taldir

format.go (12261B)

---

 // Copyright 2017 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 message
 
 import (
 	"bytes"
 	"strconv"
 	"unicode/utf8"
 
 	"golang.org/x/text/internal/format"
 )
 
 const (
 	ldigits = "0123456789abcdefx"
 	udigits = "0123456789ABCDEFX"
 )
 
 const (
 	signed   = true
 	unsigned = false
 )
 
 // A formatInfo is the raw formatter used by Printf etc.
 // It prints into a buffer that must be set up separately.
 type formatInfo struct {
 	buf *bytes.Buffer
 
 	format.Parser
 
 	// intbuf is large enough to store %b of an int64 with a sign and
 	// avoids padding at the end of the struct on 32 bit architectures.
 	intbuf [68]byte
 }
 
 func (f *formatInfo) init(buf *bytes.Buffer) {
 	f.ClearFlags()
 	f.buf = buf
 }
 
 // writePadding generates n bytes of padding.
 func (f *formatInfo) writePadding(n int) {
 	if n <= 0 { // No padding bytes needed.
 		return
 	}
 	f.buf.Grow(n)
 	// Decide which byte the padding should be filled with.
 	padByte := byte(' ')
 	if f.Zero {
 		padByte = byte('0')
 	}
 	// Fill padding with padByte.
 	for i := 0; i < n; i++ {
 		f.buf.WriteByte(padByte) // TODO: make more efficient.
 	}
 }
 
 // pad appends b to f.buf, padded on left (!f.minus) or right (f.minus).
 func (f *formatInfo) pad(b []byte) {
 	if !f.WidthPresent || f.Width == 0 {
 		f.buf.Write(b)
 		return
 	}
 	width := f.Width - utf8.RuneCount(b)
 	if !f.Minus {
 		// left padding
 		f.writePadding(width)
 		f.buf.Write(b)
 	} else {
 		// right padding
 		f.buf.Write(b)
 		f.writePadding(width)
 	}
 }
 
 // padString appends s to f.buf, padded on left (!f.minus) or right (f.minus).
 func (f *formatInfo) padString(s string) {
 	if !f.WidthPresent || f.Width == 0 {
 		f.buf.WriteString(s)
 		return
 	}
 	width := f.Width - utf8.RuneCountInString(s)
 	if !f.Minus {
 		// left padding
 		f.writePadding(width)
 		f.buf.WriteString(s)
 	} else {
 		// right padding
 		f.buf.WriteString(s)
 		f.writePadding(width)
 	}
 }
 
 // fmt_boolean formats a boolean.
 func (f *formatInfo) fmt_boolean(v bool) {
 	if v {
 		f.padString("true")
 	} else {
 		f.padString("false")
 	}
 }
 
 // fmt_unicode formats a uint64 as "U+0078" or with f.sharp set as "U+0078 'x'".
 func (f *formatInfo) fmt_unicode(u uint64) {
 	buf := f.intbuf[0:]
 
 	// With default precision set the maximum needed buf length is 18
 	// for formatting -1 with %#U ("U+FFFFFFFFFFFFFFFF") which fits
 	// into the already allocated intbuf with a capacity of 68 bytes.
 	prec := 4
 	if f.PrecPresent && f.Prec > 4 {
 		prec = f.Prec
 		// Compute space needed for "U+" , number, " '", character, "'".
 		width := 2 + prec + 2 + utf8.UTFMax + 1
 		if width > len(buf) {
 			buf = make([]byte, width)
 		}
 	}
 
 	// Format into buf, ending at buf[i]. Formatting numbers is easier right-to-left.
 	i := len(buf)
 
 	// For %#U we want to add a space and a quoted character at the end of the buffer.
 	if f.Sharp && u <= utf8.MaxRune && strconv.IsPrint(rune(u)) {
 		i--
 		buf[i] = '\''
 		i -= utf8.RuneLen(rune(u))
 		utf8.EncodeRune(buf[i:], rune(u))
 		i--
 		buf[i] = '\''
 		i--
 		buf[i] = ' '
 	}
 	// Format the Unicode code point u as a hexadecimal number.
 	for u >= 16 {
 		i--
 		buf[i] = udigits[u&0xF]
 		prec--
 		u >>= 4
 	}
 	i--
 	buf[i] = udigits[u]
 	prec--
 	// Add zeros in front of the number until requested precision is reached.
 	for prec > 0 {
 		i--
 		buf[i] = '0'
 		prec--
 	}
 	// Add a leading "U+".
 	i--
 	buf[i] = '+'
 	i--
 	buf[i] = 'U'
 
 	oldZero := f.Zero
 	f.Zero = false
 	f.pad(buf[i:])
 	f.Zero = oldZero
 }
 
 // fmt_integer formats signed and unsigned integers.
 func (f *formatInfo) fmt_integer(u uint64, base int, isSigned bool, digits string) {
 	negative := isSigned && int64(u) < 0
 	if negative {
 		u = -u
 	}
 
 	buf := f.intbuf[0:]
 	// The already allocated f.intbuf with a capacity of 68 bytes
 	// is large enough for integer formatting when no precision or width is set.
 	if f.WidthPresent || f.PrecPresent {
 		// Account 3 extra bytes for possible addition of a sign and "0x".
 		width := 3 + f.Width + f.Prec // wid and prec are always positive.
 		if width > len(buf) {
 			// We're going to need a bigger boat.
 			buf = make([]byte, width)
 		}
 	}
 
 	// Two ways to ask for extra leading zero digits: %.3d or %03d.
 	// If both are specified the f.zero flag is ignored and
 	// padding with spaces is used instead.
 	prec := 0
 	if f.PrecPresent {
 		prec = f.Prec
 		// Precision of 0 and value of 0 means "print nothing" but padding.
 		if prec == 0 && u == 0 {
 			oldZero := f.Zero
 			f.Zero = false
 			f.writePadding(f.Width)
 			f.Zero = oldZero
 			return
 		}
 	} else if f.Zero && f.WidthPresent {
 		prec = f.Width
 		if negative || f.Plus || f.Space {
 			prec-- // leave room for sign
 		}
 	}
 
 	// Because printing is easier right-to-left: format u into buf, ending at buf[i].
 	// 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 u has 64 bits.
 	i := len(buf)
 	// Use constants for the division and modulo for more efficient code.
 	// Switch cases ordered by popularity.
 	switch base {
 	case 10:
 		for u >= 10 {
 			i--
 			next := u / 10
 			buf[i] = byte('0' + u - next*10)
 			u = next
 		}
 	case 16:
 		for u >= 16 {
 			i--
 			buf[i] = digits[u&0xF]
 			u >>= 4
 		}
 	case 8:
 		for u >= 8 {
 			i--
 			buf[i] = byte('0' + u&7)
 			u >>= 3
 		}
 	case 2:
 		for u >= 2 {
 			i--
 			buf[i] = byte('0' + u&1)
 			u >>= 1
 		}
 	default:
 		panic("fmt: unknown base; can't happen")
 	}
 	i--
 	buf[i] = digits[u]
 	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:
 			// Add a leading 0x or 0X.
 			i--
 			buf[i] = digits[16]
 			i--
 			buf[i] = '0'
 		}
 	}
 
 	if negative {
 		i--
 		buf[i] = '-'
 	} else if f.Plus {
 		i--
 		buf[i] = '+'
 	} else if f.Space {
 		i--
 		buf[i] = ' '
 	}
 
 	// Left padding with zeros has already been handled like precision earlier
 	// or the f.zero flag is ignored due to an explicitly set precision.
 	oldZero := f.Zero
 	f.Zero = false
 	f.pad(buf[i:])
 	f.Zero = oldZero
 }
 
 // truncate truncates the string to the specified precision, if present.
 func (f *formatInfo) truncate(s string) string {
 	if f.PrecPresent {
 		n := f.Prec
 		for i := range s {
 			n--
 			if n < 0 {
 				return s[:i]
 			}
 		}
 	}
 	return s
 }
 
 // fmt_s formats a string.
 func (f *formatInfo) 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 *formatInfo) fmt_sbx(s string, b []byte, digits string) {
 	length := len(b)
 	if b == nil {
 		// No byte slice present. Assume string s should be encoded.
 		length = len(s)
 	}
 	// Set length to not process more bytes than the precision demands.
 	if f.PrecPresent && f.Prec < length {
 		length = f.Prec
 	}
 	// Compute width of the encoding taking into account the f.sharp and f.space flag.
 	width := 2 * length
 	if width > 0 {
 		if f.Space {
 			// Each element encoded by two hexadecimals will get a leading 0x or 0X.
 			if f.Sharp {
 				width *= 2
 			}
 			// Elements will be separated by a space.
 			width += length - 1
 		} else if f.Sharp {
 			// Only a leading 0x or 0X will be added for the whole string.
 			width += 2
 		}
 	} else { // The byte slice or string that should be encoded is empty.
 		if f.WidthPresent {
 			f.writePadding(f.Width)
 		}
 		return
 	}
 	// Handle padding to the left.
 	if f.WidthPresent && f.Width > width && !f.Minus {
 		f.writePadding(f.Width - width)
 	}
 	// Write the encoding directly into the output buffer.
 	buf := f.buf
 	if f.Sharp {
 		// Add leading 0x or 0X.
 		buf.WriteByte('0')
 		buf.WriteByte(digits[16])
 	}
 	var c byte
 	for i := 0; i < length; i++ {
 		if f.Space && i > 0 {
 			// Separate elements with a space.
 			buf.WriteByte(' ')
 			if f.Sharp {
 				// Add leading 0x or 0X for each element.
 				buf.WriteByte('0')
 				buf.WriteByte(digits[16])
 			}
 		}
 		if b != nil {
 			c = b[i] // Take a byte from the input byte slice.
 		} else {
 			c = s[i] // Take a byte from the input string.
 		}
 		// Encode each byte as two hexadecimal digits.
 		buf.WriteByte(digits[c>>4])
 		buf.WriteByte(digits[c&0xF])
 	}
 	// Handle padding to the right.
 	if f.WidthPresent && f.Width > width && f.Minus {
 		f.writePadding(f.Width - width)
 	}
 }
 
 // fmt_sx formats a string as a hexadecimal encoding of its bytes.
 func (f *formatInfo) fmt_sx(s, digits string) {
 	f.fmt_sbx(s, nil, digits)
 }
 
 // fmt_bx formats a byte slice as a hexadecimal encoding of its bytes.
 func (f *formatInfo) fmt_bx(b []byte, digits string) {
 	f.fmt_sbx("", b, digits)
 }
 
 // fmt_q formats a string as a double-quoted, escaped Go string constant.
 // If f.sharp is set a raw (backquoted) string may be returned instead
 // if the string does not contain any control characters other than tab.
 func (f *formatInfo) fmt_q(s string) {
 	s = f.truncate(s)
 	if f.Sharp && strconv.CanBackquote(s) {
 		f.padString("`" + s + "`")
 		return
 	}
 	buf := f.intbuf[:0]
 	if f.Plus {
 		f.pad(strconv.AppendQuoteToASCII(buf, s))
 	} else {
 		f.pad(strconv.AppendQuote(buf, s))
 	}
 }
 
 // fmt_c formats an integer as a Unicode character.
 // If the character is not valid Unicode, it will print '\ufffd'.
 func (f *formatInfo) fmt_c(c uint64) {
 	r := rune(c)
 	if c > utf8.MaxRune {
 		r = utf8.RuneError
 	}
 	buf := f.intbuf[:0]
 	w := utf8.EncodeRune(buf[:utf8.UTFMax], r)
 	f.pad(buf[:w])
 }
 
 // fmt_qc formats an integer as a single-quoted, escaped Go character constant.
 // If the character is not valid Unicode, it will print '\ufffd'.
 func (f *formatInfo) fmt_qc(c uint64) {
 	r := rune(c)
 	if c > utf8.MaxRune {
 		r = utf8.RuneError
 	}
 	buf := f.intbuf[:0]
 	if f.Plus {
 		f.pad(strconv.AppendQuoteRuneToASCII(buf, r))
 	} else {
 		f.pad(strconv.AppendQuoteRune(buf, r))
 	}
 }
 
 // fmt_float formats a float64. It assumes that verb is a valid format specifier
 // for strconv.AppendFloat and therefore fits into a byte.
 func (f *formatInfo) fmt_float(v float64, size int, verb rune, prec int) {
 	// Explicit precision in format specifier overrules default precision.
 	if f.PrecPresent {
 		prec = f.Prec
 	}
 	// Format number, reserving space for leading + sign if needed.
 	num := strconv.AppendFloat(f.intbuf[:1], v, byte(verb), prec, size)
 	if num[1] == '-' || num[1] == '+' {
 		num = num[1:]
 	} else {
 		num[0] = '+'
 	}
 	// f.space means to add a leading space instead of a "+" sign unless
 	// the sign is explicitly asked for by f.plus.
 	if f.Space && num[0] == '+' && !f.Plus {
 		num[0] = ' '
 	}
 	// Special handling for infinities and NaN,
 	// which don't look like a number so shouldn't be padded with zeros.
 	if num[1] == 'I' || num[1] == 'N' {
 		oldZero := f.Zero
 		f.Zero = false
 		// Remove sign before NaN if not asked for.
 		if num[1] == 'N' && !f.Space && !f.Plus {
 			num = num[1:]
 		}
 		f.pad(num)
 		f.Zero = oldZero
 		return
 	}
 	// The sharp flag forces printing a decimal point for non-binary formats
 	// and retains trailing zeros, which we may need to restore.
 	if f.Sharp && verb != 'b' {
 		digits := 0
 		switch verb {
 		case 'v', 'g', 'G':
 			digits = prec
 			// If no precision is set explicitly use a precision of 6.
 			if digits == -1 {
 				digits = 6
 			}
 		}
 
 		// Buffer pre-allocated with enough room for
 		// exponent notations of the form "e+123".
 		var tailBuf [5]byte
 		tail := tailBuf[:0]
 
 		hasDecimalPoint := false
 		// Starting from i = 1 to skip sign at num[0].
 		for i := 1; i < len(num); i++ {
 			switch num[i] {
 			case '.':
 				hasDecimalPoint = true
 			case 'e', 'E':
 				tail = append(tail, num[i:]...)
 				num = num[:i]
 			default:
 				digits--
 			}
 		}
 		if !hasDecimalPoint {
 			num = append(num, '.')
 		}
 		for digits > 0 {
 			num = append(num, '0')
 			digits--
 		}
 		num = append(num, tail...)
 	}
 	// We want a sign if asked for and if the sign is not positive.
 	if f.Plus || num[0] != '+' {
 		// If we're zero padding to the left we want the sign before the leading zeros.
 		// Achieve this by writing the sign out and then padding the unsigned number.
 		if f.Zero && f.WidthPresent && f.Width > len(num) {
 			f.buf.WriteByte(num[0])
 			f.writePadding(f.Width - len(num))
 			f.buf.Write(num[1:])
 			return
 		}
 		f.pad(num)
 		return
 	}
 	// No sign to show and the number is positive; just print the unsigned number.
 	f.pad(num[1:])
 }