add derive for raw request body

gotham_restful_derive/src/from_body.rs

@@ -0,0 +1,69 @@
+use proc_macro::TokenStream;
+use quote::quote;
+use syn::{
+	Fields,
+	ItemStruct,
+	parse_macro_input
+};
+
+pub fn expand_from_body(tokens : TokenStream) -> TokenStream
+{
+	let krate = super::krate();
+	let input = parse_macro_input!(tokens as ItemStruct);
+	let ident = input.ident;
+	let generics = input.generics;
+	
+	let (were, body) = match input.fields {
+		Fields::Named(named) => {
+			let fields = named.named;
+			if fields.len() == 0 // basically unit
+			{
+				(quote!(), quote!(Self{}))
+			}
+			else if fields.len() == 1
+			{
+				let field = fields.first().unwrap();
+				let field_ident = field.ident.as_ref().unwrap();
+				let field_ty = &field.ty;
+				(quote!(where #field_ty : for<'a> From<&'a [u8]>), quote!(Self { #field_ident: body.into() }))
+			}
+			else
+			{
+				panic!("FromBody can only be derived for structs with at most one field")
+			}
+		},
+		Fields::Unnamed(unnamed) => {
+			let fields = unnamed.unnamed;
+			if fields.len() == 0 // basically unit
+			{
+				(quote!(), quote!(Self{}))
+			}
+			else if fields.len() == 1
+			{
+				let field = fields.first().unwrap();
+				let field_ty = &field.ty;
+				(quote!(where #field_ty : for<'a> From<&'a [u8]>), quote!(Self(body.into())))
+			}
+			else
+			{
+				panic!("FromBody can only be derived for structs with at most one field")
+			}
+		},
+		Fields::Unit => (quote!(), quote!(Self{}))
+	};
+	
+	let output = quote! {
+		impl #generics #krate::FromBody for #ident #generics
+		#were
+		{
+			type Err = String;
+			
+			fn from_body(body : #krate::Chunk, _content_type : #krate::Mime) -> Result<Self, Self::Err>
+			{
+				let body : &[u8] = &body;
+				Ok(#body)
+			}
+		}
+	};
+	output.into()
+}