// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package fmt
import (
"math"
"strconv"
"unicode/utf8"
)
const (
// %b of an int64, plus a sign.
// Hex can add 0x and we handle it specially.
nByte = 65
ldigits = "0123456789abcdef"
udigits = "0123456789ABCDEF"
)
const (
signed = true
unsigned = false
)
var padZeroBytes = make([]byte, nByte)
var padSpaceBytes = make([]byte, nByte)
func init() {
for i := 0; i < nByte; i++ {
padZeroBytes[i] = '0'
padSpaceBytes[i] = ' '
}
}
// flags placed in a separate struct for easy clearing.
type fmtFlags struct {
widPresent bool
precPresent bool
minus bool
plus bool
sharp bool
space bool
unicode bool
uniQuote bool // Use 'x'= prefix for %U if printable.
zero bool
// For the formats %+v %#v, we set the plusV/sharpV flags
// and clear the plus/sharp flags since %+v and %#v are in effect
// different, flagless formats set at the top level.
plusV bool
sharpV bool
}
// A fmt is the raw formatter used by Printf etc.
// It prints into a buffer that must be set up separately.
type fmt struct {
intbuf [nByte]byte
buf *buffer
// width, precision
wid int
prec int
fmtFlags
}
func (f *fmt) clearflags() {
f.fmtFlags = fmtFlags{}
}
func (f *fmt) init(buf *buffer) {
f.buf = buf
f.clearflags()
}
// computePadding computes left and right padding widths (only one will be non-zero).
func (f *fmt) computePadding(width int) (padding []byte, leftWidth, rightWidth int) {
left := !f.minus
w := f.wid
if w < 0 {
left = false
w = -w
}
w -= width
if w > 0 {
if left && f.zero {
return padZeroBytes, w, 0
}
if left {
return padSpaceBytes, w, 0
} else {
// can't be zero padding on the right
return padSpaceBytes, 0, w
}
}
return
}
// writePadding generates n bytes of padding.
func (f *fmt) writePadding(n int, padding []byte) {
for n > 0 {
m := n
if m > nByte {
m = nByte
}
f.buf.Write(padding[0:m])
n -= m
}
}
// pad appends b to f.buf, padded on left (w > 0) or right (w < 0 or f.minus).
func (f *fmt) pad(b []byte) {
if !f.widPresent || f.wid == 0 {
f.buf.Write(b)
return
}
padding, left, right := f.computePadding(utf8.RuneCount(b))
if left > 0 {
f.writePadding(left, padding)
}
f.buf.Write(b)
if right > 0 {
f.writePadding(right, padding)
}
}
// padString appends s to buf, padded on left (w > 0) or right (w < 0 or f.minus).
func (f *fmt) padString(s string) {
if !f.widPresent || f.wid == 0 {
f.buf.WriteString(s)
return
}
padding, left, right := f.computePadding(utf8.RuneCountInString(s))
if left > 0 {
f.writePadding(left, padding)
}
f.buf.WriteString(s)
if right > 0 {
f.writePadding(right, padding)
}
}
var (
trueBytes = []byte("true")
falseBytes = []byte("false")
)
// fmt_boolean formats a boolean.
func (f *fmt) fmt_boolean(v bool) {
if v {
f.pad(trueBytes)
} else {
f.pad(falseBytes)
}
}
// integer; interprets prec but not wid. Once formatted, result is sent to pad()
// and then flags are cleared.
func (f *fmt) integer(a int64, base uint64, signedness bool, digits string) {
// precision of 0 and value of 0 means "print nothing"
if f.precPresent && f.prec == 0 && a == 0 {
return
}
negative := signedness == signed && a < 0
if negative {
a = -a
}
var buf []byte = f.intbuf[0:]
if f.widPresent || f.precPresent || f.plus || f.space {
width := f.wid + f.prec // Only one will be set, both are positive; this provides the maximum.
if base == 16 && f.sharp {
// Also adds "0x".
width += 2
}
if f.unicode {
// Also adds "U+".
width += 2
if f.uniQuote {
// Also adds " 'x'".
width += 1 + 1 + utf8.UTFMax + 1
}
}
if negative || f.plus || f.space {
width++
}
if width > nByte {
// We're going to need a bigger boat.
buf = make([]byte, width)
}
}
// two ways to ask for extra leading zero digits: %.3d or %03d.
// apparently the first cancels the second.
prec := 0
if f.precPresent {
prec = f.prec
f.zero = false
} else if f.zero && f.widPresent && !f.minus && f.wid > 0 {
prec = f.wid
if negative || f.plus || f.space {
prec-- // leave room for sign
}
}
// format a into buf, ending at buf[i]. (printing is easier right-to-left.)
// a is made into unsigned ua. we could make things
// marginally faster by splitting the 32-bit case out into a separate
// block but it's not worth the duplication, so ua has 64 bits.
i := len(buf)
ua := uint64(a)
// use constants for the division and modulo for more efficient code.
// switch cases ordered by popularity.
switch base {
case 10:
for ua >= 10 {
i--
next := ua / 10
buf[i] = byte('0' + ua - next*10)
ua = next
}
case 16:
for ua >= 16 {
i--
buf[i] = digits[ua&0xF]
ua >>= 4
}
case 8:
for ua >= 8 {
i--
buf[i] = byte('0' + ua&7)
ua >>= 3
}
case 2:
for ua >= 2 {
i--
buf[i] = byte('0' + ua&1)
ua >>= 1
}
default:
panic("fmt: unknown base; can't happen")
}
i--
buf[i] = digits[ua]
for i > 0 && prec > len(buf)-i {
i--
buf[i] = '0'
}
// Various prefixes: 0x, -, etc.
if f.sharp {
switch base {
case 8:
if buf[i] != '0' {
i--
buf[i] = '0'
}
case 16:
i--
buf[i] = 'x' + digits[10] - 'a'
i--
buf[i] = '0'
}
}
if f.unicode {
i--
buf[i] = '+'
i--
buf[i] = 'U'
}
if negative {
i--
buf[i] = '-'
} else if f.plus {
i--
buf[i] = '+'
} else if f.space {
i--
buf[i] = ' '
}
// If we want a quoted char for %#U, move the data up to make room.
if f.unicode && f.uniQuote && a >= 0 && a <= utf8.MaxRune && strconv.IsPrint(rune(a)) {
runeWidth := utf8.RuneLen(rune(a))
width := 1 + 1 + runeWidth + 1 // space, quote, rune, quote
copy(buf[i-width:], buf[i:]) // guaranteed to have enough room.
i -= width
// Now put " 'x'" at the end.
j := len(buf) - width
buf[j] = ' '
j++
buf[j] = '\''
j++
utf8.EncodeRune(buf[j:], rune(a))
j += runeWidth
buf[j] = '\''
}
f.pad(buf[i:])
}
// truncate truncates the string to the specified precision, if present.
func (f *fmt) truncate(s string) string {
if f.precPresent && f.prec < utf8.RuneCountInString(s) {
n := f.prec
for i := range s {
if n == 0 {
s = s[:i]
break
}
n--
}
}
return s
}
// fmt_s formats a string.
func (f *fmt) fmt_s(s string) {
s = f.truncate(s)
f.padString(s)
}
// fmt_sbx formats a string or byte slice as a hexadecimal encoding of its bytes.
func (f *fmt) fmt_sbx(s string, b []byte, digits string) {
n := len(b)
if b == nil {
n = len(s)
}
x := digits[10] - 'a' + 'x'
// TODO: Avoid buffer by pre-padding.
var buf []byte
for i := 0; i < n; i++ {
if i > 0 && f.space {
buf = append(buf, ' ')
}
if f.sharp && (f.space || i == 0) {
buf = append(buf, '0', x)
}
var c byte
if b == nil {
c = s[i]
} else {
c = b[i]
}
buf = append(buf, digits[c>>4], digits[c&0xF])
}
f.pad(buf)
}
// fmt_sx formats a string as a hexadecimal encoding of its bytes.
func (f *fmt) fmt_sx(s, digits string) {
if f.precPresent && f.prec < len(s) {
s = s[:f.prec]
}
f.fmt_sbx(s, nil, digits)
}
// fmt_bx formats a byte slice as a hexadecimal encoding of its bytes.
func (f *fmt) fmt_bx(b []byte, digits string) {
if f.precPresent && f.prec < len(b) {
b = b[:f.prec]
}
f.fmt_sbx("", b, digits)
}
// fmt_q formats a string as a double-quoted, escaped Go string constant.
func (f *fmt) fmt_q(s string) {
s = f.truncate(s)
var quoted string
if f.sharp && strconv.CanBackquote(s) {
quoted = "`" + s + "`"
} else {
if f.plus {
quoted = strconv.QuoteToASCII(s)
} else {
quoted = strconv.Quote(s)
}
}
f.padString(quoted)
}
// fmt_qc formats the integer as a single-quoted, escaped Go character constant.
// If the character is not valid Unicode, it will print '\ufffd'.
func (f *fmt) fmt_qc(c int64) {
var quoted []byte
if f.plus {
quoted = strconv.AppendQuoteRuneToASCII(f.intbuf[0:0], rune(c))
} else {
quoted = strconv.AppendQuoteRune(f.intbuf[0:0], rune(c))
}
f.pad(quoted)
}
// floating-point
func doPrec(f *fmt, def int) int {
if f.precPresent {
return f.prec
}
return def
}
// formatFloat formats a float64; it is an efficient equivalent to f.pad(strconv.FormatFloat()...).
func (f *fmt) formatFloat(v float64, verb byte, prec, n int) {
// Format number, reserving space for leading + sign if needed.
num := strconv.AppendFloat(f.intbuf[0:1], v, verb, prec, n)
if num[1] == '-' || num[1] == '+' {
num = num[1:]
} else {
num[0] = '+'
}
// Special handling for infinity, which doesn't look like a number so shouldn't be padded with zeros.
if math.IsInf(v, 0) {
if f.zero {
defer func() { f.zero = true }()
f.zero = false
}
}
// num is now a signed version of the number.
// If we're zero padding, want the sign before the leading zeros.
// Achieve this by writing the sign out and then padding the unsigned number.
if f.zero && f.widPresent && f.wid > len(num) {
if f.space && v >= 0 {
f.buf.WriteByte(' ') // This is what C does: even with zero, f.space means space.
f.wid--
} else if f.plus || v < 0 {
f.buf.WriteByte(num[0])
f.wid--
}
f.pad(num[1:])
return
}
// f.space says to replace a leading + with a space.
if f.space && num[0] == '+' {
num[0] = ' '
f.pad(num)
return
}
// Now we know the sign is attached directly to the number, if present at all.
// We want a sign if asked for, if it's negative, or if it's infinity (+Inf vs. -Inf).
if f.plus || num[0] == '-' || math.IsInf(v, 0) {
f.pad(num)
return
}
// No sign to show and the number is positive; just print the unsigned number.
f.pad(num[1:])
}
// fmt_e64 formats a float64 in the form -1.23e+12.
func (f *fmt) fmt_e64(v float64) { f.formatFloat(v, 'e', doPrec(f, 6), 64) }
// fmt_E64 formats a float64 in the form -1.23E+12.
func (f *fmt) fmt_E64(v float64) { f.formatFloat(v, 'E', doPrec(f, 6), 64) }
// fmt_f64 formats a float64 in the form -1.23.
func (f *fmt) fmt_f64(v float64) { f.formatFloat(v, 'f', doPrec(f, 6), 64) }
// fmt_g64 formats a float64 in the 'f' or 'e' form according to size.
func (f *fmt) fmt_g64(v float64) { f.formatFloat(v, 'g', doPrec(f, -1), 64) }
// fmt_G64 formats a float64 in the 'f' or 'E' form according to size.
func (f *fmt) fmt_G64(v float64) { f.formatFloat(v, 'G', doPrec(f, -1), 64) }
// fmt_fb64 formats a float64 in the form -123p3 (exponent is power of 2).
func (f *fmt) fmt_fb64(v float64) { f.formatFloat(v, 'b', 0, 64) }
// float32
// cannot defer to float64 versions
// because it will get rounding wrong in corner cases.
// fmt_e32 formats a float32 in the form -1.23e+12.
func (f *fmt) fmt_e32(v float32) { f.formatFloat(float64(v), 'e', doPrec(f, 6), 32) }
// fmt_E32 formats a float32 in the form -1.23E+12.
func (f *fmt) fmt_E32(v float32) { f.formatFloat(float64(v), 'E', doPrec(f, 6), 32) }
// fmt_f32 formats a float32 in the form -1.23.
func (f *fmt) fmt_f32(v float32) { f.formatFloat(float64(v), 'f', doPrec(f, 6), 32) }
// fmt_g32 formats a float32 in the 'f' or 'e' form according to size.
func (f *fmt) fmt_g32(v float32) { f.formatFloat(float64(v), 'g', doPrec(f, -1), 32) }
// fmt_G32 formats a float32 in the 'f' or 'E' form according to size.
func (f *fmt) fmt_G32(v float32) { f.formatFloat(float64(v), 'G', doPrec(f, -1), 32) }
// fmt_fb32 formats a float32 in the form -123p3 (exponent is power of 2).
func (f *fmt) fmt_fb32(v float32) { f.formatFloat(float64(v), 'b', 0, 32) }
// fmt_c64 formats a complex64 according to the verb.
func (f *fmt) fmt_c64(v complex64, verb rune) {
f.fmt_complex(float64(real(v)), float64(imag(v)), 32, verb)
}
// fmt_c128 formats a complex128 according to the verb.
func (f *fmt) fmt_c128(v complex128, verb rune) {
f.fmt_complex(real(v), imag(v), 64, verb)
}
// fmt_complex formats a complex number as (r+ji).
func (f *fmt) fmt_complex(r, j float64, size int, verb rune) {
f.buf.WriteByte('(')
oldPlus := f.plus
oldSpace := f.space
oldWid := f.wid
for i := 0; ; i++ {
switch verb {
case 'b':
f.formatFloat(r, 'b', 0, size)
case 'e':
f.formatFloat(r, 'e', doPrec(f, 6), size)
case 'E':
f.formatFloat(r, 'E', doPrec(f, 6), size)
case 'f', 'F':
f.formatFloat(r, 'f', doPrec(f, 6), size)
case 'g':
f.formatFloat(r, 'g', doPrec(f, -1), size)
case 'G':
f.formatFloat(r, 'G', doPrec(f, -1), size)
}
if i != 0 {
break
}
// Imaginary part always has a sign.
f.plus = true
f.space = false
f.wid = oldWid
r = j
}
f.space = oldSpace
f.plus = oldPlus
f.wid = oldWid
f.buf.Write(irparenBytes)
}