Gzip the data by streaming

What you want to do

• Gzip the data multiple times (part by part)
• You can get compressed partial data

I wanted to dynamically create and return Gzip data in Flask Streaming Contents.

code

GzipStream class (self-made).

#!/usr/bin/env python
# encoding: utf-8

from gzip import GzipFile
from StringIO import StringIO


class GzipStream(object):
    
    def __init__(self):
        self._io = StringIO()
        self._gf = GzipFile(fileobj=self._io, mode='wb')
        self._pos = 0
    
    def push(self, content):
        '''
        push a part of content.
        '''
        assert not self._gf.closed
        self._gf.write(content)
        self._gf.flush()
    
    def pop(self):
        '''
        :return: A part of gzipped content, or "None" that means EOF.
        '''
        current_pos = self._io.len
        
        if self._gf.closed and current_pos == self._pos:
            return None
        
        part = self._io.getvalue()[self._pos:current_pos]
        self._pos = current_pos
        
        return part
    
    def close(self):
        '''
        you must call this.
        '''
        if not self._gf.closed:
            self._gf.close()
    
    def __enter__(self):
        '''You don't have to'''
        return self
    
    def __exit__(self, exc_type, exc_value, traceback):
        '''You don't have to'''
        self.close()

Try using it as follows.

>>> from streamgzip import GzipStream

>>> gs = GzipStream()

>>> gs.push('hello ')
>>> gs.pop()
'\x1f\x8b\x08\x00\xfd\xcf\x0cX\x02\xff\xcaH\xcd\xc9\xc9W\x00\x00\x00\x00\xff\xff'

>>> gs.push('world ')
>>> gs.push('!!')
>>> gs.pop()
'*\xcf/\xcaIQ\x00\x00\x00\x00\xff\xffRT\x04\x00\x00\x00\xff\xff'

>>> gs.close()
>>> gs.pop()
'\x03\x00\xb7\xc8\xd4%\x0e\x00\x00\x00'

>>> print gs.pop()
None

Try to verify that the data is correct.

>>> from gzip import GzipFile
>>> from StringIO import StringIO

>>> io = StringIO()
>>> io.write('\x1f\x8b\x08\x00\xfd\xcf\x0cX\x02\xff\xcaH\xcd\xc9\xc9W\x00\x00\x00\x00\xff\xff*\xcf/\xcaIQ\x00\x00\x00\x00\xff\xffRT\x04\x00\x00\x00\xff\xff\x03\x00\xb7\xc8\xd4%\x0e\x00\x00\x00')
>>> io.seek(0)
>>> gzfile = GzipFile(fileobj=io, mode='rb')
>>> gzfile.read()
'hello world !!'