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utils.go
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utils.go
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// Copyright (c) 2022 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package protopluginv2
// goCamelCase camel-cases a protobuf name for use as a Go identifier.
//
// If there is an interior underscore followed by a lower case letter,
// drop the underscore and convert the letter to upper case.
func goCamelCase(s string) string {
// 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.
var b []byte
for i := 0; i < len(s); i++ {
c := s[i]
switch {
case c == '.' && i+1 < len(s) && isASCIILower(s[i+1]):
// Skip over '.' in ".{{lowercase}}".
case c == '.':
b = append(b, '_') // convert '.' to '_'
case c == '_' && (i == 0 || s[i-1] == '.'):
// Convert initial '_' to ensure we start with a capital letter.
// Do the same for '_' after '.' to match historic behavior.
b = append(b, 'X') // convert '_' to 'X'
case c == '_' && i+1 < len(s) && isASCIILower(s[i+1]):
// Skip over '_' in "_{{lowercase}}".
case isASCIIDigit(c):
b = append(b, c)
default:
// 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 -= 'a' - 'A' // convert lowercase to uppercase
}
b = append(b, c)
// Accept lower case sequence that follows.
for ; i+1 < len(s) && isASCIILower(s[i+1]); i++ {
b = append(b, s[i+1])
}
}
}
return string(b)
}
func isASCIILower(c byte) bool {
return 'a' <= c && c <= 'z'
}
func isASCIIDigit(c byte) bool {
return '0' <= c && c <= '9'
}