1// Copyright 2015 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// Package tag contains functionality handling tags and related data.
6package tag // import "golang.org/x/text/internal/tag"
7
8import "sort"
9
10// An Index converts tags to a compact numeric value.
11//
12// All elements are of size 4. Tags may be up to 4 bytes long. Excess bytes can
13// be used to store additional information about the tag.
14type Index string
15
16// Elem returns the element data at the given index.
17func (s Index) Elem(x int) string {
18	return string(s[x*4 : x*4+4])
19}
20
21// Index reports the index of the given key or -1 if it could not be found.
22// Only the first len(key) bytes from the start of the 4-byte entries will be
23// considered for the search and the first match in Index will be returned.
24func (s Index) Index(key []byte) int {
25	n := len(key)
26	// search the index of the first entry with an equal or higher value than
27	// key in s.
28	index := sort.Search(len(s)/4, func(i int) bool {
29		return cmp(s[i*4:i*4+n], key) != -1
30	})
31	i := index * 4
32	if cmp(s[i:i+len(key)], key) != 0 {
33		return -1
34	}
35	return index
36}
37
38// Next finds the next occurrence of key after index x, which must have been
39// obtained from a call to Index using the same key. It returns x+1 or -1.
40func (s Index) Next(key []byte, x int) int {
41	if x++; x*4 < len(s) && cmp(s[x*4:x*4+len(key)], key) == 0 {
42		return x
43	}
44	return -1
45}
46
47// cmp returns an integer comparing a and b lexicographically.
48func cmp(a Index, b []byte) int {
49	n := len(a)
50	if len(b) < n {
51		n = len(b)
52	}
53	for i, c := range b[:n] {
54		switch {
55		case a[i] > c:
56			return 1
57		case a[i] < c:
58			return -1
59		}
60	}
61	switch {
62	case len(a) < len(b):
63		return -1
64	case len(a) > len(b):
65		return 1
66	}
67	return 0
68}
69
70// Compare returns an integer comparing a and b lexicographically.
71func Compare(a string, b []byte) int {
72	return cmp(Index(a), b)
73}
74
75// FixCase reformats b to the same pattern of cases as form.
76// If returns false if string b is malformed.
77func FixCase(form string, b []byte) bool {
78	if len(form) != len(b) {
79		return false
80	}
81	for i, c := range b {
82		if form[i] <= 'Z' {
83			if c >= 'a' {
84				c -= 'z' - 'Z'
85			}
86			if c < 'A' || 'Z' < c {
87				return false
88			}
89		} else {
90			if c <= 'Z' {
91				c += 'z' - 'Z'
92			}
93			if c < 'a' || 'z' < c {
94				return false
95			}
96		}
97		b[i] = c
98	}
99	return true
100}
101