aranya_runtime/storage/
mod.rs

1//! Interfaces for graph storage.
2//!
3//! The [`StorageProvider`] and [`Storage`] interfaces enable high-level
4//! actions on the graph. Traversing the graph is made simpler by splitting
5//! its [`Command`]s into [`Segment`]s. Updating the graph is possible using
6//! [`Perspective`]s, which represent a slice of state.
7
8use alloc::{boxed::Box, string::String, vec::Vec};
9use core::{fmt, ops::Deref};
10
11use buggy::{Bug, BugExt};
12use serde::{Deserialize, Serialize};
13
14use crate::{Address, Command, CommandId, PolicyId, Prior};
15
16pub mod linear;
17pub mod memory;
18
19/// The maximum size of a serialized message
20pub const MAX_COMMAND_LENGTH: usize = 2048;
21
22aranya_crypto::custom_id! {
23    /// The ID of the graph, taken from initialization.
24    pub struct GraphId;
25}
26
27#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize)]
28pub struct Location {
29    pub segment: usize,
30    pub command: usize,
31}
32
33impl From<(usize, usize)> for Location {
34    fn from((segment, command): (usize, usize)) -> Self {
35        Self::new(segment, command)
36    }
37}
38
39impl AsRef<Location> for Location {
40    fn as_ref(&self) -> &Location {
41        self
42    }
43}
44
45impl Location {
46    pub fn new(segment: usize, command: usize) -> Location {
47        Location { segment, command }
48    }
49
50    /// If this is not the first command in a segment, return a location
51    /// pointing to the previous command.
52    #[must_use]
53    pub fn previous(mut self) -> Option<Self> {
54        if let Some(n) = usize::checked_sub(self.command, 1) {
55            self.command = n;
56            Some(self)
57        } else {
58            None
59        }
60    }
61
62    /// Returns true if other location is in the same segment.
63    pub fn same_segment(self, other: Location) -> bool {
64        self.segment == other.segment
65    }
66}
67
68impl fmt::Display for Location {
69    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
70        write!(f, "{}:{}", self.segment, self.command)
71    }
72}
73
74/// An error returned by [`Storage`] or [`StorageProvider`].
75#[derive(Debug, PartialEq, Eq, thiserror::Error)]
76pub enum StorageError {
77    #[error("storage already exists")]
78    StorageExists,
79    #[error("no such storage")]
80    NoSuchStorage,
81    #[error("segment index {} is out of bounds", .0.segment)]
82    SegmentOutOfBounds(Location),
83    #[error("command index {} is out of bounds in segment {}", .0.command, .0.segment)]
84    CommandOutOfBounds(Location),
85    #[error("IO error")]
86    IoError,
87    #[error("not a merge command")]
88    NotMerge,
89    #[error("command with id {0} not found")]
90    NoSuchId(CommandId),
91    #[error("policy mismatch")]
92    PolicyMismatch,
93    #[error("cannot write an empty perspective")]
94    EmptyPerspective,
95    #[error("segment must be a descendant of the head for commit")]
96    HeadNotAncestor,
97    #[error("command's parents do not match the perspective head")]
98    PerspectiveHeadMismatch,
99    #[error(transparent)]
100    Bug(#[from] Bug),
101}
102
103/// Handle to storage implementations used by the runtime.
104pub trait StorageProvider {
105    type Perspective: Perspective + Revertable;
106    type Segment: Segment;
107    type Storage: Storage<
108        Segment = Self::Segment,
109        Perspective = Self::Perspective,
110        FactIndex = <Self::Segment as Segment>::FactIndex,
111    >;
112
113    /// Create an unrooted perspective, intended for creating a new graph.
114    ///
115    /// # Arguments
116    ///
117    /// * `policy_id` - The policy to associate with the graph.
118    fn new_perspective(&mut self, policy_id: PolicyId) -> Self::Perspective;
119
120    /// Create a new graph.
121    ///
122    /// # Arguments
123    ///
124    /// * `graph` - ID of the graph, taken from the initialization command.
125    /// * `init` - Contains the data necessary to initialize the new graph.
126    fn new_storage(
127        &mut self,
128        init: Self::Perspective,
129    ) -> Result<(GraphId, &mut Self::Storage), StorageError>;
130
131    /// Get an existing graph.
132    ///
133    /// # Arguments
134    ///
135    /// * `graph` - ID of the graph, taken from the initialization command.
136    fn get_storage(&mut self, graph: GraphId) -> Result<&mut Self::Storage, StorageError>;
137
138    /// Gets a list of all stored graphs by their graph ID.
139    // TODO(nikki): rewrite this once we can use coroutines/generators?
140    fn list_graph_ids(
141        &mut self,
142    ) -> Result<impl Iterator<Item = Result<GraphId, StorageError>>, StorageError>;
143}
144
145/// Represents the runtime's graph; [`Command`]s in storage have been validated
146/// by an associated policy and committed to state.
147pub trait Storage {
148    type Perspective: Perspective + Revertable;
149    type FactPerspective: FactPerspective;
150    type Segment: Segment<FactIndex = Self::FactIndex>;
151    type FactIndex: FactIndex;
152
153    /// Returns the location of Command with id if it has been stored by
154    /// searching from the head.
155    fn get_location(&self, address: Address) -> Result<Option<Location>, StorageError> {
156        self.get_location_from(self.get_head()?, address)
157    }
158
159    /// Returns the location of Command with id by searching from the given location.
160    fn get_location_from(
161        &self,
162        start: Location,
163        address: Address,
164    ) -> Result<Option<Location>, StorageError> {
165        let mut queue = Vec::new();
166        queue.push(start);
167        'outer: while let Some(loc) = queue.pop() {
168            let head = self.get_segment(loc)?;
169            if address.max_cut > head.longest_max_cut()? {
170                continue;
171            }
172            if let Some(loc) = head.get_from_max_cut(address.max_cut)? {
173                let command = head.get_command(loc).assume("command must exist")?;
174                if command.id() == address.id {
175                    return Ok(Some(loc));
176                }
177            }
178            // Assumes skip list is sorted in ascending order.
179            // We always want to skip as close to the root as possible.
180            for (skip, max_cut) in head.skip_list() {
181                if max_cut >= &address.max_cut {
182                    queue.push(*skip);
183                    continue 'outer;
184                }
185            }
186            queue.extend(head.prior());
187        }
188        Ok(None)
189    }
190
191    /// Returns the CommandId of the command at the location.
192    fn get_command_id(&self, location: Location) -> Result<CommandId, StorageError>;
193
194    /// Returns a linear perspective at the given location.
195    fn get_linear_perspective(
196        &self,
197        parent: Location,
198    ) -> Result<Option<Self::Perspective>, StorageError>;
199
200    /// Returns a fact perspective at the given location, intended for evaluating braids.
201    /// The fact perspective will include the facts of the command at the given location.
202    fn get_fact_perspective(&self, first: Location) -> Result<Self::FactPerspective, StorageError>;
203
204    /// Returns a merge perspective based on the given locations with the braid as prior facts.
205    fn new_merge_perspective(
206        &self,
207        left: Location,
208        right: Location,
209        last_common_ancestor: (Location, usize),
210        policy_id: PolicyId,
211        braid: Self::FactIndex,
212    ) -> Result<Option<Self::Perspective>, StorageError>;
213
214    /// Returns the segment at the given location.
215    fn get_segment(&self, location: Location) -> Result<Self::Segment, StorageError>;
216
217    /// Returns the head of the graph.
218    fn get_head(&self) -> Result<Location, StorageError>;
219
220    /// Sets the given segment as the head of the graph.  Returns an error if
221    /// the current head is not an ancestor of the provided segment.
222    fn commit(&mut self, segment: Self::Segment) -> Result<(), StorageError>;
223
224    /// Writes the given perspective to a segment.
225    fn write(&mut self, perspective: Self::Perspective) -> Result<Self::Segment, StorageError>;
226
227    /// Writes the given fact perspective to a fact index.
228    fn write_facts(
229        &mut self,
230        fact_perspective: Self::FactPerspective,
231    ) -> Result<Self::FactIndex, StorageError>;
232
233    /// Determine whether the given location is an ancestor of the given segment.
234    fn is_ancestor(
235        &self,
236        search_location: Location,
237        segment: &Self::Segment,
238    ) -> Result<bool, StorageError> {
239        let mut queue = Vec::new();
240        queue.extend(segment.prior());
241        let segment = self.get_segment(search_location)?;
242        let address = segment
243            .get_command(search_location)
244            .assume("location must exist")?
245            .address()?;
246        'outer: while let Some(location) = queue.pop() {
247            if location.segment == search_location.segment
248                && location.command >= search_location.command
249            {
250                return Ok(true);
251            }
252            let segment = self.get_segment(location)?;
253            if address.max_cut > segment.longest_max_cut()? {
254                continue;
255            }
256            for (skip, max_cut) in segment.skip_list() {
257                if max_cut >= &address.max_cut {
258                    queue.push(*skip);
259                    continue 'outer;
260                }
261            }
262            queue.extend(segment.prior());
263        }
264        Ok(false)
265    }
266}
267
268type MaxCut = usize;
269
270/// A segment is a nonempty sequence of commands persisted to storage.
271///
272/// A segment can be one of three types. This might be encoded in a future version of the API.
273/// * init   - This segment is the first segment of the graph and begins with an init command.
274/// * linear - This segment has a single prior command and is simply a sequence of linear commands.
275/// * merge  - This segment merges two other segments and thus begins with a merge command.
276///            A merge segment has a braid as it's prior facts.
277///
278/// Each command past the first must have the parent of the previous command in the segment.
279pub trait Segment {
280    type FactIndex: FactIndex;
281    type Command<'a>: Command
282    where
283        Self: 'a;
284
285    /// Returns the head of the segment.
286    fn head(&self) -> Result<Self::Command<'_>, StorageError>;
287
288    /// Returns the first Command in the segment.
289    fn first(&self) -> Self::Command<'_>;
290
291    /// Returns the location of the head of the segment.
292    fn head_location(&self) -> Location;
293
294    /// Returns the location of the first command.
295    fn first_location(&self) -> Location;
296
297    /// Returns true if the segment contains the location.
298    fn contains(&self, location: Location) -> bool;
299
300    /// Returns the id for the policy used for this segment.
301    fn policy(&self) -> PolicyId;
302
303    /// Returns the prior segments for this segment.
304    fn prior(&self) -> Prior<Location>;
305
306    /// Returns the command at the given location.
307    fn get_command(&self, location: Location) -> Option<Self::Command<'_>>;
308
309    /// Returns the command with the given max cut from within this segment.
310    fn get_from_max_cut(&self, max_cut: usize) -> Result<Option<Location>, StorageError>;
311
312    /// Returns an iterator of commands starting at the given location.
313    fn get_from(&self, location: Location) -> Vec<Self::Command<'_>>;
314
315    /// Get the fact index associated with this segment.
316    fn facts(&self) -> Result<Self::FactIndex, StorageError>;
317
318    fn contains_any<I>(&self, locations: I) -> bool
319    where
320        I: IntoIterator,
321        I::Item: AsRef<Location>,
322    {
323        locations
324            .into_iter()
325            .any(|loc| self.contains(*loc.as_ref()))
326    }
327
328    /// The shortest max cut for this segment.
329    ///
330    /// This will always the max cut of the first command in the segment.
331    fn shortest_max_cut(&self) -> MaxCut;
332
333    /// The longest max cut for this segment.
334    ///
335    /// This will always be the max cut of the last command in the segment.
336    fn longest_max_cut(&self) -> Result<MaxCut, StorageError>;
337
338    /// The skip list is a series of locations that can be safely jumped to
339    /// when searching for a location. As long as the max cut of the location
340    /// you're jumping to is greater than or equal to the location you're
341    /// searching for you can jump to it and be guaranteed not to miss
342    /// the location you're searching for.
343    ///
344    /// For merge commands the last location in the skip list is the least
345    /// common ancestor.
346    fn skip_list(&self) -> &[(Location, MaxCut)];
347}
348
349/// An index of facts in storage.
350pub trait FactIndex: Query {}
351
352/// A perspective is essentially a mutable, in-memory version of a [`Segment`],
353/// with the same three types.
354pub trait Perspective: FactPerspective {
355    /// Returns the id for the policy used for this perspective.
356    fn policy(&self) -> PolicyId;
357
358    /// Adds the given command to the head of the perspective. The command's
359    /// parent must be the head of the perspective.
360    fn add_command(&mut self, command: &impl Command) -> Result<usize, StorageError>;
361
362    /// Returns true if the perspective contains a command with the given ID.
363    fn includes(&self, id: CommandId) -> bool;
364
365    /// Returns the head address in the perspective, if it exists
366    fn head_address(&self) -> Result<Prior<Address>, Bug>;
367}
368
369/// A fact perspective is essentially a mutable, in-memory version of a [`FactIndex`].
370pub trait FactPerspective: QueryMut {}
371
372/// A revertable perspective can make checkpoints and be reverted such that the
373/// state of the perspective matches that when the checkpoint was created.
374pub trait Revertable {
375    /// Create a checkpoint which can be used to revert the perspective.
376    fn checkpoint(&self) -> Checkpoint;
377
378    /// Revert the perspective to the state it was at when the checkpoint was created.
379    fn revert(&mut self, checkpoint: Checkpoint) -> Result<(), Bug>;
380}
381
382/// A checkpoint used to revert perspectives.
383pub struct Checkpoint {
384    /// An index interpreted by a given `Revertable` implementation to revert to a prior point.
385    pub index: usize,
386}
387
388/// Can be queried to look up facts.
389///
390/// Facts are labeled by a name, which are generally a bounded set of human-readable strings determined in advance.
391///
392/// Within a name, facts are an association of compound keys to values. The facts are keyed by a compound key
393/// `(k_1, k_2, ..., k_n)`, where each `k` is a sequence of bytes. The fact value is also a sequence of bytes.
394pub trait Query {
395    /// Look up a named fact by an exact match of the compound key.
396    fn query(&self, name: &str, keys: &[Box<[u8]>]) -> Result<Option<Box<[u8]>>, StorageError>;
397
398    /// Iterator for [`Query::query_prefix`].
399    type QueryIterator: Iterator<Item = Result<Fact, StorageError>>;
400
401    /// Look up all named facts that begin with the prefix of keys, in sorted key order.
402    ///
403    /// The `prefix` is a partial compound key `(k_1, k_2, ..., k_n)`, where each `k` is a sequence of bytes.
404    /// This returns all facts under the name with keys such that `prefix` is equal to a prefix of the fact's keys.
405    fn query_prefix(
406        &self,
407        name: &str,
408        prefix: &[Box<[u8]>],
409    ) -> Result<Self::QueryIterator, StorageError>;
410}
411
412/// A fact with a key and value.
413#[derive(Debug, PartialEq, Eq)]
414pub struct Fact {
415    /// The sequence of keys.
416    pub key: Keys,
417    /// The bytes of the value.
418    pub value: Box<[u8]>,
419}
420
421/// Can mutate facts by inserting and deleting them.
422///
423/// See [`Query`] for details on the nature of facts.
424pub trait QueryMut: Query {
425    /// Insert a fact labeled by a name, with a given compound key and a value.
426    ///
427    /// This fact can later be looked up by [`Query`] methods, using the name and keys.
428    fn insert(&mut self, name: String, keys: Keys, value: Box<[u8]>);
429
430    /// Delete any fact associated to the compound key, under the given name.
431    fn delete(&mut self, name: String, keys: Keys);
432}
433
434/// A sequence of byte-based keys, used for facts.
435#[derive(Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize)]
436pub struct Keys(Box<[Box<[u8]>]>);
437
438impl Deref for Keys {
439    type Target = [Box<[u8]>];
440    fn deref(&self) -> &[Box<[u8]>] {
441        self.0.as_ref()
442    }
443}
444
445impl AsRef<[Box<[u8]>]> for Keys {
446    fn as_ref(&self) -> &[Box<[u8]>] {
447        self.0.as_ref()
448    }
449}
450
451impl core::borrow::Borrow<[Box<[u8]>]> for Keys {
452    fn borrow(&self) -> &[Box<[u8]>] {
453        self.0.as_ref()
454    }
455}
456
457impl From<&[&[u8]]> for Keys {
458    fn from(value: &[&[u8]]) -> Self {
459        value.iter().copied().collect()
460    }
461}
462
463impl Keys {
464    fn starts_with(&self, prefix: &[Box<[u8]>]) -> bool {
465        self.as_ref().starts_with(prefix)
466    }
467}
468
469impl<B: Into<Box<[u8]>>> FromIterator<B> for Keys {
470    fn from_iter<T: IntoIterator<Item = B>>(iter: T) -> Self {
471        Self(iter.into_iter().map(Into::into).collect())
472    }
473}
474
475// TODO: Fix and enable
476// #[cfg(test)]
477// mod tests;
aranya_runtime/storage/mod.rs

aranya_runtime/storage/
mod.rs
