php-modbus/src/PhpType.php

<?php

namespace PHPModbus;
use Exception;

/**
 * Phpmodbus Copyright (c) 2004, 2012 Jan Krakora
 *
 * This source file is subject to the "PhpModbus license" that is bundled
 * with this package in the file license.txt.
 *
 * @author    Jan Krakora
 * @copyright Copyright (c) 2004, 2012 Jan Krakora
 * @license   PhpModbus license
 * @category  Phpmodbus
 * @package   Phpmodbus
 * @version   $id$
 *
 */

/**
 * PhpType
 *
 * The class includes set of methods that convert the received Modbus data
 * (array of bytes) to the PHP data type, i.e. signed int, unsigned int and float.
 *
 * @author     Jan Krakora
 * @copyright  Copyright (c) 2004, 2012 Jan Krakora
 * @package    Phpmodbus
 *
 */
class PhpType
{
	/**
	 * bytes2float
	 *
	 * The function converts array of 4 bytes to float. The return value
	 * depends on order of the input bytes (endianning).
	 *
	 * @param array $values
	 * @param bool  $bigEndian
	 * @return float
	 */
	public static function bytes2float($values, $bigEndian = 0)
	{
		// Set the array to correct form
		$data = self::checkData($values);
		// Combine bytes
		$real = self::combineBytes($data, $bigEndian);
		// Convert the real value to float
		return (float)self::real2float($real);
	}

	/**
	 * bytes2signedInt
	 *
	 * The function converts array of 2 or 4 bytes to signed integer.
	 * The return value depends on order of the input bytes (endianning).
	 *
	 * @param array $values
	 * @param bool  $bigEndian
	 * @return int
	 */
	public static function bytes2signedInt($values, $bigEndian = 0)
	{
		$data = array();
		$int = 0;
		// Set the array to correct form
		$data = self::checkData($values);
		// Combine bytes
		$int = self::combineBytes($data, $bigEndian);
		// In the case of signed 2 byte value convert it to 4 byte one
		if ((count($values) == 2) && ((0x8000 & $int) > 0)) {
			$int = 0xFFFF8000 | $int;
		}
		// Convert the value
		return (int)self::dword2signedInt($int);
	}

	/**
	 * bytes2unsignedInt
	 *
	 * The function converts array of 2 or 4 bytes to unsigned integer.
	 * The return value depends on order of the input bytes (endianning).
	 *
	 * @param array $values
	 * @param bool  $bigEndian
	 * @return int|float
	 */
	public static function bytes2unsignedInt($values, $bigEndian = 0)
	{
		$data = array();
		$int = 0;
		// Set the array to correct form
		$data = self::checkData($values);
		// Combine bytes
		$int = self::combineBytes($data, $bigEndian);
		// Convert the value
		return self::dword2unsignedInt($int);
	}

	/**
	 * bytes2string
	 *
	 * The function converts an values array to the string. The function detects
	 * the end of the string by 0x00 character as defined by string standards.
	 *
	 * @param array $values
	 * @param bool  $bigEndian
	 * @return string
	 */
	public static function bytes2string($values, $bigEndian = 0)
	{
		// Prepare string variable
		$str = "";
		// Parse the received data word array
		for ($i = 0; $i < count($values); $i += 2) {
			if ($bigEndian) {
				if ($values[$i] != 0) {
					$str .= chr($values[$i]);
				} else {
					break;
				}
				if ($values[$i + 1] != 0) {
					$str .= chr($values[$i + 1]);
				} else {
					break;
				}
			} else {
				if ($values[$i + 1] != 0) {
					$str .= chr($values[$i + 1]);
				} else {
					break;
				}
				if ($values[$i] != 0) {
					$str .= chr($values[$i]);
				} else {
					break;
				}
			}
		}
		// return string
		return $str;
	}

	/**
	 * real2float
	 *
	 * This function converts a value in IEC-1131 REAL single precision form to float.
	 *
	 * For more see [{@link http://en.wikipedia.org/wiki/Single_precision Single precision on Wiki}] or
	 * [{@link http://de.php.net/manual/en/function.base-convert.php PHP base_convert function commentary}, Todd Stokes
	 * @ Georgia Tech 21-Nov-2007] or
	 * [{@link http://www.php.net/manual/en/function.pack.php PHP pack/unpack functionality}]
	 *
	 * @param int $value in IEC REAL data type to be converted
	 * @return float float value
	 */
	private static function real2float($value)
	{
		// get unsigned long
		$ulong = pack("L", $value);
		// set float
		$float = unpack("f", $ulong);

		return $float[1];
	}

	/**
	 * dword2signedInt
	 *
	 * Switch double word to signed integer
	 *
	 * @param int $value
	 * @return int
	 */
	private static function dword2signedInt($value)
	{
		if ((0x80000000 & $value) != 0) {
			return -(0x7FFFFFFF & ~$value) - 1;
		} else {
			return (0x7FFFFFFF & $value);
		}
	}

	/**
	 * dword2signedInt
	 *
	 * Switch double word to unsigned integer
	 *
	 * @param int $value
	 * @return int|float
	 */
	private static function dword2unsignedInt($value)
	{
		if ((0x80000000 & $value) != 0) {
			return ((float)(0x7FFFFFFF & $value)) + 2147483648;
		} else {
			return (int)(0x7FFFFFFF & $value);
		}
	}

	/**
	 * checkData
	 *
	 * Check if the data variable is array, and check if the values are numeric
	 *
	 * @param int[] $data
	 * @return int
	 * @throws Exception
	 */
	private static function checkData($data)
	{
		// Check the data
		if (!is_array($data) ||
			count($data) < 2 ||
			count($data) > 4 ||
			count($data) == 3
		) {
			throw new Exception('The input data should be an array of 2 or 4 bytes.');
		}
		// Fill the rest of array by zeroes
		if (count($data) == 2) {
			$data[2] = 0;
			$data[3] = 0;
		}
		// Check the values to be number
		if (!is_numeric($data[0]) ||
			!is_numeric($data[1]) ||
			!is_numeric($data[2]) ||
			!is_numeric($data[3])
		) {
			throw new Exception('Data are not numeric or the array keys are not indexed by 0,1,2 and 3');
		}

		return $data;
	}

	/**
	 * combineBytes
	 *
	 * Combine bytes together
	 *
	 * @param int  $data
	 * @param bool $bigEndian
	 * @return int
	 */
	private static function combineBytes($data, $bigEndian)
	{
		$value = 0;
		// Combine bytes
		if ($bigEndian == 0) {
			$value = (($data[3] & 0xFF) << 16) |
				(($data[2] & 0xFF) << 24) |
				(($data[1] & 0xFF)) |
				(($data[0] & 0xFF) << 8);
		} else {
			$value = (($data[3] & 0xFF) << 24) |
				(($data[2] & 0xFF) << 16) |
				(($data[1] & 0xFF) << 8) |
				(($data[0] & 0xFF));
		}

		return $value;
	}
}