Source code for gluon.decoder

#!/usr/bin/env python
# -*- coding: utf-8 -*-

Caller will hand this library a buffer and ask it to either convert
it or auto-detect the type.

Based on

Licensed under the PSF License

import codecs

# 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")

[docs]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. if len(buffer) >= 4: 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) else: enc_info = None 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
[docs]def decoder(buffer): encoding = autoDetectXMLEncoding(buffer) return buffer.decode(encoding).encode('utf8')