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Add an API for persisting arbitrary fields

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This commit is contained in:
Robbert van der Helm 2022-01-30 16:14:52 +01:00
parent c286958c63
commit 8ac036f6cc
2 changed files with 121 additions and 22 deletions
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118
nih_plug_derive/src/lib.rs
View file

@ -4,7 +4,7 @@ use proc_macro::TokenStream;
use quote::quote;
use syn::spanned::Spanned;
#[proc_macro_derive(Params, attributes(id))]
#[proc_macro_derive(Params, attributes(id, persist))]
pub fn derive_params(input: TokenStream) -> TokenStream {
let ast = syn::parse_macro_input!(input as syn::DeriveInput);
@ -24,19 +24,23 @@ pub fn derive_params(input: TokenStream) -> TokenStream {
}
};
// We only care about fields with an `id` attribute. We'll build a that creates a hashmap
// containing pointers to those parmaeters.
let mut param_insert_tokens = Vec::new();
// We only care about fields with `id` and `persist` attributes. For the `id` fields we'll build
// a mapping function that creates a hashmap containing pointers to those parmaeters. For the
// `persist` function we'll create functions that serialize and deserialize those fields
// individually (so they can be added and removed independently of eachother) using JSON.
let mut param_mapping_insert_tokens = Vec::new();
let mut field_serialize_tokens = Vec::new();
let mut field_deserialize_tokens = Vec::new();
for field in fields.named {
let field_name = match &field.ident {
Some(ident) => ident,
_ => continue,
};
// We'll add another attribute for persistent fields later, and that's going to be mutually
// exclusive with this id attribute
let mut id_attr = None;
for attr in field.attrs {
// These two attributes are mutually exclusive
let mut id_attr: Option<String> = None;
let mut persist_attr: Option<String> = None;
for attr in &field.attrs {
if attr.path.is_ident("id") {
match attr.parse_meta() {
Ok(syn::Meta::NameValue(syn::MetaNameValue {
@ -60,14 +64,83 @@ pub fn derive_params(input: TokenStream) -> TokenStream {
.into()
}
};
} else if attr.path.is_ident("persist") {
match attr.parse_meta() {
Ok(syn::Meta::NameValue(syn::MetaNameValue {
lit: syn::Lit::Str(s),
..
})) => {
if persist_attr.is_none() {
persist_attr = Some(s.value());
} else {
return syn::Error::new(attr.span(), "Duplicate persist attribute")
.to_compile_error()
.into();
}
}
_ => {
return syn::Error::new(
attr.span(),
"The persist attribute should be a key-value pair with a string argument: #[persist = \"foo_bar\"]",
)
.to_compile_error()
.into()
}
};
}
}
if let Some(param_id) = id_attr {
// The specific parameter types know how to convert themselves into the correct ParamPtr
// variant
param_insert_tokens
.push(quote! { param_map.insert(#param_id, self.#field_name.as_ptr()); });
match (id_attr, persist_attr) {
(Some(param_id), None) => {
// The specific parameter types know how to convert themselves into the correct ParamPtr
// variant
param_mapping_insert_tokens
.push(quote! { param_map.insert(#param_id, self.#field_name.as_ptr()); });
}
(None, Some(stable_name)) => {
// We don't know anything about the field types, but because we can generate this
// function we get type erasure for free since we only need to worry about byte
// vectors
field_serialize_tokens.push(quote! {
match ::nih_plug::params::serialize_field(&self.#field_name) {
Ok(data) => {
serialized.insert(String::from(#stable_name), data);
}
Err(err) => {
::nih_plug::nih_log!(
"Could not serialize '{}': {}",
#stable_name,
err
)
}
};
});
field_deserialize_tokens.push(quote! {
#stable_name => {
match ::nih_plug::params::deserialize_field(&data) {
Ok(deserialized) => {
self.#field_name = deserialized;
}
Err(err) => {
::nih_plug::nih_log!(
"Could not deserialize '{}': {}",
#stable_name,
err
)
}
};
}
});
}
(Some(_), Some(_)) => {
return syn::Error::new(
field.span(),
"The id and persist attributes are mutually exclusive",
)
.to_compile_error()
.into();
}
(None, None) => (),
}
}
@ -78,10 +151,27 @@ pub fn derive_params(input: TokenStream) -> TokenStream {
) -> std::collections::HashMap<&'static str, nih_plug::params::ParamPtr> {
let mut param_map = std::collections::HashMap::new();
#(#param_insert_tokens)*
#(#param_mapping_insert_tokens)*
param_map
}
fn serialize_fields(&self) -> ::std::collections::HashMap<String, Vec<u8>> {
let mut serialized = ::std::collections::HashMap::new();
#(#field_serialize_tokens)*
serialized
}
fn deserialize_fields(&mut self, serialized: ::std::collections::HashMap<&str, Vec<u8>>) {
for (field_name, data) in serialized {
match field_name {
#(#field_deserialize_tokens)*
_ => nih_log!("Unknown field name: {}", field_name),
}
}
}
}
}
.into()

25
src/params.rs
View file

@ -21,6 +21,11 @@ use std::pin::Pin;
pub type FloatParam = PlainParam<f32>;
pub type IntParam = PlainParam<i32>;
/// Re-export for use in the [Params] proc-macro.
pub use serde_json::from_slice as deserialize_field;
/// Re-export for use in the [Params] proc-macro.
pub use serde_json::to_vec as serialize_field;
/// A distribution for a parameter's range. Probably need to add some forms of skewed ranges and
/// maybe a callback based implementation at some point.
#[derive(Debug)]
@ -292,16 +297,20 @@ impl NormalizebleRange<i32> for Range<i32> {
/// This implementation is safe when using from the wrapper because the plugin object needs to be
/// pinned, and it can never outlive the wrapper.
pub trait Params {
/// Create a mapping from unique parameter IDs to parameters. Dereferencing the pointers stored
/// in the values is only valid as long as this pinned object is valid.
/// Create a mapping from unique parameter IDs to parameters. This is done for every parameter
/// field marked with `#[id = "stable_name"]`. Dereferencing the pointers stored in the values
/// is only valid as long as this pinned object is valid.
fn param_map(self: Pin<&Self>) -> HashMap<&'static str, ParamPtr>;
// TODO: Also handle custom state persistence in this state. Instead o having a callback for
// custom state loading and restoring, it will be way nicer to use serde for this. Another
// attribute `#[persist]` can mark fields that are `Serialize + Deserialize`. They these
// fields can then be serialized alongside the `param_id: normalized_value` pairs for
// normal parameters.
// fn persistent_fields(self: Pin<&mut Self>) -> Vec<&mut (dyn Serialize + Deserialize + Send + Sync)>;
/// Serialize all fields marked with `#[persist = "stable_name"]` into a hash map containing
/// JSON-representations of those fields so they can be written to the plugin's state and
/// recalled later. This uses [serialize_field] under the hood.
fn serialize_fields(&self) -> HashMap<String, Vec<u8>>;
/// Restore all fields marked with `#[persist = "stable_name"]` from a hashmap created by
/// [Self::serialize_fields]. This gets called when the plugin's state is being restored. This
/// uses [deserialize_field] under the hood.
fn deserialize_fields(&mut self, serialized: HashMap<&str, Vec<u8>>);
}
/// Internal pointers to parameters. This is an implementation detail used by the wrappers.