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//! Reading and writing of the rustc metadata for rlibs and dylibs
use std::fs::File;
use std::path::Path;
use rustc_codegen_ssa::METADATA_FILENAME;
use rustc_data_structures::memmap::Mmap;
use rustc_data_structures::owning_ref::OwningRef;
use rustc_data_structures::rustc_erase_owner;
use rustc_data_structures::sync::MetadataRef;
use rustc_middle::middle::cstore::MetadataLoader;
use rustc_middle::ty::TyCtxt;
use rustc_target::spec::Target;
use crate::backend::WriteMetadata;
/// The metadata loader used by cg_clif.
///
/// The metadata is stored in the same format as cg_llvm.
///
/// # Metadata location
///
/// <dl>
/// <dt>rlib</dt>
/// <dd>The metadata can be found in the `lib.rmeta` file inside of the ar archive.</dd>
/// <dt>dylib</dt>
/// <dd>The metadata can be found in the `.rustc` section of the shared library.</dd>
/// </dl>
pub(crate) struct CraneliftMetadataLoader;
fn load_metadata_with(
path: &Path,
f: impl for<'a> FnOnce(&'a [u8]) -> Result<&'a [u8], String>,
) -> Result<MetadataRef, String> {
let file = File::open(path).map_err(|e| format!("{:?}", e))?;
let data = unsafe { Mmap::map(file) }.map_err(|e| format!("{:?}", e))?;
let metadata = OwningRef::new(data).try_map(f)?;
return Ok(rustc_erase_owner!(metadata.map_owner_box()));
}
impl MetadataLoader for CraneliftMetadataLoader {
fn get_rlib_metadata(&self, _target: &Target, path: &Path) -> Result<MetadataRef, String> {
load_metadata_with(path, |data| {
let archive = object::read::archive::ArchiveFile::parse(&*data)
.map_err(|e| format!("{:?}", e))?;
for entry_result in archive.members() {
let entry = entry_result.map_err(|e| format!("{:?}", e))?;
if entry.name() == METADATA_FILENAME.as_bytes() {
return Ok(entry.data());
}
}
Err("couldn't find metadata entry".to_string())
})
}
fn get_dylib_metadata(&self, _target: &Target, path: &Path) -> Result<MetadataRef, String> {
use object::{Object, ObjectSection};
load_metadata_with(path, |data| {
let file = object::File::parse(&data).map_err(|e| format!("parse: {:?}", e))?;
file.section_by_name(".rustc")
.ok_or("no .rustc section")?
.data()
.map_err(|e| format!("failed to read .rustc section: {:?}", e))
})
}
}
// Adapted from https://github.com/rust-lang/rust/blob/da573206f87b5510de4b0ee1a9c044127e409bd3/src/librustc_codegen_llvm/base.rs#L47-L112
pub(crate) fn write_metadata<O: WriteMetadata>(tcx: TyCtxt<'_>, object: &mut O) {
use snap::write::FrameEncoder;
use std::io::Write;
let metadata = tcx.encode_metadata();
let mut compressed = tcx.metadata_encoding_version();
FrameEncoder::new(&mut compressed).write_all(&metadata.raw_data).unwrap();
object.add_rustc_section(
rustc_middle::middle::exported_symbols::metadata_symbol_name(tcx),
compressed,
);
}
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