountState {}

// Pack expects the implementation to satisfy whether the
// account is initialzed.
impl IsInitialized for ProgramAccountState {
    fn is_initialized(&self) -> bool {
        self.is_initialized
    }
}

impl Pack for ProgramAccountState {
    const LEN: usize = ACCOUNT_STATE_SPACE;

    /// Store 'state' of account to its data area
    fn pack_into_slice(&self, dst: &mut [u8]) {
        sol_template_shared::pack_into_slice(self.is_initialized, &self.btree_storage, dst);
    }

    /// Retrieve 'state' of account from account data area
    fn unpack_from_slice(src: &[u8]) -> Result<Self, ProgramError> {
        match sol_template_shared::unpack_from_slice(src) {
            Ok((is_initialized, btree_map)) => Ok(ProgramAccountState {
                is_initialized,
                btree_storage: btree_map,
            }),
            Err(_) => Err(ProgramError::InvalidAccountData),
        }
    }
}

Serialization/Deserialization

To complete the underlying serialization and deserialization:

  1. sol_template_shared::pack_into_slice - Where the actual serialization occurs
  2. sol_template_shared::unpack_from_slice - Where the actual deserialization occurs

Note that in the following we have a u32 (4 bytes) partition in the data layout for BTREE_LENGTH preceding the BTREE_STORAGE. This is because borsh, during deserialization, checks that the length of the slice you are deserializing agrees with the amount of data it reads prior to actually recombobulation of the receiving object. The approach demonstrated below first reads the BTREE_LENGTH to get the size to slice out of the BTREE_STORAGE pointer.

use {
    arrayref::*,
    borsh::{BorshDeserialize, BorshSerialize},
    solana_program::program_memory::sol_memcpy,
    std::{collections::BTreeMap, error::Error},
};

/// Initialization flag size for account state
pub const INITIALIZED_BYTES: usize = 1;
/// Storage for the serialized size of the BTreeMap control
pub const BTREE_LENGTH: usize = 4;
/// Storage for the serialized BTreeMap container
pub const BTREE_STORAGE: usize = 1019;
/// Sum of all account state lengths
pub const ACCOUNT_STATE_SPACE: usize = INITIALIZED_BYTES + BTREE_LENGTH + BTREE_STORAGE;

/// Packs the initialized flag and data content into destination slice
#[allow(clippy::ptr_offset_with_cast)]
pub fn pack_into_slice(
    is_initialized: bool,
    btree_storage: &BTreeMap<String, String>,
    dst: &mut [u8],
) {
    let dst = array_mut_ref![dst, 0, ACCOUNT_STATE_SPACE];
    // Setup pointers to key areas of account state data
    let (is_initialized_dst, data_len_dst, data_dst) =
        mut_array_refs![dst, INITIALIZED_BYTES, BTREE_LENGTH, BTREE_STORAGE];
    // Set the initialized flag
    is_initialized_dst[0] = is_initialized as u8;
    // Store the core data length and serialized content
    let keyval_store_data = btree_storage.try_to_vec().unwrap();
    let data_len = keyval_store_data.len();
    if data_len < BTREE_STORAGE {
        data_len_dst[..].copy_from_slice(&(data_len as u32).to_le_bytes());
        sol_memcpy(data_dst, &keyval_store_data, data_len);
    } else {
        panic!();
    }
}

/// Unpacks the data from slice and return the initialized flag and data content
#[allow(clippy::ptr_offset_with_cast)]
pub fn unpack_from_slice(src: &[u8]) -> Result<(bool, BTreeMap<String, String>), Box<dyn Error>> {
    let src = array_ref![src, 0, ACCOUNT_STATE_SPACE];
    // Setup pointers to key areas of account state data
    let (is_initialized_src, data_len_src, data_src) =
        array_refs![src, INITIALIZED_BYTES, BTREE_LENGTH, BTREE_STORAGE];

    let is_initialized = match is_initialized_src {
        [0] => false,
        [1] => true,
        _ => {
            return Err(Box::<dyn Error>::from(format!(
                "unrecognized initialization flag \"{:?}\". in account",
                is_initialized_src
            )))
        }
    };
    // Get current size of content in data area
    let data_len = u32::from_le_bytes(*data_len_src) as usize;
    // If emptry, create a default
    if data_len == 0 {
        Ok((is_initialized, BTreeMap::<String, String>::new()))
    } else {
        let data_dser = BTreeMap::<String, String>::try_from_slice(&data_src[0..data_len]).unwrap();
        Ok((is_initialized, data_dser))
    }
}

Usage

The following pulls it all together and demonstrates how the program interacts with the ProgramAccountState which encapsulates the initialization flag as well as the underlying BTreeMap for our key/value pairs.

First when we want to initialize a brand new account:

/// Initialize a new program account, which is the first in AccountInfo array
fn initialize_account(accounts: &[AccountInfo]) -> ProgramResult {
    msg!("Initialize account");
    let account_info_iter = &mut accounts.iter();
    let program_account = next_account_info(account_info_iter)?;
    let mut account_data = program_account.data.borrow_mut();
    // Here we use unpack_unchecked as we have yet to initialize
    // Had we tried to use unpack it would fail because, well, chicken and egg
    let mut account_state = ProgramAccountState::unpack_unchecked(&account_data)?;
    // We double check that we haven't already initialized this accounts data
    // more than once. If we are good, we set the initialized flag
    if account_state.is_initialized() {
        return Err(SampleError::AlreadyInitializedState.into());
    } else {
        account_state.set_initialized();
    }
    // Finally, we store back to the accounts space
    ProgramAccountState::pack(account_state, &mut account_data).unwrap();
    Ok(())
}

Now we can operate on our other instructions as the following demonstrates minting a new key value pair that we demonstrated above when sending instructions from a client:

/// Mint a key/pair to the programs account, which is the first in accounts
fn mint_keypair_to_account(accounts: &[AccountInfo], key: String, value: String) -> ProgramResult {
    msg!("Mint to account");
    let account_info_iter = &mut accounts.iter();
    let program_account = next_account_info(account_info_iter)?;
    let mut account_data = program_account.data.borrow_mut();
    // Unpacking an uninitialized account state will fail
    let mut account_state = ProgramAccountState::unpack(&account_data)?;
    // Add the key value pair to the underlying BTreeMap
    account_state.add(key, value)?;
    // Finally, serialize back to the accounts data
    ProgramAccountState::pack(account_state, &mut account_data)?;
    Ok(())
}

How to deserialize account data on the client

Clients can call Solana to fetch program owned account, in which the serialized data block is a part of the return. Deserializing requires knowing the data block layout.

The layout of the account data was described Here

import { serialize, deserialize, deserializeUnchecked } from "borsh";
import { Buffer } from "buffer";
import {
  Keypair,
  AccountMeta,
  Connection,
  LAMPORTS_PER_SOL,
  PublicKey,
  SystemProgram,
  Transaction,
  TransactionInstruction,
  sendAndConfirmTransaction,
} from "@solana/web3.js";

// Flexible class that takes properties and imbues them
// to the object instance
class Assignable {
  constructor(properties) {
    Object.keys(properties).map((key) => {
      return (this[key] = properties[key]);
    });
  }
}

export class AccoundData extends Assignable {}

const dataSchema = new Map([
  [
    AccoundData,
    {
      kind: "struct",
      fields: [
        ["initialized", "u8"],
        ["tree_length", "u32"],
        ["map", { kind: "map", key: "string", value: "string" }],
      ],
    },
  ],
]);

/**
 * Fetch program account data
 * @param {Connection} connection - Solana RPC connection
 * @param {PublicKey} account - Public key for account whose data we want
 * @return {Promise<AccoundData>} - Keypair
 */
export async function getAccountData(
  connection: Connection,
  account: PublicKey
): Promise<AccoundData> {
  let nameAccount = await connection.getAccountInfo(account, "processed");
  return deserializeUnchecked(dataSchema, AccoundData, nameAccount.data);
}

from borsh_construct import CStruct, U8, U32, HashMap, String
from solana.rpc.commitment import Confirmed
from solders.pubkey import Pubkey
from solana.rpc.api import Client


# Schema to deserialize program's account data
account_schema = CStruct(
    "initialized" / U8,
    "map_length" / U32,
    "map" / HashMap(String, String)
)


def get_account_info(client: Client, account_pk: Pubkey):
    """Fetch account information from RPC, parse out the data and deserialize"""
    res = client.get_account_info(account_pk, Confirmed, encoding='base64')
    return account_schema.parse(res.value.data)

# Results in or similar
# => Container:
# =>     initialized = 1
# =>     map_length = 109
# =>     map = {'Happy': 'New Year!', 'newKey': 'A new value',
# =>            'python key': 'python value', 'ts key': 'ts first value'}

use {
    arrayref::*,
    borsh::{BorshDeserialize, BorshSerialize},
    std::{collections::BTreeMap, error::Error},
};

#[allow(clippy::ptr_offset_with_cast)]
pub fn unpack_from_slice(src: &[u8]) -> Result<(bool, BTreeMap<String, String>), Box<dyn Error>> {
    let src = array_ref![src, 0, ACCOUNT_STATE_SPACE];
    // Setup pointers to key areas of account state data
    let (is_initialized_src, data_len_src, data_src) =
        array_refs![src, INITIALIZED_BYTES, BTREE_LENGTH, BTREE_STORAGE];

    let is_initialized = match is_initialized_src {
        [0] => false,
        [1] => true,
        _ => {
            return Err(Box::<dyn Error>::from(format!(
                "unrecognized initialization flag \"{:?}\". in account",
                is_initialized_src
            )))
        }
    };
    // Get current size of content in data area
    let data_len = u32::from_le_bytes(*data_len_src) as usize;
    // If emptry, create a default
    if data_len == 0 {
        Ok((is_initialized, BTreeMap::<String, String>::new()))
    } else {
        let data_dser = BTreeMap::<String, String>::try_from_slice(&data_src[0..data_len]).unwrap();
        Ok((is_initialized, data_dser))
    }
}

Common Solana TS/JS Mappings

The Borsh Specification contains most mappings for primitive and compound data types.

The key to TS/JS and Python is creating a Borsh Schema with a proper definition so the serialize and deserialize can generate or walk the respective inputs.

Here we demonstrate serialization of primitives (numbers, strings) and compound types (fixed size array, Map) first in Typescript, then in Python and then equivalent deserialization on the Rust side:

#!/usr/bin/env node

import { serialize, deserialize, deserializeUnchecked } from "borsh";
import { Buffer } from "buffer";
import { expect } from "chai";
import { PublicKey, Struct } from "@solana/web3.js";

/**
 * Primitive extends the Struct type from Solana Library
 * for convenience of dynamic property setting
 * @extends {Struct} Solana JS Struct class
 */

class Primitive extends Struct {
  constructor(properties) {
    super(properties);
  }
}

/**
 * Entry point for script *
 */
async function entry() {
  // Emulate BTreeMap
  let map = new Map();
  map.set("cookbook", "recipe");
  map.set("recipe", "ingredient");

  // Setup a Primitive for all basic and a few
  // compound types
  const value = new Primitive({
    U8: 255,
    U16: 65535,
    U32: 4294967295,
    FIXED_STRING_ARRAY: ["hello", "world"],
    FIXED_U8_ARRAY: [1, 2, 3, 4, 5],
    MAP_STRING_STRING: map,
  });
  // Define our schema
  const schema = new Map([
    [
      Primitive,
      {
        kind: "struct",
        fields: [
          ["U8", "u8"],
          ["U16", "u16"],
          ["U32", "u32"],
          ["FIXED_STRING_ARRAY", ["string", 2]],
          ["FIXED_U8_ARRAY", ["u8", 5]],
          [
            "MAP_STRING_STRING",
            { kind: "map", key: "string", value: "string" },
          ],
        ],
      },
    ],
  ]);
  console.log("Value = ", value);
  // Serialize then deserialize
  const dser = Buffer.from(serialize(schema, value));
  console.log(dser);
  const newValue = deserialize(schema, Primitive, dser);
  // Viola!
  console.log("New value = ", newValue);
  console.log("Fixed string array = ", newValue["FIXED_STRING_ARRAY"]);
  console.log("Fixed u8 array = ", newValue["FIXED_U8_ARRAY"]);
  console.log("Map = ", newValue["MAP_STRING_STRING"]);
}

entry();

from borsh_construct import U8, U16, U32, String, HashMap

# Schema to deserialize various types
primitive_schema = CStruct(
        "U8" / U8,
        "U16" / U16,
        "U32" / U32,
        "FIXED_STRING_ARRAY" / String[2],
        "FIXED_U8_ARRAY" / U8[5],
        "MAP_STRING_STRING" / HashMap(String, String)
)


def common():
    mapping = {"cookbook": "recipe", "recipe": "ingredient"}

    # Serialize
    dser = primitive_schema.build({
        'U8': 255,
        'U16': 65535,
        'U32': 4294967295,
        "FIXED_STRING_ARRAY": ['hello', 'world'],
        "FIXED_U8_ARRAY": [1, 2, 3, 4, 5],
        "MAP_STRING_STRING": mapping})
    print(dser)
    # => b'\xff\xff\xff\xff\xff\xff\xff\x05\x00\x00\x00hello\x05\x00\x00\x00world\x01\x02\x03\x04\x05\x02\x00\x00\x00\x08\x00\x00\x00cookbook\x06\x00\x00\x00recipe\x06\x00\x00\x00recipe\n\x00\x00\x00ingredient'
    # Deserialize
    new_value = primitive_schema.parse(dser)
    # Viola
    print(new_value)
    # => Container:
    # =>    U8 = 255
    # =>    U16 = 65535
    # =>    U32 = 4294967295
    # =>    FIXED_STRING_ARRAY = ListContainer:
    # =>        hello
    # =>        world
    # =>    FIXED_U8_ARRAY = ListContainer:
    # =>        1
    # =>        2
    # =>        3
    # =>        4
    # =>        5
    # =>    MAP_STRING_STRING = {'cookbook': 'recipe', 'recipe': 'ingredient'}

fn main() {}

#[cfg(test)]
mod tests {
    use borsh::{BorshDeserialize, BorshSerialize};
    use std::collections::BTreeMap;

    #[test]
    fn primitives() {
        let prim = [
            255u8, 255, 255, 255, 255, 255, 255, 5, 0, 0, 0, 104, 101, 108, 108, 111, 5, 0, 0, 0,
            119, 111, 114, 108, 100, 1, 2, 3, 4, 5, 2, 0, 0, 0, 8, 0, 0, 0, 99, 111, 111, 107, 98,
            111, 111, 107, 6, 0, 0, 0, 114, 101, 99, 105, 112, 101, 6, 0, 0, 0, 114, 101, 99, 105,
            112, 101, 10, 0, 0, 0, 105, 110, 103, 114, 101, 100, 105, 101, 110, 116,
        ];
        #[derive(BorshDeserialize, BorshSerialize, Debug)]
        struct Primitive(
            u8,
            u16,
            u32,
            String,
            String,
            [u8; 5],
            BTreeMap<String, String>,
        );
        let x = Primitive::try_from_slice(&prim).unwrap();
        println!("{:?}", x);
    }
}

Advanced Constructs

We've shown how to create simple Payloads in previous examples. Sometimes Solana throws a fastball with certain types. This section will demonstrate proper mapping between TS/JS and Rust to handle those

COption

#!/usr/bin/env node

import { serialize, deserialize, deserializeUnchecked } from "borsh";
import { Buffer } from "buffer";
import { PublicKey, Struct } from "@solana/web3.js";

/**
 * COption is meant to mirror the
 * `solana_program::options::COption`
 *
 * This type stores a u32 flag (0 | 1) indicating
 * the presence or not of a underlying PublicKey
 *
 * Similar to a Rust Option
 * @extends {Struct} Solana JS Struct class
 * @implements {encode}
 */
class COption extends Struct {
  constructor(properties) {
    super(properties);
  }

  /**
   * Creates a COption from a PublicKey
   * @param {PublicKey?} akey
   * @returns {COption} COption
   */
  static fromPublicKey(akey?: PublicKey): COption {
    if (akey == undefined) {
      return new COption({
        noneOrSome: 0,
        pubKeyBuffer: new Uint8Array(32),
      });
    } else {
      return new COption({
        noneOrSome: 1,
        pubKeyBuffer: akey.toBytes(),
      });
    }
  }
  /**
   * @returns {Buffer} Serialized COption (this)
   */
  encode(): Buffer {
    return Buffer.from(serialize(COPTIONSCHEMA, this));
  }
  /**
   * Safe deserializes a borsh serialized buffer to a COption
   * @param {Buffer} data - Buffer containing borsh serialized data
   * @returns {COption} COption object
   */
  static decode(data): COption {
    return deserialize(COPTIONSCHEMA, this, data);
  }

  /**
   * Unsafe deserializes a borsh serialized buffer to a COption
   * @param {Buffer} data - Buffer containing borsh serialized data
   * @returns {COption} COption object
   */
  static decodeUnchecked(data): COption {
    return deserializeUnchecked(COPTIONSCHEMA, this, data);
  }
}

/**
 * Defines the layout of the COption object
 * for serializing/deserializing
 * @type {Map}
 */
const COPTIONSCHEMA = new Map([
  [
    COption,
    {
      kind: "struct",
      fields: [
        ["noneOrSome", "u32"],
        ["pubKeyBuffer", [32]],
      ],
    },
  ],
]);

/**
 * Entry point for script *
 */
async function entry(indata?: PublicKey) {
  // If we get a PublicKey
  if (indata) {
    // Construct COption instance
    const coption = COption.fromPublicKey(indata);
    console.log("Testing COption with " + indata.toBase58());
    // Serialize it
    let copt_ser = coption.encode();
    console.log("copt_ser ", copt_ser);
    // Deserialize it
    const tdone = COption.decode(copt_ser);
    console.log(tdone);
    // Validate contains PublicKey
    if (tdone["noneOrSome"] == 1) {
      console.log("pubkey: " + new PublicKey(tdone["pubKeyBuffer"]).toBase58());
    }
    /*
            Output:
            Testing COption with A94wMjV54C8f8wn7zL8TxNCdNiGoq7XSN7vWGrtd4vwU
            copt_ser  Buffer(36) [1, 0, 0, 0, 135, 202, 71, 214, 68, 105, 98, 176, 211, 130, 105, 2, 55, 187, 86, 186, 109, 176, 80, 208, 77, 100, 221, 101, 20, 203, 149, 166, 96, 171, 119, 35, buffer: ArrayBuffer(8192), byteLength: 36, byteOffset: 1064, length: 36]
            COption {noneOrSome: 1, pubKeyBuffer: Uint8Array(32)}
            pubkey: A94wMjV54C8f8wn7zL8TxNCdNiGoq7XSN7vWGrtd4vwU
        */
  } else {
    console.log("Testing COption with null");
    // Construct COption instance
    const coption = COption.fromPublicKey();
    // Serialize it
    const copt_ser = coption.encode();
    console.log(copt_ser);
    // Deserialize it
    const tdone1 = COption.decode(copt_ser);
    console.log(tdone1);
    // Validate does NOT contains PublicKey
    if (tdone1["noneOrSome"] == 1) {
      throw Error("Expected no public key");
    } else console.log("pubkey: null");
    /*
            Output:
            Testing COption with null
            Buffer(36)[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, buffer: ArrayBuffer(8192), byteLength: 36, byteOffset: 2272, length: 36]
            COption { noneOrSome: 0, pubKeyBuffer: Uint8Array(32) }
            pubkey: null
        */
  }
}

// Test with PublicKey
entry(new PublicKey("A94wMjV54C8f8wn7zL8TxNCdNiGoq7XSN7vWGrtd4vwU"));
console.log("");
// Test without PublicKey
entry();

fn main() {}

#[cfg(test)]
mod tests {
    use arrayref::{array_ref, array_refs};
    use solana_program::{program_option::COption, pubkey::Pubkey};

    /// Emulate how COption is 'unpacked'
    fn deser_option(data: &[u8]) -> COption<Pubkey> {
        // Map the data block
        let ain = array_ref![data, 0, 36];
        let (base, key) = array_refs![ain, 4, 32];
        // Get the SOME or NONE u32
        let nos = u32::from_le_bytes(*base);
        // Construct the COption accordingly
        let opt: COption<Pubkey> = if nos == 0 {
            COption::None
        } else {
            COption::Some(Pubkey::new_from_array(*key))
        };
        opt
    }
    #[test]
    fn btest() {
        // From Typescript with borsh'ing
        let copt = [
            1u8, 0, 0, 0, 135, 202, 71, 214, 68, 105, 98, 176, 211, 130, 105, 2, 55, 187, 86, 186,
            109, 176, 80, 208, 77, 100, 221, 101, 20, 203, 149, 166, 96, 171, 119, 35,
        ];
        // Emulate COption deserialization
        let coption = deser_option(&copt);
        if coption.is_some() {
            println!("{:?}", coption.expect("Uh-oh"));
        }
        // As a Borsh Struct
        #[derive(BorshDeserialize, BorshSerialize, Debug)]
        struct TOption(u32, [u8; 32]);
        let toption = TOption::try_from_slice(&copt).unwrap();
        let pkey = Pubkey::new_from_array(toption.1);
        println!("Some = {:?} Pubkey = {:?}", toption.0, pkey);
    }
}

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Contributors: Frank V. Castellucci, Jacob Creech, Jacob Creech, Kevin Heavey, abacus-x, akangaziz