[gentoo-portage-dev] [PATCH] INSTALL_MASK: index patterns anchored with leading slash (bug 675826)

[Zac Medico]

For scalability, use a tree structure to index patterns that are
anchored with a leading slash.

Patterns anchored with leading slash are indexed by leading non-glob
components, making it possible to minimize the number of fnmatch
calls. For example:

  /foo*/bar -> {'.': ['/foo*/bar']}

  /foo/bar* -> {'foo': {'.': ['/foo/bar*']}}

  /foo/bar/ -> {'foo': {'bar': {'.': ['/foo/bar/']}}}

Bug: https://bugs.gentoo.org/675826
Signed-off-by: Zac Medico <zmedico@g.o>
---
 lib/portage/util/install_mask.py | 78 +++++++++++++++++++++++++++++---
 1 file changed, 72 insertions(+), 6 deletions(-)

diff --git a/lib/portage/util/install_mask.py b/lib/portage/util/install_mask.py
index 32627eb05..84305644c 100644
--- a/lib/portage/util/install_mask.py
+++ b/lib/portage/util/install_mask.py
@@ -3,8 +3,11 @@
 
 __all__ = ['install_mask_dir', 'InstallMask']
 
+import collections
 import errno
 import fnmatch
+import functools
+import operator
 import sys
 
 from portage import os, _unicode_decode
@@ -18,13 +21,76 @@ else:
 	_unicode = unicode
 
 
+def _defaultdict_tree():
+	return collections.defaultdict(_defaultdict_tree)
+
+
+_pattern = collections.namedtuple('_pattern', ('orig_index', 'is_inclusive', 'pattern'))
+
+
 class InstallMask(object):
 	def __init__(self, install_mask):
 		"""
 		@param install_mask: INSTALL_MASK value
 		@type install_mask: str
 		"""
-		self._install_mask = install_mask.split()
+		# Patterns not anchored with leading slash
+		self._unanchored = []
+
+		# Patterns anchored with leading slash are indexed by leading
+		# non-glob components, making it possible to minimize the
+		# number of fnmatch calls. For example:
+		# /foo*/bar -> {'.': ['/foo*/bar']}
+		# /foo/bar* -> {'foo': {'.': ['/foo/bar*']}}
+		# /foo/bar/ -> {'foo': {'bar': {'.': ['/foo/bar/']}}}
+		self._anchored = _defaultdict_tree()
+		for orig_index, pattern in enumerate(install_mask.split()):
+			# if pattern starts with -, possibly exclude this path
+			is_inclusive = not pattern.startswith('-')
+			if not is_inclusive:
+				pattern = pattern[1:]
+			pattern_obj = _pattern(orig_index, is_inclusive, pattern)
+			# absolute path pattern
+			if pattern.startswith('/'):
+				current_dir = self._anchored
+				for component in list(filter(None, pattern.split('/'))):
+					if '*' in component:
+						break
+					else:
+						current_dir = current_dir[component]
+				current_dir.setdefault('.', []).append(pattern_obj)
+
+			# filename
+			else:
+				self._unanchored.append(pattern_obj)
+
+	def _iter_relevant_patterns(self, path):
+		"""
+		Iterate over patterns that may be relevant for the given path.
+
+		Patterns anchored with leading / are indexed by leading
+		non-glob components, making it possible to minimize the
+		number of fnmatch calls.
+		"""
+		current_dir = self._anchored
+		components = list(filter(None, path.split('/')))
+		patterns = []
+		patterns.extend(current_dir.get('.', []))
+		for component in components:
+			next_dir = current_dir.get(component, None)
+			if next_dir is None:
+				break
+			current_dir = next_dir
+			patterns.extend(current_dir.get('.', []))
+
+		if patterns:
+			# Sort by original pattern index, since order matters for
+			# non-inclusive patterns.
+			patterns.extend(self._unanchored)
+			patterns.sort(key=operator.attrgetter('orig_index'))
+			return iter(patterns)
+
+		return iter(self._unanchored)
 
 	def match(self, path):
 		"""
@@ -34,11 +100,10 @@ class InstallMask(object):
 		@return: True if path matches INSTALL_MASK, False otherwise
 		"""
 		ret = False
-		for pattern in self._install_mask:
-			# if pattern starts with -, possibly exclude this path
-			is_inclusive = not pattern.startswith('-')
-			if not is_inclusive:
-				pattern = pattern[1:]
+
+		for pattern_obj in self._iter_relevant_patterns(path):
+			is_inclusive = pattern_obj.is_inclusive
+			pattern = pattern_obj.pattern
 			# absolute path pattern
 			if pattern.startswith('/'):
 				# handle trailing slash for explicit directory match
@@ -49,6 +114,7 @@ class InstallMask(object):
 				if (fnmatch.fnmatch(path, pattern[1:])
 						or fnmatch.fnmatch(path, pattern[1:].rstrip('/') + '/*')):
 					ret = is_inclusive
+
 			# filename
 			else:
 				if fnmatch.fnmatch(os.path.basename(path), pattern):
-- 
2.18.1