Implementation of a Matching strategy for URLs in the Declarative WebRequest API.

chrome/browser/extensions/api/declarative/url_matcher.cc

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/extensions/api/declarative/url_matcher.h"
+
+#include <algorithm>
+
+#include "base/logging.h"
+#include "googleurl/src/gurl.h"
+
+namespace extensions {
+
+// This set of classes implement a mapping of URL Component Patterns, such as
+// host_prefix, host_suffix, host_equals, ..., etc., to SubstringPatterns.
+//
+// The idea of this mapping is to reduce the problem of comparing many
+// URL Component Patterns against one URL to the problem of searching many
+// substrings in one string:
+//
+// ----------------------                    --------------------
+// | URL Query operator | ----translate----> | SubstringPattern |
+// ----------------------                    --------------------
+//                                                    ^
+//                                                    |
+//                                                 compare
+//                                                    |
+//                                                    v
+// ----------------------                    --------------------
+// | URL to compare     |                    |                  |
+// | to all URL Query   | ----translate----> | String           |
+// | operators          |                    |                  |
+// ----------------------                    --------------------
+//
+// The reason for this problem reduction is that there are efficient algorithms
+// for searching many substrings in one string (see Aho-Corasick algorithm).
+//
+// Case 1: {host,path,query}_{prefix,suffix,equals} searches.
+// ==========================================================
+//
+// For searches in this class, we normalize URLs as follows:
+//
+// Step 1:
+// Remove scheme, port and segment from URL:
+// -> http://www.example.com:8080/index.html?search=foo#first_match becomes
+//    www.example.com/index.html?search=foo
+//
+// We remove the scheme and port number because they can be checked later
+// in a secondary filter step. We remove the segment (the #... part) because
+// this is not guaranteed to be ASCII-7 encoded.
+//
+// Step 2:
+// Translate URL to String and add the following position markers:
+// - BU = Beginning of URL
+// - ED = End of Domain
+// - EP = End of Path
+// - EU = End of URL
+// Furthermore, the hostname is canonicalized to start with a ".".
+//
+// Position markers are represented as characters >127, which are therefore
+// guaranteed not to be part of the ASCII-7 encoded URL character set.
+//
+// -> www.example.com/index.html?search=foo becomes
+// BU .www.example.com ED /index.html EP ?search=foo EU
+//
+// -> www.example.com/index.html becomes
+// BU .www.example.com ED /index.html EP EU
+//
+// Step 3:
+// Translate URL Component Patterns as follows:
+//
+// host_prefix(prefix) = BU add_missing_dot_prefix(prefix)
+// -> host_prefix("www.example") = BU .www.example
+//
+// host_suffix(suffix) = suffix ED
+// -> host_suffix("example.com") = example.com ED
+// -> host_suffix(".example.com") = .example.com ED
+//
+// host_equals(domain) = BU add_missing_dot_prefix(domain) ED
+// -> host_equals("www.example.com") = BU .www.example.com ED
+//
+// Similarly for path query parameters ({path, query}_{prefix, suffix, equals}).
+//
+// With this, we can search the SubstringPatterns in the normalized URL.
+//
+//
+// Case 2: url_{prefix,suffix,equals,contains} searches.
+// =====================================================
+//
+// Step 1: as above
+//
+// Step 2:
+// Translate URL to String and add the following position markers:
+// - BU = Beginning of URL
+// - EU = End of URL
+// Furthermore, the hostname is canonicalized to start with a ".".
+//
+// -> www.example.com/index.html?search=foo becomes
+// BU .www.example.com/index.html?search=foo EU
+//
+// url_prefix(prefix) = BU add_missing_dot_prefix(prefix)
+// -> url_prefix("www.example") = BU .www.example
+//
+// url_contains(substring) = substring
+// -> url_contains("index") = index
+//
+//
+// Case 3: {host,path,query}_contains searches.
+// ============================================
+//
+// These kinds of searches are not supported directly but can be derived
+// by a combination of a url_contains() query followed by an explicit test:
+//
+// host_contains(str) = url_contains(str) followed by test whether str occurs
+//   in host comonent of original URL.
+// -> host_contains("example.co") = example.co
+//    followed by gurl.host().find("example.co");
+//
+// [similarly for path_contains and query_contains].
+
+
+//
+// URLMatcherCondition
+//
+
+URLMatcherCondition::URLMatcherCondition()
+    : criterion_(HOST_PREFIX),
+      substring_pattern_(NULL) {}
+
+URLMatcherCondition::~URLMatcherCondition() {}
+
+URLMatcherCondition::URLMatcherCondition(
+    Criterion criterion,
+    const SubstringPattern* substring_pattern)
+    : criterion_(criterion),
+      substring_pattern_(substring_pattern) {}
+
+URLMatcherCondition::URLMatcherCondition(const URLMatcherCondition& rhs)
+    : criterion_(rhs.criterion_),
+      substring_pattern_(rhs.substring_pattern_) {}
+
+URLMatcherCondition& URLMatcherCondition::operator=(
+    const URLMatcherCondition& rhs) {
+  criterion_ = rhs.criterion_;
+  substring_pattern_ = rhs.substring_pattern_;
+  return *this;
+}
+
+bool URLMatcherCondition::operator<(const URLMatcherCondition& rhs) const {
+  if (criterion_ < rhs.criterion_) return true;
+  if (criterion_ > rhs.criterion_) return false;
+  if (substring_pattern_ != NULL && rhs.substring_pattern_ != NULL)
+    return *substring_pattern_ < *rhs.substring_pattern_;
+  if (substring_pattern_ == NULL && rhs.substring_pattern_ != NULL) return true;
+  // Either substring_pattern_ != NULL && rhs.substring_pattern_ == NULL,
+  // or both are NULL.
+  return false;
+}
+
+bool URLMatcherCondition::IsFullURLCondition() const {
+  // For these criteria the SubstringMatcher needs to be executed on the
+  // GURL that is canonlizaliced with
+  // URLMatcherConditionFactory::CanonicalizeURLForFullSearches.
+  switch (criterion_) {
+    case HOST_CONTAINS:
+    case PATH_CONTAINS:
+    case QUERY_CONTAINS:
+    case URL_PREFIX:
+    case URL_SUFFIX:
+    case URL_CONTAINS:
+    case URL_EQUALS:
+      return true;
+    default:
+      break;
+  }
+  return false;
+}
+
+bool URLMatcherCondition::IsMatch(
+    const std::set<SubstringPattern::ID>& matching_substring_patterns,
+    const GURL& url) const {
+  DCHECK(substring_pattern_);
+  if (matching_substring_patterns.find(substring_pattern_->id()) ==
+      matching_substring_patterns.end())
+    return false;
+  // The criteria HOST_CONTAINS, PATH_CONTAINS, QUERY_CONTAINS are based on
+  // a substring match on the raw URL. In case of a match, we need to verify
+  // that the match was found in the correct component of the URL.
+  switch (criterion_) {
+    case HOST_CONTAINS:
+      return url.host().find(substring_pattern_->pattern()) !=
+          std::string::npos;
+    case PATH_CONTAINS:
+      return url.path().find(substring_pattern_->pattern()) !=
+          std::string::npos;
+    case QUERY_CONTAINS:
+      return url.query().find(substring_pattern_->pattern()) !=
+          std::string::npos;
+    default:
+      break;
+  }
+  return true;
+}
+
+//
+// URLMatcherConditionFactory
+//
+
+namespace {
+// These are symbols that are not contained in 7-bit ASCII used in GURLs.
+const char kBeginningOfURL[] = {-1, 0};
+const char kEndOfDomain[] = {-2, 0};
+const char kEndOfPath[] = {-3, 0};
+const char kEndOfURL[] = {-4, 0};
+}  // namespace
+
+URLMatcherConditionFactory::URLMatcherConditionFactory() : id_counter_(0) {}
+
+URLMatcherConditionFactory::~URLMatcherConditionFactory() {
+  STLDeleteElements(&pattern_singletons_);
+}
+
+std::string URLMatcherConditionFactory::CanonicalizeURLForComponentSearches(
+    const GURL& url) {
+  return kBeginningOfURL + CanonicalizeHostname(url.host()) + kEndOfDomain +
+      url.path() + kEndOfPath + (url.has_query() ? "?" + url.query() : "") +
+      kEndOfURL;
+}
+
+URLMatcherCondition URLMatcherConditionFactory::CreateHostPrefixCondition(
+    const std::string& prefix) {
+  return CreateCondition(URLMatcherCondition::HOST_PREFIX,
+      kBeginningOfURL + CanonicalizeHostname(prefix));
+}
+
+URLMatcherCondition URLMatcherConditionFactory::CreateHostSuffixCondition(
+    const std::string& suffix) {
+  return CreateCondition(URLMatcherCondition::HOST_SUFFIX,
+      suffix + kEndOfDomain);
+}
+
+URLMatcherCondition URLMatcherConditionFactory::CreateHostContainsCondition(
+    const std::string& str) {
+  return CreateCondition(URLMatcherCondition::HOST_CONTAINS, str);
+}
+
+URLMatcherCondition URLMatcherConditionFactory::CreateHostEqualsCondition(
+    const std::string& str) {
+  return CreateCondition(URLMatcherCondition::HOST_EQUALS,
+      kBeginningOfURL + CanonicalizeHostname(str) + kEndOfDomain);
+}
+
+URLMatcherCondition URLMatcherConditionFactory::CreatePathPrefixCondition(
+    const std::string& prefix) {
+  return CreateCondition(URLMatcherCondition::PATH_PREFIX,
+      kEndOfDomain + prefix);
+}
+
+URLMatcherCondition URLMatcherConditionFactory::CreatePathSuffixCondition(
+    const std::string& suffix) {
+  return CreateCondition(URLMatcherCondition::HOST_SUFFIX, suffix + kEndOfPath);
+}
+
+URLMatcherCondition URLMatcherConditionFactory::CreatePathContainsCondition(
+    const std::string& str) {
+  return CreateCondition(URLMatcherCondition::PATH_CONTAINS, str);
+}
+
+URLMatcherCondition URLMatcherConditionFactory::CreatePathEqualsCondition(
+    const std::string& str) {
+  return CreateCondition(URLMatcherCondition::PATH_EQUALS,
+      kEndOfDomain + str + kEndOfPath);
+}
+
+URLMatcherCondition URLMatcherConditionFactory::CreateQueryPrefixCondition(
+    const std::string& prefix) {
+  return CreateCondition(URLMatcherCondition::QUERY_PREFIX,
+      kEndOfPath + prefix);
+}
+
+URLMatcherCondition URLMatcherConditionFactory::CreateQuerySuffixCondition(
+    const std::string& suffix) {
+  return CreateCondition(URLMatcherCondition::QUERY_SUFFIX, suffix + kEndOfURL);
+}
+
+URLMatcherCondition URLMatcherConditionFactory::CreateQueryContainsCondition(
+    const std::string& str) {
+  return CreateCondition(URLMatcherCondition::QUERY_CONTAINS, str);
+}
+
+URLMatcherCondition URLMatcherConditionFactory::CreateQueryEqualsCondition(
+    const std::string& str) {
+  return CreateCondition(URLMatcherCondition::QUERY_EQUALS,
+      kEndOfPath + str + kEndOfURL);
+}
+
+URLMatcherCondition
+    URLMatcherConditionFactory::CreateHostSuffixPathPrefixCondition(
+    const std::string& host_suffix,
+    const std::string& path_prefix) {
+  return CreateCondition(URLMatcherCondition::HOST_SUFFIX_PATH_PREFIX,
+      host_suffix + kEndOfDomain + path_prefix);
+}
+
+std::string URLMatcherConditionFactory::CanonicalizeURLForFullSearches(
+    const GURL& url) {
+  return kBeginningOfURL + CanonicalizeHostname(url.host()) + url.path() +
+      (url.has_query() ? "?" + url.query() : "") + kEndOfURL;
+}
+
+URLMatcherCondition URLMatcherConditionFactory::CreateURLPrefixCondition(
+    const std::string& prefix) {
+  return CreateCondition(URLMatcherCondition::URL_PREFIX,
+      kBeginningOfURL + CanonicalizeHostname(prefix));
+}
+
+URLMatcherCondition URLMatcherConditionFactory::CreateURLSuffixCondition(
+    const std::string& suffix) {
+  return CreateCondition(URLMatcherCondition::URL_SUFFIX, suffix + kEndOfURL);
+}
+
+URLMatcherCondition URLMatcherConditionFactory::CreateURLContainsCondition(
+    const std::string& str) {
+  return CreateCondition(URLMatcherCondition::URL_CONTAINS, str);
+}
+
+URLMatcherCondition URLMatcherConditionFactory::CreateURLEqualsCondition(
+    const std::string& str) {
+  return CreateCondition(URLMatcherCondition::QUERY_EQUALS,
+      kBeginningOfURL + CanonicalizeHostname(str) + kEndOfURL);
+}
+
+void URLMatcherConditionFactory::ForgetUnusedPatterns(
+      const std::set<SubstringPattern::ID>& used_patterns) {
+  PatternSingletons::iterator i = pattern_singletons_.begin();
+  while (i != pattern_singletons_.end()) {
+    if (used_patterns.find((*i)->id()) != used_patterns.end())
+      ++i;
+    else
+      pattern_singletons_.erase(i++);
+  }
+}
+
+URLMatcherCondition URLMatcherConditionFactory::CreateCondition(
+    URLMatcherCondition::Criterion criterion,
+    const std::string& pattern) {
+  SubstringPattern search_pattern(pattern, 0);
+  PatternSingletons::const_iterator iter =
+      pattern_singletons_.find(&search_pattern);
+  if (iter != pattern_singletons_.end()) {
+    return URLMatcherCondition(criterion, *iter);
+  } else {
+    SubstringPattern* new_pattern =
+        new SubstringPattern(pattern, id_counter_++);
+    pattern_singletons_.insert(new_pattern);
+    return URLMatcherCondition(criterion, new_pattern);
+  }
+}
+
+std::string URLMatcherConditionFactory::CanonicalizeHostname(
+    const std::string& hostname) const {
+  if (!hostname.empty() && hostname[0] == '.')
+    return hostname;
+  else
+    return "." + hostname;
+}
+
+bool URLMatcherConditionFactory::SubstringPatternPointerCompare::operator()(
+    SubstringPattern* lhs,
+    SubstringPattern* rhs) const {
+  if (lhs == NULL && rhs != NULL) return true;
+  if (lhs != NULL && rhs != NULL)
+    return lhs->pattern() < rhs->pattern();
+  // Either both are NULL or only rhs is NULL.
+  return false;
+}
+
+//
+// URLMatcherConditionSet
+//
+
+URLMatcherConditionSet::URLMatcherConditionSet() : id_(-1) {}
+
+URLMatcherConditionSet::~URLMatcherConditionSet() {}
+
+URLMatcherConditionSet::URLMatcherConditionSet(
+    ID id,
+    const Conditions& conditions)
+    : id_(id),
+      conditions_(conditions) {}
+
+URLMatcherConditionSet::URLMatcherConditionSet(
+    const URLMatcherConditionSet& rhs)
+    : id_(rhs.id_), conditions_(rhs.conditions_) {}
+
+URLMatcherConditionSet& URLMatcherConditionSet::operator=(
+    const URLMatcherConditionSet& rhs) {
+  id_ = rhs.id_;
+  conditions_ = rhs.conditions_;
+  return *this;
+}
+
+bool URLMatcherConditionSet::IsMatch(
+    const std::set<SubstringPattern::ID>& matching_substring_patterns,
+    const GURL& url) const {
+  for (Conditions::const_iterator i = conditions_.begin();
+      i != conditions_.end(); ++i) {
+    if (!i->IsMatch(matching_substring_patterns, url))
+      return false;
+  }
+  return true;
+}
+
+
+//
+// URLMatcher
+//
+
+URLMatcher::URLMatcher() {}
+
+URLMatcher::~URLMatcher() {}
+
+void URLMatcher::AddConditionSets(
+    const std::vector<URLMatcherConditionSet>& condition_sets) {
+  for (std::vector<URLMatcherConditionSet>::const_iterator i =
+      condition_sets.begin(); i != condition_sets.end(); ++i) {
+    DCHECK(url_matcher_condition_sets_.find(i->id()) ==
+          url_matcher_condition_sets_.end());
+    url_matcher_condition_sets_[i->id()] = *i;
+  }
+  UpdateInternalDatastructures();
+}
+
+void URLMatcher::RemoveConditionSets(
+    const std::vector<URLMatcherConditionSet::ID>& condition_set_ids) {
+  for (std::vector<URLMatcherConditionSet::ID>::const_iterator i =
+      condition_set_ids.begin(); i != condition_set_ids.end(); ++i) {
+    DCHECK(url_matcher_condition_sets_.find(*i) !=
+        url_matcher_condition_sets_.end());
+    url_matcher_condition_sets_.erase(*i);
+  }
+  UpdateInternalDatastructures();
+}
+
+std::set<URLMatcherConditionSet::ID> URLMatcher::MatchURL(const GURL& url) {
+  // Find all IDs of SubstringPatterns that match |url|.
+  // See URLMatcherConditionFactory for the canonicalization of URLs and the
+  // distinction between full url searches and url component searches.
+  std::set<SubstringPattern::ID> matches;
+  full_url_matcher_.Match(
+      condition_factory_.CanonicalizeURLForFullSearches(url), &matches);
+  url_component_matcher_.Match(
+      condition_factory_.CanonicalizeURLForComponentSearches(url), &matches);
+
+  // Calculate all URLMatcherConditionSets for which all URLMatcherConditions
+  // were fulfilled.
+  std::set<URLMatcherConditionSet::ID> result;
+  for (std::set<SubstringPattern::ID>::const_iterator i = matches.begin();
+      i != matches.end(); ++i) {
+    // For each URLMatcherConditionSet there is exactly one condition
+    // registered in substring_match_triggers_. This means that the following
+    // logic tests each URLMatcherConditionSet exactly once if it can be
+    // completely fulfilled.
+    std::set<URLMatcherConditionSet::ID>& condition_sets =
+        substring_match_triggers_[*i];
+    for (std::set<URLMatcherConditionSet::ID>::const_iterator j =
+        condition_sets.begin(); j != condition_sets.end(); ++j) {
+      if (url_matcher_condition_sets_[*j].IsMatch(matches, url))
+        result.insert(*j);
+    }
+  }
+
+  return result;
+}
+
+void URLMatcher::UpdateSubstringSetMatcher(bool full_url_conditions) {
+  // The purpose of |full_url_conditions| is just that we need to execute
+  // the same logic once for Full URL searches and once for URL Component
+  // searches (see URLMatcherConditionFactory).
+
+  // Determine which patterns need to be registered when this function
+  // terminates.
+  std::set<const SubstringPattern*> new_patterns;
+  for (URLMatcherConditionSets::const_iterator condition_set_iter =
+      url_matcher_condition_sets_.begin();
+      condition_set_iter != url_matcher_condition_sets_.end();
+      ++condition_set_iter) {
+    const URLMatcherConditionSet::Conditions& conditions =
+        condition_set_iter->second.conditions();
+    for (URLMatcherConditionSet::Conditions::const_iterator condition_iter =
+        conditions.begin(); condition_iter != conditions.end();
+        ++condition_iter) {
+      // If we are called to process Full URL searches, ignore all others,
+      // and vice versa.
+      if (full_url_conditions == condition_iter->IsFullURLCondition())
+        new_patterns.insert(condition_iter->substring_pattern());
+    }
+  }
+
+  // This is the set of patterns that were registered before this function
+  // is called.
+  std::set<const SubstringPattern*>& registered_patterns =
+      full_url_conditions ? registered_full_url_patterns_
+                          : registered_url_component_patterns_;
+
+  // Add all patterns that are in new_patterns but not in registered_patterns.
+  std::vector<const SubstringPattern*> patterns_to_register;
+  std::set_difference(
+      new_patterns.begin(), new_patterns.end(),
+      registered_patterns.begin(), registered_patterns.end(),
+      std::back_inserter(patterns_to_register));
+
+  // Remove all patterns that are in registered_patterns but not in
+  // new_patterns.
+  std::vector<const SubstringPattern*> patterns_to_unregister;
+  std::set_difference(
+      registered_patterns.begin(), registered_patterns.end(),
+      new_patterns.begin(), new_patterns.end(),
+      std::back_inserter(patterns_to_unregister));
+
+  // Update the SubstringSetMatcher.
+  SubstringSetMatcher& url_matcher =
+      full_url_conditions ? full_url_matcher_ : url_component_matcher_;
+  url_matcher.RegisterAndUnregisterPatterns(patterns_to_register,
+                                            patterns_to_unregister);
+
+  // Update the set of registered_patterns for the next time this function
+  // is being called.
+  registered_patterns.swap(new_patterns);
+}
+
+void URLMatcher::UpdateTriggers() {
+  // Count substring pattern frequencies.
+  std::map<SubstringPattern::ID, size_t> substring_pattern_frequencies;
+  for (URLMatcherConditionSets::const_iterator condition_set_iter =
+      url_matcher_condition_sets_.begin();
+      condition_set_iter != url_matcher_condition_sets_.end();
+      ++condition_set_iter) {
+    const URLMatcherConditionSet::Conditions& conditions =
+        condition_set_iter->second.conditions();
+    for (URLMatcherConditionSet::Conditions::const_iterator condition_iter =
+        conditions.begin(); condition_iter != conditions.end();
+        ++condition_iter) {
+      const SubstringPattern* pattern = condition_iter->substring_pattern();
+      substring_pattern_frequencies[pattern->id()]++;
+    }
+  }
+
+  // Update trigger conditions: Determine for each URLMatcherConditionSet which
+  // URLMatcherCondition contains a SubstringPattern that occurs least
+  // frequently in this URLMatcher. We assume that this condition is very
+  // specific and occurs rarely in URLs. If a match occurs for this
+  // URLMatcherCondition, we want to test all other URLMatcherCondition in the
+  // respective URLMatcherConditionSet as well to see whether the entire
+  // URLMatcherConditionSet is considered matching.
+  substring_match_triggers_.clear();
+  for (URLMatcherConditionSets::const_iterator condition_set_iter =
+      url_matcher_condition_sets_.begin();
+      condition_set_iter != url_matcher_condition_sets_.end();
+      ++condition_set_iter) {
+    const URLMatcherConditionSet::Conditions& conditions =
+        condition_set_iter->second.conditions();
+    if (conditions.empty())
+      continue;
+    URLMatcherConditionSet::Conditions::const_iterator condition_iter =
+        conditions.begin();
+    SubstringPattern::ID trigger = condition_iter->substring_pattern()->id();
+    // We skip the first element in the following loop.
+    ++condition_iter;
+    for (; condition_iter != conditions.end(); ++condition_iter) {
+      SubstringPattern::ID current_id =
+          condition_iter->substring_pattern()->id();
+      if (substring_pattern_frequencies[trigger] >
+          substring_pattern_frequencies[current_id]) {
+        trigger = current_id;
+      }
+    }
+    substring_match_triggers_[trigger].insert(condition_set_iter->second.id());
+  }
+}
+
+void URLMatcher::UpdateConditionFactory() {
+  std::set<SubstringPattern::ID> used_patterns;
+  for (URLMatcherConditionSets::const_iterator condition_set_iter =
+      url_matcher_condition_sets_.begin();
+      condition_set_iter != url_matcher_condition_sets_.end();
+      ++condition_set_iter) {
+    const URLMatcherConditionSet::Conditions& conditions =
+        condition_set_iter->second.conditions();
+    for (URLMatcherConditionSet::Conditions::const_iterator condition_iter =
+        conditions.begin(); condition_iter != conditions.end();
+        ++condition_iter) {
+      used_patterns.insert(condition_iter->substring_pattern()->id());
+    }
+  }
+  condition_factory_.ForgetUnusedPatterns(used_patterns);
+}
+
+void URLMatcher::UpdateInternalDatastructures() {
+  UpdateSubstringSetMatcher(false);
+  UpdateSubstringSetMatcher(true);
+  UpdateTriggers();
+  UpdateConditionFactory();
+}
+
+}  // namespace extensions