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CRC calculations
function crc16($string, $crc = 0) {
for($x = 0; $x < strlen($string); $x++) {
$crc = $crc ^ ord($string[$x]);
echo $crc . '<br />';
for($y = 0; $y < 8; $y++) {
if(($crc & 0x0001) == 0x0001) {
$crc = (($crc >> 1) ^ 0x10589);
}
else {
$crc = $crc >> 1;
}
}
}
return $crc;
}
function crc16_2($string) {
$crc = 0;
for($x = 0; $x < strlen($string); $x++) {
$crc = $crc ^ ord($string[$x]);
for($y = 0; $y < 8; $y++) {
if(($crc & 0x0001) == 0x0001) {
$crc = (($crc >> 1) ^ 0x8408);
}
else {
$crc = $crc >> 1;
}
}
}
$lb = ($crc & 0xff00) >> 8;
$hb = ($crc & 0x00ff) << 8;
$crc = $hb | $lb;
return $crc;
}
function crc16_3($data) {
$crc = 0xFFFF;
for($i = 0; $i < strlen($data); $i++) {
$x = (($crc >> 8) ^ ord($data[$i])) & 0xFF;
$x ^= $x >> 4;
$crc = (($crc << 8) ^ ($x << 12) ^ ($x << 5) ^ $x) & 0xFFFF;
}
return $crc;
}
function crc16_4($string, $crc = 0) {
for($x = 0; $x < strlen($string); $x++) {
$crc = $crc ^ ord($string[$x]);
for($y = 0; $y < 8; $y++) {
if(($crc & 0x0001) == 0x0001) {
$crc = (($crc >> 1) ^ 0xA001);
}
else {
$crc = $crc >> 1;
}
}
}
return $crc;
}
function crc16_5($string) {
$crc = 0xFFFF;
for($x = 0; $x < strlen($string); $x++) {
$crc = $crc ^ ord($string[$x]);
for($y = 0; $y < 8; $y++) {
if(($crc & 0x0001) == 0x0001) {
$crc = (($crc >> 1) ^ 0xA001);
}
else {
$crc = $crc >> 1;
}
}
}
return $crc;
}
function calculate_common_crc16c($buffer) {
$crc16c = 0xffff; // the crc initial value
$buffer_length = strlen($buffer);
for($i = 0; $i < $buffer_length; $i++) {
$ch = ord($buffer[$i]);
$crc16c = update_common_crc16c($ch, $crc16c);
}
return $crc16c;
}
function update_common_crc16c($ch, $crc16c) {
global $crc16c_polynomial;
$ch <<= 8;
for($i = 0; $i < 8; $i++) {
if(($crc16c ^ $ch) & 0x8000) {
$xor_flag = true;
}
else {
$xor_flag = false;
}
$crc16c = $crc16c << 1;
if($xor_flag) {
$crc16c = $crc16c ^ $crc16c_polynomial;
}
$ch = $ch << 1;
}
// mask off (zero out) the upper two bytes
$crc16c = $crc16c & 0x0000ffff;
return $crc16c;
}
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