Ruby on Rails：解压 (Zlib::Deflate) 在一定时间后不起作用

Question

我需要在将大块文本保存到数据库之前对其进行压缩，并在客户端请求时将其解压回来。

当我使用 Rails 控制台插入新记录并立即查询新插入的记录时，我现在使用的方法似乎工作正常。即，我可以成功解压压缩的描述。

但我无法解压缩在此日期之前添加的任何其他记录的压缩描述。这对我来说真的很困惑，尤其是作为 ROR 世界的初学者。

我使用 MySQL 作为数据库。

请参阅下面的模型以更好地理解它。

require "base64"

class Video < ActiveRecord::Base
  before_save :compress_description

  def desc
    unless description.blank?
      return decompress(description)
    end
  end

  private

  def compress_description
    unless description.blank?
      self.description = compress(description)
    end
  end

  def compress(text)
    Base64.encode64(Zlib::Deflate.new(nil, -Zlib::MAX_WBITS).deflate(text, Zlib::FINISH))
  end

  def decompress(text)
    Zlib::Inflate.new(-Zlib::MAX_WBITS).inflate(Base64.decode64(text))
  end
end

Answer 1

好的，实际上很容易重现您的问题。在rails控制台中执行以下

Video.create(:description => "This is a test")
Video.last.description
=> "C8nILFYAokSFktTiEgA=\n" 
Video.last.desc
=> "This is a test" 
Video.last.save #This update corrupts the description
Video.last.desc
=> "C8nILFYAokSFktTiEgA=\n"

操作发生损坏的原因是因为您正在压缩已经压缩的字符串

您可能应该按如下方式修改您的类并且应该没问题

require 'base64'
class Video < ActiveRecord::Base
  before_save :compress_description
  after_find :decompress_description
  attr_accessor :uncompressed_description

  private

  def compress_description
    unless @uncompressed_description.blank?
    self.description = compress(@uncompressed_description)
    end
  end

  def decompress_description
    unless description.blank?
      @uncompressed_description = decompress(description)
    end
  end

  def compress(text)
    Base64.encode64(Zlib::Deflate.new(nil, -Zlib::MAX_WBITS).deflate(text, Zlib::FINISH))
  end

  def decompress(text)
    Zlib::Inflate.new(-Zlib::MAX_WBITS).inflate(Base64.decode64(text))
  end
end

现在按如下方式使用您的类

Video.create(:uncompressed_description => "This is a test")
Video.last.description
=> "C8nILFYAokSFktTiEgA=\n" 
Video.last.uncompressed_description
=> "This is a test" 
Video.last.save
Video.last.uncompressed_description
=> "This is a test"