bytes
import "bytes"
Package bytes implements functions for the manipulation of byte slices. It is analogous to the facilities of the [strings] package.
Go 1.26.1
Constants
const MinRead = 512
MinRead is the minimum slice size passed to a [Buffer.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, [Buffer.ReadFrom] will not grow the underlying buffer.
bytes/buffer.go:218
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.
bytes/buffer.go:50
Functions
func Clone(b []byte) []byte
Clone returns a copy of b[:len(b)]. The result may have additional unused capacity. Clone(nil) returns nil.
bytes/bytes.go:1384
func Compare(a []byte, 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.
bytes/bytes.go:28
func Contains(b []byte, subslice []byte) bool
Contains reports whether subslice is within b.
bytes/bytes.go:77
func ContainsAny(b []byte, chars string) bool
ContainsAny reports whether any of the UTF-8-encoded code points in chars are within b.
bytes/bytes.go:82
func ContainsFunc(b []byte, f func(...)) bool
ContainsFunc reports whether any of the UTF-8-encoded code points r within b satisfy f(r).
bytes/bytes.go:92
func ContainsRune(b []byte, r rune) bool
ContainsRune reports whether the rune is contained in the UTF-8-encoded byte slice b.
bytes/bytes.go:87
func Count(s []byte, 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 UTF-8-encoded code points in s.
bytes/bytes.go:57
func Cut(s []byte, sep []byte) ([]byte, bool)
Cut slices s around the first instance of sep, returning the text before and after sep. The found result reports whether sep appears in s. If sep does not appear in s, cut returns s, nil, false. Cut returns slices of the original slice s, not copies.
bytes/bytes.go:1374
func CutPrefix(s []byte, prefix []byte) ([]byte, bool)
CutPrefix returns s without the provided leading prefix byte slice and reports whether it found the prefix. If s doesn't start with prefix, CutPrefix returns s, false. If prefix is the empty byte slice, CutPrefix returns s, true. CutPrefix returns slices of the original slice s, not copies.
bytes/bytes.go:1397
func CutSuffix(s []byte, suffix []byte) ([]byte, bool)
CutSuffix returns s without the provided ending suffix byte slice and reports whether it found the suffix. If s doesn't end with suffix, CutSuffix returns s, false. If suffix is the empty byte slice, CutSuffix returns s, true. CutSuffix returns slices of the original slice s, not copies.
bytes/bytes.go:1410
func Equal(a []byte, b []byte) bool
Equal reports whether a and b are the same length and contain the same bytes. A nil argument is equivalent to an empty slice.
bytes/bytes.go:20
func EqualFold(s []byte, t []byte) bool
EqualFold reports whether s and t, interpreted as UTF-8 strings, are equal under simple Unicode case-folding, which is a more general form of case-insensitivity.
bytes/bytes.go:1206
func Fields(s []byte) [][]byte
Fields interprets s as a sequence of UTF-8-encoded code points. It splits the slice s around each instance of one or more consecutive white space characters, as defined by [unicode.IsSpace], returning a slice of subslices of s or an empty slice if s contains only white space. Every element of the returned slice is non-empty. Unlike [Split], leading and trailing runs of white space characters are discarded.
bytes/bytes.go:457
func FieldsFunc(s []byte, f func(...)) [][]byte
FieldsFunc interprets s as a sequence of UTF-8-encoded 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. Every element of the returned slice is non-empty. Unlike [Split], leading and trailing runs of code points satisfying f(c) are discarded. FieldsFunc makes no guarantees about the order in which it calls f(c) and assumes that f always return...
bytes/bytes.go:516
func FieldsFuncSeq(s []byte, f func(...)) interface{}FieldsFuncSeq returns an iterator over subslices of s split around runs of Unicode code points satisfying f(c). The iterator yields the same subslices that would be returned by [FieldsFunc](s), but without constructing a new slice containing the subslices.
bytes/iter.go:116
func FieldsSeq(s []byte) interface{}FieldsSeq returns an iterator over subslices of s split around runs of whitespace characters, as defined by [unicode.IsSpace]. The iterator yields the same subslices that would be returned by [Fields](s), but without constructing a new slice containing the subslices.
bytes/iter.go:83
func HasPrefix(s []byte, prefix []byte) bool
HasPrefix reports whether the byte slice s begins with prefix.
bytes/bytes.go:594
func HasSuffix(s []byte, suffix []byte) bool
HasSuffix reports whether the byte slice s ends with suffix.
bytes/bytes.go:599
func Index(s []byte, sep []byte) int
Index returns the index of the first instance of sep in s, or -1 if sep is not present in s.
bytes/bytes.go:1281
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.
bytes/bytes.go:221
func IndexByte(b []byte, c byte) int
IndexByte returns the index of the first instance of c in b, or -1 if c is not present in b.
bytes/bytes.go:97
func IndexFunc(s []byte, f func(...)) int
IndexFunc interprets s as a sequence of UTF-8-encoded code points. It returns the byte index in s of the first Unicode code point satisfying f(c), or -1 if none do.
bytes/bytes.go:895
func IndexRune(s []byte, r rune) int
IndexRune interprets s as a sequence of UTF-8-encoded 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. If r is [utf8.RuneError], it returns the first instance of any invalid UTF-8 byte sequence.
bytes/bytes.go:139
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.
bytes/bytes.go:561
func LastIndex(s []byte, sep []byte) int
LastIndex returns the index of the last instance of sep in s, or -1 if sep is not present in s.
bytes/bytes.go:111
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.
bytes/bytes.go:299
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.
bytes/bytes.go:130
func LastIndexFunc(s []byte, f func(...)) int
LastIndexFunc interprets s as a sequence of UTF-8-encoded code points. It returns the byte index in s of the last Unicode code point satisfying f(c), or -1 if none do.
bytes/bytes.go:902
func Lines(s []byte) interface{}Lines returns an iterator over the newline-terminated lines in the byte slice s. The lines yielded by the iterator include their terminating newlines. If s is empty, the iterator yields no lines at all. If s does not end in a newline, the final yielded line will not end in a newline. It returns a single-use iterator.
bytes/iter.go:18
func Map(mapping func(...), 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 byte slice with no replacement. The characters in s and the output are interpreted as UTF-8-encoded code points.
bytes/bytes.go:607
func NewBuffer(buf []byte) *Buffer
NewBuffer creates and initializes a new [Buffer] using buf as its initial contents. The new [Buffer] takes ownership of buf, and the caller should not use buf after this call. NewBuffer is intended to prepare a [Buffer] to read existing data. It can also be used to set the initial size of 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 [Bu...
bytes/buffer.go:490
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].
bytes/buffer.go:498
func NewReader(b []byte) *Reader
NewReader returns a new [Reader] reading from b.
bytes/reader.go:159
func Repeat(b []byte, count int) []byte
Repeat returns a new byte slice consisting of count copies of b. It panics if count is negative or if the result of (len(b) * count) overflows.
bytes/bytes.go:639
func Replace(s []byte, old []byte, 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.
bytes/bytes.go:1155
func ReplaceAll(s []byte, old []byte, new []byte) []byte
ReplaceAll returns a copy of the slice s with all 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.
bytes/bytes.go:1199
func Runes(s []byte) []rune
Runes interprets s as a sequence of UTF-8-encoded code points. It returns a slice of runes (Unicode code points) equivalent to s.
bytes/bytes.go:1137
func Split(s []byte, 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. To split around the first instance of a separator, see [Cut].
bytes/bytes.go:439
func SplitAfter(s []byte, 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.
bytes/bytes.go:445
func SplitAfterN(s []byte, 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.
bytes/bytes.go:429
func SplitAfterSeq(s []byte, sep []byte) interface{}SplitAfterSeq returns an iterator over subslices of s split after each instance of sep. The iterator yields the same subslices that would be returned by [SplitAfter](s, sep), but without constructing a new slice containing the subslices. It returns a single-use iterator.
bytes/iter.go:75
func SplitN(s []byte, 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. To split around the first instance of a separator, see [Cut].
bytes/bytes.go:420
func SplitSeq(s []byte, sep []byte) interface{}SplitSeq returns an iterator over all subslices of s separated by sep. The iterator yields the same subslices that would be returned by [Split](s, sep), but without constructing a new slice containing the subslices. It returns a single-use iterator.
bytes/iter.go:67
func Title(s []byte) []byte
Title treats s as UTF-8-encoded bytes and returns a copy with all Unicode letters that begin words mapped to their title case. Deprecated: The rule Title uses for word boundaries does not handle Unicode punctuation properly. Use golang.org/x/text/cases instead.
bytes/bytes.go:828
func ToLower(s []byte) []byte
ToLower returns a copy of the byte slice s with all Unicode letters mapped to their lower case.
bytes/bytes.go:720
func ToLowerSpecial(c unicode.SpecialCase, s []byte) []byte
ToLowerSpecial treats s as UTF-8-encoded bytes and returns a copy with all the Unicode letters mapped to their lower case, giving priority to the special casing rules.
bytes/bytes.go:759
func ToTitle(s []byte) []byte
ToTitle treats s as UTF-8-encoded bytes and returns a copy with all the Unicode letters mapped to their title case.
bytes/bytes.go:749
func ToTitleSpecial(c unicode.SpecialCase, s []byte) []byte
ToTitleSpecial treats s as UTF-8-encoded bytes and returns a copy with all the Unicode letters mapped to their title case, giving priority to the special casing rules.
bytes/bytes.go:765
func ToUpper(s []byte) []byte
ToUpper returns a copy of the byte slice s with all Unicode letters mapped to their upper case.
bytes/bytes.go:689
func ToUpperSpecial(c unicode.SpecialCase, s []byte) []byte
ToUpperSpecial treats s as UTF-8-encoded bytes and returns a copy with all the Unicode letters mapped to their upper case, giving priority to the special casing rules.
bytes/bytes.go:753
func ToValidUTF8(s []byte, replacement []byte) []byte
ToValidUTF8 treats s as UTF-8-encoded bytes and returns a copy with each run of bytes representing invalid UTF-8 replaced with the bytes in replacement, which may be empty.
bytes/bytes.go:771
func Trim(s []byte, cutset string) []byte
Trim returns a subslice of s by slicing off all leading and trailing UTF-8-encoded code points contained in cutset.
bytes/bytes.go:980
func TrimFunc(s []byte, f func(...)) []byte
TrimFunc returns a subslice of s by slicing off all leading and trailing UTF-8-encoded code points c that satisfy f(c).
bytes/bytes.go:870
func TrimLeft(s []byte, cutset string) []byte
TrimLeft returns a subslice of s by slicing off all leading UTF-8-encoded code points contained in cutset.
bytes/bytes.go:999
func TrimLeftFunc(s []byte, f func(...)) []byte
TrimLeftFunc treats s as UTF-8-encoded bytes and returns a subslice of s by slicing off all leading UTF-8-encoded code points c that satisfy f(c).
bytes/bytes.go:847
func TrimPrefix(s []byte, prefix []byte) []byte
TrimPrefix returns s without the provided leading prefix string. If s doesn't start with prefix, s is returned unchanged.
bytes/bytes.go:876
func TrimRight(s []byte, cutset string) []byte
TrimRight returns a subslice of s by slicing off all trailing UTF-8-encoded code points that are contained in cutset.
bytes/bytes.go:1058
func TrimRightFunc(s []byte, f func(...)) []byte
TrimRightFunc returns a subslice of s by slicing off all trailing UTF-8-encoded code points c that satisfy f(c).
bytes/bytes.go:857
func TrimSpace(s []byte) []byte
TrimSpace returns a subslice of s by slicing off all leading and trailing white space, as defined by Unicode.
bytes/bytes.go:1104
func TrimSuffix(s []byte, suffix []byte) []byte
TrimSuffix returns s without the provided trailing suffix string. If s doesn't end with suffix, s is returned unchanged.
bytes/bytes.go:885
Types
type Buffer struct {
// contains filtered or unexported fields
}A Buffer is a variable-sized buffer of bytes with [Buffer.Read] and [Buffer.Write] methods. The zero value for Buffer is an empty buffer ready to use.
bytes/buffer.go:20
func (b *Buffer) Available() int
Available returns how many bytes are unused in the buffer.
bytes/buffer.go:104
func (b *Buffer) AvailableBuffer() []byte
AvailableBuffer returns an empty buffer with b.Available() capacity. This buffer is intended to be appended to and passed to an immediately succeeding [Buffer.Write] call. The buffer is only valid until the next write operation on b.
bytes/buffer.go:66
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 [Buffer.Read], [Buffer.Write], [Buffer.Reset], or [Buffer.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.
bytes/buffer.go:60
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.
bytes/buffer.go:101
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].
bytes/buffer.go:182
func (b *Buffer) Len() int
Len returns the number of bytes of the unread portion of the buffer; b.Len() == len(b.Bytes()).
bytes/buffer.go:97
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 [Buffer.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.
bytes/buffer.go:358
func (b *Buffer) Peek(n int) ([]byte, error)
Peek returns the next n bytes without advancing the buffer. If Peek returns fewer than n bytes, it also returns [io.EOF]. The slice is only valid until the next call to a read or write method. 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.
bytes/buffer.go:85
func (b *Buffer) Read(p []byte) (int, 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.
bytes/buffer.go:336
func (b *Buffer) ReadByte() (byte, error)
ReadByte reads and returns the next byte from the buffer. If no byte is available, it returns error [io.EOF].
bytes/buffer.go:374
func (b *Buffer) ReadBytes(delim byte) ([]byte, 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.
bytes/buffer.go:448
func (b *Buffer) ReadFrom(r io.Reader) (int64, 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].
bytes/buffer.go:224
func (b *Buffer) ReadRune() (rune, int, 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.
bytes/buffer.go:391
func (b *Buffer) ReadString(delim byte) (string, 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.
bytes/buffer.go:476
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 [Buffer.Truncate](0).
bytes/buffer.go:124
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>". To build strings more efficiently, see the [strings.Builder] type.
bytes/buffer.go:72
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.
bytes/buffer.go:109
func (b *Buffer) UnreadByte() error
UnreadByte unreads the last byte returned by the most recent successful read operation that read at least one byte. If a write has happened since the last read, if the last read returned an error, or if the read read zero bytes, UnreadByte returns an error.
bytes/buffer.go:431
func (b *Buffer) UnreadRune() error
UnreadRune unreads the last rune returned by [Buffer.ReadRune]. If the most recent read or write operation on the buffer was not a successful [Buffer.ReadRune], UnreadRune returns an error. (In this regard it is stricter than [Buffer.UnreadByte], which will unread the last byte from any read operation.)
bytes/buffer.go:414
func (b *Buffer) Write(p []byte) (int, 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].
bytes/buffer.go:193
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].
bytes/buffer.go:303
func (b *Buffer) WriteRune(r rune) (int, 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].
bytes/buffer.go:317
func (b *Buffer) WriteString(s string) (int, 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].
bytes/buffer.go:205
func (b *Buffer) WriteTo(w io.Writer) (int64, 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.
bytes/buffer.go:276
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. The zero value for Reader operates like a Reader of an empty slice.
bytes/reader.go:18
func (r *Reader) Len() int
Len returns the number of bytes of the unread portion of the slice.
bytes/reader.go:26
func (r *Reader) Read(b []byte) (int, error)
Read implements the [io.Reader] interface.
bytes/reader.go:39
func (r *Reader) ReadAt(b []byte, off int64) (int, error)
ReadAt implements the [io.ReaderAt] interface.
bytes/reader.go:50
func (r *Reader) ReadByte() (byte, error)
ReadByte implements the [io.ByteReader] interface.
bytes/reader.go:66
func (r *Reader) ReadRune() (rune, int, error)
ReadRune implements the [io.RuneReader] interface.
bytes/reader.go:87
func (r *Reader) Reset(b []byte)
Reset resets the [Reader] to be reading from b.
bytes/reader.go:156
func (r *Reader) Seek(offset int64, whence int) (int64, error)
Seek implements the [io.Seeker] interface.
bytes/reader.go:116
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 [Reader.ReadAt]. The result is unaffected by any method calls except [Reader.Reset].
bytes/reader.go:36
func (r *Reader) UnreadByte() error
UnreadByte complements [Reader.ReadByte] in implementing the [io.ByteScanner] interface.
bytes/reader.go:77
func (r *Reader) UnreadRune() error
UnreadRune complements [Reader.ReadRune] in implementing the [io.RuneScanner] interface.
bytes/reader.go:103
func (r *Reader) WriteTo(w io.Writer) (int64, error)
WriteTo implements the [io.WriterTo] interface.
bytes/reader.go:137