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130 lines
3.8 KiB
130 lines
3.8 KiB
// Copyright 2014 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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//go:generate go run gen.go gen_trieval.go
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// Package cases provides general and language-specific case mappers.
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package cases // import "golang.org/x/text/cases"
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import (
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"golang.org/x/text/language"
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"golang.org/x/text/transform"
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)
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// References:
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// - Unicode Reference Manual Chapter 3.13, 4.2, and 5.18.
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// - http://www.unicode.org/reports/tr29/
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// - http://www.unicode.org/Public/6.3.0/ucd/CaseFolding.txt
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// - http://www.unicode.org/Public/6.3.0/ucd/SpecialCasing.txt
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// - http://www.unicode.org/Public/6.3.0/ucd/DerivedCoreProperties.txt
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// - http://www.unicode.org/Public/6.3.0/ucd/auxiliary/WordBreakProperty.txt
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// - http://www.unicode.org/Public/6.3.0/ucd/auxiliary/WordBreakTest.txt
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// - http://userguide.icu-project.org/transforms/casemappings
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// TODO:
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// - Case folding
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// - Wide and Narrow?
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// - Segmenter option for title casing.
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// - ASCII fast paths
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// - Encode Soft-Dotted property within trie somehow.
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// A Caser transforms given input to a certain case. It implements
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// transform.Transformer.
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//
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// A Caser may be stateful and should therefore not be shared between
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// goroutines.
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type Caser struct {
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t transform.Transformer
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}
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// Bytes returns a new byte slice with the result of converting b to the case
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// form implemented by c.
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func (c Caser) Bytes(b []byte) []byte {
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b, _, _ = transform.Bytes(c.t, b)
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return b
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}
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// String returns a string with the result of transforming s to the case form
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// implemented by c.
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func (c Caser) String(s string) string {
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s, _, _ = transform.String(c.t, s)
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return s
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}
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// Reset resets the Caser to be reused for new input after a previous call to
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// Transform.
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func (c Caser) Reset() { c.t.Reset() }
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// Transform implements the Transformer interface and transforms the given input
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// to the case form implemented by c.
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func (c Caser) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
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return c.t.Transform(dst, src, atEOF)
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}
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// Upper returns a Caser for language-specific uppercasing.
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func Upper(t language.Tag, opts ...Option) Caser {
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return Caser{makeUpper(t, getOpts(opts...))}
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}
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// Lower returns a Caser for language-specific lowercasing.
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func Lower(t language.Tag, opts ...Option) Caser {
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return Caser{makeLower(t, getOpts(opts...))}
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}
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// Title returns a Caser for language-specific title casing. It uses an
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// approximation of the default Unicode Word Break algorithm.
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func Title(t language.Tag, opts ...Option) Caser {
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return Caser{makeTitle(t, getOpts(opts...))}
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}
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// Fold returns a Caser that implements Unicode case folding. The returned Caser
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// is stateless and safe to use concurrently by multiple goroutines.
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//
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// Case folding does not normalize the input and may not preserve a normal form.
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// Use the collate or search package for more convenient and linguistically
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// sound comparisons. Use unicode/precis for string comparisons where security
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// aspects are a concern.
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func Fold(opts ...Option) Caser {
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return Caser{makeFold(getOpts(opts...))}
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}
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// An Option is used to modify the behavior of a Caser.
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type Option func(o *options)
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var (
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// NoLower disables the lowercasing of non-leading letters for a title
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// caser.
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NoLower Option = noLower
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// Compact omits mappings in case folding for characters that would grow the
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// input. (Unimplemented.)
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Compact Option = compact
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)
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// TODO: option to preserve a normal form, if applicable?
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type options struct {
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noLower bool
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simple bool
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// TODO: segmenter, max ignorable, alternative versions, etc.
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noFinalSigma bool // Only used for testing.
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}
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func getOpts(o ...Option) (res options) {
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for _, f := range o {
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f(&res)
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}
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return
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}
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func noLower(o *options) {
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o.noLower = true
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}
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func compact(o *options) {
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o.simple = true
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}
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