¶ autoDetectXMLEncoding.py

2006-04-04 23:23

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"""http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/52257
#tags utility,py4zh
Title: Auto-detect XML encoding
Submitter: Paul Prescod (other recipes)
Last Updated: 2001/03/14
Version no: 1.0
Category: XML
推荐:: 发件人: 清风 <[email protected]> 
回复: [email protected]
收件人: [email protected]
日期: 2006-1-18 上午1:27
主题: Re: [python-chinese] 如何取得一个文本的编码格式？
"""
import codecs, encodings
 
"""Caller will hand this library a buffer and ask it to either convert
it or auto-detect the type."""
 
# None represents a potentially variable byte. "##" in the XML spec...
autodetect_dict={ # bytepattern     : ("name",             
                (0x00, 0x00, 0xFE, 0xFF) : ("ucs4_be"),       
                (0xFF, 0xFE, 0x00, 0x00) : ("ucs4_le"),
                (0xFE, 0xFF, None, None) : ("utf_16_be"),
                (0xFF, 0xFE, None, None) : ("utf_16_le"),
                (0x00, 0x3C, 0x00, 0x3F) : ("utf_16_be"),
                (0x3C, 0x00, 0x3F, 0x00) : ("utf_16_le"),
                (0x3C, 0x3F, 0x78, 0x6D): ("utf_8"),
                (0x4C, 0x6F, 0xA7, 0x94): ("EBCDIC")
                 }
 
def autoDetectXMLEncoding(buffer):
    """ buffer -> encoding_name
    The buffer should be at least 4 bytes long.
        Returns None if encoding cannot be detected.
        Note that encoding_name might not have an installed
        decoder (e.g. EBCDIC)
    """
    # a more efficient implementation would not decode the whole
    # buffer at once but otherwise we'd have to decode a character at
    # a time looking for the quote character...that's a pain
 
    encoding = "utf_8" # according to the XML spec, this is the default
                          # this code successively tries to refine the default
                          # whenever it fails to refine, it falls back to
                          # the last place encoding was set.
    bytes = (byte1, byte2, byte3, byte4) = tuple(map(ord, buffer[0:4]))
    enc_info = autodetect_dict.get(bytes, None)
 
    if not enc_info: # try autodetection again removing potentially
                     # variable bytes
        bytes = (byte1, byte2, None, None)
        enc_info = autodetect_dict.get(bytes)
 
         
    if enc_info:
        encoding = enc_info # we've got a guess... these are
                            #the new defaults
 
        # try to find a more precise encoding using xml declaration
        secret_decoder_ring = codecs.lookup(encoding)[1]
        (decoded,length) = secret_decoder_ring(buffer)
        first_line = decoded.split("\n")[0]
        if first_line and first_line.startswith(u"<!--?xml"):
            encoding_pos = first_line.find(u"encoding")
            if encoding_pos!=-1:
                # look for double quote
                quote_pos=first_line.find('"', encoding_pos)
 
                if quote_pos==-1:                 # look for single quote
                    quote_pos=first_line.find("'", encoding_pos)
 
                if quote_pos-->-1:
                    quote_char,rest=(first_line[quote_pos],
                                                first_line[quote_pos+1:])
                    encoding=rest[:rest.find(quote_char)]
 
    return encoding
 
</[email protected]>

§ 写于: Tue, 04 Apr 2006 | 永久链接;源文: rdf ,rss ,raw | 分类: /utility/py4zh §
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