83 lines
3.0 KiB
Rust
83 lines
3.0 KiB
Rust
extern crate proc_macro;
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use quote::quote;
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use syn::parse_macro_input;
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/// The `#[state]` attribute defines the program's state struct, i.e., the
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/// program's global account singleton giving the program the illusion of state.
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///
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/// To allocate space into the account on initialization, pass in the account
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/// size into the macro, e.g., `#[state(SIZE)]`. Otherwise, the size of the
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/// account returned by the struct's `new` constructor will determine the
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/// account size. When determining a size, make sure to reserve enough space
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/// for the 8 byte account discriminator prepended to the account. That is,
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/// always use 8 extra bytes.
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///
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/// # Zero Copy Deserialization
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///
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/// Similar to the `#[account]` attribute one can enable zero copy
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/// deserialization by using the `zero_copy` argument:
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///
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/// ```ignore
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/// #[state(zero_copy)]
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/// ```
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///
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/// For more, see the [`account`](./attr.account.html) attribute.
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#[proc_macro_attribute]
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pub fn state(
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args: proc_macro::TokenStream,
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input: proc_macro::TokenStream,
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) -> proc_macro::TokenStream {
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let item_struct = parse_macro_input!(input as syn::ItemStruct);
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let struct_ident = &item_struct.ident;
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let is_zero_copy = args.to_string() == "zero_copy";
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let size_override = {
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if args.is_empty() {
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// No size override given. The account size is whatever is given
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// as the initialized value. Use the default implementation.
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quote! {
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impl anchor_lang::__private::AccountSize for #struct_ident {
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fn size(&self) -> std::result::Result<u64, anchor_lang::solana_program::program_error::ProgramError> {
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Ok(8 + self
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.try_to_vec()
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.map_err(|_| anchor_lang::__private::ErrorCode::AccountDidNotSerialize)?
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.len() as u64)
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}
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}
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}
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} else if is_zero_copy {
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quote! {
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impl anchor_lang::__private::AccountSize for #struct_ident {
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fn size(&self) -> std::result::Result<u64, anchor_lang::solana_program::program_error::ProgramError> {
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let len = anchor_lang::__private::bytemuck::bytes_of(self).len() as u64;
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Ok(8 + len)
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}
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}
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}
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} else {
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let size = proc_macro2::TokenStream::from(args);
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// Size override given to the macro. Use it.
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quote! {
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impl anchor_lang::__private::AccountSize for #struct_ident {
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fn size(&self) -> std::result::Result<u64, anchor_lang::solana_program::program_error::ProgramError> {
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Ok(#size)
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}
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}
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}
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}
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};
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let attribute = match is_zero_copy {
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false => quote! {#[account("state")]},
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true => quote! {#[account("state", zero_copy)]},
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};
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proc_macro::TokenStream::from(quote! {
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#attribute
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#item_struct
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#size_override
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})
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}
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