refactor: use the built-in max/min to simplify the code (ethereum#3110)

Author: carrychair

common/fdlimit/fdlimit_darwin.go

@@ -24,17 +24,14 @@ const hardlimit = 10240
 // Raise tries to maximize the file descriptor allowance of this process
 // to the maximum hard-limit allowed by the OS.
 // Returns the size it was set to (may differ from the desired 'max')
-func Raise(max uint64) (uint64, error) {
+func Raise(maxVal uint64) (uint64, error) {
 	// Get the current limit
 	var limit syscall.Rlimit
 	if err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &limit); err != nil {
 		return 0, err
 	}
 	// Try to update the limit to the max allowance
-	limit.Cur = limit.Max
-	if limit.Cur > max {
-		limit.Cur = max
-	}
+	limit.Cur = min(limit.Max, maxVal)
 	if err := syscall.Setrlimit(syscall.RLIMIT_NOFILE, &limit); err != nil {
 		return 0, err
 	}

p2p/dnsdisc/tree.go

@@ -202,10 +202,7 @@ func (t *Tree) build(entries []entry) entry {
 	}
 	var subtrees []entry
 	for len(entries) > 0 {
-		n := maxChildren
-		if len(entries) < n {
-			n = len(entries)
-		}
+		n := min(len(entries), maxChildren)
 		sub := t.build(entries[:n])
 		entries = entries[n:]
 		subtrees = append(subtrees, sub)

p2p/msgrate/msgrate.go

@@ -378,10 +378,7 @@ func (t *Trackers) TargetTimeout() time.Duration {
 // targetTimeout is the internal lockless version of TargetTimeout to be used
 // during QoS tuning.
 func (t *Trackers) targetTimeout() time.Duration {
-	timeout := time.Duration(ttlScaling * float64(t.roundtrip) / t.confidence)
-	if timeout > t.OverrideTTLLimit {
-		timeout = t.OverrideTTLLimit
-	}
+	timeout := min(time.Duration(ttlScaling*float64(t.roundtrip)/t.confidence), t.OverrideTTLLimit)
 	return timeout
 }
 

rlp/decode.go

@@ -314,10 +314,7 @@ func decodeSliceElems(s *Stream, val reflect.Value, elemdec decoder) error {
 	for ; ; i++ {
 		// grow slice if necessary
 		if i >= val.Cap() {
-			newcap := val.Cap() + val.Cap()/2
-			if newcap < 4 {
-				newcap = 4
-			}
+			newcap := max(val.Cap()+val.Cap()/2, 4)
 			newv := reflect.MakeSlice(val.Type(), val.Len(), newcap)
 			reflect.Copy(newv, val)
 			val.Set(newv)