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// Copyright 2020 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package json
import (
"unicode"
"unicode/utf8"
)
// foldName returns a folded string such that foldName(x) == foldName(y)
// is similar to strings.EqualFold(x, y), but ignores underscore and dashes.
// This allows foldName to match common naming conventions.
func foldName(in []byte) []byte {
// This is inlinable to take advantage of "function outlining".
// See https://blog.filippo.io/efficient-go-apis-with-the-inliner/
var arr [32]byte // large enough for most JSON names
return appendFoldedName(arr[:0], in)
}
func appendFoldedName(out, in []byte) []byte {
for i := 0; i < len(in); {
// Handle single-byte ASCII.
if c := in[i]; c < utf8.RuneSelf {
if c != '_' && c != '-' {
if 'a' <= c && c <= 'z' {
c -= 'a' - 'A'
}
out = append(out, c)
}
i++
continue
}
// Handle multi-byte Unicode.
r, n := utf8.DecodeRune(in[i:])
out = utf8.AppendRune(out, foldRune(r))
i += n
}
return out
}
// foldRune is a variation on unicode.SimpleFold that returns the same rune
// for all runes in the same fold set.
//
// Invariant:
//
// foldRune(x) == foldRune(y) ⇔ strings.EqualFold(string(x), string(y))
func foldRune(r rune) rune {
for {
r2 := unicode.SimpleFold(r)
if r2 <= r {
return r2 // smallest character in the fold set
}
r = r2
}
}
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