linera_views/views/
hashable_wrapper.rs

1// Copyright (c) Zefchain Labs, Inc.
2// SPDX-License-Identifier: Apache-2.0
3
4use std::{
5    marker::PhantomData,
6    ops::{Deref, DerefMut},
7    sync::Mutex,
8};
9
10use serde::{de::DeserializeOwned, Serialize};
11
12use crate::{
13    batch::Batch,
14    common::from_bytes_option,
15    context::Context,
16    store::ReadableKeyValueStore as _,
17    views::{ClonableView, HashableView, Hasher, ReplaceContext, View, ViewError, MIN_VIEW_TAG},
18};
19
20/// A hash for `ContainerView` and storing of the hash for memoization purposes
21#[derive(Debug)]
22pub struct WrappedHashableContainerView<C, W, O> {
23    _phantom: PhantomData<C>,
24    stored_hash: Option<O>,
25    hash: Mutex<Option<O>>,
26    inner: W,
27}
28
29/// Key tags to create the sub-keys of a `MapView` on top of the base key.
30#[repr(u8)]
31enum KeyTag {
32    /// Prefix for the indices of the view.
33    Inner = MIN_VIEW_TAG,
34    /// Prefix for the hash.
35    Hash,
36}
37
38impl<C, W, O, C2> ReplaceContext<C2> for WrappedHashableContainerView<C, W, O>
39where
40    W: HashableView<Hasher: Hasher<Output = O>, Context = C> + ReplaceContext<C2>,
41    <W as ReplaceContext<C2>>::Target: HashableView<Hasher: Hasher<Output = O>>,
42    O: Serialize + DeserializeOwned + Send + Sync + Copy + PartialEq,
43    C: Context,
44    C2: Context,
45{
46    type Target = WrappedHashableContainerView<C2, <W as ReplaceContext<C2>>::Target, O>;
47
48    async fn with_context(
49        &mut self,
50        ctx: impl FnOnce(&Self::Context) -> C2 + Clone,
51    ) -> Self::Target {
52        let hash = *self.hash.lock().unwrap();
53        WrappedHashableContainerView {
54            _phantom: PhantomData,
55            stored_hash: self.stored_hash,
56            hash: Mutex::new(hash),
57            inner: self.inner.with_context(ctx).await,
58        }
59    }
60}
61
62impl<W: HashableView, O> View for WrappedHashableContainerView<W::Context, W, O>
63where
64    W: HashableView<Hasher: Hasher<Output = O>>,
65    O: Serialize + DeserializeOwned + Send + Sync + Copy + PartialEq,
66{
67    const NUM_INIT_KEYS: usize = 1 + W::NUM_INIT_KEYS;
68
69    type Context = W::Context;
70
71    fn context(&self) -> &Self::Context {
72        self.inner.context()
73    }
74
75    fn pre_load(context: &Self::Context) -> Result<Vec<Vec<u8>>, ViewError> {
76        let mut v = vec![context.base_key().base_tag(KeyTag::Hash as u8)];
77        let base_key = context.base_key().base_tag(KeyTag::Inner as u8);
78        let context = context.clone_with_base_key(base_key);
79        v.extend(W::pre_load(&context)?);
80        Ok(v)
81    }
82
83    fn post_load(context: Self::Context, values: &[Option<Vec<u8>>]) -> Result<Self, ViewError> {
84        let hash = from_bytes_option(values.first().ok_or(ViewError::PostLoadValuesError)?)?;
85        let base_key = context.base_key().base_tag(KeyTag::Inner as u8);
86        let context = context.clone_with_base_key(base_key);
87        let inner = W::post_load(
88            context,
89            values.get(1..).ok_or(ViewError::PostLoadValuesError)?,
90        )?;
91        Ok(Self {
92            _phantom: PhantomData,
93            stored_hash: hash,
94            hash: Mutex::new(hash),
95            inner,
96        })
97    }
98
99    async fn load(context: Self::Context) -> Result<Self, ViewError> {
100        let keys = Self::pre_load(&context)?;
101        let values = context.store().read_multi_values_bytes(keys).await?;
102        Self::post_load(context, &values)
103    }
104
105    fn rollback(&mut self) {
106        self.inner.rollback();
107        *self.hash.get_mut().unwrap() = self.stored_hash;
108    }
109
110    async fn has_pending_changes(&self) -> bool {
111        if self.inner.has_pending_changes().await {
112            return true;
113        }
114        let hash = self.hash.lock().unwrap();
115        self.stored_hash != *hash
116    }
117
118    fn flush(&mut self, batch: &mut Batch) -> Result<bool, ViewError> {
119        let delete_view = self.inner.flush(batch)?;
120        let hash = self.hash.get_mut().unwrap();
121        if delete_view {
122            let mut key_prefix = self.inner.context().base_key().bytes.clone();
123            key_prefix.pop();
124            batch.delete_key_prefix(key_prefix);
125            self.stored_hash = None;
126            *hash = None;
127        } else if self.stored_hash != *hash {
128            let mut key = self.inner.context().base_key().bytes.clone();
129            let tag = key.last_mut().unwrap();
130            *tag = KeyTag::Hash as u8;
131            match hash {
132                None => batch.delete_key(key),
133                Some(hash) => batch.put_key_value(key, hash)?,
134            }
135            self.stored_hash = *hash;
136        }
137        Ok(delete_view)
138    }
139
140    fn clear(&mut self) {
141        self.inner.clear();
142        *self.hash.get_mut().unwrap() = None;
143    }
144}
145
146impl<W, O> ClonableView for WrappedHashableContainerView<W::Context, W, O>
147where
148    W: HashableView + ClonableView,
149    O: Serialize + DeserializeOwned + Send + Sync + Copy + PartialEq,
150    W::Hasher: Hasher<Output = O>,
151{
152    fn clone_unchecked(&mut self) -> Self {
153        WrappedHashableContainerView {
154            _phantom: PhantomData,
155            stored_hash: self.stored_hash,
156            hash: Mutex::new(*self.hash.get_mut().unwrap()),
157            inner: self.inner.clone_unchecked(),
158        }
159    }
160}
161
162impl<W, O> HashableView for WrappedHashableContainerView<W::Context, W, O>
163where
164    W: HashableView,
165    O: Serialize + DeserializeOwned + Send + Sync + Copy + PartialEq,
166    W::Hasher: Hasher<Output = O>,
167{
168    type Hasher = W::Hasher;
169
170    async fn hash_mut(&mut self) -> Result<<Self::Hasher as Hasher>::Output, ViewError> {
171        let hash = *self.hash.get_mut().unwrap();
172        match hash {
173            Some(hash) => Ok(hash),
174            None => {
175                let new_hash = self.inner.hash_mut().await?;
176                let hash = self.hash.get_mut().unwrap();
177                *hash = Some(new_hash);
178                Ok(new_hash)
179            }
180        }
181    }
182
183    async fn hash(&self) -> Result<<Self::Hasher as Hasher>::Output, ViewError> {
184        let hash = *self.hash.lock().unwrap();
185        match hash {
186            Some(hash) => Ok(hash),
187            None => {
188                let new_hash = self.inner.hash().await?;
189                let mut hash = self.hash.lock().unwrap();
190                *hash = Some(new_hash);
191                Ok(new_hash)
192            }
193        }
194    }
195}
196
197impl<C, W, O> Deref for WrappedHashableContainerView<C, W, O> {
198    type Target = W;
199
200    fn deref(&self) -> &W {
201        &self.inner
202    }
203}
204
205impl<C, W, O> DerefMut for WrappedHashableContainerView<C, W, O> {
206    fn deref_mut(&mut self) -> &mut W {
207        *self.hash.get_mut().unwrap() = None;
208        &mut self.inner
209    }
210}
211
212#[cfg(with_graphql)]
213mod graphql {
214    use std::borrow::Cow;
215
216    use super::WrappedHashableContainerView;
217    use crate::context::Context;
218
219    impl<C, W, O> async_graphql::OutputType for WrappedHashableContainerView<C, W, O>
220    where
221        C: Context,
222        W: async_graphql::OutputType + Send + Sync,
223        O: Send + Sync,
224    {
225        fn type_name() -> Cow<'static, str> {
226            W::type_name()
227        }
228
229        fn qualified_type_name() -> String {
230            W::qualified_type_name()
231        }
232
233        fn create_type_info(registry: &mut async_graphql::registry::Registry) -> String {
234            W::create_type_info(registry)
235        }
236
237        async fn resolve(
238            &self,
239            ctx: &async_graphql::ContextSelectionSet<'_>,
240            field: &async_graphql::Positioned<async_graphql::parser::types::Field>,
241        ) -> async_graphql::ServerResult<async_graphql::Value> {
242            (**self).resolve(ctx, field).await
243        }
244    }
245}
linera_views/views/hashable_wrapper.rs

linera_views/views/
hashable_wrapper.rs
