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