Program Derived Address

  static findProgramAddressSync(
    seeds: Array<Buffer | Uint8Array>,
    programId: PublicKey,
  ): [PublicKey, number] {
    let nonce = 255;
    let address;
    while (nonce != 0) {
      try {
        const seedsWithNonce = seeds.concat(Buffer.from([nonce]));
        address = this.createProgramAddressSync(seedsWithNonce, programId);
      } catch (err) {
        if (err instanceof TypeError) {
          throw err;
        }
        nonce--;
        continue;
      }
      return [address, nonce];
    }
    throw new Error(`Unable to find a viable program address nonce`);
  }

    pub fn find_program_address(seeds: &[&[u8]], program_id: &Pubkey) -> (Pubkey, u8) {
        Self::try_find_program_address(seeds, program_id)
            .unwrap_or_else(|| panic!("Unable to find a viable program address bump seed"))
    }

    pub fn try_find_program_address(seeds: &[&[u8]], program_id: &Pubkey) -> Option<(Pubkey, u8)> {
        // Perform the calculation inline, calling this from within a program is
        // not supported
        #[cfg(not(target_os = "solana"))]
        {
            let mut bump_seed = [std::u8::MAX];
            for _ in 0..std::u8::MAX {
                {
                    let mut seeds_with_bump = seeds.to_vec();
                    seeds_with_bump.push(&bump_seed);
                    match Self::create_program_address(&seeds_with_bump, program_id) {
                        Ok(address) => return Some((address, bump_seed[0])),
                        Err(PubkeyError::InvalidSeeds) => (),
                        _ => break,
                    }
                }
                bump_seed[0] -= 1;
            }
            None
        }
        // Call via a system call to perform the calculation
        #[cfg(target_os = "solana")]
        {
            let mut bytes = [0; 32];
            let mut bump_seed = std::u8::MAX;
            let result = unsafe {
                crate::syscalls::sol_try_find_program_address(
                    seeds as *const _ as *const u8,
                    seeds.len() as u64,
                    program_id as *const _ as *const u8,
                    &mut bytes as *mut _ as *mut u8,
                    &mut bump_seed as *mut _ as *mut u8,
                )
            };
            match result {
                crate::entrypoint::SUCCESS => Some((Pubkey::from(bytes), bump_seed)),
                _ => None,
            }
        }
    }

  static createProgramAddressSync(
    seeds: Array<Buffer | Uint8Array>,
    programId: PublicKey,
  ): PublicKey {
    let buffer = Buffer.alloc(0);
    seeds.forEach(function (seed) {
      if (seed.length > MAX_SEED_LENGTH) {
        throw new TypeError(`Max seed length exceeded`);
      }
      buffer = Buffer.concat([buffer, toBuffer(seed)]);
    });
    buffer = Buffer.concat([
      buffer,
      programId.toBuffer(),
      Buffer.from('ProgramDerivedAddress'),
    ]);
    const publicKeyBytes = sha256(buffer);
    if (isOnCurve(publicKeyBytes)) {
      throw new Error(`Invalid seeds, address must fall off the curve`);
    }
    return new PublicKey(publicKeyBytes);
  }

    pub fn create_program_address(
        seeds: &[&[u8]],
        program_id: &Pubkey,
    ) -> Result<Pubkey, PubkeyError> {
        if seeds.len() > MAX_SEEDS {
            return Err(PubkeyError::MaxSeedLengthExceeded);
        }
        for seed in seeds.iter() {
            if seed.len() > MAX_SEED_LEN {
                return Err(PubkeyError::MaxSeedLengthExceeded);
            }
        }

        // Perform the calculation inline, calling this from within a program is
        // not supported
        #[cfg(not(target_os = "solana"))]
        {
            let mut hasher = crate::hash::Hasher::default();
            for seed in seeds.iter() {
                hasher.hash(seed);
            }
            hasher.hashv(&[program_id.as_ref(), PDA_MARKER]);
            let hash = hasher.result();

            if bytes_are_curve_point(hash) {
                return Err(PubkeyError::InvalidSeeds);
            }

            Ok(Pubkey::from(hash.to_bytes()))
        }
        // Call via a system call to perform the calculation
        #[cfg(target_os = "solana")]
        {
            let mut bytes = [0; 32];
            let result = unsafe {
                crate::syscalls::sol_create_program_address(
                    seeds as *const _ as *const u8,
                    seeds.len() as u64,
                    program_id as *const _ as *const u8,
                    &mut bytes as *mut _ as *mut u8,
                )
            };
            match result {
                crate::entrypoint::SUCCESS => Ok(Pubkey::from(bytes)),
                _ => Err(result.into()),
            }
        }
    }

use anchor_lang::prelude::*;

// Specify the program address
declare_id!("C93fyDjEmyAfr9nwDeWMVCeWVVx8fjySxnshSA9VY4KG");

// Instructions defined in program module
#[program]
pub mod counter {
    use super::*;

    // Instruction to initialize a new counter account
    pub fn initialize(ctx: Context<Initialize>) -> Result<()> {
        // Reference to the counter account from the Initialize struct
        let counter = &ctx.accounts.counter;
        msg!("Counter account created! Current count: {}", counter.count);
        Ok(())
    }

    // Instruction to increment a counter account
    pub fn increment(ctx: Context<Increment>) -> Result<()> {
        // Mutable reference to the counter account from the Increment struct
        let counter = &mut ctx.accounts.counter;
        msg!("Previous counter: {}", counter.count);

        // Increment the count value stored on the counter account by 1
        counter.count = counter.count + 1;
        msg!("Counter incremented! Current count: {}", counter.count);
        Ok(())
    }
}

// Accounts required by the initialize instruction
#[derive(Accounts)]
pub struct Initialize<'info> {
    // The account paying to create the counter account
    #[account(mut)]
    pub user: Signer<'info>, // specify account must be signer on the transaction

    // The counter account being created and initialized in the instruction
    #[account(
        init,         // specifies we are creating this account
        payer = user, // specifies account paying for the creation of the account
        space = 8 + 8 // space allocated to the new account (8 byte discriminator + 8 byte for u64)
    )]
    pub counter: Account<'info, Counter>, // specify account is 'Counter' type
    pub system_program: Program<'info, System>, // specify account must be System Program
}

// Account required by the increment instruction
#[derive(Accounts)]
pub struct Increment<'info> {
    #[account(mut)] // specify account is mutable because we are updating its data
    pub counter: Account<'info, Counter>, // specify account is 'Counter' type
}

// Define structure of `Counter` account
#[account]
pub struct Counter {
    pub count: u64, // define count value type as u64
}

import * as anchor from "@coral-xyz/anchor";
import { Program } from "@coral-xyz/anchor";
import { Counter } from "../target/types/counter";
import { Keypair } from "@solana/web3.js";

describe("counter", () => {
  // Configure the client to use the local cluster.
  const provider = anchor.AnchorProvider.env();
  anchor.setProvider(provider);

  const program = anchor.workspace.Counter as Program<Counter>;

  // Generate a new keypair to use as the address the counter account
  const counterAccount = new Keypair();

  it("Is initialized!", async () => {
    // Invoke the initialize instruction
    const transactionSignature = await program.methods
      .initialize()
      .accounts({
        counter: counterAccount.publicKey,
      })
      .signers([counterAccount]) // include counter keypair as additional signer
      .rpc({ skipPreflight: true });

    // Fetch the counter account data
    const accountData = await program.account.counter.fetch(
      counterAccount.publicKey
    );

    console.log(`Transaction Signature: ${transactionSignature}`);
    console.log(`Count: ${accountData.count}`);
  });

  it("Increment", async () => {
    // Invoke the increment instruction
    const transactionSignature = await program.methods
      .increment()
      .accounts({
        counter: counterAccount.publicKey,
      })
      .rpc();

    // Fetch the counter account data
    const accountData = await program.account.counter.fetch(
      counterAccount.publicKey
    );

    console.log(`Transaction Signature: ${transactionSignature}`);
    console.log(`Count: ${accountData.count}`);
  });
});