gix_pack/cache/
object.rs

1//! This module is a bit 'misplaced' if spelled out like '`gix_pack::cache::object::`*' but is best placed here for code reuse and
2//! general usefulness.
3use crate::cache;
4
5#[cfg(feature = "object-cache-dynamic")]
6mod memory {
7    use crate::{cache, cache::set_vec_to_slice};
8    use clru::WeightScale;
9    use std::num::NonZeroUsize;
10
11    struct Entry {
12        data: Vec<u8>,
13        kind: gix_object::Kind,
14    }
15
16    type Key = gix_hash::ObjectId;
17
18    struct CustomScale;
19
20    impl WeightScale<Key, Entry> for CustomScale {
21        fn weight(&self, key: &Key, value: &Entry) -> usize {
22            value.data.len() + std::mem::size_of::<Entry>() + key.as_bytes().len()
23        }
24    }
25
26    /// An LRU cache with hash map backing and an eviction rule based on the memory usage for object data in bytes.
27    pub struct MemoryCappedHashmap {
28        inner: clru::CLruCache<Key, Entry, gix_hashtable::hash::Builder, CustomScale>,
29        free_list: Vec<Vec<u8>>,
30        debug: gix_features::cache::Debug,
31    }
32
33    impl MemoryCappedHashmap {
34        /// The amount of bytes we can hold in total, or the value we saw in `new(…)`.
35        pub fn capacity(&self) -> usize {
36            self.inner.capacity()
37        }
38        /// Return a new instance which evicts least recently used items if it uses more than `memory_cap_in_bytes`
39        /// object data.
40        pub fn new(memory_cap_in_bytes: usize) -> MemoryCappedHashmap {
41            MemoryCappedHashmap {
42                inner: clru::CLruCache::with_config(
43                    clru::CLruCacheConfig::new(NonZeroUsize::new(memory_cap_in_bytes).expect("non zero"))
44                        .with_hasher(gix_hashtable::hash::Builder)
45                        .with_scale(CustomScale),
46                ),
47                free_list: Vec::new(),
48                debug: gix_features::cache::Debug::new(format!("MemoryCappedObjectHashmap({memory_cap_in_bytes}B)")),
49            }
50        }
51    }
52
53    impl cache::Object for MemoryCappedHashmap {
54        /// Put the object going by `id` of `kind` with `data` into the cache.
55        fn put(&mut self, id: gix_hash::ObjectId, kind: gix_object::Kind, data: &[u8]) {
56            self.debug.put();
57            let Some(data) = set_vec_to_slice(self.free_list.pop().unwrap_or_default(), data) else {
58                return;
59            };
60            let res = self.inner.put_with_weight(id, Entry { data, kind });
61            match res {
62                Ok(Some(previous_entry)) => self.free_list.push(previous_entry.data),
63                Ok(None) => {}
64                Err((_key, value)) => self.free_list.push(value.data),
65            }
66        }
67
68        /// Try to retrieve the object named `id` and place its data into `out` if available and return `Some(kind)` if found.
69        fn get(&mut self, id: &gix_hash::ObjectId, out: &mut Vec<u8>) -> Option<gix_object::Kind> {
70            let res = self.inner.get(id).and_then(|e| {
71                set_vec_to_slice(out, &e.data)?;
72                Some(e.kind)
73            });
74            if res.is_some() {
75                self.debug.hit();
76            } else {
77                self.debug.miss();
78            }
79            res
80        }
81    }
82}
83#[cfg(feature = "object-cache-dynamic")]
84pub use memory::MemoryCappedHashmap;
85
86/// A cache implementation that doesn't do any caching.
87pub struct Never;
88
89impl cache::Object for Never {
90    /// Noop
91    fn put(&mut self, _id: gix_hash::ObjectId, _kind: gix_object::Kind, _data: &[u8]) {}
92
93    /// Noop
94    fn get(&mut self, _id: &gix_hash::ObjectId, _out: &mut Vec<u8>) -> Option<gix_object::Kind> {
95        None
96    }
97}
98
99impl<T: cache::Object + ?Sized> cache::Object for Box<T> {
100    fn put(&mut self, id: gix_hash::ObjectId, kind: gix_object::Kind, data: &[u8]) {
101        use std::ops::DerefMut;
102        self.deref_mut().put(id, kind, data);
103    }
104
105    fn get(&mut self, id: &gix_hash::ObjectId, out: &mut Vec<u8>) -> Option<gix_object::Kind> {
106        use std::ops::DerefMut;
107        self.deref_mut().get(id, out)
108    }
109}
gix_pack/cache/object.rs

gix_pack/cache/
object.rs
