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format.go
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format.go
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package time
import (
"bytes"
"once"
"os"
"strconv"
)
const (
numeric = iota
alphabetic
separator
plus
minus
)
// These are predefined layouts for use in Time.Format.
// The standard time used in the layouts is:
// Mon Jan 2 15:04:05 MST 2006 (MST is GMT-0700)
// which is Unix time 1136243045.
// (Think of it as 01/02 03:04:05PM '06 -0700.)
// An underscore _ represents a space that
// may be replaced by a digit if the following number
// (a day) has two digits; for compatibility with
// fixed-width Unix time formats.
const (
ANSIC = "Mon Jan _2 15:04:05 2006"
UnixDate = "Mon Jan _2 15:04:05 MST 2006"
RubyDate = "Mon Jan 02 15:04:05 -0700 2006"
RFC822 = "02 Jan 06 1504 MST"
// RFC822 with Zulu time.
RFC822Z = "02 Jan 06 1504 -0700"
RFC850 = "Monday, 02-Jan-06 15:04:05 MST"
RFC1123 = "Mon, 02 Jan 2006 15:04:05 MST"
Kitchen = "3:04PM"
// Special case: use Z to get the time zone formatted according to ISO 8601,
// which is -0700 or Z for UTC
ISO8601 = "2006-01-02T15:04:05Z"
)
const (
stdLongMonth = "January"
stdMonth = "Jan"
stdNumMonth = "1"
stdZeroMonth = "01"
stdLongWeekDay = "Monday"
stdWeekDay = "Mon"
stdDay = "2"
stdUnderDay = "_2"
stdZeroDay = "02"
stdHour = "15"
stdHour12 = "3"
stdZeroHour12 = "03"
stdMinute = "4"
stdZeroMinute = "04"
stdSecond = "5"
stdZeroSecond = "05"
stdLongYear = "2006"
stdYear = "06"
stdZulu = "1504"
stdPM = "PM"
stdpm = "pm"
stdTZ = "MST"
stdISO8601TZ = "Z" // prints Z for UTC
stdNumTZ = "0700" // always numeric
)
var longDayNames = []string{
"Sunday",
"Monday",
"Tuesday",
"Wednesday",
"Thursday",
"Friday",
"Saturday",
}
var shortDayNames = []string{
"Sun",
"Mon",
"Tue",
"Wed",
"Thu",
"Fri",
"Sat",
}
var shortMonthNames = []string{
"---",
"Jan",
"Feb",
"Mar",
"Apr",
"May",
"Jun",
"Jul",
"Aug",
"Sep",
"Oct",
"Nov",
"Dec",
}
var longMonthNames = []string{
"---",
"January",
"February",
"March",
"April",
"May",
"June",
"July",
"August",
"September",
"October",
"November",
"December",
}
func lookup(tab []string, val string) (int, os.Error) {
for i, v := range tab {
if v == val {
return i, nil
}
}
return -1, errBad
}
func charType(c uint8) int {
switch {
case '0' <= c && c <= '9':
return numeric
case c == '_': // underscore; treated like a number when printing
return numeric
case 'a' <= c && c <= 'z', 'A' <= c && c <= 'Z':
return alphabetic
case c == '+':
return plus
case c == '-':
return minus
}
return separator
}
func pad(i int, padding string) string {
s := strconv.Itoa(i)
if i < 10 {
s = padding + s
}
return s
}
func zeroPad(i int) string { return pad(i, "0") }
// Format returns a textual representation of the time value formatted
// according to layout. The layout defines the format by showing the
// representation of a standard time, which is then used to describe
// the time to be formatted. Predefined layouts ANSIC, UnixDate,
// ISO8601 and others describe standard representations.
func (t *Time) Format(layout string) string {
b := new(bytes.Buffer)
// Each iteration generates one piece
for len(layout) > 0 {
c := layout[0]
pieceType := charType(c)
i := 0
for i < len(layout) && charType(layout[i]) == pieceType {
i++
}
p := layout[0:i]
layout = layout[i:]
switch p {
case stdYear:
p = strconv.Itoa64(t.Year % 100)
case stdLongYear:
p = strconv.Itoa64(t.Year)
case stdMonth:
p = shortMonthNames[t.Month]
case stdLongMonth:
p = longMonthNames[t.Month]
case stdNumMonth:
p = strconv.Itoa(t.Month)
case stdZeroMonth:
p = zeroPad(t.Month)
case stdWeekDay:
p = shortDayNames[t.Weekday]
case stdLongWeekDay:
p = longDayNames[t.Weekday]
case stdDay:
p = strconv.Itoa(t.Day)
case stdUnderDay:
p = pad(t.Day, " ")
case stdZeroDay:
p = zeroPad(t.Day)
case stdHour:
p = zeroPad(t.Hour)
case stdHour12:
p = strconv.Itoa(t.Hour % 12)
case stdZeroHour12:
p = zeroPad(t.Hour % 12)
case stdMinute:
p = strconv.Itoa(t.Minute)
case stdZeroMinute:
p = zeroPad(t.Minute)
case stdSecond:
p = strconv.Itoa(t.Second)
case stdZeroSecond:
p = zeroPad(t.Second)
case stdZulu:
p = zeroPad(t.Hour) + zeroPad(t.Minute)
case stdISO8601TZ, stdNumTZ:
// Ugly special case. We cheat and take "Z" to mean "the time
// zone as formatted for ISO 8601".
zone := t.ZoneOffset / 60 // convert to minutes
if p == stdISO8601TZ && t.ZoneOffset == 0 {
p = "Z"
} else {
// If the reference time is stdNumTZ (0700), the sign has already been
// emitted but may be wrong. For stdISO8601TZ we must print it.
if p == stdNumTZ && b.Len() > 0 {
soFar := b.Bytes()
if soFar[len(soFar)-1] == '-' && zone >= 0 {
// fix the sign
soFar[len(soFar)-1] = '+'
} else {
zone = -zone
}
p = ""
} else {
if zone < 0 {
p = "-"
zone = -zone
} else {
p = "+"
}
}
p += zeroPad(zone / 60)
p += zeroPad(zone % 60)
}
case stdPM:
if t.Hour >= 12 {
p = "PM"
} else {
p = "AM"
}
case stdpm:
if t.Hour >= 12 {
p = "pm"
} else {
p = "am"
}
case stdTZ:
if t.Zone != "" {
p = t.Zone
} else {
// No time zone known for this time, but we must print one.
// Use the -0700 format.
zone := t.ZoneOffset / 60 // convert to minutes
if zone < 0 {
p = "-"
zone = -zone
} else {
p = "+"
}
p += zeroPad(zone / 60)
p += zeroPad(zone % 60)
}
}
b.WriteString(p)
}
return b.String()
}
// String returns a Unix-style representation of the time value.
func (t *Time) String() string { return t.Format(UnixDate) }
var errBad = os.ErrorString("bad") // just a marker; not returned to user
// ParseError describes a problem parsing a time string.
type ParseError struct {
Layout string
Value string
LayoutElem string
ValueElem string
Message string
}
// String is the string representation of a ParseError.
func (e *ParseError) String() string {
if e.Message == "" {
return "parsing time " +
strconv.Quote(e.Value) + " as " +
strconv.Quote(e.Layout) + ": cannot parse " +
strconv.Quote(e.ValueElem) + " as " +
strconv.Quote(e.LayoutElem)
}
return "parsing time " +
strconv.Quote(e.Value) + e.Message
}
// To simplify comparison, collapse an initial run of spaces into a single space.
func collapseSpaces(s string) string {
if len(s) <= 1 || s[0] != ' ' {
return s
}
var i int
for i = 1; i < len(s); i++ {
if s[i] != ' ' {
return s[i-1:]
}
}
return " "
}
// Parse parses a formatted string and returns the time value it represents.
// The layout defines the format by showing the representation of a standard
// time, which is then used to describe the string to be parsed. Predefined
// layouts ANSIC, UnixDate, ISO8601 and others describe standard
// representations.
//
// Only those elements present in the value will be set in the returned time
// structure. Also, if the input string represents an inconsistent time
// (such as having the wrong day of the week), the returned value will also
// be inconsistent. In any case, the elements of the returned time will be
// sane: hours in 0..23, minutes in 0..59, day of month in 0..31, etc.
func Parse(alayout, avalue string) (*Time, os.Error) {
var t Time
const formatErr = ": different format from "
rangeErrString := "" // set if a value is out of range
pmSet := false // do we need to add 12 to the hour?
// Each iteration steps along one piece
layout, value := alayout, avalue
sign := "" // pending + or - from previous iteration
for len(layout) > 0 && len(value) > 0 {
c := layout[0]
pieceType := charType(c)
var i int
for i = 0; i < len(layout) && charType(layout[i]) == pieceType; i++ {
}
reference := layout[0:i]
prevLayout := layout
layout = layout[i:]
// Ugly time zone handling.
if reference == "Z" {
// Special case for ISO8601 time zone: "Z" or "-0800"
if value[0] == 'Z' {
i = 1
} else if len(value) >= 5 {
i = 5
} else {
return nil, &ParseError{Layout: alayout, Value: avalue, Message: formatErr + alayout}
}
} else {
c = value[0]
if charType(c) != pieceType {
// Ugly management of signs. Reference and data might differ.
// 1. Could be a minus sign introducing a negative year.
if c == '-' && pieceType != minus {
value = value[1:]
layout = prevLayout // don't consume reference item
sign = "-"
continue
}
// 2. Could be a plus sign for a +0100 time zone, represented by -0700 in the standard.
if c == '+' && pieceType == minus {
value = value[1:]
layout = prevLayout[1:] // absorb sign in both value and layout
sign = "+"
continue
}
return nil, &ParseError{Layout: alayout, Value: avalue, Message: formatErr + alayout}
}
for i = 0; i < len(value) && charType(value[i]) == pieceType; i++ {
}
}
p := value[0:i]
value = value[i:]
switch pieceType {
case separator:
// Separators must match but initial run of spaces is treated as a single space.
if collapseSpaces(p) != collapseSpaces(reference) {
return nil, &ParseError{Layout: alayout, Value: avalue, Message: formatErr + alayout}
}
continue
case plus, minus:
if len(p) == 1 { // ++ or -- don't count as signs.
sign = p
continue
}
}
var err os.Error
switch reference {
case stdYear:
t.Year, err = strconv.Atoi64(p)
if t.Year >= 69 { // Unix time starts Dec 31 1969 in some time zones
t.Year += 1900
} else {
t.Year += 2000
}
case stdLongYear:
t.Year, err = strconv.Atoi64(p)
if sign == "-" {
t.Year = -t.Year
}
case stdMonth:
t.Month, err = lookup(shortMonthNames, p)
case stdLongMonth:
t.Month, err = lookup(longMonthNames, p)
case stdNumMonth, stdZeroMonth:
t.Month, err = strconv.Atoi(p)
if t.Month <= 0 || 12 < t.Month {
rangeErrString = "month"
}
case stdWeekDay:
t.Weekday, err = lookup(shortDayNames, p)
case stdLongWeekDay:
t.Weekday, err = lookup(longDayNames, p)
case stdDay, stdUnderDay, stdZeroDay:
t.Day, err = strconv.Atoi(p)
if t.Day < 0 || 31 < t.Day {
// TODO: be more thorough in date check?
rangeErrString = "day"
}
case stdHour:
t.Hour, err = strconv.Atoi(p)
if t.Hour < 0 || 24 <= t.Hour {
rangeErrString = "hour"
}
case stdHour12, stdZeroHour12:
t.Hour, err = strconv.Atoi(p)
if t.Hour < 0 || 12 < t.Hour {
rangeErrString = "hour"
}
case stdMinute, stdZeroMinute:
t.Minute, err = strconv.Atoi(p)
if t.Minute < 0 || 60 <= t.Minute {
rangeErrString = "minute"
}
case stdSecond, stdZeroSecond:
t.Second, err = strconv.Atoi(p)
if t.Second < 0 || 60 <= t.Second {
rangeErrString = "second"
}
case stdZulu:
if len(p) != 4 {
err = os.ErrorString("HHMM value must be 4 digits")
break
}
t.Hour, err = strconv.Atoi(p[0:2])
if err != nil {
t.Minute, err = strconv.Atoi(p[2:4])
}
case stdISO8601TZ, stdNumTZ:
if reference == stdISO8601TZ {
if p == "Z" {
t.Zone = "UTC"
break
}
// len(p) known to be 5: "-0800"
sign = p[0:1]
p = p[1:]
} else {
// len(p) known to be 4: "0800" and sign is set
}
var hr, min int
hr, err = strconv.Atoi(p[0:2])
if err != nil {
min, err = strconv.Atoi(p[2:4])
}
t.ZoneOffset = (hr*60 + min) * 60 // offset is in seconds
switch sign[0] {
case '+':
case '-':
t.ZoneOffset = -t.ZoneOffset
default:
err = errBad
}
case stdPM:
if p == "PM" {
pmSet = true
} else if p != "AM" {
err = errBad
}
case stdpm:
if p == "pm" {
pmSet = true
} else if p != "am" {
err = errBad
}
case stdTZ:
// Does it look like a time zone?
if p == "UTC" {
t.Zone = p
break
}
// All other time zones look like XXT or XXXT.
if len(p) != 3 && len(p) != 4 || p[len(p)-1] != 'T' {
err = errBad
}
for i := 0; i < len(p); i++ {
if p[i] < 'A' || 'Z' < p[i] {
err = errBad
}
}
if err != nil {
break
}
// It's a valid format.
t.Zone = p
// Can we find it in the table?
once.Do(setupZone)
for _, z := range zones {
if p == z.zone.name {
t.ZoneOffset = z.zone.utcoff
break
}
}
}
if rangeErrString != "" {
return nil, &ParseError{alayout, avalue, reference, p, ": " + rangeErrString + " out of range"}
}
if err != nil {
return nil, &ParseError{alayout, avalue, reference, p, ""}
}
sign = ""
}
if pmSet && t.Hour < 12 {
t.Hour += 12
}
return &t, nil
}