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ReadHoldingRegistersRequest.php
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ReadHoldingRegistersRequest.php
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<?php
declare(strict_types=1);
namespace ModbusTcpClient\Packet\ModbusFunction;
use ModbusTcpClient\Exception\InvalidArgumentException;
use ModbusTcpClient\Packet\ErrorResponse;
use ModbusTcpClient\Packet\ModbusPacket;
use ModbusTcpClient\Packet\ModbusRequest;
use ModbusTcpClient\Packet\ProtocolDataUnitRequest;
use ModbusTcpClient\Utils\Endian;
use ModbusTcpClient\Utils\Types;
/**
* Request for Read Holding Registers (FC=03)
*
* Example packet: \x00\x01\x00\x00\x00\x06\x01\x03\x00\x6B\x00\x01
* \x00\x01 - transaction id
* \x00\x00 - protocol id
* \x00\x06 - number of bytes in the message (PDU = ProtocolDataUnit) to follow
* \x01 - unit id
* \x03 - function code
* \x00\x6B - start address
* \x00\x01 - holding registers quantity to return
*
*/
class ReadHoldingRegistersRequest extends ProtocolDataUnitRequest implements ModbusRequest
{
/**
* @var int total number of registers (words) requested. Size 2 bytes
*/
private int $quantity;
public function __construct(int $startAddress, int $quantity, int $unitId = 0, int $transactionId = null)
{
parent::__construct($startAddress, $unitId, $transactionId);
$this->quantity = $quantity;
$this->validate();
}
public function validate(): void
{
parent::validate();
if (($this->quantity > 0 && $this->quantity <= 124)) {
return;
}
throw new InvalidArgumentException("quantity is not set or out of range (0-124): {$this->quantity}", 3);
}
public function getFunctionCode(): int
{
return ModbusPacket::READ_HOLDING_REGISTERS;
}
public function __toString(): string
{
return parent::__toString()
. Types::toRegister($this->getQuantity());
}
/**
* @return int
*/
public function getQuantity(): int
{
return $this->quantity;
}
protected function getLengthInternal(): int
{
return parent::getLengthInternal() + 2; // quantity size (2 bytes)
}
/**
* Parses binary string to ReadHoldingRegistersRequest or return ErrorResponse on failure
*
* @param string $binaryString
* @return ReadHoldingRegistersRequest|ErrorResponse
*/
public static function parse(string $binaryString): ErrorResponse|ReadHoldingRegistersRequest
{
return self::parseStartAddressPacket(
$binaryString,
12,
ModbusPacket::READ_HOLDING_REGISTERS,
function (int $transactionId, int $unitId, int $startAddress) use ($binaryString) {
$quantity = Types::parseUInt16($binaryString[10] . $binaryString[11], Endian::BIG_ENDIAN);
return new self($startAddress, $quantity, $unitId, $transactionId);
}
);
}
}