Adding upstream version 1.17.13.upstream/1.17.13upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1238 insertions, 0 deletions

diff --git a/src/fmt/scan.go b/src/fmt/scan.go
new file mode 100644
index 0000000..3815770
--- /dev/null
+++ b/src/fmt/scan.go
@@ -0,0 +1,1238 @@
+// Copyright 2010 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 fmt
+
+import (
+	"errors"
+	"io"
+	"math"
+	"os"
+	"reflect"
+	"strconv"
+	"sync"
+	"unicode/utf8"
+)
+
+// ScanState represents the scanner state passed to custom scanners.
+// Scanners may do rune-at-a-time scanning or ask the ScanState
+// to discover the next space-delimited token.
+type ScanState interface {
+	// ReadRune reads the next rune (Unicode code point) from the input.
+	// If invoked during Scanln, Fscanln, or Sscanln, ReadRune() will
+	// return EOF after returning the first '\n' or when reading beyond
+	// the specified width.
+	ReadRune() (r rune, size int, err error)
+	// UnreadRune causes the next call to ReadRune to return the same rune.
+	UnreadRune() error
+	// SkipSpace skips space in the input. Newlines are treated appropriately
+	// for the operation being performed; see the package documentation
+	// for more information.
+	SkipSpace()
+	// Token skips space in the input if skipSpace is true, then returns the
+	// run of Unicode code points c satisfying f(c).  If f is nil,
+	// !unicode.IsSpace(c) is used; that is, the token will hold non-space
+	// characters. Newlines are treated appropriately for the operation being
+	// performed; see the package documentation for more information.
+	// The returned slice points to shared data that may be overwritten
+	// by the next call to Token, a call to a Scan function using the ScanState
+	// as input, or when the calling Scan method returns.
+	Token(skipSpace bool, f func(rune) bool) (token []byte, err error)
+	// Width returns the value of the width option and whether it has been set.
+	// The unit is Unicode code points.
+	Width() (wid int, ok bool)
+	// Because ReadRune is implemented by the interface, Read should never be
+	// called by the scanning routines and a valid implementation of
+	// ScanState may choose always to return an error from Read.
+	Read(buf []byte) (n int, err error)
+}
+
+// Scanner is implemented by any value that has a Scan method, which scans
+// the input for the representation of a value and stores the result in the
+// receiver, which must be a pointer to be useful. The Scan method is called
+// for any argument to Scan, Scanf, or Scanln that implements it.
+type Scanner interface {
+	Scan(state ScanState, verb rune) error
+}
+
+// Scan scans text read from standard input, storing successive
+// space-separated values into successive arguments. Newlines count
+// as space. It returns the number of items successfully scanned.
+// If that is less than the number of arguments, err will report why.
+func Scan(a ...interface{}) (n int, err error) {
+	return Fscan(os.Stdin, a...)
+}
+
+// Scanln is similar to Scan, but stops scanning at a newline and
+// after the final item there must be a newline or EOF.
+func Scanln(a ...interface{}) (n int, err error) {
+	return Fscanln(os.Stdin, a...)
+}
+
+// Scanf scans text read from standard input, storing successive
+// space-separated values into successive arguments as determined by
+// the format. It returns the number of items successfully scanned.
+// If that is less than the number of arguments, err will report why.
+// Newlines in the input must match newlines in the format.
+// The one exception: the verb %c always scans the next rune in the
+// input, even if it is a space (or tab etc.) or newline.
+func Scanf(format string, a ...interface{}) (n int, err error) {
+	return Fscanf(os.Stdin, format, a...)
+}
+
+type stringReader string
+
+func (r *stringReader) Read(b []byte) (n int, err error) {
+	n = copy(b, *r)
+	*r = (*r)[n:]
+	if n == 0 {
+		err = io.EOF
+	}
+	return
+}
+
+// Sscan scans the argument string, storing successive space-separated
+// values into successive arguments. Newlines count as space. It
+// returns the number of items successfully scanned. If that is less
+// than the number of arguments, err will report why.
+func Sscan(str string, a ...interface{}) (n int, err error) {
+	return Fscan((*stringReader)(&str), a...)
+}
+
+// Sscanln is similar to Sscan, but stops scanning at a newline and
+// after the final item there must be a newline or EOF.
+func Sscanln(str string, a ...interface{}) (n int, err error) {
+	return Fscanln((*stringReader)(&str), a...)
+}
+
+// Sscanf scans the argument string, storing successive space-separated
+// values into successive arguments as determined by the format. It
+// returns the number of items successfully parsed.
+// Newlines in the input must match newlines in the format.
+func Sscanf(str string, format string, a ...interface{}) (n int, err error) {
+	return Fscanf((*stringReader)(&str), format, a...)
+}
+
+// Fscan scans text read from r, storing successive space-separated
+// values into successive arguments. Newlines count as space. It
+// returns the number of items successfully scanned. If that is less
+// than the number of arguments, err will report why.
+func Fscan(r io.Reader, a ...interface{}) (n int, err error) {
+	s, old := newScanState(r, true, false)
+	n, err = s.doScan(a)
+	s.free(old)
+	return
+}
+
+// Fscanln is similar to Fscan, but stops scanning at a newline and
+// after the final item there must be a newline or EOF.
+func Fscanln(r io.Reader, a ...interface{}) (n int, err error) {
+	s, old := newScanState(r, false, true)
+	n, err = s.doScan(a)
+	s.free(old)
+	return
+}
+
+// Fscanf scans text read from r, storing successive space-separated
+// values into successive arguments as determined by the format. It
+// returns the number of items successfully parsed.
+// Newlines in the input must match newlines in the format.
+func Fscanf(r io.Reader, format string, a ...interface{}) (n int, err error) {
+	s, old := newScanState(r, false, false)
+	n, err = s.doScanf(format, a)
+	s.free(old)
+	return
+}
+
+// scanError represents an error generated by the scanning software.
+// It's used as a unique signature to identify such errors when recovering.
+type scanError struct {
+	err error
+}
+
+const eof = -1
+
+// ss is the internal implementation of ScanState.
+type ss struct {
+	rs    io.RuneScanner // where to read input
+	buf   buffer         // token accumulator
+	count int            // runes consumed so far.
+	atEOF bool           // already read EOF
+	ssave
+}
+
+// ssave holds the parts of ss that need to be
+// saved and restored on recursive scans.
+type ssave struct {
+	validSave bool // is or was a part of an actual ss.
+	nlIsEnd   bool // whether newline terminates scan
+	nlIsSpace bool // whether newline counts as white space
+	argLimit  int  // max value of ss.count for this arg; argLimit <= limit
+	limit     int  // max value of ss.count.
+	maxWid    int  // width of this arg.
+}
+
+// The Read method is only in ScanState so that ScanState
+// satisfies io.Reader. It will never be called when used as
+// intended, so there is no need to make it actually work.
+func (s *ss) Read(buf []byte) (n int, err error) {
+	return 0, errors.New("ScanState's Read should not be called. Use ReadRune")
+}
+
+func (s *ss) ReadRune() (r rune, size int, err error) {
+	if s.atEOF || s.count >= s.argLimit {
+		err = io.EOF
+		return
+	}
+
+	r, size, err = s.rs.ReadRune()
+	if err == nil {
+		s.count++
+		if s.nlIsEnd && r == '\n' {
+			s.atEOF = true
+		}
+	} else if err == io.EOF {
+		s.atEOF = true
+	}
+	return
+}
+
+func (s *ss) Width() (wid int, ok bool) {
+	if s.maxWid == hugeWid {
+		return 0, false
+	}
+	return s.maxWid, true
+}
+
+// The public method returns an error; this private one panics.
+// If getRune reaches EOF, the return value is EOF (-1).
+func (s *ss) getRune() (r rune) {
+	r, _, err := s.ReadRune()
+	if err != nil {
+		if err == io.EOF {
+			return eof
+		}
+		s.error(err)
+	}
+	return
+}
+
+// mustReadRune turns io.EOF into a panic(io.ErrUnexpectedEOF).
+// It is called in cases such as string scanning where an EOF is a
+// syntax error.
+func (s *ss) mustReadRune() (r rune) {
+	r = s.getRune()
+	if r == eof {
+		s.error(io.ErrUnexpectedEOF)
+	}
+	return
+}
+
+func (s *ss) UnreadRune() error {
+	s.rs.UnreadRune()
+	s.atEOF = false
+	s.count--
+	return nil
+}
+
+func (s *ss) error(err error) {
+	panic(scanError{err})
+}
+
+func (s *ss) errorString(err string) {
+	panic(scanError{errors.New(err)})
+}
+
+func (s *ss) Token(skipSpace bool, f func(rune) bool) (tok []byte, err error) {
+	defer func() {
+		if e := recover(); e != nil {
+			if se, ok := e.(scanError); ok {
+				err = se.err
+			} else {
+				panic(e)
+			}
+		}
+	}()
+	if f == nil {
+		f = notSpace
+	}
+	s.buf = s.buf[:0]
+	tok = s.token(skipSpace, f)
+	return
+}
+
+// space is a copy of the unicode.White_Space ranges,
+// to avoid depending on package unicode.
+var space = [][2]uint16{
+	{0x0009, 0x000d},
+	{0x0020, 0x0020},
+	{0x0085, 0x0085},
+	{0x00a0, 0x00a0},
+	{0x1680, 0x1680},
+	{0x2000, 0x200a},
+	{0x2028, 0x2029},
+	{0x202f, 0x202f},
+	{0x205f, 0x205f},
+	{0x3000, 0x3000},
+}
+
+func isSpace(r rune) bool {
+	if r >= 1<<16 {
+		return false
+	}
+	rx := uint16(r)
+	for _, rng := range space {
+		if rx < rng[0] {
+			return false
+		}
+		if rx <= rng[1] {
+			return true
+		}
+	}
+	return false
+}
+
+// notSpace is the default scanning function used in Token.
+func notSpace(r rune) bool {
+	return !isSpace(r)
+}
+
+// readRune is a structure to enable reading UTF-8 encoded code points
+// from an io.Reader. It is used if the Reader given to the scanner does
+// not already implement io.RuneScanner.
+type readRune struct {
+	reader   io.Reader
+	buf      [utf8.UTFMax]byte // used only inside ReadRune
+	pending  int               // number of bytes in pendBuf; only >0 for bad UTF-8
+	pendBuf  [utf8.UTFMax]byte // bytes left over
+	peekRune rune              // if >=0 next rune; when <0 is ^(previous Rune)
+}
+
+// readByte returns the next byte from the input, which may be
+// left over from a previous read if the UTF-8 was ill-formed.
+func (r *readRune) readByte() (b byte, err error) {
+	if r.pending > 0 {
+		b = r.pendBuf[0]
+		copy(r.pendBuf[0:], r.pendBuf[1:])
+		r.pending--
+		return
+	}
+	n, err := io.ReadFull(r.reader, r.pendBuf[:1])
+	if n != 1 {
+		return 0, err
+	}
+	return r.pendBuf[0], err
+}
+
+// ReadRune returns the next UTF-8 encoded code point from the
+// io.Reader inside r.
+func (r *readRune) ReadRune() (rr rune, size int, err error) {
+	if r.peekRune >= 0 {
+		rr = r.peekRune
+		r.peekRune = ^r.peekRune
+		size = utf8.RuneLen(rr)
+		return
+	}
+	r.buf[0], err = r.readByte()
+	if err != nil {
+		return
+	}
+	if r.buf[0] < utf8.RuneSelf { // fast check for common ASCII case
+		rr = rune(r.buf[0])
+		size = 1 // Known to be 1.
+		// Flip the bits of the rune so it's available to UnreadRune.
+		r.peekRune = ^rr
+		return
+	}
+	var n int
+	for n = 1; !utf8.FullRune(r.buf[:n]); n++ {
+		r.buf[n], err = r.readByte()
+		if err != nil {
+			if err == io.EOF {
+				err = nil
+				break
+			}
+			return
+		}
+	}
+	rr, size = utf8.DecodeRune(r.buf[:n])
+	if size < n { // an error, save the bytes for the next read
+		copy(r.pendBuf[r.pending:], r.buf[size:n])
+		r.pending += n - size
+	}
+	// Flip the bits of the rune so it's available to UnreadRune.
+	r.peekRune = ^rr
+	return
+}
+
+func (r *readRune) UnreadRune() error {
+	if r.peekRune >= 0 {
+		return errors.New("fmt: scanning called UnreadRune with no rune available")
+	}
+	// Reverse bit flip of previously read rune to obtain valid >=0 state.
+	r.peekRune = ^r.peekRune
+	return nil
+}
+
+var ssFree = sync.Pool{
+	New: func() interface{} { return new(ss) },
+}
+
+// newScanState allocates a new ss struct or grab a cached one.
+func newScanState(r io.Reader, nlIsSpace, nlIsEnd bool) (s *ss, old ssave) {
+	s = ssFree.Get().(*ss)
+	if rs, ok := r.(io.RuneScanner); ok {
+		s.rs = rs
+	} else {
+		s.rs = &readRune{reader: r, peekRune: -1}
+	}
+	s.nlIsSpace = nlIsSpace
+	s.nlIsEnd = nlIsEnd
+	s.atEOF = false
+	s.limit = hugeWid
+	s.argLimit = hugeWid
+	s.maxWid = hugeWid
+	s.validSave = true
+	s.count = 0
+	return
+}
+
+// free saves used ss structs in ssFree; avoid an allocation per invocation.
+func (s *ss) free(old ssave) {
+	// If it was used recursively, just restore the old state.
+	if old.validSave {
+		s.ssave = old
+		return
+	}
+	// Don't hold on to ss structs with large buffers.
+	if cap(s.buf) > 1024 {
+		return
+	}
+	s.buf = s.buf[:0]
+	s.rs = nil
+	ssFree.Put(s)
+}
+
+// SkipSpace provides Scan methods the ability to skip space and newline
+// characters in keeping with the current scanning mode set by format strings
+// and Scan/Scanln.
+func (s *ss) SkipSpace() {
+	for {
+		r := s.getRune()
+		if r == eof {
+			return
+		}
+		if r == '\r' && s.peek("\n") {
+			continue
+		}
+		if r == '\n' {
+			if s.nlIsSpace {
+				continue
+			}
+			s.errorString("unexpected newline")
+			return
+		}
+		if !isSpace(r) {
+			s.UnreadRune()
+			break
+		}
+	}
+}
+
+// token returns the next space-delimited string from the input. It
+// skips white space. For Scanln, it stops at newlines. For Scan,
+// newlines are treated as spaces.
+func (s *ss) token(skipSpace bool, f func(rune) bool) []byte {
+	if skipSpace {
+		s.SkipSpace()
+	}
+	// read until white space or newline
+	for {
+		r := s.getRune()
+		if r == eof {
+			break
+		}
+		if !f(r) {
+			s.UnreadRune()
+			break
+		}
+		s.buf.writeRune(r)
+	}
+	return s.buf
+}
+
+var complexError = errors.New("syntax error scanning complex number")
+var boolError = errors.New("syntax error scanning boolean")
+
+func indexRune(s string, r rune) int {
+	for i, c := range s {
+		if c == r {
+			return i
+		}
+	}
+	return -1
+}
+
+// consume reads the next rune in the input and reports whether it is in the ok string.
+// If accept is true, it puts the character into the input token.
+func (s *ss) consume(ok string, accept bool) bool {
+	r := s.getRune()
+	if r == eof {
+		return false
+	}
+	if indexRune(ok, r) >= 0 {
+		if accept {
+			s.buf.writeRune(r)
+		}
+		return true
+	}
+	if r != eof && accept {
+		s.UnreadRune()
+	}
+	return false
+}
+
+// peek reports whether the next character is in the ok string, without consuming it.
+func (s *ss) peek(ok string) bool {
+	r := s.getRune()
+	if r != eof {
+		s.UnreadRune()
+	}
+	return indexRune(ok, r) >= 0
+}
+
+func (s *ss) notEOF() {
+	// Guarantee there is data to be read.
+	if r := s.getRune(); r == eof {
+		panic(io.EOF)
+	}
+	s.UnreadRune()
+}
+
+// accept checks the next rune in the input. If it's a byte (sic) in the string, it puts it in the
+// buffer and returns true. Otherwise it return false.
+func (s *ss) accept(ok string) bool {
+	return s.consume(ok, true)
+}
+
+// okVerb verifies that the verb is present in the list, setting s.err appropriately if not.
+func (s *ss) okVerb(verb rune, okVerbs, typ string) bool {
+	for _, v := range okVerbs {
+		if v == verb {
+			return true
+		}
+	}
+	s.errorString("bad verb '%" + string(verb) + "' for " + typ)
+	return false
+}
+
+// scanBool returns the value of the boolean represented by the next token.
+func (s *ss) scanBool(verb rune) bool {
+	s.SkipSpace()
+	s.notEOF()
+	if !s.okVerb(verb, "tv", "boolean") {
+		return false
+	}
+	// Syntax-checking a boolean is annoying. We're not fastidious about case.
+	switch s.getRune() {
+	case '0':
+		return false
+	case '1':
+		return true
+	case 't', 'T':
+		if s.accept("rR") && (!s.accept("uU") || !s.accept("eE")) {
+			s.error(boolError)
+		}
+		return true
+	case 'f', 'F':
+		if s.accept("aA") && (!s.accept("lL") || !s.accept("sS") || !s.accept("eE")) {
+			s.error(boolError)
+		}
+		return false
+	}
+	return false
+}
+
+// Numerical elements
+const (
+	binaryDigits      = "01"
+	octalDigits       = "01234567"
+	decimalDigits     = "0123456789"
+	hexadecimalDigits = "0123456789aAbBcCdDeEfF"
+	sign              = "+-"
+	period            = "."
+	exponent          = "eEpP"
+)
+
+// getBase returns the numeric base represented by the verb and its digit string.
+func (s *ss) getBase(verb rune) (base int, digits string) {
+	s.okVerb(verb, "bdoUxXv", "integer") // sets s.err
+	base = 10
+	digits = decimalDigits
+	switch verb {
+	case 'b':
+		base = 2
+		digits = binaryDigits
+	case 'o':
+		base = 8
+		digits = octalDigits
+	case 'x', 'X', 'U':
+		base = 16
+		digits = hexadecimalDigits
+	}
+	return
+}
+
+// scanNumber returns the numerical string with specified digits starting here.
+func (s *ss) scanNumber(digits string, haveDigits bool) string {
+	if !haveDigits {
+		s.notEOF()
+		if !s.accept(digits) {
+			s.errorString("expected integer")
+		}
+	}
+	for s.accept(digits) {
+	}
+	return string(s.buf)
+}
+
+// scanRune returns the next rune value in the input.
+func (s *ss) scanRune(bitSize int) int64 {
+	s.notEOF()
+	r := s.getRune()
+	n := uint(bitSize)
+	x := (int64(r) << (64 - n)) >> (64 - n)
+	if x != int64(r) {
+		s.errorString("overflow on character value " + string(r))
+	}
+	return int64(r)
+}
+
+// scanBasePrefix reports whether the integer begins with a base prefix
+// and returns the base, digit string, and whether a zero was found.
+// It is called only if the verb is %v.
+func (s *ss) scanBasePrefix() (base int, digits string, zeroFound bool) {
+	if !s.peek("0") {
+		return 0, decimalDigits + "_", false
+	}
+	s.accept("0")
+	// Special cases for 0, 0b, 0o, 0x.
+	switch {
+	case s.peek("bB"):
+		s.consume("bB", true)
+		return 0, binaryDigits + "_", true
+	case s.peek("oO"):
+		s.consume("oO", true)
+		return 0, octalDigits + "_", true
+	case s.peek("xX"):
+		s.consume("xX", true)
+		return 0, hexadecimalDigits + "_", true
+	default:
+		return 0, octalDigits + "_", true
+	}
+}
+
+// scanInt returns the value of the integer represented by the next
+// token, checking for overflow. Any error is stored in s.err.
+func (s *ss) scanInt(verb rune, bitSize int) int64 {
+	if verb == 'c' {
+		return s.scanRune(bitSize)
+	}
+	s.SkipSpace()
+	s.notEOF()
+	base, digits := s.getBase(verb)
+	haveDigits := false
+	if verb == 'U' {
+		if !s.consume("U", false) || !s.consume("+", false) {
+			s.errorString("bad unicode format ")
+		}
+	} else {
+		s.accept(sign) // If there's a sign, it will be left in the token buffer.
+		if verb == 'v' {
+			base, digits, haveDigits = s.scanBasePrefix()
+		}
+	}
+	tok := s.scanNumber(digits, haveDigits)
+	i, err := strconv.ParseInt(tok, base, 64)
+	if err != nil {
+		s.error(err)
+	}
+	n := uint(bitSize)
+	x := (i << (64 - n)) >> (64 - n)
+	if x != i {
+		s.errorString("integer overflow on token " + tok)
+	}
+	return i
+}
+
+// scanUint returns the value of the unsigned integer represented
+// by the next token, checking for overflow. Any error is stored in s.err.
+func (s *ss) scanUint(verb rune, bitSize int) uint64 {
+	if verb == 'c' {
+		return uint64(s.scanRune(bitSize))
+	}
+	s.SkipSpace()
+	s.notEOF()
+	base, digits := s.getBase(verb)
+	haveDigits := false
+	if verb == 'U' {
+		if !s.consume("U", false) || !s.consume("+", false) {
+			s.errorString("bad unicode format ")
+		}
+	} else if verb == 'v' {
+		base, digits, haveDigits = s.scanBasePrefix()
+	}
+	tok := s.scanNumber(digits, haveDigits)
+	i, err := strconv.ParseUint(tok, base, 64)
+	if err != nil {
+		s.error(err)
+	}
+	n := uint(bitSize)
+	x := (i << (64 - n)) >> (64 - n)
+	if x != i {
+		s.errorString("unsigned integer overflow on token " + tok)
+	}
+	return i
+}
+
+// floatToken returns the floating-point number starting here, no longer than swid
+// if the width is specified. It's not rigorous about syntax because it doesn't check that
+// we have at least some digits, but Atof will do that.
+func (s *ss) floatToken() string {
+	s.buf = s.buf[:0]
+	// NaN?
+	if s.accept("nN") && s.accept("aA") && s.accept("nN") {
+		return string(s.buf)
+	}
+	// leading sign?
+	s.accept(sign)
+	// Inf?
+	if s.accept("iI") && s.accept("nN") && s.accept("fF") {
+		return string(s.buf)
+	}
+	digits := decimalDigits + "_"
+	exp := exponent
+	if s.accept("0") && s.accept("xX") {
+		digits = hexadecimalDigits + "_"
+		exp = "pP"
+	}
+	// digits?
+	for s.accept(digits) {
+	}
+	// decimal point?
+	if s.accept(period) {
+		// fraction?
+		for s.accept(digits) {
+		}
+	}
+	// exponent?
+	if s.accept(exp) {
+		// leading sign?
+		s.accept(sign)
+		// digits?
+		for s.accept(decimalDigits + "_") {
+		}
+	}
+	return string(s.buf)
+}
+
+// complexTokens returns the real and imaginary parts of the complex number starting here.
+// The number might be parenthesized and has the format (N+Ni) where N is a floating-point
+// number and there are no spaces within.
+func (s *ss) complexTokens() (real, imag string) {
+	// TODO: accept N and Ni independently?
+	parens := s.accept("(")
+	real = s.floatToken()
+	s.buf = s.buf[:0]
+	// Must now have a sign.
+	if !s.accept("+-") {
+		s.error(complexError)
+	}
+	// Sign is now in buffer
+	imagSign := string(s.buf)
+	imag = s.floatToken()
+	if !s.accept("i") {
+		s.error(complexError)
+	}
+	if parens && !s.accept(")") {
+		s.error(complexError)
+	}
+	return real, imagSign + imag
+}
+
+func hasX(s string) bool {
+	for i := 0; i < len(s); i++ {
+		if s[i] == 'x' || s[i] == 'X' {
+			return true
+		}
+	}
+	return false
+}
+
+// convertFloat converts the string to a float64value.
+func (s *ss) convertFloat(str string, n int) float64 {
+	// strconv.ParseFloat will handle "+0x1.fp+2",
+	// but we have to implement our non-standard
+	// decimal+binary exponent mix (1.2p4) ourselves.
+	if p := indexRune(str, 'p'); p >= 0 && !hasX(str) {
+		// Atof doesn't handle power-of-2 exponents,
+		// but they're easy to evaluate.
+		f, err := strconv.ParseFloat(str[:p], n)
+		if err != nil {
+			// Put full string into error.
+			if e, ok := err.(*strconv.NumError); ok {
+				e.Num = str
+			}
+			s.error(err)
+		}
+		m, err := strconv.Atoi(str[p+1:])
+		if err != nil {
+			// Put full string into error.
+			if e, ok := err.(*strconv.NumError); ok {
+				e.Num = str
+			}
+			s.error(err)
+		}
+		return math.Ldexp(f, m)
+	}
+	f, err := strconv.ParseFloat(str, n)
+	if err != nil {
+		s.error(err)
+	}
+	return f
+}
+
+// convertComplex converts the next token to a complex128 value.
+// The atof argument is a type-specific reader for the underlying type.
+// If we're reading complex64, atof will parse float32s and convert them
+// to float64's to avoid reproducing this code for each complex type.
+func (s *ss) scanComplex(verb rune, n int) complex128 {
+	if !s.okVerb(verb, floatVerbs, "complex") {
+		return 0
+	}
+	s.SkipSpace()
+	s.notEOF()
+	sreal, simag := s.complexTokens()
+	real := s.convertFloat(sreal, n/2)
+	imag := s.convertFloat(simag, n/2)
+	return complex(real, imag)
+}
+
+// convertString returns the string represented by the next input characters.
+// The format of the input is determined by the verb.
+func (s *ss) convertString(verb rune) (str string) {
+	if !s.okVerb(verb, "svqxX", "string") {
+		return ""
+	}
+	s.SkipSpace()
+	s.notEOF()
+	switch verb {
+	case 'q':
+		str = s.quotedString()
+	case 'x', 'X':
+		str = s.hexString()
+	default:
+		str = string(s.token(true, notSpace)) // %s and %v just return the next word
+	}
+	return
+}
+
+// quotedString returns the double- or back-quoted string represented by the next input characters.
+func (s *ss) quotedString() string {
+	s.notEOF()
+	quote := s.getRune()
+	switch quote {
+	case '`':
+		// Back-quoted: Anything goes until EOF or back quote.
+		for {
+			r := s.mustReadRune()
+			if r == quote {
+				break
+			}
+			s.buf.writeRune(r)
+		}
+		return string(s.buf)
+	case '"':
+		// Double-quoted: Include the quotes and let strconv.Unquote do the backslash escapes.
+		s.buf.writeByte('"')
+		for {
+			r := s.mustReadRune()
+			s.buf.writeRune(r)
+			if r == '\\' {
+				// In a legal backslash escape, no matter how long, only the character
+				// immediately after the escape can itself be a backslash or quote.
+				// Thus we only need to protect the first character after the backslash.
+				s.buf.writeRune(s.mustReadRune())
+			} else if r == '"' {
+				break
+			}
+		}
+		result, err := strconv.Unquote(string(s.buf))
+		if err != nil {
+			s.error(err)
+		}
+		return result
+	default:
+		s.errorString("expected quoted string")
+	}
+	return ""
+}
+
+// hexDigit returns the value of the hexadecimal digit.
+func hexDigit(d rune) (int, bool) {
+	digit := int(d)
+	switch digit {
+	case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
+		return digit - '0', true
+	case 'a', 'b', 'c', 'd', 'e', 'f':
+		return 10 + digit - 'a', true
+	case 'A', 'B', 'C', 'D', 'E', 'F':
+		return 10 + digit - 'A', true
+	}
+	return -1, false
+}
+
+// hexByte returns the next hex-encoded (two-character) byte from the input.
+// It returns ok==false if the next bytes in the input do not encode a hex byte.
+// If the first byte is hex and the second is not, processing stops.
+func (s *ss) hexByte() (b byte, ok bool) {
+	rune1 := s.getRune()
+	if rune1 == eof {
+		return
+	}
+	value1, ok := hexDigit(rune1)
+	if !ok {
+		s.UnreadRune()
+		return
+	}
+	value2, ok := hexDigit(s.mustReadRune())
+	if !ok {
+		s.errorString("illegal hex digit")
+		return
+	}
+	return byte(value1<<4 | value2), true
+}
+
+// hexString returns the space-delimited hexpair-encoded string.
+func (s *ss) hexString() string {
+	s.notEOF()
+	for {
+		b, ok := s.hexByte()
+		if !ok {
+			break
+		}
+		s.buf.writeByte(b)
+	}
+	if len(s.buf) == 0 {
+		s.errorString("no hex data for %x string")
+		return ""
+	}
+	return string(s.buf)
+}
+
+const (
+	floatVerbs = "beEfFgGv"
+
+	hugeWid = 1 << 30
+
+	intBits     = 32 << (^uint(0) >> 63)
+	uintptrBits = 32 << (^uintptr(0) >> 63)
+)
+
+// scanPercent scans a literal percent character.
+func (s *ss) scanPercent() {
+	s.SkipSpace()
+	s.notEOF()
+	if !s.accept("%") {
+		s.errorString("missing literal %")
+	}
+}
+
+// scanOne scans a single value, deriving the scanner from the type of the argument.
+func (s *ss) scanOne(verb rune, arg interface{}) {
+	s.buf = s.buf[:0]
+	var err error
+	// If the parameter has its own Scan method, use that.
+	if v, ok := arg.(Scanner); ok {
+		err = v.Scan(s, verb)
+		if err != nil {
+			if err == io.EOF {
+				err = io.ErrUnexpectedEOF
+			}
+			s.error(err)
+		}
+		return
+	}
+
+	switch v := arg.(type) {
+	case *bool:
+		*v = s.scanBool(verb)
+	case *complex64:
+		*v = complex64(s.scanComplex(verb, 64))
+	case *complex128:
+		*v = s.scanComplex(verb, 128)
+	case *int:
+		*v = int(s.scanInt(verb, intBits))
+	case *int8:
+		*v = int8(s.scanInt(verb, 8))
+	case *int16:
+		*v = int16(s.scanInt(verb, 16))
+	case *int32:
+		*v = int32(s.scanInt(verb, 32))
+	case *int64:
+		*v = s.scanInt(verb, 64)
+	case *uint:
+		*v = uint(s.scanUint(verb, intBits))
+	case *uint8:
+		*v = uint8(s.scanUint(verb, 8))
+	case *uint16:
+		*v = uint16(s.scanUint(verb, 16))
+	case *uint32:
+		*v = uint32(s.scanUint(verb, 32))
+	case *uint64:
+		*v = s.scanUint(verb, 64)
+	case *uintptr:
+		*v = uintptr(s.scanUint(verb, uintptrBits))
+	// Floats are tricky because you want to scan in the precision of the result, not
+	// scan in high precision and convert, in order to preserve the correct error condition.
+	case *float32:
+		if s.okVerb(verb, floatVerbs, "float32") {
+			s.SkipSpace()
+			s.notEOF()
+			*v = float32(s.convertFloat(s.floatToken(), 32))
+		}
+	case *float64:
+		if s.okVerb(verb, floatVerbs, "float64") {
+			s.SkipSpace()
+			s.notEOF()
+			*v = s.convertFloat(s.floatToken(), 64)
+		}
+	case *string:
+		*v = s.convertString(verb)
+	case *[]byte:
+		// We scan to string and convert so we get a copy of the data.
+		// If we scanned to bytes, the slice would point at the buffer.
+		*v = []byte(s.convertString(verb))
+	default:
+		val := reflect.ValueOf(v)
+		ptr := val
+		if ptr.Kind() != reflect.Ptr {
+			s.errorString("type not a pointer: " + val.Type().String())
+			return
+		}
+		switch v := ptr.Elem(); v.Kind() {
+		case reflect.Bool:
+			v.SetBool(s.scanBool(verb))
+		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+			v.SetInt(s.scanInt(verb, v.Type().Bits()))
+		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+			v.SetUint(s.scanUint(verb, v.Type().Bits()))
+		case reflect.String:
+			v.SetString(s.convertString(verb))
+		case reflect.Slice:
+			// For now, can only handle (renamed) []byte.
+			typ := v.Type()
+			if typ.Elem().Kind() != reflect.Uint8 {
+				s.errorString("can't scan type: " + val.Type().String())
+			}
+			str := s.convertString(verb)
+			v.Set(reflect.MakeSlice(typ, len(str), len(str)))
+			for i := 0; i < len(str); i++ {
+				v.Index(i).SetUint(uint64(str[i]))
+			}
+		case reflect.Float32, reflect.Float64:
+			s.SkipSpace()
+			s.notEOF()
+			v.SetFloat(s.convertFloat(s.floatToken(), v.Type().Bits()))
+		case reflect.Complex64, reflect.Complex128:
+			v.SetComplex(s.scanComplex(verb, v.Type().Bits()))
+		default:
+			s.errorString("can't scan type: " + val.Type().String())
+		}
+	}
+}
+
+// errorHandler turns local panics into error returns.
+func errorHandler(errp *error) {
+	if e := recover(); e != nil {
+		if se, ok := e.(scanError); ok { // catch local error
+			*errp = se.err
+		} else if eof, ok := e.(error); ok && eof == io.EOF { // out of input
+			*errp = eof
+		} else {
+			panic(e)
+		}
+	}
+}
+
+// doScan does the real work for scanning without a format string.
+func (s *ss) doScan(a []interface{}) (numProcessed int, err error) {
+	defer errorHandler(&err)
+	for _, arg := range a {
+		s.scanOne('v', arg)
+		numProcessed++
+	}
+	// Check for newline (or EOF) if required (Scanln etc.).
+	if s.nlIsEnd {
+		for {
+			r := s.getRune()
+			if r == '\n' || r == eof {
+				break
+			}
+			if !isSpace(r) {
+				s.errorString("expected newline")
+				break
+			}
+		}
+	}
+	return
+}
+
+// advance determines whether the next characters in the input match
+// those of the format. It returns the number of bytes (sic) consumed
+// in the format. All runs of space characters in either input or
+// format behave as a single space. Newlines are special, though:
+// newlines in the format must match those in the input and vice versa.
+// This routine also handles the %% case. If the return value is zero,
+// either format starts with a % (with no following %) or the input
+// is empty. If it is negative, the input did not match the string.
+func (s *ss) advance(format string) (i int) {
+	for i < len(format) {
+		fmtc, w := utf8.DecodeRuneInString(format[i:])
+
+		// Space processing.
+		// In the rest of this comment "space" means spaces other than newline.
+		// Newline in the format matches input of zero or more spaces and then newline or end-of-input.
+		// Spaces in the format before the newline are collapsed into the newline.
+		// Spaces in the format after the newline match zero or more spaces after the corresponding input newline.
+		// Other spaces in the format match input of one or more spaces or end-of-input.
+		if isSpace(fmtc) {
+			newlines := 0
+			trailingSpace := false
+			for isSpace(fmtc) && i < len(format) {
+				if fmtc == '\n' {
+					newlines++
+					trailingSpace = false
+				} else {
+					trailingSpace = true
+				}
+				i += w
+				fmtc, w = utf8.DecodeRuneInString(format[i:])
+			}
+			for j := 0; j < newlines; j++ {
+				inputc := s.getRune()
+				for isSpace(inputc) && inputc != '\n' {
+					inputc = s.getRune()
+				}
+				if inputc != '\n' && inputc != eof {
+					s.errorString("newline in format does not match input")
+				}
+			}
+			if trailingSpace {
+				inputc := s.getRune()
+				if newlines == 0 {
+					// If the trailing space stood alone (did not follow a newline),
+					// it must find at least one space to consume.
+					if !isSpace(inputc) && inputc != eof {
+						s.errorString("expected space in input to match format")
+					}
+					if inputc == '\n' {
+						s.errorString("newline in input does not match format")
+					}
+				}
+				for isSpace(inputc) && inputc != '\n' {
+					inputc = s.getRune()
+				}
+				if inputc != eof {
+					s.UnreadRune()
+				}
+			}
+			continue
+		}
+
+		// Verbs.
+		if fmtc == '%' {
+			// % at end of string is an error.
+			if i+w == len(format) {
+				s.errorString("missing verb: % at end of format string")
+			}
+			// %% acts like a real percent
+			nextc, _ := utf8.DecodeRuneInString(format[i+w:]) // will not match % if string is empty
+			if nextc != '%' {
+				return
+			}
+			i += w // skip the first %
+		}
+
+		// Literals.
+		inputc := s.mustReadRune()
+		if fmtc != inputc {
+			s.UnreadRune()
+			return -1
+		}
+		i += w
+	}
+	return
+}
+
+// doScanf does the real work when scanning with a format string.
+// At the moment, it handles only pointers to basic types.
+func (s *ss) doScanf(format string, a []interface{}) (numProcessed int, err error) {
+	defer errorHandler(&err)
+	end := len(format) - 1
+	// We process one item per non-trivial format
+	for i := 0; i <= end; {
+		w := s.advance(format[i:])
+		if w > 0 {
+			i += w
+			continue
+		}
+		// Either we failed to advance, we have a percent character, or we ran out of input.
+		if format[i] != '%' {
+			// Can't advance format. Why not?
+			if w < 0 {
+				s.errorString("input does not match format")
+			}
+			// Otherwise at EOF; "too many operands" error handled below
+			break
+		}
+		i++ // % is one byte
+
+		// do we have 20 (width)?
+		var widPresent bool
+		s.maxWid, widPresent, i = parsenum(format, i, end)
+		if !widPresent {
+			s.maxWid = hugeWid
+		}
+
+		c, w := utf8.DecodeRuneInString(format[i:])
+		i += w
+
+		if c != 'c' {
+			s.SkipSpace()
+		}
+		if c == '%' {
+			s.scanPercent()
+			continue // Do not consume an argument.
+		}
+		s.argLimit = s.limit
+		if f := s.count + s.maxWid; f < s.argLimit {
+			s.argLimit = f
+		}
+
+		if numProcessed >= len(a) { // out of operands
+			s.errorString("too few operands for format '%" + format[i-w:] + "'")
+			break
+		}
+		arg := a[numProcessed]
+
+		s.scanOne(c, arg)
+		numProcessed++
+		s.argLimit = s.limit
+	}
+	if numProcessed < len(a) {
+		s.errorString("too many operands")
+	}
+	return
+}