cronexpr parser

timer/cron.go

@@ -0,0 +1,174 @@
+package timer
+
+import (
+	"fmt"
+	"math"
+	"strconv"
+	"strings"
+	_ "time"
+)
+
+type CronField uint64
+
+const maxCronField = math.MaxUint64
+
+// Field name   | Mandatory? | Allowed values | Allowed special characters
+// ----------   | ---------- | -------------- | --------------------------
+// Seconds      | No         | 0-59           | * / , -
+// Minutes      | Yes        | 0-59           | * / , -
+// Hours        | Yes        | 0-23           | * / , -
+// Day of month | Yes        | 1-31           | * / , -
+// Month        | Yes        | 1-12           | * / , -
+// Day of week  | Yes        | 0-6            | * / , -
+type CronExpr struct {
+	sec   CronField
+	min   CronField
+	hour  CronField
+	dom   CronField
+	month CronField
+	dow   CronField
+}
+
+func NewCronExpr(expr string) (cronExpr *CronExpr, err error) {
+	fields := strings.Fields(expr)
+	if len(fields) != 5 && len(fields) != 6 {
+		err = fmt.Errorf("invalid expr %v: expected 5 or 6 fields, got %v", expr, len(fields))
+		return
+	}
+
+	if len(fields) == 5 {
+		fields = append([]string{"0"}, fields...)
+	}
+
+	cronExpr = new(CronExpr)
+	// Seconds
+	cronExpr.sec, err = parseCronField(fields[0], 0, 59)
+	if err != nil {
+		goto parseError
+	}
+	// Minutes
+	cronExpr.min, err = parseCronField(fields[1], 0, 59)
+	if err != nil {
+		goto parseError
+	}
+	// Hours
+	cronExpr.hour, err = parseCronField(fields[2], 0, 23)
+	if err != nil {
+		goto parseError
+	}
+	// Day of month
+	cronExpr.dom, err = parseCronField(fields[3], 1, 31)
+	if err != nil {
+		goto parseError
+	}
+	// Month
+	cronExpr.month, err = parseCronField(fields[4], 1, 12)
+	if err != nil {
+		goto parseError
+	}
+	// Day of week
+	cronExpr.dow, err = parseCronField(fields[5], 0, 6)
+	if err != nil {
+		goto parseError
+	}
+	return
+
+parseError:
+	err = fmt.Errorf("invalid expr %v: %v", expr, err)
+	return
+}
+
+// 1. *
+// 2. num
+// 3. */num
+// 4. num-num
+// 5. num-num/num
+// 6. num/num (means num-max/num)
+func parseCronField(field string, min int, max int) (cronField CronField, err error) {
+	fields := strings.Split(field, ",")
+	for _, field := range fields {
+		rangeAndIncr := strings.Split(field, "/")
+		if len(rangeAndIncr) > 2 {
+			err = fmt.Errorf("too many slashes: %v", field)
+			return
+		}
+
+		// range
+		startAndEnd := strings.Split(rangeAndIncr[0], "-")
+		if len(startAndEnd) > 2 {
+			err = fmt.Errorf("too many hyphens: %v", rangeAndIncr[0])
+			return
+		}
+
+		var start, end int
+		if startAndEnd[0] == "*" {
+			if len(startAndEnd) != 1 {
+				err = fmt.Errorf("invalid range: %v", rangeAndIncr[0])
+				return
+			}
+			start = min
+			end = max
+		} else {
+			// start
+			start, err = strconv.Atoi(startAndEnd[0])
+			if err != nil {
+				err = fmt.Errorf("invalid range: %v", rangeAndIncr[0])
+				return
+			}
+			// end
+			if len(startAndEnd) == 1 {
+				if len(rangeAndIncr) == 2 {
+					end = max
+				} else {
+					end = start
+				}
+			} else {
+				end, err = strconv.Atoi(startAndEnd[1])
+				if err != nil {
+					err = fmt.Errorf("invalid range: %v", rangeAndIncr[0])
+					return
+				}
+			}
+		}
+
+		if start > end {
+			err = fmt.Errorf("invalid range: %v", rangeAndIncr[0])
+			return
+		}
+		if start < min {
+			err = fmt.Errorf("out of range [%v, %v]: %v", min, max, rangeAndIncr[0])
+			return
+		}
+		if end > max {
+			err = fmt.Errorf("out of range [%v, %v]: %v", min, max, rangeAndIncr[0])
+			return
+		}
+
+		// increment
+		var incr int
+		if len(rangeAndIncr) == 1 {
+			incr = 1
+		} else {
+			incr, err = strconv.Atoi(rangeAndIncr[1])
+			if err != nil {
+				err = fmt.Errorf("invalid increment: %v", rangeAndIncr[1])
+				return
+			}
+			if incr <= 0 {
+				err = fmt.Errorf("invalid increment: %v", incr)
+				return
+			}
+		}
+
+		// cronField
+		if incr == 1 {
+			cronField |= ^(maxCronField << uint(end+1)) & (maxCronField << uint(start))
+		} else {
+			for i := start; i <= end; i += incr {
+				cronField |= 1 << uint(i)
+			}
+		}
+	}
+
+	return
+}