Sunspec: share block reads across values on the same connection (#33011)

plugin/sunspec_client.go

@@ -0,0 +1,45 @@
+package plugin
+
+import (
+	"bytes"
+	"fmt"
+
+	"github.com/evcc-io/evcc/util/modbus"
+	gridx "github.com/grid-x/modbus"
+)
+
+// sunspecCachedClient dedups the holding register reads gosunspec issues on
+// behalf of all sunspec values sharing a model block within one poll cycle.
+type sunspecCachedClient struct {
+	gridx.Client
+	cache *modbus.Cache
+}
+
+// newSunspecCachedClient wraps client for use as gosunspec's modbus client.
+func newSunspecCachedClient(client gridx.Client) *sunspecCachedClient {
+	return &sunspecCachedClient{Client: client, cache: modbus.NewCache(modbusBlockTTL)}
+}
+
+func (c *sunspecCachedClient) ReadHoldingRegisters(address, quantity uint16) ([]byte, error) {
+	key := fmt.Sprintf("%d/%d", address, quantity)
+
+	b, _, err := c.cache.Fetch(key, func() ([]byte, error) {
+		return c.Client.ReadHoldingRegisters(address, quantity)
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	// callers unmarshal in place, hand out a copy of the shared payload
+	return bytes.Clone(b), nil
+}
+
+func (c *sunspecCachedClient) WriteSingleRegister(address, value uint16) ([]byte, error) {
+	defer c.cache.Clear()
+	return c.Client.WriteSingleRegister(address, value)
+}
+
+func (c *sunspecCachedClient) WriteMultipleRegisters(address, quantity uint16, value []byte) ([]byte, error) {
+	defer c.cache.Clear()
+	return c.Client.WriteMultipleRegisters(address, quantity, value)
+}