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sago35/errors.go

Created May 17, 2022 11:52
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TinyGo : fmt package for debugging the machine package
Raw
errors.go
// Copyright 2018 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"
// Errorf formats according to a format specifier and returns the string as a
// value that satisfies error.
//
// If the format specifier includes a %w verb with an error operand,
// the returned error will implement an Unwrap method returning the operand. It is
// invalid to include more than one %w verb or to supply it with an operand
// that does not implement the error interface. The %w verb is otherwise
// a synonym for %v.
func Errorf(format string, a ...any) error {
p := newPrinter()
p.wrapErrs = true
p.doPrintf(format, a)
s := string(p.buf)
var err error
if p.wrappedErr == nil {
err = errors.New(s)
} else {
err = &wrapError{s, p.wrappedErr}
}
p.free()
return err
}
type wrapError struct {
msg string
err error
}
func (e *wrapError) Error() string {
return e.msg
}
func (e *wrapError) Unwrap() error {
return e.err
}
Raw
format.go
// Copyright 2009 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 (
"strconv"
"unicode/utf8"
)
const (
ldigits = "0123456789abcdefx"
udigits = "0123456789ABCDEFX"
)
const (
signed = true
unsigned = false
)
// flags placed in a separate struct for easy clearing.
type fmtFlags struct {
widPresent bool
precPresent bool
minus bool
plus bool
sharp bool
space bool
zero bool
// For the formats %+v %#v, we set the plusV/sharpV flags
// and clear the plus/sharp flags since %+v and %#v are in effect
// different, flagless formats set at the top level.
plusV bool
sharpV bool
}
// A fmt is the raw formatter used by Printf etc.
// It prints into a buffer that must be set up separately.
type fmt struct {
buf *buffer
fmtFlags
wid int // width
prec int // precision
// intbuf is large enough to store %b of an int64 with a sign and
// avoids padding at the end of the struct on 32 bit architectures.
intbuf [68]byte
}
func (f *fmt) clearflags() {
f.fmtFlags = fmtFlags{}
}
func (f *fmt) init(buf *buffer) {
f.buf = buf
f.clearflags()
}
// writePadding generates n bytes of padding.
func (f *fmt) writePadding(n int) {
if n <= 0 { // No padding bytes needed.
return
}
buf := *f.buf
oldLen := len(buf)
newLen := oldLen + n
// Make enough room for padding.
if newLen > cap(buf) {
buf = make(buffer, cap(buf)*2+n)
copy(buf, *f.buf)
}
// Decide which byte the padding should be filled with.
padByte := byte(' ')
if f.zero {
padByte = byte('0')
}
// Fill padding with padByte.
padding := buf[oldLen:newLen]
for i := range padding {
padding[i] = padByte
}
*f.buf = buf[:newLen]
}
// pad appends b to f.buf, padded on left (!f.minus) or right (f.minus).
func (f *fmt) pad(b []byte) {
if !f.widPresent || f.wid == 0 {
f.buf.write(b)
return
}
width := f.wid - utf8.RuneCount(b)
if !f.minus {
// left padding
f.writePadding(width)
f.buf.write(b)
} else {
// right padding
f.buf.write(b)
f.writePadding(width)
}
}
// padString appends s to f.buf, padded on left (!f.minus) or right (f.minus).
func (f *fmt) padString(s string) {
if !f.widPresent || f.wid == 0 {
f.buf.writeString(s)
return
}
width := f.wid - utf8.RuneCountInString(s)
if !f.minus {
// left padding
f.writePadding(width)
f.buf.writeString(s)
} else {
// right padding
f.buf.writeString(s)
f.writePadding(width)
}
}
// fmtBoolean formats a boolean.
func (f *fmt) fmtBoolean(v bool) {
if v {
f.padString("true")
} else {
f.padString("false")
}
}
// fmtUnicode formats a uint64 as "U+0078" or with f.sharp set as "U+0078 'x'".
func (f *fmt) fmtUnicode(u uint64) {
buf := f.intbuf[0:]
// With default precision set the maximum needed buf length is 18
// for formatting -1 with %#U ("U+FFFFFFFFFFFFFFFF") which fits
// into the already allocated intbuf with a capacity of 68 bytes.
prec := 4
if f.precPresent && f.prec > 4 {
prec = f.prec
// Compute space needed for "U+" , number, " '", character, "'".
width := 2 + prec + 2 + utf8.UTFMax + 1
if width > len(buf) {
buf = make([]byte, width)
}
}
// Format into buf, ending at buf[i]. Formatting numbers is easier right-to-left.
i := len(buf)
// For %#U we want to add a space and a quoted character at the end of the buffer.
if f.sharp && u <= utf8.MaxRune && strconv.IsPrint(rune(u)) {
i--
buf[i] = '\''
i -= utf8.RuneLen(rune(u))
utf8.EncodeRune(buf[i:], rune(u))
i--
buf[i] = '\''
i--
buf[i] = ' '
}
// Format the Unicode code point u as a hexadecimal number.
for u >= 16 {
i--
buf[i] = udigits[u&0xF]
prec--
u >>= 4
}
i--
buf[i] = udigits[u]
prec--
// Add zeros in front of the number until requested precision is reached.
for prec > 0 {
i--
buf[i] = '0'
prec--
}
// Add a leading "U+".
i--
buf[i] = '+'
i--
buf[i] = 'U'
oldZero := f.zero
f.zero = false
f.pad(buf[i:])
f.zero = oldZero
}
// fmtInteger formats signed and unsigned integers.
func (f *fmt) fmtInteger(u uint64, base int, isSigned bool, verb rune, digits string) {
negative := isSigned && int64(u) < 0
if negative {
u = -u
}
buf := f.intbuf[0:]
// The already allocated f.intbuf with a capacity of 68 bytes
// is large enough for integer formatting when no precision or width is set.
if f.widPresent || f.precPresent {
// Account 3 extra bytes for possible addition of a sign and "0x".
width := 3 + f.wid + f.prec // wid and prec are always positive.
if width > len(buf) {
// We're going to need a bigger boat.
buf = make([]byte, width)
}
}
// Two ways to ask for extra leading zero digits: %.3d or %03d.
// If both are specified the f.zero flag is ignored and
// padding with spaces is used instead.
prec := 0
if f.precPresent {
prec = f.prec
// Precision of 0 and value of 0 means "print nothing" but padding.
if prec == 0 && u == 0 {
oldZero := f.zero
f.zero = false
f.writePadding(f.wid)
f.zero = oldZero
return
}
} else if f.zero && f.widPresent {
prec = f.wid
if negative || f.plus || f.space {
prec-- // leave room for sign
}
}
// Because printing is easier right-to-left: format u into buf, ending at buf[i].
// We could make things marginally faster by splitting the 32-bit case out
// into a separate block but it's not worth the duplication, so u has 64 bits.
i := len(buf)
// Use constants for the division and modulo for more efficient code.
// Switch cases ordered by popularity.
switch base {
case 10:
for u >= 10 {
i--
next := u / 10
buf[i] = byte('0' + u - next*10)
u = next
}
case 16:
for u >= 16 {
i--
buf[i] = digits[u&0xF]
u >>= 4
}
case 8:
for u >= 8 {
i--
buf[i] = byte('0' + u&7)
u >>= 3
}
case 2:
for u >= 2 {
i--
buf[i] = byte('0' + u&1)
u >>= 1
}
default:
panic("fmt: unknown base; can't happen")
}
i--
buf[i] = digits[u]
for i > 0 && prec > len(buf)-i {
i--
buf[i] = '0'
}
// Various prefixes: 0x, -, etc.
if f.sharp {
switch base {
case 2:
// Add a leading 0b.
i--
buf[i] = 'b'
i--
buf[i] = '0'
case 8:
if buf[i] != '0' {
i--
buf[i] = '0'
}
case 16:
// Add a leading 0x or 0X.
i--
buf[i] = digits[16]
i--
buf[i] = '0'
}
}
if verb == 'O' {
i--
buf[i] = 'o'
i--
buf[i] = '0'
}
if negative {
i--
buf[i] = '-'
} else if f.plus {
i--
buf[i] = '+'
} else if f.space {
i--
buf[i] = ' '
}
// Left padding with zeros has already been handled like precision earlier
// or the f.zero flag is ignored due to an explicitly set precision.
oldZero := f.zero
f.zero = false
f.pad(buf[i:])
f.zero = oldZero
}
// truncateString truncates the string s to the specified precision, if present.
func (f *fmt) truncateString(s string) string {
if f.precPresent {
n := f.prec
for i := range s {
n--
if n < 0 {
return s[:i]
}
}
}
return s
}
// truncate truncates the byte slice b as a string of the specified precision, if present.
func (f *fmt) truncate(b []byte) []byte {
if f.precPresent {
n := f.prec
for i := 0; i < len(b); {
n--
if n < 0 {
return b[:i]
}
wid := 1
if b[i] >= utf8.RuneSelf {
_, wid = utf8.DecodeRune(b[i:])
}
i += wid
}
}
return b
}
// fmtS formats a string.
func (f *fmt) fmtS(s string) {
s = f.truncateString(s)
f.padString(s)
}
// fmtBs formats the byte slice b as if it was formatted as string with fmtS.
func (f *fmt) fmtBs(b []byte) {
b = f.truncate(b)
f.pad(b)
}
// fmtSbx formats a string or byte slice as a hexadecimal encoding of its bytes.
func (f *fmt) fmtSbx(s string, b []byte, digits string) {
length := len(b)
if b == nil {
// No byte slice present. Assume string s should be encoded.
length = len(s)
}
// Set length to not process more bytes than the precision demands.
if f.precPresent && f.prec < length {
length = f.prec
}
// Compute width of the encoding taking into account the f.sharp and f.space flag.
width := 2 * length
if width > 0 {
if f.space {
// Each element encoded by two hexadecimals will get a leading 0x or 0X.
if f.sharp {
width *= 2
}
// Elements will be separated by a space.
width += length - 1
} else if f.sharp {
// Only a leading 0x or 0X will be added for the whole string.
width += 2
}
} else { // The byte slice or string that should be encoded is empty.
if f.widPresent {
f.writePadding(f.wid)
}
return
}
// Handle padding to the left.
if f.widPresent && f.wid > width && !f.minus {
f.writePadding(f.wid - width)
}
// Write the encoding directly into the output buffer.
buf := *f.buf
if f.sharp {
// Add leading 0x or 0X.
buf = append(buf, '0', digits[16])
}
var c byte
for i := 0; i < length; i++ {
if f.space && i > 0 {
// Separate elements with a space.
buf = append(buf, ' ')
if f.sharp {
// Add leading 0x or 0X for each element.
buf = append(buf, '0', digits[16])
}
}
if b != nil {
c = b[i] // Take a byte from the input byte slice.
} else {
c = s[i] // Take a byte from the input string.
}
// Encode each byte as two hexadecimal digits.
buf = append(buf, digits[c>>4], digits[c&0xF])
}
*f.buf = buf
// Handle padding to the right.
if f.widPresent && f.wid > width && f.minus {
f.writePadding(f.wid - width)
}
}
// fmtSx formats a string as a hexadecimal encoding of its bytes.
func (f *fmt) fmtSx(s, digits string) {
f.fmtSbx(s, nil, digits)
}
// fmtBx formats a byte slice as a hexadecimal encoding of its bytes.
func (f *fmt) fmtBx(b []byte, digits string) {
f.fmtSbx("", b, digits)
}
// fmtQ formats a string as a double-quoted, escaped Go string constant.
// If f.sharp is set a raw (backquoted) string may be returned instead
// if the string does not contain any control characters other than tab.
func (f *fmt) fmtQ(s string) {
s = f.truncateString(s)
if f.sharp && strconv.CanBackquote(s) {
f.padString("`" + s + "`")
return
}
buf := f.intbuf[:0]
if f.plus {
f.pad(strconv.AppendQuoteToASCII(buf, s))
} else {
f.pad(strconv.AppendQuote(buf, s))
}
}
// fmtC formats an integer as a Unicode character.
// If the character is not valid Unicode, it will print '\ufffd'.
func (f *fmt) fmtC(c uint64) {
r := rune(c)
if c > utf8.MaxRune {
r = utf8.RuneError
}
buf := f.intbuf[:0]
w := utf8.EncodeRune(buf[:utf8.UTFMax], r)
f.pad(buf[:w])
}
// fmtQc formats an integer as a single-quoted, escaped Go character constant.
// If the character is not valid Unicode, it will print '\ufffd'.
func (f *fmt) fmtQc(c uint64) {
r := rune(c)
if c > utf8.MaxRune {
r = utf8.RuneError
}
buf := f.intbuf[:0]
if f.plus {
f.pad(strconv.AppendQuoteRuneToASCII(buf, r))
} else {
f.pad(strconv.AppendQuoteRune(buf, r))
}
}
// fmtFloat formats a float64. It assumes that verb is a valid format specifier
// for strconv.AppendFloat and therefore fits into a byte.
func (f *fmt) fmtFloat(v float64, size int, verb rune, prec int) {
// Explicit precision in format specifier overrules default precision.
if f.precPresent {
prec = f.prec
}
// Format number, reserving space for leading + sign if needed.
num := strconv.AppendFloat(f.intbuf[:1], v, byte(verb), prec, size)
if num[1] == '-' || num[1] == '+' {
num = num[1:]
} else {
num[0] = '+'
}
// f.space means to add a leading space instead of a "+" sign unless
// the sign is explicitly asked for by f.plus.
if f.space && num[0] == '+' && !f.plus {
num[0] = ' '
}
// Special handling for infinities and NaN,
// which don't look like a number so shouldn't be padded with zeros.
if num[1] == 'I' || num[1] == 'N' {
oldZero := f.zero
f.zero = false
// Remove sign before NaN if not asked for.
if num[1] == 'N' && !f.space && !f.plus {
num = num[1:]
}
f.pad(num)
f.zero = oldZero
return
}
// The sharp flag forces printing a decimal point for non-binary formats
// and retains trailing zeros, which we may need to restore.
if f.sharp && verb != 'b' {
digits := 0
switch verb {
case 'v', 'g', 'G', 'x':
digits = prec
// If no precision is set explicitly use a precision of 6.
if digits == -1 {
digits = 6
}
}
// Buffer pre-allocated with enough room for
// exponent notations of the form "e+123" or "p-1023".
var tailBuf [6]byte
tail := tailBuf[:0]
hasDecimalPoint := false
sawNonzeroDigit := false
// Starting from i = 1 to skip sign at num[0].
for i := 1; i < len(num); i++ {
switch num[i] {
case '.':
hasDecimalPoint = true
case 'p', 'P':
tail = append(tail, num[i:]...)
num = num[:i]
case 'e', 'E':
if verb != 'x' && verb != 'X' {
tail = append(tail, num[i:]...)
num = num[:i]
break
}
fallthrough
default:
if num[i] != '0' {
sawNonzeroDigit = true
}
// Count significant digits after the first non-zero digit.
if sawNonzeroDigit {
digits--
}
}
}
if !hasDecimalPoint {
// Leading digit 0 should contribute once to digits.
if len(num) == 2 && num[1] == '0' {
digits--
}
num = append(num, '.')
}
for digits > 0 {
num = append(num, '0')
digits--
}
num = append(num, tail...)
}
// We want a sign if asked for and if the sign is not positive.
if f.plus || num[0] != '+' {
// If we're zero padding to the left we want the sign before the leading zeros.
// Achieve this by writing the sign out and then padding the unsigned number.
if f.zero && f.widPresent && f.wid > len(num) {
f.buf.writeByte(num[0])
f.writePadding(f.wid - len(num))
f.buf.write(num[1:])
return
}
f.pad(num)
return
}
// No sign to show and the number is positive; just print the unsigned number.
f.pad(num[1:])
}
Raw
print.go
// Copyright 2009 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 (
"internal/fmtsort"
"io"
"reflect"
"sync"
"unicode/utf8"
)
// Strings for use with buffer.WriteString.
// This is less overhead than using buffer.Write with byte arrays.
const (
commaSpaceString = ", "
nilAngleString = "<nil>"
nilParenString = "(nil)"
nilString = "nil"
mapString = "map["
percentBangString = "%!"
missingString = "(MISSING)"
badIndexString = "(BADINDEX)"
panicString = "(PANIC="
extraString = "%!(EXTRA "
badWidthString = "%!(BADWIDTH)"
badPrecString = "%!(BADPREC)"
noVerbString = "%!(NOVERB)"
invReflectString = "<invalid reflect.Value>"
)
// State represents the printer state passed to custom formatters.
// It provides access to the io.Writer interface plus information about
// the flags and options for the operand's format specifier.
type State interface {
// Write is the function to call to emit formatted output to be printed.
Write(b []byte) (n int, err error)
// Width returns the value of the width option and whether it has been set.
Width() (wid int, ok bool)
// Precision returns the value of the precision option and whether it has been set.
Precision() (prec int, ok bool)
// Flag reports whether the flag c, a character, has been set.
Flag(c int) bool
}
// Formatter is implemented by any value that has a Format method.
// The implementation controls how State and rune are interpreted,
// and may call Sprint(f) or Fprint(f) etc. to generate its output.
type Formatter interface {
Format(f State, verb rune)
}
// Stringer is implemented by any value that has a String method,
// which defines the ``native'' format for that value.
// The String method is used to print values passed as an operand
// to any format that accepts a string or to an unformatted printer
// such as Print.
type Stringer interface {
String() string
}
// GoStringer is implemented by any value that has a GoString method,
// which defines the Go syntax for that value.
// The GoString method is used to print values passed as an operand
// to a %#v format.
type GoStringer interface {
GoString() string
}
// Use simple []byte instead of bytes.Buffer to avoid large dependency.
type buffer []byte
func (b *buffer) write(p []byte) {
*b = append(*b, p...)
}
func (b *buffer) writeString(s string) {
*b = append(*b, s...)
}
func (b *buffer) writeByte(c byte) {
*b = append(*b, c)
}
func (bp *buffer) writeRune(r rune) {
if r < utf8.RuneSelf {
*bp = append(*bp, byte(r))
return
}
b := *bp
n := len(b)
for n+utf8.UTFMax > cap(b) {
b = append(b, 0)
}
w := utf8.EncodeRune(b[n:n+utf8.UTFMax], r)
*bp = b[:n+w]
}
// pp is used to store a printer's state and is reused with sync.Pool to avoid allocations.
type pp struct {
buf buffer
// arg holds the current item, as an interface{}.
arg any
// value is used instead of arg for reflect values.
value reflect.Value
// fmt is used to format basic items such as integers or strings.
fmt fmt
// reordered records whether the format string used argument reordering.
reordered bool
// goodArgNum records whether the most recent reordering directive was valid.
goodArgNum bool
// panicking is set by catchPanic to avoid infinite panic, recover, panic, ... recursion.
panicking bool
// erroring is set when printing an error string to guard against calling handleMethods.
erroring bool
// wrapErrs is set when the format string may contain a %w verb.
wrapErrs bool
// wrappedErr records the target of the %w verb.
wrappedErr error
}
var ppFree = sync.Pool{
New: func() any { return new(pp) },
}
// newPrinter allocates a new pp struct or grabs a cached one.
func newPrinter() *pp {
p := ppFree.Get().(*pp)
p.panicking = false
p.erroring = false
p.wrapErrs = false
p.fmt.init(&p.buf)
return p
}
// free saves used pp structs in ppFree; avoids an allocation per invocation.
func (p *pp) free() {
// Proper usage of a sync.Pool requires each entry to have approximately
// the same memory cost. To obtain this property when the stored type
// contains a variably-sized buffer, we add a hard limit on the maximum buffer
// to place back in the pool.
//
// See https://golang.org/issue/23199
if cap(p.buf) > 64<<10 {
return
}
p.buf = p.buf[:0]
p.arg = nil
p.value = reflect.Value{}
p.wrappedErr = nil
ppFree.Put(p)
}
func (p *pp) Width() (wid int, ok bool) { return p.fmt.wid, p.fmt.widPresent }
func (p *pp) Precision() (prec int, ok bool) { return p.fmt.prec, p.fmt.precPresent }
func (p *pp) Flag(b int) bool {
switch b {
case '-':
return p.fmt.minus
case '+':
return p.fmt.plus || p.fmt.plusV
case '#':
return p.fmt.sharp || p.fmt.sharpV
case ' ':
return p.fmt.space
case '0':
return p.fmt.zero
}
return false
}
// Implement Write so we can call Fprintf on a pp (through State), for
// recursive use in custom verbs.
func (p *pp) Write(b []byte) (ret int, err error) {
p.buf.write(b)
return len(b), nil
}
// Implement WriteString so that we can call io.WriteString
// on a pp (through state), for efficiency.
func (p *pp) WriteString(s string) (ret int, err error) {
p.buf.writeString(s)
return len(s), nil
}
// These routines end in 'f' and take a format string.
// Fprintf formats according to a format specifier and writes to w.
// It returns the number of bytes written and any write error encountered.
func Fprintf(w io.Writer, format string, a ...any) (n int, err error) {
p := newPrinter()
p.doPrintf(format, a)
n, err = w.Write(p.buf)
p.free()
return
}
//// Printf formats according to a format specifier and writes to standard output.
//// It returns the number of bytes written and any write error encountered.
//func Printf(format string, a ...any) (n int, err error) {
// return Fprintf(os.Stdout, format, a...)
//}
// Sprintf formats according to a format specifier and returns the resulting string.
func Sprintf(format string, a ...any) string {
p := newPrinter()
p.doPrintf(format, a)
s := string(p.buf)
p.free()
return s
}
// These routines do not take a format string
// Fprint formats using the default formats for its operands and writes to w.
// Spaces are added between operands when neither is a string.
// It returns the number of bytes written and any write error encountered.
func Fprint(w io.Writer, a ...any) (n int, err error) {
p := newPrinter()
p.doPrint(a)
n, err = w.Write(p.buf)
p.free()
return
}
//// Print formats using the default formats for its operands and writes to standard output.
//// Spaces are added between operands when neither is a string.
//// It returns the number of bytes written and any write error encountered.
//func Print(a ...any) (n int, err error) {
// return Fprint(os.Stdout, a...)
//}
// Sprint formats using the default formats for its operands and returns the resulting string.
// Spaces are added between operands when neither is a string.
func Sprint(a ...any) string {
p := newPrinter()
p.doPrint(a)
s := string(p.buf)
p.free()
return s
}
// These routines end in 'ln', do not take a format string,
// always add spaces between operands, and add a newline
// after the last operand.
// Fprintln formats using the default formats for its operands and writes to w.
// Spaces are always added between operands and a newline is appended.
// It returns the number of bytes written and any write error encountered.
func Fprintln(w io.Writer, a ...any) (n int, err error) {
p := newPrinter()
p.doPrintln(a)
n, err = w.Write(p.buf)
p.free()
return
}
//// Println formats using the default formats for its operands and writes to standard output.
//// Spaces are always added between operands and a newline is appended.
//// It returns the number of bytes written and any write error encountered.
//func Println(a ...any) (n int, err error) {
// return Fprintln(os.Stdout, a...)
//}
// Sprintln formats using the default formats for its operands and returns the resulting string.
// Spaces are always added between operands and a newline is appended.
func Sprintln(a ...any) string {
p := newPrinter()
p.doPrintln(a)
s := string(p.buf)
p.free()
return s
}
// getField gets the i'th field of the struct value.
// If the field is itself is an interface, return a value for
// the thing inside the interface, not the interface itself.
func getField(v reflect.Value, i int) reflect.Value {
val := v.Field(i)
if val.Kind() == reflect.Interface && !val.IsNil() {
val = val.Elem()
}
return val
}
// tooLarge reports whether the magnitude of the integer is
// too large to be used as a formatting width or precision.
func tooLarge(x int) bool {
const max int = 1e6
return x > max || x < -max
}
// parsenum converts ASCII to integer. num is 0 (and isnum is false) if no number present.
func parsenum(s string, start, end int) (num int, isnum bool, newi int) {
if start >= end {
return 0, false, end
}
for newi = start; newi < end && '0' <= s[newi] && s[newi] <= '9'; newi++ {
if tooLarge(num) {
return 0, false, end // Overflow; crazy long number most likely.
}
num = num*10 + int(s[newi]-'0')
isnum = true
}
return
}
func (p *pp) unknownType(v reflect.Value) {
if !v.IsValid() {
p.buf.writeString(nilAngleString)
return
}
p.buf.writeByte('?')
p.buf.writeString(v.Type().String())
p.buf.writeByte('?')
}
func (p *pp) badVerb(verb rune) {
p.erroring = true
p.buf.writeString(percentBangString)
p.buf.writeRune(verb)
p.buf.writeByte('(')
switch {
case p.arg != nil:
p.buf.writeString(reflect.TypeOf(p.arg).String())
p.buf.writeByte('=')
p.printArg(p.arg, 'v')
case p.value.IsValid():
p.buf.writeString(p.value.Type().String())
p.buf.writeByte('=')
p.printValue(p.value, 'v', 0)
default:
p.buf.writeString(nilAngleString)
}
p.buf.writeByte(')')
p.erroring = false
}
func (p *pp) fmtBool(v bool, verb rune) {
switch verb {
case 't', 'v':
p.fmt.fmtBoolean(v)
default:
p.badVerb(verb)
}
}
// fmt0x64 formats a uint64 in hexadecimal and prefixes it with 0x or
// not, as requested, by temporarily setting the sharp flag.
func (p *pp) fmt0x64(v uint64, leading0x bool) {
sharp := p.fmt.sharp
p.fmt.sharp = leading0x
p.fmt.fmtInteger(v, 16, unsigned, 'v', ldigits)
p.fmt.sharp = sharp
}
// fmtInteger formats a signed or unsigned integer.
func (p *pp) fmtInteger(v uint64, isSigned bool, verb rune) {
switch verb {
case 'v':
if p.fmt.sharpV && !isSigned {
p.fmt0x64(v, true)
} else {
p.fmt.fmtInteger(v, 10, isSigned, verb, ldigits)
}
case 'd':
p.fmt.fmtInteger(v, 10, isSigned, verb, ldigits)
case 'b':
p.fmt.fmtInteger(v, 2, isSigned, verb, ldigits)
case 'o', 'O':
p.fmt.fmtInteger(v, 8, isSigned, verb, ldigits)
case 'x':
p.fmt.fmtInteger(v, 16, isSigned, verb, ldigits)
case 'X':
p.fmt.fmtInteger(v, 16, isSigned, verb, udigits)
case 'c':
p.fmt.fmtC(v)
case 'q':
p.fmt.fmtQc(v)
case 'U':
p.fmt.fmtUnicode(v)
default:
p.badVerb(verb)
}
}
// fmtFloat formats a float. The default precision for each verb
// is specified as last argument in the call to fmt_float.
func (p *pp) fmtFloat(v float64, size int, verb rune) {
switch verb {
case 'v':
p.fmt.fmtFloat(v, size, 'g', -1)
case 'b', 'g', 'G', 'x', 'X':
p.fmt.fmtFloat(v, size, verb, -1)
case 'f', 'e', 'E':
p.fmt.fmtFloat(v, size, verb, 6)
case 'F':
p.fmt.fmtFloat(v, size, 'f', 6)
default:
p.badVerb(verb)
}
}
// fmtComplex formats a complex number v with
// r = real(v) and j = imag(v) as (r+ji) using
// fmtFloat for r and j formatting.
func (p *pp) fmtComplex(v complex128, size int, verb rune) {
// Make sure any unsupported verbs are found before the
// calls to fmtFloat to not generate an incorrect error string.
switch verb {
case 'v', 'b', 'g', 'G', 'x', 'X', 'f', 'F', 'e', 'E':
oldPlus := p.fmt.plus
p.buf.writeByte('(')
p.fmtFloat(real(v), size/2, verb)
// Imaginary part always has a sign.
p.fmt.plus = true
p.fmtFloat(imag(v), size/2, verb)
p.buf.writeString("i)")
p.fmt.plus = oldPlus
default:
p.badVerb(verb)
}
}
func (p *pp) fmtString(v string, verb rune) {
switch verb {
case 'v':
if p.fmt.sharpV {
p.fmt.fmtQ(v)
} else {
p.fmt.fmtS(v)
}
case 's':
p.fmt.fmtS(v)
case 'x':
p.fmt.fmtSx(v, ldigits)
case 'X':
p.fmt.fmtSx(v, udigits)
case 'q':
p.fmt.fmtQ(v)
default:
p.badVerb(verb)
}
}
func (p *pp) fmtBytes(v []byte, verb rune, typeString string) {
switch verb {
case 'v', 'd':
if p.fmt.sharpV {
p.buf.writeString(typeString)
if v == nil {
p.buf.writeString(nilParenString)
return
}
p.buf.writeByte('{')
for i, c := range v {
if i > 0 {
p.buf.writeString(commaSpaceString)
}
p.fmt0x64(uint64(c), true)
}
p.buf.writeByte('}')
} else {
p.buf.writeByte('[')
for i, c := range v {
if i > 0 {
p.buf.writeByte(' ')
}
p.fmt.fmtInteger(uint64(c), 10, unsigned, verb, ldigits)
}
p.buf.writeByte(']')
}
case 's':
p.fmt.fmtBs(v)
case 'x':
p.fmt.fmtBx(v, ldigits)
case 'X':
p.fmt.fmtBx(v, udigits)
case 'q':
p.fmt.fmtQ(string(v))
default:
p.printValue(reflect.ValueOf(v), verb, 0)
}
}
func (p *pp) fmtPointer(value reflect.Value, verb rune) {
var u uintptr
switch value.Kind() {
case reflect.Chan, reflect.Func, reflect.Map, reflect.Pointer, reflect.Slice, reflect.UnsafePointer:
u = value.Pointer()
default:
p.badVerb(verb)
return
}
switch verb {
case 'v':
if p.fmt.sharpV {
p.buf.writeByte('(')
p.buf.writeString(value.Type().String())
p.buf.writeString(")(")
if u == 0 {
p.buf.writeString(nilString)
} else {
p.fmt0x64(uint64(u), true)
}
p.buf.writeByte(')')
} else {
if u == 0 {
p.fmt.padString(nilAngleString)
} else {
p.fmt0x64(uint64(u), !p.fmt.sharp)
}
}
case 'p':
p.fmt0x64(uint64(u), !p.fmt.sharp)
case 'b', 'o', 'd', 'x', 'X':
p.fmtInteger(uint64(u), unsigned, verb)
default:
p.badVerb(verb)
}
}
func (p *pp) catchPanic(arg any, verb rune, method string) {
if err := recover(); err != nil {
// If it's a nil pointer, just say "<nil>". The likeliest causes are a
// Stringer that fails to guard against nil or a nil pointer for a
// value receiver, and in either case, "<nil>" is a nice result.
if v := reflect.ValueOf(arg); v.Kind() == reflect.Pointer && v.IsNil() {
p.buf.writeString(nilAngleString)
return
}
// Otherwise print a concise panic message. Most of the time the panic
// value will print itself nicely.
if p.panicking {
// Nested panics; the recursion in printArg cannot succeed.
panic(err)
}
oldFlags := p.fmt.fmtFlags
// For this output we want default behavior.
p.fmt.clearflags()
p.buf.writeString(percentBangString)
p.buf.writeRune(verb)
p.buf.writeString(panicString)
p.buf.writeString(method)
p.buf.writeString(" method: ")
p.panicking = true
p.printArg(err, 'v')
p.panicking = false
p.buf.writeByte(')')
p.fmt.fmtFlags = oldFlags
}
}
func (p *pp) handleMethods(verb rune) (handled bool) {
if p.erroring {
return
}
if verb == 'w' {
// It is invalid to use %w other than with Errorf, more than once,
// or with a non-error arg.
err, ok := p.arg.(error)
if !ok || !p.wrapErrs || p.wrappedErr != nil {
p.wrappedErr = nil
p.wrapErrs = false
p.badVerb(verb)
return true
}
p.wrappedErr = err
// If the arg is a Formatter, pass 'v' as the verb to it.
verb = 'v'
}
// Is it a Formatter?
if formatter, ok := p.arg.(Formatter); ok {
handled = true
defer p.catchPanic(p.arg, verb, "Format")
formatter.Format(p, verb)
return
}
// If we're doing Go syntax and the argument knows how to supply it, take care of it now.
if p.fmt.sharpV {
if stringer, ok := p.arg.(GoStringer); ok {
handled = true
defer p.catchPanic(p.arg, verb, "GoString")
// Print the result of GoString unadorned.
p.fmt.fmtS(stringer.GoString())
return
}
} else {
// If a string is acceptable according to the format, see if
// the value satisfies one of the string-valued interfaces.
// Println etc. set verb to %v, which is "stringable".
switch verb {
case 'v', 's', 'x', 'X', 'q':
// Is it an error or Stringer?
// The duplication in the bodies is necessary:
// setting handled and deferring catchPanic
// must happen before calling the method.
switch v := p.arg.(type) {
case error:
handled = true
defer p.catchPanic(p.arg, verb, "Error")
p.fmtString(v.Error(), verb)
return
case Stringer:
handled = true
defer p.catchPanic(p.arg, verb, "String")
p.fmtString(v.String(), verb)
return
}
}
}
return false
}
func (p *pp) printArg(arg any, verb rune) {
p.arg = arg
p.value = reflect.Value{}
if arg == nil {
switch verb {
case 'T', 'v':
p.fmt.padString(nilAngleString)
default:
p.badVerb(verb)
}
return
}
// Special processing considerations.
// %T (the value's type) and %p (its address) are special; we always do them first.
switch verb {
case 'T':
p.fmt.fmtS(reflect.TypeOf(arg).String())
return
case 'p':
p.fmtPointer(reflect.ValueOf(arg), 'p')
return
}
// Some types can be done without reflection.
switch f := arg.(type) {
case bool:
p.fmtBool(f, verb)
case float32:
p.fmtFloat(float64(f), 32, verb)
case float64:
p.fmtFloat(f, 64, verb)
case complex64:
p.fmtComplex(complex128(f), 64, verb)
case complex128:
p.fmtComplex(f, 128, verb)
case int:
p.fmtInteger(uint64(f), signed, verb)
case int8:
p.fmtInteger(uint64(f), signed, verb)
case int16:
p.fmtInteger(uint64(f), signed, verb)
case int32:
p.fmtInteger(uint64(f), signed, verb)
case int64:
p.fmtInteger(uint64(f), signed, verb)
case uint:
p.fmtInteger(uint64(f), unsigned, verb)
case uint8:
p.fmtInteger(uint64(f), unsigned, verb)
case uint16:
p.fmtInteger(uint64(f), unsigned, verb)
case uint32:
p.fmtInteger(uint64(f), unsigned, verb)
case uint64:
p.fmtInteger(f, unsigned, verb)
case uintptr:
p.fmtInteger(uint64(f), unsigned, verb)
case string:
p.fmtString(f, verb)
case []byte:
p.fmtBytes(f, verb, "[]byte")
case reflect.Value:
// Handle extractable values with special methods
// since printValue does not handle them at depth 0.
if f.IsValid() && f.CanInterface() {
p.arg = f.Interface()
if p.handleMethods(verb) {
return
}
}
p.printValue(f, verb, 0)
default:
// If the type is not simple, it might have methods.
if !p.handleMethods(verb) {
// Need to use reflection, since the type had no
// interface methods that could be used for formatting.
p.printValue(reflect.ValueOf(f), verb, 0)
}
}
}
// printValue is similar to printArg but starts with a reflect value, not an interface{} value.
// It does not handle 'p' and 'T' verbs because these should have been already handled by printArg.
func (p *pp) printValue(value reflect.Value, verb rune, depth int) {
// Handle values with special methods if not already handled by printArg (depth == 0).
if depth > 0 && value.IsValid() && value.CanInterface() {
p.arg = value.Interface()
if p.handleMethods(verb) {
return
}
}
p.arg = nil
p.value = value
switch f := value; value.Kind() {
case reflect.Invalid:
if depth == 0 {
p.buf.writeString(invReflectString)
} else {
switch verb {
case 'v':
p.buf.writeString(nilAngleString)
default:
p.badVerb(verb)
}
}
case reflect.Bool:
p.fmtBool(f.Bool(), verb)
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
p.fmtInteger(uint64(f.Int()), signed, verb)
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
p.fmtInteger(f.Uint(), unsigned, verb)
case reflect.Float32:
p.fmtFloat(f.Float(), 32, verb)
case reflect.Float64:
p.fmtFloat(f.Float(), 64, verb)
case reflect.Complex64:
p.fmtComplex(f.Complex(), 64, verb)
case reflect.Complex128:
p.fmtComplex(f.Complex(), 128, verb)
case reflect.String:
p.fmtString(f.String(), verb)
case reflect.Map:
if p.fmt.sharpV {
p.buf.writeString(f.Type().String())
if f.IsNil() {
p.buf.writeString(nilParenString)
return
}
p.buf.writeByte('{')
} else {
p.buf.writeString(mapString)
}
sorted := fmtsort.Sort(f)
for i, key := range sorted.Key {
if i > 0 {
if p.fmt.sharpV {
p.buf.writeString(commaSpaceString)
} else {
p.buf.writeByte(' ')
}
}
p.printValue(key, verb, depth+1)
p.buf.writeByte(':')
p.printValue(sorted.Value[i], verb, depth+1)
}
if p.fmt.sharpV {
p.buf.writeByte('}')
} else {
p.buf.writeByte(']')
}
case reflect.Struct:
if p.fmt.sharpV {
p.buf.writeString(f.Type().String())
}
p.buf.writeByte('{')
for i := 0; i < f.NumField(); i++ {
if i > 0 {
if p.fmt.sharpV {
p.buf.writeString(commaSpaceString)
} else {
p.buf.writeByte(' ')
}
}
if p.fmt.plusV || p.fmt.sharpV {
if name := f.Type().Field(i).Name; name != "" {
p.buf.writeString(name)
p.buf.writeByte(':')
}
}
p.printValue(getField(f, i), verb, depth+1)
}
p.buf.writeByte('}')
case reflect.Interface:
value := f.Elem()
if !value.IsValid() {
if p.fmt.sharpV {
p.buf.writeString(f.Type().String())
p.buf.writeString(nilParenString)
} else {
p.buf.writeString(nilAngleString)
}
} else {
p.printValue(value, verb, depth+1)
}
case reflect.Array, reflect.Slice:
switch verb {
case 's', 'q', 'x', 'X':
// Handle byte and uint8 slices and arrays special for the above verbs.
t := f.Type()
if t.Elem().Kind() == reflect.Uint8 {
var bytes []byte
if f.Kind() == reflect.Slice {
bytes = f.Bytes()
} else if f.CanAddr() {
bytes = f.Slice(0, f.Len()).Bytes()
} else {
// We have an array, but we cannot Slice() a non-addressable array,
// so we build a slice by hand. This is a rare case but it would be nice
// if reflection could help a little more.
bytes = make([]byte, f.Len())
for i := range bytes {
bytes[i] = byte(f.Index(i).Uint())
}
}
p.fmtBytes(bytes, verb, t.String())
return
}
}
if p.fmt.sharpV {
p.buf.writeString(f.Type().String())
if f.Kind() == reflect.Slice && f.IsNil() {
p.buf.writeString(nilParenString)
return
}
p.buf.writeByte('{')
for i := 0; i < f.Len(); i++ {
if i > 0 {
p.buf.writeString(commaSpaceString)
}
p.printValue(f.Index(i), verb, depth+1)
}
p.buf.writeByte('}')
} else {
p.buf.writeByte('[')
for i := 0; i < f.Len(); i++ {
if i > 0 {
p.buf.writeByte(' ')
}
p.printValue(f.Index(i), verb, depth+1)
}
p.buf.writeByte(']')
}
case reflect.Pointer:
// pointer to array or slice or struct? ok at top level
// but not embedded (avoid loops)
if depth == 0 && f.Pointer() != 0 {
switch a := f.Elem(); a.Kind() {
case reflect.Array, reflect.Slice, reflect.Struct, reflect.Map:
p.buf.writeByte('&')
p.printValue(a, verb, depth+1)
return
}
}
fallthrough
case reflect.Chan, reflect.Func, reflect.UnsafePointer:
p.fmtPointer(f, verb)
default:
p.unknownType(f)
}
}
// intFromArg gets the argNumth element of a. On return, isInt reports whether the argument has integer type.
func intFromArg(a []any, argNum int) (num int, isInt bool, newArgNum int) {
newArgNum = argNum
if argNum < len(a) {
num, isInt = a[argNum].(int) // Almost always OK.
if !isInt {
// Work harder.
switch v := reflect.ValueOf(a[argNum]); v.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
n := v.Int()
if int64(int(n)) == n {
num = int(n)
isInt = true
}
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
n := v.Uint()
if int64(n) >= 0 && uint64(int(n)) == n {
num = int(n)
isInt = true
}
default:
// Already 0, false.
}
}
newArgNum = argNum + 1
if tooLarge(num) {
num = 0
isInt = false
}
}
return
}
// parseArgNumber returns the value of the bracketed number, minus 1
// (explicit argument numbers are one-indexed but we want zero-indexed).
// The opening bracket is known to be present at format[0].
// The returned values are the index, the number of bytes to consume
// up to the closing paren, if present, and whether the number parsed
// ok. The bytes to consume will be 1 if no closing paren is present.
func parseArgNumber(format string) (index int, wid int, ok bool) {
// There must be at least 3 bytes: [n].
if len(format) < 3 {
return 0, 1, false
}
// Find closing bracket.
for i := 1; i < len(format); i++ {
if format[i] == ']' {
width, ok, newi := parsenum(format, 1, i)
if !ok || newi != i {
return 0, i + 1, false
}
return width - 1, i + 1, true // arg numbers are one-indexed and skip paren.
}
}
return 0, 1, false
}
// argNumber returns the next argument to evaluate, which is either the value of the passed-in
// argNum or the value of the bracketed integer that begins format[i:]. It also returns
// the new value of i, that is, the index of the next byte of the format to process.
func (p *pp) argNumber(argNum int, format string, i int, numArgs int) (newArgNum, newi int, found bool) {
if len(format) <= i || format[i] != '[' {
return argNum, i, false
}
p.reordered = true
index, wid, ok := parseArgNumber(format[i:])
if ok && 0 <= index && index < numArgs {
return index, i + wid, true
}
p.goodArgNum = false
return argNum, i + wid, ok
}
func (p *pp) badArgNum(verb rune) {
p.buf.writeString(percentBangString)
p.buf.writeRune(verb)
p.buf.writeString(badIndexString)
}
func (p *pp) missingArg(verb rune) {
p.buf.writeString(percentBangString)
p.buf.writeRune(verb)
p.buf.writeString(missingString)
}
func (p *pp) doPrintf(format string, a []any) {
end := len(format)
argNum := 0 // we process one argument per non-trivial format
afterIndex := false // previous item in format was an index like [3].
p.reordered = false
formatLoop:
for i := 0; i < end; {
p.goodArgNum = true
lasti := i
for i < end && format[i] != '%' {
i++
}
if i > lasti {
p.buf.writeString(format[lasti:i])
}
if i >= end {
// done processing format string
break
}
// Process one verb
i++
// Do we have flags?
p.fmt.clearflags()
simpleFormat:
for ; i < end; i++ {
c := format[i]
switch c {
case '#':
p.fmt.sharp = true
case '0':
p.fmt.zero = !p.fmt.minus // Only allow zero padding to the left.
case '+':
p.fmt.plus = true
case '-':
p.fmt.minus = true
p.fmt.zero = false // Do not pad with zeros to the right.
case ' ':
p.fmt.space = true
default:
// Fast path for common case of ascii lower case simple verbs
// without precision or width or argument indices.
if 'a' <= c && c <= 'z' && argNum < len(a) {
if c == 'v' {
// Go syntax
p.fmt.sharpV = p.fmt.sharp
p.fmt.sharp = false
// Struct-field syntax
p.fmt.plusV = p.fmt.plus
p.fmt.plus = false
}
p.printArg(a[argNum], rune(c))
argNum++
i++
continue formatLoop
}
// Format is more complex than simple flags and a verb or is malformed.
break simpleFormat
}
}
// Do we have an explicit argument index?
argNum, i, afterIndex = p.argNumber(argNum, format, i, len(a))
// Do we have width?
if i < end && format[i] == '*' {
i++
p.fmt.wid, p.fmt.widPresent, argNum = intFromArg(a, argNum)
if !p.fmt.widPresent {
p.buf.writeString(badWidthString)
}
// We have a negative width, so take its value and ensure
// that the minus flag is set
if p.fmt.wid < 0 {
p.fmt.wid = -p.fmt.wid
p.fmt.minus = true
p.fmt.zero = false // Do not pad with zeros to the right.
}
afterIndex = false
} else {
p.fmt.wid, p.fmt.widPresent, i = parsenum(format, i, end)
if afterIndex && p.fmt.widPresent { // "%[3]2d"
p.goodArgNum = false
}
}
// Do we have precision?
if i+1 < end && format[i] == '.' {
i++
if afterIndex { // "%[3].2d"
p.goodArgNum = false
}
argNum, i, afterIndex = p.argNumber(argNum, format, i, len(a))
if i < end && format[i] == '*' {
i++
p.fmt.prec, p.fmt.precPresent, argNum = intFromArg(a, argNum)
// Negative precision arguments don't make sense
if p.fmt.prec < 0 {
p.fmt.prec = 0
p.fmt.precPresent = false
}
if !p.fmt.precPresent {
p.buf.writeString(badPrecString)
}
afterIndex = false
} else {
p.fmt.prec, p.fmt.precPresent, i = parsenum(format, i, end)
if !p.fmt.precPresent {
p.fmt.prec = 0
p.fmt.precPresent = true
}
}
}
if !afterIndex {
argNum, i, afterIndex = p.argNumber(argNum, format, i, len(a))
}
if i >= end {
p.buf.writeString(noVerbString)
break
}
verb, size := rune(format[i]), 1
if verb >= utf8.RuneSelf {
verb, size = utf8.DecodeRuneInString(format[i:])
}
i += size
switch {
case verb == '%': // Percent does not absorb operands and ignores f.wid and f.prec.
p.buf.writeByte('%')
case !p.goodArgNum:
p.badArgNum(verb)
case argNum >= len(a): // No argument left over to print for the current verb.
p.missingArg(verb)
case verb == 'v':
// Go syntax
p.fmt.sharpV = p.fmt.sharp
p.fmt.sharp = false
// Struct-field syntax
p.fmt.plusV = p.fmt.plus
p.fmt.plus = false
fallthrough
default:
p.printArg(a[argNum], verb)
argNum++
}
}
// Check for extra arguments unless the call accessed the arguments
// out of order, in which case it's too expensive to detect if they've all
// been used and arguably OK if they're not.
if !p.reordered && argNum < len(a) {
p.fmt.clearflags()
p.buf.writeString(extraString)
for i, arg := range a[argNum:] {
if i > 0 {
p.buf.writeString(commaSpaceString)
}
if arg == nil {
p.buf.writeString(nilAngleString)
} else {
p.buf.writeString(reflect.TypeOf(arg).String())
p.buf.writeByte('=')
p.printArg(arg, 'v')
}
}
p.buf.writeByte(')')
}
}
func (p *pp) doPrint(a []any) {
prevString := false
for argNum, arg := range a {
isString := arg != nil && reflect.TypeOf(arg).Kind() == reflect.String
// Add a space between two non-string arguments.
if argNum > 0 && !isString && !prevString {
p.buf.writeByte(' ')
}
p.printArg(arg, 'v')
prevString = isString
}
}
// doPrintln is like doPrint but always adds a space between arguments
// and a newline after the last argument.
func (p *pp) doPrintln(a []any) {
for argNum, arg := range a {
if argNum > 0 {
p.buf.writeByte(' ')
}
p.printArg(arg, 'v')
}
p.buf.writeByte('\n')
}
Raw
scan.go
// 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"
"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 ...any) (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 ...any) (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 ...any) (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 ...any) (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 ...any) (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 ...any) (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 ...any) (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 ...any) (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 ...any) (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() any { 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 any) {
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.Pointer {
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 []any) (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 []any) (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
}
@sago35
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sago35 commented May 17, 2022

This file is a modified version of the Go1.18.1 fmt package.
You can place them anywhere you like and import them.

It can be used with semihosting.
https://github.com/tinygo-org/drivers/blob/release/examples/semihosting/semihosting.go

package machine

import (
        "machine/fmt"
	"tinygo.org/x/drivers/semihosting"
)

func foo() {
        semihosting.Stdout.Write([]byte(fmt.Sprintf("hello %s\n", "tinygo")))
}

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