mirror of
https://github.com/restic/restic.git
synced 2024-12-28 10:49:02 +00:00
96 lines
2.1 KiB
Go
96 lines
2.1 KiB
Go
package bloblru
|
|
|
|
import (
|
|
"sync"
|
|
|
|
"github.com/restic/restic/internal/debug"
|
|
"github.com/restic/restic/internal/restic"
|
|
|
|
"github.com/hashicorp/golang-lru/simplelru"
|
|
)
|
|
|
|
// Crude estimate of the overhead per blob: a SHA-256, a linked list node
|
|
// and some pointers. See comment in Cache.add.
|
|
const overhead = len(restic.ID{}) + 64
|
|
|
|
// A Cache is a fixed-size LRU cache of blob contents.
|
|
// It is safe for concurrent access.
|
|
type Cache struct {
|
|
mu sync.Mutex
|
|
c *simplelru.LRU
|
|
|
|
free, size int // Current and max capacity, in bytes.
|
|
}
|
|
|
|
// New constructs a blob cache that stores at most size bytes worth of blobs.
|
|
func New(size int) *Cache {
|
|
c := &Cache{
|
|
free: size,
|
|
size: size,
|
|
}
|
|
|
|
// NewLRU wants us to specify some max. number of entries, else it errors.
|
|
// The actual maximum will be smaller than size/overhead, because we
|
|
// evict entries (RemoveOldest in add) to maintain our size bound.
|
|
maxEntries := size / overhead
|
|
lru, err := simplelru.NewLRU(maxEntries, c.evict)
|
|
if err != nil {
|
|
panic(err) // Can only be maxEntries <= 0.
|
|
}
|
|
c.c = lru
|
|
|
|
return c
|
|
}
|
|
|
|
// Add adds key id with value blob to c.
|
|
// It may return an evicted buffer for reuse.
|
|
func (c *Cache) Add(id restic.ID, blob []byte) (old []byte) {
|
|
debug.Log("bloblru.Cache: add %v", id)
|
|
|
|
size := cap(blob) + overhead
|
|
if size > c.size {
|
|
return
|
|
}
|
|
|
|
c.mu.Lock()
|
|
defer c.mu.Unlock()
|
|
|
|
var key interface{} = id
|
|
|
|
if c.c.Contains(key) { // Doesn't update the recency list.
|
|
return
|
|
}
|
|
|
|
// This loop takes at most min(maxEntries, maxchunksize/overhead)
|
|
// iterations.
|
|
for size > c.free {
|
|
_, val, _ := c.c.RemoveOldest()
|
|
b := val.([]byte)
|
|
if cap(b) > cap(old) {
|
|
// We can only return one buffer, so pick the largest.
|
|
old = b
|
|
}
|
|
}
|
|
|
|
c.c.Add(key, blob)
|
|
c.free -= size
|
|
|
|
return old
|
|
}
|
|
|
|
func (c *Cache) Get(id restic.ID) ([]byte, bool) {
|
|
c.mu.Lock()
|
|
value, ok := c.c.Get(id)
|
|
c.mu.Unlock()
|
|
|
|
debug.Log("bloblru.Cache: get %v, hit %v", id, ok)
|
|
|
|
blob, ok := value.([]byte)
|
|
return blob, ok
|
|
}
|
|
|
|
func (c *Cache) evict(key, value interface{}) {
|
|
blob := value.([]byte)
|
|
debug.Log("bloblru.Cache: evict %v, %d bytes", key, cap(blob))
|
|
c.free += cap(blob) + overhead
|
|
}
|