v0.1.0 initial commit

internal/logfile/time.go

@@ -0,0 +1,84 @@
+package logfile
+
+// parseRFC3339Nano parses an RFC3339 stamp with optional fractional seconds
+// into unix nanoseconds. Hand-rolled to keep the index pass allocation-free.
+func parseRFC3339Nano(b []byte) (int64, bool) {
+	if len(b) < 19 {
+		return 0, false
+	}
+	if b[4] != '-' || b[7] != '-' || (b[10] != 'T' && b[10] != 't') || b[13] != ':' || b[16] != ':' {
+		return 0, false
+	}
+	y, ok1 := numField(b[0:4])
+	mo, ok2 := numField(b[5:7])
+	d, ok3 := numField(b[8:10])
+	h, ok4 := numField(b[11:13])
+	mi, ok5 := numField(b[14:16])
+	s, ok6 := numField(b[17:19])
+	if !ok1 || !ok2 || !ok3 || !ok4 || !ok5 || !ok6 {
+		return 0, false
+	}
+
+	i := 19
+	var frac int64
+	if i < len(b) && b[i] == '.' {
+		scale := int64(100000000)
+		for i++; i < len(b) && b[i] >= '0' && b[i] <= '9'; i++ {
+			if scale > 0 {
+				frac += int64(b[i]-'0') * scale
+				scale /= 10
+			}
+		}
+	}
+
+	var offSec int64
+	if i < len(b) {
+		switch b[i] {
+		case 'Z', 'z':
+		case '+', '-':
+			if i+6 > len(b) || b[i+3] != ':' {
+				return 0, false
+			}
+			oh, okh := numField(b[i+1 : i+3])
+			om, okm := numField(b[i+4 : i+6])
+			if !okh || !okm {
+				return 0, false
+			}
+			offSec = int64(oh)*3600 + int64(om)*60
+			if b[i] == '-' {
+				offSec = -offSec
+			}
+		}
+	}
+
+	sec := daysFromCivil(y, mo, d)*86400 + int64(h)*3600 + int64(mi)*60 + int64(s) - offSec
+	return sec*1e9 + frac, true
+}
+
+func numField(b []byte) (int, bool) {
+	v := 0
+	for _, c := range b {
+		if c < '0' || c > '9' {
+			return 0, false
+		}
+		v = v*10 + int(c-'0')
+	}
+	return v, true
+}
+
+// daysFromCivil returns days since 1970-01-01 (Hinnant's civil-date algorithm).
+func daysFromCivil(y, m, d int) int64 {
+	if m <= 2 {
+		y--
+	}
+	era := y
+	if era < 0 {
+		era -= 399
+	}
+	era /= 400
+	yoe := y - era*400
+	mp := (m + 9) % 12
+	doy := (153*mp+2)/5 + d - 1
+	doe := yoe*365 + yoe/4 - yoe/100 + doy
+	return int64(era)*146097 + int64(doe) - 719468
+}