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std/unicode/utf8 ​

Index ​

Variables
fn FullRune(p: []byte): bool
fn FullRuneString(s: string): bool
fn DecodeRune(p: []byte): (r: rune, size: int)
fn DecodeRuneString(s: string): (r: rune, size: int)
fn DecodeLastRune(p: []byte): (r: rune, size: int)
fn DecodeLastRuneString(s: string): (r: rune, size: int)
fn RuneLen(r: rune): int
fn EncodeRune(mut p: []byte, mut r: rune): int
fn AppendRune(mut p: []byte, r: rune): []byte
fn RuneCount(p: []byte): (n: int)
fn RuneCountString(s: string): (n: int)
fn RuneStart(b: byte): bool
fn Valid(p: []byte): bool
fn ValidString(mut s: string): bool
fn ValidRune(r: rune): bool

Variables ​

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const (
	RuneError = '\uFFFD'     // The "error" rune or "Unicode replacement character"
	RuneSelf  = 0x80         // Characters below RuneSelf are represented as themselves in a single byte.
	MaxRune   = '\U0010FFFF' // Maximum valid Unicode code point.
	UTFMax    = 4            // Maximum number of bytes of a UTF-8 encoded Unicode character.
)

Numbers fundamental to the encoding.

FullRune ​

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fn FullRune(p: []byte): bool

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.

FullRuneString ​

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fn FullRuneString(s: string): bool

Like FullRune but its input is a string.

DecodeRune ​

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fn DecodeRune(p: []byte): (r: rune, size: int)

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.

DecodeRuneString ​

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fn DecodeRuneString(s: string): (r: rune, size: int)

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.

DecodeLastRune ​

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fn DecodeLastRune(p: []byte): (r: rune, size: int)

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.

DecodeLastRuneString ​

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fn DecodeLastRuneString(s: string): (r: rune, size: int)

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.

RuneLen ​

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fn RuneLen(r: rune): int

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.

EncodeRune ​

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fn EncodeRune(mut p: []byte, mut r: rune): int

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.

AppendRune ​

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fn AppendRune(mut p: []byte, r: rune): []byte

Appends the UTF-8 encoding of r to the end of p and returns the extended buffer. If the rune is out of range, it appends the encoding of RuneError.

RuneCount ​

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fn RuneCount(p: []byte): (n: int)

Returns the number of runes in p. Erroneous and short encodings are treated as single runes of width 1 byte.

RuneCountString ​

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fn RuneCountString(s: string): (n: int)

Like RuneCount but its input is a string.

RuneStart ​

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fn RuneStart(b: byte): bool

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 ​

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fn Valid(p: []byte): bool

Reports whether p consists entirely of valid UTF-8-encoded runes.

ValidString ​

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fn ValidString(mut s: string): bool

Reports whether s consists entirely of valid UTF-8-encoded runes.

ValidRune ​

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fn ValidRune(r: rune): bool

Reports whether r can be legally encoded as UTF-8. Code points that are out of range or a surrogate half are illegal.