calibre-web/vendor/PyPDF2/pagerange.py

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2016-08-07 20:12:32 +00:00
#!/usr/bin/env python
"""
Representation and utils for ranges of PDF file pages.
Copyright (c) 2014, Steve Witham <switham_github@mac-guyver.com>.
All rights reserved. This software is available under a BSD license;
see https://github.com/mstamy2/PyPDF2/blob/master/LICENSE
"""
import re
from .utils import isString
_INT_RE = r"(0|-?[1-9]\d*)" # A decimal int, don't allow "-0".
PAGE_RANGE_RE = "^({int}|({int}?(:{int}?(:{int}?)?)))$".format(int=_INT_RE)
# groups: 12 34 5 6 7 8
class ParseError(Exception):
pass
PAGE_RANGE_HELP = """Remember, page indices start with zero.
Page range expression examples:
: all pages. -1 last page.
22 just the 23rd page. :-1 all but the last page.
0:3 the first three pages. -2 second-to-last page.
:3 the first three pages. -2: last two pages.
5: from the sixth page onward. -3:-1 third & second to last.
The third, "stride" or "step" number is also recognized.
::2 0 2 4 ... to the end. 3:0:-1 3 2 1 but not 0.
1:10:2 1 3 5 7 9 2::-1 2 1 0.
::-1 all pages in reverse order.
"""
class PageRange(object):
"""
A slice-like representation of a range of page indices,
i.e. page numbers, only starting at zero.
The syntax is like what you would put between brackets [ ].
The slice is one of the few Python types that can't be subclassed,
but this class converts to and from slices, and allows similar use.
o PageRange(str) parses a string representing a page range.
o PageRange(slice) directly "imports" a slice.
o to_slice() gives the equivalent slice.
o str() and repr() allow printing.
o indices(n) is like slice.indices(n).
"""
def __init__(self, arg):
"""
Initialize with either a slice -- giving the equivalent page range,
or a PageRange object -- making a copy,
or a string like
"int", "[int]:[int]" or "[int]:[int]:[int]",
where the brackets indicate optional ints.
{page_range_help}
Note the difference between this notation and arguments to slice():
slice(3) means the first three pages;
PageRange("3") means the range of only the fourth page.
However PageRange(slice(3)) means the first three pages.
"""
if isinstance(arg, slice):
self._slice = arg
return
if isinstance(arg, PageRange):
self._slice = arg.to_slice()
return
m = isString(arg) and re.match(PAGE_RANGE_RE, arg)
if not m:
raise ParseError(arg)
elif m.group(2):
# Special case: just an int means a range of one page.
start = int(m.group(2))
stop = start + 1 if start != -1 else None
self._slice = slice(start, stop)
else:
self._slice = slice(*[int(g) if g else None
for g in m.group(4, 6, 8)])
# Just formatting this when there is __doc__ for __init__
if __init__.__doc__:
__init__.__doc__ = __init__.__doc__.format(page_range_help=PAGE_RANGE_HELP)
@staticmethod
def valid(input):
""" True if input is a valid initializer for a PageRange. """
return isinstance(input, slice) or \
isinstance(input, PageRange) or \
(isString(input)
and bool(re.match(PAGE_RANGE_RE, input)))
def to_slice(self):
""" Return the slice equivalent of this page range. """
return self._slice
def __str__(self):
""" A string like "1:2:3". """
s = self._slice
if s.step == None:
if s.start != None and s.stop == s.start + 1:
return str(s.start)
indices = s.start, s.stop
else:
indices = s.start, s.stop, s.step
return ':'.join("" if i == None else str(i) for i in indices)
def __repr__(self):
""" A string like "PageRange('1:2:3')". """
return "PageRange(" + repr(str(self)) + ")"
def indices(self, n):
"""
n is the length of the list of pages to choose from.
Returns arguments for range(). See help(slice.indices).
"""
return self._slice.indices(n)
PAGE_RANGE_ALL = PageRange(":") # The range of all pages.
def parse_filename_page_ranges(args):
"""
Given a list of filenames and page ranges, return a list of
(filename, page_range) pairs.
First arg must be a filename; other ags are filenames, page-range
expressions, slice objects, or PageRange objects.
A filename not followed by a page range indicates all pages of the file.
"""
pairs = []
pdf_filename = None
did_page_range = False
for arg in args + [None]:
if PageRange.valid(arg):
if not pdf_filename:
raise ValueError("The first argument must be a filename, " \
"not a page range.")
pairs.append( (pdf_filename, PageRange(arg)) )
did_page_range = True
else:
# New filename or end of list--do all of the previous file?
if pdf_filename and not did_page_range:
pairs.append( (pdf_filename, PAGE_RANGE_ALL) )
pdf_filename = arg
did_page_range = False
return pairs