strings: add function SingleSpace

The SingleSpace function convert all sequences of white spaces into
single space ' '.

2 files changed, 42 insertions, 0 deletions

diff --git a/lib/strings/string.go b/lib/strings/string.go
index 5eb7d6b7..68aedb9d 100644
--- a/lib/strings/string.go
+++ b/lib/strings/string.go
@@ -138,6 +138,32 @@ func Reverse(input string) string {
 }
 
 //
+// SingleSpace convert all sequences of white spaces into single space ' '.
+//
+func SingleSpace(in string) string {
+	var isspace bool
+	out := make([]rune, 0, len(in))
+	for _, r := range in {
+		if unicode.IsSpace(r) {
+			if isspace {
+				continue
+			}
+			isspace = true
+			continue
+		}
+		if isspace {
+			out = append(out, ' ')
+			isspace = false
+		}
+		out = append(out, r)
+	}
+	if isspace {
+		out = append(out, ' ')
+	}
+	return string(out)
+}
+
+//
 // Split given a text, return all words in text.
 //
 // A word is any sequence of character which have length equal or greater than
diff --git a/lib/strings/string_test.go b/lib/strings/string_test.go
index 7ee0c078..d161dfd7 100644
--- a/lib/strings/string_test.go
+++ b/lib/strings/string_test.go
@@ -117,6 +117,22 @@ func TestReverse(t *testing.T) {
 	}
 }
 
+func TestSingleSpace(t *testing.T) {
+	cases := []struct {
+		in  string
+		exp string
+	}{{
+		in: "",
+	}, {
+		in:  " \t\v\r\n\r\n\fa \t\v\r\n\r\n\f",
+		exp: " a ",
+	}}
+	for _, c := range cases {
+		got := SingleSpace(c.in)
+		test.Assert(t, c.in, c.exp, got, true)
+	}
+}
+
 func TestSplit(t *testing.T) {
 	cases := []struct {
 		text string