bits

package
v0.48.0 Latest Latest
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 Go to latest Published: Mar 28, 2025 License: MIT, MIT Imports: 4 Imported by: 14

Documentation

Overview

Package bits provides bit and bytes reading and writing including Golomb codes and EBSP as used by MPEG video standards. All readers and writers accumulate errors in the sense that they will stop reading or writing at the first error. The first error, if any, can be retrieved with an AccError() method.

EBSP (Encapsulated Byte Sequence Packets) uses insertion of start-code emulation prevention bytes 0x03 and is used in MPEG video standards from AVC (H.264) and forward. The main types are:

Index

Constants

This section is empty.

Variables

View Source 
var (
	ErrNotReadSeeker = errors.New("reader does not support Seek")
)

ESBPReader errors

View Source 
var (
	ErrSliceRead = fmt.Errorf("read too far in SliceReader")
)

SliceReader errors

View Source 
var ErrSliceWrite = errors.New("overflow in SliceWriter")

Functions

func CeilLog2 added in v0.35.0 

func CeilLog2(n uint) int

CeilLog2 returns nr bits needed to represent numbers 0 - n-1.

func Mask added in v0.43.0 

func Mask(n int) uint

Mask returns a binary mask for the n least significant bits.

Types

type ByteWriter added in v0.43.0 

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

ByteWriter - writer that wraps an io.Writer and accumulates error. Only the first error is saved, but any later calls will not panic.

func NewByteWriter added in v0.43.0 

func NewByteWriter(w io.Writer) *ByteWriter

NewByteWriter creates accumulated error writer around io.Writer.

func (*ByteWriter) AccError added in v0.43.0 

func (a *ByteWriter) AccError() error

AccError - return accumulated error

func (*ByteWriter) WriteSlice added in v0.43.0 

func (a *ByteWriter) WriteSlice(s []byte)

WriteSlice - write a slice

func (*ByteWriter) WriteUint16 added in v0.43.0 

func (a *ByteWriter) WriteUint16(u uint16)

WriteUint16 - write uint16

func (*ByteWriter) WriteUint32 added in v0.43.0 

func (a *ByteWriter) WriteUint32(u uint32)

WriteUint32 - write uint32

func (*ByteWriter) WriteUint48 added in v0.43.0 

func (a *ByteWriter) WriteUint48(u uint64)

WriteUint48 - write uint48

func (*ByteWriter) WriteUint64 added in v0.43.0 

func (a *ByteWriter) WriteUint64(u uint64)

WriteUint64 - write uint64

func (*ByteWriter) WriteUint8 added in v0.43.0 

func (a *ByteWriter) WriteUint8(b byte)

WriteUint8 - write a byte

type EBSPReader 

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

EBSPReader reads an EBSP bitstream dropping start-code emulation bytes. It also supports checking for more rbsp data and reading rbsp_trailing_bits.

func NewEBSPReader 

func NewEBSPReader(rd io.Reader) *EBSPReader

NewEBSPReader return a new EBSP reader stopping reading at first error.

func (*EBSPReader) AccError added in v0.43.0 

func (r *EBSPReader) AccError() error

AccError returns the accumulated error. If no error, returns nil.

func (*EBSPReader) IsSeeker 

func (r *EBSPReader) IsSeeker() bool

IsSeeker returns tru if underluing reader supports Seek interface.

func (*EBSPReader) MoreRbspData 

func (r *EBSPReader) MoreRbspData() (bool, error)

MoreRbspData returns false if next bit is 1 and last 1-bit in fullSlice. Underlying reader must support ReadSeeker interface to reset after check. Return false, nil if underlying error.

func (*EBSPReader) NrBitsRead added in v0.43.0 

func (r *EBSPReader) NrBitsRead() int

NrBitsRead returns total number of bits read into parser.

func (*EBSPReader) NrBitsReadInCurrentByte 

func (r *EBSPReader) NrBitsReadInCurrentByte() int

NrBitsReadInCurrentByte returns number of bits read in current byte.

func (*EBSPReader) NrBytesRead 

func (r *EBSPReader) NrBytesRead() int

NrBytesRead returns how many bytes read into parser.

func (*EBSPReader) Read 

func (r *EBSPReader) Read(n int) uint

Read reads n bits and respects and accumulates errors. If error, returns 0.

func (*EBSPReader) ReadBytes added in v0.43.0 

func (r *EBSPReader) ReadBytes(n int) []byte

ReadBytes read n bytes and return nil if new or accumulated error.

func (*EBSPReader) ReadExpGolomb 

func (r *EBSPReader) ReadExpGolomb() uint

ReadExpGolomb reads one unsigned exponential Golomb code.

func (*EBSPReader) ReadFlag 

func (r *EBSPReader) ReadFlag() bool

ReadFlag reads 1 bit and translates a bool.

func (*EBSPReader) ReadRbspTrailingBits 

func (r *EBSPReader) ReadRbspTrailingBits() error

ReadRbspTrailingBits reads rbsp_traling_bits. Returns error if wrong pattern. If other error, returns nil and let AccError() provide that error.

func (*EBSPReader) ReadSignedGolomb 

func (r *EBSPReader) ReadSignedGolomb() int

ReadSignedGolomb reads one signed exponential Golomb code.

func (*EBSPReader) SetError added in v0.43.0 

func (r *EBSPReader) SetError(err error)

SetError sets an error if not already set.

type EBSPWriter 

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

EBSPWriter write bits and insert start-code emulation prevention bytes as necessary. Ceases writing at first error. The first error can later be checked with AccError().

func NewEBSPWriter 

func NewEBSPWriter(w io.Writer) *EBSPWriter

NewEBSPWriter - returns a new Writer

func (*EBSPWriter) AccError 

func (w *EBSPWriter) AccError() error

AccError - return accumulated error

func (*EBSPWriter) BitsInBuffer 

func (w *EBSPWriter) BitsInBuffer() (bits, n uint)

BitsInBuffer - n bits written in buffer byte, not written to underlying writer

func (*EBSPWriter) NrBitsInBuffer 

func (w *EBSPWriter) NrBitsInBuffer() uint

NrBitsInBuffer - number bits written in buffer byte

func (*EBSPWriter) StuffByteWithZeros 

func (w *EBSPWriter) StuffByteWithZeros()

StuffByteWithZeros - write zero bits until byte boundary (0-7bits)

func (*EBSPWriter) Write 

func (w *EBSPWriter) Write(bits uint, n int)

Write - write n bits from bits and save error state

func (*EBSPWriter) WriteExpGolomb 

func (w *EBSPWriter) WriteExpGolomb(nr uint)

WriteExpGolomb - write an exponential Golomb code

func (*EBSPWriter) WriteRbspTrailingBits 

func (w *EBSPWriter) WriteRbspTrailingBits()

WriteRbspTrailingBits - write rbsp trailing bits (a 1 followed by zeros to a byte boundary)

func (*EBSPWriter) WriteSEIValue 

func (w *EBSPWriter) WriteSEIValue(val uint)

WriteSEIValue insert 0xFF until value is less than 255. Used in SEI payload type and size.

type FixedSliceReader 

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

FixedSliceReader - read integers and other data from a fixed slice. Accumulates error, and the first error can be retrieved. If err != nil, 0 or empty string is returned

func NewFixedSliceReader 

func NewFixedSliceReader(data []byte) *FixedSliceReader

bits.NewFixedSliceReader creates a new slice reader reading from data

func (*FixedSliceReader) AccError 

func (s *FixedSliceReader) AccError() error

AccError - get accumulated error after read operations

func (*FixedSliceReader) GetPos 

func (s *FixedSliceReader) GetPos() int

GetPos - get read position is slice

func (*FixedSliceReader) Length 

func (s *FixedSliceReader) Length() int

Length - get length of slice

func (*FixedSliceReader) LookAhead added in v0.33.0 

func (s *FixedSliceReader) LookAhead(offset int, data []byte) error

LookAhead returns data ahead of current pos if within bounds.

func (*FixedSliceReader) NrRemainingBytes 

func (s *FixedSliceReader) NrRemainingBytes() int

NrRemainingBytes - return number of bytes remaining

func (*FixedSliceReader) ReadBytes 

func (s *FixedSliceReader) ReadBytes(n int) []byte

ReadBytes - read a slice of n bytes Return empty slice if n bytes not available

func (*FixedSliceReader) ReadFixedLengthString 

func (s *FixedSliceReader) ReadFixedLengthString(n int) string

ReadFixedLengthString - read string of specified length n. Sets err and returns empty string if full length not available

func (*FixedSliceReader) ReadInt16 

func (s *FixedSliceReader) ReadInt16() int16

ReadInt16 - read int16 from slice

func (*FixedSliceReader) ReadInt32 

func (s *FixedSliceReader) ReadInt32() int32

ReadInt32 - read int32 from slice

func (*FixedSliceReader) ReadInt64 

func (s *FixedSliceReader) ReadInt64() int64

ReadInt64 - read int64 from slice

func (*FixedSliceReader) ReadPossiblyZeroTerminatedString added in v0.45.0 

func (s *FixedSliceReader) ReadPossiblyZeroTerminatedString(maxLen int) (str string, ok bool)

ReadPossiblyZeroTerminatedString - read string until zero byte but at most maxLen. If maxLen is reached and no zero-byte, return string and ok = false

func (*FixedSliceReader) ReadUint16 

func (s *FixedSliceReader) ReadUint16() uint16

ReadUint16 - read uint16 from slice

func (*FixedSliceReader) ReadUint24 

func (s *FixedSliceReader) ReadUint24() uint32

ReadUint24 - read uint24 from slice

func (*FixedSliceReader) ReadUint32 

func (s *FixedSliceReader) ReadUint32() uint32

ReadUint32 - read uint32 from slice

func (*FixedSliceReader) ReadUint64 

func (s *FixedSliceReader) ReadUint64() uint64

ReadUint64 - read uint64 from slice

func (*FixedSliceReader) ReadUint8 

func (s *FixedSliceReader) ReadUint8() byte

ReadUint8 - read uint8 from slice

func (*FixedSliceReader) ReadZeroTerminatedString 

func (s *FixedSliceReader) ReadZeroTerminatedString(maxLen int) string

ReadZeroTerminatedString - read string until zero byte but at most maxLen Set err and return empty string if no zero byte found.

func (*FixedSliceReader) RemainingBytes 

func (s *FixedSliceReader) RemainingBytes() []byte

RemainingBytes - return remaining bytes of this slice

func (*FixedSliceReader) SetPos 

func (s *FixedSliceReader) SetPos(pos int)

SetPos - set read position is slice

func (*FixedSliceReader) SkipBytes 

func (s *FixedSliceReader) SkipBytes(n int)

SkipBytes - skip passed n bytes

type FixedSliceWriter 

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

FixedSliceWriter - write numbers to a fixed []byte slice

func NewFixedSliceWriter 

func NewFixedSliceWriter(size int) *FixedSliceWriter

NewSliceWriter - create slice writer with fixed size.

func NewFixedSliceWriterFromSlice 

func NewFixedSliceWriterFromSlice(data []byte) *FixedSliceWriter

NewFixedSliceWriter - create writer around slice. The slice will not grow, but stay the same size. If too much data is written, there will be an accumuluated error. Can be retrieved with AccError()

func (*FixedSliceWriter) AccError 

func (sw *FixedSliceWriter) AccError() error

AccError - return accumulated erro

func (*FixedSliceWriter) Bytes 

func (sw *FixedSliceWriter) Bytes() []byte

Bytes - return buf up to what's written

func (*FixedSliceWriter) Capacity 

func (sw *FixedSliceWriter) Capacity() int

Capacity - max length of FixedSliceWriter buffer

func (*FixedSliceWriter) FlushBits 

func (sw *FixedSliceWriter) FlushBits()

FlushBits - write remaining bits to the underlying .Writer. bits will be left-shifted and zeros appended to fill up a byte.

func (*FixedSliceWriter) Len 

func (sw *FixedSliceWriter) Len() int

Len - length of FixedSliceWriter buffer written. Same as Offset()

func (*FixedSliceWriter) Offset 

func (sw *FixedSliceWriter) Offset() int

Offset - offset for writing in FixedSliceWriter buffer

func (*FixedSliceWriter) WriteBits 

func (sw *FixedSliceWriter) WriteBits(bits uint, n int)

func (*FixedSliceWriter) WriteBytes 

func (sw *FixedSliceWriter) WriteBytes(byteSlice []byte)

WriteBytes - write []byte

func (*FixedSliceWriter) WriteFlag 

func (sw *FixedSliceWriter) WriteFlag(f bool)

WriteFlag writes a flag as 1 bit.

func (*FixedSliceWriter) WriteInt16 

func (sw *FixedSliceWriter) WriteInt16(n int16)

WriteInt16 - write int16 to slice

func (*FixedSliceWriter) WriteInt32 

func (sw *FixedSliceWriter) WriteInt32(n int32)

WriteInt32 - write int32 to slice

func (*FixedSliceWriter) WriteInt64 

func (sw *FixedSliceWriter) WriteInt64(n int64)

WriteInt64 - write int64 to slice

func (*FixedSliceWriter) WriteString 

func (sw *FixedSliceWriter) WriteString(s string, addZeroEnd bool)

WriteString - write string to slice with or without zero end

func (*FixedSliceWriter) WriteUint16 

func (sw *FixedSliceWriter) WriteUint16(n uint16)

WriteUint16 - write uint16 to slice

func (*FixedSliceWriter) WriteUint24 

func (sw *FixedSliceWriter) WriteUint24(n uint32)

WriteUint24 - write uint24 to slice

func (*FixedSliceWriter) WriteUint32 

func (sw *FixedSliceWriter) WriteUint32(n uint32)

WriteUint32 - write uint32 to slice

func (*FixedSliceWriter) WriteUint48 

func (sw *FixedSliceWriter) WriteUint48(u uint64)

WriteUint48 - write uint48

func (*FixedSliceWriter) WriteUint64 

func (sw *FixedSliceWriter) WriteUint64(n uint64)

WriteUint64 - write uint64 to slice

func (*FixedSliceWriter) WriteUint8 

func (sw *FixedSliceWriter) WriteUint8(n byte)

WriteUint8 - write byte to slice

func (*FixedSliceWriter) WriteUnityMatrix 

func (sw *FixedSliceWriter) WriteUnityMatrix()

WriteUnityMatrix - write a unity matrix for mvhd or tkhd

func (*FixedSliceWriter) WriteZeroBytes 

func (sw *FixedSliceWriter) WriteZeroBytes(n int)

WriteZeroBytes - write n byte of zeroes

type Reader 

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

Reader is a bit reader that stops reading at first error and stores it. First error can be fetched usiin AccError().

func NewReader 

func NewReader(rd io.Reader) *Reader

NewReader return a new Reader that accumulates errors.

func (*Reader) AccError added in v0.43.0 

func (r *Reader) AccError() error

AccError - accumulated error is first error that occurred

func (*Reader) NrBitsRead added in v0.43.0 

func (r *Reader) NrBitsRead() int

NrBitsRead returns total number of bits read into parser.

func (*Reader) NrBitsReadInCurrentByte added in v0.43.0 

func (r *Reader) NrBitsReadInCurrentByte() int

NrBitsReadInCurrentByte returns number of bits read in current byte.

func (*Reader) NrBytesRead added in v0.43.0 

func (r *Reader) NrBytesRead() int

NrBytesRead returns how many bytes read into parser.

func (*Reader) Read 

func (r *Reader) Read(n int) uint

Read - read n bits. Return 0, if error now or previously

func (*Reader) ReadFlag 

func (r *Reader) ReadFlag() bool

ReadFlag reads 1 bit and interprets as a boolean flag. Returns false if error now or previously.

func (*Reader) ReadRemainingBytes added in v0.43.0 

func (r *Reader) ReadRemainingBytes() []byte

ReadRemainingBytes reads remaining bytes if byte-aligned. Returns nil if error now or previously.

func (*Reader) ReadSigned added in v0.43.0 

func (r *Reader) ReadSigned(n int) int

ReadSigned reads a 2-complemented signed int with n bits.

type SliceReader 

type SliceReader interface {
	AccError() error
	ReadUint8() byte
	ReadUint16() uint16
	ReadInt16() int16
	ReadUint24() uint32
	ReadUint32() uint32
	ReadInt32() int32
	ReadUint64() uint64
	ReadInt64() int64
	ReadFixedLengthString(n int) string
	ReadZeroTerminatedString(maxLen int) string
	ReadPossiblyZeroTerminatedString(maxLen int) (str string, ok bool)
	ReadBytes(n int) []byte
	RemainingBytes() []byte
	NrRemainingBytes() int
	SkipBytes(n int)
	SetPos(pos int)
	GetPos() int
	Length() int
	LookAhead(offset int, data []byte) error
}

type SliceWriter 

type SliceWriter interface {
	Len() int
	Capacity() int
	Offset() int
	Bytes() []byte
	AccError() error
	WriteUint8(n byte)
	WriteUint16(n uint16)
	WriteInt16(n int16)
	WriteUint24(n uint32)
	WriteUint32(n uint32)
	WriteInt32(n int32)
	WriteUint48(u uint64)
	WriteUint64(n uint64)
	WriteInt64(n int64)
	WriteString(s string, addZeroEnd bool)
	WriteZeroBytes(n int)
	WriteBytes(byteSlice []byte)
	WriteUnityMatrix()
	WriteBits(bits uint, n int)
	WriteFlag(f bool)
	FlushBits()
}

type Writer 

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

Writer writes bits into underlying io.Writer. Stops writing at first error. That first error is stored and can later be checked with AccError().

func NewWriter 

func NewWriter(w io.Writer) *Writer

NewWriter returns a new Writer

func (*Writer) AccError added in v0.43.0 

func (w *Writer) AccError() error

AccError returns the first error that occurred and stopped writing.

func (*Writer) Flush 

func (w *Writer) Flush()

Flush writes remaining bits to the underlying io.Writer by adding zeros to the right.

func (*Writer) Write 

func (w *Writer) Write(bits uint, n int)

Write writes n bits from bits and saves error state.

Source Files

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