- parsers.py: string slicing replaces by toolkit.StringView

DHParser/parser.py

@@ -77,7 +77,8 @@ except ImportError:
 from DHParser.toolkit import is_logging, log_dir, logfile_basename, escape_re, sane_parser_name
 from DHParser.syntaxtree import WHITESPACE_PTYPE, TOKEN_PTYPE, ZOMBIE_PARSER, ParserBase, \
     Node, TransformationFunc
-from DHParser.toolkit import TextView, load_if_file, error_messages, line_col
+from DHParser.toolkit import StringView, EMPTY_STRING_VIEW, sv_match, sv_index, sv_search, \
+    load_if_file, error_messages, line_col
 
 __all__ = ('PreprocessorFunc',
            'HistoryRecord',
@@ -161,7 +162,7 @@ class HistoryRecord:
         # type: List['Parser']
         self.node = node                # type: Node
         self.remaining = remaining      # type: int
-        document = call_stack[-1].grammar.document__ if call_stack else ''
+        document = call_stack[-1].grammar.document__.text if call_stack else ''
         self.line_col = line_col(document, len(document) - remaining)  # type: Tuple[int, int]
 
     def __str__(self):
@@ -229,11 +230,13 @@ def add_parser_guard(parser_func):
     that takes care of memoizing, left recursion and optionally tracing
     (aka "history tracking") of parser calls. Returns the wrapped call.
     """
-    def guarded_call(parser: 'Parser', text: str) -> Tuple[Node, str]:
+    def guarded_call(parser: 'Parser', text: StringView) -> Tuple[Node, StringView]:
+        assert isinstance(text, StringView)
+
         def memoized(parser, location):
             node = parser.visited[location]
             rlen = location - (0 if node is None else node.len)
-            rest = TextView(grammar.document__, -rlen) if rlen else ''
+            rest = grammar.document__[-rlen:] if rlen else EMPTY_STRING_VIEW
             return node, rest
             # NOTE: An older and simpler implementation of memoization
             # relied on `parser.visited[location] == node, rest`. Although,
@@ -267,6 +270,7 @@ def add_parser_guard(parser_func):
 
             # run original __call__ method
             node, rest = parser_func(parser, text)
+            assert isinstance(rest, StringView)
 
             if node is None:
                 # retrieve an earlier match result (from left recursion) if it exists
@@ -302,7 +306,7 @@ def add_parser_guard(parser_func):
             node = Node(None, text[:min(10, max(1, text.find("\n")))] + " ...")
             node.add_error("maximum recursion depth of parser reached; "
                            "potentially due to too many errors!")
-            rest = ''
+            rest = EMPTY_STRING_VIEW
 
         return node, rest
 
@@ -409,7 +413,7 @@ class Parser(ParserBase, metaclass=ParserMetaClass):
         self.cycle_detection = set()     # type: Set[Callable]
         return self
 
-    def __call__(self, text: TextView) -> Tuple[Node, TextView]:
+    def __call__(self, text: StringView) -> Tuple[Node, StringView]:
         """Applies the parser to the given `text` and returns a node with
         the results or None as well as the text at the position right behind
         the matching string."""
@@ -724,8 +728,8 @@ class Grammar:
 
 
     def _reset__(self):
-        self.document__ = ""          # type: str
-        self._reversed__ = ""         # type: str
+        self.document__ = EMPTY_STRING_VIEW   # type: StringView
+        self._reversed__ = EMPTY_STRING_VIEW  # type: StringView
         # variables stored and recalled by Capture and Retrieve parsers
         self.variables__ = dict()     # type: Dict[str, List[str]]
         self.rollback__ = []          # type: List[Tuple[int, Callable]]
@@ -742,7 +746,7 @@ class Grammar:
     @property
     def reversed__(self) -> str:
         if not self._reversed__:
-            self._reversed__ = self.document__[::-1]
+            self._reversed__ = StringView(self.document__.text[::-1])
         return self._reversed__
 
 
@@ -784,13 +788,13 @@ class Grammar:
         else:
             self._dirty_flag__ = True
         self.history_tracking__ = is_logging()
-        self.document__ = document
-        self.last_rb__loc__ = len(document) + 1  # rollback location
+        self.document__ = StringView(document)
+        self.last_rb__loc__ = len(self.document__) + 1  # rollback location
         parser = self[start_parser] if isinstance(start_parser, str) else start_parser
         assert parser.grammar == self, "Cannot run parsers from a different grammar object!" \
                                        " %s vs. %s" % (str(self), str(parser.grammar))
         stitches = []  # type: List[Node]
-        rest = document
+        rest = self.document__
         if not rest:
             result, ignore = parser(rest)
             if result is None:
@@ -883,7 +887,7 @@ class Grammar:
         document. 
         """
         def prepare_line(record):
-            excerpt = self.document__.__getitem__(record.extent)[:25].replace('\n', '\\n')
+            excerpt = self.document__.text.__getitem__(record.extent)[:25].replace('\n', '\\n')
             excerpt = "'%s'" % excerpt if len(excerpt) < 25 else "'%s...'" % excerpt
             return record.stack, record.status, excerpt
 
@@ -985,7 +989,7 @@ class PreprocessorToken(Parser):
         assert RX_PREPROCESSOR_TOKEN.match(token)
         super(PreprocessorToken, self).__init__(token)
 
-    def __call__(self, text: str) -> Tuple[Node, str]:
+    def __call__(self, text: StringView) -> Tuple[Node, StringView]:
         if text[0:1] == BEGIN_TOKEN:
             end = text.find(END_TOKEN, 1)
             if end < 0:
@@ -1040,10 +1044,10 @@ class RegExp(Parser):
             regexp = self.regexp.pattern
         return RegExp(regexp, self.name)
 
-    def __call__(self, text: str) -> Tuple[Node, str]:
-        match = text[0:1] != BEGIN_TOKEN and self.regexp.match(text)  # ESC starts a preprocessor token.
+    def __call__(self, text: StringView) -> Tuple[Node, StringView]:
+        match = text[0:1] != BEGIN_TOKEN and sv_match(self.regexp, text)  # ESC starts a preprocessor token.
         if match:
-            end = match.end()
+            end = sv_index(match.end(), text)
             return Node(self, text[:end]), text[end:]
         return None, text
 
@@ -1114,9 +1118,9 @@ class RE(Parser):
             regexp = self.main.regexp.pattern
         return self.__class__(regexp, self.wL, self.wR, self.name)
 
-    def __call__(self, text: str) -> Tuple[Node, str]:
+    def __call__(self, text: StringView) -> Tuple[Node, StringView]:
         # assert self.main.regexp.pattern != "@"
-        t = text    # type: str
+        t = text    # type: StringView
         wL, t = self.wspLeft(t)
         main, t = self.main(t)
         if main:
@@ -1264,7 +1268,7 @@ class Optional(UnaryOperator):
             "Nesting options with required elements is contradictory: " \
             "%s(%s)" % (str(name), str(parser.name))
 
-    def __call__(self, text: str) -> Tuple[Node, str]:
+    def __call__(self, text: StringView) -> Tuple[Node, StringView]:
         node, text = self.parser(text)
         if node:
             return Node(self, node), text
@@ -1289,7 +1293,7 @@ class ZeroOrMore(Optional):
     EBNF-Notation: `{ ... }`
     EBNF-Example:  `sentence = { /\w+,?/ } "."`
     """
-    def __call__(self, text: str) -> Tuple[Node, str]:
+    def __call__(self, text: StringView) -> Tuple[Node, StringView]:
         results = ()  # type: Tuple[Node, ...]
         n = len(text) + 1
         while text and len(text) < n:
@@ -1314,9 +1318,9 @@ class OneOrMore(UnaryOperator):
             "Use ZeroOrMore instead of nesting OneOrMore and Optional: " \
             "%s(%s)" % (str(name), str(parser.name))
 
-    def __call__(self, text: str) -> Tuple[Node, str]:
+    def __call__(self, text: StringView) -> Tuple[Node, StringView]:
         results = ()  # type: Tuple[Node, ...]
-        text_ = text  # type: str
+        text_ = text  # type: StringView
         n = len(text) + 1
         while text_ and len(text_) < n:
             n = len(text_)
@@ -1340,9 +1344,9 @@ class Series(NaryOperator):
         super(Series, self).__init__(*parsers, name=name)
         assert len(self.parsers) >= 1
 
-    def __call__(self, text: str) -> Tuple[Node, str]:
+    def __call__(self, text: StringView) -> Tuple[Node, StringView]:
         results = ()  # type: Tuple[Node, ...]
-        text_ = text  # type: str
+        text_ = text  # type: StringView
         for parser in self.parsers:
             node, text_ = parser(text_)
             if not node:
@@ -1400,7 +1404,7 @@ class Alternative(NaryOperator):
         assert all(not isinstance(p, Optional) for p in self.parsers[:-1])
         self.been_here = dict()  # type: Dict[int, int]
 
-    def __call__(self, text: str) -> Tuple[Node, str]:
+    def __call__(self, text: StringView) -> Tuple[Node, StringView]:
         for parser in self.parsers:
             node, text_ = parser(text)
             if node:
@@ -1447,11 +1451,13 @@ class FlowOperator(UnaryOperator):
 
 class Required(FlowOperator):
     # Add constructor that checks for logical errors, like `Required(Optional(...))` constructs ?
-    def __call__(self, text: str) -> Tuple[Node, str]:
+    RX_ARGUMENT = re.compile(r'\s(\S)')
+
+    def __call__(self, text: StringView) -> Tuple[Node, StringView]:
         node, text_ = self.parser(text)
         if not node:
-            m = re.search(r'\s(\S)', text)
-            i = max(1, m.regs[1][0]) if m else 1
+            m = sv_search(Required.RX_ARGUMENT, text)  # re.search(r'\s(\S)', text)
+            i = max(1, sv_index(m.regs[1][0], text)) if m else 1
             node = Node(self, text[:i])
             text_ = text[i:]
             # assert False, "*"+text[:i]+"*"
@@ -1467,7 +1473,7 @@ class Lookahead(FlowOperator):
     def __init__(self, parser: Parser, name: str = '') -> None:
         super(Lookahead, self).__init__(parser, name)
 
-    def __call__(self, text: str) -> Tuple[Node, str]:
+    def __call__(self, text: StringView) -> Tuple[Node, StringView]:
         node, text_ = self.parser(text)
         if self.sign(node is not None):
             return Node(self, ''), text
@@ -1512,9 +1518,9 @@ class Lookbehind(FlowOperator):
         self.regexp = p.main.regexp if isinstance(p, RE) else p.regexp
         super(Lookbehind, self).__init__(parser, name)
 
-    def __call__(self, text: str) -> Tuple[Node, str]:
+    def __call__(self, text: StringView) -> Tuple[Node, StringView]:
         backwards_text = self.grammar.reversed__[len(text):]  # self.grammar.document__[-len(text) - 1::-1]
-        if self.sign(self.regexp.match(backwards_text)):
+        if self.sign(sv_match(self.regexp, backwards_text)):
             return Node(self, ''), text
         else:
             return None, text
@@ -1548,7 +1554,7 @@ class Capture(UnaryOperator):
     def __init__(self, parser: Parser, name: str = '') -> None:
         super(Capture, self).__init__(parser, name)
 
-    def __call__(self, text: str) -> Tuple[Node, str]:
+    def __call__(self, text: StringView) -> Tuple[Node, StringView]:
         node, text_ = self.parser(text)
         if node:
             stack = self.grammar.variables__.setdefault(self.name, [])
@@ -1590,13 +1596,13 @@ class Retrieve(Parser):
     def __deepcopy__(self, memo):
         return self.__class__(self.symbol, self.filter, self.name)
 
-    def __call__(self, text: str) -> Tuple[Node, str]:
+    def __call__(self, text: StringView) -> Tuple[Node, StringView]:
         return self.call(text)  # allow call method to be called from subclass circumventing the parser guard
 
     def __repr__(self):
         return ':' + self.symbol.repr
 
-    def call(self, text: str) -> Tuple[Node, str]:
+    def call(self, text: StringView) -> Tuple[Node, StringView]:
         try:
             stack = self.grammar.variables__[self.symbol.name]
             value = self.filter(stack)
@@ -1612,7 +1618,7 @@ class Retrieve(Parser):
 class Pop(Retrieve):
     """STILL EXPERIMENTAL!!!"""
 
-    def __call__(self, text: str) -> Tuple[Node, str]:
+    def __call__(self, text: StringView) -> Tuple[Node, StringView]:
         nd, txt = super(Pop, self).call(text)  # call() instead of __call__() to avoid parser guard
         if nd and not nd.error_flag:
             stack = self.grammar.variables__[self.symbol.name]
@@ -1644,7 +1650,7 @@ class Synonym(UnaryOperator):
     class, in which case it would be unclear whether the parser
     RE('\d\d\d\d') carries the name 'JAHRESZAHL' or 'jahr'.
     """
-    def __call__(self, text: str) -> Tuple[Node, str]:
+    def __call__(self, text: StringView) -> Tuple[Node, StringView]:
         node, text = self.parser(text)
         if node:
             return Node(self, node), text
@@ -1684,7 +1690,7 @@ class Forward(Parser):
         duplicate.set(parser)
         return duplicate
 
-    def __call__(self, text: str) -> Tuple[Node, str]:
+    def __call__(self, text: StringView) -> Tuple[Node, StringView]:
         return self.parser(text)
 
     def __repr__(self):

DHParser/syntaxtree.py

@@ -31,7 +31,7 @@ except ImportError:
     from .typing34 import AbstractSet, Any, ByteString, Callable, cast, Container, Dict, \
         Iterator, List, NamedTuple, Sequence, Union, Text, Tuple
 
-from DHParser.toolkit import is_logging, log_dir, TextView, line_col, identity
+from DHParser.toolkit import is_logging, log_dir, StringView, line_col, identity
 
 __all__ = ('WHITESPACE_PTYPE',
            'MockParser',
@@ -129,8 +129,8 @@ ZOMBIE_PARSER = ZombieParser()
 Error = NamedTuple('Error', [('pos', int), ('msg', str)])
 
 ChildrenType = Tuple['Node', ...]
-StrictResultType = Union[ChildrenType, TextView, str]
-ResultType = Union[ChildrenType, 'Node', TextView, str, None]
+StrictResultType = Union[ChildrenType, StringView, str]
+ResultType = Union[ChildrenType, 'Node', StringView, str, None]
 
 
 def flatten_sxpr(sxpr: str) -> str:
@@ -189,6 +189,7 @@ class Node:
 
     __slots__ = ['_result', 'children', '_errors', '_len', '_pos', 'parser', 'error_flag']
 
+
     def __init__(self, parser, result: ResultType) -> None:
         """Initializes the ``Node``-object with the ``Parser``-Instance
         that generated the node and the parser's result.
@@ -251,7 +252,7 @@ class Node:
         #         or isinstance(result, Node)
         #         or isinstance(result, str)), str(result)
         self._result = (result,) if isinstance(result, Node) else str(result) \
-            if isinstance(result, TextView) else result or ''  # type: StrictResultType
+            if isinstance(result, StringView) else result or ''  # type: StrictResultType
         self.children = cast(ChildrenType, self._result) \
             if isinstance(self._result, tuple) else cast(ChildrenType, ())  # type: ChildrenType
         self.error_flag = any(r.error_flag for r in self.children)  # type: bool

DHParser/toolkit.py

@@ -43,14 +43,18 @@ except ImportError:
 import sys
 
 try:
-    from typing import Any, List, Tuple, Optional
+    from typing import Any, List, Tuple, Collection, Union, Optional
 except ImportError:
-    from .typing34 import Any, List, Tuple, Optional
+    from .typing34 import Any, List, Tuple, Collection, Union, Optional
 
 __all__ = ('logging',
            'is_logging',
            'log_dir',
            'logfile_basename',
+           'StringView',
+           'sv_match',
+           'sv_index',
+           'sv_search',
            # 'supress_warnings',
            # 'warnings',
            # 'repr_call',
@@ -150,22 +154,93 @@ def clear_logs(logfile_types={'.cst', '.ast', '.log'}):
         os.rmdir(log_dirname)
 
 
-class TextView:
-    __slots__ = ['text', 'begin', 'end']
+class StringView:
+    """"A rudimentary StringView class, just enough for the use cases
+    in parswer.py.
+
+    Slicing Python-strings always yields copies of a segment of the original
+    string. See: https://mail.python.org/pipermail/python-dev/2008-May/079699.html
+    However, this becomes costly (in terms of space and as a consequence also
+    time) when parsing longer documents. Unfortunately, Python's `memoryview`
+    does not work for unicode strings. Hence, the StringView class.
+    """
+
+    __slots__ = ['text', 'begin', 'end', 'len']
 
     def __init__(self, text: str, begin: Optional[int] = 0, end: Optional[int] = None) -> None:
         self.text = text  # type: str
-        self.begin = begin or 0  # type: int # TODO: Negative Values!!!
-        self.end = end or len(text)  # type: int
+        self.begin, self.end = StringView.real_indices(begin, end, len(text))
+        self.len = max(self.end - self.begin, 0)
+
+    @staticmethod
+    def real_indices(begin, end, len):
+        def pack(index, len):
+            index = index if index >= 0 else index + len
+            return 0 if index < 0 else len if index > len else index
+        if begin is None:  begin = 0
+        if end is None:  end = len
+        return pack(begin, len), pack(end, len)
+
+    def __bool__(self):
+        return bool(self.text) and self.end > self.begin
+
+    def __len__(self):
+        return self.len
 
     def __str__(self):
         return self.text[self.begin:self.end]
 
     def __getitem__(self, index):
-        assert isinstance(index, slice), "Minimal implementation of TextView just allows slicing."
-        start = index.start or 0
-        stop = index.stop or (self.end - self.begin)
-        return TextView(self.text, self.begin + start, self.begin + stop)
+        assert isinstance(index, slice), "As of now, StringView only allows slicing."
+        assert index.step is None or index.step == 1, \
+            "Step sizes other than 1 are not yet supported by StringView"
+        start, stop = StringView.real_indices(index.start, index.stop, self.len)
+        return StringView(self.text, self.begin + start, self.begin + stop)
+
+    def __eq__(self, other):
+        return str(self) == str(other)  # PERFORMANCE WARNING: This creates copies of the strings
+
+    def find(self, sub, start=None, end=None) -> int:
+        if start is None and end is None:
+            return self.text.find(sub, self.begin, self.end) - self.begin
+        else:
+            start, end = StringView.real_indices(start, end, self.len)
+            return self.text.find(sub, self.begin + start, self.begin + end) - self.begin
+
+    def startswith(self, prefix: str, start:int = 0, end:Optional[int] = None) -> bool:
+        start += self.begin
+        end = self.end if end is None else self.begin + end
+        return self.text.startswith(prefix, start, end)
+
+
+
+def sv_match(regex, sv: StringView):
+    return regex.match(sv.text, pos=sv.begin, endpos=sv.end)
+
+
+def sv_index(absolute_index: Union[int, Collection], sv: StringView) -> Union[int, tuple]:
+    """
+    Converts the an index into string watched by a StringView object
+    to an index relativ to the string view object, e.g.:
+    >>> sv = StringView('xxIxx')[2:3]
+    >>> match = sv_match(re.compile('I'), sv)
+    >>> match.end()
+    3
+    >>> sv_index(match.end(), sv)
+    1
+    """
+    try:
+        return absolute_index - sv.begin
+    except TypeError:
+        return tuple(index - sv.begin for index in absolute_index)
+
+
+def sv_search(regex, sv: StringView):
+    return regex.search(sv.text, pos=sv.begin, endpos=sv.end)
+
+
+
+EMPTY_STRING_VIEW = StringView('')
 
 
 # def repr_call(f, parameter_list) -> str:

examples/LaTeX/tst_LaTeX_docs.py

@@ -49,7 +49,7 @@ def fail_on_error(src, result):
         sys.exit(1)
 
 
-def test():
+def tst_func():
     with toolkit.logging(False):
         files = os.listdir('testdata')
         files.sort()
@@ -87,7 +87,8 @@ def mem_profile(func):
         print(stat)
 
 if __name__ == "__main__":
-    cpu_profile(test)
+    cpu_profile(tst_func)
+
 
 
 

test/test_DHParser.py

@@ -26,4 +26,5 @@ sys.path.extend(['../', './'])
 if __name__ == "__main__":
     from DHParser.testing import runner
 
-    runner("", globals())
\ No newline at end of file
+    runner("", globals())
+

test/test_parser.py

@@ -24,7 +24,7 @@ from functools import partial
 
 sys.path.extend(['../', './'])
 
-from DHParser.toolkit import is_logging, logging, compile_python_object
+from DHParser.toolkit import is_logging, logging, StringView, compile_python_object
 from DHParser.parser import compile_source, Retrieve, Grammar, Forward, Token, ZeroOrMore, RE, \
     RegExp, Lookbehind, NegativeLookahead, OneOrMore, Series
 from DHParser.ebnf import get_ebnf_grammar, get_ebnf_transformer, get_ebnf_compiler
@@ -152,7 +152,7 @@ class TestRegex:
         assert result
         assert not messages, str(messages)
         parser = compile_python_object(DHPARSER_IMPORTS + result, '\w+Grammar$')()
-        node, rest = parser.regex('abc+def')
+        node, rest = parser.regex(StringView('abc+def'))
         assert rest == ''
         assert node.parser.name == "regex"
         assert str(node) == 'abc+def'

test/test_syntaxtree.py

@@ -97,6 +97,7 @@ class TestNode:
         transform = get_ebnf_transformer()
         compiler = get_ebnf_compiler()
         tree = parser(ebnf)
+        print(tree.as_sxpr())
         tree_copy = copy.deepcopy(tree)
         transform(tree_copy)
         res1 = compiler(tree_copy)

test/test_toolkit.py

@@ -23,9 +23,112 @@ limitations under the License.
 import concurrent.futures
 import os
 import sys
+try:
+    import regex as re
+except ImportError:
+    import re
+
 sys.path.extend(['../', './'])
 
-from DHParser.toolkit import load_if_file, logging, log_dir, is_logging
+from DHParser.toolkit import load_if_file, logging, log_dir, is_logging, StringView, \
+    sv_match, sv_search, EMPTY_STRING_VIEW
+
+
+class TestStringView:
+    def test_real_indices(self):
+        assert StringView.real_indices(3, 5, 10) == (3, 5)
+        assert StringView.real_indices(None, None, 10) == (0, 10)
+        assert StringView.real_indices(-2, -1, 10) == (8, 9)
+        assert StringView.real_indices(-3, 11, 10) == (7, 10)
+        assert StringView.real_indices(-5, -12, 10) == (5, 0)
+        assert StringView.real_indices(-12, -5, 10) == (0, 5)
+        assert StringView.real_indices(7, 6, 10) == (7, 6)
+        assert StringView.real_indices(None, 0, 10) == (0, 0)
+
+    def test_creation(self):
+        s = "0123456789"
+        assert str(StringView(s)) == s
+        assert str(StringView(s, 3, 4)) == '3'
+        assert str(StringView(s, -4)) == '6789'
+
+    def test_equality(self):
+        s = "0123456789"
+        assert StringView(s) == s
+        assert StringView(s, 3, 4) == '3'
+        assert StringView(s, -4) == '6789'
+
+    def test_slicing(self):
+        s = " 0123456789 "
+        sv = StringView(s, 1, -1)
+        assert sv == '0123456789'
+        assert sv[3:4] == '3'
+        assert sv[-3:-1] == '78'
+        assert sv[4:3] == ''
+        assert sv[:4] == '0123'
+        assert sv[4:] == '456789'
+        assert sv[-2:] == '89'
+        assert sv[:-5] == '01234'
+        assert isinstance(sv[3:5], StringView)
+
+    def test_len(self):
+        s = " 0123456789 "
+        sv = StringView(s, 1, -1)
+        assert len(sv) == 10
+        assert sv.len == 10
+        assert len(sv[5:5]) == 0
+        assert len(sv[7:4]) == 0
+        assert len(sv[-12:-2]) == 8
+        assert len(sv[-12:12]) == 10
+
+    def test_bool(self):
+        assert not StringView('')
+        assert StringView('x')
+        s = " 0123456789 "
+        sv = StringView(s, 1, -1)
+        assert not sv[5:4]
+        assert sv[4:5], str(sv[4:5])
+        assert not sv[3:3]
+        assert not sv[12:13]
+        assert sv[0:20]
+
+    def test_sv_match(self):
+        s = " 0123456789 "
+        sv = StringView(s, 1, -1)
+        assert sv_match(re.compile(r'\d'), sv)
+        assert sv_match(re.compile(r'\d+'), sv)
+        assert not sv_match(re.compile(r' '), sv)
+        assert sv_match(re.compile(r'45'), sv[4:])
+
+    def test_sv_search(self):
+        s = " 0123456789 "
+        sv = StringView(s, 1, -1)
+        assert sv_search(re.compile(r'5'), sv)
+        assert not sv_search(re.compile(r' '), sv)
+        assert sv_search(re.compile(r'5'), sv[5:])
+        assert not sv_search(re.compile(r'9'), sv[:9])
+
+    def test_find(self):
+        s = " 0123456789 "
+        sv = StringView(s, 1, -1)
+        assert sv.find('5') == 5
+        assert sv.find(' ') < 0
+        assert sv.find('0', 1)  < 0
+        assert sv.find('9', 0, 8) < 0
+        assert sv.find('45', 1, 8) == 4
+
+    def test_startswith(self):
+        s = " 0123456789 "
+        sv = StringView(s, 1, -1)
+        assert sv.startswith('012')
+        assert sv.startswith('123', 1)
+        assert not sv.startswith('123', 1, 3)
+
+    def test_EMPTY_STRING_VIEW(self):
+        assert len(EMPTY_STRING_VIEW) == 0
+        assert EMPTY_STRING_VIEW.find('x') < 0
+        assert not sv_match(re.compile(r'x'), EMPTY_STRING_VIEW)
+        assert sv_match(re.compile(r'.*'), EMPTY_STRING_VIEW)
+        assert len(EMPTY_STRING_VIEW[0:1]) == 0