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// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
/*!
The compiler code necessary for #[deriving(Decodable)]. See
encodable.rs for more.
*/
use std::vec;
use ast::{MetaItem, item, Expr, MutMutable};
use codemap::Span;
use ext::base::ExtCtxt;
use ext::build::AstBuilder;
use ext::deriving::generic::*;
pub fn expand_deriving_decodable(cx: @ExtCtxt,
span: Span,
mitem: @MetaItem,
in_items: ~[@item]) -> ~[@item] {
let trait_def = TraitDef {
path: Path::new_(~["extra", "serialize", "Decodable"], None,
~[~Literal(Path::new_local("__D"))], true),
additional_bounds: ~[],
generics: LifetimeBounds {
lifetimes: ~[],
bounds: ~[("__D", ~[Path::new(~["extra", "serialize", "Decoder"])])],
},
methods: ~[
MethodDef {
name: "decode",
generics: LifetimeBounds::empty(),
explicit_self: None,
args: ~[Ptr(~Literal(Path::new_local("__D")),
Borrowed(None, MutMutable))],
ret_ty: Self,
const_nonmatching: true,
combine_substructure: decodable_substructure,
},
]
};
trait_def.expand(cx, span, mitem, in_items)
}
fn decodable_substructure(cx: @ExtCtxt, span: Span,
substr: &Substructure) -> @Expr {
let decoder = substr.nonself_args[0];
let recurse = ~[cx.ident_of("extra"),
cx.ident_of("serialize"),
cx.ident_of("Decodable"),
cx.ident_of("decode")];
// throw an underscore in front to suppress unused variable warnings
let blkarg = cx.ident_of("_d");
let blkdecoder = cx.expr_ident(span, blkarg);
let calldecode = cx.expr_call_global(span, recurse, ~[blkdecoder]);
let lambdadecode = cx.lambda_expr_1(span, calldecode, blkarg);
return match *substr.fields {
StaticStruct(_, ref summary) => {
let nfields = match *summary {
Left(n) => n, Right(ref fields) => fields.len()
};
let read_struct_field = cx.ident_of("read_struct_field");
let getarg = |name: @str, field: uint| {
cx.expr_method_call(span, blkdecoder, read_struct_field,
~[cx.expr_str(span, name),
cx.expr_uint(span, field),
lambdadecode])
};
let result = match *summary {
Left(n) => {
if n == 0 {
cx.expr_ident(span, substr.type_ident)
} else {
let mut fields = vec::with_capacity(n);
for i in range(0, n) {
fields.push(getarg(fmt!("_field%u", i).to_managed(), i));
}
cx.expr_call_ident(span, substr.type_ident, fields)
}
}
Right(ref fields) => {
let fields = do fields.iter().enumerate().map |(i, f)| {
cx.field_imm(span, *f, getarg(cx.str_of(*f), i))
}.collect();
cx.expr_struct_ident(span, substr.type_ident, fields)
}
};
cx.expr_method_call(span, decoder, cx.ident_of("read_struct"),
~[cx.expr_str(span, cx.str_of(substr.type_ident)),
cx.expr_uint(span, nfields),
cx.lambda_expr_1(span, result, blkarg)])
}
StaticEnum(_, ref fields) => {
let variant = cx.ident_of("i");
let mut arms = ~[];
let mut variants = ~[];
let rvariant_arg = cx.ident_of("read_enum_variant_arg");
for (i, f) in fields.iter().enumerate() {
let (name, parts) = match *f { (i, ref p) => (i, p) };
variants.push(cx.expr_str(span, cx.str_of(name)));
let getarg = |field: uint| {
cx.expr_method_call(span, blkdecoder, rvariant_arg,
~[cx.expr_uint(span, field),
lambdadecode])
};
let decoded = match *parts {
Left(n) => {
if n == 0 {
cx.expr_ident(span, name)
} else {
let mut fields = vec::with_capacity(n);
for i in range(0u, n) {
fields.push(getarg(i));
}
cx.expr_call_ident(span, name, fields)
}
}
Right(ref fields) => {
let fields = do fields.iter().enumerate().map |(i, f)| {
cx.field_imm(span, *f, getarg(i))
}.collect();
cx.expr_struct_ident(span, name, fields)
}
};
arms.push(cx.arm(span,
~[cx.pat_lit(span, cx.expr_uint(span, i))],
decoded));
}
arms.push(cx.arm_unreachable(span));
let result = cx.expr_match(span, cx.expr_ident(span, variant), arms);
let lambda = cx.lambda_expr(span, ~[blkarg, variant], result);
let variant_vec = cx.expr_vec(span, variants);
let result = cx.expr_method_call(span, blkdecoder,
cx.ident_of("read_enum_variant"),
~[variant_vec, lambda]);
cx.expr_method_call(span, decoder, cx.ident_of("read_enum"),
~[cx.expr_str(span, cx.str_of(substr.type_ident)),
cx.lambda_expr_1(span, result, blkarg)])
}
_ => cx.bug("expected StaticEnum or StaticStruct in deriving(Decodable)")
};
}
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