python - python zlib 库是否支持 uuencode？

Question

我的 python 代码正在尝试使用 zlib 库解压缩一个 uuencoded 文件。这是代码片段:

self.decompress = zlib.decompressobj(wbits)
.
.
buf = self.fileobj.read(size)
.
.
uncompress = self.decompress.decompress(buf)

我当前的 wbits 值是“-zlib.MAX_WBITS”。这会引发错误:

Error -3 while decompressing: invalid literal/lengths set

我意识到 python zlib 库支持:

RFC 1950 (zlib compressed format)
RFC 1951 (deflate compressed format)
RFC 1952 (gzip compressed format)

wbits 的选择是:

to (de-)compress deflate format, use wbits = -zlib.MAX_WBITS
to (de-)compress zlib format, use wbits = zlib.MAX_WBITS
to (de-)compress gzip format, use wbits = zlib.MAX_WBITS | 16

所以我的问题是:

Where does a uuencoded file fall in this list?
Is it supported by zlib?
If yes, what should be the value for wbits?
If no, how do I proceed with this?

提前致谢!

Answer 1

这里有一个快速演示，说明如何使用 zlib 进行压缩并使用 uuencode 进行编码，然后反转该过程。

#!/usr/bin/env python

import zlib

data = '''This is a short piece of test data
intended to test uuencoding and decoding
using the uu module, and compression and 
decompression using zlib.
'''

data = data * 5

# encode
enc = zlib.compress(data, 9).encode('uu')
print enc

# decode
dec = zlib.decompress(enc.decode('uu'))

#print `dec` 
print dec == data

输出

begin 666 <data>
M>-KMCLL-A# ,1.^I8@I 5$,#(?822V C[%RV>CXY; %[19K+/,U(;ZKBN)+A
MU8[ +EP8]D&P!RA'3J+!2DP(Z[0UUF(DNB K@;B7U/Q&4?E:8#-J*P_/HMBV
;'^PNID]/]^6'^N^[RCRFZ?5Y??[P.0$_I03L

end

True

---

以上代码仅适用于Python 2。Python 3 明确区分了文本和字节，不支持字节字符串的编码，也不支持文本字符串的解码。所以它不能使用上面显示的简单 uuencoding/uudecoding 技术。

这是一个适用于 Python2 和 Python 3 的新版本。

from __future__ import print_function
import zlib
import uu
from io import BytesIO

def zlib_uuencode(databytes, name='<data>'):
    ''' Compress databytes with zlib & uuencode the result '''
    inbuff = BytesIO(zlib.compress(databytes, 9))
    outbuff = BytesIO()
    uu.encode(inbuff, outbuff, name=name)
    return outbuff.getvalue()

def zlib_uudecode(databytes):
    ''' uudecode databytes and decompress the result with zlib '''
    inbuff = BytesIO(databytes)
    outbuff = BytesIO()
    uu.decode(inbuff, outbuff)
    return zlib.decompress(outbuff.getvalue())

# Test

# Some plain text data
data = '''This is a short piece of test data
intended to test uuencoding and decoding
using the uu module, and compression and 
decompression using zlib.
'''

# Replicate the data so the compressor has something to compress
data = data * 5
#print(data)
print('Original length:', len(data))

# Convert the text to bytes & compress it.
databytes = data.encode()
enc = zlib_uuencode(databytes)
enc_text = enc.decode()
print(enc_text)
print('Encoded length:', len(enc_text))

# Decompress & verify that it's correct
dec = zlib_uudecode(enc)
print(dec == databytes)   

输出

Original length: 720
begin 666 <data>
M>-KMCLL-A# ,1.^I8@I 5$,#(?822V C[%RV>CXY; %[19K+/,U(;ZKBN)+A
MU8[ +EP8]D&P!RA'3J+!2DP(Z[0UUF(DNB K@;B7U/Q&4?E:8#-J*P_/HMBV
;'^PNID]/]^6'^N^[RCRFZ?5Y??[P.0$_I03L

end

Encoded length: 185
True

请注意 zlib_uuencode 和 zlib_uuencode 作用于 bytes 字符串:您必须向它们传递一个 bytes arg，并返回一个 bytes 结果。