Replace RE2 import with a dependency

third_party/re2/re2/regexp.h

-// Copyright 2006 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.
-
-// --- SPONSORED LINK --------------------------------------------------
-// If you want to use this library for regular expression matching,
-// you should use re2/re2.h, which provides a class RE2 that
-// mimics the PCRE interface provided by PCRE's C++ wrappers.
-// This header describes the low-level interface used to implement RE2
-// and may change in backwards-incompatible ways from time to time.
-// In contrast, RE2's interface will not.
-// ---------------------------------------------------------------------
-
-// Regular expression library: parsing, execution, and manipulation
-// of regular expressions.
-//
-// Any operation that traverses the Regexp structures should be written
-// using Regexp::Walker (see walker-inl.h), not recursively, because deeply nested
-// regular expressions such as x++++++++++++++++++++... might cause recursive
-// traversals to overflow the stack.
-//
-// It is the caller's responsibility to provide appropriate mutual exclusion
-// around manipulation of the regexps.  RE2 does this.
-//
-// PARSING
-//
-// Regexp::Parse parses regular expressions encoded in UTF-8.
-// The default syntax is POSIX extended regular expressions,
-// with the following changes:
-//
-//   1.  Backreferences (optional in POSIX EREs) are not supported.
-//         (Supporting them precludes the use of DFA-based
-//          matching engines.)
-//
-//   2.  Collating elements and collation classes are not supported.
-//         (No one has needed or wanted them.)
-//
-// The exact syntax accepted can be modified by passing flags to
-// Regexp::Parse.  In particular, many of the basic Perl additions
-// are available.  The flags are documented below (search for LikePerl).
-//
-// If parsed with the flag Regexp::Latin1, both the regular expression
-// and the input to the matching routines are assumed to be encoded in
-// Latin-1, not UTF-8.
-//
-// EXECUTION
-//
-// Once Regexp has parsed a regular expression, it provides methods
-// to search text using that regular expression.  These methods are
-// implemented via calling out to other regular expression libraries.
-// (Let's call them the sublibraries.)
-//
-// To call a sublibrary, Regexp does not simply prepare a
-// string version of the regular expression and hand it to the
-// sublibrary.  Instead, Regexp prepares, from its own parsed form, the
-// corresponding internal representation used by the sublibrary.
-// This has the drawback of needing to know the internal representation
-// used by the sublibrary, but it has two important benefits:
-//
-//   1. The syntax and meaning of regular expressions is guaranteed
-//      to be that used by Regexp's parser, not the syntax expected
-//      by the sublibrary.  Regexp might accept a restricted or
-//      expanded syntax for regular expressions as compared with
-//      the sublibrary.  As long as Regexp can translate from its
-//      internal form into the sublibrary's, clients need not know
-//      exactly which sublibrary they are using.
-//
-//   2. The sublibrary parsers are bypassed.  For whatever reason,
-//      sublibrary regular expression parsers often have security
-//      problems.  For example, plan9grep's regular expression parser
-//      has a buffer overflow in its handling of large character
-//      classes, and PCRE's parser has had buffer overflow problems
-//      in the past.  Security-team requires sandboxing of sublibrary
-//      regular expression parsers.  Avoiding the sublibrary parsers
-//      avoids the sandbox.
-//
-// The execution methods we use now are provided by the compiled form,
-// Prog, described in prog.h
-//
-// MANIPULATION
-//
-// Unlike other regular expression libraries, Regexp makes its parsed
-// form accessible to clients, so that client code can analyze the
-// parsed regular expressions.
-
-#ifndef RE2_REGEXP_H__
-#define RE2_REGEXP_H__
-
-#include "util/util.h"
-#include "re2/stringpiece.h"
-
-namespace re2 {
-
-// Keep in sync with string list kOpcodeNames[] in testing/dump.cc
-enum RegexpOp {
-  // Matches no strings.
-  kRegexpNoMatch = 1,
-
-  // Matches empty string.
-  kRegexpEmptyMatch,
-
-  // Matches rune_.
-  kRegexpLiteral,
-
-  // Matches runes_.
-  kRegexpLiteralString,
-
-  // Matches concatenation of sub_[0..nsub-1].
-  kRegexpConcat,
-  // Matches union of sub_[0..nsub-1].
-  kRegexpAlternate,
-
-  // Matches sub_[0] zero or more times.
-  kRegexpStar,
-  // Matches sub_[0] one or more times.
-  kRegexpPlus,
-  // Matches sub_[0] zero or one times.
-  kRegexpQuest,
-
-  // Matches sub_[0] at least min_ times, at most max_ times.
-  // max_ == -1 means no upper limit.
-  kRegexpRepeat,
-
-  // Parenthesized (capturing) subexpression.  Index is cap_.
-  // Optionally, capturing name is name_.
-  kRegexpCapture,
-
-  // Matches any character.
-  kRegexpAnyChar,
-
-  // Matches any byte [sic].
-  kRegexpAnyByte,
-
-  // Matches empty string at beginning of line.
-  kRegexpBeginLine,
-  // Matches empty string at end of line.
-  kRegexpEndLine,
-
-  // Matches word boundary "\b".
-  kRegexpWordBoundary,
-  // Matches not-a-word boundary "\B".
-  kRegexpNoWordBoundary,
-
-  // Matches empty string at beginning of text.
-  kRegexpBeginText,
-  // Matches empty string at end of text.
-  kRegexpEndText,
-
-  // Matches character class given by cc_.
-  kRegexpCharClass,
-
-  // Forces match of entire expression right now,
-  // with match ID match_id_ (used by RE2::Set).
-  kRegexpHaveMatch,
-
-  kMaxRegexpOp = kRegexpHaveMatch,
-};
-
-// Keep in sync with string list in regexp.cc
-enum RegexpStatusCode {
-  // No error
-  kRegexpSuccess = 0,
-
-  // Unexpected error
-  kRegexpInternalError,
-
-  // Parse errors
-  kRegexpBadEscape,          // bad escape sequence
-  kRegexpBadCharClass,       // bad character class
-  kRegexpBadCharRange,       // bad character class range
-  kRegexpMissingBracket,     // missing closing ]
-  kRegexpMissingParen,       // missing closing )
-  kRegexpTrailingBackslash,  // at end of regexp
-  kRegexpRepeatArgument,     // repeat argument missing, e.g. "*"
-  kRegexpRepeatSize,         // bad repetition argument
-  kRegexpRepeatOp,           // bad repetition operator
-  kRegexpBadPerlOp,          // bad perl operator
-  kRegexpBadUTF8,            // invalid UTF-8 in regexp
-  kRegexpBadNamedCapture,    // bad named capture
-};
-
-// Error status for certain operations.
-class RegexpStatus {
- public:
-  RegexpStatus() : code_(kRegexpSuccess), tmp_(NULL) {}
-  ~RegexpStatus() { delete tmp_; }
-
-  void set_code(enum RegexpStatusCode code) { code_ = code; }
-  void set_error_arg(const StringPiece& error_arg) { error_arg_ = error_arg; }
-  void set_tmp(string* tmp) { delete tmp_; tmp_ = tmp; }
-  enum RegexpStatusCode code() const { return code_; }
-  const StringPiece& error_arg() const { return error_arg_; }
-  bool ok() const { return code() == kRegexpSuccess; }
-
-  // Copies state from status.
-  void Copy(const RegexpStatus& status);
-
-  // Returns text equivalent of code, e.g.:
-  //   "Bad character class"
-  static string CodeText(enum RegexpStatusCode code);
-
-  // Returns text describing error, e.g.:
-  //   "Bad character class: [z-a]"
-  string Text() const;
-
- private:
-  enum RegexpStatusCode code_;  // Kind of error
-  StringPiece error_arg_;       // Piece of regexp containing syntax error.
-  string* tmp_;                 // Temporary storage, possibly where error_arg_ is.
-
-  DISALLOW_COPY_AND_ASSIGN(RegexpStatus);
-};
-
-// Walkers to implement Simplify.
-class CoalesceWalker;
-class SimplifyWalker;
-
-// Compiled form; see prog.h
-class Prog;
-
-struct RuneRange {
-  RuneRange() : lo(0), hi(0) { }
-  RuneRange(int l, int h) : lo(l), hi(h) { }
-  Rune lo;
-  Rune hi;
-};
-
-// Less-than on RuneRanges treats a == b if they overlap at all.
-// This lets us look in a set to find the range covering a particular Rune.
-struct RuneRangeLess {
-  bool operator()(const RuneRange& a, const RuneRange& b) const {
-    return a.hi < b.lo;
-  }
-};
-
-class CharClassBuilder;
-
-class CharClass {
- public:
-  void Delete();
-
-  typedef RuneRange* iterator;
-  iterator begin() { return ranges_; }
-  iterator end() { return ranges_ + nranges_; }
-
-  int size() { return nrunes_; }
-  bool empty() { return nrunes_ == 0; }
-  bool full() { return nrunes_ == Runemax+1; }
-  bool FoldsASCII() { return folds_ascii_; }
-
-  bool Contains(Rune r);
-  CharClass* Negate();
-
- private:
-  CharClass();  // not implemented
-  ~CharClass();  // not implemented
-  static CharClass* New(int maxranges);
-
-  friend class CharClassBuilder;
-
-  bool folds_ascii_;
-  int nrunes_;
-  RuneRange *ranges_;
-  int nranges_;
-  DISALLOW_COPY_AND_ASSIGN(CharClass);
-};
-
-class Regexp {
- public:
-
-  // Flags for parsing.  Can be ORed together.
-  enum ParseFlags {
-    NoParseFlags = 0,
-    FoldCase     = 1<<0,   // Fold case during matching (case-insensitive).
-    Literal      = 1<<1,   // Treat s as literal string instead of a regexp.
-    ClassNL      = 1<<2,   // Allow char classes like [^a-z] and \D and \s
-                           // and [[:space:]] to match newline.
-    DotNL        = 1<<3,   // Allow . to match newline.
-    MatchNL      = ClassNL | DotNL,
-    OneLine      = 1<<4,   // Treat ^ and $ as only matching at beginning and
-                           // end of text, not around embedded newlines.
-                           // (Perl's default)
-    Latin1       = 1<<5,   // Regexp and text are in Latin1, not UTF-8.
-    NonGreedy    = 1<<6,   // Repetition operators are non-greedy by default.
-    PerlClasses  = 1<<7,   // Allow Perl character classes like \d.
-    PerlB        = 1<<8,   // Allow Perl's \b and \B.
-    PerlX        = 1<<9,   // Perl extensions:
-                           //   non-capturing parens - (?: )
-                           //   non-greedy operators - *? +? ?? {}?
-                           //   flag edits - (?i) (?-i) (?i: )
-                           //     i - FoldCase
-                           //     m - !OneLine
-                           //     s - DotNL
-                           //     U - NonGreedy
-                           //   line ends: \A \z
-                           //   \Q and \E to disable/enable metacharacters
-                           //   (?P<name>expr) for named captures
-                           //   \C to match any single byte
-    UnicodeGroups = 1<<10, // Allow \p{Han} for Unicode Han group
-                           //   and \P{Han} for its negation.
-    NeverNL      = 1<<11,  // Never match NL, even if the regexp mentions
-                           //   it explicitly.
-    NeverCapture = 1<<12,  // Parse all parens as non-capturing.
-
-    // As close to Perl as we can get.
-    LikePerl     = ClassNL | OneLine | PerlClasses | PerlB | PerlX |
-                   UnicodeGroups,
-
-    // Internal use only.
-    WasDollar    = 1<<15,  // on kRegexpEndText: was $ in regexp text
-  };
-
-  // Get.  No set, Regexps are logically immutable once created.
-  RegexpOp op() { return static_cast<RegexpOp>(op_); }
-  int nsub() { return nsub_; }
-  bool simple() { return simple_ != 0; }
-  enum ParseFlags parse_flags() { return static_cast<ParseFlags>(parse_flags_); }
-  int Ref();  // For testing.
-
-  Regexp** sub() {
-    if(nsub_ <= 1)
-      return &subone_;
-    else
-      return submany_;
-  }
-
-  int min() { DCHECK_EQ(op_, kRegexpRepeat); return min_; }
-  int max() { DCHECK_EQ(op_, kRegexpRepeat); return max_; }
-  Rune rune() { DCHECK_EQ(op_, kRegexpLiteral); return rune_; }
-  CharClass* cc() { DCHECK_EQ(op_, kRegexpCharClass); return cc_; }
-  int cap() { DCHECK_EQ(op_, kRegexpCapture); return cap_; }
-  const string* name() { DCHECK_EQ(op_, kRegexpCapture); return name_; }
-  Rune* runes() { DCHECK_EQ(op_, kRegexpLiteralString); return runes_; }
-  int nrunes() { DCHECK_EQ(op_, kRegexpLiteralString); return nrunes_; }
-  int match_id() { DCHECK_EQ(op_, kRegexpHaveMatch); return match_id_; }
-
-  // Increments reference count, returns object as convenience.
-  Regexp* Incref();
-
-  // Decrements reference count and deletes this object if count reaches 0.
-  void Decref();
-
-  // Parses string s to produce regular expression, returned.
-  // Caller must release return value with re->Decref().
-  // On failure, sets *status (if status != NULL) and returns NULL.
-  static Regexp* Parse(const StringPiece& s, ParseFlags flags,
-                       RegexpStatus* status);
-
-  // Returns a _new_ simplified version of the current regexp.
-  // Does not edit the current regexp.
-  // Caller must release return value with re->Decref().
-  // Simplified means that counted repetition has been rewritten
-  // into simpler terms and all Perl/POSIX features have been
-  // removed.  The result will capture exactly the same
-  // subexpressions the original did, unless formatted with ToString.
-  Regexp* Simplify();
-  friend class CoalesceWalker;
-  friend class SimplifyWalker;
-
-  // Parses the regexp src and then simplifies it and sets *dst to the
-  // string representation of the simplified form.  Returns true on success.
-  // Returns false and sets *status (if status != NULL) on parse error.
-  static bool SimplifyRegexp(const StringPiece& src, ParseFlags flags,
-                             string* dst,
-                             RegexpStatus* status);
-
-  // Returns the number of capturing groups in the regexp.
-  int NumCaptures();
-  friend class NumCapturesWalker;
-
-  // Returns a map from names to capturing group indices,
-  // or NULL if the regexp contains no named capture groups.
-  // The caller is responsible for deleting the map.
-  map<string, int>* NamedCaptures();
-
-  // Returns a map from capturing group indices to capturing group
-  // names or NULL if the regexp contains no named capture groups. The
-  // caller is responsible for deleting the map.
-  map<int, string>* CaptureNames();
-
-  // Returns a string representation of the current regexp,
-  // using as few parentheses as possible.
-  string ToString();
-
-  // Convenience functions.  They consume the passed reference,
-  // so in many cases you should use, e.g., Plus(re->Incref(), flags).
-  // They do not consume allocated arrays like subs or runes.
-  static Regexp* Plus(Regexp* sub, ParseFlags flags);
-  static Regexp* Star(Regexp* sub, ParseFlags flags);
-  static Regexp* Quest(Regexp* sub, ParseFlags flags);
-  static Regexp* Concat(Regexp** subs, int nsubs, ParseFlags flags);
-  static Regexp* Alternate(Regexp** subs, int nsubs, ParseFlags flags);
-  static Regexp* Capture(Regexp* sub, ParseFlags flags, int cap);
-  static Regexp* Repeat(Regexp* sub, ParseFlags flags, int min, int max);
-  static Regexp* NewLiteral(Rune rune, ParseFlags flags);
-  static Regexp* NewCharClass(CharClass* cc, ParseFlags flags);
-  static Regexp* LiteralString(Rune* runes, int nrunes, ParseFlags flags);
-  static Regexp* HaveMatch(int match_id, ParseFlags flags);
-
-  // Like Alternate but does not factor out common prefixes.
-  static Regexp* AlternateNoFactor(Regexp** subs, int nsubs, ParseFlags flags);
-
-  // Debugging function.  Returns string format for regexp
-  // that makes structure clear.  Does NOT use regexp syntax.
-  string Dump();
-
-  // Helper traversal class, defined fully in walker-inl.h.
-  template<typename T> class Walker;
-
-  // Compile to Prog.  See prog.h
-  // Reverse prog expects to be run over text backward.
-  // Construction and execution of prog will
-  // stay within approximately max_mem bytes of memory.
-  // If max_mem <= 0, a reasonable default is used.
-  Prog* CompileToProg(int64 max_mem);
-  Prog* CompileToReverseProg(int64 max_mem);
-
-  // Whether to expect this library to find exactly the same answer as PCRE
-  // when running this regexp.  Most regexps do mimic PCRE exactly, but a few
-  // obscure cases behave differently.  Technically this is more a property
-  // of the Prog than the Regexp, but the computation is much easier to do
-  // on the Regexp.  See mimics_pcre.cc for the exact conditions.
-  bool MimicsPCRE();
-
-  // Benchmarking function.
-  void NullWalk();
-
-  // Whether every match of this regexp must be anchored and
-  // begin with a non-empty fixed string (perhaps after ASCII
-  // case-folding).  If so, returns the prefix and the sub-regexp that
-  // follows it.
-  bool RequiredPrefix(string* prefix, bool *foldcase, Regexp** suffix);
-
- private:
-  // Constructor allocates vectors as appropriate for operator.
-  explicit Regexp(RegexpOp op, ParseFlags parse_flags);
-
-  // Use Decref() instead of delete to release Regexps.
-  // This is private to catch deletes at compile time.
-  ~Regexp();
-  void Destroy();
-  bool QuickDestroy();
-
-  // Helpers for Parse.  Listed here so they can edit Regexps.
-  class ParseState;
-  friend class ParseState;
-  friend bool ParseCharClass(StringPiece* s, Regexp** out_re,
-                             RegexpStatus* status);
-
-  // Helper for testing [sic].
-  friend bool RegexpEqualTestingOnly(Regexp*, Regexp*);
-
-  // Computes whether Regexp is already simple.
-  bool ComputeSimple();
-
-  // Constructor that generates a concatenation or alternation,
-  // enforcing the limit on the number of subexpressions for
-  // a particular Regexp.
-  static Regexp* ConcatOrAlternate(RegexpOp op, Regexp** subs, int nsubs,
-                                   ParseFlags flags, bool can_factor);
-
-  // Returns the leading string that re starts with.
-  // The returned Rune* points into a piece of re,
-  // so it must not be used after the caller calls re->Decref().
-  static Rune* LeadingString(Regexp* re, int* nrune, ParseFlags* flags);
-
-  // Removes the first n leading runes from the beginning of re.
-  // Edits re in place.
-  static void RemoveLeadingString(Regexp* re, int n);
-
-  // Returns the leading regexp in re's top-level concatenation.
-  // The returned Regexp* points at re or a sub-expression of re,
-  // so it must not be used after the caller calls re->Decref().
-  static Regexp* LeadingRegexp(Regexp* re);
-
-  // Removes LeadingRegexp(re) from re and returns the remainder.
-  // Might edit re in place.
-  static Regexp* RemoveLeadingRegexp(Regexp* re);
-
-  // Simplifies an alternation of literal strings by factoring out
-  // common prefixes.
-  static int FactorAlternation(Regexp** sub, int nsub, ParseFlags flags);
-  static int FactorAlternationRecursive(Regexp** sub, int nsub,
-                                        ParseFlags flags, int maxdepth);
-
-  // Is a == b?  Only efficient on regexps that have not been through
-  // Simplify yet - the expansion of a kRegexpRepeat will make this
-  // take a long time.  Do not call on such regexps, hence private.
-  static bool Equal(Regexp* a, Regexp* b);
-
-  // Allocate space for n sub-regexps.
-  void AllocSub(int n) {
-    if (n < 0 || static_cast<uint16>(n) != n)
-      LOG(FATAL) << "Cannot AllocSub " << n;
-    if (n > 1)
-      submany_ = new Regexp*[n];
-    nsub_ = n;
-  }
-
-  // Add Rune to LiteralString
-  void AddRuneToString(Rune r);
-
-  // Swaps this with that, in place.
-  void Swap(Regexp *that);
-
-  // Operator.  See description of operators above.
-  // uint8 instead of RegexpOp to control space usage.
-  uint8 op_;
-
-  // Is this regexp structure already simple
-  // (has it been returned by Simplify)?
-  // uint8 instead of bool to control space usage.
-  uint8 simple_;
-
-  // Flags saved from parsing and used during execution.
-  // (Only FoldCase is used.)
-  // uint16 instead of ParseFlags to control space usage.
-  uint16 parse_flags_;
-
-  // Reference count.  Exists so that SimplifyRegexp can build
-  // regexp structures that are dags rather than trees to avoid
-  // exponential blowup in space requirements.
-  // uint16 to control space usage.
-  // The standard regexp routines will never generate a
-  // ref greater than the maximum repeat count (100),
-  // but even so, Incref and Decref consult an overflow map
-  // when ref_ reaches kMaxRef.
-  uint16 ref_;
-  static const uint16 kMaxRef = 0xffff;
-
-  // Subexpressions.
-  // uint16 to control space usage.
-  // Concat and Alternate handle larger numbers of subexpressions
-  // by building concatenation or alternation trees.
-  // Other routines should call Concat or Alternate instead of
-  // filling in sub() by hand.
-  uint16 nsub_;
-  static const uint16 kMaxNsub = 0xffff;
-  union {
-    Regexp** submany_;  // if nsub_ > 1
-    Regexp* subone_;  // if nsub_ == 1
-  };
-
-  // Extra space for parse and teardown stacks.
-  Regexp* down_;
-
-  // Arguments to operator.  See description of operators above.
-  union {
-    struct {  // Repeat
-      int max_;
-      int min_;
-    };
-    struct {  // Capture
-      int cap_;
-      string* name_;
-    };
-    struct {  // LiteralString
-      int nrunes_;
-      Rune* runes_;
-    };
-    struct {  // CharClass
-      // These two could be in separate union members,
-      // but it wouldn't save any space (there are other two-word structs)
-      // and keeping them separate avoids confusion during parsing.
-      CharClass* cc_;
-      CharClassBuilder* ccb_;
-    };
-    Rune rune_;  // Literal
-    int match_id_;  // HaveMatch
-    void *the_union_[2];  // as big as any other element, for memset
-  };
-
-  DISALLOW_COPY_AND_ASSIGN(Regexp);
-};
-
-// Character class set: contains non-overlapping, non-abutting RuneRanges.
-typedef set<RuneRange, RuneRangeLess> RuneRangeSet;
-
-class CharClassBuilder {
- public:
-  CharClassBuilder();
-
-  typedef RuneRangeSet::iterator iterator;
-  iterator begin() { return ranges_.begin(); }
-  iterator end() { return ranges_.end(); }
-
-  int size() { return nrunes_; }
-  bool empty() { return nrunes_ == 0; }
-  bool full() { return nrunes_ == Runemax+1; }
-
-  bool Contains(Rune r);
-  bool FoldsASCII();
-  bool AddRange(Rune lo, Rune hi);  // returns whether class changed
-  CharClassBuilder* Copy();
-  void AddCharClass(CharClassBuilder* cc);
-  void Negate();
-  void RemoveAbove(Rune r);
-  CharClass* GetCharClass();
-  void AddRangeFlags(Rune lo, Rune hi, Regexp::ParseFlags parse_flags);
-
- private:
-  static const uint32 AlphaMask = (1<<26) - 1;
-  uint32 upper_;  // bitmap of A-Z
-  uint32 lower_;  // bitmap of a-z
-  int nrunes_;
-  RuneRangeSet ranges_;
-  DISALLOW_COPY_AND_ASSIGN(CharClassBuilder);
-};
-
-// Tell g++ that bitwise ops on ParseFlags produce ParseFlags.
-inline Regexp::ParseFlags operator|(Regexp::ParseFlags a, Regexp::ParseFlags b)
-{
-  return static_cast<Regexp::ParseFlags>(static_cast<int>(a) | static_cast<int>(b));
-}
-
-inline Regexp::ParseFlags operator^(Regexp::ParseFlags a, Regexp::ParseFlags b)
-{
-  return static_cast<Regexp::ParseFlags>(static_cast<int>(a) ^ static_cast<int>(b));
-}
-
-inline Regexp::ParseFlags operator&(Regexp::ParseFlags a, Regexp::ParseFlags b)
-{
-  return static_cast<Regexp::ParseFlags>(static_cast<int>(a) & static_cast<int>(b));
-}
-
-inline Regexp::ParseFlags operator~(Regexp::ParseFlags a)
-{
-  return static_cast<Regexp::ParseFlags>(~static_cast<int>(a));
-}
-
-
-
-}  // namespace re2
-
-#endif  // RE2_REGEXP_H__