text: // Copyright 2015 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 unicode
  
  import (
  	"testing"
  
  	"golang.org/x/text/encoding"
  	"golang.org/x/text/encoding/charmap"
  	"golang.org/x/text/encoding/internal/enctest"
  	"golang.org/x/text/transform"
  )
  
  func TestBasics(t *testing.T) {
  	testCases := []struct {
  		e         encoding.Encoding
  		encPrefix string
  		encSuffix string
  		encoded   string
  		utf8      string
  	}{{
  		e:       utf16BEIB,
  		encoded: "\x00\x57\x00\xe4\xd8\x35\xdd\x65",
  		utf8:    "\x57\u00e4\U0001d565",
  	}, {
  		e:         utf16BEEB,
  		encPrefix: "\xfe\xff",
  		encoded:   "\x00\x57\x00\xe4\xd8\x35\xdd\x65",
  		utf8:      "\x57\u00e4\U0001d565",
  	}, {
  		e:       utf16LEIB,
  		encoded: "\x57\x00\xe4\x00\x35\xd8\x65\xdd",
  		utf8:    "\x57\u00e4\U0001d565",
  	}, {
  		e:         utf16LEEB,
  		encPrefix: "\xff\xfe",
  		encoded:   "\x57\x00\xe4\x00\x35\xd8\x65\xdd",
  		utf8:      "\x57\u00e4\U0001d565",
  	}}
  
  	for _, tc := range testCases {
  		enctest.TestEncoding(t, tc.e, tc.encoded, tc.utf8, tc.encPrefix, tc.encSuffix)
  	}
  }
  
  func TestFiles(t *testing.T) {
  	enctest.TestFile(t, UTF8)
  	enctest.TestFile(t, utf16LEIB)
  }
  
  func BenchmarkEncoding(b *testing.B) {
  	enctest.Benchmark(b, UTF8)
  	enctest.Benchmark(b, utf16LEIB)
  }
  
  var (
  	utf16LEIB = UTF16(LittleEndian, IgnoreBOM) // UTF-16LE (atypical interpretation)
  	utf16LEUB = UTF16(LittleEndian, UseBOM)    // UTF-16, LE
  	utf16LEEB = UTF16(LittleEndian, ExpectBOM) // UTF-16, LE, Expect
  	utf16BEIB = UTF16(BigEndian, IgnoreBOM)    // UTF-16BE (atypical interpretation)
  	utf16BEUB = UTF16(BigEndian, UseBOM)       // UTF-16 default
  	utf16BEEB = UTF16(BigEndian, ExpectBOM)    // UTF-16 Expect
  )
  
  func TestUTF16(t *testing.T) {
  	testCases := []struct {
  		desc    string
  		src     string
  		notEOF  bool // the inverse of atEOF
  		sizeDst int
  		want    string
  		nSrc    int
  		err     error
  		t       transform.Transformer
  	}{{
  		desc: "utf-16 IgnoreBOM dec: empty string",
  		t:    utf16BEIB.NewDecoder(),
  	}, {
  		desc: "utf-16 UseBOM dec: empty string",
  		t:    utf16BEUB.NewDecoder(),
  	}, {
  		desc: "utf-16 ExpectBOM dec: empty string",
  		err:  ErrMissingBOM,
  		t:    utf16BEEB.NewDecoder(),
  	}, {
  		desc:    "utf-16 dec: BOM determines encoding BE (RFC 2781:3.3)",
  		src:     "\xFE\xFF\xD8\x08\xDF\x45\x00\x3D\x00\x52\x00\x61",
  		sizeDst: 100,
  		want:    "\U00012345=Ra",
  		nSrc:    12,
  		t:       utf16BEUB.NewDecoder(),
  	}, {
  		desc:    "utf-16 dec: BOM determines encoding LE (RFC 2781:3.3)",
  		src:     "\xFF\xFE\x08\xD8\x45\xDF\x3D\x00\x52\x00\x61\x00",
  		sizeDst: 100,
  		want:    "\U00012345=Ra",
  		nSrc:    12,
  		t:       utf16LEUB.NewDecoder(),
  	}, {
  		desc:    "utf-16 dec: BOM determines encoding LE, change default (RFC 2781:3.3)",
  		src:     "\xFF\xFE\x08\xD8\x45\xDF\x3D\x00\x52\x00\x61\x00",
  		sizeDst: 100,
  		want:    "\U00012345=Ra",
  		nSrc:    12,
  		t:       utf16BEUB.NewDecoder(),
  	}, {
  		desc:    "utf-16 dec: Fail on missing BOM when required",
  		src:     "\x08\xD8\x45\xDF\x3D\x00\xFF\xFE\xFE\xFF\x00\x52\x00\x61",
  		sizeDst: 100,
  		want:    "",
  		nSrc:    0,
  		err:     ErrMissingBOM,
  		t:       utf16BEEB.NewDecoder(),
  	}, {
  		desc:    "utf-16 dec: SHOULD interpret text as big-endian when BOM not present (RFC 2781:4.3)",
  		src:     "\xD8\x08\xDF\x45\x00\x3D\x00\x52\x00\x61",
  		sizeDst: 100,
  		want:    "\U00012345=Ra",
  		nSrc:    10,
  		t:       utf16BEUB.NewDecoder(),
  	}, {
  		// This is an error according to RFC 2781. But errors in RFC 2781 are
  		// open to interpretations, so I guess this is fine.
  		desc:    "utf-16le dec: incorrect BOM is an error (RFC 2781:4.1)",
  		src:     "\xFE\xFF\x08\xD8\x45\xDF\x3D\x00\x52\x00\x61\x00",
  		sizeDst: 100,
  		want:    "\uFFFE\U00012345=Ra",
  		nSrc:    12,
  		t:       utf16LEIB.NewDecoder(),
  	}, {
  		desc:    "utf-16 enc: SHOULD write BOM (RFC 2781:3.3)",
  		src:     "\U00012345=Ra",
  		sizeDst: 100,
  		want:    "\xFF\xFE\x08\xD8\x45\xDF\x3D\x00\x52\x00\x61\x00",
  		nSrc:    7,
  		t:       utf16LEUB.NewEncoder(),
  	}, {
  		desc:    "utf-16 enc: SHOULD write BOM (RFC 2781:3.3)",
  		src:     "\U00012345=Ra",
  		sizeDst: 100,
  		want:    "\xFE\xFF\xD8\x08\xDF\x45\x00\x3D\x00\x52\x00\x61",
  		nSrc:    7,
  		t:       utf16BEUB.NewEncoder(),
  	}, {
  		desc:    "utf-16le enc: MUST NOT write BOM (RFC 2781:3.3)",
  		src:     "\U00012345=Ra",
  		sizeDst: 100,
  		want:    "\x08\xD8\x45\xDF\x3D\x00\x52\x00\x61\x00",
  		nSrc:    7,
  		t:       utf16LEIB.NewEncoder(),
  	}, {
  		desc:    "utf-16be dec: incorrect UTF-16: odd bytes",
  		src:     "\x00",
  		sizeDst: 100,
  		want:    "\uFFFD",
  		nSrc:    1,
  		t:       utf16BEIB.NewDecoder(),
  	}, {
  		desc:    "utf-16be dec: unpaired surrogate, odd bytes",
  		src:     "\xD8\x45\x00",
  		sizeDst: 100,
  		want:    "\uFFFD\uFFFD",
  		nSrc:    3,
  		t:       utf16BEIB.NewDecoder(),
  	}, {
  		desc:    "utf-16be dec: unpaired low surrogate + valid text",
  		src:     "\xD8\x45\x00a",
  		sizeDst: 100,
  		want:    "\uFFFDa",
  		nSrc:    4,
  		t:       utf16BEIB.NewDecoder(),
  	}, {
  		desc:    "utf-16be dec: unpaired low surrogate + valid text + single byte",
  		src:     "\xD8\x45\x00ab",
  		sizeDst: 100,
  		want:    "\uFFFDa\uFFFD",
  		nSrc:    5,
  		t:       utf16BEIB.NewDecoder(),
  	}, {
  		desc:    "utf-16le dec: unpaired high surrogate",
  		src:     "\x00\x00\x00\xDC\x12\xD8",
  		sizeDst: 100,
  		want:    "\x00\uFFFD\uFFFD",
  		nSrc:    6,
  		t:       utf16LEIB.NewDecoder(),
  	}, {
  		desc:    "utf-16be dec: two unpaired low surrogates",
  		src:     "\xD8\x45\xD8\x12",
  		sizeDst: 100,
  		want:    "\uFFFD\uFFFD",
  		nSrc:    4,
  		t:       utf16BEIB.NewDecoder(),
  	}, {
  		desc:    "utf-16be dec: short dst",
  		src:     "\x00a",
  		sizeDst: 0,
  		want:    "",
  		nSrc:    0,
  		t:       utf16BEIB.NewDecoder(),
  		err:     transform.ErrShortDst,
  	}, {
  		desc:    "utf-16be dec: short dst surrogate",
  		src:     "\xD8\xF5\xDC\x12",
  		sizeDst: 3,
  		want:    "",
  		nSrc:    0,
  		t:       utf16BEIB.NewDecoder(),
  		err:     transform.ErrShortDst,
  	}, {
  		desc:    "utf-16be dec: short dst trailing byte",
  		src:     "\x00",
  		sizeDst: 2,
  		want:    "",
  		nSrc:    0,
  		t:       utf16BEIB.NewDecoder(),
  		err:     transform.ErrShortDst,
  	}, {
  		desc:    "utf-16be dec: short src",
  		src:     "\x00",
  		notEOF:  true,
  		sizeDst: 3,
  		want:    "",
  		nSrc:    0,
  		t:       utf16BEIB.NewDecoder(),
  		err:     transform.ErrShortSrc,
  	}, {
  		desc:    "utf-16 enc",
  		src:     "\U00012345=Ra",
  		sizeDst: 100,
  		want:    "\xFE\xFF\xD8\x08\xDF\x45\x00\x3D\x00\x52\x00\x61",
  		nSrc:    7,
  		t:       utf16BEUB.NewEncoder(),
  	}, {
  		desc:    "utf-16 enc: short dst normal",
  		src:     "\U00012345=Ra",
  		sizeDst: 9,
  		want:    "\xD8\x08\xDF\x45\x00\x3D\x00\x52",
  		nSrc:    6,
  		t:       utf16BEIB.NewEncoder(),
  		err:     transform.ErrShortDst,
  	}, {
  		desc:    "utf-16 enc: short dst surrogate",
  		src:     "\U00012345=Ra",
  		sizeDst: 3,
  		want:    "",
  		nSrc:    0,
  		t:       utf16BEIB.NewEncoder(),
  		err:     transform.ErrShortDst,
  	}, {
  		desc:    "utf-16 enc: short src",
  		src:     "\U00012345=Ra\xC2",
  		notEOF:  true,
  		sizeDst: 100,
  		want:    "\xD8\x08\xDF\x45\x00\x3D\x00\x52\x00\x61",
  		nSrc:    7,
  		t:       utf16BEIB.NewEncoder(),
  		err:     transform.ErrShortSrc,
  	}, {
  		desc:    "utf-16be dec: don't change byte order mid-stream",
  		src:     "\xFE\xFF\xD8\x08\xDF\x45\x00\x3D\xFF\xFE\x00\x52\x00\x61",
  		sizeDst: 100,
  		want:    "\U00012345=\ufffeRa",
  		nSrc:    14,
  		t:       utf16BEUB.NewDecoder(),
  	}, {
  		desc:    "utf-16le dec: don't change byte order mid-stream",
  		src:     "\xFF\xFE\x08\xD8\x45\xDF\x3D\x00\xFF\xFE\xFE\xFF\x52\x00\x61\x00",
  		sizeDst: 100,
  		want:    "\U00012345=\ufeff\ufffeRa",
  		nSrc:    16,
  		t:       utf16LEUB.NewDecoder(),
  	}}
  	for i, tc := range testCases {
  		b := make([]byte, tc.sizeDst)
  		nDst, nSrc, err := tc.t.Transform(b, []byte(tc.src), !tc.notEOF)
  		if err != tc.err {
  			t.Errorf("%d:%s: error was %v; want %v", i, tc.desc, err, tc.err)
  		}
  		if got := string(b[:nDst]); got != tc.want {
  			t.Errorf("%d:%s: result was %q: want %q", i, tc.desc, got, tc.want)
  		}
  		if nSrc != tc.nSrc {
  			t.Errorf("%d:%s: nSrc was %d; want %d", i, tc.desc, nSrc, tc.nSrc)
  		}
  	}
  }
  
  func TestUTF8Decoder(t *testing.T) {
  	testCases := []struct {
  		desc    string
  		src     string
  		notEOF  bool // the inverse of atEOF
  		sizeDst int
  		want    string
  		nSrc    int
  		err     error
  	}{{
  		desc: "empty string, empty dest buffer",
  	}, {
  		desc:    "empty string",
  		sizeDst: 8,
  	}, {
  		desc:    "empty string, streaming",
  		notEOF:  true,
  		sizeDst: 8,
  	}, {
  		desc:    "ascii",
  		src:     "abcde",
  		sizeDst: 8,
  		want:    "abcde",
  		nSrc:    5,
  	}, {
  		desc:    "ascii and error",
  		src:     "ab\x80de",
  		sizeDst: 7,
  		want:    "ab\ufffdde",
  		nSrc:    5,
  	}, {
  		desc:    "valid two-byte sequence",
  		src:     "a\u0300bc",
  		sizeDst: 7,
  		want:    "a\u0300bc",
  		nSrc:    5,
  	}, {
  		desc:    "valid three-byte sequence",
  		src:     "a\u0300中",
  		sizeDst: 7,
  		want:    "a\u0300中",
  		nSrc:    6,
  	}, {
  		desc:    "valid four-byte sequence",
  		src:     "a中\U00016F50",
  		sizeDst: 8,
  		want:    "a中\U00016F50",
  		nSrc:    8,
  	}, {
  		desc:    "short source buffer",
  		src:     "abc\xf0\x90",
  		notEOF:  true,
  		sizeDst: 10,
  		want:    "abc",
  		nSrc:    3,
  		err:     transform.ErrShortSrc,
  	}, {
  		// We don't check for the maximal subpart of an ill-formed subsequence
  		// at the end of an open segment.
  		desc:    "complete invalid that looks like short at end",
  		src:     "abc\xf0\x80",
  		notEOF:  true,
  		sizeDst: 10,
  		want:    "abc", // instead of "abc\ufffd\ufffd",
  		nSrc:    3,
  		err:     transform.ErrShortSrc,
  	}, {
  		desc:    "incomplete sequence at end",
  		src:     "a\x80bc\xf0\x90",
  		sizeDst: 9,
  		want:    "a\ufffdbc\ufffd",
  		nSrc:    6,
  	}, {
  		desc:    "invalid second byte",
  		src:     "abc\xf0dddd",
  		sizeDst: 10,
  		want:    "abc\ufffddddd",
  		nSrc:    8,
  	}, {
  		desc:    "invalid second byte at end",
  		src:     "abc\xf0d",
  		sizeDst: 10,
  		want:    "abc\ufffdd",
  		nSrc:    5,
  	}, {
  		desc:    "invalid third byte",
  		src:     "a\u0300bc\xf0\x90dddd",
  		sizeDst: 12,
  		want:    "a\u0300bc\ufffddddd",
  		nSrc:    11,
  	}, {
  		desc:    "invalid third byte at end",
  		src:     "a\u0300bc\xf0\x90d",
  		sizeDst: 12,
  		want:    "a\u0300bc\ufffdd",
  		nSrc:    8,
  	}, {
  		desc:    "invalid fourth byte, tight buffer",
  		src:     "a\u0300bc\xf0\x90\x80d",
  		sizeDst: 9,
  		want:    "a\u0300bc\ufffdd",
  		nSrc:    9,
  	}, {
  		desc:    "invalid fourth byte at end",
  		src:     "a\u0300bc\xf0\x90\x80",
  		sizeDst: 8,
  		want:    "a\u0300bc\ufffd",
  		nSrc:    8,
  	}, {
  		desc:    "invalid fourth byte and short four byte sequence",
  		src:     "a\u0300bc\xf0\x90\x80\xf0\x90\x80",
  		notEOF:  true,
  		sizeDst: 20,
  		want:    "a\u0300bc\ufffd",
  		nSrc:    8,
  		err:     transform.ErrShortSrc,
  	}, {
  		desc:    "valid four-byte sequence overflowing short buffer",
  		src:     "a\u0300bc\xf0\x90\x80\x80",
  		notEOF:  true,
  		sizeDst: 8,
  		want:    "a\u0300bc",
  		nSrc:    5,
  		err:     transform.ErrShortDst,
  	}, {
  		desc:    "invalid fourth byte at end short, but short dst",
  		src:     "a\u0300bc\xf0\x90\x80\xf0\x90\x80",
  		notEOF:  true,
  		sizeDst: 8,
  		// More bytes would fit in the buffer, but this seems to require a more
  		// complicated and slower algorithm.
  		want: "a\u0300bc", // instead of "a\u0300bc"
  		nSrc: 5,
  		err:  transform.ErrShortDst,
  	}, {
  		desc:    "short dst for error",
  		src:     "abc\x80",
  		notEOF:  true,
  		sizeDst: 5,
  		want:    "abc",
  		nSrc:    3,
  		err:     transform.ErrShortDst,
  	}, {
  		desc:    "adjusting short dst buffer",
  		src:     "abc\x80ef",
  		notEOF:  true,
  		sizeDst: 6,
  		want:    "abc\ufffd",
  		nSrc:    4,
  		err:     transform.ErrShortDst,
  	}}
  	tr := UTF8.NewDecoder()
  	for i, tc := range testCases {
  		b := make([]byte, tc.sizeDst)
  		nDst, nSrc, err := tr.Transform(b, []byte(tc.src), !tc.notEOF)
  		if err != tc.err {
  			t.Errorf("%d:%s: error was %v; want %v", i, tc.desc, err, tc.err)
  		}
  		if got := string(b[:nDst]); got != tc.want {
  			t.Errorf("%d:%s: result was %q: want %q", i, tc.desc, got, tc.want)
  		}
  		if nSrc != tc.nSrc {
  			t.Errorf("%d:%s: nSrc was %d; want %d", i, tc.desc, nSrc, tc.nSrc)
  		}
  	}
  }
  
  func TestBOMOverride(t *testing.T) {
  	dec := BOMOverride(charmap.CodePage437.NewDecoder())
  	dst := make([]byte, 100)
  	for i, tc := range []struct {
  		src   string
  		atEOF bool
  		dst   string
  		nSrc  int
  		err   error
  	}{
  		0:  {"H\x82ll\x93", true, "Héllô", 5, nil},
  		1:  {"\uFEFFHéllö", true, "Héllö", 10, nil},
  		2:  {"\xFE\xFF\x00H\x00e\x00l\x00l\x00o", true, "Hello", 12, nil},
  		3:  {"\xFF\xFEH\x00e\x00l\x00l\x00o\x00", true, "Hello", 12, nil},
  		4:  {"\uFEFF", true, "", 3, nil},
  		5:  {"\xFE\xFF", true, "", 2, nil},
  		6:  {"\xFF\xFE", true, "", 2, nil},
  		7:  {"\xEF\xBB", true, "\u2229\u2557", 2, nil},
  		8:  {"\xEF", true, "\u2229", 1, nil},
  		9:  {"", true, "", 0, nil},
  		10: {"\xFE", true, "\u25a0", 1, nil},
  		11: {"\xFF", true, "\u00a0", 1, nil},
  		12: {"\xEF\xBB", false, "", 0, transform.ErrShortSrc},
  		13: {"\xEF", false, "", 0, transform.ErrShortSrc},
  		14: {"", false, "", 0, transform.ErrShortSrc},
  		15: {"\xFE", false, "", 0, transform.ErrShortSrc},
  		16: {"\xFF", false, "", 0, transform.ErrShortSrc},
  		17: {"\xFF\xFE", false, "", 0, transform.ErrShortSrc},
  	} {
  		dec.Reset()
  		nDst, nSrc, err := dec.Transform(dst, []byte(tc.src), tc.atEOF)
  		got := string(dst[:nDst])
  		if nSrc != tc.nSrc {
  			t.Errorf("%d: nSrc: got %d; want %d", i, nSrc, tc.nSrc)
  		}
  		if got != tc.dst {
  			t.Errorf("%d: got %+q; want %+q", i, got, tc.dst)
  		}
  		if err != tc.err {
  			t.Errorf("%d: error: got %v; want %v", i, err, tc.err)
  		}
  	}
  }
  