将字节流转换为数字数据类型

Question

假设我有一个字节流,其中我知道64位值(64位随机数)的位置.字节顺序是Little-Endian.由于PHP的整数数据类型限制为32位(至少在32位操作系统上),我如何将字节序列转换为PHP数字表示(我认为浮点就足够了)？

$serverChallenge = substr($bytes, 24, 8);
// $serverChallenge now contains the byte-sequence 
// of which I know that it's a 64-bit value

Answer 1

只是查找代码Zend_Crypt_Math_BigInteger_Bcmath并Zend_Crypt_Math_BigInteger_Gmp处理此问题:

使用BCmath(Big-Endian)

这基本上是Chad Birch发布的解决方案.

public static function bc_binaryToInteger($operand)
{
    $result = '0';
    while (strlen($operand)) {
        $ord = ord(substr($operand, 0, 1));
        $result = bcadd(bcmul($result, 256), $ord);
        $operand = substr($operand, 1);
    }
    return $result;
}

使用GMP(Big-Endian)

相同的algorithem - 只是不同的函数名称.

public static function gmp_binaryToInteger($operand)
{
    $result = '0';
    while (strlen($operand)) {
        $ord = ord(substr($operand, 0, 1));
        $result = gmp_add(gmp_mul($result, 256), $ord);
        $operand = substr($operand, 1);
    }
    return gmp_strval($result);
}

更改algorithem以使用Litte-Endian字节顺序非常简单:只需从end到start读取二进制数据:

使用BCmath(Litte-Endian)

public static function bc_binaryToInteger($operand)
{
    // Just reverse the binray data
    $operand = strrev($operand);
    $result = '0';
    while (strlen($operand)) {
        $ord = ord(substr($operand, 0, 1));
        $result = bcadd(bcmul($result, 256), $ord);
        $operand = substr($operand, 1);
    }
    return $result;
}

使用GMP(Litte-Endian)

public static function gmp_binaryToInteger($operand)
{
    // Just reverse the binray data
    $operand = strrev($operand);
    $result = '0';
    while (strlen($operand)) {
        $ord = ord(substr($operand, 0, 1));
        $result = gmp_add(gmp_mul($result, 256), $ord);
        $operand = substr($operand, 1);
    }
    return gmp_strval($result);
}