accounts/abi/bind: parse ABI only once, create metadata struct (#22583)

accounts/abi/bind/base.go

@@ -21,6 +21,8 @@ import (
 	"errors"
 	"fmt"
 	"math/big"
+	"strings"
+	"sync"
 
 	"github.com/ethereum/go-ethereum"
 	"github.com/ethereum/go-ethereum/accounts/abi"
@@ -76,6 +78,29 @@ type WatchOpts struct {
 	Context context.Context // Network context to support cancellation and timeouts (nil = no timeout)
 }
 
+// MetaData collects all metadata for a bound contract.
+type MetaData struct {
+	mu   sync.Mutex
+	Sigs map[string]string
+	Bin  string
+	ABI  string
+	ab   *abi.ABI
+}
+
+func (m *MetaData) GetAbi() (*abi.ABI, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	if m.ab != nil {
+		return m.ab, nil
+	}
+	if parsed, err := abi.JSON(strings.NewReader(m.ABI)); err != nil {
+		return nil, err
+	} else {
+		m.ab = &parsed
+	}
+	return m.ab, nil
+}
+
 // BoundContract is the base wrapper object that reflects a contract on the
 // Ethereum network. It contains a collection of methods that are used by the
 // higher level contract bindings to operate.