83 lines
1.6 KiB
JavaScript
83 lines
1.6 KiB
JavaScript
"use strict";
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function UpdateCRC16(crcIn, byte) {
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let crc = crcIn;
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let inNum = byte | 0x100;
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do {
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crc <<= 1;
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crc = crc & 0xFFFFFFFF;
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inNum <<= 1;
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inNum = inNum & 0xFFFFFFFF;
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if (inNum & 0x100) {
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++crc;
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}
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if (crc & 0x10000) {
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crc ^= 0x1021;
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crc = crc & 0xFFFFFFFF;
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}
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} while (!(inNum & 0x10000));
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return crc & 0xffff;
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}
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function crc16(data, size) {
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let crc = 0;
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for (let i = 0; i < size; i++) {
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crc = UpdateCRC16(crc, data[i])
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}
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crc = UpdateCRC16(crc, 0);
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crc = UpdateCRC16(crc, 0);
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return crc & 0xffff;
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}
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function crc16_backup(buf, len) {
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// let crc = 0x0000;
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let crc = 0xFFFF;
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for (let pos = 0; pos < len; pos++) {
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// XOR byte into least sig. byte of crc
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crc ^= buf[pos];
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crc = crc & 0xFFFF;
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for (let i = 8; i != 0; i--) { // Loop over each bit
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if ((crc & 0x0001) != 0) { // If the LSB is set
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crc >>= 1; // Shift right and XOR 0xA001
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crc ^= 0xA001;
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crc = crc & 0xFFFF;
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}
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else {// Else LSB is not set
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crc >>= 1; // Just shift right
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crc = crc & 0xFFFF;
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}
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}
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}
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return crc;
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}
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/*
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int calcrc(char *ptr, int count)
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{
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int crc;
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char i;
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crc = 0;
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while (--count >= 0)
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{
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crc = crc ^ (int) *ptr++ << 8;
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i = 8;
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do
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{
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if (crc & 0x8000)
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crc = crc << 1 ^ 0x1021;
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else
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crc = crc << 1;
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} while(--i);
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}
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return (crc);
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}
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*/
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module.exports = crc16; |