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extern crate proc_macro;
use crate::proc_macro::TokenStream;
use quote::{quote, quote_spanned};
use syn::spanned::Spanned;
use syn::{Data, DeriveInput, Fields, Index};
use std::mem::size_of;
use syn;
#[proc_macro_derive(StructFromBytes)]
pub fn from_bytes_derive(input: TokenStream) -> TokenStream {
let ast = syn::parse(input).unwrap();
impl_from_bytes(&ast)
}
fn impl_from_bytes(ast: &syn::DeriveInput) -> TokenStream {
let name = &ast.ident;
let gen = quote! {
impl StructFromBytes for #name {
fn from_bytes(slice: &[u8], offset: usize) -> std::io::Result<Box<Self>> {
let size = Self::packed_size();
match Self::unpack_from_slice(&slice[offset..offset+size]) {
Ok(v) => Ok(Box::new(v)),
Err(why) => Err(std::io::Error::new(std::io::ErrorKind::InvalidData, format!("{:?}", why)))
}
}
}
};
gen.into()
}
#[proc_macro_derive(PackedSize_u8)]
pub fn packed_size_derive_u8(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
static_packed_size(size_of::<u8>(), input)
}
#[proc_macro_derive(PackedSize_u16)]
pub fn packed_size_derive_u16(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
static_packed_size(size_of::<u16>(), input)
}
#[proc_macro_derive(PackedSize_u32)]
pub fn packed_size_derive_u32(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
static_packed_size(size_of::<u32>(), input)
}
fn static_packed_size(size: usize, input: proc_macro::TokenStream) -> proc_macro::TokenStream {
let ast: DeriveInput = syn::parse(input).unwrap();
let name = &ast.ident;
let expanded = quote! {
impl PackedSize for #name {
fn packed_size() -> usize {
#size
}
}
};
expanded.into()
}
#[proc_macro_derive(PackedSize)]
pub fn packed_size_derive(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
let ast: DeriveInput = syn::parse(input).unwrap();
let name = &ast.ident;
let sum = packed_bytes_sum(&ast.data);
let expanded = quote! {
impl PackedSize for #name {
fn packed_size() -> usize {
#sum
}
}
};
expanded.into()
}
fn packed_bytes_sum(data: &Data) -> proc_macro2::TokenStream {
match *data {
Data::Struct(ref data) => {
match data.fields {
Fields::Named(ref fields) => {
let recurse = fields.named.iter().map(|f| {
let name = &f.ty;
quote_spanned! {f.span() =>
<#name>::packed_size()
}
});
quote! {
0 #(+ #recurse)*
}
}
Fields::Unnamed(ref fields) => {
let recurse = fields.unnamed.iter().enumerate().map(|(i, f)| {
let index = Index::from(i);
quote_spanned! {f.span()=>
&self.#index::PackedSize::packed_size()
}
});
quote! {
0 #(+ #recurse)*
}
}
Fields::Unit => {
quote!(0)
}
}
}
Data::Enum(_) | Data::Union(_) => unimplemented!(),
}
}