From 84d2482ddbff9564c9ad75b2d30af66e3ddfd44d Mon Sep 17 00:00:00 2001
From: Christopher Speller <crspeller@gmail.com>
Date: Thu, 12 May 2016 15:08:58 -0400
Subject: Updating go depencancies. Switching to go1.6 vendoring (#2949)

---
 vendor/github.com/mattermost/rsc/qr/coding/qr.go | 815 +++++++++++++++++++++++
 1 file changed, 815 insertions(+)
 create mode 100644 vendor/github.com/mattermost/rsc/qr/coding/qr.go

(limited to 'vendor/github.com/mattermost/rsc/qr/coding/qr.go')

diff --git a/vendor/github.com/mattermost/rsc/qr/coding/qr.go b/vendor/github.com/mattermost/rsc/qr/coding/qr.go
new file mode 100644
index 000000000..35711a4eb
--- /dev/null
+++ b/vendor/github.com/mattermost/rsc/qr/coding/qr.go
@@ -0,0 +1,815 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package coding implements low-level QR coding details.
+package coding
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+
+	"github.com/mattermost/rsc/gf256"
+)
+
+// Field is the field for QR error correction.
+var Field = gf256.NewField(0x11d, 2)
+
+// 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.
+type Version int
+
+const MinVersion = 1
+const MaxVersion = 40
+
+func (v Version) String() string {
+	return strconv.Itoa(int(v))
+}
+
+func (v Version) sizeClass() int {
+	if v <= 9 {
+		return 0
+	}
+	if v <= 26 {
+		return 1
+	}
+	return 2
+}
+
+// DataBytes returns the number of data bytes that can be
+// stored in a QR code with the given version and level.
+func (v Version) DataBytes(l Level) int {
+	vt := &vtab[v]
+	lev := &vt.level[l]
+	return vt.bytes - lev.nblock*lev.check
+}
+
+// Encoding implements a QR data encoding scheme.
+// The implementations--Numeric, Alphanumeric, and String--specify
+// the character set and the mapping from UTF-8 to code bits.
+// The more restrictive the mode, the fewer code bits are needed.
+type Encoding interface {
+	Check() error
+	Bits(v Version) int
+	Encode(b *Bits, v Version)
+}
+
+type Bits struct {
+	b    []byte
+	nbit int
+}
+
+func (b *Bits) Reset() {
+	b.b = b.b[:0]
+	b.nbit = 0
+}
+
+func (b *Bits) Bits() int {
+	return b.nbit
+}
+
+func (b *Bits) Bytes() []byte {
+	if b.nbit%8 != 0 {
+		panic("fractional byte")
+	}
+	return b.b
+}
+
+func (b *Bits) Append(p []byte) {
+	if b.nbit%8 != 0 {
+		panic("fractional byte")
+	}
+	b.b = append(b.b, p...)
+	b.nbit += 8 * len(p)
+}
+
+func (b *Bits) Write(v uint, nbit int) {
+	for nbit > 0 {
+		n := nbit
+		if n > 8 {
+			n = 8
+		}
+		if b.nbit%8 == 0 {
+			b.b = append(b.b, 0)
+		} else {
+			m := -b.nbit & 7
+			if n > m {
+				n = m
+			}
+		}
+		b.nbit += n
+		sh := uint(nbit - n)
+		b.b[len(b.b)-1] |= uint8(v >> sh << uint(-b.nbit&7))
+		v -= v >> sh << sh
+		nbit -= n
+	}
+}
+
+// Num is the encoding for numeric data.
+// The only valid characters are the decimal digits 0 through 9.
+type Num string
+
+func (s Num) String() string {
+	return fmt.Sprintf("Num(%#q)", string(s))
+}
+
+func (s Num) Check() error {
+	for _, c := range s {
+		if c < '0' || '9' < c {
+			return fmt.Errorf("non-numeric string %#q", string(s))
+		}
+	}
+	return nil
+}
+
+var numLen = [3]int{10, 12, 14}
+
+func (s Num) Bits(v Version) int {
+	return 4 + numLen[v.sizeClass()] + (10*len(s)+2)/3
+}
+
+func (s Num) Encode(b *Bits, v Version) {
+	b.Write(1, 4)
+	b.Write(uint(len(s)), numLen[v.sizeClass()])
+	var i int
+	for i = 0; i+3 <= len(s); i += 3 {
+		w := uint(s[i]-'0')*100 + uint(s[i+1]-'0')*10 + uint(s[i+2]-'0')
+		b.Write(w, 10)
+	}
+	switch len(s) - i {
+	case 1:
+		w := uint(s[i] - '0')
+		b.Write(w, 4)
+	case 2:
+		w := uint(s[i]-'0')*10 + uint(s[i+1]-'0')
+		b.Write(w, 7)
+	}
+}
+
+// Alpha is the encoding for alphanumeric data.
+// The valid characters are 0-9A-Z$%*+-./: and space.
+type Alpha string
+
+const alphabet = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./:"
+
+func (s Alpha) String() string {
+	return fmt.Sprintf("Alpha(%#q)", string(s))
+}
+
+func (s Alpha) Check() error {
+	for _, c := range s {
+		if strings.IndexRune(alphabet, c) < 0 {
+			return fmt.Errorf("non-alphanumeric string %#q", string(s))
+		}
+	}
+	return nil
+}
+
+var alphaLen = [3]int{9, 11, 13}
+
+func (s Alpha) Bits(v Version) int {
+	return 4 + alphaLen[v.sizeClass()] + (11*len(s)+1)/2
+}
+
+func (s Alpha) Encode(b *Bits, v Version) {
+	b.Write(2, 4)
+	b.Write(uint(len(s)), alphaLen[v.sizeClass()])
+	var i int
+	for i = 0; i+2 <= len(s); i += 2 {
+		w := uint(strings.IndexRune(alphabet, rune(s[i])))*45 +
+			uint(strings.IndexRune(alphabet, rune(s[i+1])))
+		b.Write(w, 11)
+	}
+
+	if i < len(s) {
+		w := uint(strings.IndexRune(alphabet, rune(s[i])))
+		b.Write(w, 6)
+	}
+}
+
+// String is the encoding for 8-bit data.  All bytes are valid.
+type String string
+
+func (s String) String() string {
+	return fmt.Sprintf("String(%#q)", string(s))
+}
+
+func (s String) Check() error {
+	return nil
+}
+
+var stringLen = [3]int{8, 16, 16}
+
+func (s String) Bits(v Version) int {
+	return 4 + stringLen[v.sizeClass()] + 8*len(s)
+}
+
+func (s String) Encode(b *Bits, v Version) {
+	b.Write(4, 4)
+	b.Write(uint(len(s)), stringLen[v.sizeClass()])
+	for i := 0; i < len(s); i++ {
+		b.Write(uint(s[i]), 8)
+	}
+}
+
+// A Pixel describes a single pixel in a QR code.
+type Pixel uint32
+
+const (
+	Black Pixel = 1 << iota
+	Invert
+)
+
+func (p Pixel) Offset() uint {
+	return uint(p >> 6)
+}
+
+func OffsetPixel(o uint) Pixel {
+	return Pixel(o << 6)
+}
+
+func (r PixelRole) Pixel() Pixel {
+	return Pixel(r << 2)
+}
+
+func (p Pixel) Role() PixelRole {
+	return PixelRole(p>>2) & 15
+}
+
+func (p Pixel) String() string {
+	s := p.Role().String()
+	if p&Black != 0 {
+		s += "+black"
+	}
+	if p&Invert != 0 {
+		s += "+invert"
+	}
+	s += "+" + strconv.FormatUint(uint64(p.Offset()), 10)
+	return s
+}
+
+// A PixelRole describes the role of a QR pixel.
+type PixelRole uint32
+
+const (
+	_         PixelRole = iota
+	Position            // position squares (large)
+	Alignment           // alignment squares (small)
+	Timing              // timing strip between position squares
+	Format              // format metadata
+	PVersion            // version pattern
+	Unused              // unused pixel
+	Data                // data bit
+	Check               // error correction check bit
+	Extra
+)
+
+var roles = []string{
+	"",
+	"position",
+	"alignment",
+	"timing",
+	"format",
+	"pversion",
+	"unused",
+	"data",
+	"check",
+	"extra",
+}
+
+func (r PixelRole) String() string {
+	if Position <= r && r <= Check {
+		return roles[r]
+	}
+	return strconv.Itoa(int(r))
+}
+
+// A Level represents a QR error correction level.
+// From least to most tolerant of errors, they are L, M, Q, H.
+type Level int
+
+const (
+	L Level = iota
+	M
+	Q
+	H
+)
+
+func (l Level) String() string {
+	if L <= l && l <= H {
+		return "LMQH"[l : l+1]
+	}
+	return strconv.Itoa(int(l))
+}
+
+// A Code is a square pixel grid.
+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
+}
+
+func (c *Code) Black(x, y int) bool {
+	return 0 <= x && x < c.Size && 0 <= y && y < c.Size &&
+		c.Bitmap[y*c.Stride+x/8]&(1<<uint(7-x&7)) != 0
+}
+
+// A Mask describes a mask that is applied to the QR
+// code to avoid QR artifacts being interpreted as
+// alignment and timing patterns (such as the squares
+// in the corners).  Valid masks are integers from 0 to 7.
+type Mask int
+
+// http://www.swetake.com/qr/qr5_en.html
+var mfunc = []func(int, int) bool{
+	func(i, j int) bool { return (i+j)%2 == 0 },
+	func(i, j int) bool { return i%2 == 0 },
+	func(i, j int) bool { return j%3 == 0 },
+	func(i, j int) bool { return (i+j)%3 == 0 },
+	func(i, j int) bool { return (i/2+j/3)%2 == 0 },
+	func(i, j int) bool { return i*j%2+i*j%3 == 0 },
+	func(i, j int) bool { return (i*j%2+i*j%3)%2 == 0 },
+	func(i, j int) bool { return (i*j%3+(i+j)%2)%2 == 0 },
+}
+
+func (m Mask) Invert(y, x int) bool {
+	if m < 0 {
+		return false
+	}
+	return mfunc[m](y, x)
+}
+
+// A Plan describes how to construct a QR code
+// with a specific version, level, and mask.
+type Plan struct {
+	Version Version
+	Level   Level
+	Mask    Mask
+
+	DataBytes  int // number of data bytes
+	CheckBytes int // number of error correcting (checksum) bytes
+	Blocks     int // number of data blocks
+
+	Pixel [][]Pixel // pixel map
+}
+
+// NewPlan returns a Plan for a QR code with the given
+// version, level, and mask.
+func NewPlan(version Version, level Level, mask Mask) (*Plan, error) {
+	p, err := vplan(version)
+	if err != nil {
+		return nil, err
+	}
+	if err := fplan(level, mask, p); err != nil {
+		return nil, err
+	}
+	if err := lplan(version, level, p); err != nil {
+		return nil, err
+	}
+	if err := mplan(mask, p); err != nil {
+		return nil, err
+	}
+	return p, nil
+}
+
+func (b *Bits) Pad(n int) {
+	if n < 0 {
+		panic("qr: invalid pad size")
+	}
+	if n <= 4 {
+		b.Write(0, n)
+	} else {
+		b.Write(0, 4)
+		n -= 4
+		n -= -b.Bits() & 7
+		b.Write(0, -b.Bits()&7)
+		pad := n / 8
+		for i := 0; i < pad; i += 2 {
+			b.Write(0xec, 8)
+			if i+1 >= pad {
+				break
+			}
+			b.Write(0x11, 8)
+		}
+	}
+}
+
+func (b *Bits) AddCheckBytes(v Version, l Level) {
+	nd := v.DataBytes(l)
+	if b.nbit < nd*8 {
+		b.Pad(nd*8 - b.nbit)
+	}
+	if b.nbit != nd*8 {
+		panic("qr: too much data")
+	}
+
+	dat := b.Bytes()
+	vt := &vtab[v]
+	lev := &vt.level[l]
+	db := nd / lev.nblock
+	extra := nd % lev.nblock
+	chk := make([]byte, lev.check)
+	rs := gf256.NewRSEncoder(Field, lev.check)
+	for i := 0; i < lev.nblock; i++ {
+		if i == lev.nblock-extra {
+			db++
+		}
+		rs.ECC(dat[:db], chk)
+		b.Append(chk)
+		dat = dat[db:]
+	}
+
+	if len(b.Bytes()) != vt.bytes {
+		panic("qr: internal error")
+	}
+}
+
+func (p *Plan) Encode(text ...Encoding) (*Code, error) {
+	var b Bits
+	for _, t := range text {
+		if err := t.Check(); err != nil {
+			return nil, err
+		}
+		t.Encode(&b, p.Version)
+	}
+	if b.Bits() > p.DataBytes*8 {
+		return nil, fmt.Errorf("cannot encode %d bits into %d-bit code", b.Bits(), p.DataBytes*8)
+	}
+	b.AddCheckBytes(p.Version, p.Level)
+	bytes := b.Bytes()
+
+	// Now we have the checksum bytes and the data bytes.
+	// Construct the actual code.
+	c := &Code{Size: len(p.Pixel), Stride: (len(p.Pixel) + 7) &^ 7}
+	c.Bitmap = make([]byte, c.Stride*c.Size)
+	crow := c.Bitmap
+	for _, row := range p.Pixel {
+		for x, pix := range row {
+			switch pix.Role() {
+			case Data, Check:
+				o := pix.Offset()
+				if bytes[o/8]&(1<<uint(7-o&7)) != 0 {
+					pix ^= Black
+				}
+			}
+			if pix&Black != 0 {
+				crow[x/8] |= 1 << uint(7-x&7)
+			}
+		}
+		crow = crow[c.Stride:]
+	}
+	return c, nil
+}
+
+// A version describes metadata associated with a version.
+type version struct {
+	apos    int
+	astride int
+	bytes   int
+	pattern int
+	level   [4]level
+}
+
+type level struct {
+	nblock int
+	check  int
+}
+
+var vtab = []version{
+	{},
+	{100, 100, 26, 0x0, [4]level{{1, 7}, {1, 10}, {1, 13}, {1, 17}}},          // 1
+	{16, 100, 44, 0x0, [4]level{{1, 10}, {1, 16}, {1, 22}, {1, 28}}},          // 2
+	{20, 100, 70, 0x0, [4]level{{1, 15}, {1, 26}, {2, 18}, {2, 22}}},          // 3
+	{24, 100, 100, 0x0, [4]level{{1, 20}, {2, 18}, {2, 26}, {4, 16}}},         // 4
+	{28, 100, 134, 0x0, [4]level{{1, 26}, {2, 24}, {4, 18}, {4, 22}}},         // 5
+	{32, 100, 172, 0x0, [4]level{{2, 18}, {4, 16}, {4, 24}, {4, 28}}},         // 6
+	{20, 16, 196, 0x7c94, [4]level{{2, 20}, {4, 18}, {6, 18}, {5, 26}}},       // 7
+	{22, 18, 242, 0x85bc, [4]level{{2, 24}, {4, 22}, {6, 22}, {6, 26}}},       // 8
+	{24, 20, 292, 0x9a99, [4]level{{2, 30}, {5, 22}, {8, 20}, {8, 24}}},       // 9
+	{26, 22, 346, 0xa4d3, [4]level{{4, 18}, {5, 26}, {8, 24}, {8, 28}}},       // 10
+	{28, 24, 404, 0xbbf6, [4]level{{4, 20}, {5, 30}, {8, 28}, {11, 24}}},      // 11
+	{30, 26, 466, 0xc762, [4]level{{4, 24}, {8, 22}, {10, 26}, {11, 28}}},     // 12
+	{32, 28, 532, 0xd847, [4]level{{4, 26}, {9, 22}, {12, 24}, {16, 22}}},     // 13
+	{24, 20, 581, 0xe60d, [4]level{{4, 30}, {9, 24}, {16, 20}, {16, 24}}},     // 14
+	{24, 22, 655, 0xf928, [4]level{{6, 22}, {10, 24}, {12, 30}, {18, 24}}},    // 15
+	{24, 24, 733, 0x10b78, [4]level{{6, 24}, {10, 28}, {17, 24}, {16, 30}}},   // 16
+	{28, 24, 815, 0x1145d, [4]level{{6, 28}, {11, 28}, {16, 28}, {19, 28}}},   // 17
+	{28, 26, 901, 0x12a17, [4]level{{6, 30}, {13, 26}, {18, 28}, {21, 28}}},   // 18
+	{28, 28, 991, 0x13532, [4]level{{7, 28}, {14, 26}, {21, 26}, {25, 26}}},   // 19
+	{32, 28, 1085, 0x149a6, [4]level{{8, 28}, {16, 26}, {20, 30}, {25, 28}}},  // 20
+	{26, 22, 1156, 0x15683, [4]level{{8, 28}, {17, 26}, {23, 28}, {25, 30}}},  // 21
+	{24, 24, 1258, 0x168c9, [4]level{{9, 28}, {17, 28}, {23, 30}, {34, 24}}},  // 22
+	{28, 24, 1364, 0x177ec, [4]level{{9, 30}, {18, 28}, {25, 30}, {30, 30}}},  // 23
+	{26, 26, 1474, 0x18ec4, [4]level{{10, 30}, {20, 28}, {27, 30}, {32, 30}}}, // 24
+	{30, 26, 1588, 0x191e1, [4]level{{12, 26}, {21, 28}, {29, 30}, {35, 30}}}, // 25
+	{28, 28, 1706, 0x1afab, [4]level{{12, 28}, {23, 28}, {34, 28}, {37, 30}}}, // 26
+	{32, 28, 1828, 0x1b08e, [4]level{{12, 30}, {25, 28}, {34, 30}, {40, 30}}}, // 27
+	{24, 24, 1921, 0x1cc1a, [4]level{{13, 30}, {26, 28}, {35, 30}, {42, 30}}}, // 28
+	{28, 24, 2051, 0x1d33f, [4]level{{14, 30}, {28, 28}, {38, 30}, {45, 30}}}, // 29
+	{24, 26, 2185, 0x1ed75, [4]level{{15, 30}, {29, 28}, {40, 30}, {48, 30}}}, // 30
+	{28, 26, 2323, 0x1f250, [4]level{{16, 30}, {31, 28}, {43, 30}, {51, 30}}}, // 31
+	{32, 26, 2465, 0x209d5, [4]level{{17, 30}, {33, 28}, {45, 30}, {54, 30}}}, // 32
+	{28, 28, 2611, 0x216f0, [4]level{{18, 30}, {35, 28}, {48, 30}, {57, 30}}}, // 33
+	{32, 28, 2761, 0x228ba, [4]level{{19, 30}, {37, 28}, {51, 30}, {60, 30}}}, // 34
+	{28, 24, 2876, 0x2379f, [4]level{{19, 30}, {38, 28}, {53, 30}, {63, 30}}}, // 35
+	{22, 26, 3034, 0x24b0b, [4]level{{20, 30}, {40, 28}, {56, 30}, {66, 30}}}, // 36
+	{26, 26, 3196, 0x2542e, [4]level{{21, 30}, {43, 28}, {59, 30}, {70, 30}}}, // 37
+	{30, 26, 3362, 0x26a64, [4]level{{22, 30}, {45, 28}, {62, 30}, {74, 30}}}, // 38
+	{24, 28, 3532, 0x27541, [4]level{{24, 30}, {47, 28}, {65, 30}, {77, 30}}}, // 39
+	{28, 28, 3706, 0x28c69, [4]level{{25, 30}, {49, 28}, {68, 30}, {81, 30}}}, // 40
+}
+
+func grid(siz int) [][]Pixel {
+	m := make([][]Pixel, siz)
+	pix := make([]Pixel, siz*siz)
+	for i := range m {
+		m[i], pix = pix[:siz], pix[siz:]
+	}
+	return m
+}
+
+// vplan creates a Plan for the given version.
+func vplan(v Version) (*Plan, error) {
+	p := &Plan{Version: v}
+	if v < 1 || v > 40 {
+		return nil, fmt.Errorf("invalid QR version %d", int(v))
+	}
+	siz := 17 + int(v)*4
+	m := grid(siz)
+	p.Pixel = m
+
+	// Timing markers (overwritten by boxes).
+	const ti = 6 // timing is in row/column 6 (counting from 0)
+	for i := range m {
+		p := Timing.Pixel()
+		if i&1 == 0 {
+			p |= Black
+		}
+		m[i][ti] = p
+		m[ti][i] = p
+	}
+
+	// Position boxes.
+	posBox(m, 0, 0)
+	posBox(m, siz-7, 0)
+	posBox(m, 0, siz-7)
+
+	// Alignment boxes.
+	info := &vtab[v]
+	for x := 4; x+5 < siz; {
+		for y := 4; y+5 < siz; {
+			// don't overwrite timing markers
+			if (x < 7 && y < 7) || (x < 7 && y+5 >= siz-7) || (x+5 >= siz-7 && y < 7) {
+			} else {
+				alignBox(m, x, y)
+			}
+			if y == 4 {
+				y = info.apos
+			} else {
+				y += info.astride
+			}
+		}
+		if x == 4 {
+			x = info.apos
+		} else {
+			x += info.astride
+		}
+	}
+
+	// Version pattern.
+	pat := vtab[v].pattern
+	if pat != 0 {
+		v := pat
+		for x := 0; x < 6; x++ {
+			for y := 0; y < 3; y++ {
+				p := PVersion.Pixel()
+				if v&1 != 0 {
+					p |= Black
+				}
+				m[siz-11+y][x] = p
+				m[x][siz-11+y] = p
+				v >>= 1
+			}
+		}
+	}
+
+	// One lonely black pixel
+	m[siz-8][8] = Unused.Pixel() | Black
+
+	return p, nil
+}
+
+// fplan adds the format pixels
+func fplan(l Level, m Mask, p *Plan) error {
+	// Format pixels.
+	fb := uint32(l^1) << 13 // level: L=01, M=00, Q=11, H=10
+	fb |= uint32(m) << 10   // mask
+	const formatPoly = 0x537
+	rem := fb
+	for i := 14; i >= 10; i-- {
+		if rem&(1<<uint(i)) != 0 {
+			rem ^= formatPoly << uint(i-10)
+		}
+	}
+	fb |= rem
+	invert := uint32(0x5412)
+	siz := len(p.Pixel)
+	for i := uint(0); i < 15; i++ {
+		pix := Format.Pixel() + OffsetPixel(i)
+		if (fb>>i)&1 == 1 {
+			pix |= Black
+		}
+		if (invert>>i)&1 == 1 {
+			pix ^= Invert | Black
+		}
+		// top left
+		switch {
+		case i < 6:
+			p.Pixel[i][8] = pix
+		case i < 8:
+			p.Pixel[i+1][8] = pix
+		case i < 9:
+			p.Pixel[8][7] = pix
+		default:
+			p.Pixel[8][14-i] = pix
+		}
+		// bottom right
+		switch {
+		case i < 8:
+			p.Pixel[8][siz-1-int(i)] = pix
+		default:
+			p.Pixel[siz-1-int(14-i)][8] = pix
+		}
+	}
+	return nil
+}
+
+// lplan edits a version-only Plan to add information
+// about the error correction levels.
+func lplan(v Version, l Level, p *Plan) error {
+	p.Level = l
+
+	nblock := vtab[v].level[l].nblock
+	ne := vtab[v].level[l].check
+	nde := (vtab[v].bytes - ne*nblock) / nblock
+	extra := (vtab[v].bytes - ne*nblock) % nblock
+	dataBits := (nde*nblock + extra) * 8
+	checkBits := ne * nblock * 8
+
+	p.DataBytes = vtab[v].bytes - ne*nblock
+	p.CheckBytes = ne * nblock
+	p.Blocks = nblock
+
+	// Make data + checksum pixels.
+	data := make([]Pixel, dataBits)
+	for i := range data {
+		data[i] = Data.Pixel() | OffsetPixel(uint(i))
+	}
+	check := make([]Pixel, checkBits)
+	for i := range check {
+		check[i] = Check.Pixel() | OffsetPixel(uint(i+dataBits))
+	}
+
+	// Split into blocks.
+	dataList := make([][]Pixel, nblock)
+	checkList := make([][]Pixel, nblock)
+	for i := 0; i < nblock; i++ {
+		// The last few blocks have an extra data byte (8 pixels).
+		nd := nde
+		if i >= nblock-extra {
+			nd++
+		}
+		dataList[i], data = data[0:nd*8], data[nd*8:]
+		checkList[i], check = check[0:ne*8], check[ne*8:]
+	}
+	if len(data) != 0 || len(check) != 0 {
+		panic("data/check math")
+	}
+
+	// Build up bit sequence, taking first byte of each block,
+	// then second byte, and so on.  Then checksums.
+	bits := make([]Pixel, dataBits+checkBits)
+	dst := bits
+	for i := 0; i < nde+1; i++ {
+		for _, b := range dataList {
+			if i*8 < len(b) {
+				copy(dst, b[i*8:(i+1)*8])
+				dst = dst[8:]
+			}
+		}
+	}
+	for i := 0; i < ne; i++ {
+		for _, b := range checkList {
+			if i*8 < len(b) {
+				copy(dst, b[i*8:(i+1)*8])
+				dst = dst[8:]
+			}
+		}
+	}
+	if len(dst) != 0 {
+		panic("dst math")
+	}
+
+	// Sweep up pair of columns,
+	// then down, assigning to right then left pixel.
+	// Repeat.
+	// See Figure 2 of http://www.pclviewer.com/rs2/qrtopology.htm
+	siz := len(p.Pixel)
+	rem := make([]Pixel, 7)
+	for i := range rem {
+		rem[i] = Extra.Pixel()
+	}
+	src := append(bits, rem...)
+	for x := siz; x > 0; {
+		for y := siz - 1; y >= 0; y-- {
+			if p.Pixel[y][x-1].Role() == 0 {
+				p.Pixel[y][x-1], src = src[0], src[1:]
+			}
+			if p.Pixel[y][x-2].Role() == 0 {
+				p.Pixel[y][x-2], src = src[0], src[1:]
+			}
+		}
+		x -= 2
+		if x == 7 { // vertical timing strip
+			x--
+		}
+		for y := 0; y < siz; y++ {
+			if p.Pixel[y][x-1].Role() == 0 {
+				p.Pixel[y][x-1], src = src[0], src[1:]
+			}
+			if p.Pixel[y][x-2].Role() == 0 {
+				p.Pixel[y][x-2], src = src[0], src[1:]
+			}
+		}
+		x -= 2
+	}
+	return nil
+}
+
+// mplan edits a version+level-only Plan to add the mask.
+func mplan(m Mask, p *Plan) error {
+	p.Mask = m
+	for y, row := range p.Pixel {
+		for x, pix := range row {
+			if r := pix.Role(); (r == Data || r == Check || r == Extra) && p.Mask.Invert(y, x) {
+				row[x] ^= Black | Invert
+			}
+		}
+	}
+	return nil
+}
+
+// posBox draws a position (large) box at upper left x, y.
+func posBox(m [][]Pixel, x, y int) {
+	pos := Position.Pixel()
+	// box
+	for dy := 0; dy < 7; dy++ {
+		for dx := 0; dx < 7; dx++ {
+			p := pos
+			if dx == 0 || dx == 6 || dy == 0 || dy == 6 || 2 <= dx && dx <= 4 && 2 <= dy && dy <= 4 {
+				p |= Black
+			}
+			m[y+dy][x+dx] = p
+		}
+	}
+	// white border
+	for dy := -1; dy < 8; dy++ {
+		if 0 <= y+dy && y+dy < len(m) {
+			if x > 0 {
+				m[y+dy][x-1] = pos
+			}
+			if x+7 < len(m) {
+				m[y+dy][x+7] = pos
+			}
+		}
+	}
+	for dx := -1; dx < 8; dx++ {
+		if 0 <= x+dx && x+dx < len(m) {
+			if y > 0 {
+				m[y-1][x+dx] = pos
+			}
+			if y+7 < len(m) {
+				m[y+7][x+dx] = pos
+			}
+		}
+	}
+}
+
+// alignBox draw an alignment (small) box at upper left x, y.
+func alignBox(m [][]Pixel, x, y int) {
+	// box
+	align := Alignment.Pixel()
+	for dy := 0; dy < 5; dy++ {
+		for dx := 0; dx < 5; dx++ {
+			p := align
+			if dx == 0 || dx == 4 || dy == 0 || dy == 4 || dx == 2 && dy == 2 {
+				p |= Black
+			}
+			m[y+dy][x+dx] = p
+		}
+	}
+}
-- 
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