getid3_lib::BigEndian2Float

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Summery Summery

ANSI/IEEE Standard 754-1985, Standard for Binary Floating Point Arithmetic

Syntax Syntax

getid3_lib::BigEndian2Float( string $byteword )

Parameters Parameters

$byteword

(string) (Required)

Return Return

(float|false)

Source Source

File: wp-includes/ID3/getid3.lib.php

		$bitword = self::BigEndian2Bin($byteword);
		if (!$bitword) {
			return 0;
		}
		$signbit = $bitword[0];
		$floatvalue = 0;
		$exponentbits = 0;
		$fractionbits = 0;

		switch (strlen($byteword) * 8) {
			case 32:
				$exponentbits = 8;
				$fractionbits = 23;
				break;

			case 64:
				$exponentbits = 11;
				$fractionbits = 52;
				break;

			case 80:
				// 80-bit Apple SANE format
				// http://www.mactech.com/articles/mactech/Vol.06/06.01/SANENormalized/
				$exponentstring = substr($bitword, 1, 15);
				$isnormalized = intval($bitword[16]);
				$fractionstring = substr($bitword, 17, 63);
				$exponent = pow(2, self::Bin2Dec($exponentstring) - 16383);
				$fraction = $isnormalized + self::DecimalBinary2Float($fractionstring);
				$floatvalue = $exponent * $fraction;
				if ($signbit == '1') {
					$floatvalue *= -1;
				}
				return $floatvalue;

			default:
				return false;
		}
		$exponentstring = substr($bitword, 1, $exponentbits);
		$fractionstring = substr($bitword, $exponentbits + 1, $fractionbits);
		$exponent = self::Bin2Dec($exponentstring);
		$fraction = self::Bin2Dec($fractionstring);

		if (($exponent == (pow(2, $exponentbits) - 1)) && ($fraction != 0)) {
			// Not a Number
			$floatvalue = false;
		} elseif (($exponent == (pow(2, $exponentbits) - 1)) && ($fraction == 0)) {
			if ($signbit == '1') {
				$floatvalue = '-infinity';
			} else {
				$floatvalue = '+infinity';
			}
		} elseif (($exponent == 0) && ($fraction == 0)) {
			if ($signbit == '1') {
				$floatvalue = -0;
			} else {
				$floatvalue = 0;
			}
			$floatvalue = ($signbit ? 0 : -0);
		} elseif (($exponent == 0) && ($fraction != 0)) {
			// These are 'unnormalized' values
			$floatvalue = pow(2, (-1 * (pow(2, $exponentbits - 1) - 2))) * self::DecimalBinary2Float($fractionstring);
			if ($signbit == '1') {
				$floatvalue *= -1;
			}
		} elseif ($exponent != 0) {
			$floatvalue = pow(2, ($exponent - (pow(2, $exponentbits - 1) - 1))) * (1 + self::DecimalBinary2Float($fractionstring));
			if ($signbit == '1') {
				$floatvalue *= -1;
			}
		}
		return (float) $floatvalue;
	}

	/**
	 * @param string $byteword

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