bytes: add IndexRune, FieldsFunc and To*Special

Basically these functions are implemented the same way as the
corresponding functions in the strings package.  Test functions
are implemented for IndexRune and FieldsFunc.

Additionally two typos are fixed in packages bytes and strings.

R=r
CC=golang-dev
https://golang.org/cl/1696062

3 files changed, 83 insertions, 5 deletions

diff --git a/src/pkg/bytes/bytes.go b/src/pkg/bytes/bytes.go
index 6eb6772328..e0b30b9677 100644
--- a/src/pkg/bytes/bytes.go
+++ b/src/pkg/bytes/bytes.go
@@ -3,7 +3,7 @@
 // license that can be found in the LICENSE file.
 
 // The bytes package implements functions for the manipulation of byte slices.
-// Analagous to the facilities of the strings package.
+// Analogous to the facilities of the strings package.
 package bytes
 
 import (
@@ -127,6 +127,20 @@ func LastIndex(s, sep []byte) int {
 	return -1
 }
 
+// IndexRune interprets s as a sequence of UTF-8-encoded Unicode code points.
+// It returns the byte index of the first occurrence in s of the given rune.
+// It returns -1 if rune is not present in s.
+func IndexRune(s []byte, rune int) int {
+	for i := 0; i < len(s); {
+		r, size := utf8.DecodeRune(s[i:])
+		if r == rune {
+			return i
+		}
+		i += size
+	}
+	return -1
+}
+
 // IndexAny interprets s as a sequence of UTF-8-encoded Unicode code points.
 // It returns the byte index of the first occurrence in s of any of the Unicode
 // code points in chars.  It returns -1 if chars is empty or if there is no code
@@ -202,12 +216,20 @@ func SplitAfter(s, sep []byte, n int) [][]byte {
 // Fields splits the array s around each instance of one or more consecutive white space
 // characters, returning a slice of subarrays of s or an empty list if s contains only white space.
 func Fields(s []byte) [][]byte {
+	return FieldsFunc(s, unicode.IsSpace)
+}
+
+// FieldsFunc interprets s as a sequence of UTF-8-encoded Unicode code points.
+// It splits the array s at each run of code points c satisfying f(c) and
+// returns a slice of subarrays of s.  If no code points in s satisfy f(c), an
+// empty slice is returned.
+func FieldsFunc(s []byte, f func(int) bool) [][]byte {
 	n := 0
 	inField := false
 	for i := 0; i < len(s); {
 		rune, size := utf8.DecodeRune(s[i:])
 		wasInField := inField
-		inField = !unicode.IsSpace(rune)
+		inField = !f(rune)
 		if inField && !wasInField {
 			n++
 		}
@@ -219,12 +241,12 @@ func Fields(s []byte) [][]byte {
 	fieldStart := -1
 	for i := 0; i <= len(s) && na < n; {
 		rune, size := utf8.DecodeRune(s[i:])
-		if fieldStart < 0 && size > 0 && !unicode.IsSpace(rune) {
+		if fieldStart < 0 && size > 0 && !f(rune) {
 			fieldStart = i
 			i += size
 			continue
 		}
-		if fieldStart >= 0 && (size == 0 || unicode.IsSpace(rune)) {
+		if fieldStart >= 0 && (size == 0 || f(rune)) {
 			a[na] = s[fieldStart:i]
 			na++
 			fieldStart = -1
@@ -337,6 +359,25 @@ func ToLower(s []byte) []byte { return Map(unicode.ToLower, s) }
 // ToTitle returns a copy of the byte array s with all Unicode letters mapped to their title case.
 func ToTitle(s []byte) []byte { return Map(unicode.ToTitle, s) }
 
+// ToUpperSpecial returns a copy of the byte array s with all Unicode letters mapped to their
+// upper case, giving priority to the special casing rules.
+func ToUpperSpecial(_case unicode.SpecialCase, s []byte) []byte {
+	return Map(func(r int) int { return _case.ToUpper(r) }, s)
+}
+
+// ToLowerSpecial returns a copy of the byte array s with all Unicode letters mapped to their
+// lower case, giving priority to the special casing rules.
+func ToLowerSpecial(_case unicode.SpecialCase, s []byte) []byte {
+	return Map(func(r int) int { return _case.ToLower(r) }, s)
+}
+
+// ToTitleSpecial returns a copy of the byte array s with all Unicode letters mapped to their
+// title case, giving priority to the special casing rules.
+func ToTitleSpecial(_case unicode.SpecialCase, s []byte) []byte {
+	return Map(func(r int) int { return _case.ToTitle(r) }, s)
+}
+
+
 // isSeparator reports whether the rune could mark a word boundary.
 // TODO: update when package unicode captures more of the properties.
 func isSeparator(rune int) bool {
diff --git a/src/pkg/bytes/bytes_test.go b/src/pkg/bytes/bytes_test.go
index b91ae5734d..de503878cd 100644
--- a/src/pkg/bytes/bytes_test.go
+++ b/src/pkg/bytes/bytes_test.go
@@ -125,6 +125,15 @@ var indexAnyTests = []BinOpTest{
 	BinOpTest{dots + dots + dots, " ", -1},
 }
 
+var indexRuneTests = []BinOpTest{
+	BinOpTest{"", "a", -1},
+	BinOpTest{"", "☺", -1},
+	BinOpTest{"foo", "☹", -1},
+	BinOpTest{"foo", "o", 1},
+	BinOpTest{"foo☺bar", "☺", 3},
+	BinOpTest{"foo☺☻☹bar", "☹", 9},
+}
+
 // Execute f on each test case.  funcName should be the name of f; it's used
 // in failure reports.
 func runIndexTests(t *testing.T, f func(s, sep []byte) int, funcName string, testCases []BinOpTest) {
@@ -168,6 +177,17 @@ func TestIndexByte(t *testing.T) {
 	}
 }
 
+func TestIndexRune(t *testing.T) {
+	for _, tt := range indexRuneTests {
+		a := []byte(tt.a)
+		r, _ := utf8.DecodeRuneInString(tt.b)
+		pos := IndexRune(a, r)
+		if pos != tt.i {
+			t.Errorf(`IndexRune(%q, '%c') = %v`, tt.a, r, pos)
+		}
+	}
+}
+
 func BenchmarkIndexByte4K(b *testing.B) { bmIndex(b, IndexByte, 4<<10) }
 
 func BenchmarkIndexByte4M(b *testing.B) { bmIndex(b, IndexByte, 4<<20) }
@@ -336,6 +356,23 @@ func TestFields(t *testing.T) {
 	}
 }
 
+func TestFieldsFunc(t *testing.T) {
+	pred := func(c int) bool { return c == 'X' }
+	var fieldsFuncTests = []FieldsTest{
+		FieldsTest{"", []string{}},
+		FieldsTest{"XX", []string{}},
+		FieldsTest{"XXhiXXX", []string{"hi"}},
+		FieldsTest{"aXXbXXXcX", []string{"a", "b", "c"}},
+	}
+	for _, tt := range fieldsFuncTests {
+		a := FieldsFunc([]byte(tt.s), pred)
+		result := arrayOfString(a)
+		if !eq(result, tt.a) {
+			t.Errorf("FieldsFunc(%q) = %v, want %v", tt.s, a, tt.a)
+		}
+	}
+}
+
 // Test case for any function which accepts and returns a byte array.
 // For ease of creation, we write the byte arrays as strings.
 type StringTest struct {
diff --git a/src/pkg/strings/strings.go b/src/pkg/strings/strings.go
index c332f4567d..89da9dc224 100644
--- a/src/pkg/strings/strings.go
+++ b/src/pkg/strings/strings.go
@@ -191,7 +191,7 @@ func Fields(s string) []string {
 	return FieldsFunc(s, unicode.IsSpace)
 }
 
-// FieldsFunc splits the string s at each run of Unicode code points c satifying f(c)
+// FieldsFunc splits the string s at each run of Unicode code points c satisfying f(c)
 // and returns an array of slices of s. If no code points in s satisfy f(c), an empty slice
 // is returned.
 func FieldsFunc(s string, f func(int) bool) []string {