Parsing optimisations

render/id.go

@@ -1,7 +1,6 @@
 package render
 
 import (
-	"net"
 	"strings"
 
 	"github.com/weaveworks/scope/probe/endpoint"
@@ -66,7 +65,9 @@ func externalNodeID(n report.Node, addr string, local report.Networks) (string,
 
 	// If the dstNodeAddr is not in a network local to this report, we emit an
 	// internet pseudoNode
-	if ip := net.ParseIP(addr); ip != nil && !local.Contains(ip) {
+	// Create a buffer on the stack of this function, so we don't need to allocate in ParseIP
+	var into [5]byte // one extra byte to save a memory allocation in critbitgo
+	if ip := report.ParseIP([]byte(addr), into[:4]); ip != nil && !local.Contains(ip) {
 		// emit one internet node for incoming, one for outgoing
 		if len(n.Adjacency) > 0 {
 			return IncomingInternetID, true

report/id.go

@@ -166,11 +166,11 @@ func makeSingleComponentID(tag string) func(string) string {
 // parseSingleComponentID makes a single-component node id decoder
 func parseSingleComponentID(tag string) func(string) (string, bool) {
 	return func(id string) (string, bool) {
-		fields := strings.SplitN(id, ScopeDelim, 2)
-		if len(fields) != 2 || fields[1] != "<"+tag+">" {
+		field0, field1, ok := split2(id, ScopeDelim)
+		if !ok || field1 != "<"+tag+">" {
 			return "", false
 		}
-		return fields[0], true
+		return field0, true
 	}
 }
 
@@ -197,48 +197,54 @@ func ParseOverlayNodeID(id string) (overlayPrefix string, peerName string) {
 	return WeaveOverlayPeerPrefix, id
 }
 
+// Split a string s into to parts separated by sep.
+func split2(s, sep string) (s1, s2 string, ok bool) {
+	// Not using strings.SplitN() to avoid a heap allocation
+	pos := strings.Index(s, sep)
+	if pos == -1 {
+		return "", "", false
+	}
+	return s[:pos], s[pos+1:], true
+}
+
 // ParseNodeID produces the host ID and remainder (typically an address) from
 // a node ID. Note that hostID may be blank.
 func ParseNodeID(nodeID string) (hostID string, remainder string, ok bool) {
-	fields := strings.SplitN(nodeID, ScopeDelim, 2)
-	if len(fields) != 2 {
-		return "", "", false
-	}
-	return fields[0], fields[1], true
+	return split2(nodeID, ScopeDelim)
 }
 
 // ParseEndpointNodeID produces the scope, address, and port and remainder.
-// Note that hostID may be blank.
+// Note that scope may be blank.
 func ParseEndpointNodeID(endpointNodeID string) (scope, address, port string, ok bool) {
-	fields := strings.SplitN(endpointNodeID, ScopeDelim, 3)
-	if len(fields) != 3 {
+	// Not using strings.SplitN() to avoid a heap allocation
+	first := strings.Index(endpointNodeID, ScopeDelim)
+	if first == -1 {
 		return "", "", "", false
 	}
-
-	return fields[0], fields[1], fields[2], true
+	second := strings.Index(endpointNodeID[first+1:], ScopeDelim)
+	if second == -1 {
+		return "", "", "", false
+	}
+	return endpointNodeID[:first], endpointNodeID[first+1 : first+1+second], endpointNodeID[first+1+second+1:], true
 }
 
 // ParseAddressNodeID produces the host ID, address from an address node ID.
 func ParseAddressNodeID(addressNodeID string) (hostID, address string, ok bool) {
-	fields := strings.SplitN(addressNodeID, ScopeDelim, 2)
-	if len(fields) != 2 {
-		return "", "", false
-	}
-	return fields[0], fields[1], true
+	return split2(addressNodeID, ScopeDelim)
 }
 
 // ParseECSServiceNodeID produces the cluster, service name from an ECS Service node ID
 func ParseECSServiceNodeID(ecsServiceNodeID string) (cluster, serviceName string, ok bool) {
-	fields := strings.SplitN(ecsServiceNodeID, ScopeDelim, 2)
-	if len(fields) != 2 {
+	cluster, serviceName, ok = split2(ecsServiceNodeID, ScopeDelim)
+	if !ok {
 		return "", "", false
 	}
 	// In previous versions, ECS Service node IDs were of form serviceName + "<ecs_service>".
 	// For backwards compatibility, we should still return a sensical serviceName for these cases.
-	if fields[1] == "<ecs_service>" {
-		return "unknown", fields[0], true
+	if serviceName == "<ecs_service>" {
+		return "unknown", cluster, true
 	}
-	return fields[0], fields[1], true
+	return cluster, serviceName, true
 }
 
 // ExtractHostID extracts the host id from Node

report/networks.go

@@ -140,3 +140,70 @@ func commonIPv4PrefixLen(a, b net.IP) int {
 	}
 	return cpl
 }
+
+// ParseIP parses s as an IP address into a byte slice if supplied, returning the result.
+// (mostly copied from net.ParseIP, modified to save memory allocations)
+func ParseIP(s []byte, into []byte) net.IP {
+	for i := 0; i < len(s); i++ {
+		switch s[i] {
+		case '.':
+			return parseIPv4(s, into)
+		case ':':
+			return net.ParseIP(string(s)) // leave IPv6 to the original code since we don't see many of those
+		}
+	}
+	return nil
+}
+
+// Parse IPv4 address (d.d.d.d).
+// (mostly copied from net.parseIPv4, modified to save memory allocations)
+func parseIPv4(s []byte, into []byte) net.IP {
+	var p []byte
+	if len(into) >= net.IPv4len { // check if we can use the supplied slice
+		p = into[:net.IPv4len]
+	} else {
+		p = make([]byte, net.IPv4len)
+	}
+	for i := 0; i < net.IPv4len; i++ {
+		if len(s) == 0 {
+			// Missing octets.
+			return nil
+		}
+		if i > 0 {
+			if s[0] != '.' {
+				return nil
+			}
+			s = s[1:]
+		}
+		n, c, ok := dtoi(s)
+		if !ok || n > 0xFF {
+			return nil
+		}
+		s = s[c:]
+		p[i] = byte(n)
+	}
+	if len(s) != 0 {
+		return nil
+	}
+	return p
+}
+
+// Bigger than we need, not too big to worry about overflow
+const big = 0xFFFFFF
+
+// Decimal to integer.
+// Returns number, characters consumed, success.
+// (completely copied from net.dtoi, just because it wasn't exported)
+func dtoi(s []byte) (n int, i int, ok bool) {
+	n = 0
+	for i = 0; i < len(s) && '0' <= s[i] && s[i] <= '9'; i++ {
+		n = n*10 + int(s[i]-'0')
+		if n >= big {
+			return big, i, false
+		}
+	}
+	if i == 0 {
+		return 0, 0, false
+	}
+	return n, i, true
+}