📄 10 - performing random access on read-once input streams.rb
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require 'socket'require 'stringio'sock = TCPSocket.open("www.example.com", 80)sock.write("GET /\n")file = StringIO.new(sock.read)file.read(10) # => "<HTML>\r\n<H"file.rewindfile.read(10) # => "<HTML>\r\n<H"file.pos = 90file.read(15) # => " this web page "#---class BufferedIO def initialize(io) @buff = StringIO.new @source = io @pos = 0 end def read(x=nil) to_read = x ? to_read = x+@buff.pos-@buff.size : nil _append(@source.read(to_read)) if !to_read or to_read > 0 @buff.read(x) end def pos=(x) read(x-@buff.pos) if x > @buff.size @buff.pos = x end def seek(x, whence=IO::SEEK_SET) case whence when IO::SEEK_SET then self.pos=(x) when IO::SEEK_CUR then self.pos=(@buff.pos+x) when IO::SEEK_END then read; self.pos=(@buff.size-x) # Note: this reads all the socket data. end pos end # Some methods can simply be delegated to the buffer. ["pos", "rewind", "tell"].each do |m| module_eval "def #{m}\n@buff.#{m}\nend" end private def _append(s) @buff << s @buff.pos -= s.size endend#---sock = TCPSocket.open("www.example.com", 80)sock.write("GET /\n")file = BufferedIO.new(sock)file.read(10) # => "<HTML>\r\n<H"file.rewind # => 0file.read(10) # => "<HTML>\r\n<H"file.pos = 90 # => 90file.read(15) # => " this web page "file.seek(-10, IO::SEEK_CUR) # => 95file.read(10) # => " web page "#---class BufferedIO def readline oldpos = @buff.pos line = @buff.readline unless @buff.eof? if !line or line[-1] != ?\n _append(@source.readline) # Finish the line @buff.pos = oldpos # Go back to where we were line = @buff.readline # Read the line again end line endendfile.readline# => "by typing "example.com",\r\n"#---⌨️ 快捷键说明
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