)

var errInvalidDelim = errors.New("csv: invalid field or comment delimiter")

func validDelim(r rune) bool {
	return r != 0 && r != '"' && r != '\r' && r != '\n' && utf8.ValidRune(r) && r != utf8.RuneError
}

// A Reader reads records from a CSV-encoded file.
//
// As returned by [NewReader], a Reader expects input conforming to RFC 4180.
// The exported fields can be changed to customize the details before the

	}
	if chunk[0] == '\\' && runtime.GOOS != "windows" {
		chunk = chunk[1:]
		if len(chunk) == 0 {
			err = ErrBadPattern
			return
		}
	}
	r, n := utf8.DecodeRuneInString(chunk)
	if r == utf8.RuneError && n == 1 {
		err = ErrBadPattern
	}
	nchunk = chunk[n:]
	if len(nchunk) == 0 {
		err = ErrBadPattern
	}
	return
}

// Glob returns the names of all files matching pattern or nil

func intstring(buf *[4]byte, v int64) (s string) {
	var b []byte
	if buf != nil {
		b = buf[:]
		s = slicebytetostringtmp(&b[0], len(b))
	} else {
		s, b = rawstring(4)
	}
	if int64(rune(v)) != v {
		v = runeError
	}
	n := encoderune(b, rune(v))
	return s[:n]
}

// rawstring allocates storage for a new string. The returned
// string and byte slice both refer to the same storage.

			// given how rarely we expect to hit these edge cases, speed and
			// conciseness are better.
			var width int
			if c == runeError {
				width = 1
				if i+2 < len(s) && s[i:i+3] == string(runeError) {
					width = 3
				}
			} else {
				width = len(string(c))
			}
			for j := 0; j < width; j++ {
				buf = append(buf, `\x`...)

		rr, size := utf8.DecodeRune(s[r:])
		if rr == utf8.RuneError && size == 1 {
			break
		}
		r += size
	}
	if r == len(s) {
		return s, true
	}

	b := make([]byte, len(s)+2*utf8.UTFMax)
	w := copy(b, s[0:r])
	for r < len(s) {
		// Out of room? Can only happen if s is full of
		// malformed UTF-8 and we're replacing each
		// byte with RuneError.
		if w >= len(b)-2*utf8.UTFMax {

	{"\xffff", `"\xffff"`},
	{"hello \xffff world", `"hello \xffff world"`},
	{"\uFFFD", `"\xef\xbf\xbd"`},                                             // utf8.RuneError
	{"\uFFFD hello \uFFFD world", `"\xef\xbf\xbd hello \xef\xbf\xbd world"`}, // utf8.RuneError
	// overflow
	{"9223372036854775810ns", `"9223372036854775810ns"`},
	{"9223372036854775808ns", `"9223372036854775808ns"`},

func toLowerCaseASCII(in string) string {
	// If the string is already lower-case then there's nothing to do.
	isAlreadyLowerCase := true
	for _, c := range in {
		if c == utf8.RuneError {
			// If we get a UTF-8 error then there might be
			// upper-case ASCII bytes in the invalid sequence.
			isAlreadyLowerCase = false
			break
		}
		if 'A' <= c && c <= 'Z' {

		n := len(src) - i
		if n > utf8.UTFMax {
			n = utf8.UTFMax
		}
		c, size := utf8.DecodeRuneInString(string(src[i : i+n]))
		if c == utf8.RuneError && size == 1 {
			dst = append(dst, src[start:i]...)
			dst = append(dst, `\ufffd`...)
			i += size
			start = i
			continue
		}
		// U+2028 is LINE SEPARATOR.
		// U+2029 is PARAGRAPH SEPARATOR.