Adds unmodified source files from golang.org.

third_party/golang/src/fmt/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 (
+        "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 == 100 {
+                        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')
+        }
+}