2010-05-25 22:02:35 -06:00
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// Copyright 2010 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package fmt
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import (
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"bytes"
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"io"
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"os"
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"reflect"
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"strconv"
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"unicode"
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"utf8"
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)
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// readRuner is the interface to something that can read runes. If
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// the object provided to Scan does not satisfy this interface, the
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// object will be wrapped by a readRune object.
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type readRuner interface {
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ReadRune() (rune int, size int, err os.Error)
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}
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2010-05-26 19:15:09 -06:00
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// ScanState represents the scanner state passed to custom scanners.
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// Scanners may do rune-at-a-time scanning or ask the ScanState
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// to discover the next space-delimited token.
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type ScanState interface {
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// GetRune reads the next rune (Unicode code point) from the input.
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GetRune() (rune int, err os.Error)
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// UngetRune causes the next call to Get to return the rune.
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UngetRune(rune int)
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// Token returns the next space-delimited token from the input.
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Token() (token string, err os.Error)
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}
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// Scanner is implemented by any value that has a Scan method, which scans
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// the input for the representation of a value and stores the result in the
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// receiver, which must be a pointer to be useful. The Scan method is called
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// for any argument to Scan or Scanln that implements it.
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type Scanner interface {
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Scan(ScanState) os.Error
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}
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// ss is the internal implementation of ScanState.
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type ss struct {
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rr readRuner // where to read input
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buf bytes.Buffer // token accumulator
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nlIsSpace bool // whether newline counts as white space
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peekRune int // one-rune lookahead
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err os.Error
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}
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func (s *ss) GetRune() (rune int, err os.Error) {
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if s.peekRune >= 0 {
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rune = s.peekRune
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s.peekRune = -1
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return
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}
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rune, _, err = s.rr.ReadRune()
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return
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}
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func (s *ss) UngetRune(rune int) {
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s.peekRune = rune
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}
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func (s *ss) Token() (tok string, err os.Error) {
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tok = s.token()
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err = s.err
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return
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}
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// readRune is a structure to enable reading UTF-8 encoded code points
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// from an io.Reader. It is used if the Reader given to the scanner does
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// not already implement ReadRuner.
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// TODO: readByteRune for things that can read bytes.
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type readRune struct {
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reader io.Reader
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buf [utf8.UTFMax]byte
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}
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// ReadRune returns the next UTF-8 encoded code point from the
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// io.Reader inside r.
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func (r readRune) ReadRune() (rune int, size int, err os.Error) {
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_, err = r.reader.Read(r.buf[0:1])
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if err != nil {
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return 0, 0, err
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}
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if r.buf[0] < utf8.RuneSelf { // fast check for common ASCII case
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rune = int(r.buf[0])
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return
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}
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for size := 1; size < utf8.UTFMax; size++ {
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_, err = r.reader.Read(r.buf[size : size+1])
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if err != nil {
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break
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}
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if !utf8.FullRune(&r.buf) {
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continue
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}
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if c, w := utf8.DecodeRune(r.buf[0:size]); w == size {
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rune = c
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return
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}
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}
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return utf8.RuneError, 1, err
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}
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// A leaky bucket of reusable ss structures.
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var ssFree = make(chan *ss, 100)
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// Allocate a new ss struct. Probably can grab the previous one from ssFree.
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func newScanState(r io.Reader, nlIsSpace bool) *ss {
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s, ok := <-ssFree
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if !ok {
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s = new(ss)
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}
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if rr, ok := r.(readRuner); ok {
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s.rr = rr
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} else {
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s.rr = readRune{reader: r}
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}
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s.nlIsSpace = nlIsSpace
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s.peekRune = -1
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s.err = nil
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return s
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}
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// Save used ss structs in ssFree; avoid an allocation per invocation.
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func (s *ss) free() {
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// Don't hold on to ss structs with large buffers.
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if cap(s.buf.Bytes()) > 1024 {
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return
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}
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s.buf.Reset()
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s.rr = nil
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_ = ssFree <- s
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}
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// token returns the next space-delimited string from the input.
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// For Scanln, it stops at newlines. For Scan, newlines are treated as
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// spaces.
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func (s *ss) token() string {
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s.buf.Reset()
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// skip white space and maybe newline
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for {
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rune, err := s.GetRune()
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if err != nil {
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s.err = err
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return ""
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}
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if rune == '\n' {
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if s.nlIsSpace {
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continue
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}
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s.err = os.ErrorString("unexpected newline")
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return ""
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}
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if !unicode.IsSpace(rune) {
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s.buf.WriteRune(rune)
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break
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}
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}
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// read until white space or newline
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for {
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rune, err := s.GetRune()
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if err != nil {
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if err == os.EOF {
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break
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}
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s.err = err
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return ""
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}
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if unicode.IsSpace(rune) {
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s.UngetRune(rune)
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break
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}
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s.buf.WriteRune(rune)
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}
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return s.buf.String()
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}
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// Scan parses text read from r, storing successive space-separated
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// values into successive arguments. Newlines count as space. Each
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// argument must be a pointer to a basic type. It returns the number of
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// items successfully parsed. If that is less than the number of arguments,
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// err will report why.
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func Scan(r io.Reader, a ...interface{}) (n int, err os.Error) {
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s := newScanState(r, true)
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n = s.doScan(a)
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err = s.err
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s.free()
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return
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}
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// Scanln parses text read from r, storing successive space-separated
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// values into successive arguments. Scanning stops at a newline and after
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// the final item there must be a newline or EOF. Each argument must be a
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// pointer to a basic type. It returns the number of items successfully
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// parsed. If that is less than the number of arguments, err will report
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// why.
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func Scanln(r io.Reader, a ...interface{}) (n int, err os.Error) {
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s := newScanState(r, false)
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n = s.doScan(a)
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err = s.err
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s.free()
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return
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}
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var intBits = uint(reflect.Typeof(int(0)).Size() * 8)
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var uintptrBits = uint(reflect.Typeof(int(0)).Size() * 8)
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var complexError = os.ErrorString("syntax error scanning complex number")
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// scanBool converts the token to a boolean value.
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func (s *ss) scanBool(tok string) bool {
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if s.err != nil {
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return false
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}
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var b bool
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b, s.err = strconv.Atob(tok)
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return b
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}
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// complexParts returns the strings representing the real and imaginary parts of the string.
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func (s *ss) complexParts(str string) (real, imag string) {
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if len(str) > 2 && str[0] == '(' && str[len(str)-1] == ')' {
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str = str[1 : len(str)-1]
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}
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real, str = floatPart(str)
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// Must now have a sign.
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if len(str) == 0 || (str[0] != '+' && str[0] != '-') {
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s.err = complexError
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return "", ""
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}
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imag, str = floatPart(str)
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if str != "i" {
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s.err = complexError
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return "", ""
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}
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return real, imag
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}
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// floatPart returns strings holding the floating point value in the string, followed
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// by the remainder of the string. That is, it splits str into (number,rest-of-string).
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func floatPart(str string) (first, last string) {
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i := 0
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// leading sign?
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if len(str) > 0 && (str[0] == '+' || str[0] == '-') {
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i++
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}
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// digits?
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for len(str) > 0 && '0' <= str[i] && str[i] <= '9' {
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i++
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}
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// period?
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if str[i] == '.' {
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i++
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}
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// fraction?
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for len(str) > 0 && '0' <= str[i] && str[i] <= '9' {
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i++
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}
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// exponent?
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if len(str) > 0 && (str[i] == 'e' || str[i] == 'E') {
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i++
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// leading sign?
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if str[0] == '+' || str[0] == '-' {
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i++
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}
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// digits?
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for len(str) > 0 && '0' <= str[i] && str[i] <= '9' {
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i++
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}
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}
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return str[0:i], str[i:]
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}
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// scanFloat converts the string to a float value.
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func (s *ss) scanFloat(str string) float64 {
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var f float
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f, s.err = strconv.Atof(str)
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return float64(f)
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}
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// scanFloat32 converts the string to a float32 value.
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func (s *ss) scanFloat32(str string) float64 {
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var f float32
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f, s.err = strconv.Atof32(str)
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return float64(f)
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}
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// scanFloat64 converts the string to a float64 value.
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func (s *ss) scanFloat64(str string) float64 {
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var f float64
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f, s.err = strconv.Atof64(str)
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return f
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}
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// scanComplex converts the token to a complex128 value.
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// The atof argument is a type-specific reader for the underlying type.
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// If we're reading complex64, atof will parse float32s and convert them
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// to float64's to avoid reproducing this code for each complex type.
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func (s *ss) scanComplex(tok string, atof func(*ss, string) float64) complex128 {
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if s.err != nil {
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return 0
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}
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sreal, simag := s.complexParts(tok)
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if s.err != nil {
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return 0
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}
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var real, imag float64
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real = atof(s, sreal)
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if s.err != nil {
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return 0
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}
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imag = atof(s, simag)
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if s.err != nil {
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return 0
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}
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return cmplx(real, imag)
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}
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// scanInt converts the token to an int64, but checks that it fits into the
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// specified number of bits.
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func (s *ss) scanInt(tok string, bitSize uint) int64 {
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if s.err != nil {
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return 0
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}
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var i int64
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i, s.err = strconv.Atoi64(tok)
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x := (i << (64 - bitSize)) >> (64 - bitSize)
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if i != x {
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s.err = os.ErrorString("integer overflow on token " + tok)
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}
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return i
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}
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// scanUint converts the token to a uint64, but checks that it fits into the
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// specified number of bits.
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func (s *ss) scanUint(tok string, bitSize uint) uint64 {
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if s.err != nil {
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return 0
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}
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var i uint64
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i, s.err = strconv.Atoui64(tok)
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x := (i << (64 - bitSize)) >> (64 - bitSize)
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if i != x {
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s.err = os.ErrorString("unsigned integer overflow on token " + tok)
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}
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return i
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}
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// doScan does the real work. At the moment, it handles only pointers to basic types.
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func (s *ss) doScan(a []interface{}) int {
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for n, param := range a {
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// If the parameter has its own Scan method, use that.
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if v, ok := param.(Scanner); ok {
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s.err = v.Scan(s)
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if s.err != nil {
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return n
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}
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continue
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}
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tok := s.token()
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switch v := param.(type) {
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case *bool:
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*v = s.scanBool(tok)
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case *complex:
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*v = complex(s.scanComplex(tok, (*ss).scanFloat))
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case *complex64:
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*v = complex64(s.scanComplex(tok, (*ss).scanFloat32))
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case *complex128:
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*v = s.scanComplex(tok, (*ss).scanFloat64)
|
|
|
|
case *int:
|
|
|
|
*v = int(s.scanInt(tok, intBits))
|
|
|
|
case *int8:
|
|
|
|
*v = int8(s.scanInt(tok, 8))
|
|
|
|
case *int16:
|
|
|
|
*v = int16(s.scanInt(tok, 16))
|
|
|
|
case *int32:
|
|
|
|
*v = int32(s.scanInt(tok, 32))
|
|
|
|
case *int64:
|
|
|
|
*v = s.scanInt(tok, 64)
|
|
|
|
case *uint:
|
|
|
|
*v = uint(s.scanUint(tok, intBits))
|
|
|
|
case *uint8:
|
|
|
|
*v = uint8(s.scanUint(tok, 8))
|
|
|
|
case *uint16:
|
|
|
|
*v = uint16(s.scanUint(tok, 16))
|
|
|
|
case *uint32:
|
|
|
|
*v = uint32(s.scanUint(tok, 32))
|
|
|
|
case *uint64:
|
|
|
|
*v = s.scanUint(tok, 64)
|
|
|
|
case *uintptr:
|
|
|
|
*v = uintptr(s.scanUint(tok, uintptrBits))
|
|
|
|
case *float:
|
|
|
|
if s.err == nil {
|
|
|
|
*v, s.err = strconv.Atof(tok)
|
|
|
|
} else {
|
|
|
|
*v = 0
|
|
|
|
}
|
|
|
|
case *float32:
|
|
|
|
if s.err == nil {
|
|
|
|
*v, s.err = strconv.Atof32(tok)
|
|
|
|
} else {
|
|
|
|
*v = 0
|
|
|
|
}
|
|
|
|
case *float64:
|
|
|
|
if s.err == nil {
|
|
|
|
*v, s.err = strconv.Atof64(tok)
|
|
|
|
} else {
|
|
|
|
*v = 0
|
|
|
|
}
|
|
|
|
case *string:
|
|
|
|
*v = tok
|
|
|
|
default:
|
|
|
|
t := reflect.Typeof(v)
|
|
|
|
str := t.String()
|
|
|
|
if _, ok := t.(*reflect.PtrType); !ok {
|
|
|
|
s.err = os.ErrorString("Scan: type not a pointer: " + str)
|
|
|
|
} else {
|
|
|
|
s.err = os.ErrorString("Scan: can't handle type: " + str)
|
|
|
|
}
|
|
|
|
}
|
|
|
|
if s.err != nil {
|
|
|
|
return n
|
|
|
|
}
|
|
|
|
}
|
|
|
|
// Check for newline if required.
|
|
|
|
if !s.nlIsSpace {
|
|
|
|
for {
|
2010-05-26 19:15:09 -06:00
|
|
|
rune, err := s.GetRune()
|
2010-05-25 22:02:35 -06:00
|
|
|
if err != nil {
|
|
|
|
if err == os.EOF {
|
|
|
|
break
|
|
|
|
}
|
|
|
|
s.err = err
|
|
|
|
break
|
|
|
|
}
|
|
|
|
if rune == '\n' {
|
|
|
|
break
|
|
|
|
}
|
|
|
|
if !unicode.IsSpace(rune) {
|
|
|
|
s.err = os.ErrorString("Scan: expected newline")
|
|
|
|
break
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
return len(a)
|
|
|
|
}
|