src

runewidth.go (7757B)

---

 package runewidth
 
 import (
 	"os"
 	"strings"
 
 	"github.com/clipperhouse/uax29/v2/graphemes"
 )
 
 //go:generate go run script/generate.go
 
 var (
 	// EastAsianWidth will be set true if the current locale is CJK
 	EastAsianWidth bool
 
 	// StrictEmojiNeutral should be set false if handle broken fonts
 	StrictEmojiNeutral bool = true
 
 	// DefaultCondition is a condition in current locale
 	DefaultCondition = &Condition{
 		EastAsianWidth:     false,
 		StrictEmojiNeutral: true,
 	}
 )
 
 func init() {
 	handleEnv()
 }
 
 func handleEnv() {
 	env := os.Getenv("RUNEWIDTH_EASTASIAN")
 	if env == "" {
 		EastAsianWidth = IsEastAsian()
 	} else {
 		EastAsianWidth = env == "1"
 	}
 	// update DefaultCondition
 	if DefaultCondition.EastAsianWidth != EastAsianWidth {
 		DefaultCondition.EastAsianWidth = EastAsianWidth
 		if len(DefaultCondition.combinedLut) > 0 {
 			DefaultCondition.combinedLut = DefaultCondition.combinedLut[:0]
 			CreateLUT()
 		}
 	}
 }
 
 type interval struct {
 	first rune
 	last  rune
 }
 
 type table []interval
 
 func inTables(r rune, ts ...table) bool {
 	for _, t := range ts {
 		if inTable(r, t) {
 			return true
 		}
 	}
 	return false
 }
 
 func inTable(r rune, t table) bool {
 	if r < t[0].first {
 		return false
 	}
 	if r > t[len(t)-1].last {
 		return false
 	}
 
 	bot := 0
 	top := len(t) - 1
 	for top >= bot {
 		mid := (bot + top) >> 1
 
 		switch {
 		case t[mid].last < r:
 			bot = mid + 1
 		case t[mid].first > r:
 			top = mid - 1
 		default:
 			return true
 		}
 	}
 
 	return false
 }
 
 var private = table{
 	{0x00E000, 0x00F8FF}, {0x0F0000, 0x0FFFFD}, {0x100000, 0x10FFFD},
 }
 
 var nonprint = table{
 	{0x0000, 0x001F}, {0x007F, 0x009F}, {0x00AD, 0x00AD},
 	{0x070F, 0x070F}, {0x180B, 0x180E}, {0x200B, 0x200F},
 	{0x2028, 0x202E}, {0x206A, 0x206F}, {0xD800, 0xDFFF},
 	{0xFEFF, 0xFEFF}, {0xFFF9, 0xFFFB}, {0xFFFE, 0xFFFF},
 }
 
 // Condition have flag EastAsianWidth whether the current locale is CJK or not.
 type Condition struct {
 	combinedLut        []byte
 	EastAsianWidth     bool
 	StrictEmojiNeutral bool
 }
 
 // NewCondition return new instance of Condition which is current locale.
 func NewCondition() *Condition {
 	return &Condition{
 		EastAsianWidth:     EastAsianWidth,
 		StrictEmojiNeutral: StrictEmojiNeutral,
 	}
 }
 
 // RuneWidth returns the number of cells in r.
 // See http://www.unicode.org/reports/tr11/
 func (c *Condition) RuneWidth(r rune) int {
 	if r < 0 || r > 0x10FFFF {
 		return 0
 	}
 	if len(c.combinedLut) > 0 {
 		return int(c.combinedLut[r>>1]>>(uint(r&1)*4)) & 3
 	}
 	// optimized version, verified by TestRuneWidthChecksums()
 	if !c.EastAsianWidth {
 		switch {
 		case r < 0x20:
 			return 0
 		case (r >= 0x7F && r <= 0x9F) || r == 0xAD: // nonprint
 			return 0
 		case r < 0x300:
 			return 1
 		case inTable(r, narrow):
 			return 1
 		case inTables(r, nonprint, combining):
 			return 0
 		case inTable(r, doublewidth):
 			return 2
 		default:
 			return 1
 		}
 	} else {
 		switch {
 		case inTables(r, nonprint, combining):
 			return 0
 		case inTable(r, narrow):
 			return 1
 		case inTables(r, ambiguous, doublewidth):
 			return 2
 		case !c.StrictEmojiNeutral && inTables(r, ambiguous, emoji, narrow):
 			return 2
 		default:
 			return 1
 		}
 	}
 }
 
 // CreateLUT will create an in-memory lookup table of 557056 bytes for faster operation.
 // This should not be called concurrently with other operations on c.
 // If options in c is changed, CreateLUT should be called again.
 func (c *Condition) CreateLUT() {
 	const max = 0x110000
 	lut := c.combinedLut
 	if len(c.combinedLut) != 0 {
 		// Remove so we don't use it.
 		c.combinedLut = nil
 	} else {
 		lut = make([]byte, max/2)
 	}
 	for i := range lut {
 		i32 := int32(i * 2)
 		x0 := c.RuneWidth(i32)
 		x1 := c.RuneWidth(i32 + 1)
 		lut[i] = uint8(x0) | uint8(x1)<<4
 	}
 	c.combinedLut = lut
 }
 
 // StringWidth return width as you can see
 func (c *Condition) StringWidth(s string) (width int) {
 	g := graphemes.FromString(s)
 	for g.Next() {
 		var chWidth int
 		for _, r := range g.Value() {
 			chWidth = c.RuneWidth(r)
 			if chWidth > 0 {
 				break // Our best guess at this point is to use the width of the first non-zero-width rune.
 			}
 		}
 		width += chWidth
 	}
 	return
 }
 
 // Truncate return string truncated with w cells
 func (c *Condition) Truncate(s string, w int, tail string) string {
 	if c.StringWidth(s) <= w {
 		return s
 	}
 	w -= c.StringWidth(tail)
 	var width int
 	pos := len(s)
 	g := graphemes.FromString(s)
 	for g.Next() {
 		var chWidth int
 		for _, r := range g.Value() {
 			chWidth = c.RuneWidth(r)
 			if chWidth > 0 {
 				break // See StringWidth() for details.
 			}
 		}
 		if width+chWidth > w {
 			pos = g.Start()
 			break
 		}
 		width += chWidth
 	}
 	return s[:pos] + tail
 }
 
 // TruncateLeft cuts w cells from the beginning of the `s`.
 func (c *Condition) TruncateLeft(s string, w int, prefix string) string {
 	if c.StringWidth(s) <= w {
 		return prefix
 	}
 
 	var width int
 	pos := len(s)
 
 	g := graphemes.FromString(s)
 	for g.Next() {
 		var chWidth int
 		for _, r := range g.Value() {
 			chWidth = c.RuneWidth(r)
 			if chWidth > 0 {
 				break // See StringWidth() for details.
 			}
 		}
 
 		if width+chWidth > w {
 			if width < w {
 				pos = g.End()
 				prefix += strings.Repeat(" ", width+chWidth-w)
 			} else {
 				pos = g.Start()
 			}
 
 			break
 		}
 
 		width += chWidth
 	}
 
 	return prefix + s[pos:]
 }
 
 // Wrap return string wrapped with w cells
 func (c *Condition) Wrap(s string, w int) string {
 	width := 0
 	out := ""
 	for _, r := range s {
 		cw := c.RuneWidth(r)
 		if r == '\n' {
 			out += string(r)
 			width = 0
 			continue
 		} else if width+cw > w {
 			out += "\n"
 			width = 0
 			out += string(r)
 			width += cw
 			continue
 		}
 		out += string(r)
 		width += cw
 	}
 	return out
 }
 
 // FillLeft return string filled in left by spaces in w cells
 func (c *Condition) FillLeft(s string, w int) string {
 	width := c.StringWidth(s)
 	count := w - width
 	if count > 0 {
 		b := make([]byte, count)
 		for i := range b {
 			b[i] = ' '
 		}
 		return string(b) + s
 	}
 	return s
 }
 
 // FillRight return string filled in left by spaces in w cells
 func (c *Condition) FillRight(s string, w int) string {
 	width := c.StringWidth(s)
 	count := w - width
 	if count > 0 {
 		b := make([]byte, count)
 		for i := range b {
 			b[i] = ' '
 		}
 		return s + string(b)
 	}
 	return s
 }
 
 // RuneWidth returns the number of cells in r.
 // See http://www.unicode.org/reports/tr11/
 func RuneWidth(r rune) int {
 	return DefaultCondition.RuneWidth(r)
 }
 
 // IsAmbiguousWidth returns whether is ambiguous width or not.
 func IsAmbiguousWidth(r rune) bool {
 	return inTables(r, private, ambiguous)
 }
 
 // IsNeutralWidth returns whether is neutral width or not.
 func IsNeutralWidth(r rune) bool {
 	return inTable(r, neutral)
 }
 
 // StringWidth return width as you can see
 func StringWidth(s string) (width int) {
 	return DefaultCondition.StringWidth(s)
 }
 
 // Truncate return string truncated with w cells
 func Truncate(s string, w int, tail string) string {
 	return DefaultCondition.Truncate(s, w, tail)
 }
 
 // TruncateLeft cuts w cells from the beginning of the `s`.
 func TruncateLeft(s string, w int, prefix string) string {
 	return DefaultCondition.TruncateLeft(s, w, prefix)
 }
 
 // Wrap return string wrapped with w cells
 func Wrap(s string, w int) string {
 	return DefaultCondition.Wrap(s, w)
 }
 
 // FillLeft return string filled in left by spaces in w cells
 func FillLeft(s string, w int) string {
 	return DefaultCondition.FillLeft(s, w)
 }
 
 // FillRight return string filled in left by spaces in w cells
 func FillRight(s string, w int) string {
 	return DefaultCondition.FillRight(s, w)
 }
 
 // CreateLUT will create an in-memory lookup table of 557055 bytes for faster operation.
 // This should not be called concurrently with other operations.
 func CreateLUT() {
 	if len(DefaultCondition.combinedLut) > 0 {
 		return
 	}
 	DefaultCondition.CreateLUT()
 }