From 71387ff53f95ddd5f0bb91d7e4c92ccdc65238e7 Mon Sep 17 00:00:00 2001

From: Rob Pike <[email protected]>

Date: Sun, 23 Aug 2015 17:45:58 +1000

Subject: [PATCH 20/63] [release-branch.go1.5] fmt: in Scanf, %c can scan a

 space, so don't skip spaces at %c

In short, %c should just give you the next rune, period.

Apparently this is the design. I use the term loosely.

Fixes #12275

Change-Id: I6f30bed442c0e88eac2244d465c7d151b29cf393

Reviewed-on: https://go-review.googlesource.com/13821

Reviewed-by: Andrew Gerrand <[email protected]>

Reviewed-on: https://go-review.googlesource.com/14395

---

 src/fmt/scan.go      | 13 +++++++++----

 src/fmt/scan_test.go | 11 +++++++----

 2 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/src/fmt/scan.go b/src/fmt/scan.go

index 5b9b516..e3e0fd0 100644

--- a/src/fmt/scan.go

+++ b/src/fmt/scan.go

@@ -83,6 +83,8 @@ func Scanln(a ...interface{}) (n int, err error) {

 // the format.  It returns the number of items successfully scanned.

 // If that is less than the number of arguments, err will report why.

 // Newlines in the input must match newlines in the format.

+// The one exception: the verb %c always scans the next rune in the

+// input, even if it is a space (or tab etc.) or newline.

 func Scanf(format string, a ...interface{}) (n int, err error) {

 	return Fscanf(os.Stdin, format, a...)

 }

@@ -1164,15 +1166,18 @@ func (s *ss) doScanf(format string, a []interface{}) (numProcessed int, err erro

 		if !widPresent {

 			s.maxWid = hugeWid

 		}

-		s.SkipSpace()

+

+		c, w := utf8.DecodeRuneInString(format[i:])

+		i += w

+

+		if c != 'c' {

+			s.SkipSpace()

+		}

 		s.argLimit = s.limit

 		if f := s.count + s.maxWid; f < s.argLimit {

 			s.argLimit = f

 		}

-		c, w := utf8.DecodeRuneInString(format[i:])

-		i += w

-

 		if numProcessed >= len(a) { // out of operands

 			s.errorString("too few operands for format %" + format[i-w:])

 			break

diff --git a/src/fmt/scan_test.go b/src/fmt/scan_test.go

index a378436..334c4a6 100644

--- a/src/fmt/scan_test.go

+++ b/src/fmt/scan_test.go

@@ -300,10 +300,13 @@ var scanfTests = []ScanfTest{

 	{"%2s", "sssss", &xVal, Xs("ss")},

 	// Fixed bugs

-	{"%d\n", "27\n", &intVal, 27},  // ok

-	{"%d\n", "28 \n", &intVal, 28}, // was: "unexpected newline"

-	{"%v", "0", &intVal, 0},        // was: "EOF"; 0 was taken as base prefix and not counted.

-	{"%v", "0", &uintVal, uint(0)}, // was: "EOF"; 0 was taken as base prefix and not counted.

+	{"%d\n", "27\n", &intVal, 27},      // ok

+	{"%d\n", "28 \n", &intVal, 28},     // was: "unexpected newline"

+	{"%v", "0", &intVal, 0},            // was: "EOF"; 0 was taken as base prefix and not counted.

+	{"%v", "0", &uintVal, uint(0)},     // was: "EOF"; 0 was taken as base prefix and not counted.

+	{"%c", " ", &uintVal, uint(' ')},   // %c must accept a blank.

+	{"%c", "\t", &uintVal, uint('\t')}, // %c must accept any space.

+	{"%c", "\n", &uintVal, uint('\n')}, // %c must accept any space.

 }

 var overflowTests = []ScanTest{

-- 

2.6.1