token-2022: Add transfer fee types and instructions

token/program-2022/src/extension.rs

@@ -0,0 +1,97 @@
+//! Extensions available to token mints and accounts
+
+use solana_program::{clock::Epoch, program_option::COption, pubkey::Pubkey};
+
+/// Different kinds of accounts. Note that `Mint`, `Account`, and `Multisig` types
+/// are determined exclusively by the size of the account, and are not included in
+/// the account data. `AccountType` is only included if extensions have been
+/// initialized.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub enum AccountType {
+    /// Marker for 0 data
+    Uninitialized,
+    /// Mint account with additional extensions
+    Mint,
+    /// Token holding account with additional extensions
+    Account,
+}
+
+impl Default for AccountType {
+    fn default() -> Self {
+        Self::Uninitialized
+    }
+}
+
+/// Extensions that can be applied to mints or accounts.  Mint extensions must only be
+/// applied to mint accounts, and account extensions must only be applied to token holding
+/// accounts.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub enum Extension {
+    /// Used as padding if the account size would otherwise be 355, same as a multisig
+    Uninitialized,
+    /// Includes a transfer fee and accompanying authorities to withdraw and set the fee
+    MintTransferFee,
+    /// Includes withheld transfer fees
+    AccountTransferFee,
+    /// Includes an optional mint close authority
+    MintCloseAuthority,
+}
+
+/// Type-Length-Value Entry, used to encapsulate all extensions contained within an account
+#[repr(C)]
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct TlvEntry<V> {
+    /// Extension type encoded in the rest of the entry
+    pub extension: Extension,
+    /// Length of the entry, in bytes
+    pub length: u32,
+    /// Deserialized value
+    pub value: V,
+}
+
+/// Close authority extension data for mints.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, PartialEq)]
+pub struct MintCloseAuthority {
+    /// Optional authority to close the mint
+    pub close_authority: COption<Pubkey>,
+}
+
+/// Transfer fee information
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, PartialEq)]
+pub struct TransferFee {
+    /// First epoch where the transfer fee takes effect
+    pub epoch: Epoch,
+    /// Amount of transfer collected as fees, expressed as basis points of the
+    /// transfer amount, ie. increments of 0.01%
+    pub transfer_fee_basis_points: u16,
+    /// Maximum fee assessed on transfers, expressed as an amount of tokens
+    pub maximum_fee: u64,
+}
+
+/// Transfer fee extension data for mints.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, PartialEq)]
+pub struct MintTransferFee {
+    /// Optional authority to set the fee
+    pub transfer_fee_config_authority: COption<Pubkey>,
+    /// Withdraw from mint instructions must be signed by this key
+    pub withheld_withdraw_authority: COption<Pubkey>,
+    /// Withheld transfer fee tokens that have been moved to the mint for withdrawal
+    pub withheld_amount: u64,
+    /// Older transfer fee, used if the current epoch < new_transfer_fee.epoch
+    pub older_transfer_fee: TransferFee,
+    /// Newer transfer fee, used if the current epoch >= new_transfer_fee.epoch
+    pub newer_transfer_fee: TransferFee,
+}
+
+/// Transfer fee extension data for accounts.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, PartialEq)]
+pub struct AccountTransferFee {
+    /// Amount withheld during transfers, to be harvested to the mint
+    pub withheld_amount: u64,
+}