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1"""
2Page labels are shown by PDF viewers as "the page number".
4A page has a numeric index, starting at 0. Additionally, the page
5has a label. In the most simple case:
7 label = index + 1
9However, the title page and the table of contents might have Roman numerals as
10page labels. This makes things more complicated.
12Example 1
13---------
15>>> reader.root_object["/PageLabels"]["/Nums"]
16[0, IndirectObject(18, 0, 139929798197504),
17 8, IndirectObject(19, 0, 139929798197504)]
18>>> reader.get_object(reader.root_object["/PageLabels"]["/Nums"][1])
19{'/S': '/r'}
20>>> reader.get_object(reader.root_object["/PageLabels"]["/Nums"][3])
21{'/S': '/D'}
23Example 2
24---------
25The following is a document with pages labeled
26i, ii, iii, iv, 1, 2, 3, A-8, A-9, ...
281 0 obj
29 << /Type /Catalog
30 /PageLabels << /Nums [
31 0 << /S /r >>
32 4 << /S /D >>
33 7 << /S /D
34 /P ( A- )
35 /St 8
36 >>
37 % A number tree containing
38 % three page label dictionaries
39 ]
40 >>
41 ...
42 >>
43endobj
46§12.4.2 PDF Specification 1.7 and 2.0
47=====================================
49Entries in a page label dictionary
50----------------------------------
51The /S key:
52D Decimal Arabic numerals
53R Uppercase Roman numerals
54r Lowercase Roman numerals
55A Uppercase letters (A to Z for the first 26 pages,
56 AA to ZZ for the next 26, and so on)
57a Lowercase letters (a to z for the first 26 pages,
58 aa to zz for the next 26, and so on)
59"""
61from collections.abc import Callable, Iterator
62from typing import Optional, cast
64from ._protocols import PdfCommonDocProtocol
65from ._utils import logger_warning
66from .generic import (
67 ArrayObject,
68 DictionaryObject,
69 NullObject,
70 NumberObject,
71 is_null_or_none,
72)
75def number2uppercase_roman_numeral(num: int) -> str:
76 roman = [
77 (1000, "M"),
78 (900, "CM"),
79 (500, "D"),
80 (400, "CD"),
81 (100, "C"),
82 (90, "XC"),
83 (50, "L"),
84 (40, "XL"),
85 (10, "X"),
86 (9, "IX"),
87 (5, "V"),
88 (4, "IV"),
89 (1, "I"),
90 ]
92 def roman_num(num: int) -> Iterator[str]:
93 for decimal, roman_repr in roman:
94 x, _ = divmod(num, decimal)
95 yield roman_repr * x
96 num -= decimal * x
97 if num <= 0:
98 break
100 return "".join(list(roman_num(num)))
103def number2lowercase_roman_numeral(number: int) -> str:
104 return number2uppercase_roman_numeral(number).lower()
107def number2uppercase_letter(number: int) -> str:
108 if number <= 0:
109 raise ValueError("Expecting a positive number")
110 alphabet = [chr(i) for i in range(ord("A"), ord("Z") + 1)]
111 rep = ""
112 while number > 0:
113 remainder = number % 26
114 if remainder == 0:
115 remainder = 26
116 rep = alphabet[remainder - 1] + rep
117 # update
118 number -= remainder
119 number = number // 26
120 return rep
123def number2lowercase_letter(number: int) -> str:
124 return number2uppercase_letter(number).lower()
127def get_label_from_nums(dictionary_object: DictionaryObject, index: int) -> str:
128 # [Nums] shall be an array of the form
129 # [ key_1 value_1 key_2 value_2 ... key_n value_n ]
130 # where each key_i is an integer and the corresponding
131 # value_i shall be the object associated with that key.
132 # The keys shall be sorted in numerical order,
133 # analogously to the arrangement of keys in a name tree
134 # as described in 7.9.6, "Name Trees."
135 nums = cast(ArrayObject, dictionary_object["/Nums"])
136 nums_length = len(nums)
137 i = 0
138 value = None
139 start_index = 0
140 while i < nums_length:
141 if i + 1 >= nums_length:
142 logger_warning(
143 "Ignoring last /Nums key without a value.", source=__name__
144 )
145 break
146 start_index = nums[i]
147 value = nums[i + 1].get_object()
148 if i + 2 == nums_length:
149 break
150 if nums[i + 2] > index:
151 break
152 i += 2
153 m: dict[Optional[str], Callable[[int], str]] = {
154 None: lambda _: "",
155 "/D": str,
156 "/R": number2uppercase_roman_numeral,
157 "/r": number2lowercase_roman_numeral,
158 "/A": number2uppercase_letter,
159 "/a": number2lowercase_letter,
160 }
161 # if /Nums array is not following the specification or if /Nums is empty
162 if not isinstance(value, dict):
163 return str(index + 1) # Fallback
164 start = value.get("/St", 1)
165 prefix = cast(str, value.get("/P", ""))
166 mapping_function = m.get(value.get("/S"))
167 if mapping_function is None:
168 # Unknown /S numbering style; fall back to the page position.
169 logger_warning(
170 "Ignoring unknown page label numbering style %(style)r in /Nums.",
171 source=__name__,
172 style=value.get("/S"),
173 )
174 return str(index + 1) # Fallback
175 try:
176 return prefix + mapping_function(index - start_index + start)
177 except (TypeError, ValueError):
178 # Malformed /St or /P value; fall back to the page position.
179 logger_warning(
180 "Ignoring malformed page label entry in /Nums (/St=%(start)r, /P=%(prefix)r).",
181 source=__name__,
182 start=start,
183 prefix=prefix,
184 )
185 return str(index + 1) # Fallback
188def index2label(reader: PdfCommonDocProtocol, index: int) -> str:
189 """
190 See 7.9.7 "Number Trees".
192 Args:
193 reader: The PdfReader
194 index: The index of the page
196 Returns:
197 The label of the page, e.g. "iv" or "4".
199 """
200 root = cast(DictionaryObject, reader.root_object)
201 if "/PageLabels" not in root:
202 return str(index + 1) # Fallback
203 number_tree = cast(DictionaryObject, root["/PageLabels"].get_object())
204 if "/Nums" in number_tree:
205 return get_label_from_nums(number_tree, index)
206 if "/Kids" in number_tree and not isinstance(number_tree["/Kids"], NullObject):
207 # number_tree = {'/Kids': [IndirectObject(7333, 0, 140132998195856), ...]}
208 # Limit maximum depth.
209 level = 0
210 while level < 100:
211 kids = cast(list[DictionaryObject], number_tree["/Kids"])
212 for kid in kids:
213 # kid = {'/Limits': [0, 63], '/Nums': [0, {'/P': 'C1'}, ...]}
214 limits = kid.get("/Limits", NullObject()).get_object()
215 if not isinstance(limits, list) or len(limits) < 2:
216 # Skip kids whose /Limits range is missing or malformed.
217 logger_warning(
218 "Ignoring kid with missing or malformed /Limits in /PageLabels.",
219 source=__name__,
220 )
221 continue
222 if limits[0] <= index <= limits[1]:
223 if not is_null_or_none(kid.get("/Kids", None)):
224 # Recursive definition.
225 level += 1
226 if level == 100: # pragma: no cover
227 raise NotImplementedError(
228 "Too deep nesting is not supported."
229 )
230 number_tree = kid
231 # Exit the inner `for` loop and continue at the next level with the
232 # next iteration of the `while` loop.
233 break
234 return get_label_from_nums(kid, index)
235 else:
236 # When there are no kids, make sure to exit the `while` loop directly
237 # and continue with the fallback.
238 break
240 logger_warning("Could not reliably determine page label for %(index)d.", source=__name__, index=index)
241 return str(index + 1) # Fallback if neither /Nums nor /Kids is in the number_tree
244def nums_insert(
245 key: NumberObject,
246 value: DictionaryObject,
247 nums: ArrayObject,
248) -> None:
249 """
250 Insert a key, value pair in a Nums array.
252 See 7.9.7 "Number Trees".
254 Args:
255 key: number key of the entry
256 value: value of the entry
257 nums: Nums array to modify
259 """
260 if len(nums) % 2 != 0:
261 raise ValueError("A nums like array must have an even number of elements")
263 i = len(nums)
264 while i != 0 and key <= nums[i - 2]:
265 i = i - 2
267 if i < len(nums) and key == nums[i]:
268 nums[i + 1] = value
269 else:
270 nums.insert(i, key)
271 nums.insert(i + 1, value)
274def nums_clear_range(
275 key: NumberObject,
276 page_index_to: int,
277 nums: ArrayObject,
278) -> None:
279 """
280 Remove all entries in a number tree in a range after an entry.
282 See 7.9.7 "Number Trees".
284 Args:
285 key: number key of the entry before the range
286 page_index_to: The page index of the upper limit of the range
287 nums: Nums array to modify
289 """
290 if len(nums) % 2 != 0:
291 raise ValueError("A nums like array must have an even number of elements")
292 if page_index_to < key:
293 raise ValueError("page_index_to must be greater or equal than key")
295 i = nums.index(key) + 2
296 while i < len(nums) and nums[i] <= page_index_to:
297 nums.pop(i)
298 nums.pop(i)
301def nums_next(
302 key: NumberObject,
303 nums: ArrayObject,
304) -> tuple[Optional[NumberObject], Optional[DictionaryObject]]:
305 """
306 Return the (key, value) pair of the entry after the given one.
308 See 7.9.7 "Number Trees".
310 Args:
311 key: number key of the entry
312 nums: Nums array
314 """
315 if len(nums) % 2 != 0:
316 raise ValueError("A nums like array must have an even number of elements")
318 i = nums.index(key) + 2
319 if i < len(nums):
320 return (nums[i], nums[i + 1])
321 return (None, None)