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  • Python3标准库：zlib GNUzlib压缩(2)

lorem
  • print('Decompressed matches lorem:',decompressed_matches)
  •  
  • unused_matches = decompressor.unused_data == lorem
  • print('Unused data matches lorem:',unused_matches)

    • 解压缩所有数据后，unused_data属性会包含未用的所有数据。

    1.4 校验和

    除了压缩和解压缩函数，zlib还包括两个用于计算数据的校验和的函数，分别是adler32()和crc32()。这两个函数计算出的校验和都不能认为是密码安全的，它们只用于数据完整性验证。

    
	
      
		
    1. 
			import zlib
      2. 
		
    2. 
			 
      3. 
		
    3. 
			data = open('lorem.txt','rb').read()
      4. 
		
    4. 
			 
      5. 
		
    5. 
			cksum = zlib.adler32(data)
      6. 
		
    6. 
			print('Adler32: {:12d}'.format(cksum))
      7. 
		
    7. 
			print(' : {:12d}'.format(zlib.adler32(data,cksum)))
      8. 
		
    8. 
			 
      9. 
		
    9. 
			cksum = zlib.crc32(data)
      10. 
		
    10. 
			print('CRC-32: {:12d}'.format(cksum))
      11. 
		
    11. 
			print(' : {:12d}'.format(zlib.crc32(data,cksum)))
      12. 
	
    

    

    
	这两个函数取相同的参数，包括一个包含数据的字节串和一个可选值，这个值可作为校验和的起点。这些函数会返回一个32位有符号整数值，这个值可以作为一个新的起点参数再传回给后续的调用，以生成一个动态变化的校验和。
    

    
	
    

    
	
    

    
	1.5 压缩网络数据
    

    
	下一个代码清单中的服务器使用流压缩器来响应文件名请求，它将文件的一个压缩版本写至与客户通信的套接字中。
    

    
	
    
	
      
		
    1. 
			import zlib
      2. 
		
    2. 
			import logging
      3. 
		
    3. 
			import socketserver
      4. 
		
    4. 
			import binascii
      5. 
		
    5. 
			 
      6. 
		
    6. 
			BLOCK_SIZE = 64
      7. 
		
    7. 
			 
      8. 
		
    8. 
			 
      9. 
		
    9. 
			class ZlibRequestHandler(socketserver.BaseRequestHandler):
      10. 
		
    10. 
			 
      11. 
		
    11. 
			logger = logging.getLogger('Server')
      12. 
		
    12. 
			 
      13. 
		
    13. 
			def handle(self):
      14. 
		
    14. 
			compressor = zlib.compressobj(1)
      15. 
		
    15. 
			 
      16. 
		
    16. 
			# Find out what file the client wants
      17. 
		
    17. 
			filename = self.request.recv(1024).decode('utf-8')
      18. 
		
    18. 
			self.logger.debug('client asked for: %r', filename)
      19. 
		
    19. 
			 
      20. 
		
    20. 
			# Send chunks of the file as they are compressed
      21. 
		
    21. 
			with open(filename, 'rb') as input:
      22. 
		
    22. 
			while True:
      23. 
		
    23. 
			block = input.read(BLOCK_SIZE)
      24. 
		
    24. 
			if not block:
      25. 
		
    25. 
			break
      26. 
		
    26. 
			self.logger.debug('RAW %r', block)
      27. 
		
    27. 
			compressed = compressor.compress(block)
      28. 
		
    28. 
			if compressed:
      29. 
		
    29. 
			self.logger.debug(
      30. 
		
    30. 
			'SENDING %r',
      31. 
		
    31. 
			binascii.hexlify(compressed))
      32. 
		
    32. 
			self.request.send(compressed)
      33. 
		
    33. 
			else:
      34. 
		
    34. 
			self.logger.debug('BUFFERING')
      35. 
		
    35. 
			 
      36. 
		
    36. 
			# Send any data being buffered by the compressor
      37. 
		
    37. 
			remaining = compressor.flush()
      38. 
		
    38. 
			while remaining:
      39. 
		
    39. 
			to_send = remaining[:BLOCK_SIZE]
      40. 
		
    40. 
			remaining = remaining[BLOCK_SIZE:]
      41. 
		
    41. 
			self.logger.debug('FLUSHING %r',
      42. 
		
    42. 
			binascii.hexlify(to_send))
      43. 
		
    43. 
			self.request.send(to_send)
      44. 
		
    44. 
			return
      45. 
		
    45. 
			 
      46. 
		
    46. 
			 
      47. 
		
    47. 
			if __name__ == '__main__':
      48. 
		
    48. 
			import socket
      49. 
		
    49. 
			import threading
      50. 
		
    50. 
			from io import BytesIO
      51. 
		
    51. 
			 
      52. 
		
    52. 
			logging.basicConfig(
      53. 
		
    53. 
			level=logging.DEBUG,
      54. 
		
    54. 
			format='%(name)s: %(message)s',
      55. 
		
    55. 
			)
      56. 
		
    56. 
			logger = logging.getLogger('Client')
      57. 
		
    57. 
			 
      58. 
		
    58. 
			# Set up a server, running in a separate thread
      59. 
		
    59. 
			address = ('localhost', 0) # let the kernel assign a port
      60. 
		
    60. 
			server = socketserver.TCPServer(address, ZlibRequestHandler)
      61. 
		
    61. 
			ip, port = server.server_address # what port was assigned?
      62. 
		
    62. 
			 
      63. 
		
    63. 
			t = threading.Thread(target=server.serve_forever)
      64. 
		
    64. 
			t.setDaemon(True)
      65. 
		
    65. 
			t.start()
      



  
    
  
  
    
   
  
    
  
 
 
    
 
 
  
 
 
 
 

    




 



    


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