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author | Wim <wim@42.be> | 2022-03-20 02:20:54 +0100 |
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committer | Wim <wim@42.be> | 2022-03-20 14:57:48 +0100 |
commit | 496d5b4ec7f5f4afae6199f928675d14d18de015 (patch) | |
tree | 3a649c80a76f0ffc33e6b3a63c0e65e892169cde /vendor/github.com/skip2/go-qrcode/reedsolomon/reed_solomon.go | |
parent | 2623a412c42a81104b97ae8c81a5f66760fee4b6 (diff) | |
download | matterbridge-msglm-496d5b4ec7f5f4afae6199f928675d14d18de015.tar.gz matterbridge-msglm-496d5b4ec7f5f4afae6199f928675d14d18de015.tar.bz2 matterbridge-msglm-496d5b4ec7f5f4afae6199f928675d14d18de015.zip |
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.go | 73 |
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 new file mode 100644 index 00000000..561697b4 --- /dev/null +++ b/vendor/github.com/skip2/go-qrcode/reedsolomon/reed_solomon.go @@ -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 +} |