wal: fix wal

wal/util.go

@@ -0,0 +1,91 @@
+package wal
+
+import (
+	"fmt"
+	"log"
+	"os"
+)
+
+func Exist(dirpath string) bool {
+	names, err := readDir(dirpath)
+	if err != nil {
+		return false
+	}
+	return len(names) != 0
+}
+
+// The input names should be sorted.
+// serachIndex returns the array index of the last name that has
+// a smaller raft index section than the given raft index.
+func searchIndex(names []string, index int64) (int, bool) {
+	for i := len(names) - 1; i >= 0; i-- {
+		name := names[i]
+		_, curIndex, err := parseWalName(name)
+		if err != nil {
+			panic("parse correct name error")
+		}
+		if index >= curIndex {
+			return i, true
+		}
+	}
+	return -1, false
+}
+
+// names should have been sorted based on sequence number.
+// isValidSeq checks whether seq increases continuously.
+func isValidSeq(names []string) bool {
+	var lastSeq int64
+	for _, name := range names {
+		curSeq, _, err := parseWalName(name)
+		if err != nil {
+			panic("parse correct name error")
+		}
+		if lastSeq != 0 && lastSeq != curSeq-1 {
+			return false
+		}
+		lastSeq = curSeq
+	}
+	return true
+}
+
+// readDir returns the filenames in wal directory.
+func readDir(dirpath string) ([]string, error) {
+	dir, err := os.Open(dirpath)
+	if err != nil {
+		return nil, err
+	}
+	defer dir.Close()
+	names, err := dir.Readdirnames(-1)
+	if err != nil {
+		return nil, err
+	}
+	return names, nil
+}
+
+func checkWalNames(names []string) []string {
+	wnames := make([]string, 0)
+	for _, name := range names {
+		if _, _, err := parseWalName(name); err != nil {
+			log.Printf("parse %s: %v", name, err)
+			continue
+		}
+		wnames = append(wnames, name)
+	}
+	return wnames
+}
+
+func parseWalName(str string) (seq, index int64, err error) {
+	var num int
+	num, err = fmt.Sscanf(str, "%016x-%016x.wal", &seq, &index)
+	if num != 2 && err == nil {
+		err = fmt.Errorf("bad wal name: %s", str)
+	}
+	return
+}
+
+func max(a, b int64) int64 {
+	if a > b {
+		return a
+	}
+	return b
+}