compiler/rustc_metadata/src/rmeta/def_path_hash_map.rs

   1 use crate::rmeta::DecodeContext;
   2 use crate::rmeta::EncodeContext;
   3 use crate::rmeta::MetadataBlob;
   4 use rustc_data_structures::owning_ref::OwningRef;
   5 use rustc_hir::def_path_hash_map::{Config as HashMapConfig, DefPathHashMap};
   6 use rustc_middle::parameterized_over_tcx;
   7 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
   8 use rustc_span::def_id::{DefIndex, DefPathHash};
   9
  10 pub(crate) enum DefPathHashMapRef<'tcx> {
  11     OwnedFromMetadata(odht::HashTable<HashMapConfig, OwningRef<MetadataBlob, [u8]>>),
  12     BorrowedFromTcx(&'tcx DefPathHashMap),
  13 }
  14
  15 parameterized_over_tcx! {
  16     DefPathHashMapRef,
  17 }
  18
  19 impl DefPathHashMapRef<'_> {
  20     #[inline]
  21     pub fn def_path_hash_to_def_index(&self, def_path_hash: &DefPathHash) -> DefIndex {
  22         match *self {
  23             DefPathHashMapRef::OwnedFromMetadata(ref map) => map.get(def_path_hash).unwrap(),
  24             DefPathHashMapRef::BorrowedFromTcx(_) => {
  25                 panic!("DefPathHashMap::BorrowedFromTcx variant only exists for serialization")
  26             }
  27         }
  28     }
  29 }
  30
  31 impl<'a, 'tcx> Encodable<EncodeContext<'a, 'tcx>> for DefPathHashMapRef<'tcx> {
  32     fn encode(&self, e: &mut EncodeContext<'a, 'tcx>) {
  33         match *self {
  34             DefPathHashMapRef::BorrowedFromTcx(def_path_hash_map) => {
  35                 let bytes = def_path_hash_map.raw_bytes();
  36                 e.emit_usize(bytes.len());
  37                 e.emit_raw_bytes(bytes);
  38             }
  39             DefPathHashMapRef::OwnedFromMetadata(_) => {
  40                 panic!("DefPathHashMap::OwnedFromMetadata variant only exists for deserialization")
  41             }
  42         }
  43     }
  44 }
  45
  46 impl<'a, 'tcx> Decodable<DecodeContext<'a, 'tcx>> for DefPathHashMapRef<'static> {
  47     fn decode(d: &mut DecodeContext<'a, 'tcx>) -> DefPathHashMapRef<'static> {
  48         // Import TyDecoder so we can access the DecodeContext::position() method
  49         use crate::rustc_middle::ty::codec::TyDecoder;
  50
  51         let len = d.read_usize();
  52         let pos = d.position();
  53         let o = OwningRef::new(d.blob().clone()).map(|x| &x[pos..pos + len]);
  54
  55         // Although we already have the data we need via the OwningRef, we still need
  56         // to advance the DecodeContext's position so it's in a valid state after
  57         // the method. We use read_raw_bytes() for that.
  58         let _ = d.read_raw_bytes(len);
  59
  60         let inner = odht::HashTable::from_raw_bytes(o).unwrap_or_else(|e| {
  61             panic!("decode error: {}", e);
  62         });
  63         DefPathHashMapRef::OwnedFromMetadata(inner)
  64     }
  65 }