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fmt.Printf: introduce notation for random access to arguments.

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This text is added to doc.go:

        Explicit argument indexes:

        In Printf, Sprintf, and Fprintf, the default behavior is for each
        formatting verb to format successive arguments passed in the call.
        However, the notation [n] immediately before the verb indicates that the
        nth one-indexed argument is to be formatted instead. The same notation
        before a '*' for a width or precision selects the argument index holding
        the value. After processing a bracketed expression [n], arguments n+1,
        n+2, etc. will be processed unless otherwise directed.

        For example,
                fmt.Sprintf("%[2]d %[1]d\n", 11, 22)
        will yield "22, 11", while
                fmt.Sprintf("%[3]*[2].*[1]f", 12.0, 2, 6),
        equivalent to
                fmt.Sprintf("%6.2f", 12.0),
        will yield " 12.00". Because an explicit index affects subsequent verbs,
        this notation can be used to print the same values multiple times
        by resetting the index for the first argument to be repeated:
                fmt.Sprintf("%d %d %#[1]x %#x", 16, 17)
        will yield "16 17 0x10 0x11".

The notation chosen differs from that in C, but I believe it's easier to read
and to remember (we're indexing the arguments), and compatibility with
C's printf was never a strong goal anyway.

While we're here, change the word "field" to "arg" or "argument" in the
code; it was being misused and was confusing.

R=rsc, bradfitz, rogpeppe, minux.ma, peter.armitage
CC=golang-dev
https://golang.org/cl/9680043
This commit is contained in:
Rob Pike 2013-05-24 15:49:26 -07:00
parent ffe8a3c5e2
commit 7472ce0e58
5 changed files with 218 additions and 98 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
doc/go1.2.txt
View File

@ -8,4 +8,5 @@ Please keep the descriptions to a single line, starting with the
package or cmd/xxx directory name, and ending in a CL number.
Please keep the list sorted (as in sort.Strings of the lines).
fmt: indexed access to arguments in Printf etc. (CL 9680043).
io: Copy prioritizes WriterTo over ReaderFrom (CL 9462044).

24
src/pkg/fmt/doc.go
View File

@ -118,6 +118,28 @@
convert the value before recurring:
func (x X) String() string { return Sprintf("<%s>", string(x)) }
Explicit argument indexes:
In Printf, Sprintf, and Fprintf, the default behavior is for each
formatting verb to format successive arguments passed in the call.
However, the notation [n] immediately before the verb indicates that the
nth one-indexed argument is to be formatted instead. The same notation
before a '*' for a width or precision selects the argument index holding
the value. After processing a bracketed expression [n], arguments n+1,
n+2, etc. will be processed unless otherwise directed.
For example,
fmt.Sprintf("%[2]d %[1]d\n", 11, 22)
will yield "22, 11", while
fmt.Sprintf("%[3]*[2].*[1]f", 12.0, 2, 6),
equivalent to
fmt.Sprintf("%6.2f", 12.0),
will yield " 12.00". Because an explicit index affects subsequent verbs,
this notation can be used to print the same values multiple times
by resetting the index for the first argument to be repeated:
fmt.Sprintf("%d %d %#[1]x %#x", 16, 17)
will yield "16 17 0x10 0x11".
Format errors:
If an invalid argument is given for a verb, such as providing
@ -133,6 +155,8 @@
Non-int for width or precision: %!(BADWIDTH) or %!(BADPREC)
Printf("%*s", 4.5, "hi"): %!(BADWIDTH)hi
Printf("%.*s", 4.5, "hi"): %!(BADPREC)hi
Invalid or out-of-range argument index: %!(BADARGNUM)
Printf("%*[2]d", 7): %d(BADARGNUM)
All errors begin with the string "%!" followed sometimes
by a single character (the verb) and end with a parenthesized

40
src/pkg/fmt/fmt_test.go
View File

@ -110,7 +110,7 @@ var bslice = barray[:]
var b byte
var fmttests = []struct {
var fmtTests = []struct {
fmt string
val interface{}
out string
@ -503,7 +503,7 @@ var fmttests = []struct {
}
func TestSprintf(t *testing.T) {
for _, tt := range fmttests {
for _, tt := range fmtTests {
s := Sprintf(tt.fmt, tt.val)
if i := strings.Index(tt.out, "PTR"); i >= 0 {
pattern := "PTR"
@ -539,6 +539,42 @@ func TestSprintf(t *testing.T) {
}
}
type SE []interface{} // slice of empty; notational compactness.
var reorderTests = []struct {
fmt string
val SE
out string
}{
{"%[1]d", SE{1}, "1"},
{"%[2]d", SE{2, 1}, "1"},
{"%[2]d %[1]d", SE{1, 2}, "2 1"},
{"%[2]*[1]d", SE{2, 5}, " 2"},
{"%6.2f", SE{12.0}, " 12.00"},
{"%[3]*[2].*[1]f", SE{12.0, 2, 6}, " 12.00"},
{"%[1]*[2].*[3]f", SE{6, 2, 12.0}, " 12.00"},
// An actual use! Print the same arguments twice.
{"%d %d %d %#[1]o %#o %#o", SE{11, 12, 13}, "11 12 13 013 014 015"},
// Erroneous cases.
{"%[]d", SE{2, 1}, "%d(BADARGNUM)"},
{"%[-3]d", SE{2, 1}, "%d(BADARGNUM)"},
{"%[x]d", SE{2, 1}, "%d(BADARGNUM)"},
{"%[23]d", SE{2, 1}, "%d(BADARGNUM)"},
{"%[3]", SE{2, 1}, "%!(NOVERB)"},
{"%d %d %d %#[1]o %#o %#o %#o", SE{11, 12, 13}, "11 12 13 013 014 015 %o(MISSING)"},
}
func TestReorder(t *testing.T) {
for _, tt := range reorderTests {
s := Sprintf(tt.fmt, tt.val...)
if s != tt.out {
t.Errorf("Sprintf(%q, %v) = <%s> want <%s>", tt.fmt, tt.val, s, tt.out)
} else {
}
}
}
func BenchmarkSprintfEmpty(b *testing.B) {
for i := 0; i < b.N; i++ {
Sprintf("")

201
src/pkg/fmt/print.go
View File

@ -22,6 +22,7 @@ var (
nilBytes = []byte("nil")
mapBytes = []byte("map[")
missingBytes = []byte("(MISSING)")
badArgNum = []byte("(BADARGNUM)")
panicBytes = []byte("(PANIC=")
extraBytes = []byte("%!(EXTRA ")
irparenBytes = []byte("i)")
@ -109,11 +110,15 @@ type pp struct {
panicking bool
erroring bool // printing an error condition
buf buffer
// field holds the current item, as an interface{}.
field interface{}
// 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 last reordering directive was valid.
goodArgNum bool
runeBuf [utf8.UTFMax]byte
fmt fmt
}
@ -170,7 +175,7 @@ func (p *pp) free() {
return
}
p.buf = p.buf[:0]
p.field = nil
p.arg = nil
p.value = reflect.Value{}
ppFree.put(p)
}
@ -212,9 +217,9 @@ func (p *pp) Write(b []byte) (ret int, err error) {
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)
n, err = w.Write(p.buf)
p.free()
return int(n64), err
return
}
// Printf formats according to a format specifier and writes to standard output.
@ -246,9 +251,9 @@ func Errorf(format string, a ...interface{}) error {
func Fprint(w io.Writer, a ...interface{}) (n int, err error) {
p := newPrinter()
p.doPrint(a, false, false)
n64, err := w.Write(p.buf)
n, err = w.Write(p.buf)
p.free()
return int(n64), err
return
}
// Print formats using the default formats for its operands and writes to standard output.
@ -278,9 +283,9 @@ func Sprint(a ...interface{}) string {
func Fprintln(w io.Writer, a ...interface{}) (n int, err error) {
p := newPrinter()
p.doPrint(a, true, true)
n64, err := w.Write(p.buf)
n, err = w.Write(p.buf)
p.free()
return int(n64), err
return
}
// Println formats using the default formats for its operands and writes to standard output.
@ -300,8 +305,8 @@ func Sprintln(a ...interface{}) string {
return s
}
// getField gets the i'th arg of the struct value.
// If the arg itself is an interface, return a value for
// 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)
@ -340,10 +345,10 @@ func (p *pp) badVerb(verb rune) {
p.add(verb)
p.add('(')
switch {
case p.field != nil:
p.buf.WriteString(reflect.TypeOf(p.field).String())
case p.arg != nil:
p.buf.WriteString(reflect.TypeOf(p.arg).String())
p.add('=')
p.printField(p.field, 'v', false, false, 0)
p.printArg(p.arg, 'v', false, false, 0)
case p.value.IsValid():
p.buf.WriteString(p.value.Type().String())
p.add('=')
@ -566,7 +571,7 @@ func (p *pp) fmtBytes(v []byte, verb rune, goSyntax bool, typ reflect.Type, dept
p.buf.WriteByte(' ')
}
}
p.printField(c, 'v', p.fmt.plus, goSyntax, depth+1)
p.printArg(c, 'v', p.fmt.plus, goSyntax, depth+1)
}
if goSyntax {
p.buf.WriteByte('}')
@ -640,26 +645,26 @@ var (
uintptrBits = reflect.TypeOf(uintptr(0)).Bits()
)
func (p *pp) catchPanic(field interface{}, verb rune) {
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(field); v.Kind() == reflect.Ptr && v.IsNil() {
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 printField cannot succeed.
// Nested panics; the recursion in printArg 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.printArg(err, 'v', false, false, 0)
p.panicking = false
p.buf.WriteByte(')')
}
@ -670,10 +675,10 @@ func (p *pp) handleMethods(verb rune, plus, goSyntax bool, depth int) (wasString
return
}
// Is it a Formatter?
if formatter, ok := p.field.(Formatter); ok {
if formatter, ok := p.arg.(Formatter); ok {
handled = true
wasString = false
defer p.catchPanic(p.field, verb)
defer p.catchPanic(p.arg, verb)
formatter.Format(p, verb)
return
}
@ -682,13 +687,13 @@ func (p *pp) handleMethods(verb rune, plus, goSyntax bool, depth int) (wasString
p.fmt.plus = false
}
// If we're doing Go syntax and the field knows how to supply it, take care of it now.
// If we're doing Go syntax and the argument knows how to supply it, take care of it now.
if goSyntax {
p.fmt.sharp = false
if stringer, ok := p.field.(GoStringer); ok {
if stringer, ok := p.arg.(GoStringer); ok {
wasString = false
handled = true
defer p.catchPanic(p.field, verb)
defer p.catchPanic(p.arg, verb)
// Print the result of GoString unadorned.
p.fmtString(stringer.GoString(), 's', false)
return
@ -703,19 +708,19 @@ func (p *pp) handleMethods(verb rune, plus, goSyntax bool, depth int) (wasString
// 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) {
switch v := p.arg.(type) {
case error:
wasString = false
handled = true
defer p.catchPanic(p.field, verb)
p.printField(v.Error(), verb, plus, false, depth)
defer p.catchPanic(p.arg, verb)
p.printArg(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)
defer p.catchPanic(p.arg, verb)
p.printArg(v.String(), verb, plus, false, depth)
return
}
}
@ -724,11 +729,11 @@ func (p *pp) handleMethods(verb rune, plus, goSyntax bool, depth int) (wasString
return
}
func (p *pp) printField(field interface{}, verb rune, plus, goSyntax bool, depth int) (wasString bool) {
p.field = field
func (p *pp) printArg(arg interface{}, verb rune, plus, goSyntax bool, depth int) (wasString bool) {
p.arg = arg
p.value = reflect.Value{}
if field == nil {
if arg == nil {
if verb == 'T' || verb == 'v' {
p.fmt.pad(nilAngleBytes)
} else {
@ -741,10 +746,10 @@ func (p *pp) printField(field interface{}, verb rune, plus, goSyntax bool, depth
// %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)
p.printArg(reflect.TypeOf(arg).String(), 's', false, false, 0)
return false
case 'p':
p.fmtPointer(reflect.ValueOf(field), verb, goSyntax)
p.fmtPointer(reflect.ValueOf(arg), verb, goSyntax)
return false
}
@ -762,7 +767,7 @@ func (p *pp) printField(field interface{}, verb rune, plus, goSyntax bool, depth
}
// Some types can be done without reflection.
switch f := field.(type) {
switch f := arg.(type) {
case bool:
p.fmtBool(f, verb)
case float32:
@ -810,13 +815,13 @@ func (p *pp) printField(field interface{}, verb rune, plus, goSyntax bool, depth
return wasString
}
// Need to use reflection
return p.printReflectValue(reflect.ValueOf(field), verb, plus, goSyntax, depth)
return p.printReflectValue(reflect.ValueOf(arg), verb, plus, goSyntax, depth)
}
p.field = nil
p.arg = nil
return
}
// printValue is like printField but starts with a reflect value, not an interface{} value.
// printValue is like printArg 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' {
@ -831,7 +836,7 @@ func (p *pp) printValue(value reflect.Value, verb rune, plus, goSyntax bool, dep
// %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)
p.printArg(value.Type().String(), 's', false, false, 0)
return false
case 'p':
p.fmtPointer(value, verb, goSyntax)
@ -839,10 +844,10 @@ func (p *pp) printValue(value reflect.Value, verb rune, plus, goSyntax bool, dep
}
// 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.
// 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.field = value.Interface()
p.arg = value.Interface()
}
if wasString, handled := p.handleMethods(verb, plus, goSyntax, depth); handled {
return wasString
@ -851,7 +856,7 @@ func (p *pp) printValue(value reflect.Value, verb rune, plus, goSyntax bool, dep
return p.printReflectValue(value, verb, plus, goSyntax, depth)
}
// printReflectValue is the fallback for both printField and printValue.
// 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, plus, goSyntax bool, depth int) (wasString bool) {
oldValue := p.value
@ -1015,19 +1020,57 @@ BigSwitch:
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
// intFromArg gets the argNumth element of a. On return, isInt reports whether the argument has type int.
func intFromArg(a []interface{}, end, i, argNum int) (num int, isInt bool, newi, newArgNum int) {
newi, newArgNum = end, argNum
if i < end && argNum < len(a) {
num, isInt = a[argNum].(int)
newi, newArgNum = i+1, argNum+1
}
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) {
// Find closing parenthesis
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) {
p.goodArgNum = true
if len(format) <= i || format[i] != '[' {
return argNum, i
}
p.reordered = true
index, wid, ok := parseArgNumber(format[i:])
if ok && 0 <= index && index < numArgs {
return index, i + wid
}
p.goodArgNum = false
return argNum, i + wid
}
func (p *pp) doPrintf(format string, a []interface{}) {
end := len(format)
fieldnum := 0 // we process one field per non-trivial format
argNum := 0 // we process one argument per non-trivial format
p.reordered = false
for i := 0; i < end; {
lasti := i
for i < end && format[i] != '%' {
@ -1043,7 +1086,8 @@ func (p *pp) doPrintf(format string, a []interface{}) {
// Process one verb
i++
// flags and widths
// Do we have flags?
p.fmt.clearflags()
F:
for ; i < end; i++ {
@ -1062,22 +1106,29 @@ func (p *pp) doPrintf(format string, a []interface{}) {
break F
}
}
// do we have width?
// Do we have an explicit argument index?
argNum, i = p.argNumber(argNum, format, i, len(a))
// Do we have width?
if i < end && format[i] == '*' {
p.fmt.wid, p.fmt.widPresent, i, fieldnum = intFromArg(a, end, i, fieldnum)
p.fmt.wid, p.fmt.widPresent, i, argNum = intFromArg(a, end, i, argNum)
if !p.fmt.widPresent {
p.buf.Write(badWidthBytes)
}
argNum, i = p.argNumber(argNum, format, i, len(a)) // We consumed []; another can follow here.
} else {
p.fmt.wid, p.fmt.widPresent, i = parsenum(format, i, end)
}
// do we have precision?
// Do we have precision?
if i+1 < end && format[i] == '.' {
if format[i+1] == '*' {
p.fmt.prec, p.fmt.precPresent, i, fieldnum = intFromArg(a, end, i+1, fieldnum)
p.fmt.prec, p.fmt.precPresent, i, argNum = intFromArg(a, end, i+1, argNum)
if !p.fmt.precPresent {
p.buf.Write(badPrecBytes)
}
argNum, i = p.argNumber(argNum, format, i, len(a)) // We consumed []; another can follow here.
} else {
p.fmt.prec, p.fmt.precPresent, i = parsenum(format, i+1, end)
if !p.fmt.precPresent {
@ -1097,30 +1148,38 @@ func (p *pp) doPrintf(format string, a []interface{}) {
p.buf.WriteByte('%') // We ignore width and prec.
continue
}
if fieldnum >= len(a) { // out of operands
if !p.goodArgNum {
p.buf.WriteByte('%')
p.add(c)
p.buf.Write(badArgNum)
continue
} else if argNum >= len(a) { // out of operands
p.buf.WriteByte('%')
p.add(c)
p.buf.Write(missingBytes)
continue
}
field := a[fieldnum]
fieldnum++
arg := a[argNum]
argNum++
goSyntax := c == 'v' && p.fmt.sharp
plus := c == 'v' && p.fmt.plus
p.printField(field, c, plus, goSyntax, 0)
p.printArg(arg, c, plus, goSyntax, 0)
}
if fieldnum < len(a) {
// 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 ; fieldnum < len(a); fieldnum++ {
field := a[fieldnum]
if field != nil {
p.buf.WriteString(reflect.TypeOf(field).String())
for ; argNum < len(a); argNum++ {
arg := a[argNum]
if arg != nil {
p.buf.WriteString(reflect.TypeOf(arg).String())
p.buf.WriteByte('=')
}
p.printField(field, 'v', false, false, 0)
if fieldnum+1 < len(a) {
p.printArg(arg, 'v', false, false, 0)
if argNum+1 < len(a) {
p.buf.Write(commaSpaceBytes)
}
}
@ -1130,17 +1189,17 @@ func (p *pp) doPrintf(format string, a []interface{}) {
func (p *pp) doPrint(a []interface{}, addspace, addnewline bool) {
prevString := false
for fieldnum := 0; fieldnum < len(a); fieldnum++ {
for argNum := 0; argNum < len(a); argNum++ {
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
arg := a[argNum]
if argNum > 0 {
isString := arg != nil && reflect.TypeOf(arg).Kind() == reflect.String
if addspace || !isString && !prevString {
p.buf.WriteByte(' ')
}
}
prevString = p.printField(field, 'v', false, false, 0)
prevString = p.printArg(arg, 'v', false, false, 0)
}
if addnewline {
p.buf.WriteByte('\n')

36
src/pkg/fmt/scan.go
View File

@ -171,9 +171,9 @@ type ssave struct {
validSave bool // is or was a part of an actual ss.
nlIsEnd bool // whether newline terminates scan
nlIsSpace bool // whether newline counts as white space
fieldLimit int // max value of ss.count for this field; fieldLimit <= limit
argLimit int // max value of ss.count for this arg; argLimit <= limit
limit int // max value of ss.count.
maxWid int // width of this field.
maxWid int // width of this arg.
}
// The Read method is only in ScanState so that ScanState
@ -192,7 +192,7 @@ func (s *ss) ReadRune() (r rune, size int, err error) {
s.peekRune = -1
return
}
if s.atEOF || s.nlIsEnd && s.prevRune == '\n' || s.count >= s.fieldLimit {
if s.atEOF || s.nlIsEnd && s.prevRune == '\n' || s.count >= s.argLimit {
err = io.EOF
return
}
@ -389,7 +389,7 @@ func newScanState(r io.Reader, nlIsSpace, nlIsEnd bool) (s *ss, old ssave) {
s, ok := r.(*ss)
if ok {
old = s.ssave
s.limit = s.fieldLimit
s.limit = s.argLimit
s.nlIsEnd = nlIsEnd || s.nlIsEnd
s.nlIsSpace = nlIsSpace
return
@ -407,7 +407,7 @@ func newScanState(r io.Reader, nlIsSpace, nlIsEnd bool) (s *ss, old ssave) {
s.peekRune = -1
s.atEOF = false
s.limit = hugeWid
s.fieldLimit = hugeWid
s.argLimit = hugeWid
s.maxWid = hugeWid
s.validSave = true
s.count = 0
@ -477,8 +477,8 @@ func (s *ss) token(skipSpace bool, f func(rune) bool) []byte {
}
// typeError indicates that the type of the operand did not match the format
func (s *ss) typeError(field interface{}, expected string) {
s.errorString("expected field of type pointer to " + expected + "; found " + reflect.TypeOf(field).String())
func (s *ss) typeError(arg interface{}, expected string) {
s.errorString("expected argument of type pointer to " + expected + "; found " + reflect.TypeOf(arg).String())
}
var complexError = errors.New("syntax error scanning complex number")
@ -927,11 +927,11 @@ const floatVerbs = "beEfFgGv"
const hugeWid = 1 << 30
// scanOne scans a single value, deriving the scanner from the type of the argument.
func (s *ss) scanOne(verb rune, field interface{}) {
func (s *ss) scanOne(verb rune, arg interface{}) {
s.buf = s.buf[:0]
var err error
// If the parameter has its own Scan method, use that.
if v, ok := field.(Scanner); ok {
if v, ok := arg.(Scanner); ok {
err = v.Scan(s, verb)
if err != nil {
if err == io.EOF {
@ -942,7 +942,7 @@ func (s *ss) scanOne(verb rune, field interface{}) {
return
}
switch v := field.(type) {
switch v := arg.(type) {
case *bool:
*v = s.scanBool(verb)
case *complex64:
@ -1046,8 +1046,8 @@ func errorHandler(errp *error) {
// doScan does the real work for scanning without a format string.
func (s *ss) doScan(a []interface{}) (numProcessed int, err error) {
defer errorHandler(&err)
for _, field := range a {
s.scanOne('v', field)
for _, arg := range a {
s.scanOne('v', arg)
numProcessed++
}
// Check for newline if required.
@ -1144,9 +1144,9 @@ func (s *ss) doScanf(format string, a []interface{}) (numProcessed int, err erro
if !widPresent {
s.maxWid = hugeWid
}
s.fieldLimit = s.limit
if f := s.count + s.maxWid; f < s.fieldLimit {
s.fieldLimit = f
s.argLimit = s.limit
if f := s.count + s.maxWid; f < s.argLimit {
s.argLimit = f
}
c, w := utf8.DecodeRuneInString(format[i:])
@ -1156,11 +1156,11 @@ func (s *ss) doScanf(format string, a []interface{}) (numProcessed int, err erro
s.errorString("too few operands for format %" + format[i-w:])
break
}
field := a[numProcessed]
arg := a[numProcessed]
s.scanOne(c, field)
s.scanOne(c, arg)
numProcessed++
s.fieldLimit = s.limit
s.argLimit = s.limit
}
if numProcessed < len(a) {
s.errorString("too many operands")