将字节流转换为数字数据类型

发布于 2024-07-16 07:58:44 字数 301 浏览 7 评论 0原文

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。字节顺序为 Little-Endian。由于 PHP 的整数数据类型仅限于 32 位（至少在 32 位操作系统上），我如何将字节序列转换为 PHP 数字表示形式（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

原文

Let's say I have a byte-stream in which I know the location of a 64-bit value (a 64-bit nonce). The byte-order is Little-Endian. As PHP's integer data-type is limited to 32-bit (at least on 32-bit operating systems) how would I convert the byte-sequence into a PHP numeric representation (float would be sufficient I think)?

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

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烦人精 2024-07-23 07:58:44

只需查找处理此问题的 Zend_Crypt_Math_BigInteger_Bcmath 和 Zend_Crypt_Math_BigInteger_Gmp 的代码：

Using BCmath (Big-Endian)

这本质上是乍得·伯奇。

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）

相同的算法 - 只是函数名称不同。

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);
}

更改算法以使用 Litte-Endian 字节顺序非常简单：只需从头到尾读取二进制数据：

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);
}

Just looked up the code for Zend_Crypt_Math_BigInteger_Bcmath and Zend_Crypt_Math_BigInteger_Gmp which deals with this problem:

Using BCmath (Big-Endian)

This is essentially the solution posted by Chad Birch.

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;
}

Using GMP (Big-Endian)

Same algorithem - just different function names.

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);
}

Changing the algorithem to use Litte-Endian byte-order is quite simple: just read the binary data from end to start:

Using 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;
}

Using 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);
}

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温柔一刀 2024-07-23 07:58:44

这看起来像是一个彻底的黑客攻击，但它应该可以完成这项工作，假设你有 daemonmoi 推荐的 BC Math 函数：

$result = "0";
for ($i = strlen($serverChallenge) - 1; $i >= 0; $i--)
{
    $result = bcmul($result, 256); // shift result

    $nextByte = (string)(ord($serverChallenge[$i]));
    $result = bcadd($result, $nextByte);
}

This seems like a total hack, but it should do the job, assuming you have the BC Math functions that daemonmoi recommended:

$result = "0";
for ($i = strlen($serverChallenge) - 1; $i >= 0; $i--)
{
    $result = bcmul($result, 256); // shift result

    $nextByte = (string)(ord($serverChallenge[$i]));
    $result = bcadd($result, $nextByte);
}

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