127 lines
2.5 KiB
Go
127 lines
2.5 KiB
Go
package console
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import "time"
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// appendDuration appends a string representing the duration in the form "72h3m0.5s".
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// Leading zero units are omitted. As a special case, durations less than one
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// second format use a smaller unit (milli-, micro-, or nanoseconds) to ensure
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// that the leading digit is non-zero. The zero duration formats as 0s.
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func appendDuration(dst []byte, d time.Duration) []byte {
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// Largest time is 2540400h10m10.000000000s
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var buf [32]byte
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w := len(buf)
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u := uint64(d)
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neg := d < 0
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if neg {
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u = -u
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}
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if u < uint64(time.Second) {
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// Special case: if duration is smaller than a second,
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// use smaller units, like 1.2ms
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var prec int
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w--
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buf[w] = 's'
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w--
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switch {
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case u == 0:
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return append(dst, "0s"...)
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case u < uint64(time.Microsecond):
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// print nanoseconds
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prec = 0
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buf[w] = 'n'
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case u < uint64(time.Millisecond):
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// print microseconds
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prec = 3
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// U+00B5 'µ' micro sign == 0xC2 0xB5
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w-- // Need room for two bytes.
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copy(buf[w:], "µ")
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default:
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// print milliseconds
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prec = 6
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buf[w] = 'm'
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}
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w, u = fmtFrac(buf[:w], u, prec)
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w = fmtInt(buf[:w], u)
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} else {
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w--
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buf[w] = 's'
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w, u = fmtFrac(buf[:w], u, 9)
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// u is now integer seconds
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w = fmtInt(buf[:w], u%60)
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u /= 60
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// u is now integer minutes
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if u > 0 {
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w--
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buf[w] = 'm'
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w = fmtInt(buf[:w], u%60)
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u /= 60
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// u is now integer hours
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// Stop at hours because days can be different lengths.
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if u > 0 {
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w--
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buf[w] = 'h'
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w = fmtInt(buf[:w], u%24)
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u /= 24
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if u > 0 {
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w--
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buf[w] = 'd'
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w = fmtInt(buf[:w], u)
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}
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}
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}
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}
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if neg {
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w--
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buf[w] = '-'
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}
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return append(dst, buf[w:]...)
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}
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// fmtFrac formats the fraction of v/10**prec (e.g., ".12345") into the
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// tail of buf, omitting trailing zeros. It omits the decimal
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// point too when the fraction is 0. It returns the index where the
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// output bytes begin and the value v/10**prec.
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func fmtFrac(buf []byte, v uint64, prec int) (nw int, nv uint64) {
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// Omit trailing zeros up to and including decimal point.
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w := len(buf)
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print := false
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for i := 0; i < prec; i++ {
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digit := v % 10
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print = print || digit != 0
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if print {
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w--
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buf[w] = byte(digit) + '0'
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}
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v /= 10
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}
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if print {
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w--
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buf[w] = '.'
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}
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return w, v
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}
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// fmtInt formats v into the tail of buf.
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// It returns the index where the output begins.
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func fmtInt(buf []byte, v uint64) int {
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w := len(buf)
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if v == 0 {
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w--
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buf[w] = '0'
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} else {
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for v > 0 {
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w--
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buf[w] = byte(v%10) + '0'
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v /= 10
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}
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}
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return w
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}
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