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package casing
import (
"path/filepath"
"strings"
)
// Camel returns the CamelCased name.
//
// This was moved from the now deprecated github.com/golang/protobuf/protoc-gen-go/generator package
//
// 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 Camel(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)
}
// CamelIdentifier returns the CamelCased identifier without affecting the package name/path if any.
func CamelIdentifier(s string) string {
const dot = "."
if !strings.Contains(s, dot) {
return Camel(s)
}
identifier := filepath.Ext(s)
path := strings.TrimSuffix(s, identifier)
identifier = strings.TrimPrefix(identifier, dot)
return path + dot + Camel(identifier)
}
// JSONCamelCase converts a snake_case identifier to a camelCase identifier,
// according to the protobuf JSON specification.
func JSONCamelCase(s string) string {
var b []byte
var wasUnderscore bool
for i := 0; i < len(s); i++ { // proto identifiers are always ASCII
c := s[i]
if c != '_' {
if wasUnderscore && isASCIILower(c) {
c -= 'a' - 'A' // convert to uppercase
}
b = append(b, c)
}
wasUnderscore = c == '_'
}
return string(b)
}
// And now lots of helper functions.
// 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'
}
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