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# Copyright 1999 by Jeffrey Chang. All rights reserved.
# This code is part of the Biopython distribution and governed by its
# license. Please see the LICENSE file that should have been included
# as part of this package.
"""Code for more fancy file handles.
Classes:
UndoHandle File object decorator with support for undo-like operations.
StringHandle Wraps a file object around a string.
SGMLHandle File object that automatically strips SGML tags from data.
SGMLStripper Object that strips SGML.
"""
import os
import string
import StringIO
import sgmllib
class UndoHandle:
"""A Python handle that adds functionality for saving lines.
Saves lines in a LIFO fashion.
Added methods:
saveline Save a line to be returned next time.
peekline Peek at the next line without consuming it.
"""
def __init__(self, handle):
self._handle = handle
self._saved = []
def readlines(self, *args, **keywds):
lines = self._saved + self._handle.readlines(*args,**keywds)
self._saved = []
return lines
def readline(self, *args, **keywds):
if self._saved:
line = self._saved.pop(0)
else:
line = self._handle.readline(*args,**keywds)
return line
def read(self, size=-1):
if size == -1:
saved = string.join(self._saved, "")
self._saved[:] = []
else:
saved = ''
while size > 0 and self._saved:
if len(self._saved[0]) <= size:
size = size - len(self._saved[0])
saved = saved + self._saved.pop(0)
else:
saved = saved + self._saved[0][:size]
self._saved[0] = self._saved[0][size:]
size = 0
return saved + self._handle.read(size)
def saveline(self, line):
if line:
self._saved = [line] + self._saved
def peekline(self):
if self._saved:
line = self._saved[0]
else:
line = self._handle.readline()
self.saveline(line)
return line
def tell(self):
lengths = map(len, self._saved)
sum = reduce(lambda x, y: x+y, lengths, 0)
return self._handle.tell() - sum
def seek(self, *args):
self._saved = []
self._handle.seek(*args)
def __getattr__(self, attr):
return getattr(self._handle, attr)
# I could make this faster by using cStringIO.
# However, cStringIO (in v1.52) does not implement the
# readlines method.
StringHandle = StringIO.StringIO
class SGMLHandle:
"""A Python handle that automatically strips SGML tags from data.
"""
def __init__(self, handle):
"""SGMLStripper(handle)
handle is a file handle to SGML-formatted data.
"""
self._handle = handle
self._stripper = SGMLStripper()
def read(self, *args, **keywds):
data = self._handle.read(*args, **keywds)
return self._stripper.strip(data)
def readline(self, *args, **keywds):
line = self._handle.readline(*args, **keywds)
return self._stripper.strip(line)
def readlines(self, *args, **keywds):
lines = self._handle.readlines(*args, **keywds)
for i in range(len(lines)):
lines[i] = self._stripper.strip(str)
return lines
def __getattr__(self, attr):
return getattr(self._handle, attr)
class SGMLStripper:
class MyParser(sgmllib.SGMLParser):
def __init__(self):
sgmllib.SGMLParser.__init__(self)
self.data = ''
def handle_data(self, data):
self.data = self.data + data
def __init__(self):
self._parser = SGMLStripper.MyParser()
def strip(self, str):
"""S.strip(str) -> string
Strip the SGML tags from str.
"""
if not str: # empty string, don't do anything.
return ''
# I need to make sure that I don't return an empty string if
# the buffer is not empty. This can happen if there's a newline
# character embedded within a tag. Thus, I'll first check to
# see if the last character is a newline. If it is, and it's stripped
# away, I'll add it back.
is_newline = str[-1] in ['\n', '\r']
self._parser.data = '' # clear the parser's data (don't reset)
self._parser.feed(str)
if self._parser.data:
str = self._parser.data
elif is_newline:
str = '\n'
else:
str = ''
return str
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