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authorn-peugnet <n.peugnet@free.fr>2021-09-08 18:54:11 +0200
committern-peugnet <n.peugnet@free.fr>2021-09-08 18:54:11 +0200
commit66cb179e0c751c081fbb9ec769a409a7a8115459 (patch)
tree2c3dbdace7f8a36f22b66de5ba929d7f2b5d9da4 /cache
parent31432f931012a6cb3ee2c153127e6669a4dbb959 (diff)
downloaddna-backup-66cb179e0c751c081fbb9ec769a409a7a8115459.tar.gz
dna-backup-66cb179e0c751c081fbb9ec769a409a7a8115459.zip
add cache and start using it in repo
Diffstat (limited to 'cache')
-rw-r--r--cache/cache.go58
-rw-r--r--cache/cache_test.go80
2 files changed, 138 insertions, 0 deletions
diff --git a/cache/cache.go b/cache/cache.go
new file mode 100644
index 0000000..ff2c279
--- /dev/null
+++ b/cache/cache.go
@@ -0,0 +1,58 @@
+package cache
+
+import "sync"
+
+type Cacher interface {
+ Get(key interface{}) (value []byte, exists bool)
+ Set(key interface{}, value []byte)
+ Len() int
+}
+
+type FifoCache struct {
+ head, tail *fifoCacheEntry
+ data map[interface{}][]byte
+ capacity int
+ mutex sync.RWMutex
+}
+
+type fifoCacheEntry struct {
+ Key interface{}
+ Next *fifoCacheEntry
+}
+
+func NewFifoCache(capacity int) *FifoCache {
+ return &FifoCache{data: make(map[interface{}][]byte, capacity), capacity: capacity}
+}
+
+func (c *FifoCache) Get(key interface{}) (value []byte, exists bool) {
+ c.mutex.RLock()
+ defer c.mutex.RUnlock()
+ value, exists = c.data[key]
+ return
+}
+
+func (c *FifoCache) Set(key interface{}, value []byte) {
+ c.mutex.Lock()
+ defer c.mutex.Unlock()
+ if len(c.data) == c.capacity {
+ // Evict first entry
+ evicted := c.head
+ c.head = evicted.Next
+ delete(c.data, evicted.Key)
+ }
+ entry := &fifoCacheEntry{Key: key}
+ if c.head == nil {
+ c.head = entry
+ }
+ if c.tail == nil {
+ c.tail = entry
+ } else {
+ c.tail.Next = entry
+ c.tail = entry
+ }
+ c.data[key] = value
+}
+
+func (c *FifoCache) Len() int {
+ return len(c.data)
+}
diff --git a/cache/cache_test.go b/cache/cache_test.go
new file mode 100644
index 0000000..6b84b79
--- /dev/null
+++ b/cache/cache_test.go
@@ -0,0 +1,80 @@
+package cache
+
+import (
+ "bytes"
+ "testing"
+)
+
+func TestFifoChunkCache(t *testing.T) {
+ var v []byte
+ var e bool
+ var cache Cacher = NewFifoCache(3)
+ k0 := 0
+ k1 := 1
+ k2 := 2
+ k3 := 3
+ v0 := []byte{'0'}
+ v1 := []byte{'1'}
+ v2 := []byte{'2'}
+ v3 := []byte{'3'}
+
+ if cache.Len() != 0 {
+ t.Fatal("Cache should be of size 0")
+ }
+
+ v, e = cache.Get(k0)
+ if e {
+ t.Fatal("There should not be any value")
+ }
+
+ cache.Set(k0, v0)
+ cache.Set(k1, v1)
+ cache.Set(k2, v2)
+
+ if cache.Len() != 3 {
+ t.Fatal("Cache should be of size 3")
+ }
+
+ v, e = cache.Get(k0)
+ if !e {
+ t.Fatal("Value should exist for k0")
+ }
+ if bytes.Compare(v, v0) != 0 {
+ t.Fatal("Value for k0 does not match")
+ }
+
+ cache.Set(k3, v3)
+
+ if cache.Len() != 3 {
+ t.Fatal("Cache should still be of size 3")
+ }
+
+ v, e = cache.Get(k0)
+ if e {
+ t.Fatal("Value should not exist for k0")
+ }
+
+ v, e = cache.Get(k1)
+ if !e {
+ t.Fatal("Value should exist for k1")
+ }
+ if bytes.Compare(v, v1) != 0 {
+ t.Fatal("Value for k1 does not match")
+ }
+
+ v, e = cache.Get(k2)
+ if !e {
+ t.Fatal("Value should exist for k2")
+ }
+ if bytes.Compare(v, v2) != 0 {
+ t.Fatal("Value for k2 does not match")
+ }
+
+ v, e = cache.Get(k3)
+ if !e {
+ t.Fatal("Value should exist for k3")
+ }
+ if bytes.Compare(v, v3) != 0 {
+ t.Fatal("Value for k3 does not match")
+ }
+}