fmt: simplify the code some more by storing the field in the pp structure.

R=rsc
CC=golang-dev
https://golang.org/cl/5293058

src/pkg/fmt/print.go

@@ -74,6 +74,8 @@ type pp struct {
 	n         int
 	panicking bool
 	buf       bytes.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
@@ -132,6 +134,7 @@ func (p *pp) free() {
 		return
 	}
 	p.buf.Reset()
+	p.field = nil
 	p.value = reflect.Value{}
 	ppFree.put(p)
 }
@@ -294,16 +297,16 @@ func (p *pp) unknownType(v interface{}) {
 	p.buf.WriteByte('?')
 }
 
-func (p *pp) badVerb(verb int, val interface{}) {
+func (p *pp) badVerb(verb int) {
 	p.add('%')
 	p.add('!')
 	p.add(verb)
 	p.add('(')
 	switch {
-	case val != nil:
-		p.buf.WriteString(reflect.TypeOf(val).String())
+	case p.field != nil:
+		p.buf.WriteString(reflect.TypeOf(p.field).String())
 		p.add('=')
-		p.printField(val, 'v', false, false, 0)
+		p.printField(p.field, 'v', false, false, 0)
 	case p.value.IsValid():
 		p.buf.WriteString(p.value.Type().String())
 		p.add('=')
@@ -314,12 +317,12 @@ func (p *pp) badVerb(verb int, val interface{}) {
 	p.add(')')
 }
 
-func (p *pp) fmtBool(v bool, verb int, value interface{}) {
+func (p *pp) fmtBool(v bool, verb int) {
 	switch verb {
 	case 't', 'v':
 		p.fmt.fmt_boolean(v)
 	default:
-		p.badVerb(verb, value)
+		p.badVerb(verb)
 	}
 }
 
@@ -333,7 +336,7 @@ func (p *pp) fmtC(c int64) {
 	p.fmt.pad(p.runeBuf[0:w])
 }
 
-func (p *pp) fmtInt64(v int64, verb int, value interface{}) {
+func (p *pp) fmtInt64(v int64, verb int) {
 	switch verb {
 	case 'b':
 		p.fmt.integer(v, 2, signed, ldigits)
@@ -347,7 +350,7 @@ func (p *pp) fmtInt64(v int64, verb int, value interface{}) {
 		if 0 <= v && v <= unicode.MaxRune {
 			p.fmt.fmt_qc(v)
 		} else {
-			p.badVerb(verb, value)
+			p.badVerb(verb)
 		}
 	case 'x':
 		p.fmt.integer(v, 16, signed, ldigits)
@@ -356,7 +359,7 @@ func (p *pp) fmtInt64(v int64, verb int, value interface{}) {
 	case 'X':
 		p.fmt.integer(v, 16, signed, udigits)
 	default:
-		p.badVerb(verb, value)
+		p.badVerb(verb)
 	}
 }
 
@@ -391,7 +394,7 @@ func (p *pp) fmtUnicode(v int64) {
 	p.fmt.sharp = sharp
 }
 
-func (p *pp) fmtUint64(v uint64, verb int, goSyntax bool, value interface{}) {
+func (p *pp) fmtUint64(v uint64, verb int, goSyntax bool) {
 	switch verb {
 	case 'b':
 		p.fmt.integer(int64(v), 2, unsigned, ldigits)
@@ -411,7 +414,7 @@ func (p *pp) fmtUint64(v uint64, verb int, goSyntax bool, value interface{}) {
 		if 0 <= v && v <= unicode.MaxRune {
 			p.fmt.fmt_qc(int64(v))
 		} else {
-			p.badVerb(verb, value)
+			p.badVerb(verb)
 		}
 	case 'x':
 		p.fmt.integer(int64(v), 16, unsigned, ldigits)
@@ -420,11 +423,11 @@ func (p *pp) fmtUint64(v uint64, verb int, goSyntax bool, value interface{}) {
 	case 'U':
 		p.fmtUnicode(int64(v))
 	default:
-		p.badVerb(verb, value)
+		p.badVerb(verb)
 	}
 }
 
-func (p *pp) fmtFloat32(v float32, verb int, value interface{}) {
+func (p *pp) fmtFloat32(v float32, verb int) {
 	switch verb {
 	case 'b':
 		p.fmt.fmt_fb32(v)
@@ -439,11 +442,11 @@ func (p *pp) fmtFloat32(v float32, verb int, value interface{}) {
 	case 'G':
 		p.fmt.fmt_G32(v)
 	default:
-		p.badVerb(verb, value)
+		p.badVerb(verb)
 	}
 }
 
-func (p *pp) fmtFloat64(v float64, verb int, value interface{}) {
+func (p *pp) fmtFloat64(v float64, verb int) {
 	switch verb {
 	case 'b':
 		p.fmt.fmt_fb64(v)
@@ -458,33 +461,33 @@ func (p *pp) fmtFloat64(v float64, verb int, value interface{}) {
 	case 'G':
 		p.fmt.fmt_G64(v)
 	default:
-		p.badVerb(verb, value)
+		p.badVerb(verb)
 	}
 }
 
-func (p *pp) fmtComplex64(v complex64, verb int, value interface{}) {
+func (p *pp) fmtComplex64(v complex64, verb int) {
 	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, value)
+		p.badVerb(verb)
 	}
 }
 
-func (p *pp) fmtComplex128(v complex128, verb int, value interface{}) {
+func (p *pp) fmtComplex128(v complex128, verb int) {
 	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, value)
+		p.badVerb(verb)
 	}
 }
 
-func (p *pp) fmtString(v string, verb int, goSyntax bool, value interface{}) {
+func (p *pp) fmtString(v string, verb int, goSyntax bool) {
 	switch verb {
 	case 'v':
 		if goSyntax {
@@ -501,11 +504,11 @@ func (p *pp) fmtString(v string, verb int, goSyntax bool, value interface{}) {
 	case 'q':
 		p.fmt.fmt_q(v)
 	default:
-		p.badVerb(verb, value)
+		p.badVerb(verb)
 	}
 }
 
-func (p *pp) fmtBytes(v []byte, verb int, goSyntax bool, depth int, value interface{}) {
+func (p *pp) fmtBytes(v []byte, verb int, goSyntax bool, depth int) {
 	if verb == 'v' || verb == 'd' {
 		if goSyntax {
 			p.buf.Write(bytesBytes)
@@ -540,17 +543,17 @@ func (p *pp) fmtBytes(v []byte, verb int, goSyntax bool, depth int, value interf
 	case 'q':
 		p.fmt.fmt_q(s)
 	default:
-		p.badVerb(verb, value)
+		p.badVerb(verb)
 	}
 }
 
-func (p *pp) fmtPointer(field interface{}, value reflect.Value, verb int, goSyntax bool) {
+func (p *pp) fmtPointer(value reflect.Value, verb int, goSyntax bool) {
 	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, field)
+		p.badVerb(verb)
 		return
 	}
 	if goSyntax {
@@ -576,12 +579,12 @@ var (
 	uintptrBits = reflect.TypeOf(uintptr(0)).Bits()
 )
 
-func (p *pp) catchPanic(val interface{}, verb int) {
+func (p *pp) catchPanic(field interface{}, verb int) {
 	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(val); v.Kind() == reflect.Ptr && v.IsNil() {
+		if v := reflect.ValueOf(field); v.Kind() == reflect.Ptr && v.IsNil() {
 			p.buf.Write(nilAngleBytes)
 			return
 		}
@@ -601,12 +604,12 @@ func (p *pp) catchPanic(val interface{}, verb int) {
 	}
 }
 
-func (p *pp) handleMethods(field interface{}, verb int, plus, goSyntax bool, depth int) (wasString, handled bool) {
+func (p *pp) handleMethods(verb int, plus, goSyntax bool, depth int) (wasString, handled bool) {
 	// Is it a Formatter?
-	if formatter, ok := field.(Formatter); ok {
+	if formatter, ok := p.field.(Formatter); ok {
 		handled = true
 		wasString = false
-		defer p.catchPanic(field, verb)
+		defer p.catchPanic(p.field, verb)
 		formatter.Format(p, verb)
 		return
 	}
@@ -618,20 +621,20 @@ func (p *pp) handleMethods(field interface{}, verb int, plus, goSyntax bool, dep
 	// 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 := field.(GoStringer); ok {
+		if stringer, ok := p.field.(GoStringer); ok {
 			wasString = false
 			handled = true
-			defer p.catchPanic(field, verb)
+			defer p.catchPanic(p.field, verb)
 			// Print the result of GoString unadorned.
-			p.fmtString(stringer.GoString(), 's', false, field)
+			p.fmtString(stringer.GoString(), 's', false)
 			return
 		}
 	} else {
 		// Is it a Stringer?
-		if stringer, ok := field.(Stringer); ok {
+		if stringer, ok := p.field.(Stringer); ok {
 			wasString = false
 			handled = true
-			defer p.catchPanic(field, verb)
+			defer p.catchPanic(p.field, verb)
 			p.printField(stringer.String(), verb, plus, false, depth)
 			return
 		}
@@ -645,11 +648,13 @@ func (p *pp) printField(field interface{}, verb int, plus, goSyntax bool, depth
 		if verb == 'T' || verb == 'v' {
 			p.buf.Write(nilAngleBytes)
 		} else {
-			p.badVerb(verb, field)
+			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 {
@@ -657,74 +662,60 @@ func (p *pp) printField(field interface{}, verb int, plus, goSyntax bool, depth
 		p.printField(reflect.TypeOf(field).String(), 's', false, false, 0)
 		return false
 	case 'p':
-		p.fmtPointer(field, reflect.ValueOf(field), verb, goSyntax)
+		p.fmtPointer(reflect.ValueOf(field), verb, goSyntax)
 		return false
 	}
 
-	if wasString, handled := p.handleMethods(field, verb, plus, goSyntax, depth); handled {
+	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, field)
-		return false
+		p.fmtBool(f, verb)
 	case float32:
-		p.fmtFloat32(f, verb, field)
-		return false
+		p.fmtFloat32(f, verb)
 	case float64:
-		p.fmtFloat64(f, verb, field)
-		return false
+		p.fmtFloat64(f, verb)
 	case complex64:
-		p.fmtComplex64(complex64(f), verb, field)
-		return false
+		p.fmtComplex64(complex64(f), verb)
 	case complex128:
-		p.fmtComplex128(f, verb, field)
-		return false
+		p.fmtComplex128(f, verb)
 	case int:
-		p.fmtInt64(int64(f), verb, field)
-		return false
+		p.fmtInt64(int64(f), verb)
 	case int8:
-		p.fmtInt64(int64(f), verb, field)
-		return false
+		p.fmtInt64(int64(f), verb)
 	case int16:
-		p.fmtInt64(int64(f), verb, field)
-		return false
+		p.fmtInt64(int64(f), verb)
 	case int32:
-		p.fmtInt64(int64(f), verb, field)
-		return false
+		p.fmtInt64(int64(f), verb)
 	case int64:
-		p.fmtInt64(f, verb, field)
-		return false
+		p.fmtInt64(f, verb)
 	case uint:
-		p.fmtUint64(uint64(f), verb, goSyntax, field)
-		return false
+		p.fmtUint64(uint64(f), verb, goSyntax)
 	case uint8:
-		p.fmtUint64(uint64(f), verb, goSyntax, field)
-		return false
+		p.fmtUint64(uint64(f), verb, goSyntax)
 	case uint16:
-		p.fmtUint64(uint64(f), verb, goSyntax, field)
-		return false
+		p.fmtUint64(uint64(f), verb, goSyntax)
 	case uint32:
-		p.fmtUint64(uint64(f), verb, goSyntax, field)
-		return false
+		p.fmtUint64(uint64(f), verb, goSyntax)
 	case uint64:
-		p.fmtUint64(f, verb, goSyntax, field)
-		return false
+		p.fmtUint64(f, verb, goSyntax)
 	case uintptr:
-		p.fmtUint64(uint64(f), verb, goSyntax, field)
-		return false
+		p.fmtUint64(uint64(f), verb, goSyntax)
 	case string:
-		p.fmtString(f, verb, goSyntax, field)
-		return verb == 's' || verb == 'v'
+		p.fmtString(f, verb, goSyntax)
+		wasString = verb == 's' || verb == 'v'
 	case []byte:
-		p.fmtBytes(f, verb, goSyntax, depth, field)
-		return verb == 's'
+		p.fmtBytes(f, verb, goSyntax, depth)
+		wasString = verb == 's'
+	default:
+		// Need to use reflection
+		return p.printReflectValue(reflect.ValueOf(field), verb, plus, goSyntax, depth)
 	}
-
-	// 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.
@@ -733,7 +724,7 @@ func (p *pp) printValue(value reflect.Value, verb int, plus, goSyntax bool, dept
 		if verb == 'T' || verb == 'v' {
 			p.buf.Write(nilAngleBytes)
 		} else {
-			p.badVerb(verb, nil)
+			p.badVerb(verb)
 		}
 		return false
 	}
@@ -745,17 +736,17 @@ func (p *pp) printValue(value reflect.Value, verb int, plus, goSyntax bool, dept
 		p.printField(value.Type().String(), 's', false, false, 0)
 		return false
 	case 'p':
-		p.fmtPointer(nil, value, verb, goSyntax)
+		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.
-	var field interface{}
+	p.field = nil // Make sure it's cleared, for safety.
 	if value.CanInterface() {
-		field = value.Interface()
+		p.field = value.Interface()
 	}
-	if wasString, handled := p.handleMethods(field, verb, plus, goSyntax, depth); handled {
+	if wasString, handled := p.handleMethods(verb, plus, goSyntax, depth); handled {
 		return wasString
 	}
 
@@ -770,25 +761,25 @@ func (p *pp) printReflectValue(value reflect.Value, verb int, plus, goSyntax boo
 BigSwitch:
 	switch f := value; f.Kind() {
 	case reflect.Bool:
-		p.fmtBool(f.Bool(), verb, nil)
+		p.fmtBool(f.Bool(), verb)
 	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
-		p.fmtInt64(f.Int(), verb, nil)
+		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, nil)
+		p.fmtUint64(uint64(f.Uint()), verb, goSyntax)
 	case reflect.Float32, reflect.Float64:
 		if f.Type().Size() == 4 {
-			p.fmtFloat32(float32(f.Float()), verb, nil)
+			p.fmtFloat32(float32(f.Float()), verb)
 		} else {
-			p.fmtFloat64(float64(f.Float()), verb, nil)
+			p.fmtFloat64(float64(f.Float()), verb)
 		}
 	case reflect.Complex64, reflect.Complex128:
 		if f.Type().Size() == 8 {
-			p.fmtComplex64(complex64(f.Complex()), verb, nil)
+			p.fmtComplex64(complex64(f.Complex()), verb)
 		} else {
-			p.fmtComplex128(complex128(f.Complex()), verb, nil)
+			p.fmtComplex128(complex128(f.Complex()), verb)
 		}
 	case reflect.String:
-		p.fmtString(f.String(), verb, goSyntax, nil)
+		p.fmtString(f.String(), verb, goSyntax)
 	case reflect.Map:
 		if goSyntax {
 			p.buf.WriteString(f.Type().String())
@@ -864,7 +855,7 @@ BigSwitch:
 			for i := range bytes {
 				bytes[i] = byte(f.Index(i).Uint())
 			}
-			p.fmtBytes(bytes, verb, goSyntax, depth, nil)
+			p.fmtBytes(bytes, verb, goSyntax, depth)
 			wasString = verb == 's'
 			break
 		}
@@ -924,7 +915,7 @@ BigSwitch:
 		}
 		p.fmt0x64(uint64(v), true)
 	case reflect.Chan, reflect.Func, reflect.UnsafePointer:
-		p.fmtPointer(nil, value, verb, goSyntax)
+		p.fmtPointer(value, verb, goSyntax)
 	default:
 		p.unknownType(f)
 	}