tor_persist/
lib.rs

1#![cfg_attr(docsrs, feature(doc_cfg))]
2#![doc = include_str!("../README.md")]
3// @@ begin lint list maintained by maint/add_warning @@
4#![allow(renamed_and_removed_lints)] // @@REMOVE_WHEN(ci_arti_stable)
5#![allow(unknown_lints)] // @@REMOVE_WHEN(ci_arti_nightly)
6#![warn(missing_docs)]
7#![warn(noop_method_call)]
8#![warn(unreachable_pub)]
9#![warn(clippy::all)]
10#![deny(clippy::await_holding_lock)]
11#![deny(clippy::cargo_common_metadata)]
12#![deny(clippy::cast_lossless)]
13#![deny(clippy::checked_conversions)]
14#![warn(clippy::cognitive_complexity)]
15#![deny(clippy::debug_assert_with_mut_call)]
16#![deny(clippy::exhaustive_enums)]
17#![deny(clippy::exhaustive_structs)]
18#![deny(clippy::expl_impl_clone_on_copy)]
19#![deny(clippy::fallible_impl_from)]
20#![deny(clippy::implicit_clone)]
21#![deny(clippy::large_stack_arrays)]
22#![warn(clippy::manual_ok_or)]
23#![deny(clippy::missing_docs_in_private_items)]
24#![warn(clippy::needless_borrow)]
25#![warn(clippy::needless_pass_by_value)]
26#![warn(clippy::option_option)]
27#![deny(clippy::print_stderr)]
28#![deny(clippy::print_stdout)]
29#![warn(clippy::rc_buffer)]
30#![deny(clippy::ref_option_ref)]
31#![warn(clippy::semicolon_if_nothing_returned)]
32#![warn(clippy::trait_duplication_in_bounds)]
33#![deny(clippy::unchecked_time_subtraction)]
34#![deny(clippy::unnecessary_wraps)]
35#![warn(clippy::unseparated_literal_suffix)]
36#![deny(clippy::unwrap_used)]
37#![deny(clippy::mod_module_files)]
38#![allow(clippy::let_unit_value)] // This can reasonably be done for explicitness
39#![allow(clippy::uninlined_format_args)]
40#![allow(clippy::significant_drop_in_scrutinee)] // arti/-/merge_requests/588/#note_2812945
41#![allow(clippy::result_large_err)] // temporary workaround for arti#587
42#![allow(clippy::needless_raw_string_hashes)] // complained-about code is fine, often best
43#![allow(clippy::needless_lifetimes)] // See arti#1765
44#![allow(mismatched_lifetime_syntaxes)] // temporary workaround for arti#2060
45#![allow(clippy::collapsible_if)] // See arti#2342
46#![deny(clippy::unused_async)]
47//! <!-- @@ end lint list maintained by maint/add_warning @@ -->
48
49// TODO #1645 (either remove this, or decide to have it everywhere)
50#![cfg_attr(not(all(feature = "experimental", feature = "full")), allow(unused))]
51
52mod err;
53#[cfg(not(target_arch = "wasm32"))]
54mod fs;
55mod fs_mistrust_error_ext;
56mod handle;
57pub mod hsnickname;
58mod load_store;
59pub mod slug;
60#[cfg(feature = "testing")]
61mod testing;
62
63#[cfg(feature = "state-dir")]
64pub mod state_dir;
65
66use serde::{Deserialize, Serialize, de::DeserializeOwned};
67use std::sync::Arc;
68
69/// Wrapper type for Results returned from this crate.
70type Result<T> = std::result::Result<T, crate::Error>;
71
72pub use err::{Error, ErrorSource};
73#[cfg(not(target_arch = "wasm32"))]
74pub use fs::FsStateMgr;
75pub use fs_mistrust_error_ext::FsMistrustErrorExt;
76pub use handle::{DynStorageHandle, StorageHandle};
77pub use serde_json::Value as JsonValue;
78#[cfg(feature = "testing")]
79pub use testing::TestingStateMgr;
80
81/// An object that can manage persistent state.
82///
83/// State is implemented as a simple key-value store, where the values
84/// are objects that can be serialized and deserialized.
85///
86/// # Warnings
87///
88/// Current implementations may place additional limits on the types
89/// of objects that can be stored.  This is not a great example of OO
90/// design: eventually we should probably clarify that more.
91pub trait StateMgr: Clone {
92    /// Try to load the object with key `key` from the store.
93    ///
94    /// Return None if no such object exists.
95    fn load<D>(&self, key: &str) -> Result<Option<D>>
96    where
97        D: DeserializeOwned;
98    /// Try to save `val` with key `key` in the store.
99    ///
100    /// Replaces any previous value associated with `key`.
101    fn store<S>(&self, key: &str, val: &S) -> Result<()>
102    where
103        S: Serialize;
104    /// Return true if this is a read-write state manager.
105    ///
106    /// If it returns false, then attempts to `store` will fail with
107    /// an error of kind [`BadApiUsage`](tor_error::ErrorKind::BadApiUsage)
108    fn can_store(&self) -> bool;
109
110    /// Try to become a read-write state manager if possible, without
111    /// blocking.
112    ///
113    /// This function will return an error only if something really
114    /// unexpected went wrong.  It may return `Ok(_)` even if we don't
115    /// acquire the lock: check the return value or call
116    /// `[StateMgr::can_store()`] to see if the lock is held.
117    fn try_lock(&self) -> Result<LockStatus>;
118
119    /// Release any locks held and become a read-only state manager
120    /// again. If no locks were held, do nothing.
121    fn unlock(&self) -> Result<()>;
122
123    /// Make a new [`StorageHandle`] to store values of particular type
124    /// at a particular key.
125    fn create_handle<T>(self, key: impl Into<String>) -> DynStorageHandle<T>
126    where
127        Self: Send + Sync + Sized + 'static,
128        T: Serialize + DeserializeOwned + 'static,
129    {
130        Arc::new(handle::StorageHandleImpl::new(self, key.into()))
131    }
132}
133
134/// A possible outcome from calling [`StateMgr::try_lock()`]
135#[allow(clippy::exhaustive_enums)]
136#[derive(Debug, Copy, Clone, Eq, PartialEq)]
137#[must_use]
138pub enum LockStatus {
139    /// We didn't have the lock and were unable to acquire it.
140    NoLock,
141    /// We already held the lock, and didn't have anything to do.
142    AlreadyHeld,
143    /// We successfully acquired the lock for the first time.
144    NewlyAcquired,
145}
146
147impl LockStatus {
148    /// Return true if this status indicates that we hold the lock.
149    pub fn held(&self) -> bool {
150        !matches!(self, LockStatus::NoLock)
151    }
152}
153
154/// A wrapper type for types whose representation may change in future versions of Arti.
155///
156/// This uses `#[serde(untagged)]` to attempt deserializing as a type `T` first, and falls back
157/// to a generic JSON value representation if that fails.
158#[derive(Clone, Serialize, Deserialize, Debug, PartialEq, Eq)]
159#[serde(untagged)]
160#[allow(clippy::exhaustive_enums)]
161pub enum Futureproof<T> {
162    /// A successfully-deserialized `T`.
163    Understandable(T),
164    /// A generic JSON value, representing a failure to deserialize a `T`.
165    Unknown(JsonValue),
166}
167
168impl<T> Futureproof<T> {
169    /// Convert the `Futureproof` into an `Option<T>`, throwing away an `Unknown` value.
170    pub fn into_option(self) -> Option<T> {
171        match self {
172            Futureproof::Understandable(x) => Some(x),
173            Futureproof::Unknown(_) => None,
174        }
175    }
176}
177
178impl<T> From<T> for Futureproof<T> {
179    fn from(inner: T) -> Self {
180        Self::Understandable(inner)
181    }
182}
tor_persist/lib.rs

tor_persist/
lib.rs
