fix panics on concurrent use (concurrent map writes)

dynssz.go

@@ -9,10 +9,13 @@ package dynssz
 import (
 	"fmt"
 	"reflect"
+	"sync"
 )
 
 type DynSsz struct {
+	fastsszCompatMutex sync.Mutex
 	fastsszCompatCache map[reflect.Type]*fastsszCompatibility
+	typeSizeMutex      sync.RWMutex
 	typeSizeCache      map[reflect.Type]*cachedSszSize
 	specValues         map[string]any
 	specValueCache     map[string]*cachedSpecValue

fastssz.go

@@ -77,6 +77,9 @@ type fastsszCompatibility struct {
 //   that would prevent the use of fastssz for encoding or decoding.
 
 func (d *DynSsz) getFastsszCompatibility(targetType reflect.Type, sizeHints []sszSizeHint) (*fastsszCompatibility, error) {
+	d.fastsszCompatMutex.Lock()
+	defer d.fastsszCompatMutex.Unlock()
+
 	if cachedCompatibility := d.fastsszCompatCache[targetType]; cachedCompatibility != nil {
 		return cachedCompatibility, nil
 	}

sszsize.go

@@ -53,9 +53,12 @@ func (d *DynSsz) getSszSize(targetType reflect.Type, sizeHints []sszSizeHint) (i
 	}
 
 	// get size from cache if not influenced by a parent sizeHint
+	d.typeSizeMutex.RLock()
 	if cachedSize := d.typeSizeCache[targetType]; cachedSize != nil && len(sizeHints) == 0 {
+		d.typeSizeMutex.RUnlock()
 		return cachedSize.size, cachedSize.specval, nil
 	}
+	d.typeSizeMutex.RUnlock()
 
 	switch targetType.Kind() {
 	case reflect.Struct:
@@ -126,10 +129,12 @@ func (d *DynSsz) getSszSize(targetType reflect.Type, sizeHints []sszSizeHint) (i
 		staticSize = -1
 	} else if len(sizeHints) == 0 {
 		// cache size if it's static and not influenced by a parent sizeHint
+		d.typeSizeMutex.Lock()
 		d.typeSizeCache[targetType] = &cachedSszSize{
 			size:    staticSize,
 			specval: hasSpecValue,
 		}
+		d.typeSizeMutex.Unlock()
 	}
 
 	return staticSize, hasSpecValue, nil