2022-01-06 13:30:44 -08:00
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//! Type facilitating on demand zero copy deserialization.
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use crate::error::ErrorCode;
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use crate::{
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Accounts, AccountsClose, AccountsExit, Owner, Result, ToAccountInfo, ToAccountInfos,
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ToAccountMetas, ZeroCopy,
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};
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use arrayref::array_ref;
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use solana_program::account_info::AccountInfo;
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use solana_program::instruction::AccountMeta;
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use solana_program::pubkey::Pubkey;
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use std::cell::{Ref, RefMut};
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use std::collections::BTreeMap;
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use std::fmt;
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use std::io::Write;
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use std::marker::PhantomData;
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use std::mem;
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use std::ops::DerefMut;
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2022-01-06 13:30:44 -08:00
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/// Type facilitating on demand zero copy deserialization.
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///
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/// Note that using accounts in this way is distinctly different from using,
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/// for example, the [`Account`](./struct.Account.html). Namely,
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/// one must call
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/// - `load_init` after initializing an account (this will ignore the missing
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/// account discriminator that gets added only after the user's instruction code)
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/// - `load` when the account is not mutable
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/// - `load_mut` when the account is mutable
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///
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/// For more details on zero-copy-deserialization, see the
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/// [`account`](./attr.account.html) attribute.
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/// <p style=";padding:0.75em;border: 1px solid #ee6868">
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/// <strong>⚠️ </strong> When using this type it's important to be mindful
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/// of any calls to the <code>load</code> functions so as not to
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/// induce a <code>RefCell</code> panic, especially when sharing accounts across CPI
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/// boundaries. When in doubt, one should make sure all refs resulting from
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/// a call to a <code>load</code> function are dropped before CPI.
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/// This can be done explicitly by calling <code>drop(my_var)</code> or implicitly
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/// by wrapping the code using the <code>Ref</code> in braces <code>{..}</code> or
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/// moving it into its own function.
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/// </p>
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///
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/// # Example
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/// ```ignore
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/// use anchor_lang::prelude::*;
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///
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/// declare_id!("Fg6PaFpoGXkYsidMpWTK6W2BeZ7FEfcYkg476zPFsLnS");
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///
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/// #[program]
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/// pub mod bar {
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/// use super::*;
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///
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/// pub fn create_bar(ctx: Context<CreateBar>, data: u64) -> Result<()> {
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/// let bar = &mut ctx.accounts.bar.load_init()?;
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/// bar.authority = ctx.accounts.authority.key();
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/// bar.data = data;
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/// Ok(())
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/// }
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///
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/// pub fn update_bar(ctx: Context<UpdateBar>, data: u64) -> Result<()> {
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/// (*ctx.accounts.bar.load_mut()?).data = data;
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/// Ok(())
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/// }
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/// }
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///
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/// #[account(zero_copy)]
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/// #[derive(Default)]
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/// pub struct Bar {
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/// authority: Pubkey,
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/// data: u64
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/// }
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///
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/// #[derive(Accounts)]
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/// pub struct CreateBar<'info> {
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/// #[account(
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/// init,
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/// payer = authority
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/// )]
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/// bar: AccountLoader<'info, Bar>,
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/// #[account(mut)]
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/// authority: Signer<'info>,
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/// system_program: AccountInfo<'info>,
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/// }
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///
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/// #[derive(Accounts)]
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/// pub struct UpdateBar<'info> {
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/// #[account(
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/// mut,
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/// has_one = authority,
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/// )]
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/// pub bar: AccountLoader<'info, Bar>,
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/// pub authority: Signer<'info>,
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/// }
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/// ```
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#[derive(Clone)]
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pub struct AccountLoader<'info, T: ZeroCopy + Owner> {
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acc_info: AccountInfo<'info>,
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phantom: PhantomData<&'info T>,
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}
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impl<'info, T: ZeroCopy + Owner + fmt::Debug> fmt::Debug for AccountLoader<'info, T> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.debug_struct("AccountLoader")
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.field("acc_info", &self.acc_info)
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.field("phantom", &self.phantom)
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.finish()
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}
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}
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impl<'info, T: ZeroCopy + Owner> AccountLoader<'info, T> {
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fn new(acc_info: AccountInfo<'info>) -> AccountLoader<'info, T> {
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Self {
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acc_info,
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phantom: PhantomData,
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}
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}
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/// Constructs a new `Loader` from a previously initialized account.
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#[inline(never)]
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pub fn try_from(acc_info: &AccountInfo<'info>) -> Result<AccountLoader<'info, T>> {
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if acc_info.owner != &T::owner() {
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return Err(ErrorCode::AccountOwnedByWrongProgram.into());
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}
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let data: &[u8] = &acc_info.try_borrow_data()?;
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// Discriminator must match.
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let disc_bytes = array_ref![data, 0, 8];
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if disc_bytes != &T::discriminator() {
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return Err(ErrorCode::AccountDiscriminatorMismatch.into());
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}
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Ok(AccountLoader::new(acc_info.clone()))
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}
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/// Constructs a new `Loader` from an uninitialized account.
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#[inline(never)]
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pub fn try_from_unchecked(
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_program_id: &Pubkey,
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acc_info: &AccountInfo<'info>,
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) -> Result<AccountLoader<'info, T>> {
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if acc_info.owner != &T::owner() {
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return Err(ErrorCode::AccountOwnedByWrongProgram.into());
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}
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Ok(AccountLoader::new(acc_info.clone()))
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}
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/// Returns a Ref to the account data structure for reading.
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pub fn load(&self) -> Result<Ref<T>> {
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let data = self.acc_info.try_borrow_data()?;
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let disc_bytes = array_ref![data, 0, 8];
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if disc_bytes != &T::discriminator() {
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return Err(ErrorCode::AccountDiscriminatorMismatch.into());
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}
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Ok(Ref::map(data, |data| {
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bytemuck::from_bytes(&data[8..mem::size_of::<T>() + 8])
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}))
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}
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/// Returns a `RefMut` to the account data structure for reading or writing.
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pub fn load_mut(&self) -> Result<RefMut<T>> {
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// AccountInfo api allows you to borrow mut even if the account isn't
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// writable, so add this check for a better dev experience.
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if !self.acc_info.is_writable {
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return Err(ErrorCode::AccountNotMutable.into());
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}
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let data = self.acc_info.try_borrow_mut_data()?;
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let disc_bytes = array_ref![data, 0, 8];
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if disc_bytes != &T::discriminator() {
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return Err(ErrorCode::AccountDiscriminatorMismatch.into());
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}
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Ok(RefMut::map(data, |data| {
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bytemuck::from_bytes_mut(&mut data.deref_mut()[8..mem::size_of::<T>() + 8])
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}))
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}
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/// Returns a `RefMut` to the account data structure for reading or writing.
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/// Should only be called once, when the account is being initialized.
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pub fn load_init(&self) -> Result<RefMut<T>> {
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// AccountInfo api allows you to borrow mut even if the account isn't
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// writable, so add this check for a better dev experience.
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if !self.acc_info.is_writable {
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return Err(ErrorCode::AccountNotMutable.into());
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}
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let data = self.acc_info.try_borrow_mut_data()?;
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// The discriminator should be zero, since we're initializing.
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let mut disc_bytes = [0u8; 8];
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disc_bytes.copy_from_slice(&data[..8]);
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let discriminator = u64::from_le_bytes(disc_bytes);
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if discriminator != 0 {
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return Err(ErrorCode::AccountDiscriminatorAlreadySet.into());
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}
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Ok(RefMut::map(data, |data| {
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bytemuck::from_bytes_mut(&mut data.deref_mut()[8..mem::size_of::<T>() + 8])
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}))
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}
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}
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impl<'info, T: ZeroCopy + Owner> Accounts<'info> for AccountLoader<'info, T> {
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#[inline(never)]
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fn try_accounts(
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_program_id: &Pubkey,
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accounts: &mut &[AccountInfo<'info>],
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_ix_data: &[u8],
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_bumps: &mut BTreeMap<String, u8>,
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) -> Result<Self> {
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if accounts.is_empty() {
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return Err(ErrorCode::AccountNotEnoughKeys.into());
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}
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let account = &accounts[0];
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*accounts = &accounts[1..];
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let l = AccountLoader::try_from(account)?;
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Ok(l)
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}
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}
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impl<'info, T: ZeroCopy + Owner> AccountsExit<'info> for AccountLoader<'info, T> {
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// The account *cannot* be loaded when this is called.
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fn exit(&self, _program_id: &Pubkey) -> Result<()> {
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let mut data = self.acc_info.try_borrow_mut_data()?;
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let dst: &mut [u8] = &mut data;
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let mut cursor = std::io::Cursor::new(dst);
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cursor.write_all(&T::discriminator()).unwrap();
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Ok(())
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}
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}
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impl<'info, T: ZeroCopy + Owner> AccountsClose<'info> for AccountLoader<'info, T> {
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fn close(&self, sol_destination: AccountInfo<'info>) -> Result<()> {
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crate::common::close(self.to_account_info(), sol_destination)
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}
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}
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impl<'info, T: ZeroCopy + Owner> ToAccountMetas for AccountLoader<'info, T> {
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fn to_account_metas(&self, is_signer: Option<bool>) -> Vec<AccountMeta> {
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let is_signer = is_signer.unwrap_or(self.acc_info.is_signer);
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let meta = match self.acc_info.is_writable {
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false => AccountMeta::new_readonly(*self.acc_info.key, is_signer),
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true => AccountMeta::new(*self.acc_info.key, is_signer),
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};
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vec![meta]
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}
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}
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impl<'info, T: ZeroCopy + Owner> AsRef<AccountInfo<'info>> for AccountLoader<'info, T> {
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fn as_ref(&self) -> &AccountInfo<'info> {
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&self.acc_info
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}
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}
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impl<'info, T: ZeroCopy + Owner> ToAccountInfos<'info> for AccountLoader<'info, T> {
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fn to_account_infos(&self) -> Vec<AccountInfo<'info>> {
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vec![self.acc_info.clone()]
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}
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}
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