exp/norm: API for normalization library.

R=r, r, mpvl, rsc
CC=golang-dev
https://golang.org/cl/4678041

src/pkg/exp/norm/normalize.go

+// Copyright 2011 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 form contains types and functions for normalizing Unicode strings.
+package norm
+
+// A Form denotes a canonical representation of Unicode code points.
+// The Unicode-defined normalization and equivalence forms are:
+//
+//   NFC   Unicode Normalization Form C
+//   NFD   Unicode Normalization Form D
+//   NFKC  Unicode Normalization Form KC
+//   NFKD  Unicode Normalization Form KD
+//
+// For a Form f, this documentation uses the notation f(x) to mean
+// the bytes or string x converted to the given form.
+// A position n in x is called a boundary if conversion to the form can
+// proceed independently on both sides:
+//   f(x) == append(f(x[0:n]), f(x[n:])...)
+//
+// References: http://unicode.org/reports/tr15/ and
+// http://unicode.org/notes/tn5/.
+type Form int
+
+const (
+	NFC Form = iota
+	NFD
+	NFKC
+	NFKD
+)
+
+// Bytes returns f(b). May return b if f(b) = b.
+func (f Form) Bytes(b []byte) []byte
+
+// String returns f(s).
+func (f Form) String(s string) string
+
+// IsNormal returns true if b == f(b).
+func (f Form) IsNormal(b []byte) bool
+
+// IsNormalString returns true if s == f(s).
+func (f Form) IsNormalString(s string) bool
+
+// Append returns f(append(out, b...)).
+// The buffer out must be empty or equal to f(out).
+func (f Form) Append(out, b []byte) []byte
+
+// AppendString returns f(append(out, []byte(s))).
+// The buffer out must be empty or equal to f(out).
+func (f Form) AppendString(out []byte, s string) []byte
+
+// QuickSpan returns a boundary n such that b[0:n] == f(b[0:n]).
+// It is not guaranteed to return the largest such n.
+func (f Form) QuickSpan(b []byte) int
+
+// QuickSpanString returns a boundary n such that b[0:n] == f(s[0:n]).
+// It is not guaranteed to return the largest such n.
+func (f Form) QuickSpanString(s string) int
+
+// FirstBoundary returns the position i of the first boundary in b.
+// It returns len(b), false if b contains no boundaries.
+func (f Form) FirstBoundary(b []byte) (i int, ok bool)
+
+// FirstBoundaryInString return the position i of the first boundary in s.
+// It returns len(s), false if s contains no boundaries.
+func (f Form) FirstBoundaryInString(s string) (i int, ok bool)
+
+// LastBoundaryIn returns the position i of the last boundary in b.
+// It returns 0, false if b contains no boundary.
+func (f Form) LastBoundary(b []byte) (i int, ok bool)
+
+// LastBoundaryInString returns the position i of the last boundary in s.
+// It returns 0, false if s contains no boundary.
+func (f Form) LastBoundaryInString(s string) (i int, ok bool)