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casing operations for byte arrays
R=rsc DELTA=186 (181 added, 0 deleted, 5 changed) OCL=34203 CL=34203
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@ -6,7 +6,10 @@
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// Analagous to the facilities of the strings package.
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package bytes
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import "utf8"
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import (
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"unicode";
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"utf8";
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)
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// Compare returns an integer comparing the two byte arrays lexicographically.
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// The result will be 0 if a==b, -1 if a < b, and +1 if a > b
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@ -177,3 +180,83 @@ func HasPrefix(s, prefix []byte) bool {
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func HasSuffix(s, suffix []byte) bool {
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return len(s) >= len(suffix) && Equal(s[len(s)-len(suffix):len(s)], suffix)
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}
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// Map returns a copy of the byte array s with all its characters modified
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// according to the mapping function.
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func Map(mapping func(rune int) int, s []byte) []byte {
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// In the worst case, the array can grow when mapped, making
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// things unpleasant. But it's so rare we barge in assuming it's
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// fine. It could also shrink but that falls out naturally.
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maxbytes := len(s); // length of b
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nbytes := 0; // number of bytes encoded in b
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b := make([]byte, maxbytes);
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for wid, i := 0, 0; i < len(s); i += wid {
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wid = 1;
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rune := int(s[i]);
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if rune < utf8.RuneSelf {
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rune = mapping(rune);
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} else {
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rune, wid = utf8.DecodeRune(s[i:len(s)]);
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}
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rune = mapping(rune);
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if nbytes + utf8.RuneLen(rune) > maxbytes {
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// Grow the buffer.
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maxbytes = maxbytes*2 + utf8.UTFMax;
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nb := make([]byte, maxbytes);
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for i, c := range b[0:nbytes] {
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nb[i] = c
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}
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b = nb;
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}
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nbytes += utf8.EncodeRune(rune, b[nbytes:maxbytes]);
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}
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return b[0:nbytes];
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}
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// ToUpper returns a copy of the byte array s with all Unicode letters mapped to their upper case.
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func ToUpper(s []byte) []byte {
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return Map(unicode.ToUpper, s)
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}
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// ToUpper returns a copy of the byte array s with all Unicode letters mapped to their lower case.
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func ToLower(s []byte) []byte {
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return Map(unicode.ToLower, s)
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}
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// ToTitle returns a copy of the byte array s with all Unicode letters mapped to their title case.
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func Title(s []byte) []byte {
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return Map(unicode.ToTitle, s)
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}
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// Trim returns a slice of the string s, with all leading and trailing white space
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// removed, as defined by Unicode.
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func TrimSpace(s []byte) []byte {
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start, end := 0, len(s);
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for wid := 0; start < end; start += wid {
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wid = 1;
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rune := int(s[start]);
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if rune >= utf8.RuneSelf {
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rune, wid = utf8.DecodeRune(s[start:end])
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}
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if !unicode.IsSpace(rune) {
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break;
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}
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}
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for wid := 0; start < end; end -= wid {
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wid = 1;
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rune := int(s[end-1]);
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if rune >= utf8.RuneSelf {
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// Back up carefully looking for beginning of rune. Mustn't pass start.
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for wid = 2; start <= end-wid && !utf8.RuneStart(s[end-wid]); wid++ {
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}
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if start > end-wid { // invalid UTF-8 sequence; stop processing
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return s[start:end]
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}
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rune, wid = utf8.DecodeRune(s[end-wid:end]);
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}
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if !unicode.IsSpace(rune) {
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break;
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}
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}
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return s[start:end];
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}
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@ -8,6 +8,7 @@ import (
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. "bytes";
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"strings";
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"testing";
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"unicode";
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)
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func eq(a, b []string) bool {
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@ -163,3 +164,100 @@ func TestCopy(t *testing.T) {
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}
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}
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}
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// Test case for any function which accepts and returns a byte array.
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// For ease of creation, we write the byte arrays as strings.
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type StringTest struct {
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in, out string;
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}
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var upperTests = []StringTest {
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StringTest{"", ""},
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StringTest{"abc", "ABC"},
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StringTest{"AbC123", "ABC123"},
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StringTest{"azAZ09_", "AZAZ09_"},
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StringTest{"\u0250\u0250\u0250\u0250\u0250", "\u2C6F\u2C6F\u2C6F\u2C6F\u2C6F"}, // grows one byte per char
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}
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var lowerTests = []StringTest {
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StringTest{"", ""},
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StringTest{"abc", "abc"},
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StringTest{"AbC123", "abc123"},
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StringTest{"azAZ09_", "azaz09_"},
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StringTest{"\u2C6D\u2C6D\u2C6D\u2C6D\u2C6D", "\u0251\u0251\u0251\u0251\u0251"}, // shrinks one byte per char
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}
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const space = "\t\v\r\f\n\u0085\u00a0\u2000\u3000"
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var trimSpaceTests = []StringTest {
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StringTest{"", ""},
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StringTest{"abc", "abc"},
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StringTest{space + "abc" + space, "abc"},
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StringTest{" ", ""},
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StringTest{" \t\r\n \t\t\r\r\n\n ", ""},
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StringTest{" \t\r\n x\t\t\r\r\n\n ", "x"},
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StringTest{" \u2000\t\r\n x\t\t\r\r\ny\n \u3000", "x\t\t\r\r\ny"},
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StringTest{"1 \t\r\n2", "1 \t\r\n2"},
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StringTest{" x\x80", "x\x80"}, // invalid UTF-8 on end
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StringTest{" x\xc0", "x\xc0"}, // invalid UTF-8 on end
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}
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// Bytes returns a new slice containing the bytes in s.
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// Borrowed from strings to avoid dependency.
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func Bytes(s string) []byte {
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b := make([]byte, len(s));
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for i := 0; i < len(s); i++ {
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b[i] = s[i];
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}
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return b;
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}
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// Execute f on each test case. funcName should be the name of f; it's used
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// in failure reports.
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func runStringTests(t *testing.T, f func([]byte) []byte, funcName string, testCases []StringTest) {
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for i, tc := range testCases {
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actual := string(f(Bytes(tc.in)));
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if actual != tc.out {
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t.Errorf("%s(%q) = %q; want %q", funcName, tc.in, actual, tc.out);
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}
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}
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}
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func tenRunes(rune int) string {
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r := make([]int, 10);
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for i := range r {
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r[i] = rune
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}
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return string(r)
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}
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func TestMap(t *testing.T) {
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// Run a couple of awful growth/shrinkage tests
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a := tenRunes('a');
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// 1. Grow. This triggers two reallocations in Map.
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maxRune := func(rune int) int { return unicode.MaxRune };
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m := Map(maxRune, Bytes(a));
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expect := tenRunes(unicode.MaxRune);
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if string(m) != expect {
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t.Errorf("growing: expected %q got %q", expect, m);
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}
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// 2. Shrink
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minRune := func(rune int) int { return 'a' };
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m = Map(minRune, Bytes(tenRunes(unicode.MaxRune)));
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expect = a;
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if string(m) != expect {
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t.Errorf("shrinking: expected %q got %q", expect, m);
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}
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}
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func TestToUpper(t *testing.T) {
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runStringTests(t, ToUpper, "ToUpper", upperTests);
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}
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func TestToLower(t *testing.T) {
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runStringTests(t, ToLower, "ToLower", lowerTests);
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}
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func TestTrimSpace(t *testing.T) {
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runStringTests(t, TrimSpace, "TrimSpace", trimSpaceTests);
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}
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@ -149,7 +149,7 @@ func HasSuffix(s, suffix string) bool {
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}
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// Map returns a copy of the string s with all its characters modified
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// according to mapping function.
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// according to the mapping function.
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func Map(mapping func(rune int) int, s string) string {
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// In the worst case, the string can grow when mapped, making
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// things unpleasant. But it's so rare we barge in assuming it's
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@ -177,17 +177,17 @@ func Map(mapping func(rune int) int, s string) string {
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return string(b[0:nbytes]);
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}
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// ToUpper returns a copy of the string s with all letters mapped to their upper case.
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// ToUpper returns a copy of the string s with all Unicode letters mapped to their upper case.
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func ToUpper(s string) string {
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return Map(unicode.ToUpper, s)
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}
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// ToUpper returns a copy of the string s with all letters mapped to their lower case.
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// ToUpper returns a copy of the string s with all Unicode letters mapped to their lower case.
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func ToLower(s string) string {
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return Map(unicode.ToLower, s)
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}
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// ToTitle returns a copy of the string s with all letters mapped to their title case.
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// ToTitle returns a copy of the string s with all Unicode letters mapped to their title case.
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func Title(s string) string {
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return Map(unicode.ToTitle, s)
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}
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