Performance improvement for cn ip search.

The mask len for cn route bigger than 8, we can use the first byte as the key.

Author: j67678

cnipdata.go

@@ -3,6 +3,12 @@ package main
 var CNIPDataStart []uint32
 var CNIPDataNum []uint
 
+//data range by first byte
+var CNIPDataRange [256]struct {
+	start int
+	end   int
+}
+
 func initCNIPData() {
 	CNIPDataStart = []uint32{
 		16777472,
@@ -9738,4 +9744,19 @@ func initCNIPData() {
 		512,
 	}
 
+	n := len(CNIPDataStart)
+	var curr uint32 = 0
+	var preFirstByte uint32 = 0
+	for i := 0; i < n; i++ {
+		firstByte := CNIPDataStart[i] >> 24
+		if curr != firstByte {
+			curr = firstByte
+			if preFirstByte != 0 {
+				CNIPDataRange[preFirstByte].end = i - 1
+			}
+			CNIPDataRange[firstByte].start = i
+			preFirstByte = firstByte
+		}
+	}
+	CNIPDataRange[preFirstByte].end = n - 1
 }

directip.go

@@ -1,9 +1,5 @@
 package main
 
-import (
-	"sort"
-)
-
 func ipShouldDirect(ip string) (direct bool) {
 	direct = false
 	defer func() {
@@ -22,7 +18,11 @@ func ipShouldDirect(ip string) (direct bool) {
 	if ipLong == 0 {
 		return true
 	}
-	ipIndex := sort.Search(len(CNIPDataStart), func(i int) bool {
+	firstByte := ipLong >> 24
+	if CNIPDataRange[firstByte].end == 0 {
+		return false
+	}
+	ipIndex := searchRange(CNIPDataRange[firstByte].start, CNIPDataRange[firstByte].end, func(i int) bool {
 		return CNIPDataStart[i] > ipLong
 	})
 	ipIndex--

util.go

@@ -416,3 +416,18 @@ func ip2long(ipstr string) (uint32, error) {
 	}
 	return binary.BigEndian.Uint32(ip), nil
 }
+
+// search between [start, end]
+func searchRange(start, end int, f func(int) bool) int {
+	i, j := start, end+1
+	for i < j {
+		h := i + (j-i)/2 // avoid overflow when computing h
+		// i ≤ h < j
+		if !f(h) {
+			i = h + 1 // preserves f(i-1) == false
+		} else {
+			j = h // preserves f(j) == true
+		}
+	}
+	return i
+}