bytes - The Go Programming Language

MinRead is the minimum slice size passed to a Read call by Buffer.ReadFrom. As long as the Buffer has at least MinRead bytes beyond what is required to hold the contents of r, ReadFrom will not grow the underlying buffer.

Variables

var ErrTooLarge = errors.New("bytes.Buffer: too large")

ErrTooLarge is passed to panic if memory cannot be allocated to store data in a buffer.

func Compare

func Compare(a, b []byte) int

Compare returns an integer comparing the two byte arrays lexicographically. The result will be 0 if a==b, -1 if a < b, and +1 if a > b A nil argument is equivalent to an empty slice.

func Contains

func Contains(b, subslice []byte) bool

Contains returns whether subslice is within b.

func Count

func Count(s, sep []byte) int

Count counts the number of non-overlapping instances of sep in s.

func Equal

func Equal(a, b []byte) bool

Equal returns a boolean reporting whether a == b. A nil argument is equivalent to an empty slice.

func EqualFold

func EqualFold(s, t []byte) bool

EqualFold reports whether s and t, interpreted as UTF-8 strings, are equal under Unicode case-folding.

func Fields

func Fields(s []byte) [][]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 FieldsFunc

func FieldsFunc(s []byte, f func(rune) bool) [][]byte

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 HasPrefix

func HasPrefix(s, prefix []byte) bool

HasPrefix tests whether the byte array s begins with prefix.

func HasSuffix

func HasSuffix(s, suffix []byte) bool

HasSuffix tests whether the byte array s ends with suffix.

func Index

func Index(s, sep []byte) int

Index returns the index of the first instance of sep in s, or -1 if sep is not present in s.

func IndexAny

func IndexAny(s []byte, chars string) int

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 point in common.

func IndexByte

func IndexByte(s []byte, c byte) int

IndexByte returns the index of the first instance of c in s, or -1 if c is not present in s.

func IndexFunc

func IndexFunc(s []byte, f func(r rune) bool) int

IndexFunc interprets s as a sequence of UTF-8-encoded Unicode code points. It returns the byte index in s of the first Unicode code point satisfying f(c), or -1 if none do.

func IndexRune

func IndexRune(s []byte, r rune) int

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 Join

func Join(a [][]byte, sep []byte) []byte

Join concatenates the elements of a to create a single byte array. The separator sep is placed between elements in the resulting array.

func LastIndex

func LastIndex(s, sep []byte) int

LastIndex returns the index of the last instance of sep in s, or -1 if sep is not present in s.

func LastIndexAny

func LastIndexAny(s []byte, chars string) int

LastIndexAny interprets s as a sequence of UTF-8-encoded Unicode code points. It returns the byte index of the last 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 point in common.

func LastIndexFunc

func LastIndexFunc(s []byte, f func(r rune) bool) int

LastIndexFunc interprets s as a sequence of UTF-8-encoded Unicode code points. It returns the byte index in s of the last Unicode code point satisfying f(c), or -1 if none do.

func Map

func Map(mapping func(r rune) rune, s []byte) []byte

Map returns a copy of the byte array s with all its characters modified according to the mapping function. If mapping returns a negative value, the character is dropped from the string with no replacement. The characters in s and the output are interpreted as UTF-8-encoded Unicode code points.

func Repeat

func Repeat(b []byte, count int) []byte

Repeat returns a new byte slice consisting of count copies of b.

func Replace

func Replace(s, old, new []byte, n int) []byte

Replace returns a copy of the slice s with the first n non-overlapping instances of old replaced by new. If n < 0, there is no limit on the number of replacements.

func Runes

func Runes(s []byte) []rune

Runes returns a slice of runes (Unicode code points) equivalent to s.

func Split

func Split(s, sep []byte) [][]byte

Split slices s into all subslices separated by sep and returns a slice of the subslices between those separators. If sep is empty, Split splits after each UTF-8 sequence. It is equivalent to SplitN with a count of -1.

func SplitAfter

func SplitAfter(s, sep []byte) [][]byte

SplitAfter slices s into all subslices after each instance of sep and returns a slice of those subslices. If sep is empty, SplitAfter splits after each UTF-8 sequence. It is equivalent to SplitAfterN with a count of -1.

func SplitAfterN

func SplitAfterN(s, sep []byte, n int) [][]byte

SplitAfterN slices s into subslices after each instance of sep and returns a slice of those subslices. If sep is empty, SplitAfterN splits after each UTF-8 sequence. The count determines the number of subslices to return:

n > 0: at most n subslices; the last subslice will be the unsplit remainder.
n == 0: the result is nil (zero subslices)
n < 0: all subslices

func SplitN

func SplitN(s, sep []byte, n int) [][]byte

SplitN slices s into subslices separated by sep and returns a slice of the subslices between those separators. If sep is empty, SplitN splits after each UTF-8 sequence. The count determines the number of subslices to return:

n > 0: at most n subslices; the last subslice will be the unsplit remainder.
n == 0: the result is nil (zero subslices)
n < 0: all subslices

func Title

func Title(s []byte) []byte

Title returns a copy of s with all Unicode letters that begin words mapped to their title case.

func ToLower

func ToLower(s []byte) []byte

ToUpper returns a copy of the byte array s with all Unicode letters mapped to their lower case.

func ToLowerSpecial

func ToLowerSpecial(_case unicode.SpecialCase, s []byte) []byte

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 ToTitle

func ToTitle(s []byte) []byte

ToTitle returns a copy of the byte array s with all Unicode letters mapped to their title case.

func ToTitleSpecial

func ToTitleSpecial(_case unicode.SpecialCase, s []byte) []byte

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 ToUpper

func ToUpper(s []byte) []byte

ToUpper returns a copy of the byte array s with all Unicode letters mapped to their upper case.

func ToUpperSpecial

func ToUpperSpecial(_case unicode.SpecialCase, s []byte) []byte

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 Trim

func Trim(s []byte, cutset string) []byte

Trim returns a subslice of s by slicing off all leading and trailing UTF-8-encoded Unicode code points contained in cutset.

func TrimFunc

func TrimFunc(s []byte, f func(r rune) bool) []byte

TrimFunc returns a subslice of s by slicing off all leading and trailing UTF-8-encoded Unicode code points c that satisfy f(c).

func TrimLeft

func TrimLeft(s []byte, cutset string) []byte

TrimLeft returns a subslice of s by slicing off all leading UTF-8-encoded Unicode code points contained in cutset.

func TrimLeftFunc

func TrimLeftFunc(s []byte, f func(r rune) bool) []byte

TrimLeftFunc returns a subslice of s by slicing off all leading UTF-8-encoded Unicode code points c that satisfy f(c).

func TrimRight

func TrimRight(s []byte, cutset string) []byte

TrimRight returns a subslice of s by slicing off all trailing UTF-8-encoded Unicode code points that are contained in cutset.

func TrimRightFunc

func TrimRightFunc(s []byte, f func(r rune) bool) []byte

TrimRightFunc returns a subslice of s by slicing off all trailing UTF-8 encoded Unicode code points c that satisfy f(c).

func TrimSpace

func TrimSpace(s []byte) []byte

TrimSpace returns a subslice of s by slicing off all leading and trailing white space, as defined by Unicode.

type Buffer

type Buffer struct {
    // contains filtered or unexported fields
}

A Buffer is a variable-sized buffer of bytes with Read and Write methods. The zero value for Buffer is an empty buffer ready to use.

? Example

Code:

var b Buffer // A Buffer needs no initialization.
b.Write([]byte("Hello "))
b.Write([]byte("world!"))
b.WriteTo(os.Stdout)

Output:

Hello world!

? Example (Reader)

Code:

// A Buffer can turn a string or a []byte into an io.Reader.
buf := NewBufferString("R29waGVycyBydWxlIQ==")
dec := base64.NewDecoder(base64.StdEncoding, buf)
io.Copy(os.Stdout, dec)

Output:

Gophers rule!

func NewBuffer

func NewBuffer(buf []byte) *Buffer

NewBuffer creates and initializes a new Buffer using buf as its initial contents. It is intended to prepare a Buffer to read existing data. It can also be used to size the internal buffer for writing. To do that, buf should have the desired capacity but a length of zero.

In most cases, new(Buffer) (or just declaring a Buffer variable) is sufficient to initialize a Buffer.

func NewBufferString

func NewBufferString(s string) *Buffer

NewBufferString creates and initializes a new Buffer using string s as its initial contents. It is intended to prepare a buffer to read an existing string.

In most cases, new(Buffer) (or just declaring a Buffer variable) is sufficient to initialize a Buffer.

func (*Buffer) Bytes

func (b *Buffer) Bytes() []byte

Bytes returns a slice of the contents of the unread portion of the buffer; len(b.Bytes()) == b.Len(). If the caller changes the contents of the returned slice, the contents of the buffer will change provided there are no intervening method calls on the Buffer.

func (*Buffer) Len

func (b *Buffer) Len() int

Len returns the number of bytes of the unread portion of the buffer; b.Len() == len(b.Bytes()).

func (*Buffer) Next

func (b *Buffer) Next(n int) []byte

Next returns a slice containing the next n bytes from the buffer, advancing the buffer as if the bytes had been returned by Read. If there are fewer than n bytes in the buffer, Next returns the entire buffer. The slice is only valid until the next call to a read or write method.

func (*Buffer) Read

func (b *Buffer) Read(p []byte) (n int, err error)

Read reads the next len(p) bytes from the buffer or until the buffer is drained. The return value n is the number of bytes read. If the buffer has no data to return, err is io.EOF (unless len(p) is zero); otherwise it is nil.

func (*Buffer) ReadByte

func (b *Buffer) ReadByte() (c byte, err error)

ReadByte reads and returns the next byte from the buffer. If no byte is available, it returns error io.EOF.

func (*Buffer) ReadBytes

func (b *Buffer) ReadBytes(delim byte) (line []byte, err error)

ReadBytes reads until the first occurrence of delim in the input, returning a slice containing the data up to and including the delimiter. If ReadBytes encounters an error before finding a delimiter, it returns the data read before the error and the error itself (often io.EOF). ReadBytes returns err != nil if and only if the returned data does not end in delim.

func (*Buffer) ReadFrom

func (b *Buffer) ReadFrom(r io.Reader) (n int64, err error)

ReadFrom reads data from r until EOF and appends it to the buffer. The return value n is the number of bytes read. Any error except io.EOF encountered during the read is also returned. If the buffer becomes too large, ReadFrom will panic with ErrTooLarge.

func (*Buffer) ReadRune

func (b *Buffer) ReadRune() (r rune, size int, err error)

ReadRune reads and returns the next UTF-8-encoded Unicode code point from the buffer. If no bytes are available, the error returned is io.EOF. If the bytes are an erroneous UTF-8 encoding, it consumes one byte and returns U+FFFD, 1.

func (*Buffer) ReadString

func (b *Buffer) ReadString(delim byte) (line string, err error)

ReadString reads until the first occurrence of delim in the input, returning a string containing the data up to and including the delimiter. If ReadString encounters an error before finding a delimiter, it returns the data read before the error and the error itself (often io.EOF). ReadString returns err != nil if and only if the returned data does not end in delim.

func (*Buffer) Reset

func (b *Buffer) Reset()

Reset resets the buffer so it has no content. b.Reset() is the same as b.Truncate(0).

func (*Buffer) String

func (b *Buffer) String() string

String returns the contents of the unread portion of the buffer as a string. If the Buffer is a nil pointer, it returns "<nil>".

func (*Buffer) Truncate

func (b *Buffer) Truncate(n int)

Truncate discards all but the first n unread bytes from the buffer. It panics if n is negative or greater than the length of the buffer.

func (*Buffer) UnreadByte

func (b *Buffer) UnreadByte() error

UnreadByte unreads the last byte returned by the most recent read operation. If write has happened since the last read, UnreadByte returns an error.

func (*Buffer) UnreadRune

func (b *Buffer) UnreadRune() error

UnreadRune unreads the last rune returned by ReadRune. If the most recent read or write operation on the buffer was not a ReadRune, UnreadRune returns an error. (In this regard it is stricter than UnreadByte, which will unread the last byte from any read operation.)

func (*Buffer) Write

func (b *Buffer) Write(p []byte) (n int, err error)

Write appends the contents of p to the buffer. The return value n is the length of p; err is always nil. If the buffer becomes too large, Write will panic with ErrTooLarge.

func (*Buffer) WriteByte

func (b *Buffer) WriteByte(c byte) error

WriteByte appends the byte c to the buffer. The returned error is always nil, but is included to match bufio.Writer's WriteByte. If the buffer becomes too large, WriteByte will panic with ErrTooLarge.

func (*Buffer) WriteRune

func (b *Buffer) WriteRune(r rune) (n int, err error)

WriteRune appends the UTF-8 encoding of Unicode code point r to the buffer, returning its length and an error, which is always nil but is included to match bufio.Writer's WriteRune. If the buffer becomes too large, WriteRune will panic with ErrTooLarge.

func (*Buffer) WriteString

func (b *Buffer) WriteString(s string) (n int, err error)

WriteString appends the contents of s to the buffer. The return value n is the length of s; err is always nil. If the buffer becomes too large, WriteString will panic with ErrTooLarge.

func (*Buffer) WriteTo

func (b *Buffer) WriteTo(w io.Writer) (n int64, err error)

WriteTo writes data to w until the buffer is drained or an error occurs. The return value n is the number of bytes written; it always fits into an int, but it is int64 to match the io.WriterTo interface. Any error encountered during the write is also returned.

type Reader

type Reader struct {
    // contains filtered or unexported fields
}

A Reader implements the io.Reader, io.ReaderAt, io.Seeker, io.ByteScanner, and io.RuneScanner interfaces by reading from a byte slice. Unlike a Buffer, a Reader is read-only and supports seeking.

func NewReader

func NewReader(b []byte) *Reader

NewReader returns a new Reader reading from b.

func (*Reader) Len

func (r *Reader) Len() int

Len returns the number of bytes of the unread portion of the slice.

func (*Reader) Read

func (r *Reader) Read(b []byte) (n int, err error)

func (*Reader) ReadAt

func (r *Reader) ReadAt(b []byte, off int64) (n int, err error)

func (*Reader) ReadByte

func (r *Reader) ReadByte() (b byte, err error)

func (*Reader) ReadRune

func (r *Reader) ReadRune() (ch rune, size int, err error)

func (*Reader) Seek

func (r *Reader) Seek(offset int64, whence int) (int64, error)

Seek implements the io.Seeker interface.

func (*Reader) UnreadByte

func (r *Reader) UnreadByte() error

func (*Reader) UnreadRune

func (r *Reader) UnreadRune() error

Bugs

The rule Title uses for word boundaries does not handle Unicode punctuation properly.

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