1// Copyright 2014 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5//go:generate go run gen.go gen_trieval.go
6
7// Package cases provides general and language-specific case mappers.
8package cases // import "golang.org/x/text/cases"
9
10import (
11 "golang.org/x/text/language"
12 "golang.org/x/text/transform"
13)
14
15// References:
16// - Unicode Reference Manual Chapter 3.13, 4.2, and 5.18.
17// - https://www.unicode.org/reports/tr29/
18// - https://www.unicode.org/Public/6.3.0/ucd/CaseFolding.txt
19// - https://www.unicode.org/Public/6.3.0/ucd/SpecialCasing.txt
20// - https://www.unicode.org/Public/6.3.0/ucd/DerivedCoreProperties.txt
21// - https://www.unicode.org/Public/6.3.0/ucd/auxiliary/WordBreakProperty.txt
22// - https://www.unicode.org/Public/6.3.0/ucd/auxiliary/WordBreakTest.txt
23// - http://userguide.icu-project.org/transforms/casemappings
24
25// TODO:
26// - Case folding
27// - Wide and Narrow?
28// - Segmenter option for title casing.
29// - ASCII fast paths
30// - Encode Soft-Dotted property within trie somehow.
31
32// A Caser transforms given input to a certain case. It implements
33// transform.Transformer.
34//
35// A Caser may be stateful and should therefore not be shared between
36// goroutines.
37type Caser struct {
38 t transform.SpanningTransformer
39}
40
41// Bytes returns a new byte slice with the result of converting b to the case
42// form implemented by c.
43func (c Caser) Bytes(b []byte) []byte {
44 b, _, _ = transform.Bytes(c.t, b)
45 return b
46}
47
48// String returns a string with the result of transforming s to the case form
49// implemented by c.
50func (c Caser) String(s string) string {
51 s, _, _ = transform.String(c.t, s)
52 return s
53}
54
55// Reset resets the Caser to be reused for new input after a previous call to
56// Transform.
57func (c Caser) Reset() { c.t.Reset() }
58
59// Transform implements the transform.Transformer interface and transforms the
60// given input to the case form implemented by c.
61func (c Caser) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
62 return c.t.Transform(dst, src, atEOF)
63}
64
65// Span implements the transform.SpanningTransformer interface.
66func (c Caser) Span(src []byte, atEOF bool) (n int, err error) {
67 return c.t.Span(src, atEOF)
68}
69
70// Upper returns a Caser for language-specific uppercasing.
71func Upper(t language.Tag, opts ...Option) Caser {
72 return Caser{makeUpper(t, getOpts(opts...))}
73}
74
75// Lower returns a Caser for language-specific lowercasing.
76func Lower(t language.Tag, opts ...Option) Caser {
77 return Caser{makeLower(t, getOpts(opts...))}
78}
79
80// Title returns a Caser for language-specific title casing. It uses an
81// approximation of the default Unicode Word Break algorithm.
82func Title(t language.Tag, opts ...Option) Caser {
83 return Caser{makeTitle(t, getOpts(opts...))}
84}
85
86// Fold returns a Caser that implements Unicode case folding. The returned Caser
87// is stateless and safe to use concurrently by multiple goroutines.
88//
89// Case folding does not normalize the input and may not preserve a normal form.
90// Use the collate or search package for more convenient and linguistically
91// sound comparisons. Use golang.org/x/text/secure/precis for string comparisons
92// where security aspects are a concern.
93func Fold(opts ...Option) Caser {
94 return Caser{makeFold(getOpts(opts...))}
95}
96
97// An Option is used to modify the behavior of a Caser.
98type Option func(o options) options
99
100// TODO: consider these options to take a boolean as well, like FinalSigma.
101// The advantage of using this approach is that other providers of a lower-case
102// algorithm could set different defaults by prefixing a user-provided slice
103// of options with their own. This is handy, for instance, for the precis
104// package which would override the default to not handle the Greek final sigma.
105
106var (
107 // NoLower disables the lowercasing of non-leading letters for a title
108 // caser.
109 NoLower Option = noLower
110
111 // Compact omits mappings in case folding for characters that would grow the
112 // input. (Unimplemented.)
113 Compact Option = compact
114)
115
116// TODO: option to preserve a normal form, if applicable?
117
118type options struct {
119 noLower bool
120 simple bool
121
122 // TODO: segmenter, max ignorable, alternative versions, etc.
123
124 ignoreFinalSigma bool
125}
126
127func getOpts(o ...Option) (res options) {
128 for _, f := range o {
129 res = f(res)
130 }
131 return
132}
133
134func noLower(o options) options {
135 o.noLower = true
136 return o
137}
138
139func compact(o options) options {
140 o.simple = true
141 return o
142}
143
144// HandleFinalSigma specifies whether the special handling of Greek final sigma
145// should be enabled. Unicode prescribes handling the Greek final sigma for all
146// locales, but standards like IDNA and PRECIS override this default.
147func HandleFinalSigma(enable bool) Option {
148 if enable {
149 return handleFinalSigma
150 }
151 return ignoreFinalSigma
152}
153
154func ignoreFinalSigma(o options) options {
155 o.ignoreFinalSigma = true
156 return o
157}
158
159func handleFinalSigma(o options) options {
160 o.ignoreFinalSigma = false
161 return o
162}