Commit 3748d226 authored by Rob Pike's avatar Rob Pike

fmt.Scanf: improve error message when input does not match format

R=rsc
CC=golang-dev
https://golang.org/cl/1693043
parent 4fd7880d
......@@ -885,6 +885,7 @@ func (s *ss) doScan(a []interface{}) (numProcessed int, err os.Error) {
// either input or format behave as a single space. This routine also
// handles the %% case. If the return value is zero, either format
// starts with a % (with no following %) or the input is empty.
// If it is negative, the input did not match the string.
func (s *ss) advance(format string) (i int) {
for i < len(format) {
fmtc, w := utf8.DecodeRuneInString(format[i:])
......@@ -919,7 +920,7 @@ func (s *ss) advance(format string) (i int) {
inputc := s.mustGetRune()
if fmtc != inputc {
s.UngetRune(inputc)
return
return -1
}
i += w
}
......@@ -940,10 +941,11 @@ func (s *ss) doScanf(format string, a []interface{}) (numProcessed int, err os.E
}
// Either we failed to advance, we have a percent character, or we ran out of input.
if format[i] != '%' {
// Can't advance format. Do we have arguments still to process?
if i < len(a) {
s.errorString("too many arguments for format")
// Can't advance format. Why not?
if w < 0 {
s.errorString("input does not match format")
}
// Otherwise at EOF; "too many operands" error handled below
break
}
i++ // % is one byte
......
......@@ -303,6 +303,7 @@ var multiTests = []ScanfMultiTest{
ScanfMultiTest{"%d %d %d", "23 18", args(&i, &j), args(23, 18), "too few operands"},
ScanfMultiTest{"%d %d", "23 18 27", args(&i, &j, &k), args(23, 18), "too many operands"},
ScanfMultiTest{"%c", "\u0100", args(&int8Val), nil, "overflow"},
ScanfMultiTest{"X%d", "10X", args(&intVal), nil, "input does not match format"},
// Bad UTF-8: should see every byte.
ScanfMultiTest{"%c%c%c", "\xc2X\xc2", args(&i, &j, &k), args(utf8.RuneError, 'X', utf8.RuneError), ""},
......
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