PHP:带符号的二进制字符串 [英] PHP: Signed Binary Strings

问题描述

将二进制字符串转换为有符号整数时遇到问题

I'm having a problem with converting binary strings to signed integers

如果您调用decbin('-40')，则php将输出1111111111111111111111111111111111111111111111111111111111011000

If you call decbin('-40'), php will output 1111111111111111111111111111111111111111111111111111111111011000

但是，如果您调用bindec(decbin('-40'))，它将输出1.84467440737E + 19(或类似的东西，显然不是-40)，因为它将最高有效位视为另一个数量级而不是作为符号位"-php手册

But if you call bindec(decbin('-40')), it will output 1.84467440737E+19 (or something similar, which is obviously not -40) because it "sees the most significant bit as another order of magnitude rather than as the sign bit" - php manual

有没有一种方法可以将64位二进制二进制字符串(与decbin的输出很相似)转换为有符号整数?

Is there a way to convert a binary 64 bit binary string (much like the one output by decbin) string into a signed integer?

推荐答案

从文档中不能使用 bindec

bindec()将所有binary_string值解释为无符号整数.这是因为bindec()将最高有效位视为另一个数量级，而不是符号位.

bindec() interprets all binary_string values as unsigned integers. This is because bindec() sees the most significant bit as another order of magnitude rather than as the sign bit.

base_convert 似乎完全忽略了签名.

base_convert appears to ignore signing altogether.

如果您知道传入的字符串将始终为64位二进制文​​件，而您不是在32位系统上，则编写自定义函数非常容易.

If you know that your incoming string will always be 64 bit binary and you are not on a 32 bit system, it's quite easy to write a custom function.

• 检查字符串是否为64个字符长.
• 检查最高有效位是否为1.
• 翻转所有位
• 添加1
• 取反

这是我一起敲门的快捷方式.

Here's a quick one I knocked together.

function bindec2($bin)
{
    if (strlen($bin) == 64 && $bin[0] == '1') {
        for ($i = 0; $i < 64; $i++) {
            $bin[$i] = $bin[$i] == '1' ? '0' : '1';
        }

        return (bindec($bin) + 1) * -1;
    }
    return bindec($bin);
}

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