Adding upstream version 0.0~git20250520.a1d9079+dfsg.

Signed-off-by: Daniel Baumann <daniel@debian.org>

bind/seq/string.go

@@ -0,0 +1,49 @@
+// Copyright 2014 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 seq
+
+import "unicode/utf16"
+
+// Based heavily on package unicode/utf16 from the Go standard library.
+
+const (
+	replacementChar = '\uFFFD'     // Unicode replacement character
+	maxRune         = '\U0010FFFF' // Maximum valid Unicode code point.
+)
+
+const (
+	// 0xd800-0xdc00 encodes the high 10 bits of a pair.
+	// 0xdc00-0xe000 encodes the low 10 bits of a pair.
+	// the value is those 20 bits plus 0x10000.
+	surr1 = 0xd800
+	surr2 = 0xdc00
+	surr3 = 0xe000
+
+	surrSelf = 0x10000
+)
+
+// UTF16Encode utf16 encodes s into chars. It returns the resulting
+// length in units of uint16. It is assumed that the chars slice
+// has enough room for the encoded string.
+func UTF16Encode(s string, chars []uint16) int {
+	n := 0
+	for _, v := range s {
+		switch {
+		case v < 0, surr1 <= v && v < surr3, v > maxRune:
+			v = replacementChar
+			fallthrough
+		case v < surrSelf:
+			chars[n] = uint16(v)
+			n += 1
+		default:
+			// surrogate pair, two uint16 values
+			r1, r2 := utf16.EncodeRune(v)
+			chars[n] = uint16(r1)
+			chars[n+1] = uint16(r2)
+			n += 2
+		}
+	}
+	return n
+}