// 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 (
"errors"
"io"
"os"
"reflect"
"sync"
"unicode/utf8"
)
// Some constants in the form of bytes, to avoid string overhead.
// Needlessly fastidious, I suppose.
var (
commaSpaceBytes = []byte(", ")
nilAngleBytes = []byte("<nil>")
nilParenBytes = []byte("(nil)")
nilBytes = []byte("nil")
mapBytes = []byte("map[")
percentBangBytes = []byte("%!")
missingBytes = []byte("(MISSING)")
badIndexBytes = []byte("(BADINDEX)")
panicBytes = []byte("(PANIC=")
extraBytes = []byte("%!(EXTRA ")
irparenBytes = []byte("i)")
bytesBytes = []byte("[]byte{")
badWidthBytes = []byte("%!(BADWIDTH)")
badPrecBytes = []byte("%!(BADPREC)")
noVerbBytes = []byte("%!(NOVERB)")
)
// 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) (ret 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 the interface implemented by values with a custom formatter.
// The implementation of Format may call Sprint(f) or Fprint(f) etc.
// to generate its output.
type Formatter interface {
Format(f State, c 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) (n int, err error) {
*b = append(*b, p...)
return len(p), nil
}
func (b *buffer) WriteString(s string) (n int, err error) {
*b = append(*b, s...)
return len(s), nil
}
func (b *buffer) WriteByte(c byte) error {
*b = append(*b, c)
return nil
}
func (bp *buffer) WriteRune(r rune) error {
if r < utf8.RuneSelf {
*bp = append(*bp, byte(r))
return nil
}
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]
return nil
}
type pp struct {
n int
panicking bool
erroring bool // printing an error condition
buf buffer
// arg holds the current item, as an interface{}.
arg interface{}
// value holds the current item, as a reflect.Value, and will be
// the zero Value if the item has not been reflected.
value reflect.Value
// reordered records whether the format string used argument reordering.
reordered bool
// goodArgNum records whether the most recent reordering directive was valid.
goodArgNum bool
runeBuf [utf8.UTFMax]byte
fmt fmt
}
var ppFree = sync.Pool{
New: func() interface{} { 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.fmt.init(&p.buf)
return p
}
// free saves used pp structs in ppFree; avoids an allocation per invocation.
func (p *pp) free() {
// Don't hold on to pp structs with large buffers.
if cap(p.buf) > 1024 {
return
}
p.buf = p.buf[:0]
p.arg = nil
p.value = reflect.Value{}
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
case '#':
return p.fmt.sharp
case ' ':
return p.fmt.space
case '0':
return p.fmt.zero
}
return false
}
func (p *pp) add(c rune) {
p.buf.WriteRune(c)
}
// 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) {
return p.buf.Write(b)
}
// 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 ...interface{}) (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 ...interface{}) (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 ...interface{}) string {
p := newPrinter()
p.doPrintf(format, a)
s := string(p.buf)
p.free()
return s
}
// Errorf formats according to a format specifier and returns the string
// as a value that satisfies error.
func Errorf(format string, a ...interface{}) error {
return errors.New(Sprintf(format, a...))
}
// 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 ...interface{}) (n int, err error) {
p := newPrinter()
p.doPrint(a, false, false)
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 ...interface{}) (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 ...interface{}) string {
p := newPrinter()
p.doPrint(a, false, false)
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 ...interface{}) (n int, err error) {
p := newPrinter()
p.doPrint(a, true, true)
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 ...interface{}) (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 ...interface{}) string {
p := newPrinter()
p.doPrint(a, true, true)
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.Write(nilAngleBytes)
return
}
p.buf.WriteByte('?')
p.buf.WriteString(v.Type().String())
p.buf.WriteByte('?')
}
func (p *pp) badVerb(verb rune) {
p.erroring = true
p.add('%')
p.add('!')
p.add(verb)
p.add('(')
switch {
case p.arg != nil:
p.buf.WriteString(reflect.TypeOf(p.arg).String())
p.add('=')
p.printArg(p.arg, 'v', 0)
case p.value.IsValid():
p.buf.WriteString(p.value.Type().String())
p.add('=')
p.printValue(p.value, 'v', 0)
default:
p.buf.Write(nilAngleBytes)
}
p.add(')')
p.erroring = false
}
func (p *pp) fmtBool(v bool, verb rune) {
switch verb {
case 't', 'v':
p.fmt.fmt_boolean(v)
default:
p.badVerb(verb)
}
}
// fmtC formats a rune for the 'c' format.
func (p *pp) fmtC(c int64) {
r := rune(c) // Check for overflow.
if int64(r) != c {
r = utf8.RuneError
}
w := utf8.EncodeRune(p.runeBuf[0:utf8.UTFMax], r)
p.fmt.pad(p.runeBuf[0:w])
}
func (p *pp) fmtInt64(v int64, verb rune) {
switch verb {
case 'b':
p.fmt.integer(v, 2, signed, ldigits)
case 'c':
p.fmtC(v)
case 'd', 'v':
p.fmt.integer(v, 10, signed, ldigits)
case 'o':
p.fmt.integer(v, 8, signed, ldigits)
case 'q':
if 0 <= v && v <= utf8.MaxRune {
p.fmt.fmt_qc(v)
} else {
p.badVerb(verb)
}
case 'x':
p.fmt.integer(v, 16, signed, ldigits)
case 'U':
p.fmtUnicode(v)
case 'X':
p.fmt.integer(v, 16, signed, udigits)
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.integer(int64(v), 16, unsigned, ldigits)
p.fmt.sharp = sharp
}
// fmtUnicode formats a uint64 in U+1234 form by
// temporarily turning on the unicode flag and tweaking the precision.
func (p *pp) fmtUnicode(v int64) {
precPresent := p.fmt.precPresent
sharp := p.fmt.sharp
p.fmt.sharp = false
prec := p.fmt.prec
if !precPresent {
// If prec is already set, leave it alone; otherwise 4 is minimum.
p.fmt.prec = 4
p.fmt.precPresent = true
}
p.fmt.unicode = true // turn on U+
p.fmt.uniQuote = sharp
p.fmt.integer(int64(v), 16, unsigned, udigits)
p.fmt.unicode = false
p.fmt.uniQuote = false
p.fmt.prec = prec
p.fmt.precPresent = precPresent
p.fmt.sharp = sharp
}
func (p *pp) fmtUint64(v uint64, verb rune) {
switch verb {
case 'b':
p.fmt.integer(int64(v), 2, unsigned, ldigits)
case 'c':
p.fmtC(int64(v))
case 'd':
p.fmt.integer(int64(v), 10, unsigned, ldigits)
case 'v':
if p.fmt.sharpV {
p.fmt0x64(v, true)
} else {
p.fmt.integer(int64(v), 10, unsigned, ldigits)
}
case 'o':
p.fmt.integer(int64(v), 8, unsigned, ldigits)
case 'q':
if 0 <= v && v <= utf8.MaxRune {
p.fmt.fmt_qc(int64(v))
} else {
p.badVerb(verb)
}
case 'x':
p.fmt.integer(int64(v), 16, unsigned, ldigits)
case 'X':
p.fmt.integer(int64(v), 16, unsigned, udigits)
case 'U':
p.fmtUnicode(int64(v))
default:
p.badVerb(verb)
}
}
func (p *pp) fmtFloat32(v float32, verb rune) {
switch verb {
case 'b':
p.fmt.fmt_fb32(v)
case 'e':
p.fmt.fmt_e32(v)
case 'E':
p.fmt.fmt_E32(v)
case 'f', 'F':
p.fmt.fmt_f32(v)
case 'g', 'v':
p.fmt.fmt_g32(v)
case 'G':
p.fmt.fmt_G32(v)
default:
p.badVerb(verb)
}
}
func (p *pp) fmtFloat64(v float64, verb rune) {
switch verb {
case 'b':
p.fmt.fmt_fb64(v)
case 'e':
p.fmt.fmt_e64(v)
case 'E':
p.fmt.fmt_E64(v)
case 'f', 'F':
p.fmt.fmt_f64(v)
case 'g', 'v':
p.fmt.fmt_g64(v)
case 'G':
p.fmt.fmt_G64(v)
default:
p.badVerb(verb)
}
}
func (p *pp) fmtComplex64(v complex64, verb rune) {
switch verb {
case 'b', 'e', 'E', 'f', 'F', 'g', 'G':
p.fmt.fmt_c64(v, verb)
case 'v':
p.fmt.fmt_c64(v, 'g')
default:
p.badVerb(verb)
}
}
func (p *pp) fmtComplex128(v complex128, verb rune) {
switch verb {
case 'b', 'e', 'E', 'f', 'F', 'g', 'G':
p.fmt.fmt_c128(v, verb)
case 'v':
p.fmt.fmt_c128(v, 'g')
default:
p.badVerb(verb)
}
}
func (p *pp) fmtString(v string, verb rune) {
switch verb {
case 'v':
if p.fmt.sharpV {
p.fmt.fmt_q(v)
} else {
p.fmt.fmt_s(v)
}
case 's':
p.fmt.fmt_s(v)
case 'x':
p.fmt.fmt_sx(v, ldigits)
case 'X':
p.fmt.fmt_sx(v, udigits)
case 'q':
p.fmt.fmt_q(v)
default:
p.badVerb(verb)
}
}
func (p *pp) fmtBytes(v []byte, verb rune, typ reflect.Type, depth int) {
if verb == 'v' || verb == 'd' {
if p.fmt.sharpV {
if v == nil {
if typ == nil {
p.buf.WriteString("[]byte(nil)")
} else {
p.buf.WriteString(typ.String())
p.buf.Write(nilParenBytes)
}
return
}
if typ == nil {
p.buf.Write(bytesBytes)
} else {
p.buf.WriteString(typ.String())
p.buf.WriteByte('{')
}
} else {
p.buf.WriteByte('[')
}
for i, c := range v {
if i > 0 {
if p.fmt.sharpV {
p.buf.Write(commaSpaceBytes)
} else {
p.buf.WriteByte(' ')
}
}
p.printArg(c, 'v', depth+1)
}
if p.fmt.sharpV {
p.buf.WriteByte('}')
} else {
p.buf.WriteByte(']')
}
return
}
switch verb {
case 's':
p.fmt.fmt_s(string(v))
case 'x':
p.fmt.fmt_bx(v, ldigits)
case 'X':
p.fmt.fmt_bx(v, udigits)
case 'q':
p.fmt.fmt_q(string(v))
default:
p.badVerb(verb)
}
}
func (p *pp) fmtPointer(value reflect.Value, verb rune) {
use0x64 := true
switch verb {
case 'p', 'v':
// ok
case 'b', 'd', 'o', 'x', 'X':
use0x64 = false
// ok
default:
p.badVerb(verb)
return
}
var u uintptr
switch value.Kind() {
case reflect.Chan, reflect.Func, reflect.Map, reflect.Ptr, reflect.Slice, reflect.UnsafePointer:
u = value.Pointer()
default:
p.badVerb(verb)
return
}
if p.fmt.sharpV {
p.add('(')
p.buf.WriteString(value.Type().String())
p.add(')')
p.add('(')
if u == 0 {
p.buf.Write(nilBytes)
} else {
p.fmt0x64(uint64(u), true)
}
p.add(')')
} else if verb == 'v' && u == 0 {
p.buf.Write(nilAngleBytes)
} else {
if use0x64 {
p.fmt0x64(uint64(u), !p.fmt.sharp)
} else {
p.fmtUint64(uint64(u), verb)
}
}
}
var (
intBits = reflect.TypeOf(0).Bits()
uintptrBits = reflect.TypeOf(uintptr(0)).Bits()
)
func (p *pp) catchPanic(arg interface{}, verb rune) {
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.Ptr && v.IsNil() {
p.buf.Write(nilAngleBytes)
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)
}
p.fmt.clearflags() // We are done, and for this output we want default behavior.
p.buf.Write(percentBangBytes)
p.add(verb)
p.buf.Write(panicBytes)
p.panicking = true
p.printArg(err, 'v', 0)
p.panicking = false
p.buf.WriteByte(')')
}
}
// clearSpecialFlags pushes %#v back into the regular flags and returns their old state.
func (p *pp) clearSpecialFlags() (plusV, sharpV bool) {
plusV = p.fmt.plusV
if plusV {
p.fmt.plus = true
p.fmt.plusV = false
}
sharpV = p.fmt.sharpV
if sharpV {
p.fmt.sharp = true
p.fmt.sharpV = false
}
return
}
// restoreSpecialFlags, whose argument should be a call to clearSpecialFlags,
// restores the setting of the plusV and sharpV flags.
func (p *pp) restoreSpecialFlags(plusV, sharpV bool) {
if plusV {
p.fmt.plus = false
p.fmt.plusV = true
}
if sharpV {
p.fmt.sharp = false
p.fmt.sharpV = true
}
}
func (p *pp) handleMethods(verb rune, depth int) (handled bool) {
if p.erroring {
return
}
// Is it a Formatter?
if formatter, ok := p.arg.(Formatter); ok {
handled = true
defer p.restoreSpecialFlags(p.clearSpecialFlags())
defer p.catchPanic(p.arg, verb)
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)
// Print the result of GoString unadorned.
p.fmt.fmt_s(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)
p.printArg(v.Error(), verb, depth)
return
case Stringer:
handled = true
defer p.catchPanic(p.arg, verb)
p.printArg(v.String(), verb, depth)
return
}
}
}
return false
}
func (p *pp) printArg(arg interface{}, verb rune, depth int) (wasString bool) {
p.arg = arg
p.value = reflect.Value{}
if arg == nil {
if verb == 'T' || verb == 'v' {
p.fmt.pad(nilAngleBytes)
} else {
p.badVerb(verb)
}
return false
}
// Special processing considerations.
// %T (the value's type) and %p (its address) are special; we always do them first.
switch verb {
case 'T':
p.printArg(reflect.TypeOf(arg).String(), 's', 0)
return false
case 'p':
p.fmtPointer(reflect.ValueOf(arg), verb)
return false
}
// Some types can be done without reflection.
switch f := arg.(type) {
case bool:
p.fmtBool(f, verb)
case float32:
p.fmtFloat32(f, verb)
case float64:
p.fmtFloat64(f, verb)
case complex64:
p.fmtComplex64(f, verb)
case complex128:
p.fmtComplex128(f, verb)
case int:
p.fmtInt64(int64(f), verb)
case int8:
p.fmtInt64(int64(f), verb)
case int16:
p.fmtInt64(int64(f), verb)
case int32:
p.fmtInt64(int64(f), verb)
case int64:
p.fmtInt64(f, verb)
case uint:
p.fmtUint64(uint64(f), verb)
case uint8:
p.fmtUint64(uint64(f), verb)
case uint16:
p.fmtUint64(uint64(f), verb)
case uint32:
p.fmtUint64(uint64(f), verb)
case uint64:
p.fmtUint64(f, verb)
case uintptr:
p.fmtUint64(uint64(f), verb)
case string:
p.fmtString(f, verb)
wasString = verb == 's' || verb == 'v'
case []byte:
p.fmtBytes(f, verb, nil, depth)
wasString = verb == 's'
case reflect.Value:
return p.printReflectValue(f, verb, depth)
default:
// If the type is not simple, it might have methods.
if handled := p.handleMethods(verb, depth); handled {
return false
}
// Need to use reflection
return p.printReflectValue(reflect.ValueOf(arg), verb, depth)
}
p.arg = nil
return
}
// printValue is like printArg but starts with a reflect value, not an interface{} value.
func (p *pp) printValue(value reflect.Value, verb rune, depth int) (wasString bool) {
if !value.IsValid() {
if verb == 'T' || verb == 'v' {
p.buf.Write(nilAngleBytes)
} else {
p.badVerb(verb)
}
return false
}
// Special processing considerations.
// %T (the value's type) and %p (its address) are special; we always do them first.
switch verb {
case 'T':
p.printArg(value.Type().String(), 's', 0)
return false
case 'p':
p.fmtPointer(value, verb)
return false
}
// Handle values with special methods.
// Call always, even when arg == nil, because handleMethods clears p.fmt.plus for us.
p.arg = nil // Make sure it's cleared, for safety.
if value.CanInterface() {
p.arg = value.Interface()
}
if handled := p.handleMethods(verb, depth); handled {
return false
}
return p.printReflectValue(value, verb, depth)
}
var byteType = reflect.TypeOf(byte(0))
// printReflectValue is the fallback for both printArg and printValue.
// It uses reflect to print the value.
func (p *pp) printReflectValue(value reflect.Value, verb rune, depth int) (wasString bool) {
oldValue := p.value
p.value = value
BigSwitch:
switch f := value; f.Kind() {
case reflect.Invalid:
p.buf.WriteString("<invalid reflect.Value>")
case reflect.Bool:
p.fmtBool(f.Bool(), verb)
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
p.fmtInt64(f.Int(), verb)
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
p.fmtUint64(f.Uint(), verb)
case reflect.Float32, reflect.Float64:
if f.Type().Size() == 4 {
p.fmtFloat32(float32(f.Float()), verb)
} else {
p.fmtFloat64(f.Float(), verb)
}
case reflect.Complex64, reflect.Complex128:
if f.Type().Size() == 8 {
p.fmtComplex64(complex64(f.Complex()), verb)
} else {
p.fmtComplex128(f.Complex(), 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("(nil)")
break
}
p.buf.WriteByte('{')
} else {
p.buf.Write(mapBytes)
}
keys := f.MapKeys()
for i, key := range keys {
if i > 0 {
if p.fmt.sharpV {
p.buf.Write(commaSpaceBytes)
} else {
p.buf.WriteByte(' ')
}
}
p.printValue(key, verb, depth+1)
p.buf.WriteByte(':')
p.printValue(f.MapIndex(key), verb, depth+1)
}
if p.fmt.sharpV {
p.buf.WriteByte('}')
} else {
p.buf.WriteByte(']')
}
case reflect.Struct:
if p.fmt.sharpV {
p.buf.WriteString(value.Type().String())
}
p.add('{')
v := f
t := v.Type()
for i := 0; i < v.NumField(); i++ {
if i > 0 {
if p.fmt.sharpV {
p.buf.Write(commaSpaceBytes)
} else {
p.buf.WriteByte(' ')
}
}
if p.fmt.plusV || p.fmt.sharpV {
if f := t.Field(i); f.Name != "" {
p.buf.WriteString(f.Name)
p.buf.WriteByte(':')
}
}
p.printValue(getField(v, 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.Write(nilParenBytes)
} else {
p.buf.Write(nilAngleBytes)
}
} else {
wasString = p.printValue(value, verb, depth+1)
}
case reflect.Array, reflect.Slice:
// Byte slices are special:
// - Handle []byte (== []uint8) with fmtBytes.
// - Handle []T, where T is a named byte type, with fmtBytes only
// for the s, q, an x verbs. For other verbs, T might be a
// Stringer, so we use printValue to print each element.
if typ := f.Type(); typ.Elem().Kind() == reflect.Uint8 && (typ.Elem() == byteType || verb == 's' || verb == 'q' || verb == 'x') {
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, typ, depth)
wasString = verb == 's'
break
}
if p.fmt.sharpV {
p.buf.WriteString(value.Type().String())
if f.Kind() == reflect.Slice && f.IsNil() {
p.buf.WriteString("(nil)")
break
}
p.buf.WriteByte('{')
} else {
p.buf.WriteByte('[')
}
for i := 0; i < f.Len(); i++ {
if i > 0 {
if p.fmt.sharpV {
p.buf.Write(commaSpaceBytes)
} else {
p.buf.WriteByte(' ')
}
}
p.printValue(f.Index(i), verb, depth+1)
}
if p.fmt.sharpV {
p.buf.WriteByte('}')
} else {
p.buf.WriteByte(']')
}
case reflect.Ptr:
v := f.Pointer()
// pointer to array or slice or struct? ok at top level
// but not embedded (avoid loops)
if v != 0 && depth == 0 {
switch a := f.Elem(); a.Kind() {
case reflect.Array, reflect.Slice:
p.buf.WriteByte('&')
p.printValue(a, verb, depth+1)
break BigSwitch
case reflect.Struct:
p.buf.WriteByte('&')
p.printValue(a, verb, depth+1)
break BigSwitch
case reflect.Map:
p.buf.WriteByte('&')
p.printValue(a, verb, depth+1)
break BigSwitch
}
}
fallthrough
case reflect.Chan, reflect.Func, reflect.UnsafePointer:
p.fmtPointer(value, verb)
default:
p.unknownType(f)
}
p.value = oldValue
return wasString
}
// intFromArg gets the argNumth element of a. On return, isInt reports whether the argument has type int.
func intFromArg(a []interface{}, argNum int) (num int, isInt bool, newArgNum int) {
newArgNum = argNum
if argNum < len(a) {
num, isInt = a[argNum].(int)
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) doPrintf(format string, a []interface{}) {
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
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()
F:
for ; i < end; i++ {
switch format[i] {
case '#':
p.fmt.sharp = true
case '0':
p.fmt.zero = true
case '+':
p.fmt.plus = true
case '-':
p.fmt.minus = true
case ' ':
p.fmt.space = true
default:
break F
}
}
// 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.Write(badWidthBytes)
}
// 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
}
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.Write(badPrecBytes)
}
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.Write(noVerbBytes)
continue
}
c, w := utf8.DecodeRuneInString(format[i:])
i += w
// percent is special - absorbs no operand
if c == '%' {
p.buf.WriteByte('%') // We ignore width and prec.
continue
}
if !p.goodArgNum {
p.buf.Write(percentBangBytes)
p.add(c)
p.buf.Write(badIndexBytes)
continue
} else if argNum >= len(a) { // out of operands
p.buf.Write(percentBangBytes)
p.add(c)
p.buf.Write(missingBytes)
continue
}
arg := a[argNum]
argNum++
if c == 'v' {
if p.fmt.sharp {
// Go syntax. Set the flag in the fmt and clear the sharp flag.
p.fmt.sharp = false
p.fmt.sharpV = true
}
if p.fmt.plus {
// Struct-field syntax. Set the flag in the fmt and clear the plus flag.
p.fmt.plus = false
p.fmt.plusV = true
}
}
p.printArg(arg, c, 0)
}
// 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.buf.Write(extraBytes)
for ; argNum < len(a); argNum++ {
arg := a[argNum]
if arg != nil {
p.buf.WriteString(reflect.TypeOf(arg).String())
p.buf.WriteByte('=')
}
p.printArg(arg, 'v', 0)
if argNum+1 < len(a) {
p.buf.Write(commaSpaceBytes)
}
}
p.buf.WriteByte(')')
}
}
func (p *pp) doPrint(a []interface{}, addspace, addnewline bool) {
prevString := false
for argNum := 0; argNum < len(a); argNum++ {
p.fmt.clearflags()
// always add spaces if we're doing Println
arg := a[argNum]
if argNum > 0 {
isString := arg != nil && reflect.TypeOf(arg).Kind() == reflect.String
if addspace || !isString && !prevString {
p.buf.WriteByte(' ')
}
}
prevString = p.printArg(arg, 'v', 0)
}
if addnewline {
p.buf.WriteByte('\n')
}
}