<?php

namespace PHPModbus;

/**
 * Phpmodbus Copyright (c) 2004, 2013 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, 2013 Jan Krakora
 * @license   PhpModbus license
 * @category  Phpmodbus
 * @package   Phpmodbus
 * @version   $id$
 */

/**
 * IecType
 *
 * The class includes set of IEC-1131 data type functions that converts a PHP
 * data types to a IEC data type.
 *
 * @author     Jan Krakora
 * @copyright  Copyright (c) 2004, 2010 Jan Krakora
 * @package    Phpmodbus
 */
class IecType
{
	/**
	 * iecBYTE
	 *
	 * Converts a value to IEC-1131 BYTE data type
	 *
	 * @param int $value from 0 to 255
	 * @return int IEC BYTE data type
	 *
	 */
	public static function iecBYTE($value)
	{
		return chr($value & 0xFF);
	}

	/**
	 * iecINT
	 *
	 * Converts a value to IEC-1131 INT data type
	 *
	 * @param int $value to be converted
	 * @return int IEC-1131 INT data type
	 *
	 */
	public static function iecINT($value)
	{
		return self::iecBYTE(($value >> 8) & 0x00FF) .
		self::iecBYTE(($value & 0x00FF));
	}

	/**
	 * iecDINT
	 *
	 * Converts a value to IEC-1131 DINT data type
	 *
	 * @param int $value     to be converted
	 * @param int $bigEndian defines endian codding (little endian == 0, big endian == 1)
	 * @return int IEC-1131 INT data type
	 *
	 */
	public static function iecDINT($value, $bigEndian = 0)
	{
		// result with right endianness
		return self::endianness($value, $bigEndian);
	}

	/**
	 * iecREAL
	 *
	 * Converts a value to IEC-1131 REAL data type. The function uses function  @use float2iecReal.
	 *
	 * @param int  $value     to be converted
	 * @param bool $bigEndian defines endian codding (little endian == 0, big endian == 1)
	 * @return int IEC-1131 REAL data type
	 */
	public static function iecREAL($value, $bigEndian = 0)
	{
		// iecREAL representation
		$real = self::float2iecReal($value);
		// result with right endianness
		return self::endianness($real, $bigEndian);
	}

	/**
	 * float2iecReal
	 *
	 * This function converts float value to IEC-1131 REAL single precision form.
	 *
	 * 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 float $value to be converted
	 * @return int IEC REAL data type
	 */
	private static function float2iecReal($value)
	{
		// get float binary string
		$float = pack("f", $value);
		// set 32-bit unsigned integer of the float
		$w = unpack("L", $float);
		return $w[1];
	}

	/**
	 * endianness
	 *
	 * Make endianess as required.
	 * For more see http://en.wikipedia.org/wiki/Endianness
	 *
	 * @param int  $value
	 * @param bool $bigEndian
	 * @return int
	 */
	private static function endianness($value, $bigEndian = 0)
	{
		if ($bigEndian == 0) {
			return
				self::iecBYTE(($value >> 8) & 0x000000FF) .
				self::iecBYTE(($value & 0x000000FF)) .
				self::iecBYTE(($value >> 24) & 0x000000FF) .
				self::iecBYTE(($value >> 16) & 0x000000FF);
		} else {
			return
				self::iecBYTE(($value >> 24) & 0x000000FF) .
				self::iecBYTE(($value >> 16) & 0x000000FF) .
				self::iecBYTE(($value >> 8) & 0x000000FF) .
				self::iecBYTE(($value & 0x000000FF));
		}
	}
}