rustc_codegen_ssa/back/
rmeta_link.rs

1//! Late-metadata archive member that lists which rlib entries are Rust object files,
2//! and potentially other data collected and used when building or linking a rlib.
3//! See <https://github.com/rust-lang/rust/issues/138243>.
4
5use std::path::{Path, PathBuf};
6
7use object::read::archive::ArchiveFile;
8use rustc_data_structures::fx::FxHashMap;
9use rustc_serialize::opaque::mem_encoder::MemEncoder;
10use rustc_serialize::opaque::{MAGIC_END_BYTES, MemDecoder};
11use rustc_serialize::{Decodable, Encodable};
12
13use super::metadata::search_for_section;
14
15pub(crate) const FILENAME: &str = "lib.rmeta-link";
16pub(crate) const SECTION: &str = ".rmeta-link";
17
18pub struct RmetaLink {
19    pub rust_object_files: Vec<String>,
20}
21
22impl RmetaLink {
23    pub(crate) fn encode(&self) -> Vec<u8> {
24        let mut encoder = MemEncoder::new();
25        self.rust_object_files.encode(&mut encoder);
26        let mut data = encoder.finish();
27        data.extend_from_slice(MAGIC_END_BYTES);
28        data
29    }
30
31    pub(crate) fn decode(data: &[u8]) -> Option<RmetaLink> {
32        let mut decoder = MemDecoder::new(data, 0).ok()?;
33        let rust_object_files = Vec::<String>::decode(&mut decoder);
34        Some(RmetaLink { rust_object_files })
35    }
36}
37
38/// Reads the link-time metadata from an already-parsed archive.
39pub fn read(archive: &ArchiveFile<'_>, archive_data: &[u8], rlib_path: &Path) -> Option<RmetaLink> {
40    for entry in archive.members() {
41        let entry = entry.ok()?;
42        if entry.name() == FILENAME.as_bytes() {
43            let data = entry.data(archive_data).ok()?;
44            let section_data = search_for_section(rlib_path, data, SECTION).ok()?;
45            return RmetaLink::decode(section_data);
46        }
47    }
48    None
49}
50
51/// Like [`read`], but parses the archive from raw bytes.
52///
53/// Use this when the caller's `ArchiveFile` comes from a different version of the `object` crate.
54pub fn read_from_data(archive_data: &[u8], rlib_path: &Path) -> Option<RmetaLink> {
55    let archive = ArchiveFile::parse(archive_data).ok()?;
56    read(&archive, archive_data, rlib_path)
57}
58
59#[derive(#[automatically_derived]
impl ::core::default::Default for RmetaLinkCache {
    #[inline]
    fn default() -> RmetaLinkCache {
        RmetaLinkCache { cache: ::core::default::Default::default() }
    }
}Default)]
60pub struct RmetaLinkCache {
61    cache: FxHashMap<PathBuf, Option<RmetaLink>>,
62}
63
64impl RmetaLinkCache {
65    pub fn get_or_insert_with(
66        &mut self,
67        rlib_path: &Path,
68        load: impl FnOnce() -> Option<RmetaLink>,
69    ) -> Option<&RmetaLink> {
70        self.cache.entry(rlib_path.to_path_buf()).or_insert_with(load).as_ref()
71    }
72}
rustc_codegen_ssa/back/rmeta_link.rs

rustc_codegen_ssa/back/
rmeta_link.rs
