663 lines
19 KiB
Python
663 lines
19 KiB
Python
#!/usr/bin/env python3
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# -*- coding: utf-8 -*-
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import re
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import logging
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from typing import (Any, BinaryIO, Dict, Generic, Iterator, List,
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Optional, Tuple, Type, TypeVar, Union)
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from . import settings
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from .utils import choplist
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log = logging.getLogger(__name__)
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class PSException(Exception):
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pass
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class PSEOF(PSException):
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pass
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class PSSyntaxError(PSException):
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pass
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class PSTypeError(PSException):
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pass
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class PSValueError(PSException):
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pass
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class PSObject:
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"""Base class for all PS or PDF-related data types."""
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pass
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class PSLiteral(PSObject):
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"""A class that represents a PostScript literal.
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Postscript literals are used as identifiers, such as
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variable names, property names and dictionary keys.
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Literals are case sensitive and denoted by a preceding
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slash sign (e.g. "/Name")
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Note: Do not create an instance of PSLiteral directly.
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Always use PSLiteralTable.intern().
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"""
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NameType = Union[str, bytes]
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def __init__(self, name: NameType) -> None:
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self.name = name
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def __repr__(self) -> str:
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name = self.name
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return '/%r' % name
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class PSKeyword(PSObject):
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"""A class that represents a PostScript keyword.
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PostScript keywords are a dozen of predefined words.
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Commands and directives in PostScript are expressed by keywords.
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They are also used to denote the content boundaries.
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Note: Do not create an instance of PSKeyword directly.
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Always use PSKeywordTable.intern().
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"""
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def __init__(self, name: bytes) -> None:
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self.name = name
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return
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def __repr__(self) -> str:
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name = self.name
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return '/%r' % name
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_SymbolT = TypeVar('_SymbolT', PSLiteral, PSKeyword)
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class PSSymbolTable(Generic[_SymbolT]):
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"""A utility class for storing PSLiteral/PSKeyword objects.
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Interned objects can be checked its identity with "is" operator.
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"""
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def __init__(self, klass: Type[_SymbolT]) -> None:
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self.dict: Dict[PSLiteral.NameType, _SymbolT] = {}
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self.klass: Type[_SymbolT] = klass
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return
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def intern(self, name: PSLiteral.NameType) -> _SymbolT:
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if name in self.dict:
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lit = self.dict[name]
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else:
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# Type confusion issue: PSKeyword always takes bytes as name
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# PSLiteral uses either str or bytes
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lit = self.klass(name) # type: ignore[arg-type]
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self.dict[name] = lit
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return lit
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PSLiteralTable = PSSymbolTable(PSLiteral)
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PSKeywordTable = PSSymbolTable(PSKeyword)
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LIT = PSLiteralTable.intern
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KWD = PSKeywordTable.intern
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KEYWORD_PROC_BEGIN = KWD(b'{')
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KEYWORD_PROC_END = KWD(b'}')
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KEYWORD_ARRAY_BEGIN = KWD(b'[')
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KEYWORD_ARRAY_END = KWD(b']')
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KEYWORD_DICT_BEGIN = KWD(b'<<')
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KEYWORD_DICT_END = KWD(b'>>')
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def literal_name(x: object) -> Any:
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if not isinstance(x, PSLiteral):
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if settings.STRICT:
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raise PSTypeError('Literal required: {!r}'.format(x))
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else:
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name = x
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else:
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name = x.name
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if not isinstance(name, str):
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try:
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name = str(name, 'utf-8')
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except Exception:
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pass
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return name
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def keyword_name(x: object) -> Any:
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if not isinstance(x, PSKeyword):
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if settings.STRICT:
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raise PSTypeError('Keyword required: %r' % x)
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else:
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name = x
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else:
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name = str(x.name, 'utf-8', 'ignore')
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return name
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EOL = re.compile(br'[\r\n]')
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SPC = re.compile(br'\s')
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NONSPC = re.compile(br'\S')
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HEX = re.compile(br'[0-9a-fA-F]')
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END_LITERAL = re.compile(br'[#/%\[\]()<>{}\s]')
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END_HEX_STRING = re.compile(br'[^\s0-9a-fA-F]')
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HEX_PAIR = re.compile(br'[0-9a-fA-F]{2}|.')
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END_NUMBER = re.compile(br'[^0-9]')
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END_KEYWORD = re.compile(br'[#/%\[\]()<>{}\s]')
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END_STRING = re.compile(br'[()\134]')
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OCT_STRING = re.compile(br'[0-7]')
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ESC_STRING = {
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b'b': 8,
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b't': 9,
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b'n': 10,
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b'f': 12,
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b'r': 13,
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b'(': 40,
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b')': 41,
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b'\\': 92
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}
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PSBaseParserToken = Union[float, bool, PSLiteral, PSKeyword, bytes]
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class PSBaseParser:
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"""Most basic PostScript parser that performs only tokenization.
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"""
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BUFSIZ = 4096
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def __init__(self, fp: BinaryIO) -> None:
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self.fp = fp
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self.seek(0)
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return
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def __repr__(self) -> str:
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return '<%s: %r, bufpos=%d>' % (self.__class__.__name__, self.fp,
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self.bufpos)
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def flush(self) -> None:
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return
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def close(self) -> None:
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self.flush()
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return
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def tell(self) -> int:
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return self.bufpos+self.charpos
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def poll(self, pos: Optional[int] = None, n: int = 80) -> None:
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pos0 = self.fp.tell()
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if not pos:
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pos = self.bufpos+self.charpos
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self.fp.seek(pos)
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log.info('poll(%d): %r', pos, self.fp.read(n))
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self.fp.seek(pos0)
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return
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def seek(self, pos: int) -> None:
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"""Seeks the parser to the given position.
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"""
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log.debug('seek: %r', pos)
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self.fp.seek(pos)
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# reset the status for nextline()
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self.bufpos = pos
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self.buf = b''
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self.charpos = 0
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# reset the status for nexttoken()
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self._parse1 = self._parse_main
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self._curtoken = b''
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self._curtokenpos = 0
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self._tokens: List[Tuple[int, PSBaseParserToken]] = []
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return
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def fillbuf(self) -> None:
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if self.charpos < len(self.buf):
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return
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# fetch next chunk.
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self.bufpos = self.fp.tell()
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self.buf = self.fp.read(self.BUFSIZ)
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if not self.buf:
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raise PSEOF('Unexpected EOF')
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self.charpos = 0
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return
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def nextline(self) -> Tuple[int, bytes]:
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"""Fetches a next line that ends either with \\r or \\n.
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"""
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linebuf = b''
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linepos = self.bufpos + self.charpos
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eol = False
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while 1:
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self.fillbuf()
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if eol:
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c = self.buf[self.charpos:self.charpos+1]
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# handle b'\r\n'
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if c == b'\n':
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linebuf += c
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self.charpos += 1
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break
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m = EOL.search(self.buf, self.charpos)
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if m:
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linebuf += self.buf[self.charpos:m.end(0)]
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self.charpos = m.end(0)
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if linebuf[-1:] == b'\r':
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eol = True
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else:
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break
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else:
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linebuf += self.buf[self.charpos:]
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self.charpos = len(self.buf)
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log.debug('nextline: %r, %r', linepos, linebuf)
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return (linepos, linebuf)
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def revreadlines(self) -> Iterator[bytes]:
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"""Fetches a next line backword.
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This is used to locate the trailers at the end of a file.
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"""
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self.fp.seek(0, 2)
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pos = self.fp.tell()
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buf = b''
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while 0 < pos:
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prevpos = pos
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pos = max(0, pos-self.BUFSIZ)
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self.fp.seek(pos)
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s = self.fp.read(prevpos-pos)
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if not s:
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break
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while 1:
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n = max(s.rfind(b'\r'), s.rfind(b'\n'))
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if n == -1:
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buf = s + buf
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break
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yield s[n:] + buf
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s = s[:n]
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buf = b''
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return
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def _parse_main(self, s: bytes, i: int) -> int:
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m = NONSPC.search(s, i)
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if not m:
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return len(s)
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j = m.start(0)
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c = s[j:j+1]
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self._curtokenpos = self.bufpos+j
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if c == b'%':
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self._curtoken = b'%'
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self._parse1 = self._parse_comment
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return j+1
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elif c == b'/':
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self._curtoken = b''
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self._parse1 = self._parse_literal
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return j+1
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elif c in b'-+' or c.isdigit():
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self._curtoken = c
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self._parse1 = self._parse_number
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return j+1
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elif c == b'.':
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self._curtoken = c
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self._parse1 = self._parse_float
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return j+1
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elif c.isalpha():
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self._curtoken = c
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self._parse1 = self._parse_keyword
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return j+1
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elif c == b'(':
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self._curtoken = b''
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self.paren = 1
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self._parse1 = self._parse_string
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return j+1
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elif c == b'<':
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self._curtoken = b''
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self._parse1 = self._parse_wopen
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return j+1
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elif c == b'>':
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self._curtoken = b''
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self._parse1 = self._parse_wclose
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return j+1
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else:
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self._add_token(KWD(c))
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return j+1
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def _add_token(self, obj: PSBaseParserToken) -> None:
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self._tokens.append((self._curtokenpos, obj))
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return
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def _parse_comment(self, s: bytes, i: int) -> int:
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m = EOL.search(s, i)
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if not m:
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self._curtoken += s[i:]
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return len(s)
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j = m.start(0)
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self._curtoken += s[i:j]
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self._parse1 = self._parse_main
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# We ignore comments.
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# self._tokens.append(self._curtoken)
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return j
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def _parse_literal(self, s: bytes, i: int) -> int:
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m = END_LITERAL.search(s, i)
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if not m:
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self._curtoken += s[i:]
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return len(s)
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j = m.start(0)
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self._curtoken += s[i:j]
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c = s[j:j+1]
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if c == b'#':
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self.hex = b''
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self._parse1 = self._parse_literal_hex
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return j+1
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try:
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name: Union[str, bytes] = str(self._curtoken, 'utf-8')
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except Exception:
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name = self._curtoken
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self._add_token(LIT(name))
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self._parse1 = self._parse_main
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return j
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def _parse_literal_hex(self, s: bytes, i: int) -> int:
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c = s[i:i+1]
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if HEX.match(c) and len(self.hex) < 2:
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self.hex += c
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return i+1
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if self.hex:
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self._curtoken += bytes((int(self.hex, 16),))
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self._parse1 = self._parse_literal
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return i
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def _parse_number(self, s: bytes, i: int) -> int:
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m = END_NUMBER.search(s, i)
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if not m:
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self._curtoken += s[i:]
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return len(s)
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j = m.start(0)
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self._curtoken += s[i:j]
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c = s[j:j+1]
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if c == b'.':
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self._curtoken += c
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self._parse1 = self._parse_float
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return j+1
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try:
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self._add_token(int(self._curtoken))
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except ValueError:
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pass
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self._parse1 = self._parse_main
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return j
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def _parse_float(self, s: bytes, i: int) -> int:
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m = END_NUMBER.search(s, i)
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if not m:
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self._curtoken += s[i:]
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return len(s)
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j = m.start(0)
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self._curtoken += s[i:j]
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try:
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self._add_token(float(self._curtoken))
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except ValueError:
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pass
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self._parse1 = self._parse_main
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return j
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def _parse_keyword(self, s: bytes, i: int) -> int:
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m = END_KEYWORD.search(s, i)
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if not m:
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self._curtoken += s[i:]
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return len(s)
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j = m.start(0)
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self._curtoken += s[i:j]
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if self._curtoken == b'true':
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token: Union[bool, PSKeyword] = True
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elif self._curtoken == b'false':
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token = False
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else:
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token = KWD(self._curtoken)
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self._add_token(token)
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self._parse1 = self._parse_main
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return j
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def _parse_string(self, s: bytes, i: int) -> int:
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m = END_STRING.search(s, i)
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if not m:
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self._curtoken += s[i:]
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return len(s)
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j = m.start(0)
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self._curtoken += s[i:j]
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c = s[j:j+1]
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if c == b'\\':
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self.oct = b''
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self._parse1 = self._parse_string_1
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return j+1
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if c == b'(':
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self.paren += 1
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self._curtoken += c
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return j+1
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if c == b')':
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self.paren -= 1
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if self.paren:
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# WTF, they said balanced parens need no special treatment.
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self._curtoken += c
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return j+1
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self._add_token(self._curtoken)
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self._parse1 = self._parse_main
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return j+1
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def _parse_string_1(self, s: bytes, i: int) -> int:
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"""Parse literal strings
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PDF Reference 3.2.3
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"""
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c = s[i:i+1]
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if OCT_STRING.match(c) and len(self.oct) < 3:
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self.oct += c
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return i+1
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elif self.oct:
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self._curtoken += bytes((int(self.oct, 8),))
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self._parse1 = self._parse_string
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return i
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elif c in ESC_STRING:
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self._curtoken += bytes((ESC_STRING[c],))
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elif c == b'\r' and len(s) > i+1 and s[i+1:i+2] == b'\n':
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# If current and next character is \r\n skip both because enters
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# after a \ are ignored
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i += 1
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# default action
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self._parse1 = self._parse_string
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return i+1
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def _parse_wopen(self, s: bytes, i: int) -> int:
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c = s[i:i+1]
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if c == b'<':
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self._add_token(KEYWORD_DICT_BEGIN)
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self._parse1 = self._parse_main
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i += 1
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else:
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self._parse1 = self._parse_hexstring
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return i
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def _parse_wclose(self, s: bytes, i: int) -> int:
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c = s[i:i+1]
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if c == b'>':
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self._add_token(KEYWORD_DICT_END)
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i += 1
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self._parse1 = self._parse_main
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return i
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def _parse_hexstring(self, s: bytes, i: int) -> int:
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m = END_HEX_STRING.search(s, i)
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if not m:
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self._curtoken += s[i:]
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return len(s)
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j = m.start(0)
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self._curtoken += s[i:j]
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token = HEX_PAIR.sub(lambda m: bytes((int(m.group(0), 16),)),
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SPC.sub(b'', self._curtoken))
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self._add_token(token)
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self._parse1 = self._parse_main
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return j
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def nexttoken(self) -> Tuple[int, PSBaseParserToken]:
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while not self._tokens:
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self.fillbuf()
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self.charpos = self._parse1(self.buf, self.charpos)
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token = self._tokens.pop(0)
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log.debug('nexttoken: %r', token)
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return token
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# Stack slots may by occupied by any of:
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# * the PSBaseParserToken types
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# * list (via KEYWORD_ARRAY)
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# * dict (via KEYWORD_DICT)
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# * subclass-specific extensions (e.g. PDFStream, PDFObjRef) via ExtraT
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ExtraT = TypeVar("ExtraT")
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PSStackType = Union[float, bool, PSLiteral, bytes, List, Dict, ExtraT]
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PSStackEntry = Tuple[int, PSStackType[ExtraT]]
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class PSStackParser(PSBaseParser, Generic[ExtraT]):
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def __init__(self, fp: BinaryIO) -> None:
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PSBaseParser.__init__(self, fp)
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self.reset()
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return
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def reset(self) -> None:
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self.context: List[Tuple[int, Optional[str],
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List[PSStackEntry[ExtraT]]]] = []
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self.curtype: Optional[str] = None
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self.curstack: List[PSStackEntry[ExtraT]] = []
|
|
self.results: List[PSStackEntry[ExtraT]] = []
|
|
return
|
|
|
|
def seek(self, pos: int) -> None:
|
|
PSBaseParser.seek(self, pos)
|
|
self.reset()
|
|
return
|
|
|
|
def push(self, *objs: PSStackEntry[ExtraT]) -> None:
|
|
self.curstack.extend(objs)
|
|
return
|
|
|
|
def pop(self, n: int) -> List[PSStackEntry[ExtraT]]:
|
|
objs = self.curstack[-n:]
|
|
self.curstack[-n:] = []
|
|
return objs
|
|
|
|
def popall(self) -> List[PSStackEntry[ExtraT]]:
|
|
objs = self.curstack
|
|
self.curstack = []
|
|
return objs
|
|
|
|
def add_results(self, *objs: PSStackEntry[ExtraT]) -> None:
|
|
try:
|
|
log.debug('add_results: %r', objs)
|
|
except Exception:
|
|
log.debug('add_results: (unprintable object)')
|
|
self.results.extend(objs)
|
|
return
|
|
|
|
def start_type(self, pos: int, type: str) -> None:
|
|
self.context.append((pos, self.curtype, self.curstack))
|
|
(self.curtype, self.curstack) = (type, [])
|
|
log.debug('start_type: pos=%r, type=%r', pos, type)
|
|
return
|
|
|
|
def end_type(self, type: str) -> Tuple[int, List[PSStackType[ExtraT]]]:
|
|
if self.curtype != type:
|
|
raise PSTypeError('Type mismatch: {!r} != {!r}'
|
|
.format(self.curtype, type))
|
|
objs = [obj for (_, obj) in self.curstack]
|
|
(pos, self.curtype, self.curstack) = self.context.pop()
|
|
log.debug('end_type: pos=%r, type=%r, objs=%r', pos, type, objs)
|
|
return (pos, objs)
|
|
|
|
def do_keyword(self, pos: int, token: PSKeyword) -> None:
|
|
return
|
|
|
|
def nextobject(self) -> PSStackEntry[ExtraT]:
|
|
"""Yields a list of objects.
|
|
|
|
Arrays and dictionaries are represented as Python lists and
|
|
dictionaries.
|
|
|
|
:return: keywords, literals, strings, numbers, arrays and dictionaries.
|
|
"""
|
|
while not self.results:
|
|
(pos, token) = self.nexttoken()
|
|
if isinstance(token, (int, float, bool, str, bytes, PSLiteral)):
|
|
# normal token
|
|
self.push((pos, token))
|
|
elif token == KEYWORD_ARRAY_BEGIN:
|
|
# begin array
|
|
self.start_type(pos, 'a')
|
|
elif token == KEYWORD_ARRAY_END:
|
|
# end array
|
|
try:
|
|
self.push(self.end_type('a'))
|
|
except PSTypeError:
|
|
if settings.STRICT:
|
|
raise
|
|
elif token == KEYWORD_DICT_BEGIN:
|
|
# begin dictionary
|
|
self.start_type(pos, 'd')
|
|
elif token == KEYWORD_DICT_END:
|
|
# end dictionary
|
|
try:
|
|
(pos, objs) = self.end_type('d')
|
|
if len(objs) % 2 != 0:
|
|
error_msg = 'Invalid dictionary construct: %r' % objs
|
|
raise PSSyntaxError(error_msg)
|
|
d = {literal_name(k): v
|
|
for (k, v) in choplist(2, objs) if v is not None}
|
|
self.push((pos, d))
|
|
except PSTypeError:
|
|
if settings.STRICT:
|
|
raise
|
|
elif token == KEYWORD_PROC_BEGIN:
|
|
# begin proc
|
|
self.start_type(pos, 'p')
|
|
elif token == KEYWORD_PROC_END:
|
|
# end proc
|
|
try:
|
|
self.push(self.end_type('p'))
|
|
except PSTypeError:
|
|
if settings.STRICT:
|
|
raise
|
|
elif isinstance(token, PSKeyword):
|
|
log.debug('do_keyword: pos=%r, token=%r, stack=%r', pos,
|
|
token, self.curstack)
|
|
self.do_keyword(pos, token)
|
|
else:
|
|
log.error('unknown token: pos=%r, token=%r, stack=%r', pos,
|
|
token, self.curstack)
|
|
self.do_keyword(pos, token)
|
|
raise
|
|
if self.context:
|
|
continue
|
|
else:
|
|
self.flush()
|
|
obj = self.results.pop(0)
|
|
try:
|
|
log.debug('nextobject: %r', obj)
|
|
except Exception:
|
|
log.debug('nextobject: (unprintable object)')
|
|
return obj
|