package utf8

Import Path
	unicode/utf8 (on golang.org and go.dev)

Dependency Relation
	imports 0 packages, and imported by 46 packages

Involved Source Files Package utf8 implements functions and constants to support text encoded in UTF-8. It includes functions to translate between runes and UTF-8 byte sequences. See https://en.wikipedia.org/wiki/UTF-8
Code Examples package main import ( "fmt" "unicode/utf8" ) func main() { b := []byte("Hello, 世界") for len(b) > 0 { r, size := utf8.DecodeLastRune(b) fmt.Printf("%c %v\n", r, size) b = b[:len(b)-size] } } package main import ( "fmt" "unicode/utf8" ) func main() { str := "Hello, 世界" for len(str) > 0 { r, size := utf8.DecodeLastRuneInString(str) fmt.Printf("%c %v\n", r, size) str = str[:len(str)-size] } } package main import ( "fmt" "unicode/utf8" ) func main() { b := []byte("Hello, 世界") for len(b) > 0 { r, size := utf8.DecodeRune(b) fmt.Printf("%c %v\n", r, size) b = b[size:] } } package main import ( "fmt" "unicode/utf8" ) func main() { str := "Hello, 世界" for len(str) > 0 { r, size := utf8.DecodeRuneInString(str) fmt.Printf("%c %v\n", r, size) str = str[size:] } } package main import ( "fmt" "unicode/utf8" ) func main() { r := '世' buf := make([]byte, 3) n := utf8.EncodeRune(buf, r) fmt.Println(buf) fmt.Println(n) } package main import ( "fmt" "unicode/utf8" ) func main() { runes := []rune{ // Less than 0, out of range. -1, // Greater than 0x10FFFF, out of range. 0x110000, // The Unicode replacement character. utf8.RuneError, } for i, c := range runes { buf := make([]byte, 3) size := utf8.EncodeRune(buf, c) fmt.Printf("%d: %d %[2]s %d\n", i, buf, size) } } package main import ( "fmt" "unicode/utf8" ) func main() { buf := []byte{228, 184, 150} // 世 fmt.Println(utf8.FullRune(buf)) fmt.Println(utf8.FullRune(buf[:2])) } package main import ( "fmt" "unicode/utf8" ) func main() { str := "世" fmt.Println(utf8.FullRuneInString(str)) fmt.Println(utf8.FullRuneInString(str[:2])) } package main import ( "fmt" "unicode/utf8" ) func main() { buf := []byte("Hello, 世界") fmt.Println("bytes =", len(buf)) fmt.Println("runes =", utf8.RuneCount(buf)) } package main import ( "fmt" "unicode/utf8" ) func main() { str := "Hello, 世界" fmt.Println("bytes =", len(str)) fmt.Println("runes =", utf8.RuneCountInString(str)) } package main import ( "fmt" "unicode/utf8" ) func main() { fmt.Println(utf8.RuneLen('a')) fmt.Println(utf8.RuneLen('界')) } package main import ( "fmt" "unicode/utf8" ) func main() { buf := []byte("a界") fmt.Println(utf8.RuneStart(buf[0])) fmt.Println(utf8.RuneStart(buf[1])) fmt.Println(utf8.RuneStart(buf[2])) } package main import ( "fmt" "unicode/utf8" ) func main() { valid := []byte("Hello, 世界") invalid := []byte{0xff, 0xfe, 0xfd} fmt.Println(utf8.Valid(valid)) fmt.Println(utf8.Valid(invalid)) } package main import ( "fmt" "unicode/utf8" ) func main() { valid := 'a' invalid := rune(0xfffffff) fmt.Println(utf8.ValidRune(valid)) fmt.Println(utf8.ValidRune(invalid)) } package main import ( "fmt" "unicode/utf8" ) func main() { valid := "Hello, 世界" invalid := string([]byte{0xff, 0xfe, 0xfd}) fmt.Println(utf8.ValidString(valid)) fmt.Println(utf8.ValidString(invalid)) }
Package-Level Functions (total 14)
DecodeLastRune unpacks the last UTF-8 encoding in p and returns the rune and its width in bytes. If p is empty it returns (RuneError, 0). Otherwise, if the encoding is invalid, it returns (RuneError, 1). Both are impossible results for correct, non-empty UTF-8. An encoding is invalid if it is incorrect UTF-8, encodes a rune that is out of range, or is not the shortest possible UTF-8 encoding for the value. No other validation is performed.
DecodeLastRuneInString is like DecodeLastRune but its input is a string. If s is empty it returns (RuneError, 0). Otherwise, if the encoding is invalid, it returns (RuneError, 1). Both are impossible results for correct, non-empty UTF-8. An encoding is invalid if it is incorrect UTF-8, encodes a rune that is out of range, or is not the shortest possible UTF-8 encoding for the value. No other validation is performed.
DecodeRune unpacks the first UTF-8 encoding in p and returns the rune and its width in bytes. If p is empty it returns (RuneError, 0). Otherwise, if the encoding is invalid, it returns (RuneError, 1). Both are impossible results for correct, non-empty UTF-8. An encoding is invalid if it is incorrect UTF-8, encodes a rune that is out of range, or is not the shortest possible UTF-8 encoding for the value. No other validation is performed.
DecodeRuneInString is like DecodeRune but its input is a string. If s is empty it returns (RuneError, 0). Otherwise, if the encoding is invalid, it returns (RuneError, 1). Both are impossible results for correct, non-empty UTF-8. An encoding is invalid if it is incorrect UTF-8, encodes a rune that is out of range, or is not the shortest possible UTF-8 encoding for the value. No other validation is performed.
EncodeRune writes into p (which must be large enough) the UTF-8 encoding of the rune. If the rune is out of range, it writes the encoding of RuneError. It returns the number of bytes written.
FullRune reports whether the bytes in p begin with a full UTF-8 encoding of a rune. An invalid encoding is considered a full Rune since it will convert as a width-1 error rune.
FullRuneInString is like FullRune but its input is a string.
RuneCount returns the number of runes in p. Erroneous and short encodings are treated as single runes of width 1 byte.
RuneCountInString is like RuneCount but its input is a string.
RuneLen returns the number of bytes required to encode the rune. It returns -1 if the rune is not a valid value to encode in UTF-8.
RuneStart reports whether the byte could be the first byte of an encoded, possibly invalid rune. Second and subsequent bytes always have the top two bits set to 10.
Valid reports whether p consists entirely of valid UTF-8-encoded runes.
ValidRune reports whether r can be legally encoded as UTF-8. Code points that are out of range or a surrogate half are illegal.
ValidString reports whether s consists entirely of valid UTF-8-encoded runes.
Package-Level Constants (total 4)
Numbers fundamental to the encoding.
Numbers fundamental to the encoding.
Numbers fundamental to the encoding.
Numbers fundamental to the encoding.