src/metadata.rs

   1 use std::fs::File;
   2 use std::path::Path;
   3
   4 use rustc::middle::cstore::{EncodedMetadata, MetadataLoader};
   5 use rustc::session::config;
   6 use rustc::ty::TyCtxt;
   7 use rustc_codegen_ssa::METADATA_FILENAME;
   8 use rustc_data_structures::owning_ref::{self, OwningRef};
   9 use rustc_data_structures::rustc_erase_owner;
  10 use rustc_target::spec::Target;
  11
  12 pub struct CraneliftMetadataLoader;
  13
  14 impl MetadataLoader for CraneliftMetadataLoader {
  15     fn get_rlib_metadata(
  16         &self,
  17         _target: &Target,
  18         path: &Path,
  19     ) -> Result<owning_ref::ErasedBoxRef<[u8]>, String> {
  20         let mut archive = ar::Archive::new(File::open(path).map_err(|e| format!("{:?}", e))?);
  21         // Iterate over all entries in the archive:
  22         while let Some(entry_result) = archive.next_entry() {
  23             let mut entry = entry_result.map_err(|e| format!("{:?}", e))?;
  24             if entry.header().identifier() == METADATA_FILENAME.as_bytes() {
  25                 let mut buf = Vec::new();
  26                 ::std::io::copy(&mut entry, &mut buf).map_err(|e| format!("{:?}", e))?;
  27                 let buf: OwningRef<Vec<u8>, [u8]> = OwningRef::new(buf).into();
  28                 return Ok(rustc_erase_owner!(buf.map_owner_box()));
  29             }
  30         }
  31
  32         Err("couldn't find metadata entry".to_string())
  33         //self.get_dylib_metadata(target, path)
  34     }
  35
  36     fn get_dylib_metadata(
  37         &self,
  38         _target: &Target,
  39         path: &Path,
  40     ) -> Result<owning_ref::ErasedBoxRef<[u8]>, String> {
  41         use object::Object;
  42         let file = std::fs::read(path).map_err(|e| format!("read:{:?}", e))?;
  43         let file = object::File::parse(&file).map_err(|e| format!("parse: {:?}", e))?;
  44         let buf = file
  45             .section_data_by_name(".rustc")
  46             .ok_or("no .rustc section")?
  47             .into_owned();
  48         let buf: OwningRef<Vec<u8>, [u8]> = OwningRef::new(buf).into();
  49         Ok(rustc_erase_owner!(buf.map_owner_box()))
  50     }
  51 }
  52
  53 // Adapted from https://github.com/rust-lang/rust/blob/da573206f87b5510de4b0ee1a9c044127e409bd3/src/librustc_codegen_llvm/base.rs#L47-L112
  54 pub fn write_metadata(tcx: TyCtxt<'_>, artifact: &mut faerie::Artifact) -> EncodedMetadata {
  55     use flate2::write::DeflateEncoder;
  56     use flate2::Compression;
  57     use std::io::Write;
  58
  59     #[derive(PartialEq, Eq, PartialOrd, Ord)]
  60     enum MetadataKind {
  61         None,
  62         Uncompressed,
  63         Compressed,
  64     }
  65
  66     let kind = tcx
  67         .sess
  68         .crate_types
  69         .borrow()
  70         .iter()
  71         .map(|ty| match *ty {
  72             config::CrateType::Executable
  73             | config::CrateType::Staticlib
  74             | config::CrateType::Cdylib => MetadataKind::None,
  75
  76             config::CrateType::Rlib => MetadataKind::Uncompressed,
  77
  78             config::CrateType::Dylib | config::CrateType::ProcMacro => MetadataKind::Compressed,
  79         })
  80         .max()
  81         .unwrap_or(MetadataKind::None);
  82
  83     if kind == MetadataKind::None {
  84         return EncodedMetadata::new();
  85     }
  86
  87     let metadata = tcx.encode_metadata();
  88     if kind == MetadataKind::Uncompressed {
  89         return metadata;
  90     }
  91
  92     assert!(kind == MetadataKind::Compressed);
  93     let mut compressed = tcx.metadata_encoding_version();
  94     DeflateEncoder::new(&mut compressed, Compression::fast())
  95         .write_all(&metadata.raw_data)
  96         .unwrap();
  97
  98     artifact
  99         .declare(".rustc", faerie::Decl::section(faerie::SectionKind::Data))
 100         .unwrap();
 101     artifact
 102         .define_with_symbols(".rustc", compressed, {
 103             let mut map = std::collections::BTreeMap::new();
 104             // FIXME implement faerie elf backend section custom symbols
 105             // For MachO this is necessary to prevent the linker from throwing away the .rustc section,
 106             // but for ELF it isn't.
 107             if tcx.sess.target.target.options.is_like_osx {
 108                 map.insert(
 109                     rustc::middle::exported_symbols::metadata_symbol_name(tcx),
 110                     0,
 111                 );
 112             }
 113             map
 114         })
 115         .unwrap();
 116
 117     metadata
 118 }