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authorWim <wim@42.be>2022-03-20 02:20:54 +0100
committerWim <wim@42.be>2022-03-20 14:57:48 +0100
commit496d5b4ec7f5f4afae6199f928675d14d18de015 (patch)
tree3a649c80a76f0ffc33e6b3a63c0e65e892169cde /vendor/github.com/skip2/go-qrcode/reedsolomon/reed_solomon.go
parent2623a412c42a81104b97ae8c81a5f66760fee4b6 (diff)
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Add whatsappmulti buildflag for whatsapp with multidevice support (whatsapp)
Diffstat (limited to 'vendor/github.com/skip2/go-qrcode/reedsolomon/reed_solomon.go')
-rw-r--r--vendor/github.com/skip2/go-qrcode/reedsolomon/reed_solomon.go73
1 files changed, 73 insertions, 0 deletions
diff --git a/vendor/github.com/skip2/go-qrcode/reedsolomon/reed_solomon.go b/vendor/github.com/skip2/go-qrcode/reedsolomon/reed_solomon.go
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@@ -0,0 +1,73 @@
+// go-qrcode
+// Copyright 2014 Tom Harwood
+
+// Package reedsolomon provides error correction encoding for QR Code 2005.
+//
+// QR Code 2005 uses a Reed-Solomon error correcting code to detect and correct
+// errors encountered during decoding.
+//
+// The generated RS codes are systematic, and consist of the input data with
+// error correction bytes appended.
+package reedsolomon
+
+import (
+ "log"
+
+ bitset "github.com/skip2/go-qrcode/bitset"
+)
+
+// Encode data for QR Code 2005 using the appropriate Reed-Solomon code.
+//
+// numECBytes is the number of error correction bytes to append, and is
+// determined by the target QR Code's version and error correction level.
+//
+// ISO/IEC 18004 table 9 specifies the numECBytes required. e.g. a 1-L code has
+// numECBytes=7.
+func Encode(data *bitset.Bitset, numECBytes int) *bitset.Bitset {
+ // Create a polynomial representing |data|.
+ //
+ // The bytes are interpreted as the sequence of coefficients of a polynomial.
+ // The last byte's value becomes the x^0 coefficient, the second to last
+ // becomes the x^1 coefficient and so on.
+ ecpoly := newGFPolyFromData(data)
+ ecpoly = gfPolyMultiply(ecpoly, newGFPolyMonomial(gfOne, numECBytes))
+
+ // Pick the generator polynomial.
+ generator := rsGeneratorPoly(numECBytes)
+
+ // Generate the error correction bytes.
+ remainder := gfPolyRemainder(ecpoly, generator)
+
+ // Combine the data & error correcting bytes.
+ // The mathematically correct answer is:
+ //
+ // result := gfPolyAdd(ecpoly, remainder).
+ //
+ // The encoding used by QR Code 2005 is slightly different this result: To
+ // preserve the original |data| bit sequence exactly, the data and remainder
+ // are combined manually below. This ensures any most significant zero bits
+ // are preserved (and not optimised away).
+ result := bitset.Clone(data)
+ result.AppendBytes(remainder.data(numECBytes))
+
+ return result
+}
+
+// rsGeneratorPoly returns the Reed-Solomon generator polynomial with |degree|.
+//
+// The generator polynomial is calculated as:
+// (x + a^0)(x + a^1)...(x + a^degree-1)
+func rsGeneratorPoly(degree int) gfPoly {
+ if degree < 2 {
+ log.Panic("degree < 2")
+ }
+
+ generator := gfPoly{term: []gfElement{1}}
+
+ for i := 0; i < degree; i++ {
+ nextPoly := gfPoly{term: []gfElement{gfExpTable[i], 1}}
+ generator = gfPolyMultiply(generator, nextPoly)
+ }
+
+ return generator
+}