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runewidth_posix.go (1968B)

      1 //go:build !windows && !js && !appengine
      2 // +build !windows,!js,!appengine
      3 
      4 package runewidth
      5 
      6 import (
      7 	"os"
      8 	"strings"
      9 )
     10 
     11 func mblen(charset string) int {
     12 	switch charset {
     13 	case "utf-8", "utf8":
     14 		return 6
     15 	case "jis":
     16 		return 8
     17 	case "eucjp":
     18 		return 3
     19 	case "euckr", "euccn", "sjis", "cp932", "cp51932", "cp936", "cp949", "cp950", "big5", "gbk", "gb2312":
     20 		return 2
     21 	}
     22 	return 1
     23 }
     24 
     25 // localeCharset extracts the charset part of a locale name of the form
     26 // "ll.CHARSET" or "ll_CC.CHARSET" (two- or three-letter language code,
     27 // optional uppercase country code). It returns "" if locale does not have
     28 // that shape.
     29 func localeCharset(locale string) string {
     30 	n := 0
     31 	for n < len(locale) && locale[n] >= 'a' && locale[n] <= 'z' {
     32 		n++
     33 	}
     34 	if n < 2 || n > 3 {
     35 		return ""
     36 	}
     37 	rest := locale[n:]
     38 	if len(rest) >= 3 && rest[0] == '_' &&
     39 		rest[1] >= 'A' && rest[1] <= 'Z' && rest[2] >= 'A' && rest[2] <= 'Z' {
     40 		rest = rest[3:]
     41 	}
     42 	if len(rest) >= 2 && rest[0] == '.' {
     43 		return rest[1:]
     44 	}
     45 	return ""
     46 }
     47 
     48 func isEastAsian(locale string) bool {
     49 	charset := strings.ToLower(locale)
     50 	if cs := localeCharset(locale); cs != "" {
     51 		charset = strings.ToLower(cs)
     52 	}
     53 
     54 	if strings.HasSuffix(charset, "@cjk_narrow") {
     55 		return false
     56 	}
     57 
     58 	for pos, b := range []byte(charset) {
     59 		if b == '@' {
     60 			charset = charset[:pos]
     61 			break
     62 		}
     63 	}
     64 	max := mblen(charset)
     65 	if max > 1 && (charset[0] != 'u' ||
     66 		strings.HasPrefix(locale, "ja") ||
     67 		strings.HasPrefix(locale, "ko") ||
     68 		strings.HasPrefix(locale, "zh")) {
     69 		return true
     70 	}
     71 	return false
     72 }
     73 
     74 // IsEastAsian return true if the current locale is CJK
     75 func IsEastAsian() bool {
     76 	locale := os.Getenv("LC_ALL")
     77 	if locale == "" {
     78 		locale = os.Getenv("LC_CTYPE")
     79 	}
     80 	if locale == "" {
     81 		locale = os.Getenv("LANG")
     82 	}
     83 
     84 	// ignore C locale
     85 	if locale == "POSIX" || locale == "C" {
     86 		return false
     87 	}
     88 	if len(locale) > 1 && locale[0] == 'C' && (locale[1] == '.' || locale[1] == '-') {
     89 		return false
     90 	}
     91 
     92 	return isEastAsian(locale)
     93 }