#
cargo/sources/registry/index/
mod.rs

    1//! Management of the index of a registry source.
    2//!
    3//! This module contains management of the index and various operations, such as
    4//! actually parsing the index, looking for crates, etc. This is intended to be
    5//! abstract over remote indices (downloaded via Git or HTTP) and local registry
    6//! indices (which are all just present on the filesystem).
    7//!
    8//! ## How the index works
    9//!
    10//! Here is a simple flow when loading a [`Summary`] (metadata) from the index:
    11//!
    12//! 1. A query is fired via [`RegistryIndex::query_inner`].
    13//! 2. Tries loading all summaries via [`RegistryIndex::load_summaries`], and
    14//!    under the hood calling [`Summaries::parse`] to parse an index file.
    15//!     1. If an on-disk index cache is present, loads it via
    16//!        [`Summaries::parse_cache`].
    17//!     2. Otherwise goes to the slower path [`RegistryData::load`] to get the
    18//!        specific index file.
    19//! 3. A [`Summary`] is now ready in callback `f` in [`RegistryIndex::query_inner`].
    20//!
    21//! To learn the rationale behind this multi-layer index metadata loading,
    22//! see [the documentation of the on-disk index cache](cache).
    23use crate::core::Dependency;
    24use crate::core::dependency::{Artifact, DepKind};
    25use crate::core::{PackageId, SourceId, Summary};
    26use crate::sources::registry::{LoadResponse, RegistryData};
    27use crate::util::IntoUrl;
    28use crate::util::interning::InternedString;
    29use crate::util::{CargoResult, Filesystem, GlobalContext, OptVersionReq, internal};
    30use cargo_util::registry::make_dep_path;
    31use cargo_util_schemas::index::{IndexPackage, RegistryDependency};
    32use cargo_util_schemas::manifest::RustVersion;
    33use semver::Version;
    34use serde::{Deserialize, Serialize};
    35use std::borrow::Cow;
    36use std::collections::BTreeMap;
    37use std::collections::HashMap;
    38use std::path::Path;
    39use std::str;
    40use std::task::{Poll, ready};
    41use tracing::info;
    42
    43mod cache;
    44use self::cache::CacheManager;
    45use self::cache::SummariesCache;
    46
    47/// The maximum schema version of the `v` field in the index this version of
    48/// cargo understands. See [`IndexPackage::v`] for the detail.
    49const INDEX_V_MAX: u32 = 2;
    50
    51/// Manager for handling the on-disk index.
    52///
    53/// Different kinds of registries store the index differently:
    54///
    55/// * [`LocalRegistry`] is a simple on-disk tree of files of the raw index.
    56/// * [`RemoteRegistry`] is stored as a raw git repository.
    57/// * [`HttpRegistry`] fills the on-disk index cache directly without keeping
    58///   any raw index.
    59///
    60/// These means of access are handled via the [`RegistryData`] trait abstraction.
    61/// This transparently handles caching of the index in a more efficient format.
    62///
    63/// [`LocalRegistry`]: super::local::LocalRegistry
    64/// [`RemoteRegistry`]: super::remote::RemoteRegistry
    65/// [`HttpRegistry`]: super::http_remote::HttpRegistry
    66pub struct RegistryIndex<'gctx> {
    67    source_id: SourceId,
    68    /// Root directory of the index for the registry.
    69    path: Filesystem,
    70    /// In-memory cache of summary data.
    71    ///
    72    /// This is keyed off the package name. The [`Summaries`] value handles
    73    /// loading the summary data. It keeps an optimized on-disk representation
    74    /// of the JSON files, which is created in an as-needed fashion. If it
    75    /// hasn't been cached already, it uses [`RegistryData::load`] to access
    76    /// to JSON files from the index, and the creates the optimized on-disk
    77    /// summary cache.
    78    summaries_cache: HashMap<InternedString, Summaries>,
    79    /// [`GlobalContext`] reference for convenience.
    80    gctx: &'gctx GlobalContext,
    81    /// Manager of on-disk caches.
    82    cache_manager: CacheManager<'gctx>,
    83}
    84
    85/// An internal cache of summaries for a particular package.
    86///
    87/// A list of summaries are loaded from disk via one of two methods:
    88///
    89/// 1. From raw registry index --- Primarily Cargo will parse the corresponding
    90///    file for a crate in the upstream crates.io registry. That's just a JSON
    91///    blob per line which we can parse, extract the version, and then store here.
    92///    See [`IndexPackage`] and [`IndexSummary::parse`].
    93///
    94/// 2. From on-disk index cache --- If Cargo has previously run, we'll have a
    95///    cached index of dependencies for the upstream index. This is a file that
    96///    Cargo maintains lazily on the local filesystem and is much faster to
    97///    parse since it doesn't involve parsing all of the JSON.
    98///    See [`SummariesCache`].
    99///
    100/// The outward-facing interface of this doesn't matter too much where it's
    101/// loaded from, but it's important when reading the implementation to note that
    102/// we try to parse as little as possible!
    103#[derive(Default)]
    104struct Summaries {
    105    /// A raw vector of uninterpreted bytes. This is what `Unparsed` start/end
    106    /// fields are indexes into. If a `Summaries` is loaded from the crates.io
    107    /// index then this field will be empty since nothing is `Unparsed`.
    108    raw_data: Vec<u8>,
    109
    110    /// All known versions of a crate, keyed from their `Version` to the
    111    /// possibly parsed or unparsed version of the full summary.
    112    versions: HashMap<Version, MaybeIndexSummary>,
    113}
    114
    115/// A lazily parsed [`IndexSummary`].
    116enum MaybeIndexSummary {
    117    /// A summary which has not been parsed, The `start` and `end` are pointers
    118    /// into [`Summaries::raw_data`] which this is an entry of.
    119    Unparsed { start: usize, end: usize },
    120
    121    /// An actually parsed summary.
    122    Parsed(IndexSummary),
    123}
    124
    125/// A parsed representation of a summary from the index. This is usually parsed
    126/// from a line from a raw index file, or a JSON blob from on-disk index cache.
    127///
    128/// In addition to a full [`Summary`], we have information on whether it is `yanked`.
    129#[derive(Clone, Debug)]
    130pub enum IndexSummary {
    131    /// Available for consideration
    132    Candidate(Summary),
    133    /// Yanked within its registry
    134    Yanked(Summary),
    135    /// Not available as we are offline and create is not downloaded yet
    136    Offline(Summary),
    137    /// From a newer schema version and is likely incomplete or inaccurate
    138    Unsupported(Summary, u32),
    139    /// An error was encountered despite being a supported schema version
    140    Invalid(Summary),
    141}
    142
    143impl IndexSummary {
    144    /// Extract the summary from any variant
    145    pub fn as_summary(&self) -> &Summary {
    146        match self {
    147            IndexSummary::Candidate(sum)
    148            | IndexSummary::Yanked(sum)
    149            | IndexSummary::Offline(sum)
    150            | IndexSummary::Unsupported(sum, _)
    151            | IndexSummary::Invalid(sum) => sum,
    152        }
    153    }
    154
    155    /// Extract the summary from any variant
    156    pub fn into_summary(self) -> Summary {
    157        match self {
    158            IndexSummary::Candidate(sum)
    159            | IndexSummary::Yanked(sum)
    160            | IndexSummary::Offline(sum)
    161            | IndexSummary::Unsupported(sum, _)
    162            | IndexSummary::Invalid(sum) => sum,
    163        }
    164    }
    165
    166    pub fn map_summary(self, f: impl Fn(Summary) -> Summary) -> Self {
    167        match self {
    168            IndexSummary::Candidate(s) => IndexSummary::Candidate(f(s)),
    169            IndexSummary::Yanked(s) => IndexSummary::Yanked(f(s)),
    170            IndexSummary::Offline(s) => IndexSummary::Offline(f(s)),
    171            IndexSummary::Unsupported(s, v) => IndexSummary::Unsupported(f(s), v.clone()),
    172            IndexSummary::Invalid(s) => IndexSummary::Invalid(f(s)),
    173        }
    174    }
    175
    176    /// Extract the package id from any variant
    177    pub fn package_id(&self) -> PackageId {
    178        self.as_summary().package_id()
    179    }
    180
    181    /// Returns `true` if the index summary is [`Yanked`].
    182    ///
    183    /// [`Yanked`]: IndexSummary::Yanked
    184    #[must_use]
    185    pub fn is_yanked(&self) -> bool {
    186        matches!(self, Self::Yanked(..))
    187    }
    188
    189    /// Returns `true` if the index summary is [`Offline`].
    190    ///
    191    /// [`Offline`]: IndexSummary::Offline
    192    #[must_use]
    193    pub fn is_offline(&self) -> bool {
    194        matches!(self, Self::Offline(..))
    195    }
    196}
    197
    198fn index_package_to_summary(pkg: &IndexPackage<'_>, source_id: SourceId) -> CargoResult<Summary> {
    199    // ****CAUTION**** Please be extremely careful with returning errors, see
    200    // `IndexSummary::parse` for details
    201    let pkgid = PackageId::new(pkg.name.as_ref().into(), pkg.vers.clone(), source_id);
    202    let deps = pkg
    203        .deps
    204        .iter()
    205        .map(|dep| registry_dependency_into_dep(dep.clone(), source_id))
    206        .collect::<CargoResult<Vec<_>>>()?;
    207    let mut features = pkg.features.clone();
    208    if let Some(features2) = pkg.features2.clone() {
    209        for (name, values) in features2 {
    210            features.entry(name).or_default().extend(values);
    211        }
    212    }
    213    let features = features
    214        .into_iter()
    215        .map(|(name, values)| (name.into(), values.into_iter().map(|v| v.into()).collect()))
    216        .collect::<BTreeMap<_, _>>();
    217    let links: Option<InternedString> = pkg.links.as_ref().map(|l| l.as_ref().into());
    218    let mut summary = Summary::new(pkgid, deps, &features, links, pkg.rust_version.clone())?;
    219    summary.set_checksum(pkg.cksum.clone());
    220    Ok(summary)
    221}
    222
    223#[derive(Deserialize, Serialize)]
    224struct IndexPackageMinimum<'a> {
    225    name: Cow<'a, str>,
    226    vers: Version,
    227}
    228
    229#[derive(Deserialize, Serialize, Default)]
    230struct IndexPackageRustVersion {
    231    rust_version: Option<RustVersion>,
    232}
    233
    234#[derive(Deserialize, Serialize, Default)]
    235struct IndexPackageV {
    236    v: Option<u32>,
    237}
    238
    239impl<'gctx> RegistryIndex<'gctx> {
    240    /// Creates an empty registry index at `path`.
    241    pub fn new(
    242        source_id: SourceId,
    243        path: &Filesystem,
    244        gctx: &'gctx GlobalContext,
    245    ) -> RegistryIndex<'gctx> {
    246        RegistryIndex {
    247            source_id,
    248            path: path.clone(),
    249            summaries_cache: HashMap::new(),
    250            gctx,
    251            cache_manager: CacheManager::new(path.join(".cache"), gctx),
    252        }
    253    }
    254
    255    /// Returns the hash listed for a specified `PackageId`. Primarily for
    256    /// checking the integrity of a downloaded package matching the checksum in
    257    /// the index file, aka [`IndexSummary`].
    258    pub fn hash(&mut self, pkg: PackageId, load: &mut dyn RegistryData) -> Poll<CargoResult<&str>> {
    259        let req = OptVersionReq::lock_to_exact(pkg.version());
    260        let summary = self.summaries(pkg.name(), &req, load)?;
    261        let summary = ready!(summary).next();
    262        Poll::Ready(Ok(summary
    263            .ok_or_else(|| internal(format!("no hash listed for {}", pkg)))?
    264            .as_summary()
    265            .checksum()
    266            .ok_or_else(|| internal(format!("no hash listed for {}", pkg)))?))
    267    }
    268
    269    /// Load a list of summaries for `name` package in this registry which
    270    /// match `req`.
    271    ///
    272    /// This function will semantically
    273    ///
    274    /// 1. parse the index file (either raw or cache),
    275    /// 2. match all versions,
    276    /// 3. and then return an iterator over all summaries which matched.
    277    ///
    278    /// Internally there's quite a few layer of caching to amortize this cost
    279    /// though since this method is called quite a lot on null builds in Cargo.
    280    fn summaries<'a, 'b>(
    281        &'a mut self,
    282        name: InternedString,
    283        req: &'b OptVersionReq,
    284        load: &mut dyn RegistryData,
    285    ) -> Poll<CargoResult<impl Iterator<Item = &'a IndexSummary> + 'b>>
    286    where
    287        'a: 'b,
    288    {
    289        let bindeps = self.gctx.cli_unstable().bindeps;
    290
    291        let source_id = self.source_id;
    292
    293        // First up parse what summaries we have available.
    294        let summaries = ready!(self.load_summaries(name, load)?);
    295
    296        // Iterate over our summaries, extract all relevant ones which match our
    297        // version requirement, and then parse all corresponding rows in the
    298        // registry. As a reminder this `summaries` method is called for each
    299        // entry in a lock file on every build, so we want to absolutely
    300        // minimize the amount of work being done here and parse as little as
    301        // necessary.
    302        let raw_data = &summaries.raw_data;
    303        Poll::Ready(Ok(summaries
    304            .versions
    305            .iter_mut()
    306            .filter_map(move |(k, v)| if req.matches(k) { Some(v) } else { None })
    307            .filter_map(move |maybe| {
    308                match maybe.parse(raw_data, source_id, bindeps) {
    309                    Ok(sum) => Some(sum),
    310                    Err(e) => {
    311                        info!("failed to parse `{}` registry package: {}", name, e);
    312                        None
    313                    }
    314                }
    315            })))
    316    }
    317
    318    /// Actually parses what summaries we have available.
    319    ///
    320    /// If Cargo has run previously, this tries in this order:
    321    ///
    322    /// 1. Returns from in-memory cache, aka [`RegistryIndex::summaries_cache`].
    323    /// 2. If missing, hands over to [`Summaries::parse`] to parse an index file.
    324    ///
    325    ///    The actual kind index file being parsed depends on which kind of
    326    ///    [`RegistryData`] the `load` argument is given. For example, a
    327    ///    Git-based [`RemoteRegistry`] will first try a on-disk index cache
    328    ///    file, and then try parsing registry raw index from Git repository.
    329    ///
    330    /// In effect, this is intended to be a quite cheap operation.
    331    ///
    332    /// [`RemoteRegistry`]: super::remote::RemoteRegistry
    333    fn load_summaries(
    334        &mut self,
    335        name: InternedString,
    336        load: &mut dyn RegistryData,
    337    ) -> Poll<CargoResult<&mut Summaries>> {
    338        // If we've previously loaded what versions are present for `name`, just
    339        // return that since our in-memory cache should still be valid.
    340        if self.summaries_cache.contains_key(&name) {
    341            return Poll::Ready(Ok(self.summaries_cache.get_mut(&name).unwrap()));
    342        }
    343
    344        // Prepare the `RegistryData` which will lazily initialize internal data
    345        // structures.
    346        load.prepare()?;
    347
    348        let root = load.assert_index_locked(&self.path);
    349        let summaries = ready!(Summaries::parse(
    350            root,
    351            &name,
    352            self.source_id,
    353            load,
    354            self.gctx.cli_unstable().bindeps,
    355            &self.cache_manager,
    356        ))?
    357        .unwrap_or_default();
    358        self.summaries_cache.insert(name, summaries);
    359        Poll::Ready(Ok(self.summaries_cache.get_mut(&name).unwrap()))
    360    }
    361
    362    /// Clears the in-memory summaries cache.
    363    pub fn clear_summaries_cache(&mut self) {
    364        self.summaries_cache.clear();
    365    }
    366
    367    /// Attempts to find the packages that match a `name` and a version `req`.
    368    ///
    369    /// This is primarily used by [`Source::query`](super::Source).
    370    pub fn query_inner(
    371        &mut self,
    372        name: InternedString,
    373        req: &OptVersionReq,
    374        load: &mut dyn RegistryData,
    375        f: &mut dyn FnMut(IndexSummary),
    376    ) -> Poll<CargoResult<()>> {
    377        if !self.gctx.network_allowed() {
    378            // This should only return `Poll::Ready(Ok(()))` if there is at least 1 match.
    379            //
    380            // If there are 0 matches it should fall through and try again with online.
    381            // This is necessary for dependencies that are not used (such as
    382            // target-cfg or optional), but are not downloaded. Normally the
    383            // build should succeed if they are not downloaded and not used,
    384            // but they still need to resolve. If they are actually needed
    385            // then cargo will fail to download and an error message
    386            // indicating that the required dependency is unavailable while
    387            // offline will be displayed.
    388            let mut called = false;
    389            let callback = &mut |s: IndexSummary| {
    390                if !s.is_offline() {
    391                    called = true;
    392                    f(s);
    393                }
    394            };
    395            ready!(self.query_inner_with_online(name, req, load, callback, false)?);
    396            if called {
    397                return Poll::Ready(Ok(()));
    398            }
    399        }
    400        self.query_inner_with_online(name, req, load, f, true)
    401    }
    402
    403    /// Inner implementation of [`Self::query_inner`]. Returns the number of
    404    /// summaries we've got.
    405    ///
    406    /// The `online` controls whether Cargo can access the network when needed.
    407    fn query_inner_with_online(
    408        &mut self,
    409        name: InternedString,
    410        req: &OptVersionReq,
    411        load: &mut dyn RegistryData,
    412        f: &mut dyn FnMut(IndexSummary),
    413        online: bool,
    414    ) -> Poll<CargoResult<()>> {
    415        ready!(self.summaries(name, &req, load))?
    416            // First filter summaries for `--offline`. If we're online then
    417            // everything is a candidate, otherwise if we're offline we're only
    418            // going to consider candidates which are actually present on disk.
    419            //
    420            // Note: This particular logic can cause problems with
    421            // optional dependencies when offline. If at least 1 version
    422            // of an optional dependency is downloaded, but that version
    423            // does not satisfy the requirements, then resolution will
    424            // fail. Unfortunately, whether or not something is optional
    425            // is not known here.
    426            .map(|s| {
    427                if online || load.is_crate_downloaded(s.package_id()) {
    428                    s.clone()
    429                } else {
    430                    IndexSummary::Offline(s.as_summary().clone())
    431                }
    432            })
    433            .for_each(f);
    434        Poll::Ready(Ok(()))
    435    }
    436
    437    /// Looks into the summaries to check if a package has been yanked.
    438    pub fn is_yanked(
    439        &mut self,
    440        pkg: PackageId,
    441        load: &mut dyn RegistryData,
    442    ) -> Poll<CargoResult<bool>> {
    443        let req = OptVersionReq::lock_to_exact(pkg.version());
    444        let found = ready!(self.summaries(pkg.name(), &req, load))?.any(|s| s.is_yanked());
    445        Poll::Ready(Ok(found))
    446    }
    447}
    448
    449impl Summaries {
    450    /// Parse out a [`Summaries`] instances from on-disk state.
    451    ///
    452    /// This will do the followings in order:
    453    ///
    454    /// 1. Attempt to prefer parsing a previous index cache file that already
    455    ///    exists from a previous invocation of Cargo (aka you're typing `cargo
    456    ///    build` again after typing it previously).
    457    /// 2. If parsing fails, or the cache isn't found or is invalid, we then
    458    ///    take a slower path which loads the full descriptor for `relative`
    459    ///    from the underlying index (aka libgit2 with crates.io, or from a
    460    ///    remote HTTP index) and then parse everything in there.
    461    ///
    462    /// * `root` --- this is the root argument passed to `load`
    463    /// * `name` --- the name of the package.
    464    /// * `source_id` --- the registry's `SourceId` used when parsing JSON blobs
    465    ///   to create summaries.
    466    /// * `load` --- the actual index implementation which may be very slow to
    467    ///   call. We avoid this if we can.
    468    /// * `bindeps` --- whether the `-Zbindeps` unstable flag is enabled
    469    pub fn parse(
    470        root: &Path,
    471        name: &str,
    472        source_id: SourceId,
    473        load: &mut dyn RegistryData,
    474        bindeps: bool,
    475        cache_manager: &CacheManager<'_>,
    476    ) -> Poll<CargoResult<Option<Summaries>>> {
    477        // This is the file we're loading from cache or the index data.
    478        // See module comment in `registry/mod.rs` for why this is structured the way it is.
    479        let lowered_name = &name.to_lowercase();
    480        let relative = make_dep_path(&lowered_name, false);
    481
    482        let mut cached_summaries = None;
    483        let mut index_version = None;
    484        if let Some(contents) = cache_manager.get(lowered_name) {
    485            match Summaries::parse_cache(contents) {
    486                Ok((s, v)) => {
    487                    cached_summaries = Some(s);
    488                    index_version = Some(v);
    489                }
    490                Err(e) => {
    491                    tracing::debug!("failed to parse {lowered_name:?} cache: {e}");
    492                }
    493            }
    494        }
    495
    496        let response = ready!(load.load(root, relative.as_ref(), index_version.as_deref())?);
    497
    498        match response {
    499            LoadResponse::CacheValid => {
    500                tracing::debug!("fast path for registry cache of {:?}", relative);
    501                return Poll::Ready(Ok(cached_summaries));
    502            }
    503            LoadResponse::NotFound => {
    504                cache_manager.invalidate(lowered_name);
    505                return Poll::Ready(Ok(None));
    506            }
    507            LoadResponse::Data {
    508                raw_data,
    509                index_version,
    510            } => {
    511                // This is the fallback path where we actually talk to the registry backend to load
    512                // information. Here we parse every single line in the index (as we need
    513                // to find the versions)
    514                tracing::debug!("slow path for {:?}", relative);
    515                let mut cache = SummariesCache::default();
    516                let mut ret = Summaries::default();
    517                ret.raw_data = raw_data;
    518                for line in split(&ret.raw_data, b'\n') {
    519                    // Attempt forwards-compatibility on the index by ignoring
    520                    // everything that we ourselves don't understand, that should
    521                    // allow future cargo implementations to break the
    522                    // interpretation of each line here and older cargo will simply
    523                    // ignore the new lines.
    524                    let summary = match IndexSummary::parse(line, source_id, bindeps) {
    525                        Ok(summary) => summary,
    526                        Err(e) => {
    527                            // This should only happen when there is an index
    528                            // entry from a future version of cargo that this
    529                            // version doesn't understand. Hopefully, those future
    530                            // versions of cargo correctly set INDEX_V_MAX and
    531                            // CURRENT_CACHE_VERSION, otherwise this will skip
    532                            // entries in the cache preventing those newer
    533                            // versions from reading them (that is, until the
    534                            // cache is rebuilt).
    535                            tracing::info!(
    536                                "failed to parse {:?} registry package: {}",
    537                                relative,
    538                                e
    539                            );
    540                            continue;
    541                        }
    542                    };
    543                    let version = summary.package_id().version().clone();
    544                    cache.versions.push((version.clone(), line));
    545                    ret.versions.insert(version, summary.into());
    546                }
    547                if let Some(index_version) = index_version {
    548                    tracing::trace!("caching index_version {}", index_version);
    549                    let cache_bytes = cache.serialize(index_version.as_str());
    550                    // Once we have our `cache_bytes` which represents the `Summaries` we're
    551                    // about to return, write that back out to disk so future Cargo
    552                    // invocations can use it.
    553                    cache_manager.put(lowered_name, &cache_bytes);
    554
    555                    // If we've got debug assertions enabled read back in the cached values
    556                    // and assert they match the expected result.
    557                    #[cfg(debug_assertions)]
    558                    {
    559                        let readback = SummariesCache::parse(&cache_bytes)
    560                            .expect("failed to parse cache we just wrote");
    561                        assert_eq!(
    562                            readback.index_version, index_version,
    563                            "index_version mismatch"
    564                        );
    565                        assert_eq!(readback.versions, cache.versions, "versions mismatch");
    566                    }
    567                }
    568                Poll::Ready(Ok(Some(ret)))
    569            }
    570        }
    571    }
    572
    573    /// Parses the contents of an on-disk cache, aka [`SummariesCache`], which
    574    /// represents information previously cached by Cargo.
    575    pub fn parse_cache(contents: Vec<u8>) -> CargoResult<(Summaries, InternedString)> {
    576        let cache = SummariesCache::parse(&contents)?;
    577        let index_version = cache.index_version.into();
    578        let mut ret = Summaries::default();
    579        for (version, summary) in cache.versions {
    580            let (start, end) = subslice_bounds(&contents, summary);
    581            ret.versions
    582                .insert(version, MaybeIndexSummary::Unparsed { start, end });
    583        }
    584        ret.raw_data = contents;
    585        return Ok((ret, index_version));
    586
    587        // Returns the start/end offsets of `inner` with `outer`. Asserts that
    588        // `inner` is a subslice of `outer`.
    589        fn subslice_bounds(outer: &[u8], inner: &[u8]) -> (usize, usize) {
    590            let outer_start = outer.as_ptr() as usize;
    591            let outer_end = outer_start + outer.len();
    592            let inner_start = inner.as_ptr() as usize;
    593            let inner_end = inner_start + inner.len();
    594            assert!(inner_start >= outer_start);
    595            assert!(inner_end <= outer_end);
    596            (inner_start - outer_start, inner_end - outer_start)
    597        }
    598    }
    599}
    600
    601impl MaybeIndexSummary {
    602    /// Parses this "maybe a summary" into a `Parsed` for sure variant.
    603    ///
    604    /// Does nothing if this is already `Parsed`, and otherwise the `raw_data`
    605    /// passed in is sliced with the bounds in `Unparsed` and then actually
    606    /// parsed.
    607    fn parse(
    608        &mut self,
    609        raw_data: &[u8],
    610        source_id: SourceId,
    611        bindeps: bool,
    612    ) -> CargoResult<&IndexSummary> {
    613        let (start, end) = match self {
    614            MaybeIndexSummary::Unparsed { start, end } => (*start, *end),
    615            MaybeIndexSummary::Parsed(summary) => return Ok(summary),
    616        };
    617        let summary = IndexSummary::parse(&raw_data[start..end], source_id, bindeps)?;
    618        *self = MaybeIndexSummary::Parsed(summary);
    619        match self {
    620            MaybeIndexSummary::Unparsed { .. } => unreachable!(),
    621            MaybeIndexSummary::Parsed(summary) => Ok(summary),
    622        }
    623    }
    624}
    625
    626impl From<IndexSummary> for MaybeIndexSummary {
    627    fn from(summary: IndexSummary) -> MaybeIndexSummary {
    628        MaybeIndexSummary::Parsed(summary)
    629    }
    630}
    631
    632impl IndexSummary {
    633    /// Parses a line from the registry's index file into an [`IndexSummary`]
    634    /// for a package.
    635    ///
    636    /// The `line` provided is expected to be valid JSON. It is supposed to be
    637    /// a [`IndexPackage`].
    638    fn parse(line: &[u8], source_id: SourceId, bindeps: bool) -> CargoResult<IndexSummary> {
    639        // ****CAUTION**** Please be extremely careful with returning errors
    640        // from this function. Entries that error are not included in the
    641        // index cache, and can cause cargo to get confused when switching
    642        // between different versions that understand the index differently.
    643        // Make sure to consider the INDEX_V_MAX and CURRENT_CACHE_VERSION
    644        // values carefully when making changes here.
    645        let index_summary = (|| {
    646            let index = serde_json::from_slice::<IndexPackage<'_>>(line)?;
    647            let summary = index_package_to_summary(&index, source_id)?;
    648            Ok((index, summary))
    649        })();
    650        let (index, summary, valid) = match index_summary {
    651            Ok((index, summary)) => (index, summary, true),
    652            Err(err) => {
    653                let Ok(IndexPackageMinimum { name, vers }) =
    654                    serde_json::from_slice::<IndexPackageMinimum<'_>>(line)
    655                else {
    656                    // If we can't recover, prefer the original error
    657                    return Err(err);
    658                };
    659                tracing::info!(
    660                    "recoverying from failed parse of registry package {name}@{vers}: {err}"
    661                );
    662                let IndexPackageRustVersion { rust_version } =
    663                    serde_json::from_slice::<IndexPackageRustVersion>(line).unwrap_or_default();
    664                let IndexPackageV { v } =
    665                    serde_json::from_slice::<IndexPackageV>(line).unwrap_or_default();
    666                let index = IndexPackage {
    667                    name,
    668                    vers,
    669                    rust_version,
    670                    v,
    671                    deps: Default::default(),
    672                    features: Default::default(),
    673                    features2: Default::default(),
    674                    cksum: Default::default(),
    675                    yanked: Default::default(),
    676                    links: Default::default(),
    677                };
    678                let summary = index_package_to_summary(&index, source_id)?;
    679                (index, summary, false)
    680            }
    681        };
    682        let v = index.v.unwrap_or(1);
    683        tracing::trace!("json parsed registry {}/{}", index.name, index.vers);
    684
    685        let v_max = if bindeps {
    686            INDEX_V_MAX + 1
    687        } else {
    688            INDEX_V_MAX
    689        };
    690
    691        if v_max < v {
    692            Ok(IndexSummary::Unsupported(summary, v))
    693        } else if !valid {
    694            Ok(IndexSummary::Invalid(summary))
    695        } else if index.yanked.unwrap_or(false) {
    696            Ok(IndexSummary::Yanked(summary))
    697        } else {
    698            Ok(IndexSummary::Candidate(summary))
    699        }
    700    }
    701}
    702
    703/// Converts an encoded dependency in the registry to a cargo dependency
    704fn registry_dependency_into_dep(
    705    dep: RegistryDependency<'_>,
    706    default: SourceId,
    707) -> CargoResult<Dependency> {
    708    let RegistryDependency {
    709        name,
    710        req,
    711        mut features,
    712        optional,
    713        default_features,
    714        target,
    715        kind,
    716        registry,
    717        package,
    718        public,
    719        artifact,
    720        bindep_target,
    721        lib,
    722    } = dep;
    723
    724    let id = if let Some(registry) = &registry {
    725        SourceId::for_registry(&registry.into_url()?)?
    726    } else {
    727        default
    728    };
    729
    730    let interned_name = InternedString::new(package.as_ref().unwrap_or(&name));
    731    let mut dep = Dependency::parse(interned_name, Some(&req), id)?;
    732    if package.is_some() {
    733        dep.set_explicit_name_in_toml(name);
    734    }
    735    let kind = match kind.as_deref().unwrap_or("") {
    736        "dev" => DepKind::Development,
    737        "build" => DepKind::Build,
    738        _ => DepKind::Normal,
    739    };
    740
    741    let platform = match target {
    742        Some(target) => Some(target.parse()?),
    743        None => None,
    744    };
    745
    746    // All dependencies are private by default
    747    let public = public.unwrap_or(false);
    748
    749    // Unfortunately older versions of cargo and/or the registry ended up
    750    // publishing lots of entries where the features array contained the
    751    // empty feature, "", inside. This confuses the resolution process much
    752    // later on and these features aren't actually valid, so filter them all
    753    // out here.
    754    features.retain(|s| !s.is_empty());
    755
    756    // In index, "registry" is null if it is from the same index.
    757    // In Cargo.toml, "registry" is None if it is from the default
    758    if !id.is_crates_io() {
    759        dep.set_registry_id(id);
    760    }
    761
    762    if let Some(artifacts) = artifact {
    763        let artifact = Artifact::parse(&artifacts, lib, bindep_target.as_deref())?;
    764        dep.set_artifact(artifact);
    765    }
    766
    767    dep.set_optional(optional)
    768        .set_default_features(default_features)
    769        .set_features(features)
    770        .set_platform(platform)
    771        .set_kind(kind)
    772        .set_public(public);
    773
    774    Ok(dep)
    775}
    776
    777/// Like [`slice::split`] but is optimized by [`memchr`].
    778fn split(haystack: &[u8], needle: u8) -> impl Iterator<Item = &[u8]> {
    779    struct Split<'a> {
    780        haystack: &'a [u8],
    781        needle: u8,
    782    }
    783
    784    impl<'a> Iterator for Split<'a> {
    785        type Item = &'a [u8];
    786
    787        fn next(&mut self) -> Option<&'a [u8]> {
    788            if self.haystack.is_empty() {
    789                return None;
    790            }
    791            let (ret, remaining) = match memchr::memchr(self.needle, self.haystack) {
    792                Some(pos) => (&self.haystack[..pos], &self.haystack[pos + 1..]),
    793                None => (self.haystack, &[][..]),
    794            };
    795            self.haystack = remaining;
    796            Some(ret)
    797        }
    798    }
    799
    800    Split { haystack, needle }
    801}