/var/www/greso.tech/server/nsm/node_modules/qrcode/lib/core
Edit: /var/www/greso.tech/server/nsm/node_modules/qrcode/lib/core/galois-field.js (1899B)
const EXP_TABLE = new Uint8Array(512)
const LOG_TABLE = new Uint8Array(256)
/**
* Precompute the log and anti-log tables for faster computation later
*
* For each possible value in the galois field 2^8, we will pre-compute
* the logarithm and anti-logarithm (exponential) of this value
*
* ref {@link https://en.wikiversity.org/wiki/Reed%E2%80%93Solomon_codes_for_coders#Introduction_to_mathematical_fields}
*/
;(function initTables () {
let x = 1
for (let i = 0; i < 255; i++) {
EXP_TABLE[i] = x
LOG_TABLE[x] = i
x <<= 1 // multiply by 2
// The QR code specification says to use byte-wise modulo 100011101 arithmetic.
// This means that when a number is 256 or larger, it should be XORed with 0x11D.
if (x & 0x100) { // similar to x >= 256, but a lot faster (because 0x100 == 256)
x ^= 0x11D
}
}
// Optimization: double the size of the anti-log table so that we don't need to mod 255 to
// stay inside the bounds (because we will mainly use this table for the multiplication of
// two GF numbers, no more).
// @see {@link mul}
for (let i = 255; i < 512; i++) {
EXP_TABLE[i] = EXP_TABLE[i - 255]
}
}())
/**
* Returns log value of n inside Galois Field
*
* @param {Number} n
* @return {Number}
*/
exports.log = function log (n) {
if (n < 1) throw new Error('log(' + n + ')')
return LOG_TABLE[n]
}
/**
* Returns anti-log value of n inside Galois Field
*
* @param {Number} n
* @return {Number}
*/
exports.exp = function exp (n) {
return EXP_TABLE[n]
}
/**
* Multiplies two number inside Galois Field
*
* @param {Number} x
* @param {Number} y
* @return {Number}
*/
exports.mul = function mul (x, y) {
if (x === 0 || y === 0) return 0
// should be EXP_TABLE[(LOG_TABLE[x] + LOG_TABLE[y]) % 255] if EXP_TABLE wasn't oversized
// @see {@link initTables}
return EXP_TABLE[LOG_TABLE[x] + LOG_TABLE[y]]
}