Include RE2 library

third_party/re2/re2/prefilter.cc

Index: third_party/re2/re2/prefilter.cc
diff --git a/third_party/re2/re2/prefilter.cc b/third_party/re2/re2/prefilter.cc
new file mode 100644
index 0000000000000000000000000000000000000000..30e4c01bd1002a5abe349ef421c2feaf0ca54988
--- /dev/null
+++ b/third_party/re2/re2/prefilter.cc
@@ -0,0 +1,671 @@
+// Copyright 2009 The RE2 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 "util/util.h"
+#include "re2/prefilter.h"
+#include "re2/re2.h"
+#include "re2/unicode_casefold.h"
+#include "re2/walker-inl.h"
+
+namespace re2 {
+
+static const int Trace = false;
+
+typedef set<string>::iterator SSIter;
+typedef set<string>::const_iterator ConstSSIter;
+
+static int alloc_id = 100000;  // Used for debugging.
+// Initializes a Prefilter, allocating subs_ as necessary.
+Prefilter::Prefilter(Op op) {
+  op_ = op;
+  subs_ = NULL;
+  if (op_ == AND || op_ == OR)
+    subs_ = new vector<Prefilter*>;
+
+  alloc_id_ = alloc_id++;
+  VLOG(10) << "alloc_id: " << alloc_id_;
+}
+
+// Destroys a Prefilter.
+Prefilter::~Prefilter() {
+  VLOG(10) << "Deleted: " << alloc_id_;
+  if (subs_) {
+    for (int i = 0; i < subs_->size(); i++)
+      delete (*subs_)[i];
+    delete subs_;
+    subs_ = NULL;
+  }
+}
+
+// Simplify if the node is an empty Or or And.
+Prefilter* Prefilter::Simplify() {
+  if (op_ != AND && op_ != OR) {
+    return this;
+  }
+
+  // Nothing left in the AND/OR.
+  if (subs_->size() == 0) {
+    if (op_ == AND)
+      op_ = ALL;  // AND of nothing is true
+    else
+      op_ = NONE;  // OR of nothing is false
+
+    return this;
+  }
+
+  // Just one subnode: throw away wrapper.
+  if (subs_->size() == 1) {
+    Prefilter* a = (*subs_)[0];
+    subs_->clear();
+    delete this;
+    return a->Simplify();
+  }
+
+  return this;
+}
+
+// Combines two Prefilters together to create an "op" (AND or OR).
+// The passed Prefilters will be part of the returned Prefilter or deleted.
+// Does lots of work to avoid creating unnecessarily complicated structures.
+Prefilter* Prefilter::AndOr(Op op, Prefilter* a, Prefilter* b) {
+  // If a, b can be rewritten as op, do so.
+  a = a->Simplify();
+  b = b->Simplify();
+
+  // Canonicalize: a->op <= b->op.
+  if (a->op() > b->op()) {
+    Prefilter* t = a;
+    a = b;
+    b = t;
+  }
+
+  // Trivial cases.
+  //    ALL AND b = b
+  //    NONE OR b = b
+  //    ALL OR b   = ALL
+  //    NONE AND b = NONE
+  // Don't need to look at b, because of canonicalization above.
+  // ALL and NONE are smallest opcodes.
+  if (a->op() == ALL || a->op() == NONE) {
+    if ((a->op() == ALL && op == AND) ||
+        (a->op() == NONE && op == OR)) {
+      delete a;
+      return b;
+    } else {
+      delete b;
+      return a;
+    }
+  }
+
+  // If a and b match op, merge their contents.
+  if (a->op() == op && b->op() == op) {
+    for (int i = 0; i < b->subs()->size(); i++) {
+      Prefilter* bb = (*b->subs())[i];
+      a->subs()->push_back(bb);
+    }
+    b->subs()->clear();
+    delete b;
+    return a;
+  }
+
+  // If a already has the same op as the op that is under construction
+  // add in b (similarly if b already has the same op, add in a).
+  if (b->op() == op) {
+    Prefilter* t = a;
+    a = b;
+    b = t;
+  }
+  if (a->op() == op) {
+    a->subs()->push_back(b);
+    return a;
+  }
+
+  // Otherwise just return the op.
+  Prefilter* c = new Prefilter(op);
+  c->subs()->push_back(a);
+  c->subs()->push_back(b);
+  return c;
+}
+
+Prefilter* Prefilter::And(Prefilter* a, Prefilter* b) {
+  return AndOr(AND, a, b);
+}
+
+Prefilter* Prefilter::Or(Prefilter* a, Prefilter* b) {
+  return AndOr(OR, a, b);
+}
+
+static void SimplifyStringSet(set<string> *ss) {
+  // Now make sure that the strings aren't redundant.  For example, if
+  // we know "ab" is a required string, then it doesn't help at all to
+  // know that "abc" is also a required string, so delete "abc". This
+  // is because, when we are performing a string search to filter
+  // regexps, matching ab will already allow this regexp to be a
+  // candidate for match, so further matching abc is redundant.
+
+  for (SSIter i = ss->begin(); i != ss->end(); ++i) {
+    SSIter j = i;
+    ++j;
+    while (j != ss->end()) {
+      // Increment j early so that we can erase the element it points to.
+      SSIter old_j = j;
+      ++j;
+      if (old_j->find(*i) != string::npos)
+        ss->erase(old_j);
+    }
+  }
+}
+
+Prefilter* Prefilter::OrStrings(set<string>* ss) {
+  SimplifyStringSet(ss);
+  Prefilter* or_prefilter = NULL;
+  if (!ss->empty()) {
+    or_prefilter = new Prefilter(NONE);
+    for (SSIter i = ss->begin(); i != ss->end(); ++i)
+      or_prefilter = Or(or_prefilter, FromString(*i));
+  }
+  return or_prefilter;
+}
+
+static Rune ToLowerRune(Rune r) {
+  if (r < Runeself) {
+    if ('A' <= r && r <= 'Z')
+      r += 'a' - 'A';
+    return r;
+  }
+
+  CaseFold *f = LookupCaseFold(unicode_tolower, num_unicode_tolower, r);
+  if (f == NULL || r < f->lo)
+    return r;
+  return ApplyFold(f, r);
+}
+
+Prefilter* Prefilter::FromString(const string& str) {
+  Prefilter* m = new Prefilter(Prefilter::ATOM);
+  m->atom_ = str;
+  return m;
+}
+
+// Information about a regexp used during computation of Prefilter.
+// Can be thought of as information about the set of strings matching
+// the given regular expression.
+class Prefilter::Info {
+ public:
+  Info();
+  ~Info();
+
+  // More constructors.  They delete their Info* arguments.
+  static Info* Alt(Info* a, Info* b);
+  static Info* Concat(Info* a, Info* b);
+  static Info* And(Info* a, Info* b);
+  static Info* Star(Info* a);
+  static Info* Plus(Info* a);
+  static Info* Quest(Info* a);
+  static Info* EmptyString();
+  static Info* NoMatch();
+  static Info* AnyChar();
+  static Info* CClass(CharClass* cc);
+  static Info* Literal(Rune r);
+  static Info* AnyMatch();
+
+  // Format Info as a string.
+  string ToString();
+
+  // Caller takes ownership of the Prefilter.
+  Prefilter* TakeMatch();
+
+  set<string>& exact() { return exact_; }
+
+  bool is_exact() const { return is_exact_; }
+
+  class Walker;
+
+ private:
+  set<string> exact_;
+
+  // When is_exact_ is true, the strings that match
+  // are placed in exact_. When it is no longer an exact
+  // set of strings that match this RE, then is_exact_
+  // is false and the match_ contains the required match
+  // criteria.
+  bool is_exact_;
+
+  // Accumulated Prefilter query that any
+  // match for this regexp is guaranteed to match.
+  Prefilter* match_;
+};
+
+
+Prefilter::Info::Info()
+  : is_exact_(false),
+    match_(NULL) {
+}
+
+Prefilter::Info::~Info() {
+  delete match_;
+}
+
+Prefilter* Prefilter::Info::TakeMatch() {
+  if (is_exact_) {
+    match_ = Prefilter::OrStrings(&exact_);
+    is_exact_ = false;
+  }
+  Prefilter* m = match_;
+  match_ = NULL;
+  return m;
+}
+
+// Format a Info in string form.
+string Prefilter::Info::ToString() {
+  if (this == NULL) {
+    // Sometimes when iterating on children of a node,
+    // some children might have NULL Info. Adding
+    // the check here for NULL to take care of cases where
+    // the caller is not checking.
+    return "";
+  }
+
+  if (is_exact_) {
+    int n = 0;
+    string s;
+    for (set<string>::iterator i = exact_.begin(); i != exact_.end(); ++i) {
+      if (n++ > 0)
+        s += ",";
+      s += *i;
+    }
+    return s;
+  }
+
+  if (match_)
+    return match_->DebugString();
+
+  return "";
+}
+
+// Add the strings from src to dst.
+static void CopyIn(const set<string>& src, set<string>* dst) {
+  for (ConstSSIter i = src.begin(); i != src.end(); ++i)
+    dst->insert(*i);
+}
+
+// Add the cross-product of a and b to dst.
+// (For each string i in a and j in b, add i+j.)
+static void CrossProduct(const set<string>& a,
+                         const set<string>& b,
+                         set<string>* dst) {
+  for (ConstSSIter i = a.begin(); i != a.end(); ++i)
+    for (ConstSSIter j = b.begin(); j != b.end(); ++j)
+      dst->insert(*i + *j);
+}
+
+// Concats a and b. Requires that both are exact sets.
+// Forms an exact set that is a crossproduct of a and b.
+Prefilter::Info* Prefilter::Info::Concat(Info* a, Info* b) {
+  if (a == NULL)
+    return b;
+  DCHECK(a->is_exact_);
+  DCHECK(b && b->is_exact_);
+  Info *ab = new Info();
+
+  CrossProduct(a->exact_, b->exact_, &ab->exact_);
+  ab->is_exact_ = true;
+
+  delete a;
+  delete b;
+  return ab;
+}
+
+// Constructs an inexact Info for ab given a and b.
+// Used only when a or b is not exact or when the
+// exact cross product is likely to be too big.
+Prefilter::Info* Prefilter::Info::And(Info* a, Info* b) {
+  if (a == NULL)
+    return b;
+  if (b == NULL)
+    return a;
+
+  Info *ab = new Info();
+
+  ab->match_ = Prefilter::And(a->TakeMatch(), b->TakeMatch());
+  ab->is_exact_ = false;
+  delete a;
+  delete b;
+  return ab;
+}
+
+// Constructs Info for a|b given a and b.
+Prefilter::Info* Prefilter::Info::Alt(Info* a, Info* b) {
+  Info *ab = new Info();
+
+  if (a->is_exact_ && b->is_exact_) {
+    CopyIn(a->exact_, &ab->exact_);
+    CopyIn(b->exact_, &ab->exact_);
+    ab->is_exact_ = true;
+  } else {
+    // Either a or b has is_exact_ = false. If the other
+    // one has is_exact_ = true, we move it to match_ and
+    // then create a OR of a,b. The resulting Info has
+    // is_exact_ = false.
+    ab->match_ = Prefilter::Or(a->TakeMatch(), b->TakeMatch());
+    ab->is_exact_ = false;
+  }
+
+  delete a;
+  delete b;
+  return ab;
+}
+
+// Constructs Info for a? given a.
+Prefilter::Info* Prefilter::Info::Quest(Info *a) {
+  Info *ab = new Info();
+
+  ab->is_exact_ = false;
+  ab->match_ = new Prefilter(ALL);
+  delete a;
+  return ab;
+}
+
+// Constructs Info for a* given a.
+// Same as a? -- not much to do.
+Prefilter::Info* Prefilter::Info::Star(Info *a) {
+  return Quest(a);
+}
+
+// Constructs Info for a+ given a. If a was exact set, it isn't
+// anymore.
+Prefilter::Info* Prefilter::Info::Plus(Info *a) {
+  Info *ab = new Info();
+
+  ab->match_ = a->TakeMatch();
+  ab->is_exact_ = false;
+
+  delete a;
+  return ab;
+}
+
+static string RuneToString(Rune r) {
+  char buf[UTFmax];
+  int n = runetochar(buf, &r);
+  return string(buf, n);
+}
+
+// Constructs Info for literal rune.
+Prefilter::Info* Prefilter::Info::Literal(Rune r) {
+  Info* info = new Info();
+  info->exact_.insert(RuneToString(ToLowerRune(r)));
+  info->is_exact_ = true;
+  return info;
+}
+
+// Constructs Info for dot (any character).
+Prefilter::Info* Prefilter::Info::AnyChar() {
+  Prefilter::Info* info = new Prefilter::Info();
+  info->match_ = new Prefilter(ALL);
+  return info;
+}
+
+// Constructs Prefilter::Info for no possible match.
+Prefilter::Info* Prefilter::Info::NoMatch() {
+  Prefilter::Info* info = new Prefilter::Info();
+  info->match_ = new Prefilter(NONE);
+  return info;
+}
+
+// Constructs Prefilter::Info for any possible match.
+// This Prefilter::Info is valid for any regular expression,
+// since it makes no assertions whatsoever about the
+// strings being matched.
+Prefilter::Info* Prefilter::Info::AnyMatch() {
+  Prefilter::Info *info = new Prefilter::Info();
+  info->match_ = new Prefilter(ALL);
+  return info;
+}
+
+// Constructs Prefilter::Info for just the empty string.
+Prefilter::Info* Prefilter::Info::EmptyString() {
+  Prefilter::Info* info = new Prefilter::Info();
+  info->is_exact_ = true;
+  info->exact_.insert("");
+  return info;
+}
+
+// Constructs Prefilter::Info for a character class.
+typedef CharClass::iterator CCIter;
+Prefilter::Info* Prefilter::Info::CClass(CharClass *cc) {
+  if (Trace) {
+    VLOG(0) << "CharClassInfo:";
+    for (CCIter i = cc->begin(); i != cc->end(); ++i)
+      VLOG(0) << "  " << i->lo << "-" << i->hi;
+  }
+
+  // If the class is too large, it's okay to overestimate.
+  if (cc->size() > 10)
+    return AnyChar();
+
+  Prefilter::Info *a = new Prefilter::Info();
+  for (CCIter i = cc->begin(); i != cc->end(); ++i)
+    for (Rune r = i->lo; r <= i->hi; r++)
+      a->exact_.insert(RuneToString(ToLowerRune(r)));
+
+  a->is_exact_ = true;
+
+  if (Trace) {
+    VLOG(0) << " = " << a->ToString();
+  }
+
+  return a;
+}
+
+class Prefilter::Info::Walker : public Regexp::Walker<Prefilter::Info*> {
+ public:
+  Walker() {}
+
+  virtual Info* PostVisit(
+      Regexp* re, Info* parent_arg,
+      Info* pre_arg,
+      Info** child_args, int nchild_args);
+
+  virtual Info* ShortVisit(
+      Regexp* re,
+      Info* parent_arg);
+
+ private:
+  DISALLOW_EVIL_CONSTRUCTORS(Walker);
+};
+
+Prefilter::Info* Prefilter::BuildInfo(Regexp* re) {
+  if (Trace) {
+    LOG(INFO) << "BuildPrefilter::Info: " << re->ToString();
+  }
+  Prefilter::Info::Walker w;
+  Prefilter::Info* info = w.WalkExponential(re, NULL, 100000);
+
+  if (w.stopped_early()) {
+    delete info;
+    return NULL;
+  }
+
+  return info;
+}
+
+Prefilter::Info* Prefilter::Info::Walker::ShortVisit(
+    Regexp* re, Prefilter::Info* parent_arg) {
+  return AnyMatch();
+}
+
+// Constructs the Prefilter::Info for the given regular expression.
+// Assumes re is simplified.
+Prefilter::Info* Prefilter::Info::Walker::PostVisit(
+    Regexp* re, Prefilter::Info* parent_arg,
+    Prefilter::Info* pre_arg, Prefilter::Info** child_args,
+    int nchild_args) {
+  Prefilter::Info *info;
+  switch (re->op()) {
+    default:
+    case kRegexpRepeat:
+      LOG(DFATAL) << "Bad regexp op " << re->op();
+      info = EmptyString();
+      break;
+
+    case kRegexpNoMatch:
+      info = NoMatch();
+      break;
+
+    // These ops match the empty string:
+    case kRegexpEmptyMatch:      // anywhere
+    case kRegexpBeginLine:       // at beginning of line
+    case kRegexpEndLine:         // at end of line
+    case kRegexpBeginText:       // at beginning of text
+    case kRegexpEndText:         // at end of text
+    case kRegexpWordBoundary:    // at word boundary
+    case kRegexpNoWordBoundary:  // not at word boundary
+      info = EmptyString();
+      break;
+
+    case kRegexpLiteral:
+      info = Literal(re->rune());
+      break;
+
+    case kRegexpLiteralString:
+      if (re->nrunes() == 0) {
+        info = NoMatch();
+        break;
+      }
+      info = Literal(re->runes()[0]);
+      for (int i = 1; i < re->nrunes(); i++)
+        info = Concat(info, Literal(re->runes()[i]));
+      break;
+
+    case kRegexpConcat: {
+      // Accumulate in info.
+      // Exact is concat of recent contiguous exact nodes.
+      info = NULL;
+      Info* exact = NULL;
+      for (int i = 0; i < nchild_args; i++) {
+        Info* ci = child_args[i];  // child info
+        if (!ci->is_exact() ||
+            (exact && ci->exact().size() * exact->exact().size() > 16)) {
+          // Exact run is over.
+          info = And(info, exact);
+          exact = NULL;
+          // Add this child's info.
+          info = And(info, ci);
+        } else {
+          // Append to exact run.
+          exact = Concat(exact, ci);
+        }
+      }
+      info = And(info, exact);
+    }
+      break;
+
+    case kRegexpAlternate:
+      info = child_args[0];
+      for (int i = 1; i < nchild_args; i++)
+        info = Alt(info, child_args[i]);
+      VLOG(10) << "Alt: " << info->ToString();
+      break;
+
+    case kRegexpStar:
+      info = Star(child_args[0]);
+      break;
+
+    case kRegexpQuest:
+      info = Quest(child_args[0]);
+      break;
+
+    case kRegexpPlus:
+      info = Plus(child_args[0]);
+      break;
+
+    case kRegexpAnyChar:
+      // Claim nothing, except that it's not empty.
+      info = AnyChar();
+      break;
+
+    case kRegexpCharClass:
+      info = CClass(re->cc());
+      break;
+
+    case kRegexpCapture:
+      // These don't affect the set of matching strings.
+      info = child_args[0];
+      break;
+  }
+
+  if (Trace) {
+    VLOG(0) << "BuildInfo " << re->ToString()
+            << ": " << info->ToString();
+  }
+
+  return info;
+}
+
+
+Prefilter* Prefilter::FromRegexp(Regexp* re) {
+  if (re == NULL)
+    return NULL;
+
+  Regexp* simple = re->Simplify();
+  Prefilter::Info *info = BuildInfo(simple);
+
+  simple->Decref();
+  if (info == NULL)
+    return NULL;
+
+  Prefilter* m = info->TakeMatch();
+
+  delete info;
+  return m;
+}
+
+string Prefilter::DebugString() const {
+  if (this == NULL)
+    return "<nil>";
+
+  switch (op_) {
+    default:
+      LOG(DFATAL) << "Bad op in Prefilter::DebugString: " << op_;
+      return StringPrintf("op%d", op_);
+    case NONE:
+      return "*no-matches*";
+    case ATOM:
+      return atom_;
+    case ALL:
+      return "";
+    case AND: {
+      string s = "";
+      for (int i = 0; i < subs_->size(); i++) {
+        if (i > 0)
+          s += " ";
+        s += (*subs_)[i]->DebugString();
+      }
+      return s;
+    }
+    case OR: {
+      string s = "(";
+      for (int i = 0; i < subs_->size(); i++) {
+        if (i > 0)
+          s += "|";
+        s += (*subs_)[i]->DebugString();
+      }
+      s += ")";
+      return s;
+    }
+  }
+}
+
+Prefilter* Prefilter::FromRE2(const RE2* re2) {
+  if (re2 == NULL)
+    return NULL;
+
+  Regexp* regexp = re2->Regexp();
+  if (regexp == NULL)
+    return NULL;
+
+  return FromRegexp(regexp);
+}
+
+
+}  // namespace re2