src/metadata.rs

   1 //! Reading and writing of the rustc metadata for rlibs and dylibs
   2
   3 use std::convert::TryFrom;
   4 use std::fs::File;
   5 use std::path::Path;
   6
   7 use rustc_codegen_ssa::METADATA_FILENAME;
   8 use rustc_data_structures::owning_ref::OwningRef;
   9 use rustc_data_structures::rustc_erase_owner;
  10 use rustc_data_structures::sync::MetadataRef;
  11 use rustc_middle::middle::cstore::{EncodedMetadata, MetadataLoader};
  12 use rustc_middle::ty::TyCtxt;
  13 use rustc_session::config;
  14 use rustc_target::spec::Target;
  15
  16 use crate::backend::WriteMetadata;
  17
  18 pub(crate) struct CraneliftMetadataLoader;
  19
  20 impl MetadataLoader for CraneliftMetadataLoader {
  21     fn get_rlib_metadata(&self, _target: &Target, path: &Path) -> Result<MetadataRef, String> {
  22         let mut archive = ar::Archive::new(File::open(path).map_err(|e| format!("{:?}", e))?);
  23         // Iterate over all entries in the archive:
  24         while let Some(entry_result) = archive.next_entry() {
  25             let mut entry = entry_result.map_err(|e| format!("{:?}", e))?;
  26             if entry.header().identifier() == METADATA_FILENAME.as_bytes() {
  27                 let mut buf = Vec::with_capacity(
  28                     usize::try_from(entry.header().size())
  29                         .expect("Rlib metadata file too big to load into memory."),
  30                 );
  31                 ::std::io::copy(&mut entry, &mut buf).map_err(|e| format!("{:?}", e))?;
  32                 let buf: OwningRef<Vec<u8>, [u8]> = OwningRef::new(buf);
  33                 return Ok(rustc_erase_owner!(buf.map_owner_box()));
  34             }
  35         }
  36
  37         Err("couldn't find metadata entry".to_string())
  38     }
  39
  40     fn get_dylib_metadata(&self, _target: &Target, path: &Path) -> Result<MetadataRef, String> {
  41         use object::{Object, ObjectSection};
  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_by_name(".rustc")
  46             .ok_or("no .rustc section")?
  47             .data()
  48             .map_err(|e| format!("failed to read .rustc section: {:?}", e))?
  49             .to_owned();
  50         let buf: OwningRef<Vec<u8>, [u8]> = OwningRef::new(buf);
  51         Ok(rustc_erase_owner!(buf.map_owner_box()))
  52     }
  53 }
  54
  55 // Adapted from https://github.com/rust-lang/rust/blob/da573206f87b5510de4b0ee1a9c044127e409bd3/src/librustc_codegen_llvm/base.rs#L47-L112
  56 pub(crate) fn write_metadata<P: WriteMetadata>(
  57     tcx: TyCtxt<'_>,
  58     product: &mut P,
  59 ) -> EncodedMetadata {
  60     use snap::write::FrameEncoder;
  61     use std::io::Write;
  62
  63     #[derive(PartialEq, Eq, PartialOrd, Ord)]
  64     enum MetadataKind {
  65         None,
  66         Uncompressed,
  67         Compressed,
  68     }
  69
  70     let kind = tcx
  71         .sess
  72         .crate_types()
  73         .iter()
  74         .map(|ty| match *ty {
  75             config::CrateType::Executable
  76             | config::CrateType::Staticlib
  77             | config::CrateType::Cdylib => MetadataKind::None,
  78
  79             config::CrateType::Rlib => MetadataKind::Uncompressed,
  80
  81             config::CrateType::Dylib | config::CrateType::ProcMacro => MetadataKind::Compressed,
  82         })
  83         .max()
  84         .unwrap_or(MetadataKind::None);
  85
  86     if kind == MetadataKind::None {
  87         return EncodedMetadata::new();
  88     }
  89
  90     let metadata = tcx.encode_metadata();
  91     if kind == MetadataKind::Uncompressed {
  92         return metadata;
  93     }
  94
  95     assert!(kind == MetadataKind::Compressed);
  96     let mut compressed = tcx.metadata_encoding_version();
  97     FrameEncoder::new(&mut compressed)
  98         .write_all(&metadata.raw_data)
  99         .unwrap();
 100
 101     product.add_rustc_section(
 102         rustc_middle::middle::exported_symbols::metadata_symbol_name(tcx),
 103         compressed,
 104         tcx.sess.target.is_like_osx,
 105     );
 106
 107     metadata
 108 }