function BigEndian2Float($byteword)
{
// ANSI/IEEE Standard 754-1985, Standard for Binary Floating Point Arithmetic
// http://www.psc.edu/general/software/packages/ieee/ieee.html
// http://www.scri.fsu.edu/~jac/MAD3401/Backgrnd/ieee.html
$bitword = BigEndian2Bin($byteword);
$signbit = $bitword[0];
switch (strlen($byteword) * 8) {
case 32:
$exponentbits = 8;
$fractionbits = 23;
break;
case 64:
$exponentbits = 11;
$fractionbits = 52;
break;
case 80:
$exponentbits = 16;
$fractionbits = 64;
break;
default:
return false;
break;
}
$exponentstring = substr($bitword, 1, $exponentbits - 1);
$fractionstring = substr($bitword, $exponentbits, $fractionbits);
$exponent = Bin2Dec($exponentstring);
$fraction = Bin2Dec($fractionstring);
if ($exponentbits == 16 && $fractionbits == 64) {
// 80-bit
// As used in Apple AIFF for sample_rate
// A bit of a hack, but it works ;)
return pow(2, $exponent - 16382) * DecimalBinary2Float($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, $exponentbits - 1) - 2)) * DecimalBinary2Float($fractionstring);
if ($signbit == '1') {
$floatvalue *= -1;
}
} elseif ($exponent != 0) {
$floatvalue = pow(2, $exponent - (pow(2, $exponentbits - 1) - 1)) * (1 + DecimalBinary2Float($fractionstring));
if ($signbit == '1') {
$floatvalue *= -1;
}
}
return (double) $floatvalue;
}
function BigEndian2Float($byteword)
{
// ANSI/IEEE Standard 754-1985, Standard for Binary Floating Point Arithmetic
// http://www.psc.edu/general/software/packages/ieee/ieee.html
// http://www.scri.fsu.edu/~jac/MAD3401/Backgrnd/ieee.html
$bitword = BigEndian2Bin($byteword);
$signbit = $bitword[0];
if (strlen($byteword) == 4) {
// 32-bit DWORD
$exponentbits = 8;
$fractionbits = 23;
} else {
if (strlen($byteword) == 8) {
// 64-bit QWORD
$exponentbits = 11;
$fractionbits = 52;
} else {
return FALSE;
}
}
$exponentstring = substr($bitword, 1, $exponentbits);
$fractionstring = substr($bitword, 9, $fractionbits);
$exponent = Bin2Dec($exponentstring);
$fraction = Bin2Dec($fractionstring);
if ($exponent == pow(2, $exponentbits) - 1 && $fraction != 0) {
// Not a Number
$floatvalue = FALSE;
} else {
if ($exponent == pow(2, $exponentbits) - 1 && $fraction == 0) {
if ($signbit == '1') {
$floatvalue = '-infinity';
} else {
$floatvalue = '+infinity';
}
} else {
if ($exponent == 0 && $fraction == 0) {
if ($signbit == '1') {
$floatvalue = -0;
} else {
$floatvalue = 0;
}
$floatvalue = $signbit ? 0 : -0;
} else {
if ($exponent == 0 && $fraction != 0) {
// These are 'unnormalized' values
$floatvalue = pow(2, -1 * (pow(2, $exponentbits - 1) - 2)) * DecimalBinary2Float($fractionstring);
if ($signbit == '1') {
$floatvalue *= -1;
}
} else {
if ($exponent != 0) {
$floatvalue = pow(2, $exponent - (pow(2, $exponentbits - 1) - 1)) * (1 + DecimalBinary2Float($fractionstring));
if ($signbit == '1') {
$floatvalue *= -1;
}
}
}
}
}
}
return (double) $floatvalue;
}
