binrw_derive 0.11.2

Derive macro for binrw
Documentation 
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use crate::{
    binrw::{
        codegen::{
            get_destructured_imports, get_endian,
            sanitization::{ARGS, MAP_WRITER_TYPE_HINT, OPT, WRITER, WRITE_METHOD},
        },
        parser::{CondEndian, Input, Magic},
    },
    util::quote_spanned_any,
};
use proc_macro2::{Ident, TokenStream};
use quote::quote;
use syn::spanned::Spanned;

pub(crate) struct PreludeGenerator<'a> {
    out: TokenStream,
    input: Option<&'a Input>,
    name: Option<&'a Ident>,
    writer_var: &'a TokenStream,
}

impl<'a> PreludeGenerator<'a> {
    pub(crate) fn new(
        out: TokenStream,
        input: Option<&'a Input>,
        name: Option<&'a Ident>,
        writer_var: &'a TokenStream,
    ) -> Self {
        Self {
            out,
            input,
            name,
            writer_var,
        }
    }

    pub(crate) fn prefix_imports(mut self) -> Self {
        if let Some(imports) = self
            .input
            .and_then(|input| get_destructured_imports(input.imports(), self.name, true))
        {
            let out = self.out;
            self.out = quote! {
                let #imports = #ARGS;
                #out
            };
        }

        self
    }

    pub(crate) fn prefix_magic(mut self, magic: &Magic) -> Self {
        if let Some(magic) = magic {
            let writer_var = &self.writer_var;
            let magic = magic.match_value();
            let out = self.out;
            self.out = quote! {
                #WRITE_METHOD (
                    &#magic,
                    #writer_var,
                    #OPT,
                    ()
                )?;

                #out
            };
        }

        self
    }

    pub(crate) fn prefix_endian(mut self, endian: &CondEndian) -> Self {
        let endian = get_endian(endian);
        let out = self.out;
        self.out = quote! {
            let #OPT = #endian;
            #out
        };

        self
    }

    pub(crate) fn prefix_map_stream(mut self) -> Self {
        if let Some(input) = self.input {
            if let Some(map_stream) = input.map_stream() {
                let outer_writer = input.stream_ident_or(WRITER);
                let inner_writer = &self.writer_var;
                let tail = self.out;
                self.out = quote_spanned_any! { map_stream.span()=>
                    let #inner_writer = &mut #MAP_WRITER_TYPE_HINT::<W, _, _>(#map_stream)(#outer_writer);
                    #tail
                };
            }
        }

        self
    }

    pub(crate) fn finish(self) -> TokenStream {
        self.out
    }
}