Created
December 10, 2012 14:55
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CRC calculations
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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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