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stringutils.go
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stringutils.go
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// Copyright 2018 Twitch Interactive, Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License"). You may not
// use this file except in compliance with the License. A copy of the License is
// located at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// or in the "license" file accompanying this file. This file is distributed on
// an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
// express or implied. See the License for the specific language governing
// permissions and limitations under the License.
package stringutils
import (
"strings"
"unicode"
)
// Is c an ASCII lower-case letter?
func isASCIILower(c byte) bool {
return 'a' <= c && c <= 'z'
}
// Is c an ASCII digit?
func isASCIIDigit(c byte) bool {
return '0' <= c && c <= '9'
}
// CamelCase converts a string from snake_case to CamelCased.
//
// If there is an interior underscore followed by a lower case letter, drop the
// underscore and convert the letter to upper case. There is a remote
// possibility of this rewrite causing a name collision, but it's so remote
// we're prepared to pretend it's nonexistent - since the C++ generator
// lowercases names, it's extremely unlikely to have two fields with different
// capitalizations. In short, _my_field_name_2 becomes XMyFieldName_2.
func CamelCase(s string) string {
if s == "" {
return ""
}
t := make([]byte, 0, 32)
i := 0
if s[0] == '_' {
// Need a capital letter; drop the '_'.
t = append(t, 'X')
i++
}
// Invariant: if the next letter is lower case, it must be converted
// to upper case.
//
// That is, we process a word at a time, where words are marked by _ or upper
// case letter. Digits are treated as words.
for ; i < len(s); i++ {
c := s[i]
if c == '_' && i+1 < len(s) && isASCIILower(s[i+1]) {
continue // Skip the underscore in s.
}
if isASCIIDigit(c) {
t = append(t, c)
continue
}
// Assume we have a letter now - if not, it's a bogus identifier. The next
// word is a sequence of characters that must start upper case.
if isASCIILower(c) {
c ^= ' ' // Make it a capital letter.
}
t = append(t, c) // Guaranteed not lower case.
// Accept lower case sequence that follows.
for i+1 < len(s) && isASCIILower(s[i+1]) {
i++
t = append(t, s[i])
}
}
return string(t)
}
// LowerCamelCase converts a snake_case string to camelCase
func LowerCamelCase(s string) string {
t := []byte(CamelCase(s))
t[0] ^= ' '
return string(t)
}
// AlphaDigitize replaces non-letter, non-digit, non-underscore characters with
// underscore.
func AlphaDigitize(r rune) rune {
if unicode.IsLetter(r) || unicode.IsDigit(r) || r == '_' {
return r
}
return '_'
}
// CleanIdentifier makes sure s is a valid 'identifier' string: it contains only
// letters, numbers, and underscore.
func CleanIdentifier(s string) string {
return strings.Map(AlphaDigitize, s)
}
// BaseName the last path element of a slash-delimited name, with the last
// dotted suffix removed.
func BaseName(name string) string {
// First, find the last element
if i := strings.LastIndex(name, "/"); i >= 0 {
name = name[i+1:]
}
// Now drop the suffix
if i := strings.LastIndex(name, "."); i >= 0 {
name = name[0:i]
}
return name
}