[[string]]。pack（'H *'）是什么意思？ [英] What does ["string"].pack('H*') mean?

问题描述

我需要将一些Ruby代码翻译成JavaScript，并且遇到以下函数：

  def sha1_hex（h）
 Digest :: SHA1.hexdigest（[h] .pack（'H *'））
 end 
  

在这种情况下， [h] .pack（'H *'）意味着什么？它如何转换为JavaScript？解析方案

它将字符串解释为十六进制数字，每个字节两个字符，并将其转换为字符串与相应的ASCII码字符：

  [464F4F]。pack（'H *'）＃=> ; FOO，0x46代表'F'，0x4F代码为'O'
  

相反的转换，使用 unpack ：

 'FOO'.unpack 'H *'）＃=> [464f4f] 
  

非ASCII-8BIT编码有点困难：

 á.encoding＃=> ＃<编码：UTF-8是氢。 
á.unpack（'H *'）＃=> [c3a1] 
 ['c3a1']。pack（'H *'）＃=> \xC3\xA1
 ['c3a1']。pack（'H *'）。encoding＃=> ＃<编码：ASCII-8BIT> 
 ['c3a1']。pack（'H *'）。force_encoding（'UTF-8'）＃​​=> á
  

I need to translate some Ruby code to JavaScript and came across the following function:

def sha1_hex(h)
  Digest::SHA1.hexdigest([h].pack('H*'))
end

What exactly does [h].pack('H*') mean in this context? How would it translate to JavaScript?

解决方案

It interprets the string as hex numbers, two characters per byte, and converts it to a string with the characters with the corresponding ASCII code:

["464F4F"].pack('H*')  # =>  "FOO", 0x46 is the code for 'F', 0x4F the code for 'O'

For the opposite conversion, use unpack:

'FOO'.unpack('H*')     # => ["464f4f"]

It is a little bit more difficult for non-ASCII-8BIT encodings:

"á".encoding                                # => #<Encoding:UTF-8>
"á".unpack('H*')                            # => ["c3a1"]
['c3a1'].pack('H*')                         # => "\xC3\xA1"
['c3a1'].pack('H*').encoding                # => #<Encoding:ASCII-8BIT>
['c3a1'].pack('H*').force_encoding('UTF-8') # => "á"

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