wip: grib

internal/pkg/grib/cache.go

@@ -0,0 +1,40 @@
+package grib
+
+import (
+	"encoding/binary"
+	"math"
+	"sync"
+	"time"
+)
+
+type vec [2]float64
+
+type item struct {
+	v   vec
+	exp time.Time
+}
+
+type memCache struct {
+	ttl time.Duration
+	m   sync.Map
+}
+
+func (c *memCache) get(k uint64) (vec, bool) {
+	if v, ok := c.m.Load(k); ok {
+		it := v.(item)
+		if time.Now().Before(it.exp) {
+			return it.v, true
+		}
+		c.m.Delete(k)
+	}
+	return vec{}, false
+}
+
+func (c *memCache) set(k uint64, v vec) { c.m.Store(k, item{v, time.Now().Add(c.ttl)}) }
+
+func encodeVec(v vec) []byte {
+	var b [16]byte
+	binary.LittleEndian.PutUint64(b[:8], math.Float64bits(v[0]))
+	binary.LittleEndian.PutUint64(b[8:], math.Float64bits(v[1]))
+	return b[:]
+}