coding

package
v0.6.0 Latest Latest
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 Go to latest Published: Oct 12, 2024 License: BSD-3-Clause Imports: 9 Imported by: 0

Documentation

Overview

Package coding implements low-level QR coding details.

Index

Constants

View Source 
const MaxVersion = 40
View Source 
const MinVersion = 1

Variables

View Source 
var (
	ErrLevel   = errors.New("qr: invalid level")
	ErrVersion = errors.New("qr: invalid version")
)
View Source 
var Field = gf256.NewField(0x11d, 2)

Field is the field for QR error correction.

Functions

func Is added in v0.5.0 

func Is(r rune, mode Mode) bool

Is reports whether r is encodable in mode.

func IsKanji added in v0.5.0 

func IsKanji(r rune) bool

IsKanji reports whether the Unicode rune r belongs to the QR Kanji subset of JIS X 0208.

Types

type AcceptsFunc added in v0.5.0 

type AcceptsFunc func(rune) bool // Used in ModeEncoder.

type BitStream added in v0.5.0 

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

BitStream reads bits from the underlying buffer.

func NewBitStream added in v0.5.0 

func NewBitStream(b []byte) BitStream

NewBitStream returns a BitStream reading from b.

func (*BitStream) Bytes added in v0.5.0 

func (s *BitStream) Bytes() []byte

Bytes returns the data underlying s.

func (*BitStream) Next added in v0.5.0 

func (s *BitStream) Next() byte

Next returns the next bit from s as 0 or 1. Past end of buffer Next returns 0.

type Bits 

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

func NewBits added in v0.5.0 

func NewBits(v Version, l Level) *Bits

NewBits returns Bits with enough capacity for a QR code of the given version and level.

func (*Bits) Add added in v0.5.0 

func (b *Bits) Add(n int) []byte

Add adds n bytes to b and returns the added slice.

func (*Bits) AddCheckBytes 

func (b *Bits) AddCheckBytes(v Version, l Level)

AddCheckBytes adds padding and checksum to b for the given QR version and level.

func (*Bits) Bits 

func (b *Bits) Bits() int

func (*Bits) Bytes 

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

func (*Bits) Grow added in v0.5.0 

func (b *Bits) Grow(n int)

func (*Bits) PadTo added in v0.5.0 

func (b *Bits) PadTo(n int)

PadTo pads b to n*8 bit.

func (*Bits) Permute added in v0.5.0 

func (b *Bits) Permute(v Version, l Level) BitStream

Permute returns a BitStream reading data and checksum bits in b with blocks interleaved for the given QR code version and level. The BitStream may use the same underlying buffer.

func (*Bits) Reset 

func (b *Bits) Reset()

func (*Bits) Write 

func (b *Bits) Write(v uint32, nbit int)

type Code 

type Code struct {
	Bitmap []byte // 1 is black, 0 is white
	Size   int    // number of pixels on a side
	Stride int    // number of bytes per row
}

A Code is a square pixel grid.

func Encode added in v0.5.0 

func Encode(version Version, level Level, text ...Segment) (*Code, error)

Encode encodes text using an Encoder with the given version and level.

func (*Code) Black 

func (c *Code) Black(x, y int) bool

func (*Code) Penalty added in v0.5.0 

func (c *Code) Penalty() int

Penalty returns the penalty value for c. The penalty is used for choosing the mask for the code.

type CutRuneFunc added in v0.5.0 

type CutRuneFunc func(string) (rune, int) // Used in ModeEncoder.

type Encoder added in v0.5.0 

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

Encoder encodes a QR code.

func NewEncoder added in v0.5.0 

func NewEncoder(version Version, level Level) (*Encoder, error)

NewEncoder returns an Encoder for the given version and level.

func (*Encoder) Code added in v0.5.0 

func (e *Encoder) Code() (*Code, error)

Code returns a QR code containing data written to e.

func (*Encoder) Encode added in v0.5.0 

func (e *Encoder) Encode(text ...Segment) (*Code, error)

Encode is a wrapper around Write and Code.

func (*Encoder) Reset added in v0.5.0 

func (e *Encoder) Reset()

func (*Encoder) Write added in v0.5.0 

func (e *Encoder) Write(text ...Segment) error

Write adds text to e.

type Level 

type Level int

A Level represents a QR error correction level. From least to most tolerant of errors, they are L, M, Q, H. 

const (
	L Level = iota
	M
	Q
	H
)

func (Level) String 

func (l Level) String() string

type Mode added in v0.5.0 

type Mode int16

A Mode is a QR segment encoder. 

const (
	Numeric       Mode = iota // numeric mode, ASCII-compatible text
	Alphanumeric              // alphanumeric mode, ASCII-compatible text
	Byte                      // byte mode, any data
	Kanji                     // kanji mode, UTF-8 text
	Latin1                    // byte mode, UTF-8 text encoded as ISO 8859-1
	ShiftJISKanji             // kanji mode, Shift JIS text
	ECI                       // eci mode, raw segment
	StructAppend              // structured append, raw segment
)

Predefined encoding modes.

func AddMode added in v0.5.0 

func AddMode(m *ModeEncoder) Mode

AddMode registers an encoding mode, returning its number on success or -1 on failure. The number of modes is limited to 32768.

func (Mode) Length added in v0.5.0 

func (mode Mode) Length(bytes, runes int, class int) int

Length returns the length in bits of a valid string of the given length in bytes and runes encoded in mode at the given QR version size class, including the header. Length returns 0 if and only if mode is invalid.

func (Mode) RuneFilter added in v0.5.0 

func (mode Mode) RuneFilter() (CutRuneFunc, AcceptsFunc)

RuneFilter returns CutRune and Accepts functions for mode. If mode is invalid, RuneFilter returns nil and a function rejecting any rune.

func (Mode) String added in v0.6.0 

func (mode Mode) String() string

type ModeEncoder added in v0.5.0 

type ModeEncoder struct {
	Name      string // Name for error reporting
	Indicator byte   // 4 bit mode indicator

	// CountLength lists lengths of the character count field in three
	// QR version size classes.
	CountLength [3]byte

	// EncodedLength returns the encoded data length in bits of a valid
	// string of the given length in bytes and runes.
	EncodedLength func(bytes, runes int) int

	// Valid reports whether the string is valid for the encoding mode.
	// It is called by Segment.IsValid and by the encoder.  If nil, the
	// string is validated using CutRune and Accepts.
	Valid func(string) bool

	// CutRune returns the first rune in the string and its width in
	// bytes.  If nil, utf8.DecodeRuneInString is used.  It should be
	// set if and only if the Mode requires non-UTF-8 rune decoding.
	CutRune func(string) (rune, int)

	// Accepts reports whether the encoding mode accepts the rune.
	// If nil, any rune is accepted.  It is called by Is.
	Accepts func(rune) bool

	// Transform returns a segment of another Mode with the string
	// transformed for encoding and a boolean indicating whether the
	// transform was successful.  The target Mode must have Transform
	// unset.  If nil, the original segment is used.  It is called by
	// Segment.Transform and by the encoder.
	Transform func(string) (Segment, bool)

	// Count returns the character count of the transformed string.
	// If nil, the length of the string in bytes is used.
	Count func(string) int

	// Encode4, Encode3, Encode2 and Encode1 return the encoding of the
	// bytes and its length in bits.  The encoder calls a non-nil
	// Encode{N} repeatedly as long as N source bytes are available, in
	// descending order of N.  If all are nil, each byte is encoded as
	// 8 bits.  The encoder panics if not all bytes are consumed.
	Encode4 func([4]byte) (uint32, int)
	Encode3 func([3]byte) (uint32, int)
	Encode2 func([2]byte) (uint32, int)
	Encode1 func(byte) (uint32, int)
}

ModeEncoder implements a QR segment encoding.

The segment is validated using either Valid or CutRune and Accepts. Text mode encoders must have a Transform function returning a Numeric, Alphanumeric, Byte or ShiftJISKanji mode segment. If set, it is called by Segment.Transform after validation. The encoder calls Segment.Transform and validates the returned segment before encoding.

Package split uses CutRune, Accepts, EncodedLength and CountLength to split text into segments, and Transform for calculating the checksum when splitting input into multiple QR codes (Structured Append).

func GetMode added in v0.5.0 

func GetMode(mode Mode) *ModeEncoder

GetMode returns a copy of ModeEncoder for the mode. It can be used to base the implementation of a new mode on an existing one.

type ModeError added in v0.6.0 

type ModeError Mode

ModeError represents an invalid Mode number or ModeEncoder.

func (ModeError) Error added in v0.6.0 

func (e ModeError) Error() string

type Plan 

type Plan struct {
	Version Version // QR code version
	Level   Level   // QR error correction Level

	DataBytes int // number of data bytes
	Size      int // number of pixels on a side

	Map     []byte    // pixel map: 0 is data or checksum, 1 is other
	Pattern [8][]byte // position and alignment boxes, timing, format, mask
}

A Plan describes how to construct a QR code with a specific version and level.

func NewPlan 

func NewPlan(version Version, level Level) (*Plan, error)

NewPlan returns a Plan for a QR code with the given version and level.

func (*Plan) Encode 

func (p *Plan) Encode(text ...Segment) (*Code, error)

func (*Plan) Serialise added in v0.5.0 

func (p *Plan) Serialise(s BitStream, bitmap []byte)

Serialise writes bits from s to the bitmap in zigzag scan order.

type Segment added in v0.5.0 

type Segment struct {
	Text string // data to encode
	Mode Mode   // encoding mode
}

A Segment describes a QR code segment.

func (Segment) Encode added in v0.5.0 

func (seg Segment) Encode(b *Bits, class int) error

Encode writes seg encoded for the given QR version size class to b.

func (Segment) EncodedLength added in v0.5.0 

func (seg Segment) EncodedLength(class int) int

EncodedLength returns the encoded length in bits of seg in the given QR version size class. EncodedLength returns 0 if and only if mode is invalid. The segment is not validated.

func (Segment) IsValid added in v0.5.0 

func (seg Segment) IsValid() bool

IsValid reports whether seg is encodable.

func (Segment) Transform added in v0.5.0 

func (seg Segment) Transform() (Segment, error)

Transform transforms seg for encoding. The transformed segment is not validated. The encoder calls Transform prior to encoding.

type SegmentError added in v0.5.0 

type SegmentError Segment

SegmentError represents an invalid Segment.

func (SegmentError) Error added in v0.5.0 

func (e SegmentError) Error() string

type Version 

type Version int

A Version represents a QR version. The version specifies the size of the QR code: a QR code with version v has 4v+17 pixels on a side. Versions number from 1 to 40: the larger the version, the more information the code can store.

func (Version) DataBytes 

func (v Version) DataBytes(l Level) int

DataBytes returns the number of data bytes that can be stored in a QR code with the given version and level.

func (Version) SizeClass added in v0.5.0 

func (v Version) SizeClass() int

SizeClass returns the size class of v. The size class if 0 for versions 1 to 9, 1 for 10 to 26 and 2 for 27 to 40.

func (Version) String 

func (v Version) String() string

Source Files

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