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https://github.com/golang/go
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fmt: speed up floating point print, clean up some code
%g down to two mallocs from four. Also a mild speedup. fmt_test.BenchmarkSprintfFloat 3016 2703 -10.38% Fixes #2557. R=rsc CC=golang-dev https://golang.org/cl/5491054
This commit is contained in:
Rob Pike
parent
29264c6f4f
commit
04faa08c07
@ -154,12 +154,17 @@ func putint(buf []byte, base, val uint64, digits string) int {
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return i - 1
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}
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var (
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trueBytes = []byte("true")
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falseBytes = []byte("false")
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)
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// fmt_boolean formats a boolean.
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func (f *fmt) fmt_boolean(v bool) {
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if v {
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f.padString("true")
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f.pad(trueBytes)
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} else {
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f.padString("false")
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f.pad(falseBytes)
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}
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}
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@ -283,31 +288,18 @@ func (f *fmt) fmt_s(s string) {
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}
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// fmt_sx formats a string as a hexadecimal encoding of its bytes.
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func (f *fmt) fmt_sx(s string) {
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t := ""
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func (f *fmt) fmt_sx(s, digits string) {
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// TODO: Avoid buffer by pre-padding.
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var b bytes.Buffer
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for i := 0; i < len(s); i++ {
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if i > 0 && f.space {
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t += " "
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b.WriteByte(' ')
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}
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v := s[i]
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t += string(ldigits[v>>4])
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t += string(ldigits[v&0xF])
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b.WriteByte(digits[v>>4])
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b.WriteByte(digits[v&0xF])
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}
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f.padString(t)
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}
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// fmt_sX formats a string as an uppercase hexadecimal encoding of its bytes.
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func (f *fmt) fmt_sX(s string) {
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t := ""
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for i := 0; i < len(s); i++ {
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if i > 0 && f.space {
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t += " "
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}
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v := s[i]
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t += string(udigits[v>>4])
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t += string(udigits[v&0xF])
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}
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f.padString(t)
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f.pad(b.Bytes())
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}
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// fmt_q formats a string as a double-quoted, escaped Go string constant.
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@ -329,13 +321,13 @@ func (f *fmt) fmt_q(s string) {
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// fmt_qc formats the integer as a single-quoted, escaped Go character constant.
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// If the character is not valid Unicode, it will print '\ufffd'.
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func (f *fmt) fmt_qc(c int64) {
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var quoted string
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var quoted []byte
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if f.plus {
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quoted = strconv.QuoteRuneToASCII(rune(c))
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quoted = strconv.AppendQuoteRuneToASCII(f.intbuf[0:0], rune(c))
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} else {
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quoted = strconv.QuoteRune(rune(c))
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quoted = strconv.AppendQuoteRune(f.intbuf[0:0], rune(c))
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}
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f.padString(quoted)
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f.pad(quoted)
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}
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// floating-point
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@ -347,57 +339,70 @@ func doPrec(f *fmt, def int) int {
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return def
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}
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// formatFloat formats a float64; it is an efficient equivalent to f.pad(strconv.FormatFloat()...).
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func (f *fmt) formatFloat(v float64, verb byte, prec, n int) {
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// We leave one byte at the beginning of f.intbuf for a sign if needed,
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// and make it a space, which we might be able to use.
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f.intbuf[0] = ' '
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slice := strconv.AppendFloat(f.intbuf[0:1], v, verb, prec, n)
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// Add a plus sign or space to the floating-point string representation if missing and required.
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func (f *fmt) plusSpace(s string) {
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if s[0] != '-' {
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// The formatted number starts at slice[1].
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switch slice[1] {
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case '-', '+':
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// We're set; drop the leading space.
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slice = slice[1:]
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default:
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// There's no sign, but we might need one.
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if f.plus {
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s = "+" + s
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slice[0] = '+'
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} else if f.space {
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s = " " + s
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// space is already there
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} else {
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slice = slice[1:]
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}
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}
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f.padString(s)
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f.pad(slice)
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}
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// fmt_e64 formats a float64 in the form -1.23e+12.
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func (f *fmt) fmt_e64(v float64) { f.plusSpace(strconv.FormatFloat(v, 'e', doPrec(f, 6), 64)) }
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func (f *fmt) fmt_e64(v float64) { f.formatFloat(v, 'e', doPrec(f, 6), 64) }
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// fmt_E64 formats a float64 in the form -1.23E+12.
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func (f *fmt) fmt_E64(v float64) { f.plusSpace(strconv.FormatFloat(v, 'E', doPrec(f, 6), 64)) }
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func (f *fmt) fmt_E64(v float64) { f.formatFloat(v, 'E', doPrec(f, 6), 64) }
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// fmt_f64 formats a float64 in the form -1.23.
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func (f *fmt) fmt_f64(v float64) { f.plusSpace(strconv.FormatFloat(v, 'f', doPrec(f, 6), 64)) }
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func (f *fmt) fmt_f64(v float64) { f.formatFloat(v, 'f', doPrec(f, 6), 64) }
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// fmt_g64 formats a float64 in the 'f' or 'e' form according to size.
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func (f *fmt) fmt_g64(v float64) { f.plusSpace(strconv.FormatFloat(v, 'g', doPrec(f, -1), 64)) }
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func (f *fmt) fmt_g64(v float64) { f.formatFloat(v, 'g', doPrec(f, -1), 64) }
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// fmt_g64 formats a float64 in the 'f' or 'E' form according to size.
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func (f *fmt) fmt_G64(v float64) { f.plusSpace(strconv.FormatFloat(v, 'G', doPrec(f, -1), 64)) }
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func (f *fmt) fmt_G64(v float64) { f.formatFloat(v, 'G', doPrec(f, -1), 64) }
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// fmt_fb64 formats a float64 in the form -123p3 (exponent is power of 2).
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func (f *fmt) fmt_fb64(v float64) { f.plusSpace(strconv.FormatFloat(v, 'b', 0, 64)) }
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func (f *fmt) fmt_fb64(v float64) { f.formatFloat(v, 'b', 0, 64) }
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// float32
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// cannot defer to float64 versions
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// because it will get rounding wrong in corner cases.
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// fmt_e32 formats a float32 in the form -1.23e+12.
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func (f *fmt) fmt_e32(v float32) { f.plusSpace(strconv.FormatFloat(float64(v), 'e', doPrec(f, 6), 32)) }
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func (f *fmt) fmt_e32(v float32) { f.formatFloat(float64(v), 'e', doPrec(f, 6), 32) }
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// fmt_E32 formats a float32 in the form -1.23E+12.
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func (f *fmt) fmt_E32(v float32) { f.plusSpace(strconv.FormatFloat(float64(v), 'E', doPrec(f, 6), 32)) }
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func (f *fmt) fmt_E32(v float32) { f.formatFloat(float64(v), 'E', doPrec(f, 6), 32) }
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// fmt_f32 formats a float32 in the form -1.23.
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func (f *fmt) fmt_f32(v float32) { f.plusSpace(strconv.FormatFloat(float64(v), 'f', doPrec(f, 6), 32)) }
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func (f *fmt) fmt_f32(v float32) { f.formatFloat(float64(v), 'f', doPrec(f, 6), 32) }
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// fmt_g32 formats a float32 in the 'f' or 'e' form according to size.
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func (f *fmt) fmt_g32(v float32) { f.plusSpace(strconv.FormatFloat(float64(v), 'g', doPrec(f, -1), 32)) }
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func (f *fmt) fmt_g32(v float32) { f.formatFloat(float64(v), 'g', doPrec(f, -1), 32) }
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// fmt_G32 formats a float32 in the 'f' or 'E' form according to size.
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func (f *fmt) fmt_G32(v float32) { f.plusSpace(strconv.FormatFloat(float64(v), 'G', doPrec(f, -1), 32)) }
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func (f *fmt) fmt_G32(v float32) { f.formatFloat(float64(v), 'G', doPrec(f, -1), 32) }
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// fmt_fb32 formats a float32 in the form -123p3 (exponent is power of 2).
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func (f *fmt) fmt_fb32(v float32) { f.padString(strconv.FormatFloat(float64(v), 'b', 0, 32)) }
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func (f *fmt) fmt_fb32(v float32) { f.formatFloat(float64(v), 'b', 0, 32) }
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// fmt_c64 formats a complex64 according to the verb.
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func (f *fmt) fmt_c64(v complex64, verb rune) {
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@ -503,9 +503,9 @@ func (p *pp) fmtString(v string, verb rune, goSyntax bool) {
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case 's':
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p.fmt.fmt_s(v)
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case 'x':
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p.fmt.fmt_sx(v)
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p.fmt.fmt_sx(v, ldigits)
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case 'X':
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p.fmt.fmt_sX(v)
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p.fmt.fmt_sx(v, udigits)
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case 'q':
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p.fmt.fmt_q(v)
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default:
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@ -542,9 +542,9 @@ func (p *pp) fmtBytes(v []byte, verb rune, goSyntax bool, depth int) {
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case 's':
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p.fmt.fmt_s(s)
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case 'x':
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p.fmt.fmt_sx(s)
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p.fmt.fmt_sx(s, ldigits)
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case 'X':
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p.fmt.fmt_sX(s)
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p.fmt.fmt_sx(s, udigits)
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case 'q':
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p.fmt.fmt_q(s)
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default:
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