Add bitfield derive (#16)

protocol-derive/src/parse.rs

@@ -3,7 +3,7 @@ use proc_macro2::Ident;
 use std::iter::FromIterator;
 use syn::punctuated::Punctuated;
 use syn::{
-    Attribute, Data, DeriveInput, ExprLit, Fields, FieldsNamed, Lit, Meta, NestedMeta, Type,
+    Attribute, Data, DeriveInput, ExprLit, Field, Fields, FieldsNamed, Lit, Meta, NestedMeta, Type,
 };
 use syn::{Error as SynError, Variant};
 use syn::{Expr, Token};
@@ -36,6 +36,7 @@ pub(crate) struct FieldData<'a> {
 pub(crate) enum AttributeData {
     With { module: String },
     MaxLength { length: usize },
+    Bitfield { idx: u8, position: BitfieldPosition },
     Empty,
 }
 
@@ -45,6 +46,13 @@ pub(crate) enum DiscriminantType {
     VarInt,
 }
 
+#[derive(Debug, Eq, PartialEq)]
+pub(crate) enum BitfieldPosition {
+    Start,
+    Intermediate,
+    End,
+}
+
 pub(crate) fn parse_derive_input(
     input: &DeriveInput,
 ) -> Result<DeriveInputParseResult, DeriveInputParserError> {
@@ -77,7 +85,7 @@ fn parse_discriminant_type(
     attributes: &Vec<Attribute>,
 ) -> Result<DiscriminantType, DeriveInputParserError> {
     let nested_metas = parse_attributes_nested_metas(attributes)?;
-    let attribute = parse_attribute(nested_metas)?;
+    let attribute = parse_attribute(nested_metas, None, 0)?;
 
     match attribute {
         AttributeData::With { module } if module == "var_int" => Ok(DiscriminantType::VarInt),
@@ -127,13 +135,26 @@ fn parse_variant_discriminant(variant: &Variant) -> Option<usize> {
 
 fn parse_fields(named_fields: &FieldsNamed) -> Result<Vec<FieldData>, DeriveInputParserError> {
     let mut fields_data = Vec::new();
+    let mut current_bitfield_idx = 0;
 
-    for field in named_fields.named.iter() {
+    let fields: Vec<&Field> = named_fields.named.iter().collect();
+
+    for (idx, field) in fields.iter().enumerate() {
         let name = field.ident.as_ref().unwrap();
         let ty = &field.ty;
 
         let nested_metas = parse_attributes_nested_metas(&field.attrs)?;
-        let attribute = parse_attribute(nested_metas)?;
+
+        let next_field_opt = fields.get(idx + 1);
+        let next_nested_metas_opt = next_field_opt
+            .and_then(|next_field| parse_attributes_nested_metas(&next_field.attrs).ok());
+
+        let attribute = parse_attribute(nested_metas, next_nested_metas_opt, current_bitfield_idx)?;
+
+        match attribute {
+            AttributeData::Bitfield { .. } => current_bitfield_idx += 1,
+            _ => current_bitfield_idx = 0,
+        }
 
         fields_data.push(FieldData {
             name,
@@ -165,12 +186,23 @@ fn parse_attributes_nested_metas(
     Ok(nested_metas.into_iter().flatten().collect())
 }
 
-fn parse_attribute(nested_metas: Vec<NestedMeta>) -> Result<AttributeData, DeriveInputParserError> {
-    let attribute_parsers: Vec<fn(&NestedMeta) -> Result<AttributeData, AttributeError>> =
+fn parse_attribute(
+    nested_metas: Vec<NestedMeta>,
+    next_nested_metas_opt: Option<Vec<NestedMeta>>,
+    current_bitfield_idx: u8,
+) -> Result<AttributeData, DeriveInputParserError> {
+    let simple_attribute_parsers: Vec<fn(&NestedMeta) -> Result<AttributeData, AttributeError>> =
         vec![get_module_attribute, get_max_length_attribute];
 
     for nested_meta in nested_metas.iter() {
-        for attribute_parser in attribute_parsers.iter() {
+        let bitfield_attribute =
+            get_bitfield_attribute(current_bitfield_idx, nested_meta, &next_nested_metas_opt);
+
+        if bitfield_attribute != AttributeData::Empty {
+            return Ok(bitfield_attribute);
+        }
+
+        for attribute_parser in simple_attribute_parsers.iter() {
             let attribute = attribute_parser(nested_meta)?;
 
             if attribute != AttributeData::Empty {
@@ -211,3 +243,49 @@ fn get_max_length_attribute(nested_meta: &NestedMeta) -> Result<AttributeData, A
 
     Ok(AttributeData::Empty)
 }
+
+fn get_bitfield_attribute(
+    current_bitfield_idx: u8,
+    nested_meta: &NestedMeta,
+    next_nested_metas_opt: &Option<Vec<NestedMeta>>,
+) -> AttributeData {
+    if is_bitfield_attribute(nested_meta) {
+        let position = calc_bitfield_position(current_bitfield_idx, next_nested_metas_opt);
+
+        AttributeData::Bitfield {
+            idx: current_bitfield_idx,
+            position,
+        }
+    } else {
+        AttributeData::Empty
+    }
+}
+
+fn calc_bitfield_position(
+    current_bitfield_idx: u8,
+    next_nested_metas_opt: &Option<Vec<NestedMeta>>,
+) -> BitfieldPosition {
+    fn next_has_bitfield_attribute(next_nested_metas: &Vec<NestedMeta>) -> bool {
+        next_nested_metas
+            .iter()
+            .any(|nested_meta| is_bitfield_attribute(nested_meta))
+    }
+
+    match next_nested_metas_opt {
+        Some(next_nested_metas) if (next_has_bitfield_attribute(&next_nested_metas)) => {
+            if current_bitfield_idx == 0 {
+                BitfieldPosition::Start
+            } else {
+                BitfieldPosition::Intermediate
+            }
+        }
+        _ => BitfieldPosition::End,
+    }
+}
+
+fn is_bitfield_attribute(nested_meta: &NestedMeta) -> bool {
+    match nested_meta {
+        NestedMeta::Meta(Meta::Path(path)) => path.is_ident("bitfield"),
+        _ => false,
+    }
+}

protocol-derive/src/render/decoder.rs

@@ -1,4 +1,4 @@
-use crate::parse::{AttributeData, DiscriminantType, FieldData, VariantData};
+use crate::parse::{AttributeData, BitfieldPosition, DiscriminantType, FieldData, VariantData};
 use proc_macro2::TokenStream as TokenStream2;
 use proc_macro2::{Ident, Span};
 use quote::quote;
@@ -140,6 +140,7 @@ fn render_field(field: &FieldData) -> TokenStream2 {
     match &field.attribute {
         AttributeData::With { module } => render_with_field(name, module),
         AttributeData::MaxLength { length } => render_max_length_field(name, *length as u16),
+        AttributeData::Bitfield { idx, position } => render_bitfield(name, *idx, position),
         AttributeData::Empty => render_simple_field(name, ty),
     }
 }
@@ -163,3 +164,22 @@ fn render_max_length_field(name: &Ident, max_length: u16) -> TokenStream2 {
         let #name = crate::decoder::DecoderReadExt::read_string(reader, #max_length)?;
     }
 }
+
+fn render_bitfield(name: &Ident, idx: u8, position: &BitfieldPosition) -> TokenStream2 {
+    let mask = 1u8 << idx;
+
+    let render_mask = quote! {
+        let #name = flags & #mask > 0;
+    };
+
+    match position {
+        BitfieldPosition::Start => {
+            quote! {
+              let flags = reader.read_u8()?;
+
+              #render_mask
+            }
+        }
+        _ => render_mask,
+    }
+}

protocol-derive/src/render/encoder.rs

@@ -1,4 +1,4 @@
-use crate::parse::{AttributeData, DiscriminantType, FieldData, VariantData};
+use crate::parse::{AttributeData, BitfieldPosition, DiscriminantType, FieldData, VariantData};
 use proc_macro2::TokenStream as TokenStream2;
 use proc_macro2::{Ident, Span};
 use quote::quote;
@@ -130,6 +130,7 @@ fn render_field(field: &FieldData, with_self: bool) -> TokenStream2 {
         AttributeData::MaxLength { length } => {
             render_max_length_field(name, *length as u16, with_self)
         }
+        AttributeData::Bitfield { idx, position } => render_bitfield(name, *idx, position),
         AttributeData::Empty => render_simple_field(name, with_self),
     }
 }
@@ -155,6 +156,32 @@ fn render_max_length_field(name: &Ident, max_length: u16, with_self: bool) -> To
     }
 }
 
+fn render_bitfield(name: &Ident, idx: u8, position: &BitfieldPosition) -> TokenStream2 {
+    let mask = 1u8 << idx;
+
+    let render_mask = quote! {
+        if self.#name {
+            flags |= #mask;
+        }
+    };
+
+    match position {
+        BitfieldPosition::Start => quote!(
+            let mut flags = 0;
+
+            #render_mask
+        ),
+        BitfieldPosition::Intermediate => render_mask,
+        BitfieldPosition::End => {
+            quote! {
+                #render_mask
+
+                writer.write_u8(flags)?;
+            }
+        }
+    }
+}
+
 fn get_field_final_name(name: &Ident, with_self: bool) -> TokenStream2 {
     if with_self {
         quote!(&self.#name)

protocol/src/version/v1_14_4/game.rs

@@ -12,6 +12,7 @@ use uuid::Uuid;
 pub enum GameServerBoundPacket {
     ServerBoundChatMessage(ServerBoundChatMessage),
     ServerBoundKeepAlive(ServerBoundKeepAlive),
+    ServerBoundAbilities(ServerBoundAbilities),
 }
 
 pub enum GameClientBoundPacket {
@@ -29,6 +30,7 @@ impl GameServerBoundPacket {
         match self {
             GameServerBoundPacket::ServerBoundChatMessage(_) => 0x03,
             GameServerBoundPacket::ServerBoundKeepAlive(_) => 0x0F,
+            GameServerBoundPacket::ServerBoundAbilities(_) => 0x19,
         }
     }
 
@@ -332,6 +334,20 @@ pub enum EntityActionId {
     StartFlyingWithElytra,
 }
 
+#[derive(Encoder, Decoder, Debug, PartialEq)]
+pub struct ServerBoundAbilities {
+    #[data_type(bitfield)]
+    pub invulnerable: bool,
+    #[data_type(bitfield)]
+    pub allow_flying: bool,
+    #[data_type(bitfield)]
+    pub flying: bool,
+    #[data_type(bitfield)]
+    pub creative_mode: bool,
+    pub fly_speed: f32,
+    pub walk_speed: f32,
+}
+
 #[cfg(test)]
 mod tests {
     use crate::data::chat::Payload;
@@ -686,4 +702,33 @@ mod tests {
             }
         );
     }
+
+    #[test]
+    fn test_serverbound_abilities_encode() {
+        let abilities = ServerBoundAbilities {
+            invulnerable: true,
+            flying: true,
+            allow_flying: false,
+            creative_mode: true,
+            fly_speed: 0.0,
+            walk_speed: 0.0,
+        };
+
+        let mut vec = Vec::new();
+        abilities.encode(&mut vec).unwrap();
+
+        assert_eq!(vec, [13, 0, 0, 0, 0, 0, 0, 0, 0]);
+    }
+
+    #[test]
+    fn test_serverbound_abilities_decode() {
+        let vec = [13, 0, 0, 0, 0, 0, 0, 0, 0].to_vec();
+        let mut cursor = Cursor::new(vec);
+
+        let abilities = ServerBoundAbilities::decode(&mut cursor).unwrap();
+        assert!(abilities.invulnerable);
+        assert!(!abilities.allow_flying);
+        assert!(abilities.flying);
+        assert!(abilities.creative_mode);
+    }
 }