Include RE2 library

third_party/re2/re2/prog.h

+// Copyright 2007 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.
+
+// Compiled representation of regular expressions.
+// See regexp.h for the Regexp class, which represents a regular
+// expression symbolically.
+
+#ifndef RE2_PROG_H__
+#define RE2_PROG_H__
+
+#include "util/util.h"
+#include "re2/re2.h"
+
+namespace re2 {
+
+// Simple fixed-size bitmap.
+template<int Bits>
+class Bitmap {
+ public:
+  Bitmap() { Reset(); }
+  int Size() { return Bits; }
+
+  void Reset() {
+    for (int i = 0; i < Words; i++)
+      w_[i] = 0;
+  }
+  bool Get(int k) const {
+    return w_[k >> WordLog] & (1<<(k & 31));
+  }
+  void Set(int k) {
+    w_[k >> WordLog] |= 1<<(k & 31);
+  }
+  void Clear(int k) {
+    w_[k >> WordLog] &= ~(1<<(k & 31));
+  }
+  uint32 Word(int i) const {
+    return w_[i];
+  }
+
+ private:
+  static const int WordLog = 5;
+  static const int Words = (Bits+31)/32;
+  uint32 w_[Words];
+  DISALLOW_EVIL_CONSTRUCTORS(Bitmap);
+};
+
+
+// Opcodes for Inst
+enum InstOp {
+  kInstAlt = 0,      // choose between out_ and out1_
+  kInstAltMatch,     // Alt: out_ is [00-FF] and back, out1_ is match; or vice versa.
+  kInstByteRange,    // next (possible case-folded) byte must be in [lo_, hi_]
+  kInstCapture,      // capturing parenthesis number cap_
+  kInstEmptyWidth,   // empty-width special (^ $ ...); bit(s) set in empty_
+  kInstMatch,        // found a match!
+  kInstNop,          // no-op; occasionally unavoidable
+  kInstFail,         // never match; occasionally unavoidable
+};
+
+// Bit flags for empty-width specials
+enum EmptyOp {
+  kEmptyBeginLine        = 1<<0,      // ^ - beginning of line
+  kEmptyEndLine          = 1<<1,      // $ - end of line
+  kEmptyBeginText        = 1<<2,      // \A - beginning of text
+  kEmptyEndText          = 1<<3,      // \z - end of text
+  kEmptyWordBoundary     = 1<<4,      // \b - word boundary
+  kEmptyNonWordBoundary  = 1<<5,      // \B - not \b
+  kEmptyAllFlags         = (1<<6)-1,
+};
+
+class Regexp;
+
+class DFA;
+struct OneState;
+
+// Compiled form of regexp program.
+class Prog {
+ public:
+  Prog();
+  ~Prog();
+
+  // Single instruction in regexp program.
+  class Inst {
+   public:
+    Inst() : out_opcode_(0), out1_(0) { }
+
+    // Constructors per opcode
+    void InitAlt(uint32 out, uint32 out1);
+    void InitByteRange(int lo, int hi, int foldcase, uint32 out);
+    void InitCapture(int cap, uint32 out);
+    void InitEmptyWidth(EmptyOp empty, uint32 out);
+    void InitMatch(int id);
+    void InitNop(uint32 out);
+    void InitFail();
+
+    // Getters
+    int id(Prog* p) { return this - p->inst_; }
+    InstOp opcode() { return static_cast<InstOp>(out_opcode_&7); }
+    int out()     { return out_opcode_>>3; }
+    int out1()    { DCHECK(opcode() == kInstAlt || opcode() == kInstAltMatch); return out1_; }
+    int cap()       { DCHECK_EQ(opcode(), kInstCapture); return cap_; }
+    int lo()        { DCHECK_EQ(opcode(), kInstByteRange); return lo_; }
+    int hi()        { DCHECK_EQ(opcode(), kInstByteRange); return hi_; }
+    int foldcase()  { DCHECK_EQ(opcode(), kInstByteRange); return foldcase_; }
+    int match_id()  { DCHECK_EQ(opcode(), kInstMatch); return match_id_; }
+    EmptyOp empty() { DCHECK_EQ(opcode(), kInstEmptyWidth); return empty_; }
+    bool greedy(Prog *p) {
+      DCHECK_EQ(opcode(), kInstAltMatch);
+      return p->inst(out())->opcode() == kInstByteRange;
+    }
+
+    // Does this inst (an kInstByteRange) match c?
+    inline bool Matches(int c) {
+      DCHECK_EQ(opcode(), kInstByteRange);
+      if (foldcase_ && 'A' <= c && c <= 'Z')
+        c += 'a' - 'A';
+      return lo_ <= c && c <= hi_;
+    }
+
+    // Returns string representation for debugging.
+    string Dump();
+
+    // Maximum instruction id.
+    // (Must fit in out_opcode_, and PatchList steals another bit.)
+    static const int kMaxInst = (1<<28) - 1;
+
+   private:
+    void set_opcode(InstOp opcode) {
+      out_opcode_ = (out()<<3) | opcode;
+    }
+
+    void set_out(int out) {
+      out_opcode_ = (out<<3) | opcode();
+    }
+
+    void set_out_opcode(int out, InstOp opcode) {
+      out_opcode_ = (out<<3) | opcode;
+    }
+
+    uint32 out_opcode_;  // 29 bits of out, 3 (low) bits opcode
+    union {              // additional instruction arguments:
+      uint32 out1_;      // opcode == kInstAlt
+                         //   alternate next instruction
+
+      int32 cap_;        // opcode == kInstCapture
+                         //   Index of capture register (holds text
+                         //   position recorded by capturing parentheses).
+                         //   For \n (the submatch for the nth parentheses),
+                         //   the left parenthesis captures into register 2*n
+                         //   and the right one captures into register 2*n+1.
+
+      int32 match_id_;   // opcode == kInstMatch
+                         //   Match ID to identify this match (for re2::Set).
+
+      struct {           // opcode == kInstByteRange
+        uint8 lo_;       //   byte range is lo_-hi_ inclusive
+        uint8 hi_;       //
+        uint8 foldcase_; //   convert A-Z to a-z before checking range.
+      };
+
+      EmptyOp empty_;    // opcode == kInstEmptyWidth
+                         //   empty_ is bitwise OR of kEmpty* flags above.
+    };
+
+    friend class Compiler;
+    friend struct PatchList;
+    friend class Prog;
+
+    DISALLOW_EVIL_CONSTRUCTORS(Inst);
+  };
+
+  // Whether to anchor the search.
+  enum Anchor {
+    kUnanchored,  // match anywhere
+    kAnchored,    // match only starting at beginning of text
+  };
+
+  // Kind of match to look for (for anchor != kFullMatch)
+  //
+  // kLongestMatch mode finds the overall longest
+  // match but still makes its submatch choices the way
+  // Perl would, not in the way prescribed by POSIX.
+  // The POSIX rules are much more expensive to implement,
+  // and no one has needed them.
+  //
+  // kFullMatch is not strictly necessary -- we could use
+  // kLongestMatch and then check the length of the match -- but
+  // the matching code can run faster if it knows to consider only
+  // full matches.
+  enum MatchKind {
+    kFirstMatch,     // like Perl, PCRE
+    kLongestMatch,   // like egrep or POSIX
+    kFullMatch,      // match only entire text; implies anchor==kAnchored
+    kManyMatch       // for SearchDFA, records set of matches
+  };
+
+  Inst *inst(int id) { return &inst_[id]; }
+  int start() { return start_; }
+  int start_unanchored() { return start_unanchored_; }
+  void set_start(int start) { start_ = start; }
+  void set_start_unanchored(int start) { start_unanchored_ = start; }
+  int64 size() { return size_; }
+  bool reversed() { return reversed_; }
+  void set_reversed(bool reversed) { reversed_ = reversed; }
+  int64 byte_inst_count() { return byte_inst_count_; }
+  const Bitmap<256>& byterange() { return byterange_; }
+  void set_dfa_mem(int64 dfa_mem) { dfa_mem_ = dfa_mem; }
+  int64 dfa_mem() { return dfa_mem_; }
+  int flags() { return flags_; }
+  void set_flags(int flags) { flags_ = flags; }
+  bool anchor_start() { return anchor_start_; }
+  void set_anchor_start(bool b) { anchor_start_ = b; }
+  bool anchor_end() { return anchor_end_; }
+  void set_anchor_end(bool b) { anchor_end_ = b; }
+  int bytemap_range() { return bytemap_range_; }
+  const uint8* bytemap() { return bytemap_; }
+
+  // Returns string representation of program for debugging.
+  string Dump();
+  string DumpUnanchored();
+
+  // Record that at some point in the prog, the bytes in the range
+  // lo-hi (inclusive) are treated as different from bytes outside the range.
+  // Tracking this lets the DFA collapse commonly-treated byte ranges
+  // when recording state pointers, greatly reducing its memory footprint.
+  void MarkByteRange(int lo, int hi);
+
+  // Returns the set of kEmpty flags that are in effect at
+  // position p within context.
+  static uint32 EmptyFlags(const StringPiece& context, const char* p);
+
+  // Returns whether byte c is a word character: ASCII only.
+  // Used by the implementation of \b and \B.
+  // This is not right for Unicode, but:
+  //   - it's hard to get right in a byte-at-a-time matching world
+  //     (the DFA has only one-byte lookahead).
+  //   - even if the lookahead were possible, the Progs would be huge.
+  // This crude approximation is the same one PCRE uses.
+  static bool IsWordChar(uint8 c) {
+    return ('A' <= c && c <= 'Z') ||
+           ('a' <= c && c <= 'z') ||
+           ('0' <= c && c <= '9') ||
+           c == '_';
+  }
+
+  // Execution engines.  They all search for the regexp (run the prog)
+  // in text, which is in the larger context (used for ^ $ \b etc).
+  // Anchor and kind control the kind of search.
+  // Returns true if match found, false if not.
+  // If match found, fills match[0..nmatch-1] with submatch info.
+  // match[0] is overall match, match[1] is first set of parens, etc.
+  // If a particular submatch is not matched during the regexp match,
+  // it is set to NULL.
+  //
+  // Matching text == StringPiece(NULL, 0) is treated as any other empty
+  // string, but note that on return, it will not be possible to distinguish
+  // submatches that matched that empty string from submatches that didn't
+  // match anything.  Either way, match[i] == NULL.
+
+  // Search using NFA: can find submatches but kind of slow.
+  bool SearchNFA(const StringPiece& text, const StringPiece& context,
+                 Anchor anchor, MatchKind kind,
+                 StringPiece* match, int nmatch);
+
+  // Search using DFA: much faster than NFA but only finds
+  // end of match and can use a lot more memory.
+  // Returns whether a match was found.
+  // If the DFA runs out of memory, sets *failed to true and returns false.
+  // If matches != NULL and kind == kManyMatch and there is a match,
+  // SearchDFA fills matches with the match IDs of the final matching state.
+  bool SearchDFA(const StringPiece& text, const StringPiece& context,
+                 Anchor anchor, MatchKind kind,
+                 StringPiece* match0, bool* failed,
+                 vector<int>* matches);
+
+  // Build the entire DFA for the given match kind.  FOR TESTING ONLY.
+  // Usually the DFA is built out incrementally, as needed, which
+  // avoids lots of unnecessary work.  This function is useful only
+  // for testing purposes.  Returns number of states.
+  int BuildEntireDFA(MatchKind kind);
+
+  // Compute byte map.
+  void ComputeByteMap();
+
+  // Run peep-hole optimizer on program.
+  void Optimize();
+
+  // One-pass NFA: only correct if IsOnePass() is true,
+  // but much faster than NFA (competitive with PCRE)
+  // for those expressions.
+  bool IsOnePass();
+  bool SearchOnePass(const StringPiece& text, const StringPiece& context,
+                     Anchor anchor, MatchKind kind,
+                     StringPiece* match, int nmatch);
+
+  // Bit-state backtracking.  Fast on small cases but uses memory
+  // proportional to the product of the program size and the text size.
+  bool SearchBitState(const StringPiece& text, const StringPiece& context,
+                      Anchor anchor, MatchKind kind,
+                      StringPiece* match, int nmatch);
+
+  static const int kMaxOnePassCapture = 5;  // $0 through $4
+
+  // Backtracking search: the gold standard against which the other
+  // implementations are checked.  FOR TESTING ONLY.
+  // It allocates a ton of memory to avoid running forever.
+  // It is also recursive, so can't use in production (will overflow stacks).
+  // The name "Unsafe" here is supposed to be a flag that
+  // you should not be using this function.
+  bool UnsafeSearchBacktrack(const StringPiece& text,
+                             const StringPiece& context,
+                             Anchor anchor, MatchKind kind,
+                             StringPiece* match, int nmatch);
+
+  // Computes range for any strings matching regexp. The min and max can in
+  // some cases be arbitrarily precise, so the caller gets to specify the
+  // maximum desired length of string returned.
+  //
+  // Assuming PossibleMatchRange(&min, &max, N) returns successfully, any
+  // string s that is an anchored match for this regexp satisfies
+  //   min <= s && s <= max.
+  //
+  // Note that PossibleMatchRange() will only consider the first copy of an
+  // infinitely repeated element (i.e., any regexp element followed by a '*' or
+  // '+' operator). Regexps with "{N}" constructions are not affected, as those
+  // do not compile down to infinite repetitions.
+  //
+  // Returns true on success, false on error.
+  bool PossibleMatchRange(string* min, string* max, int maxlen);
+
+  // Compiles a collection of regexps to Prog.  Each regexp will have
+  // its own Match instruction recording the index in the vector.
+  static Prog* CompileSet(const RE2::Options& options, RE2::Anchor anchor,
+                          Regexp* re);
+
+ private:
+  friend class Compiler;
+
+  DFA* GetDFA(MatchKind kind);
+
+  bool anchor_start_;       // regexp has explicit start anchor
+  bool anchor_end_;         // regexp has explicit end anchor
+  bool reversed_;           // whether program runs backward over input
+  bool did_onepass_;        // has IsOnePass been called?
+
+  int start_;               // entry point for program
+  int start_unanchored_;    // unanchored entry point for program
+  int size_;                // number of instructions
+  int byte_inst_count_;     // number of kInstByteRange instructions
+  int bytemap_range_;       // bytemap_[x] < bytemap_range_
+  int flags_;               // regexp parse flags
+  int onepass_statesize_;   // byte size of each OneState* node
+
+  Inst* inst_;              // pointer to instruction array
+
+  Mutex dfa_mutex_;    // Protects dfa_first_, dfa_longest_
+  DFA* volatile dfa_first_;     // DFA cached for kFirstMatch
+  DFA* volatile dfa_longest_;   // DFA cached for kLongestMatch and kFullMatch
+  int64 dfa_mem_;      // Maximum memory for DFAs.
+  void (*delete_dfa_)(DFA* dfa);
+
+  Bitmap<256> byterange_;    // byterange.Get(x) true if x ends a
+                             // commonly-treated byte range.
+  uint8 bytemap_[256];       // map from input bytes to byte classes
+  uint8 *unbytemap_;         // bytemap_[unbytemap_[x]] == x
+
+  uint8* onepass_nodes_;     // data for OnePass nodes
+  OneState* onepass_start_;  // start node for OnePass program
+
+  DISALLOW_EVIL_CONSTRUCTORS(Prog);
+};
+
+}  // namespace re2
+
+#endif  // RE2_PROG_H__