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// 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[")
missingBytes = []byte("(MISSING)")
panicBytes = []byte("(PANIC=")
extraBytes = []byte("%!(EXTRA ")
irparenBytes = []byte("i)")
bytesBytes = []byte("[]byte{")
widthBytes = []byte("%!(BADWIDTH)")
precBytes = []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 returns 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 Sprintf or Fprintf(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 a %s or %v format 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
// field holds the current item, as an interface{}.
field 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
runeBuf [utf8.UTFMax]byte
fmt fmt
}
// A cache holds a set of reusable objects.
// The slice is a stack (LIFO).
// If more are needed, the cache creates them by calling new.
type cache struct {
mu sync.Mutex
saved []interface{}
new func() interface{}
}
func (c *cache) put(x interface{}) {
c.mu.Lock()
if len(c.saved) < cap(c.saved) {
c.saved = append(c.saved, x)
}
c.mu.Unlock()
}
func (c *cache) get() interface{} {
c.mu.Lock()
n := len(c.saved)
if n == 0 {
c.mu.Unlock()
return c.new()
}
x := c.saved[n-1]
c.saved = c.saved[0 : n-1]
c.mu.Unlock()
return x
}
func newCache(f func() interface{}) *cache {
return &cache{saved: make([]interface{}, 0, 100), new: f}
}
var ppFree = newCache(func() interface{} { return new(pp) })
// Allocate a new pp struct or grab a cached one.
func newPrinter() *pp {
p := ppFree.get().(*pp)
p.panicking = false
p.erroring = false
p.fmt.init(&p.buf)
return p
}
// Save 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.field = 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)
n64, err := w.Write(p.buf)
p.free()
return int(n64), err
}
// 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)
n64, err := w.Write(p.buf)
p.free()
return int(n64), err
}
// 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)
n64, err := w.Write(p.buf)
p.free()
return int(n64), err
}
// 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
}
// Get the i'th arg of the struct value.
// If the arg 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
}
// Convert ASCII to integer. n is 0 (and got 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++ {
num = num*10 + int(s[newi]-'0')
isnum = true
}
return
}
func (p *pp) unknownType(v interface{}) {
if v == nil {
p.buf.Write(nilAngleBytes)
return
}
p.buf.WriteByte('?')
p.buf.WriteString(reflect.TypeOf(v).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.field != nil:
p.buf.WriteString(reflect.TypeOf(p.field).String())
p.add('=')
p.printField(p.field, 'v', false, false, 0)
case p.value.IsValid():
p.buf.WriteString(p.value.Type().String())
p.add('=')
p.printValue(p.value, 'v', false, false, 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, goSyntax bool) {
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 goSyntax {
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':
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':
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 '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 '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, goSyntax bool) {
switch verb {
case 'v':
if goSyntax {
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, goSyntax bool, depth int) {
if verb == 'v' || verb == 'd' {
if goSyntax {
p.buf.Write(bytesBytes)
} else {
p.buf.WriteByte('[')
}
for i, c := range v {
if i > 0 {
if goSyntax {
p.buf.Write(commaSpaceBytes)
} else {
p.buf.WriteByte(' ')
}
}
p.printField(c, 'v', p.fmt.plus, goSyntax, depth+1)
}
if goSyntax {
p.buf.WriteByte('}')
} else {
p.buf.WriteByte(']')
}
return
}
s := string(v)
switch verb {
case 's':
p.fmt.fmt_s(s)
case 'x':
p.fmt.fmt_sx(s, ldigits)
case 'X':
p.fmt.fmt_sx(s, udigits)
case 'q':
p.fmt.fmt_q(s)
default:
p.badVerb(verb)
}
}
func (p *pp) fmtPointer(value reflect.Value, verb rune, goSyntax bool) {
switch verb {
case 'p', 'v', 'b', 'd', 'o', 'x', 'X':
// 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 goSyntax {
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 {
p.fmt0x64(uint64(u), !p.fmt.sharp)
}
}
var (
intBits = reflect.TypeOf(0).Bits()
floatBits = reflect.TypeOf(0.0).Bits()
complexBits = reflect.TypeOf(1i).Bits()
uintptrBits = reflect.TypeOf(uintptr(0)).Bits()
)
func (p *pp) catchPanic(field 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(field); 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 printField cannot succeed.
panic(err)
}
p.buf.WriteByte('%')
p.add(verb)
p.buf.Write(panicBytes)
p.panicking = true
p.printField(err, 'v', false, false, 0)
p.panicking = false
p.buf.WriteByte(')')
}
}
func (p *pp) handleMethods(verb rune, plus, goSyntax bool, depth int) (wasString, handled bool) {
if p.erroring {
return
}
// Is it a Formatter?
if formatter, ok := p.field.(Formatter); ok {
handled = true
wasString = false
defer p.catchPanic(p.field, verb)
formatter.Format(p, verb)
return
}
// Must not touch flags before Formatter looks at them.
if plus {
p.fmt.plus = false
}
// If we're doing Go syntax and the field knows how to supply it, take care of it now.
if goSyntax {
p.fmt.sharp = false
if stringer, ok := p.field.(GoStringer); ok {
wasString = false
handled = true
defer p.catchPanic(p.field, verb)
// Print the result of GoString unadorned.
p.fmtString(stringer.GoString(), 's', false)
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 wasString and handled, and deferring catchPanic,
// must happen before calling the method.
switch v := p.field.(type) {
case error:
wasString = false
handled = true
defer p.catchPanic(p.field, verb)
p.printField(v.Error(), verb, plus, false, depth)
return
case Stringer:
wasString = false
handled = true
defer p.catchPanic(p.field, verb)
p.printField(v.String(), verb, plus, false, depth)
return
}
}
}
handled = false
return
}
func (p *pp) printField(field interface{}, verb rune, plus, goSyntax bool, depth int) (wasString bool) {
if field == nil {
if verb == 'T' || verb == 'v' {
p.buf.Write(nilAngleBytes)
} else {
p.badVerb(verb)
}
return false
}
p.field = field
p.value = reflect.Value{}
// Special processing considerations.
// %T (the value's type) and %p (its address) are special; we always do them first.
switch verb {
case 'T':
p.printField(reflect.TypeOf(field).String(), 's', false, false, 0)
return false
case 'p':
p.fmtPointer(reflect.ValueOf(field), verb, goSyntax)
return false
}
if wasString, handled := p.handleMethods(verb, plus, goSyntax, depth); handled {
return wasString
}
// Some types can be done without reflection.
switch f := field.(type) {
case bool:
p.fmtBool(f, verb)
case float32:
p.fmtFloat32(f, verb)
case float64:
p.fmtFloat64(f, verb)
case complex64:
p.fmtComplex64(complex64(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, goSyntax)
case uint8:
p.fmtUint64(uint64(f), verb, goSyntax)
case uint16:
p.fmtUint64(uint64(f), verb, goSyntax)
case uint32:
p.fmtUint64(uint64(f), verb, goSyntax)
case uint64:
p.fmtUint64(f, verb, goSyntax)
case uintptr:
p.fmtUint64(uint64(f), verb, goSyntax)
case string:
p.fmtString(f, verb, goSyntax)
wasString = verb == 's' || verb == 'v'
case []byte:
p.fmtBytes(f, verb, goSyntax, depth)
wasString = verb == 's'
default:
// Need to use reflection
return p.printReflectValue(reflect.ValueOf(field), verb, plus, goSyntax, depth)
}
p.field = nil
return
}
// printValue is like printField but starts with a reflect value, not an interface{} value.
func (p *pp) printValue(value reflect.Value, verb rune, plus, goSyntax bool, 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.printField(value.Type().String(), 's', false, false, 0)
return false
case 'p':
p.fmtPointer(value, verb, goSyntax)
return false
}
// Handle values with special methods.
// Call always, even when field == nil, because handleMethods clears p.fmt.plus for us.
p.field = nil // Make sure it's cleared, for safety.
if value.CanInterface() {
p.field = value.Interface()
}
if wasString, handled := p.handleMethods(verb, plus, goSyntax, depth); handled {
return wasString
}
return p.printReflectValue(value, verb, plus, goSyntax, depth)
}
// printReflectValue is the fallback for both printField and printValue.
// It uses reflect to print the value.
func (p *pp) printReflectValue(value reflect.Value, verb rune, plus, goSyntax bool, depth int) (wasString bool) {
oldValue := p.value
p.value = value
BigSwitch:
switch f := value; f.Kind() {
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(uint64(f.Uint()), verb, goSyntax)
case reflect.Float32, reflect.Float64:
if f.Type().Size() == 4 {
p.fmtFloat32(float32(f.Float()), verb)
} else {
p.fmtFloat64(float64(f.Float()), verb)
}
case reflect.Complex64, reflect.Complex128:
if f.Type().Size() == 8 {
p.fmtComplex64(complex64(f.Complex()), verb)
} else {
p.fmtComplex128(complex128(f.Complex()), verb)
}
case reflect.String:
p.fmtString(f.String(), verb, goSyntax)
case reflect.Map:
if goSyntax {
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 goSyntax {
p.buf.Write(commaSpaceBytes)
} else {
p.buf.WriteByte(' ')
}
}
p.printValue(key, verb, plus, goSyntax, depth+1)
p.buf.WriteByte(':')
p.printValue(f.MapIndex(key), verb, plus, goSyntax, depth+1)
}
if goSyntax {
p.buf.WriteByte('}')
} else {
p.buf.WriteByte(']')
}
case reflect.Struct:
if goSyntax {
p.buf.WriteString(value.Type().String())
}
p.add('{')
v := f
t := v.Type()
for i := 0; i < v.NumField(); i++ {
if i > 0 {
if goSyntax {
p.buf.Write(commaSpaceBytes)
} else {
p.buf.WriteByte(' ')
}
}
if plus || goSyntax {
if f := t.Field(i); f.Name != "" {
p.buf.WriteString(f.Name)
p.buf.WriteByte(':')
}
}
p.printValue(getField(v, i), verb, plus, goSyntax, depth+1)
}
p.buf.WriteByte('}')
case reflect.Interface:
value := f.Elem()
if !value.IsValid() {
if goSyntax {
p.buf.WriteString(f.Type().String())
p.buf.Write(nilParenBytes)
} else {
p.buf.Write(nilAngleBytes)
}
} else {
wasString = p.printValue(value, verb, plus, goSyntax, depth+1)
}
case reflect.Array, reflect.Slice:
// Byte slices are special.
if f.Type().Elem().Kind() == reflect.Uint8 {
// We know it's a slice of bytes, but we also know it does not have static type
// []byte, or it would have been caught above. Therefore we cannot convert
// it directly in the (slightly) obvious way: f.Interface().([]byte); it doesn't have
// that type, and we can't write an expression of the right type and do a
// conversion because we don't have a static way to write the right type.
// 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, goSyntax, depth)
wasString = verb == 's'
break
}
if goSyntax {
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 goSyntax {
p.buf.Write(commaSpaceBytes)
} else {
p.buf.WriteByte(' ')
}
}
p.printValue(f.Index(i), verb, plus, goSyntax, depth+1)
}
if goSyntax {
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, plus, goSyntax, depth+1)
break BigSwitch
case reflect.Struct:
p.buf.WriteByte('&')
p.printValue(a, verb, plus, goSyntax, depth+1)
break BigSwitch
}
}
fallthrough
case reflect.Chan, reflect.Func, reflect.UnsafePointer:
p.fmtPointer(value, verb, goSyntax)
default:
p.unknownType(f)
}
p.value = oldValue
return wasString
}
// intFromArg gets the fieldnumth element of a. On return, isInt reports whether the argument has type int.
func intFromArg(a []interface{}, end, i, fieldnum int) (num int, isInt bool, newi, newfieldnum int) {
newi, newfieldnum = end, fieldnum
if i < end && fieldnum < len(a) {
num, isInt = a[fieldnum].(int)
newi, newfieldnum = i+1, fieldnum+1
}
return
}
func (p *pp) doPrintf(format string, a []interface{}) {
end := len(format)
fieldnum := 0 // we process one field per non-trivial format
for i := 0; i < end; {
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++
// flags and widths
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 width?
if i < end && format[i] == '*' {
p.fmt.wid, p.fmt.widPresent, i, fieldnum = intFromArg(a, end, i, fieldnum)
if !p.fmt.widPresent {
p.buf.Write(widthBytes)
}
} else {
p.fmt.wid, p.fmt.widPresent, i = parsenum(format, i, end)
}
// do we have precision?
if i < end && format[i] == '.' {
if format[i+1] == '*' {
p.fmt.prec, p.fmt.precPresent, i, fieldnum = intFromArg(a, end, i+1, fieldnum)
if !p.fmt.precPresent {
p.buf.Write(precBytes)
}
} else {
p.fmt.prec, p.fmt.precPresent, i = parsenum(format, i+1, end)
if !p.fmt.precPresent {
p.fmt.prec = 0
p.fmt.precPresent = true
}
}
}
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 fieldnum >= len(a) { // out of operands
p.buf.WriteByte('%')
p.add(c)
p.buf.Write(missingBytes)
continue
}
field := a[fieldnum]
fieldnum++
goSyntax := c == 'v' && p.fmt.sharp
plus := c == 'v' && p.fmt.plus
p.printField(field, c, plus, goSyntax, 0)
}
if fieldnum < len(a) {
p.buf.Write(extraBytes)
for ; fieldnum < len(a); fieldnum++ {
field := a[fieldnum]
if field != nil {
p.buf.WriteString(reflect.TypeOf(field).String())
p.buf.WriteByte('=')
}
p.printField(field, 'v', false, false, 0)
if fieldnum+1 < len(a) {
p.buf.Write(commaSpaceBytes)
}
}
p.buf.WriteByte(')')
}
}
func (p *pp) doPrint(a []interface{}, addspace, addnewline bool) {
prevString := false
for fieldnum := 0; fieldnum < len(a); fieldnum++ {
p.fmt.clearflags()
// always add spaces if we're doing println
field := a[fieldnum]
if fieldnum > 0 {
isString := field != nil && reflect.TypeOf(field).Kind() == reflect.String
if addspace || !isString && !prevString {
p.buf.WriteByte(' ')
}
}
prevString = p.printField(field, 'v', false, false, 0)
}
if addnewline {
p.buf.WriteByte('\n')
}
}