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//! A `Source` for registry-based packages.
//! # What's a Registry?
//! Registries are central locations where packages can be uploaded to,
//! discovered, and searched for. The purpose of a registry is to have a
//! location that serves as permanent storage for versions of a crate over time.
//! Compared to git sources, a registry provides many packages as well as many
//! versions simultaneously. Git sources can also have commits deleted through
//! rebasings where registries cannot have their versions deleted.
//! # The Index of a Registry
//! One of the major difficulties with a registry is that hosting so many
//! packages may quickly run into performance problems when dealing with
//! dependency graphs. It's infeasible for cargo to download the entire contents
//! of the registry just to resolve one package's dependencies, for example. As
//! a result, cargo needs some efficient method of querying what packages are
//! available on a registry, what versions are available, and what the
//! dependencies for each version is.
//! One method of doing so would be having the registry expose an HTTP endpoint
//! which can be queried with a list of packages and a response of their
//! dependencies and versions is returned. This is somewhat inefficient however
//! as we may have to hit the endpoint many times and we may have already
//! queried for much of the data locally already (for other packages, for
//! example). This also involves inventing a transport format between the
//! registry and Cargo itself, so this route was not taken.
//! Instead, Cargo communicates with registries through a git repository
//! referred to as the Index. The Index of a registry is essentially an easily
//! query-able version of the registry's database for a list of versions of a
//! package as well as a list of dependencies for each version.
//! Using git to host this index provides a number of benefits:
//! * The entire index can be stored efficiently locally on disk. This means
//! that all queries of a registry can happen locally and don't need to touch
//! the network.
//! * Updates of the index are quite efficient. Using git buys incremental
//! updates, compressed transmission, etc for free. The index must be updated
//! each time we need fresh information from a registry, but this is one
//! update of a git repository that probably hasn't changed a whole lot so
//! it shouldn't be too expensive.
//! Additionally, each modification to the index is just appending a line at
//! the end of a file (the exact format is described later). This means that
//! the commits for an index are quite small and easily applied/compressable.
//! ## The format of the Index
//! The index is a store for the list of versions for all packages known, so its
//! format on disk is optimized slightly to ensure that `ls registry` doesn't
//! produce a list of all packages ever known. The index also wants to ensure
//! that there's not a million files which may actually end up hitting
//! filesystem limits at some point. To this end, a few decisions were made
//! about the format of the registry:
//! 1. Each crate will have one file corresponding to it. Each version for a
//! crate will just be a line in this file.
//! 2. There will be two tiers of directories for crate names, under which
//! crates corresponding to those tiers will be located.
//! As an example, this is an example hierarchy of an index:
//! ```notrust
//! .
//! ├── 3
//! │   └── u
//! │   └── url
//! ├── bz
//! │   └── ip
//! │   └── bzip2
//! ├── config.json
//! ├── en
//! │   └── co
//! │   └── encoding
//! └── li
//!    ├── bg
//!    │   └── libgit2
//!    └── nk
//!    └── link-config
//! ```
//! The root of the index contains a `config.json` file with a few entries
//! corresponding to the registry (see `RegistryConfig` below).
//! Otherwise, there are three numbered directories (1, 2, 3) for crates with
//! names 1, 2, and 3 characters in length. The 1/2 directories simply have the
//! crate files underneath them, while the 3 directory is sharded by the first
//! letter of the crate name.
//! Otherwise the top-level directory contains many two-letter directory names,
//! each of which has many sub-folders with two letters. At the end of all these
//! are the actual crate files themselves.
//! The purpose of this layout is to hopefully cut down on `ls` sizes as well as
//! efficient lookup based on the crate name itself.
//! ## Crate files
//! Each file in the index is the history of one crate over time. Each line in
//! the file corresponds to one version of a crate, stored in JSON format (see
//! the `RegistryPackage` structure below).
//! As new versions are published, new lines are appended to this file. The only
//! modifications to this file that should happen over time are yanks of a
//! particular version.
//! # Downloading Packages
//! The purpose of the Index was to provide an efficient method to resolve the
//! dependency graph for a package. So far we only required one network
//! interaction to update the registry's repository (yay!). After resolution has
//! been performed, however we need to download the contents of packages so we
//! can read the full manifest and build the source code.
//! To accomplish this, this source's `download` method will make an HTTP
//! request per-package requested to download tarballs into a local cache. These
//! tarballs will then be unpacked into a destination folder.
//! Note that because versions uploaded to the registry are frozen forever that
//! the HTTP download and unpacking can all be skipped if the version has
//! already been downloaded and unpacked. This caching allows us to only
//! download a package when absolutely necessary.
//! # Filesystem Hierarchy
//! Overall, the `$HOME/.cargo` looks like this when talking about the registry:
//! ```notrust
//! # A folder under which all registry metadata is hosted (similar to
//! # $HOME/.cargo/git)
//! $HOME/.cargo/registry/
//! # For each registry that cargo knows about (keyed by hostname + hash)
//! # there is a folder which is the checked out version of the index for
//! # the registry in this location. Note that this is done so cargo can
//! # support multiple registries simultaneously
//! index/
//! registry1-<hash>/
//! registry2-<hash>/
//! ...
//! # This folder is a cache for all downloaded tarballs from a registry.
//! # Once downloaded and verified, a tarball never changes.
//! cache/
//! registry1-<hash>/<pkg>-<version>.crate
//! ...
//! # Location in which all tarballs are unpacked. Each tarball is known to
//! # be frozen after downloading, so transitively this folder is also
//! # frozen once its unpacked (it's never unpacked again)
//! src/
//! registry1-<hash>/<pkg>-<version>/...
//! ...
//! ```
use std::borrow::Cow;
use std::collections::BTreeMap;
use std::fmt;
use std::fs::File;
use std::path::{Path, PathBuf};
use flate2::read::GzDecoder;
use semver::Version;
use serde::de;
use tar::Archive;
use core::{Package, PackageId, Registry, Source, SourceId, Summary};
use core::dependency::{Dependency, Kind};
use sources::PathSource;
use util::{internal, CargoResult, Config, FileLock, Filesystem};
use util::errors::CargoResultExt;
use util::hex;
use util::to_url::ToUrl;
const INDEX_LOCK: &str = ".cargo-index-lock";
pub const CRATES_IO: &str = "";
const CRATE_TEMPLATE: &str = "{crate}";
const VERSION_TEMPLATE: &str = "{version}";
pub struct RegistrySource<'cfg> {
source_id: SourceId,
src_path: Filesystem,
config: &'cfg Config,
updated: bool,
ops: Box<RegistryData + 'cfg>,
index: index::RegistryIndex<'cfg>,
index_locked: bool,
pub struct RegistryConfig {
/// Download endpoint for all crates.
/// The string is a template which will generate the download URL for the
/// tarball of a specific version of a crate. The substrings `{crate}` and
/// `{version}` will be replaced with the crate's name and version
/// respectively.
/// For backwards compatibility, if the string does not contain `{crate}` or
/// `{version}`, it will be extended with `/{crate}/{version}/download` to
/// support registries like which were crated before the
/// templating setup was created.
pub dl: String,
/// API endpoint for the registry. This is what's actually hit to perform
/// operations like yanks, owner modifications, publish new crates, etc.
pub api: Option<String>,
struct RegistryPackage<'a> {
name: Cow<'a, str>,
vers: Version,
deps: DependencyList,
features: BTreeMap<String, Vec<String>>,
cksum: String,
yanked: Option<bool>,
#[serde(default)] links: Option<String>,
struct DependencyList {
inner: Vec<Dependency>,
struct RegistryDependency<'a> {
name: Cow<'a, str>,
req: Cow<'a, str>,
features: Vec<String>,
optional: bool,
default_features: bool,
target: Option<Cow<'a, str>>,
kind: Option<Cow<'a, str>>,
registry: Option<String>,
pub trait RegistryData {
fn index_path(&self) -> &Filesystem;
fn load(
_root: &Path,
path: &Path,
data: &mut FnMut(&[u8]) -> CargoResult<()>,
) -> CargoResult<()>;
fn config(&mut self) -> CargoResult<Option<RegistryConfig>>;
fn update_index(&mut self) -> CargoResult<()>;
fn download(&mut self, pkg: &PackageId, checksum: &str) -> CargoResult<FileLock>;
fn is_crate_downloaded(&self, _pkg: &PackageId) -> bool {
mod index;
mod remote;
mod local;
fn short_name(id: &SourceId) -> String {
let hash = hex::short_hash(id);
let ident = id.url().host_str().unwrap_or("").to_string();
format!("{}-{}", ident, hash)
impl<'cfg> RegistrySource<'cfg> {
pub fn remote(source_id: &SourceId, config: &'cfg Config) -> RegistrySource<'cfg> {
let name = short_name(source_id);
let ops = remote::RemoteRegistry::new(source_id, config, &name);
RegistrySource::new(source_id, config, &name, Box::new(ops), true)
pub fn local(source_id: &SourceId, path: &Path, config: &'cfg Config) -> RegistrySource<'cfg> {
let name = short_name(source_id);
let ops = local::LocalRegistry::new(path, config, &name);
RegistrySource::new(source_id, config, &name, Box::new(ops), false)
fn new(
source_id: &SourceId,
config: &'cfg Config,
name: &str,
ops: Box<RegistryData + 'cfg>,
index_locked: bool,
) -> RegistrySource<'cfg> {
RegistrySource {
src_path: config.registry_source_path().join(name),
source_id: source_id.clone(),
updated: false,
index: index::RegistryIndex::new(source_id, ops.index_path(), config, index_locked),
/// Decode the configuration stored within the registry.
/// This requires that the index has been at least checked out.
pub fn config(&mut self) -> CargoResult<Option<RegistryConfig>> {
/// Unpacks a downloaded package into a location where it's ready to be
/// compiled.
/// No action is taken if the source looks like it's already unpacked.
fn unpack_package(&self, pkg: &PackageId, tarball: &FileLock) -> CargoResult<PathBuf> {
let dst = self.src_path
.join(&format!("{}-{}",, pkg.version()));
// Note that we've already got the `tarball` locked above, and that
// implies a lock on the unpacked destination as well, so this access
// via `into_path_unlocked` should be ok.
let dst = dst.into_path_unlocked();
let ok = dst.join(".cargo-ok");
if ok.exists() {
return Ok(dst);
let gz = GzDecoder::new(tarball.file());
let mut tar = Archive::new(gz);
let prefix = dst.file_name().unwrap();
let parent = dst.parent().unwrap();
for entry in tar.entries()? {
let mut entry = entry.chain_err(|| "failed to iterate over archive")?;
let entry_path = entry
.chain_err(|| "failed to read entry path")?
// We're going to unpack this tarball into the global source
// directory, but we want to make sure that it doesn't accidentally
// (or maliciously) overwrite source code from other crates. Cargo
// itself should never generate a tarball that hits this error, and
// should also block uploads with these sorts of tarballs,
// but be extra sure by adding a check here as well.
if !entry_path.starts_with(prefix) {
"invalid tarball downloaded, contains \
a file at {:?} which isn't under {:?}",
// Once that's verified, unpack the entry as usual.
.chain_err(|| format!("failed to unpack entry at `{}`", entry_path.display()))?;
fn do_update(&mut self) -> CargoResult<()> {
let path = self.ops.index_path();
self.index =
index::RegistryIndex::new(&self.source_id, path, self.config, self.index_locked);
impl<'cfg> Registry for RegistrySource<'cfg> {
fn query(&mut self, dep: &Dependency, f: &mut FnMut(Summary)) -> CargoResult<()> {
// If this is a precise dependency, then it came from a lockfile and in
// theory the registry is known to contain this version. If, however, we
// come back with no summaries, then our registry may need to be
// updated, so we fall back to performing a lazy update.
if dep.source_id().precise().is_some() && !self.updated {
let mut called = false;
self.index.query(dep, &mut *self.ops, &mut |s| {
called = true;
if called {
return Ok(());
} else {
self.index.query(dep, &mut *self.ops, f)
fn supports_checksums(&self) -> bool {
fn requires_precise(&self) -> bool {
impl<'cfg> Source for RegistrySource<'cfg> {
fn source_id(&self) -> &SourceId {
fn update(&mut self) -> CargoResult<()> {
// If we have an imprecise version then we don't know what we're going
// to look for, so we always attempt to perform an update here.
// If we have a precise version, then we'll update lazily during the
// querying phase. Note that precise in this case is only
// `Some("locked")` as other `Some` values indicate a `cargo update
// --precise` request
if self.source_id.precise() != Some("locked") {
fn download(&mut self, package: &PackageId) -> CargoResult<Package> {
let hash = self.index.hash(package, &mut *self.ops)?;
let path =, &hash)?;
let path = self.unpack_package(package, &path)
.chain_err(|| internal(format!("failed to unpack package `{}`", package)))?;
let mut src = PathSource::new(&path, &self.source_id, self.config);
let pkg =;
// Unfortunately the index and the actual Cargo.toml in the index can
// differ due to historical Cargo bugs. To paper over these we trash the
// *summary* loaded from the Cargo.toml we just downloaded with the one
// we loaded from the index.
let summaries = self.index.summaries(&*, &mut *self.ops)?;
let summary = summaries
.map(|s| &s.0)
.find(|s| s.package_id() == package)
.expect("summary not found");
let mut manifest = pkg.manifest().clone();
Ok(Package::new(manifest, pkg.manifest_path()))
fn fingerprint(&self, pkg: &Package) -> CargoResult<String> {
// TODO: this is pretty unfortunate, ideally we'd use `DeserializeSeed` which
// is intended for "deserializing with context" but that means we couldn't
// use `#[derive(Deserialize)]` on `RegistryPackage` unfortunately.
// I'm told, however, that will solve
// all our problems here. Until that lands this thread local is just a
// workaround in the meantime.
// If you're reading this and find this thread local funny, check to see if that
// PR is merged. If it is then let's ditch this thread local!
scoped_thread_local!(static DEFAULT_ID: SourceId);
impl<'de> de::Deserialize<'de> for DependencyList {
fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
D: de::Deserializer<'de>,
return deserializer.deserialize_seq(Visitor);
struct Visitor;
impl<'de> de::Visitor<'de> for Visitor {
type Value = DependencyList;
fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
write!(formatter, "a list of dependencies")
fn visit_seq<A>(self, mut seq: A) -> Result<DependencyList, A::Error>
A: de::SeqAccess<'de>,
let mut ret = Vec::new();
if let Some(size) = seq.size_hint() {
while let Some(element) = seq.next_element::<RegistryDependency>()? {
ret.push(parse_registry_dependency(element).map_err(|e| de::Error::custom(e))?);
Ok(DependencyList { inner: ret })
/// Converts an encoded dependency in the registry to a cargo dependency
fn parse_registry_dependency(dep: RegistryDependency) -> CargoResult<Dependency> {
let RegistryDependency {
mut features,
} = dep;
let id = if let Some(registry) = registry {
} else {
DEFAULT_ID.with(|id| id.clone())
let mut dep = Dependency::parse_no_deprecated(&name, Some(&req), &id)?;
let kind = match kind.as_ref().map(|s| &s[..]).unwrap_or("") {
"dev" => Kind::Development,
"build" => Kind::Build,
_ => Kind::Normal,
let platform = match target {
Some(target) => Some(target.parse()?),
None => None,
// Unfortunately older versions of cargo and/or the registry ended up
// publishing lots of entries where the features array contained the
// empty feature, "", inside. This confuses the resolution process much
// later on and these features aren't actually valid, so filter them all
// out here.
features.retain(|s| !s.is_empty());