// 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.

#ifndef RE2_PROG_H_

#define RE2_PROG_H_

// Compiled representation of regular expressions.

// See regexp.h for the Regexp class, which represents a regular

// expression symbolically.

#include <stdint.h>

#include <cstring>

#include <functional>

#include <string>

#include <type_traits>

#include <vector>

#include "absl/base/call_once.h"

#include "absl/log/absl_check.h"

#include "absl/log/absl_log.h"

#include "absl/strings/string_view.h"

#include "re2/pod_array.h"

#include "re2/re2.h"

#include "re2/sparse_array.h"

#include "re2/sparse_set.h"

namespace re2 {

// 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

  kNumInst,

};

// 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 DFA;

class Regexp;

// Compiled form of regexp program.

class Prog {

 public:

  Prog();

  ~Prog();

  // Single instruction in regexp program.

  class Inst {

   public:

    // See the assertion below for why this is so.

    Inst() = default;

    // Copyable.

    Inst(const Inst&) = default;

    Inst& operator=(const Inst&) = default;

    // Constructors per opcode

    void InitAlt(uint32_t out, uint32_t out1);

    void InitByteRange(int lo, int hi, int foldcase, uint32_t out);

    void InitCapture(int cap, uint32_t out);

    void InitEmptyWidth(EmptyOp empty, uint32_t out);

    void InitMatch(int id);

    void InitNop(uint32_t out);

    void InitFail();

    // Getters

    int id(Prog* p) { return static_cast<int>(this - p->inst_.data()); }

    InstOp opcode() { return static_cast<InstOp>(out_opcode_ & 7); }

    int last() { return (out_opcode_ >> 3) & 1; }

    int out() { return out_opcode_ >> 4; }

    int out1() {

      ABSL_DCHECK(opcode() == kInstAlt || opcode() == kInstAltMatch);

      return out1_;

    }

    int cap() {

      ABSL_DCHECK_EQ(opcode(), kInstCapture);

      return cap_;

    }

    int lo() {

      ABSL_DCHECK_EQ(opcode(), kInstByteRange);

      return lo_;

    }

    int hi() {

      ABSL_DCHECK_EQ(opcode(), kInstByteRange);

      return hi_;

    }

    int foldcase() {

      ABSL_DCHECK_EQ(opcode(), kInstByteRange);

      return hint_foldcase_ & 1;

    }

    int hint() {

      ABSL_DCHECK_EQ(opcode(), kInstByteRange);

      return hint_foldcase_ >> 1;

    }

    int match_id() {

      ABSL_DCHECK_EQ(opcode(), kInstMatch);

      return match_id_;

    }

    EmptyOp empty() {

      ABSL_DCHECK_EQ(opcode(), kInstEmptyWidth);

      return empty_;

    }

    bool greedy(Prog* p) {

      ABSL_DCHECK_EQ(opcode(), kInstAltMatch);

      return p->inst(out())->opcode() == kInstByteRange ||

             (p->inst(out())->opcode() == kInstNop &&

              p->inst(p->inst(out())->out())->opcode() == kInstByteRange);

    }

    // Does this inst (an kInstByteRange) match c?

    inline bool Matches(int c) {

      ABSL_DCHECK_EQ(opcode(), kInstByteRange);

      if (foldcase() && 'A' <= c && c <= 'Z')

        c += 'a' - 'A';

      return lo_ <= c && c <= hi_;

    }

    // Returns string representation for debugging.

    std::string Dump();

    // Maximum instruction id.

    // (Must fit in out_opcode_. PatchList/last steal another bit.)

    static const int kMaxInst = (1<<28) - 1;

   private:

    void set_opcode(InstOp opcode) {

      out_opcode_ = (out()<<4) | (last()<<3) | opcode;

    }

    void set_last() {

      out_opcode_ = (out()<<4) | (1<<3) | opcode();

    }

    void set_out(int out) {

      out_opcode_ = (out<<4) | (last()<<3) | opcode();

    }

    void set_out_opcode(int out, InstOp opcode) {

      out_opcode_ = (out<<4) | (last()<<3) | opcode;

    }

    uint32_t out_opcode_;  // 28 bits: out, 1 bit: last, 3 (low) bits: opcode

    union {                // additional instruction arguments:

      uint32_t out1_;      // opcode == kInstAlt

                           //   alternate next instruction

      int32_t 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_t match_id_;   // opcode == kInstMatch

                           //   Match ID to identify this match (for re2::Set).

      struct {             // opcode == kInstByteRange

        uint8_t lo_;       //   byte range is lo_-hi_ inclusive

        uint8_t hi_;       //

        uint16_t hint_foldcase_;  // 15 bits: hint, 1 (low) bit: foldcase

                           //   hint to execution engines: the delta to the

                           //   next instruction (in the current list) worth

                           //   exploring iff this instruction matched; 0

                           //   means there are no remaining possibilities,

                           //   which is most likely for character classes.

                           //   foldcase: A-Z -> 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;

  };

  // Inst must be trivial so that we can freely clear it with memset(3).

  // Arrays of Inst are initialised by copying the initial elements with

  // memmove(3) and then clearing any remaining elements with memset(3).

  static_assert(std::is_trivial<Inst>::value, "Inst must be trivial");

  // 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_; }

  void set_start(int start) { start_ = start; }

  int start_unanchored() { return start_unanchored_; }

  void set_start_unanchored(int start) { start_unanchored_ = start; }

  int size() { return size_; }

  bool reversed() { return reversed_; }

  void set_reversed(bool reversed) { reversed_ = reversed; }

  int list_count() { return list_count_; }

  int inst_count(InstOp op) { return inst_count_[op]; }

  uint16_t* list_heads() { return list_heads_.data(); }

  size_t bit_state_text_max_size() { return bit_state_text_max_size_; }

  int64_t dfa_mem() { return dfa_mem_; }

  void set_dfa_mem(int64_t dfa_mem) { dfa_mem_ = dfa_mem; }

  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_t* bytemap() { return bytemap_; }

  bool can_prefix_accel() { return prefix_size_ != 0; }

  // Accelerates to the first likely occurrence of the prefix.

  // Returns a pointer to the first byte or NULL if not found.

  const void* PrefixAccel(const void* data, size_t size) {

    ABSL_DCHECK(can_prefix_accel());

    if (prefix_foldcase_) {

      return PrefixAccel_ShiftDFA(data, size);

    } else if (prefix_size_ != 1) {

      return PrefixAccel_FrontAndBack(data, size);

    } else {

      return memchr(data, prefix_front_, size);

    }

  }

  // Configures prefix accel using the analysis performed during compilation.

  void ConfigurePrefixAccel(const std::string& prefix, bool prefix_foldcase);

  // An implementation of prefix accel that uses prefix_dfa_ to perform

  // case-insensitive search.

  const void* PrefixAccel_ShiftDFA(const void* data, size_t size);

  // An implementation of prefix accel that looks for prefix_front_ and

  // prefix_back_ to return fewer false positives than memchr(3) alone.

  const void* PrefixAccel_FrontAndBack(const void* data, size_t size);

  // Returns string representation of program for debugging.

  std::string Dump();

  std::string DumpUnanchored();

  std::string DumpByteMap();

  // Returns the set of kEmpty flags that are in effect at

  // position p within context.

  static uint32_t EmptyFlags(absl::string_view 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_t 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 == absl::string_view() 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(absl::string_view text, absl::string_view context,

                 Anchor anchor, MatchKind kind, absl::string_view* 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(absl::string_view text, absl::string_view context,

                 Anchor anchor, MatchKind kind, absl::string_view* match0,

                 bool* failed, SparseSet* matches);

  // The callback issued after building each DFA state with BuildEntireDFA().

  // If next is null, then the memory budget has been exhausted and building

  // will halt. Otherwise, the state has been built and next points to an array

  // of bytemap_range()+1 slots holding the next states as per the bytemap and

  // kByteEndText. The number of the state is implied by the callback sequence:

  // the first callback is for state 0, the second callback is for state 1, ...

  // match indicates whether the state is a matching state.

  using DFAStateCallback = std::function<void(const int* next, bool match)>;

  // Build the entire DFA for the given match kind.

  // Usually the DFA is built out incrementally, as needed, which

  // avoids lots of unnecessary work.

  // If cb is not empty, it receives one callback per state built.

  // Returns the number of states built.

  // FOR TESTING OR EXPERIMENTAL PURPOSES ONLY.

  int BuildEntireDFA(MatchKind kind, const DFAStateCallback& cb);

  // Compute bytemap.

  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(absl::string_view text, absl::string_view context,

                     Anchor anchor, MatchKind kind, absl::string_view* match,

                     int nmatch);

  // Bit-state backtracking.  Fast on small cases but uses memory

  // proportional to the product of the list count and the text size.

  bool CanBitState() { return list_heads_.data() != NULL; }

  bool SearchBitState(absl::string_view text, absl::string_view context,

                      Anchor anchor, MatchKind kind, absl::string_view* 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(absl::string_view text, absl::string_view context,

                             Anchor anchor, MatchKind kind,

                             absl::string_view* 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(std::string* min, std::string* max, int maxlen);

  // Outputs the program fanout into the given sparse array.

  void Fanout(SparseArray<int>* fanout);

  // Compiles a collection of regexps to Prog.  Each regexp will have

  // its own Match instruction recording the index in the output vector.

  static Prog* CompileSet(Regexp* re, RE2::Anchor anchor, int64_t max_mem);

  // Flattens the Prog from "tree" form to "list" form. This is an in-place

  // operation in the sense that the old instructions are lost.

  void Flatten();

  // Walks the Prog; the "successor roots" or predecessors of the reachable

  // instructions are marked in rootmap or predmap/predvec, respectively.

  // reachable and stk are preallocated scratch structures.

  void MarkSuccessors(SparseArray<int>* rootmap,

                      SparseArray<int>* predmap,

                      std::vector<std::vector<int>>* predvec,

                      SparseSet* reachable, std::vector<int>* stk);

  // Walks the Prog from the given "root" instruction; the "dominator root"

  // of the reachable instructions (if such exists) is marked in rootmap.

  // reachable and stk are preallocated scratch structures.

  void MarkDominator(int root, SparseArray<int>* rootmap,

                     SparseArray<int>* predmap,

                     std::vector<std::vector<int>>* predvec,

                     SparseSet* reachable, std::vector<int>* stk);

  // Walks the Prog from the given "root" instruction; the reachable

  // instructions are emitted in "list" form and appended to flat.

  // reachable and stk are preallocated scratch structures.

  void EmitList(int root, SparseArray<int>* rootmap,

                std::vector<Inst>* flat,

                SparseSet* reachable, std::vector<int>* stk);

  // Computes hints for ByteRange instructions in [begin, end).

  void ComputeHints(std::vector<Inst>* flat, int begin, int end);

  // Controls whether the DFA should bail out early if the NFA would be faster.

  // FOR TESTING ONLY.

  static void TESTING_ONLY_set_dfa_should_bail_when_slow(bool b);

 private:

  friend class Compiler;

  DFA* GetDFA(MatchKind kind);

  void DeleteDFA(DFA* dfa);

  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_flatten_;        // has Flatten been called?

  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 bytemap_range_;       // bytemap_[x] < bytemap_range_

  bool prefix_foldcase_;    // whether prefix is case-insensitive

  size_t prefix_size_;      // size of prefix (0 if no prefix)

  union {

    uint64_t* prefix_dfa_;  // "Shift DFA" for prefix

    struct {

      int prefix_front_;    // first byte of prefix

      int prefix_back_;     // last byte of prefix

    };

  };

  int list_count_;                  // count of lists (see above)

  int inst_count_[kNumInst];        // count of instructions by opcode

  PODArray<uint16_t> list_heads_;   // sparse array enumerating list heads

                                    // not populated if size_ is overly large

  size_t bit_state_text_max_size_;  // upper bound (inclusive) on text.size()

  PODArray<Inst> inst_;              // pointer to instruction array

  PODArray<uint8_t> onepass_nodes_;  // data for OnePass nodes

  int64_t dfa_mem_;         // Maximum memory for DFAs.

  DFA* dfa_first_;          // DFA cached for kFirstMatch/kManyMatch

  DFA* dfa_longest_;        // DFA cached for kLongestMatch/kFullMatch

  uint8_t bytemap_[256];    // map from input bytes to byte classes

  absl::once_flag dfa_first_once_;

  absl::once_flag dfa_longest_once_;

  Prog(const Prog&) = delete;

  Prog& operator=(const Prog&) = delete;

};

// std::string_view in MSVC has iterators that aren't just pointers and

// that don't allow comparisons between different objects - not even if

// those objects are views into the same string! Thus, we provide these

// conversion functions for convenience.

static inline const char* BeginPtr(absl::string_view s) {

  return s.data();

}

Unexecuted instantiation: re2.cc:re2::BeginPtr(std::__1::basic_string_view<char, std::__1::char_traits<char> >)

Unexecuted instantiation: compile.cc:re2::BeginPtr(std::__1::basic_string_view<char, std::__1::char_traits<char> >)

Unexecuted instantiation: prog.cc:re2::BeginPtr(std::__1::basic_string_view<char, std::__1::char_traits<char> >)

Unexecuted instantiation: dfa.cc:re2::BeginPtr(std::__1::basic_string_view<char, std::__1::char_traits<char> >)

Unexecuted instantiation: onepass.cc:re2::BeginPtr(std::__1::basic_string_view<char, std::__1::char_traits<char> >)

Unexecuted instantiation: nfa.cc:re2::BeginPtr(std::__1::basic_string_view<char, std::__1::char_traits<char> >)

Unexecuted instantiation: bitstate.cc:re2::BeginPtr(std::__1::basic_string_view<char, std::__1::char_traits<char> >)

static inline const char* EndPtr(absl::string_view s) {

  return s.data() + s.size();

}

Unexecuted instantiation: re2.cc:re2::EndPtr(std::__1::basic_string_view<char, std::__1::char_traits<char> >)

Unexecuted instantiation: compile.cc:re2::EndPtr(std::__1::basic_string_view<char, std::__1::char_traits<char> >)

Unexecuted instantiation: prog.cc:re2::EndPtr(std::__1::basic_string_view<char, std::__1::char_traits<char> >)

Unexecuted instantiation: dfa.cc:re2::EndPtr(std::__1::basic_string_view<char, std::__1::char_traits<char> >)

Unexecuted instantiation: onepass.cc:re2::EndPtr(std::__1::basic_string_view<char, std::__1::char_traits<char> >)

Unexecuted instantiation: nfa.cc:re2::EndPtr(std::__1::basic_string_view<char, std::__1::char_traits<char> >)

Unexecuted instantiation: bitstate.cc:re2::EndPtr(std::__1::basic_string_view<char, std::__1::char_traits<char> >)

}  // namespace re2

#endif  // RE2_PROG_H_