Add 4 transfer hook examples

tokens/token-2022/transfer-hook/anchor/TransferHookCounter/.gitignore

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+
+.anchor
+.DS_Store
+target
+**/*.rs.bk
+node_modules
+test-ledger
+.yarn

tokens/token-2022/transfer-hook/anchor/TransferHookCounter/.prettierignore

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+
+.anchor
+.DS_Store
+target
+node_modules
+dist
+build
+test-ledger

tokens/token-2022/transfer-hook/anchor/TransferHookCounter/Anchor.toml

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+[toolchain]
+
+[features]
+seeds = false
+skip-lint = false
+
+[programs.localnet]
+transfer_hook = "DrWbQtYJGtsoRwzKqAbHKHKsCJJfpysudF39GBVFSxub"
+
+[registry]
+url = "https://api.apr.dev"
+
+[provider]
+cluster = "Localnet"
+wallet = "~/.config/solana/id.json"
+
+[scripts]
+test = "yarn run ts-mocha -p ./tsconfig.json -t 1000000 tests/**/*.ts"

tokens/token-2022/transfer-hook/anchor/TransferHookCounter/Cargo.toml

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+[workspace]
+members = [
+    "programs/*"
+]
+
+[profile.release]
+overflow-checks = true
+lto = "fat"
+codegen-units = 1
+[profile.release.build-override]
+opt-level = 3
+incremental = false
+codegen-units = 1

tokens/token-2022/transfer-hook/anchor/TransferHookCounter/migrations/deploy.ts

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+// Migrations are an early feature. Currently, they're nothing more than this
+// single deploy script that's invoked from the CLI, injecting a provider
+// configured from the workspace's Anchor.toml.
+
+const anchor = require("@coral-xyz/anchor");
+
+module.exports = async function (provider) {
+  // Configure client to use the provider.
+  anchor.setProvider(provider);
+
+  // Add your deploy script here.
+};

tokens/token-2022/transfer-hook/anchor/TransferHookCounter/package.json

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+{
+    "scripts": {
+        "lint:fix": "prettier */*.js \"*/**/*{.js,.ts}\" -w",
+        "lint": "prettier */*.js \"*/**/*{.js,.ts}\" --check"
+    },
+    "dependencies": {
+        "@coral-xyz/anchor": "^0.29.0",
+        "@solana/spl-token": "^0.4.0",
+        "@solana/web3.js": "^1.89.1"
+    },
+    "devDependencies": {
+        "@types/bn.js": "^5.1.0",
+        "@types/chai": "^4.3.0",
+        "@types/mocha": "^9.0.0",
+        "chai": "^4.3.4",
+        "mocha": "^9.0.3",
+        "prettier": "^2.6.2",
+        "ts-mocha": "^10.0.0",
+        "typescript": "^4.3.5"
+    }
+}

tokens/token-2022/transfer-hook/anchor/TransferHookCounter/programs/transfer-hook/Cargo.toml

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+[package]
+name = "transfer-hook"
+version = "0.1.0"
+description = "Created with Anchor"
+edition = "2021"
+
+[lib]
+crate-type = ["cdylib", "lib"]
+name = "transfer_hook"
+
+[features]
+no-entrypoint = []
+no-idl = []
+no-log-ix-name = []
+cpi = ["no-entrypoint"]
+default = []
+
+[dependencies]
+anchor-lang = {version = "0.29.0", features = ["init-if-needed"]}
+anchor-spl = "0.29.0"
+solana-program = "=1.17.17"
+
+spl-transfer-hook-interface = "0.5.0"
+spl-tlv-account-resolution = "0.5.0"

tokens/token-2022/transfer-hook/anchor/TransferHookCounter/programs/transfer-hook/Xargo.toml

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+[target.bpfel-unknown-unknown.dependencies.std]
+features = []

tokens/token-2022/transfer-hook/anchor/TransferHookCounter/programs/transfer-hook/src/lib.rs

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+use anchor_lang::{
+    prelude::*,
+    system_program::{create_account, CreateAccount},
+};
+use anchor_spl::{
+    associated_token::AssociatedToken,
+    token_interface::{Mint, TokenAccount, TokenInterface},
+};
+use spl_tlv_account_resolution::{
+    account::ExtraAccountMeta, seeds::Seed, state::ExtraAccountMetaList,
+};
+use spl_transfer_hook_interface::instruction::{ExecuteInstruction, TransferHookInstruction};
+
+declare_id!("DrWbQtYJGtsoRwzKqAbHKHKsCJJfpysudF39GBVFSxub");
+
+#[error_code]
+pub enum MyError {
+    #[msg("The amount is too big")]
+    AmountTooBig,
+}
+
+#[program]
+pub mod transfer_hook {
+    use super::*;
+
+    pub fn initialize_extra_account_meta_list(
+        ctx: Context<InitializeExtraAccountMetaList>,
+    ) -> Result<()> {
+
+        let account_metas = vec![
+            ExtraAccountMeta::new_with_seeds(
+                &[Seed::Literal {
+                    bytes: "counter".as_bytes().to_vec(),
+                }],
+                false, // is_signer
+                true,  // is_writable
+            )?,
+        ];
+
+        // calculate account size
+        let account_size = ExtraAccountMetaList::size_of(account_metas.len())? as u64;
+        // calculate minimum required lamports
+        let lamports = Rent::get()?.minimum_balance(account_size as usize);
+
+        let mint = ctx.accounts.mint.key();
+        let signer_seeds: &[&[&[u8]]] = &[&[
+            b"extra-account-metas",
+            &mint.as_ref(),
+            &[ctx.bumps.extra_account_meta_list],
+        ]];
+
+        // create ExtraAccountMetaList account
+        create_account(
+            CpiContext::new(
+                ctx.accounts.system_program.to_account_info(),
+                CreateAccount {
+                    from: ctx.accounts.payer.to_account_info(),
+                    to: ctx.accounts.extra_account_meta_list.to_account_info(),
+                },
+            )
+            .with_signer(signer_seeds),
+            lamports,
+            account_size,
+            ctx.program_id,
+        )?;
+
+        // initialize ExtraAccountMetaList account with extra accounts
+        ExtraAccountMetaList::init::<ExecuteInstruction>(
+            &mut ctx.accounts.extra_account_meta_list.try_borrow_mut_data()?,
+            &account_metas,
+        )?;
+
+        Ok(())
+    }
+
+    pub fn transfer_hook(ctx: Context<TransferHook>, amount: u64) -> Result<()> {
+
+        if amount > 50 {
+            msg!("The amount is too big {0}", amount);
+            //return err!(MyError::AmountTooBig);
+        }
+
+        ctx.accounts.counter_account.counter.checked_add(1).unwrap();
+
+        msg!("This token has been transferred {0} times", ctx.accounts.counter_account.counter);
+
+        Ok(())
+    }
+
+    // fallback instruction handler as workaround to anchor instruction discriminator check
+    pub fn fallback<'info>(
+        program_id: &Pubkey,
+        accounts: &'info [AccountInfo<'info>],
+        data: &[u8],
+    ) -> Result<()> {
+        let instruction = TransferHookInstruction::unpack(data)?;
+
+        // match instruction discriminator to transfer hook interface execute instruction  
+        // token2022 program CPIs this instruction on token transfer
+        match instruction {
+            TransferHookInstruction::Execute { amount } => {
+                let amount_bytes = amount.to_le_bytes();
+
+                // invoke custom transfer hook instruction on our program
+                __private::__global::transfer_hook(program_id, accounts, &amount_bytes)
+            }
+            _ => return Err(ProgramError::InvalidInstructionData.into()),
+        }
+    }
+}
+
+#[derive(Accounts)]
+pub struct InitializeExtraAccountMetaList<'info> {
+    #[account(mut)]
+    payer: Signer<'info>,
+
+    /// CHECK: ExtraAccountMetaList Account, must use these seeds
+    #[account(
+        mut,
+        seeds = [b"extra-account-metas", mint.key().as_ref()], 
+        bump
+    )]
+    pub extra_account_meta_list: AccountInfo<'info>,
+    pub mint: InterfaceAccount<'info, Mint>,
+    #[account(
+        init_if_needed,
+        seeds = [b"counter"], 
+        bump,
+        payer = payer,
+        space = 16
+    )]
+    pub counter_account: Account<'info, CounterAccount>,
+    pub token_program: Interface<'info, TokenInterface>,
+    pub associated_token_program: Program<'info, AssociatedToken>,
+    pub system_program: Program<'info, System>,
+}
+
+// Order of accounts matters for this struct.
+// The first 4 accounts are the accounts required for token transfer (source, mint, destination, owner)
+// Remaining accounts are the extra accounts required from the ExtraAccountMetaList account
+// These accounts are provided via CPI to this program from the token2022 program
+#[derive(Accounts)]
+pub struct TransferHook<'info> {
+    #[account(
+        token::mint = mint, 
+        token::authority = owner,
+    )]
+    pub source_token: InterfaceAccount<'info, TokenAccount>,
+    pub mint: InterfaceAccount<'info, Mint>,
+    #[account(
+        token::mint = mint,
+    )]
+    pub destination_token: InterfaceAccount<'info, TokenAccount>,
+    /// CHECK: source token account owner, can be SystemAccount or PDA owned by another program
+    pub owner: UncheckedAccount<'info>,
+    /// CHECK: ExtraAccountMetaList Account,
+    #[account(
+        seeds = [b"extra-account-metas", mint.key().as_ref()], 
+        bump
+    )]
+    pub extra_account_meta_list: UncheckedAccount<'info>,
+    #[account(
+        seeds = [b"counter"],
+        bump
+    )]
+    pub counter_account: Account<'info, CounterAccount>,
+}
+
+#[account]
+pub struct CounterAccount {
+    counter: u64,
+}