bytes

package
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 Go to latest Published: Dec 19, 2015 License: BSD-3-Clause Imports: 4 Imported by: 0

Documentation

Overview

Package bytes implements functions for the manipulation of byte slices. It is analogous to the facilities of the strings package.

Index

Examples

Constants

View Source 
const MinRead = 512

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

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

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

Functions

func Compare 

func Compare(a, b []byte) int

Compare returns an integer comparing two byte slices 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.

Example 
package main

import (
	"bytes"
)

func main() {
	// Interpret Compare's result by comparing it to zero.
	var a, b []byte
	if bytes.Compare(a, b) < 0 {
		// a less b
	}
	if bytes.Compare(a, b) <= 0 {
		// a less or equal b
	}
	if bytes.Compare(a, b) > 0 {
		// a greater b
	}
	if bytes.Compare(a, b) >= 0 {
		// a greater or equal b
	}

	// Prefer Equal to Compare for equality comparisons.
	if bytes.Equal(a, b) {
		// a equal b
	}
	if !bytes.Equal(a, b) {
		// a not equal b
	}
}

Output:

func Contains 

func Contains(b, subslice []byte) bool

Contains reports 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. If sep is an empty slice, Count returns 1 + the number of Unicode code points in s.

func Equal 

func Equal(a, b []byte) bool

Equal returns a boolean reporting whether a and b are the same length and contain the same bytes. 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 slice s around each instance of one or more consecutive white space characters, returning a slice of subslices 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 slice s at each run of code points c satisfying f(c) and returns a slice of subslices of s. If all code points in s satisfy f(c), or len(s) == 0, an empty slice is returned. FieldsFunc makes no guarantees about the order in which it calls f(c). If f does not return consistent results for a given c, FieldsFunc may crash.

func HasPrefix 

func HasPrefix(s, prefix []byte) bool

HasPrefix tests whether the byte slice s begins with prefix.

func HasSuffix 

func HasSuffix(s, suffix []byte) bool

HasSuffix tests whether the byte slice 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(s [][]byte, sep []byte) []byte

Join concatenates the elements of s to create a new byte slice. The separator sep is placed between elements in the resulting slice.

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 LastIndexByte 

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

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

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 slice 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 old is empty, it matches at the beginning of the slice and after each UTF-8 sequence, yielding up to k+1 replacements for a k-rune slice. 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.

BUG(rsc): The rule Title uses for word boundaries does not handle Unicode punctuation properly.

func ToLower 

func ToLower(s []byte) []byte

ToLower returns a copy of the byte slice 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 slice 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 slice 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 slice 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 slice 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 slice 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 TrimPrefix 

func TrimPrefix(s, prefix []byte) []byte

TrimPrefix returns s without the provided leading prefix string. If s doesn't start with prefix, s is returned unchanged.

Example 
package main

import (
	"bytes"
	"fmt"
)

func main() {
	var b = []byte("Goodbye,, world!")
	b = bytes.TrimPrefix(b, []byte("Goodbye,"))
	b = bytes.TrimPrefix(b, []byte("See ya,"))
	fmt.Printf("Hello%s", b)
}

Output:

Hello, world!

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.

func TrimSuffix 

func TrimSuffix(s, suffix []byte) []byte

TrimSuffix returns s without the provided trailing suffix string. If s doesn't end with suffix, s is returned unchanged.

Example 
package main

import (
	"bytes"
	"os"
)

func main() {
	var b = []byte("Hello, goodbye, etc!")
	b = bytes.TrimSuffix(b, []byte("goodbye, etc!"))
	b = bytes.TrimSuffix(b, []byte("gopher"))
	b = append(b, bytes.TrimSuffix([]byte("world!"), []byte("x!"))...)
	os.Stdout.Write(b)
}

Output:

Hello, world!

Types

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 
package main

import (
	"bytes"
	"fmt"
	"os"
)

func main() {
	var b bytes.Buffer // A Buffer needs no initialization.
	b.Write([]byte("Hello "))
	fmt.Fprintf(&b, "world!")
	b.WriteTo(os.Stdout)
}

Output:

Hello world!
Example (Reader) 
package main

import (
	"bytes"
	"encoding/base64"
	"io"
	"os"
)

func main() {
	// A Buffer can turn a string or a []byte into an io.Reader.
	buf := bytes.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 length b.Len() holding the unread portion of the buffer. The slice is valid for use only until the next buffer modification (that is, only until the next call to a method like Read, Write, Reset, or Truncate). The slice aliases the buffer content at least until the next buffer modification, so immediate changes to the slice will affect the result of future reads.

func (*Buffer) Cap 

func (b *Buffer) Cap() int

Cap returns the capacity of the buffer's underlying byte slice, that is, the total space allocated for the buffer's data.

func (*Buffer) Grow 

func (b *Buffer) Grow(n int)

Grow grows the buffer's capacity, if necessary, to guarantee space for another n bytes. After Grow(n), at least n bytes can be written to the buffer without another allocation. If n is negative, Grow will panic. If the buffer can't grow it will panic with ErrTooLarge.

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, growing the buffer as needed. 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 to be empty, but it retains the underlying storage for use by future writes. Reset is the same as 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 but continues to use the same allocated storage. 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, growing the buffer as needed. 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, growing the buffer as needed. 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. The buffer is grown as needed; if it 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, growing the buffer as needed. 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.WriterTo, 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) Size 

func (r *Reader) Size() int64

Size returns the original length of the underlying byte slice. Size is the number of bytes available for reading via ReadAt. The returned value is always the same and is not affected by calls to any other method.

func (*Reader) UnreadByte 

func (r *Reader) UnreadByte() error

func (*Reader) UnreadRune 

func (r *Reader) UnreadRune() error

func (*Reader) WriteTo 

func (r *Reader) WriteTo(w io.Writer) (n int64, err error)

WriteTo implements the io.WriterTo interface.

Notes

Bugs

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

Source Files

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