tools/gn/pattern.cc

   1 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "tools/gn/pattern.h"
   6
   7 #include "tools/gn/value.h"
   8
   9 namespace {
  10
  11 void ParsePattern(const std::string& s, std::vector<Pattern::Subrange>* out) {
  12   // Set when the last subrange is a literal so we can just append when we
  13   // find another literal.
  14   Pattern::Subrange* last_literal = nullptr;
  15
  16   for (size_t i = 0; i < s.size(); i++) {
  17     if (s[i] == '*') {
  18       // Don't allow two **.
  19       if (out->size() == 0 ||
  20           (*out)[out->size() - 1].type != Pattern::Subrange::ANYTHING)
  21         out->push_back(Pattern::Subrange(Pattern::Subrange::ANYTHING));
  22       last_literal = nullptr;
  23     } else if (s[i] == '\\') {
  24       if (i < s.size() - 1 && s[i + 1] == 'b') {
  25         // "\b" means path boundary.
  26         i++;
  27         out->push_back(Pattern::Subrange(Pattern::Subrange::PATH_BOUNDARY));
  28         last_literal = nullptr;
  29       } else {
  30         // Backslash + anything else means that literal char.
  31         if (!last_literal) {
  32           out->push_back(Pattern::Subrange(Pattern::Subrange::LITERAL));
  33           last_literal = &(*out)[out->size() - 1];
  34         }
  35         if (i < s.size() - 1) {
  36           i++;
  37           last_literal->literal.push_back(s[i]);
  38         } else {
  39           // Single backslash at end, use literal backslash.
  40           last_literal->literal.push_back('\\');
  41         }
  42       }
  43     } else {
  44       if (!last_literal) {
  45         out->push_back(Pattern::Subrange(Pattern::Subrange::LITERAL));
  46         last_literal = &(*out)[out->size() - 1];
  47       }
  48       last_literal->literal.push_back(s[i]);
  49     }
  50   }
  51 }
  52
  53 }  // namespace
  54
  55 Pattern::Pattern(const std::string& s) {
  56   ParsePattern(s, &subranges_);
  57   is_suffix_ =
  58       (subranges_.size() == 2 &&
  59        subranges_[0].type == Subrange::ANYTHING &&
  60        subranges_[1].type == Subrange::LITERAL);
  61 }
  62
  63 Pattern::~Pattern() {
  64 }
  65
  66 bool Pattern::MatchesString(const std::string& s) const {
  67   // Empty pattern matches only empty string.
  68   if (subranges_.empty())
  69     return s.empty();
  70
  71   if (is_suffix_) {
  72     const std::string& suffix = subranges_[1].literal;
  73     if (suffix.size() > s.size())
  74       return false;  // Too short.
  75     return s.compare(s.size() - suffix.size(), suffix.size(), suffix) == 0;
  76   }
  77
  78   return RecursiveMatch(s, 0, 0, true);
  79 }
  80
  81 // We assume the number of ranges is small so recursive is always reasonable.
  82 // Could be optimized to only be recursive for *.
  83 bool Pattern::RecursiveMatch(const std::string& s,
  84                              size_t begin_char,
  85                              size_t subrange_index,
  86                              bool allow_implicit_path_boundary) const {
  87   if (subrange_index >= subranges_.size()) {
  88     // Hit the end of our subranges, the text should also be at the end for a
  89     // match.
  90     return begin_char == s.size();
  91   }
  92
  93   const Subrange& sr = subranges_[subrange_index];
  94   switch (sr.type) {
  95     case Subrange::LITERAL: {
  96       if (s.size() - begin_char < sr.literal.size())
  97         return false;  // Not enough room.
  98       if (s.compare(begin_char, sr.literal.size(), sr.literal) != 0)
  99         return false;  // Literal doesn't match.
 100
 101       // Recursively check the next one.
 102       return RecursiveMatch(s, begin_char + sr.literal.size(),
 103                             subrange_index + 1, true);
 104     }
 105
 106     case Subrange::PATH_BOUNDARY: {
 107       // When we can accept an implicit path boundary, we have to check both
 108       // a match of the literal and the implicit one.
 109       if (allow_implicit_path_boundary &&
 110           (begin_char == 0 || begin_char == s.size())) {
 111         // At implicit path boundary, see if the rest of the pattern matches.
 112         if (RecursiveMatch(s, begin_char, subrange_index + 1, false))
 113           return true;
 114       }
 115
 116       // Check for a literal "/".
 117       if (begin_char < s.size() && s[begin_char] == '/') {
 118         // At explicit boundary, see if the rest of the pattern matches.
 119         if (RecursiveMatch(s, begin_char + 1, subrange_index + 1, true))
 120           return true;
 121       }
 122       return false;
 123     }
 124
 125     case Subrange::ANYTHING: {
 126       if (subrange_index == subranges_.size() - 1)
 127         return true;  // * at the end, consider it matching.
 128
 129       size_t min_next_size = sr.MinSize();
 130
 131       // We don't care about exactly what matched as long as there was a match,
 132       // so we can do this front-to-back. If we needed the match, we would
 133       // normally want "*" to be greedy so would work backwards.
 134       for (size_t i = begin_char; i < s.size() - min_next_size; i++) {
 135         // Note: this could probably be faster by detecting the type of the
 136         // next match in advance and checking for a match in this loop rather
 137         // than doing a full recursive call for each character.
 138         if (RecursiveMatch(s, i, subrange_index + 1, true))
 139           return true;
 140       }
 141       return false;
 142     }
 143
 144     default:
 145       NOTREACHED();
 146   }
 147
 148   return false;
 149 }
 150
 151 PatternList::PatternList() {
 152 }
 153
 154 PatternList::~PatternList() {
 155 }
 156
 157 void PatternList::Append(const Pattern& pattern) {
 158   patterns_.push_back(pattern);
 159 }
 160
 161 void PatternList::SetFromValue(const Value& v, Err* err) {
 162   patterns_.clear();
 163
 164   if (v.type() != Value::LIST) {
 165     *err = Err(v.origin(), "This value must be a list.");
 166     return;
 167   }
 168
 169   const std::vector<Value>& list = v.list_value();
 170   for (const auto& elem : list) {
 171     if (!elem.VerifyTypeIs(Value::STRING, err))
 172       return;
 173     patterns_.push_back(Pattern(elem.string_value()));
 174   }
 175 }
 176
 177 bool PatternList::MatchesString(const std::string& s) const {
 178   for (const auto& pattern : patterns_) {
 179     if (pattern.MatchesString(s))
 180       return true;
 181   }
 182   return false;
 183 }
 184
 185 bool PatternList::MatchesValue(const Value& v) const {
 186   if (v.type() == Value::STRING)
 187     return MatchesString(v.string_value());
 188   return false;
 189 }