gtsocial-umbx

info.go (2997B)

---

 // Copyright 2015 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 cases
 
 func (c info) cccVal() info {
 	if c&exceptionBit != 0 {
 		return info(exceptions[c>>exceptionShift]) & cccMask
 	}
 	return c & cccMask
 }
 
 func (c info) cccType() info {
 	ccc := c.cccVal()
 	if ccc <= cccZero {
 		return cccZero
 	}
 	return ccc
 }
 
 // TODO: Implement full Unicode breaking algorithm:
 // 1) Implement breaking in separate package.
 // 2) Use the breaker here.
 // 3) Compare table size and performance of using the more generic breaker.
 //
 // Note that we can extend the current algorithm to be much more accurate. This
 // only makes sense, though, if the performance and/or space penalty of using
 // the generic breaker is big. Extra data will only be needed for non-cased
 // runes, which means there are sufficient bits left in the caseType.
 // ICU prohibits breaking in such cases as well.
 
 // For the purpose of title casing we use an approximation of the Unicode Word
 // Breaking algorithm defined in Annex #29:
 // https://www.unicode.org/reports/tr29/#Default_Grapheme_Cluster_Table.
 //
 // For our approximation, we group the Word Break types into the following
 // categories, with associated rules:
 //
 // 1) Letter:
 //    ALetter, Hebrew_Letter, Numeric, ExtendNumLet, Extend, Format_FE, ZWJ.
 //    Rule: Never break between consecutive runes of this category.
 //
 // 2) Mid:
 //    MidLetter, MidNumLet, Single_Quote.
 //    (Cf. case-ignorable: MidLetter, MidNumLet, Single_Quote or cat is Mn,
 //    Me, Cf, Lm or Sk).
 //    Rule: Don't break between Letter and Mid, but break between two Mids.
 //
 // 3) Break:
 //    Any other category: NewLine, MidNum, CR, LF, Double_Quote, Katakana, and
 //    Other.
 //    These categories should always result in a break between two cased letters.
 //    Rule: Always break.
 //
 // Note 1: the Katakana and MidNum categories can, in esoteric cases, result in
 // preventing a break between two cased letters. For now we will ignore this
 // (e.g. [ALetter] [ExtendNumLet] [Katakana] [ExtendNumLet] [ALetter] and
 // [ALetter] [Numeric] [MidNum] [Numeric] [ALetter].)
 //
 // Note 2: the rule for Mid is very approximate, but works in most cases. To
 // improve, we could store the categories in the trie value and use a FA to
 // manage breaks. See TODO comment above.
 //
 // Note 3: according to the spec, it is possible for the Extend category to
 // introduce breaks between other categories grouped in Letter. However, this
 // is undesirable for our purposes. ICU prevents breaks in such cases as well.
 
 // isBreak returns whether this rune should introduce a break.
 func (c info) isBreak() bool {
 	return c.cccVal() == cccBreak
 }
 
 // isLetter returns whether the rune is of break type ALetter, Hebrew_Letter,
 // Numeric, ExtendNumLet, or Extend.
 func (c info) isLetter() bool {
 	ccc := c.cccVal()
 	if ccc == cccZero {
 		return !c.isCaseIgnorable()
 	}
 	return ccc != cccBreak
 }