buffer

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 Go to latest Published: Jul 3, 2021 License: BSD-2-Clause Imports: 10 Imported by: 0

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buffer

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This package implements high-efficiency byte buffer types.

Documentation

Overview

Package buffer provides multiple byte buffer implementations.

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

This section is empty.

Types

type Buffer 

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

Buffer implements a byte buffer. The Buffer has space for 2**N bytes for user-specified N.

func New 

func New(numBits uint) *Buffer

New is a convenience function that allocates a new Buffer and calls Init on it.

func (Buffer) Bytes 

func (buffer Buffer) Bytes() []byte

Bytes allocates and returns a copy of the Buffer's contents.

func (Buffer) BytesView 

func (buffer Buffer) BytesView() []byte

BytesView returns a slice into the Buffer's contents.

func (*Buffer) Clear 

func (buffer *Buffer) Clear()

Clear erases the contents of the Buffer.

func (*Buffer) CommitBulkRead 

func (buffer *Buffer) CommitBulkRead(length uint)

CommitBulkRead completes the bulk read begun by the previous call to PrepareBulkRead. The argument must be between 0 and the length of the slice returned by PrepareBulkRead.

func (*Buffer) CommitBulkWrite 

func (buffer *Buffer) CommitBulkWrite(length uint)

CommitBulkWrite completes the bulk write begun by the previous call to PrepareBulkWrite. The argument must be between 0 and the length of the slice returned by PrepareBulkWrite.

func (Buffer) DebugString 

func (buffer Buffer) DebugString() string

DebugString returns a detailed dump of the Buffer's internal state.

func (Buffer) GoString 

func (buffer Buffer) GoString() string

GoString returns a brief dump of the Buffer's internal state.

func (*Buffer) Init 

func (buffer *Buffer) Init(numBits uint)

Init initializes the Buffer. The Buffer will hold a maximum of 2**N bits, where N is the argument provided. The argument must be a number between 0 and 31 inclusive.

func (Buffer) IsEmpty 

func (buffer Buffer) IsEmpty() bool

IsEmpty returns true iff the Buffer contains no bytes.

func (Buffer) IsFull 

func (buffer Buffer) IsFull() bool

IsFull returns true iff the Buffer contains the maximum number of bytes.

func (Buffer) Len 

func (buffer Buffer) Len() uint

Len returns the number of bytes currently in the Buffer.

func (Buffer) NumBits 

func (buffer Buffer) NumBits() uint

NumBits returns the number of bits used to initialize this Buffer.

func (*Buffer) PrepareBulkRead 

func (buffer *Buffer) PrepareBulkRead(length uint) []byte

PrepareBulkRead obtains a slice from which the caller can read bytes. The bytes do not leave the buffer's contents until CommitBulkRead is called. If CommitBulkRead is not subsequently called, the read acts as a "peek" operation.

The returned slice may contain fewer bytes than requested; it will return a zero-length slice iff the buffer is empty. The caller must check its length before using it. A short but non-empty return slice does *not* indicate an empty buffer.

The returned slice is only valid until the next call to any mutating method on this Buffer; mutating methods are those which take a pointer receiver.

func (*Buffer) PrepareBulkWrite 

func (buffer *Buffer) PrepareBulkWrite(length uint) []byte

PrepareBulkWrite obtains a slice into which the caller can write bytes. The bytes do not become a part of the buffer's contents until CommitBulkWrite is called. If CommitBulkWrite is not subsequently called, the write is considered abandoned.

The returned slice may contain fewer bytes than requested; it will return a nil slice iff the buffer is full. The caller must check the slice's length before using it. A short but non-empty return slice does *not* indicate a full buffer.

The returned slice is only valid until the next call to any mutating method on this Buffer; mutating methods are those which take a pointer receiver.

func (*Buffer) Read 

func (buffer *Buffer) Read(data []byte) (int, error)

Read reads a slice of bytes from the Buffer. If the buffer is empty, ErrEmpty is returned.

func (*Buffer) ReadByte 

func (buffer *Buffer) ReadByte() (byte, error)

ReadByte reads a single byte from the Buffer. If the buffer is empty, ErrEmpty is returned.

func (*Buffer) ReadFrom 

func (buffer *Buffer) ReadFrom(r io.Reader) (int64, error)

ReadFrom attempts to fill this Buffer by reading from the provided Reader. May return any error returned by the Reader, including io.EOF. If a nil error is returned, then the buffer is now full.

func (Buffer) Size 

func (buffer Buffer) Size() uint

Size returns the maximum byte capacity of the Buffer.

func (Buffer) String 

func (buffer Buffer) String() string

String returns a plain-text description of the buffer.

func (*Buffer) Write 

func (buffer *Buffer) Write(data []byte) (int, error)

Write writes a slice of bytes to the Buffer. If the Buffer is full, as many bytes as possible are written to the Buffer and ErrFull is returned.

func (*Buffer) WriteByte 

func (buffer *Buffer) WriteByte(ch byte) error

WriteByte writes a single byte to the Buffer. If the Buffer is full, ErrFull is returned.

func (*Buffer) WriteTo 

func (buffer *Buffer) WriteTo(w io.Writer) (int64, error)

WriteTo attempts to drain this Buffer by writing to the provided Writer. May return any error returned by the Writer. If a nil error is returned, then the Buffer is now empty.

type Error 

type Error byte

Error is the type for the error constants returned by this package. 

const (
	// ErrEmpty is returned when reading from an empty Buffer.
	ErrEmpty Error = iota

	// ErrFull is returned when writing to a full Buffer.
	ErrFull

	// ErrBadDistance is returned when Window.LookupByte is called with a
	// distance that isn't contained within the Window.
	ErrBadDistance
)

func (Error) Error 

func (err Error) Error() string

Error returns the error message for this error.

func (Error) GoString 

func (err Error) GoString() string

GoString returns the name of the Go constant.

type Hybrid 

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

Hybrid implements a combination Window/Buffer that uses the Window to remember bytes that were recently removed from the Buffer, and that hashes all data that enters the Window so that LZ77-style prefix matching can be made efficient.

func NewHybrid 

func NewHybrid(o HybridOptions) *Hybrid

NewHybrid is a convenience function that allocates a Hybrid and calls Init on it.

func (*Hybrid) Advance 

func (hybrid *Hybrid) Advance() (buf []byte, matchDistance uint, matchLength uint, matchFound bool)

Advance moves a slice of bytes from the Hybrid's Buffer to its Window. The nature of the slice depends on the Hybrid's prefix match settings, the contents of the Hybrid's Window, and the contents of the Hybrid's Buffer.

func (Hybrid) BufferNumBits 

func (hybrid Hybrid) BufferNumBits() uint

BufferNumBits returns the size of the Buffer in bits.

func (*Hybrid) Clear 

func (hybrid *Hybrid) Clear()

Clear clears all data in the entire Hybrid.

func (*Hybrid) CommitBulkRead 

func (hybrid *Hybrid) CommitBulkRead(length uint)

CommitBulkRead completes the bulk read begun by the previous call to PrepareBulkRead. The argument must be between 0 and the length of the slice returned by PrepareBulkRead.

func (*Hybrid) CommitBulkWrite 

func (hybrid *Hybrid) CommitBulkWrite(length uint)

CommitBulkWrite completes the bulk write begun by the previous call to PrepareBulkWrite. The argument must be between 0 and the length of the slice returned by PrepareBulkWrite.

func (Hybrid) DebugString 

func (hybrid Hybrid) DebugString() string

DebugString returns a detailed dump of the Hybrid's internal state.

func (Hybrid) GoString 

func (hybrid Hybrid) GoString() string

GoString returns a brief dump of the Hybrid's internal state.

func (Hybrid) HashNumBits 

func (hybrid Hybrid) HashNumBits() uint

HashNumBits returns the size of the hash function output in bits.

func (*Hybrid) Init 

func (hybrid *Hybrid) Init(o HybridOptions)

Init initializes a Hybrid.

func (Hybrid) IsEmpty 

func (hybrid Hybrid) IsEmpty() bool

IsEmpty returns true iff the Hybrid's Buffer is empty.

func (Hybrid) IsFull 

func (hybrid Hybrid) IsFull() bool

IsFull returns true iff the Hybrid's Buffer is full.

func (Hybrid) Len 

func (hybrid Hybrid) Len() uint

Len returns the number of bytes currently in the Hybrid's Buffer.

func (Hybrid) Options 

func (hybrid Hybrid) Options() HybridOptions

Options returns a HybridOptions struct which can be used to construct a new Hybrid with the same settings.

func (*Hybrid) PrepareBulkRead 

func (hybrid *Hybrid) PrepareBulkRead(length uint) []byte

PrepareBulkRead obtains a slice from which the caller can read bytes. See Buffer.PrepareBulkRead for more details.

func (*Hybrid) PrepareBulkWrite 

func (hybrid *Hybrid) PrepareBulkWrite(length uint) []byte

PrepareBulkWrite obtains a slice into which the caller can write bytes. See Buffer.PrepareBulkWrite for more details.

func (*Hybrid) Read 

func (hybrid *Hybrid) Read(data []byte) (int, error)

Read reads a slice of bytes from the Hybrid's Buffer. If the buffer is empty, ErrEmpty is returned.

func (*Hybrid) ReadByte 

func (hybrid *Hybrid) ReadByte() (byte, error)

ReadByte reads a single byte, or returns ErrEmpty if the buffer is empty.

func (*Hybrid) SetWindow 

func (hybrid *Hybrid) SetWindow(data []byte)

SetWindow replaces the Hybrid's Window with the given data.

func (Hybrid) String 

func (hybrid Hybrid) String() string

String returns a plain-text description of the Hybrid.

func (*Hybrid) WindowClear 

func (hybrid *Hybrid) WindowClear()

WindowClear clears just the data in the Hybrid's Window.

func (Hybrid) WindowNumBits 

func (hybrid Hybrid) WindowNumBits() uint

WindowNumBits returns the size of the Window in bits.

func (*Hybrid) Write 

func (hybrid *Hybrid) Write(data []byte) (int, error)

Write writes a slice of bytes to the Hybrid's Buffer.

func (*Hybrid) WriteByte 

func (hybrid *Hybrid) WriteByte(ch byte) error

WriteByte writes a single byte to the Hybrid's Buffer.

type HybridOptions 

type HybridOptions struct {
	BufferNumBits       uint
	WindowNumBits       uint
	HashNumBits         uint
	MinMatchLength      uint
	MaxMatchLength      uint
	MaxMatchDistance    uint
	HasMinMatchLength   bool
	HasMaxMatchLength   bool
	HasMaxMatchDistance bool
}

HybridOptions holds options for initializing an instance of Hybrid.

func (HybridOptions) Equal 

func (opts HybridOptions) Equal(other HybridOptions) bool

Equal returns true iff the given HybridOptions is semantically equal to this one.

type Window 

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

Window implements a sliding window. The Window has space for 2**N bytes for user-specified N.

func NewWindow 

func NewWindow(numBits uint) *Window

NewWindow is a convenience function that allocates a Window and calls Init on it.

func (Window) Bytes 

func (window Window) Bytes() []byte

Bytes allocates and returns a copy of the Window's contents.

func (Window) BytesView 

func (window Window) BytesView() []byte

BytesView returns a slice into the Window's contents.

The returned slice is only valid until the next call to any mutating method on this Window; mutating methods are those which take a pointer receiver.

func (*Window) Clear 

func (window *Window) Clear()

Clear erases the contents of the Window.

func (*Window) CommitBulkWrite 

func (window *Window) CommitBulkWrite(length uint)

CommitBulkWrite completes the bulk write begun by the previous call to PrepareBulkWrite. The argument must be between 0 and the length of the slice returned by PrepareBulkWrite.

func (Window) DebugString 

func (window Window) DebugString() string

DebugString returns a detailed dump of the Window's internal state.

func (Window) GoString 

func (window Window) GoString() string

GoString returns a brief dump of the Window's internal state.

func (Window) Hash 

func (window Window) Hash(hashes ...hash.Hash)

Hash non-destructively writes the contents of the Window into the provided Hash object(s).

func (Window) Hash32 

func (window Window) Hash32(fn func() hash.Hash32) uint32

Hash32 is a convenience method that constructs a Hash32, calls Window.Hash with it, and calls Sum32 on it.

func (*Window) Init 

func (window *Window) Init(numBits uint)

Init initializes the Window. The Window will hold a maximum of 2**N bits, where N is the argument provided. The argument must be a number between 0 and 31 inclusive.

func (Window) IsZero 

func (window Window) IsZero() bool

IsZero returns true iff the Window contains only 0 bytes.

func (Window) LookupByte 

func (window Window) LookupByte(distance uint) (byte, error)

LookupByte returns a byte which was written previously. The argument is the offset into the window, with 1 representing the most recently written byte and Window.Size() representing the oldest byte still within the Window.

func (Window) NumBits 

func (window Window) NumBits() uint

NumBits returns the number of bits used to initialize this Window.

func (*Window) PrepareBulkWrite 

func (window *Window) PrepareBulkWrite(length uint) []byte

PrepareBulkWrite obtains a slice into which the caller can write bytes. The bytes do not become a part of the Window's contents until CommitBulkWrite is called. If CommitBulkWrite is not subsequently called, the write is considered abandoned.

The returned slice may contain fewer bytes than requested, if the provided length is greater than the size of the Window. The caller must check the slice's length before using it.

The returned slice is only valid until the next call to any mutating method on this Window; mutating methods are those which take a pointer receiver.

func (Window) Size 

func (window Window) Size() uint

Size returns the maximum byte capacity of the Window.

func (Window) String 

func (window Window) String() string

String returns a plain-text description of the Window.

func (*Window) Write 

func (window *Window) Write(data []byte) (int, error)

Write writes a slice of bytes to the Window. The oldest len(data) bytes in the Window are dropped to make room. If len(data) exceeds Window.Size(), then only the last Window.Size() bytes of the slice will be recorded.

func (*Window) WriteByte 

func (window *Window) WriteByte(ch byte) error

WriteByte writes a single byte to the Window. The oldest byte in the Window is dropped to make room.

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