Hulk did something

[bytom/vapor.git] / vendor / golang.org / x / text / cases / info.go

diff --git a/vendor/golang.org/x/text/cases/info.go b/vendor/golang.org/x/text/cases/info.go
new file mode 100644 (file)
index 0000000..3b51f03
--- /dev/null
+++ b/vendor/golang.org/x/text/cases/info.go
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+// 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:
+// http://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
+}