Ruby中的位移 [英] Bit shifting in Ruby

问题描述

我目前正在将Visual Basic应用程序转换为Ruby，因为我们正在将其移至Web.但是，在转换某些算法时，我遇到了有关移位的问题.

I'm currently converting a Visual Basic application to Ruby because we're moving it to the web. However when converting some algorithms I've run into a problem concerning bit shifting.

据我所知，问题在于VB对Integer类型执行的大小掩码(如

How I understand it, the problem lies in the size mask VB enforces on Integer types (as explained Here). Ruby, in practice, doesn't differentiate in these types.

那么问题是

Dim i As Integer = 182
WriteLine(i << 24) '-1241513984

Ruby

puts 182 << 24 # 3053453312

我一直在Google上搜索并阅读了过去几个小时的移位信息，但是还没有找到解决此问题的方法或方向.

I've been Googling and reading up on bit shifting the last hours but haven't found a way, or direction even, to tackle this problem.

推荐答案

您需要复制Visual Basic正在做什么，即

You need to replicate what visual basic is doing, namely

• 根据记录屏蔽移位值
• 使用0xFFFFFFFF遮盖结果(因为ruby将为您提升该值到一个大数字
• 如果最高位被设置，则从结果中减去2 ^ 32(因为带符号的整数存储在例如

  def shift_32 x, shift_amount
    shift_amount &= 0x1F
    x <<= shift_amount
    x &= 0xFFFFFFFF 
  
    if (x & (1<<31)).zero?
     x
    else
     x - 2**32
    end
  end
  

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