// Copyright 2003-2009 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.

#ifndef RE2_RE2_H_
#define RE2_RE2_H_

// C++ interface to the re2 regular-expression library.
// RE2 supports Perl-style regular expressions (with extensions like
// \d, \w, \s, ...).
//
// -----------------------------------------------------------------------
// REGEXP SYNTAX:
//
// This module uses the re2 library and hence supports
// its syntax for regular expressions, which is similar to Perl's with
// some of the more complicated things thrown away.  In particular,
// backreferences and generalized assertions are not available, nor is \Z.
//
// See https://github.com/google/re2/wiki/Syntax for the syntax
// supported by RE2, and a comparison with PCRE and PERL regexps.
//
// For those not familiar with Perl's regular expressions,
// here are some examples of the most commonly used extensions:
//
//   "hello (\\w+) world"  -- \w matches a "word" character
//   "version (\\d+)"      -- \d matches a digit
//   "hello\\s+world"      -- \s matches any whitespace character
//   "\\b(\\w+)\\b"        -- \b matches non-empty string at word boundary
//   "(?i)hello"           -- (?i) turns on case-insensitive matching
//   "/\\*(.*?)\\*/"       -- .*? matches . minimum no. of times possible
//
// The double backslashes are needed when writing C++ string literals.
// However, they should NOT be used when writing C++11 raw string literals:
//
//   R"(hello (\w+) world)"  -- \w matches a "word" character
//   R"(version (\d+))"      -- \d matches a digit
//   R"(hello\s+world)"      -- \s matches any whitespace character
//   R"(\b(\w+)\b)"          -- \b matches non-empty string at word boundary
//   R"((?i)hello)"          -- (?i) turns on case-insensitive matching
//   R"(/\*(.*?)\*/)"        -- .*? matches . minimum no. of times possible
//
// When using UTF-8 encoding, case-insensitive matching will perform
// simple case folding, not full case folding.
//
// -----------------------------------------------------------------------
// MATCHING INTERFACE:
//
// The "FullMatch" operation checks that supplied text matches a
// supplied pattern exactly.
//
// Example: successful match
//    CHECK(RE2::FullMatch("hello", "h.*o"));
//
// Example: unsuccessful match (requires full match):
//    CHECK(!RE2::FullMatch("hello", "e"));
//
// -----------------------------------------------------------------------
// UTF-8 AND THE MATCHING INTERFACE:
//
// By default, the pattern and input text are interpreted as UTF-8.
// The RE2::Latin1 option causes them to be interpreted as Latin-1.
//
// Example:
//    CHECK(RE2::FullMatch(utf8_string, RE2(utf8_pattern)));
//    CHECK(RE2::FullMatch(latin1_string, RE2(latin1_pattern, RE2::Latin1)));
//
// -----------------------------------------------------------------------
// SUBMATCH EXTRACTION:
//
// You can supply extra pointer arguments to extract submatches.
// On match failure, none of the pointees will have been modified.
// On match success, the submatches will be converted (as necessary) and
// their values will be assigned to their pointees until all conversions
// have succeeded or one conversion has failed.
// On conversion failure, the pointees will be in an indeterminate state
// because the caller has no way of knowing which conversion failed.
// However, conversion cannot fail for types like string and StringPiece
// that do not inspect the submatch contents. Hence, in the common case
// where all of the pointees are of such types, failure is always due to
// match failure and thus none of the pointees will have been modified.
//
// Example: extracts "ruby" into "s" and 1234 into "i"
//    int i;
//    std::string s;
//    CHECK(RE2::FullMatch("ruby:1234", "(\\w+):(\\d+)", &s, &i));
//
// Example: fails because string cannot be stored in integer
//    CHECK(!RE2::FullMatch("ruby", "(.*)", &i));
//
// Example: fails because there aren't enough sub-patterns
//    CHECK(!RE2::FullMatch("ruby:1234", "\\w+:\\d+", &s));
//
// Example: does not try to extract any extra sub-patterns
//    CHECK(RE2::FullMatch("ruby:1234", "(\\w+):(\\d+)", &s));
//
// Example: does not try to extract into NULL
//    CHECK(RE2::FullMatch("ruby:1234", "(\\w+):(\\d+)", NULL, &i));
//
// Example: integer overflow causes failure
//    CHECK(!RE2::FullMatch("ruby:1234567891234", "\\w+:(\\d+)", &i));
//
// NOTE(rsc): Asking for submatches slows successful matches quite a bit.
// This may get a little faster in the future, but right now is slower
// than PCRE.  On the other hand, failed matches run *very* fast (faster
// than PCRE), as do matches without submatch extraction.
//
// -----------------------------------------------------------------------
// PARTIAL MATCHES
//
// You can use the "PartialMatch" operation when you want the pattern
// to match any substring of the text.
//
// Example: simple search for a string:
//      CHECK(RE2::PartialMatch("hello", "ell"));
//
// Example: find first number in a string
//      int number;
//      CHECK(RE2::PartialMatch("x*100 + 20", "(\\d+)", &number));
//      CHECK_EQ(number, 100);
//
// -----------------------------------------------------------------------
// PRE-COMPILED REGULAR EXPRESSIONS
//
// RE2 makes it easy to use any string as a regular expression, without
// requiring a separate compilation step.
//
// If speed is of the essence, you can create a pre-compiled "RE2"
// object from the pattern and use it multiple times.  If you do so,
// you can typically parse text faster than with sscanf.
//
// Example: precompile pattern for faster matching:
//    RE2 pattern("h.*o");
//    while (ReadLine(&str)) {
//      if (RE2::FullMatch(str, pattern)) ...;
//    }
//
// -----------------------------------------------------------------------
// SCANNING TEXT INCREMENTALLY
//
// The "Consume" operation may be useful if you want to repeatedly
// match regular expressions at the front of a string and skip over
// them as they match.  This requires use of the "StringPiece" type,
// which represents a sub-range of a real string.
//
// Example: read lines of the form "var = value" from a string.
//      std::string contents = ...;     // Fill string somehow
//      StringPiece input(contents);    // Wrap a StringPiece around it
//
//      std::string var;
//      int value;
//      while (RE2::Consume(&input, "(\\w+) = (\\d+)\n", &var, &value)) {
//        ...;
//      }
//
// Each successful call to "Consume" will set "var/value", and also
// advance "input" so it points past the matched text.  Note that if the
// regular expression matches an empty string, input will advance
// by 0 bytes.  If the regular expression being used might match
// an empty string, the loop body must check for this case and either
// advance the string or break out of the loop.
//
// The "FindAndConsume" operation is similar to "Consume" but does not
// anchor your match at the beginning of the string.  For example, you
// could extract all words from a string by repeatedly calling
//     RE2::FindAndConsume(&input, "(\\w+)", &word)
//
// -----------------------------------------------------------------------
// USING VARIABLE NUMBER OF ARGUMENTS
//
// The above operations require you to know the number of arguments
// when you write the code.  This is not always possible or easy (for
// example, the regular expression may be calculated at run time).
// You can use the "N" version of the operations when the number of
// match arguments are determined at run time.
//
// Example:
//   const RE2::Arg* args[10];
//   int n;
//   // ... populate args with pointers to RE2::Arg values ...
//   // ... set n to the number of RE2::Arg objects ...
//   bool match = RE2::FullMatchN(input, pattern, args, n);
//
// The last statement is equivalent to
//
//   bool match = RE2::FullMatch(input, pattern,
//                               *args[0], *args[1], ..., *args[n - 1]);
//
// -----------------------------------------------------------------------
// PARSING HEX/OCTAL/C-RADIX NUMBERS
//
// By default, if you pass a pointer to a numeric value, the
// corresponding text is interpreted as a base-10 number.  You can
// instead wrap the pointer with a call to one of the operators Hex(),
// Octal(), or CRadix() to interpret the text in another base.  The
// CRadix operator interprets C-style "0" (base-8) and "0x" (base-16)
// prefixes, but defaults to base-10.
//
// Example:
//   int a, b, c, d;
//   CHECK(RE2::FullMatch("100 40 0100 0x40", "(.*) (.*) (.*) (.*)",
//         RE2::Octal(&a), RE2::Hex(&b), RE2::CRadix(&c), RE2::CRadix(&d));
// will leave 64 in a, b, c, and d.

#include <algorithm>
#include <map>
#include <mutex>
#include <stddef.h>
#include <stdint.h>
#include <string>
#include <type_traits>
#include <vector>

#if defined(__APPLE__)
#include <TargetConditionals.h>
#endif

#include "stringpiece.h"

namespace re2 {
class Prog;
class Regexp;
} // namespace re2

namespace re2 {

// Interface for regular expression matching.  Also corresponds to a
// pre-compiled regular expression.  An "RE2" object is safe for
// concurrent use by multiple threads.
class RE2 {
public:
    // We convert user-passed pointers into special Arg objects
    class Arg;
    class Options;

    // Defined in set.h.
    class Set;

    enum ErrorCode {
        NoError = 0,

        // Unexpected error
        ErrorInternal,

        // Parse errors
        ErrorBadEscape,         // bad escape sequence
        ErrorBadCharClass,      // bad character class
        ErrorBadCharRange,      // bad character class range
        ErrorMissingBracket,    // missing closing ]
        ErrorMissingParen,      // missing closing )
        ErrorUnexpectedParen,   // unexpected closing )
        ErrorTrailingBackslash, // trailing \ at end of regexp
        ErrorRepeatArgument,    // repeat argument missing, e.g. "*"
        ErrorRepeatSize,        // bad repetition argument
        ErrorRepeatOp,          // bad repetition operator
        ErrorBadPerlOp,         // bad perl operator
        ErrorBadUTF8,           // invalid UTF-8 in regexp
        ErrorBadNamedCapture,   // bad named capture group
        ErrorPatternTooLarge    // pattern too large (compile failed)
    };

    // Predefined common options.
    // If you need more complicated things, instantiate
    // an Option class, possibly passing one of these to
    // the Option constructor, change the settings, and pass that
    // Option class to the RE2 constructor.
    enum CannedOptions {
        DefaultOptions = 0,
        Latin1, // treat input as Latin-1 (default UTF-8)
        POSIX,  // POSIX syntax, leftmost-longest match
        Quiet   // do not log about regexp parse errors
    };

    // Need to have the const char* and const std::string& forms for implicit
    // conversions when passing string literals to FullMatch and PartialMatch.
    // Otherwise the StringPiece form would be sufficient.
    RE2(const char *pattern);
    RE2(const std::string &pattern);
    RE2(const StringPiece &pattern);
    RE2(const StringPiece &pattern, const Options &options);
    ~RE2();

    // Not copyable.
    // RE2 objects are expensive. You should probably use std::shared_ptr<RE2>
    // instead. If you really must copy, RE2(first.pattern(), first.options())
    // effectively does so: it produces a second object that mimics the first.
    RE2(const RE2 &) = delete;
    RE2 &operator=(const RE2 &) = delete;
    // Not movable.
    // RE2 objects are thread-safe and logically immutable. You should probably
    // use std::unique_ptr<RE2> instead. Otherwise, consider std::deque<RE2> if
    // direct emplacement into a container is desired. If you really must move,
    // be prepared to submit a design document along with your feature request.
    RE2(RE2 &&) = delete;
    RE2 &operator=(RE2 &&) = delete;

    // Returns whether RE2 was created properly.
    bool ok() const { return error_code() == NoError; }

    // The string specification for this RE2.  E.g.
    //   RE2 re("ab*c?d+");
    //   re.pattern();    // "ab*c?d+"
    const std::string &pattern() const { return *pattern_; }

    // If RE2 could not be created properly, returns an error string.
    // Else returns the empty string.
    const std::string &error() const { return *error_; }

    // If RE2 could not be created properly, returns an error code.
    // Else returns RE2::NoError (== 0).
    ErrorCode error_code() const { return error_code_; }

    // If RE2 could not be created properly, returns the offending
    // portion of the regexp.
    const std::string &error_arg() const { return *error_arg_; }

    // Returns the program size, a very approximate measure of a regexp's "cost".
    // Larger numbers are more expensive than smaller numbers.
    int ProgramSize() const;
    int ReverseProgramSize() const;

    // If histogram is not null, outputs the program fanout
    // as a histogram bucketed by powers of 2.
    // Returns the number of the largest non-empty bucket.
    int ProgramFanout(std::vector<int> *histogram) const;
    int ReverseProgramFanout(std::vector<int> *histogram) const;

    // Returns the underlying Regexp; not for general use.
    // Returns entire_regexp_ so that callers don't need
    // to know about prefix_ and prefix_foldcase_.
    re2::Regexp *Regexp() const { return entire_regexp_; }

    /***** The array-based matching interface ******/

    // The functions here have names ending in 'N' and are used to implement
    // the functions whose names are the prefix before the 'N'. It is sometimes
    // useful to invoke them directly, but the syntax is awkward, so the 'N'-less
    // versions should be preferred.
    static bool FullMatchN(const StringPiece &text, const RE2 &re, const Arg *const args[], int n);
    static bool PartialMatchN(const StringPiece &text, const RE2 &re, const Arg *const args[], int n);
    static bool ConsumeN(StringPiece *input, const RE2 &re, const Arg *const args[], int n);
    static bool FindAndConsumeN(StringPiece *input, const RE2 &re, const Arg *const args[], int n);

private:
    template <typename F, typename SP>
    static inline bool Apply(F f, SP sp, const RE2 &re) {
        return f(sp, re, NULL, 0);
    }

    template <typename F, typename SP, typename... A>
    static inline bool Apply(F f, SP sp, const RE2 &re, const A &...a) {
        const Arg *const args[] = {&a...};
        const int n = sizeof...(a);
        return f(sp, re, args, n);
    }

public:
    // In order to allow FullMatch() et al. to be called with a varying number
    // of arguments of varying types, we use two layers of variadic templates.
    // The first layer constructs the temporary Arg objects. The second layer
    // (above) constructs the array of pointers to the temporary Arg objects.

    /***** The useful part: the matching interface *****/

    // Matches "text" against "re".  If pointer arguments are
    // supplied, copies matched sub-patterns into them.
    //
    // You can pass in a "const char*" or a "std::string" for "text".
    // You can pass in a "const char*" or a "std::string" or a "RE2" for "re".
    //
    // The provided pointer arguments can be pointers to any scalar numeric
    // type, or one of:
    //    std::string     (matched piece is copied to string)
    //    StringPiece     (StringPiece is mutated to point to matched piece)
    //    T               (where "bool T::ParseFrom(const char*, size_t)" exists)
    //    (void*)NULL     (the corresponding matched sub-pattern is not copied)
    //
    // Returns true iff all of the following conditions are satisfied:
    //   a. "text" matches "re" fully - from the beginning to the end of "text".
    //   b. The number of matched sub-patterns is >= number of supplied pointers.
    //   c. The "i"th argument has a suitable type for holding the
    //      string captured as the "i"th sub-pattern.  If you pass in
    //      NULL for the "i"th argument, or pass fewer arguments than
    //      number of sub-patterns, the "i"th captured sub-pattern is
    //      ignored.
    //
    // CAVEAT: An optional sub-pattern that does not exist in the
    // matched string is assigned the empty string.  Therefore, the
    // following will return false (because the empty string is not a
    // valid number):
    //    int number;
    //    RE2::FullMatch("abc", "[a-z]+(\\d+)?", &number);
    template <typename... A>
    static bool FullMatch(const StringPiece &text, const RE2 &re, A &&...a) {
        return Apply(FullMatchN, text, re, Arg(std::forward<A>(a))...);
    }

    // Like FullMatch(), except that "re" is allowed to match a substring
    // of "text".
    //
    // Returns true iff all of the following conditions are satisfied:
    //   a. "text" matches "re" partially - for some substring of "text".
    //   b. The number of matched sub-patterns is >= number of supplied pointers.
    //   c. The "i"th argument has a suitable type for holding the
    //      string captured as the "i"th sub-pattern.  If you pass in
    //      NULL for the "i"th argument, or pass fewer arguments than
    //      number of sub-patterns, the "i"th captured sub-pattern is
    //      ignored.
    template <typename... A>
    static bool PartialMatch(const StringPiece &text, const RE2 &re, A &&...a) {
        return Apply(PartialMatchN, text, re, Arg(std::forward<A>(a))...);
    }

    // Like FullMatch() and PartialMatch(), except that "re" has to match
    // a prefix of the text, and "input" is advanced past the matched
    // text.  Note: "input" is modified iff this routine returns true
    // and "re" matched a non-empty substring of "input".
    //
    // Returns true iff all of the following conditions are satisfied:
    //   a. "input" matches "re" partially - for some prefix of "input".
    //   b. The number of matched sub-patterns is >= number of supplied pointers.
    //   c. The "i"th argument has a suitable type for holding the
    //      string captured as the "i"th sub-pattern.  If you pass in
    //      NULL for the "i"th argument, or pass fewer arguments than
    //      number of sub-patterns, the "i"th captured sub-pattern is
    //      ignored.
    template <typename... A>
    static bool Consume(StringPiece *input, const RE2 &re, A &&...a) {
        return Apply(ConsumeN, input, re, Arg(std::forward<A>(a))...);
    }

    // Like Consume(), but does not anchor the match at the beginning of
    // the text.  That is, "re" need not start its match at the beginning
    // of "input".  For example, "FindAndConsume(s, "(\\w+)", &word)" finds
    // the next word in "s" and stores it in "word".
    //
    // Returns true iff all of the following conditions are satisfied:
    //   a. "input" matches "re" partially - for some substring of "input".
    //   b. The number of matched sub-patterns is >= number of supplied pointers.
    //   c. The "i"th argument has a suitable type for holding the
    //      string captured as the "i"th sub-pattern.  If you pass in
    //      NULL for the "i"th argument, or pass fewer arguments than
    //      number of sub-patterns, the "i"th captured sub-pattern is
    //      ignored.
    template <typename... A>
    static bool FindAndConsume(StringPiece *input, const RE2 &re, A &&...a) {
        return Apply(FindAndConsumeN, input, re, Arg(std::forward<A>(a))...);
    }

    // Replace the first match of "re" in "str" with "rewrite".
    // Within "rewrite", backslash-escaped digits (\1 to \9) can be
    // used to insert text matching corresponding parenthesized group
    // from the pattern.  \0 in "rewrite" refers to the entire matching
    // text.  E.g.,
    //
    //   std::string s = "yabba dabba doo";
    //   CHECK(RE2::Replace(&s, "b+", "d"));
    //
    // will leave "s" containing "yada dabba doo"
    //
    // Returns true if the pattern matches and a replacement occurs,
    // false otherwise.
    static bool Replace(std::string *str, const RE2 &re, const StringPiece &rewrite);

    // Like Replace(), except replaces successive non-overlapping occurrences
    // of the pattern in the string with the rewrite. E.g.
    //
    //   std::string s = "yabba dabba doo";
    //   CHECK(RE2::GlobalReplace(&s, "b+", "d"));
    //
    // will leave "s" containing "yada dada doo"
    // Replacements are not subject to re-matching.
    //
    // Because GlobalReplace only replaces non-overlapping matches,
    // replacing "ana" within "banana" makes only one replacement, not two.
    //
    // Returns the number of replacements made.
    static int GlobalReplace(std::string *str, const RE2 &re, const StringPiece &rewrite);

    // Like Replace, except that if the pattern matches, "rewrite"
    // is copied into "out" with substitutions.  The non-matching
    // portions of "text" are ignored.
    //
    // Returns true iff a match occurred and the extraction happened
    // successfully;  if no match occurs, the string is left unaffected.
    //
    // REQUIRES: "text" must not alias any part of "*out".
    static bool Extract(const StringPiece &text, const RE2 &re, const StringPiece &rewrite, std::string *out);

    // Escapes all potentially meaningful regexp characters in
    // 'unquoted'.  The returned string, used as a regular expression,
    // will match exactly the original string.  For example,
    //           1.5-2.0?
    // may become:
    //           1\.5\-2\.0\?
    static std::string QuoteMeta(const StringPiece &unquoted);

    // 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) const;

    // Generic matching interface

    // Type of match.
    enum Anchor {
        UNANCHORED,   // No anchoring
        ANCHOR_START, // Anchor at start only
        ANCHOR_BOTH   // Anchor at start and end
    };

    // Return the number of capturing subpatterns, or -1 if the
    // regexp wasn't valid on construction.  The overall match ($0)
    // does not count: if the regexp is "(a)(b)", returns 2.
    int NumberOfCapturingGroups() const { return num_captures_; }

    // Return a map from names to capturing indices.
    // The map records the index of the leftmost group
    // with the given name.
    // Only valid until the re is deleted.
    const std::map<std::string, int> &NamedCapturingGroups() const;

    // Return a map from capturing indices to names.
    // The map has no entries for unnamed groups.
    // Only valid until the re is deleted.
    const std::map<int, std::string> &CapturingGroupNames() const;

    // General matching routine.
    // Match against text starting at offset startpos
    // and stopping the search at offset endpos.
    // Returns true if match found, false if not.
    // On a successful match, fills in submatch[] (up to nsubmatch entries)
    // with information about submatches.
    // I.e. matching RE2("(foo)|(bar)baz") on "barbazbla" will return true, with
    // submatch[0] = "barbaz", submatch[1].data() = NULL, submatch[2] = "bar",
    // submatch[3].data() = NULL, ..., up to submatch[nsubmatch-1].data() = NULL.
    // Caveat: submatch[] may be clobbered even on match failure.
    //
    // Don't ask for more match information than you will use:
    // runs much faster with nsubmatch == 1 than nsubmatch > 1, and
    // runs even faster if nsubmatch == 0.
    // Doesn't make sense to use nsubmatch > 1 + NumberOfCapturingGroups(),
    // but will be handled correctly.
    //
    // Passing text == StringPiece(NULL, 0) will be handled like any other
    // empty string, but note that on return, it will not be possible to tell
    // whether submatch i matched the empty string or did not match:
    // either way, submatch[i].data() == NULL.
    bool Match(const StringPiece &text, size_t startpos, size_t endpos, Anchor re_anchor, StringPiece *submatch, int nsubmatch) const;

    // Check that the given rewrite string is suitable for use with this
    // regular expression.  It checks that:
    //   * The regular expression has enough parenthesized subexpressions
    //     to satisfy all of the \N tokens in rewrite
    //   * The rewrite string doesn't have any syntax errors.  E.g.,
    //     '\' followed by anything other than a digit or '\'.
    // A true return value guarantees that Replace() and Extract() won't
    // fail because of a bad rewrite string.
    bool CheckRewriteString(const StringPiece &rewrite, std::string *error) const;

    // Returns the maximum submatch needed for the rewrite to be done by
    // Replace(). E.g. if rewrite == "foo \\2,\\1", returns 2.
    static int MaxSubmatch(const StringPiece &rewrite);

    // Append the "rewrite" string, with backslash subsitutions from "vec",
    // to string "out".
    // Returns true on success.  This method can fail because of a malformed
    // rewrite string.  CheckRewriteString guarantees that the rewrite will
    // be sucessful.
    bool Rewrite(std::string *out, const StringPiece &rewrite, const StringPiece *vec, int veclen) const;

    // Constructor options
    class Options {
    public:
        // The options are (defaults in parentheses):
        //
        //   utf8             (true)  text and pattern are UTF-8; otherwise Latin-1
        //   posix_syntax     (false) restrict regexps to POSIX egrep syntax
        //   longest_match    (false) search for longest match, not first match
        //   log_errors       (true)  log syntax and execution errors to ERROR
        //   max_mem          (see below)  approx. max memory footprint of RE2
        //   literal          (false) interpret string as literal, not regexp
        //   never_nl         (false) never match \n, even if it is in regexp
        //   dot_nl           (false) dot matches everything including new line
        //   never_capture    (false) parse all parens as non-capturing
        //   case_sensitive   (true)  match is case-sensitive (regexp can override
        //                              with (?i) unless in posix_syntax mode)
        //
        // The following options are only consulted when posix_syntax == true.
        // When posix_syntax == false, these features are always enabled and
        // cannot be turned off; to perform multi-line matching in that case,
        // begin the regexp with (?m).
        //   perl_classes     (false) allow Perl's \d \s \w \D \S \W
        //   word_boundary    (false) allow Perl's \b \B (word boundary and not)
        //   one_line         (false) ^ and $ only match beginning and end of text
        //
        // The max_mem option controls how much memory can be used
        // to hold the compiled form of the regexp (the Prog) and
        // its cached DFA graphs.  Code Search placed limits on the number
        // of Prog instructions and DFA states: 10,000 for both.
        // In RE2, those limits would translate to about 240 KB per Prog
        // and perhaps 2.5 MB per DFA (DFA state sizes vary by regexp; RE2 does a
        // better job of keeping them small than Code Search did).
        // Each RE2 has two Progs (one forward, one reverse), and each Prog
        // can have two DFAs (one first match, one longest match).
        // That makes 4 DFAs:
        //
        //   forward, first-match    - used for UNANCHORED or ANCHOR_START searches
        //                               if opt.longest_match() == false
        //   forward, longest-match  - used for all ANCHOR_BOTH searches,
        //                               and the other two kinds if
        //                               opt.longest_match() == true
        //   reverse, first-match    - never used
        //   reverse, longest-match  - used as second phase for unanchored searches
        //
        // The RE2 memory budget is statically divided between the two
        // Progs and then the DFAs: two thirds to the forward Prog
        // and one third to the reverse Prog.  The forward Prog gives half
        // of what it has left over to each of its DFAs.  The reverse Prog
        // gives it all to its longest-match DFA.
        //
        // Once a DFA fills its budget, it flushes its cache and starts over.
        // If this happens too often, RE2 falls back on the NFA implementation.

        // For now, make the default budget something close to Code Search.
        static const int kDefaultMaxMem = 8 << 20;

        enum Encoding { EncodingUTF8 = 1, EncodingLatin1 };

        Options()
            : max_mem_(kDefaultMaxMem), encoding_(EncodingUTF8), posix_syntax_(false), longest_match_(false), log_errors_(true), literal_(false),
              never_nl_(false), dot_nl_(false), never_capture_(false), case_sensitive_(true), perl_classes_(false), word_boundary_(false),
              one_line_(false) {}

        /*implicit*/ Options(CannedOptions);

        int64_t max_mem() const { return max_mem_; }
        void set_max_mem(int64_t m) { max_mem_ = m; }

        Encoding encoding() const { return encoding_; }
        void set_encoding(Encoding encoding) { encoding_ = encoding; }

        bool posix_syntax() const { return posix_syntax_; }
        void set_posix_syntax(bool b) { posix_syntax_ = b; }

        bool longest_match() const { return longest_match_; }
        void set_longest_match(bool b) { longest_match_ = b; }

        bool log_errors() const { return log_errors_; }
        void set_log_errors(bool b) { log_errors_ = b; }

        bool literal() const { return literal_; }
        void set_literal(bool b) { literal_ = b; }

        bool never_nl() const { return never_nl_; }
        void set_never_nl(bool b) { never_nl_ = b; }

        bool dot_nl() const { return dot_nl_; }
        void set_dot_nl(bool b) { dot_nl_ = b; }

        bool never_capture() const { return never_capture_; }
        void set_never_capture(bool b) { never_capture_ = b; }

        bool case_sensitive() const { return case_sensitive_; }
        void set_case_sensitive(bool b) { case_sensitive_ = b; }

        bool perl_classes() const { return perl_classes_; }
        void set_perl_classes(bool b) { perl_classes_ = b; }

        bool word_boundary() const { return word_boundary_; }
        void set_word_boundary(bool b) { word_boundary_ = b; }

        bool one_line() const { return one_line_; }
        void set_one_line(bool b) { one_line_ = b; }

        void Copy(const Options &src) { *this = src; }

        int ParseFlags() const;

    private:
        int64_t max_mem_;
        Encoding encoding_;
        bool posix_syntax_;
        bool longest_match_;
        bool log_errors_;
        bool literal_;
        bool never_nl_;
        bool dot_nl_;
        bool never_capture_;
        bool case_sensitive_;
        bool perl_classes_;
        bool word_boundary_;
        bool one_line_;
    };

    // Returns the options set in the constructor.
    const Options &options() const { return options_; }

    // Argument converters; see below.
    template <typename T>
    static Arg CRadix(T *ptr);
    template <typename T>
    static Arg Hex(T *ptr);
    template <typename T>
    static Arg Octal(T *ptr);

    // Controls the maximum count permitted by GlobalReplace(); -1 is unlimited.
    // FOR FUZZING ONLY.
    static void FUZZING_ONLY_set_maximum_global_replace_count(int i);

private:
    void Init(const StringPiece &pattern, const Options &options);

    bool DoMatch(const StringPiece &text, Anchor re_anchor, size_t *consumed, const Arg *const args[], int n) const;

    re2::Prog *ReverseProg() const;

    // First cache line is relatively cold fields.
    const std::string *pattern_;   // string regular expression
    Options options_;              // option flags
    re2::Regexp *entire_regexp_;   // parsed regular expression
    re2::Regexp *suffix_regexp_;   // parsed regular expression, prefix_ removed
    const std::string *error_;     // error indicator (or points to empty string)
    const std::string *error_arg_; // fragment of regexp showing error (or ditto)

    // Second cache line is relatively hot fields.
    // These are ordered oddly to pack everything.
    int num_captures_;          // number of capturing groups
    ErrorCode error_code_ : 29; // error code (29 bits is more than enough)
    bool longest_match_ : 1;    // cached copy of options_.longest_match()
    bool is_one_pass_ : 1;      // can use prog_->SearchOnePass?
    bool prefix_foldcase_ : 1;  // prefix_ is ASCII case-insensitive
    std::string prefix_;        // required prefix (before suffix_regexp_)
    re2::Prog *prog_;           // compiled program for regexp

    // Reverse Prog for DFA execution only
    mutable re2::Prog *rprog_;
    // Map from capture names to indices
    mutable const std::map<std::string, int> *named_groups_;
    // Map from capture indices to names
    mutable const std::map<int, std::string> *group_names_;

    mutable std::once_flag rprog_once_;
    mutable std::once_flag named_groups_once_;
    mutable std::once_flag group_names_once_;
};

/***** Implementation details *****/

namespace re2_internal {

// Types for which the 3-ary Parse() function template has specializations.
template <typename T>
struct Parse3ary : public std::false_type {};
template <>
struct Parse3ary<void> : public std::true_type {};
template <>
struct Parse3ary<std::string> : public std::true_type {};
template <>
struct Parse3ary<StringPiece> : public std::true_type {};
template <>
struct Parse3ary<char> : public std::true_type {};
template <>
struct Parse3ary<signed char> : public std::true_type {};
template <>
struct Parse3ary<unsigned char> : public std::true_type {};
template <>
struct Parse3ary<float> : public std::true_type {};
template <>
struct Parse3ary<double> : public std::true_type {};

template <typename T>
bool Parse(const char *str, size_t n, T *dest);

// Types for which the 4-ary Parse() function template has specializations.
template <typename T>
struct Parse4ary : public std::false_type {};
template <>
struct Parse4ary<long> : public std::true_type {};
template <>
struct Parse4ary<unsigned long> : public std::true_type {};
template <>
struct Parse4ary<short> : public std::true_type {};
template <>
struct Parse4ary<unsigned short> : public std::true_type {};
template <>
struct Parse4ary<int> : public std::true_type {};
template <>
struct Parse4ary<unsigned int> : public std::true_type {};
template <>
struct Parse4ary<long long> : public std::true_type {};
template <>
struct Parse4ary<unsigned long long> : public std::true_type {};

template <typename T>
bool Parse(const char *str, size_t n, T *dest, int radix);

} // namespace re2_internal

class RE2::Arg {
private:
    template <typename T>
    using CanParse3ary = typename std::enable_if<re2_internal::Parse3ary<T>::value, int>::type;

    template <typename T>
    using CanParse4ary = typename std::enable_if<re2_internal::Parse4ary<T>::value, int>::type;

#if !defined(_MSC_VER)
    template <typename T>
    using CanParseFrom =
        typename std::enable_if<std::is_member_function_pointer<decltype(static_cast<bool (T::*)(const char *, size_t)>(&T::ParseFrom))>::value,
                                int>::type;
#endif

public:
    Arg() : Arg(nullptr) {}
    Arg(std::nullptr_t ptr) : arg_(ptr), parser_(DoNothing) {}

    template <typename T, CanParse3ary<T> = 0>
    Arg(T *ptr) : arg_(ptr), parser_(DoParse3ary<T>) {}

    template <typename T, CanParse4ary<T> = 0>
    Arg(T *ptr) : arg_(ptr), parser_(DoParse4ary<T>) {}

#if !defined(_MSC_VER)
    template <typename T, CanParseFrom<T> = 0>
    Arg(T *ptr) : arg_(ptr), parser_(DoParseFrom<T>) {}
#endif

    typedef bool (*Parser)(const char *str, size_t n, void *dest);

    template <typename T>
    Arg(T *ptr, Parser parser) : arg_(ptr), parser_(parser) {}

    bool Parse(const char *str, size_t n) const { return (*parser_)(str, n, arg_); }

private:
    static bool DoNothing(const char * /*str*/, size_t /*n*/, void * /*dest*/) { return true; }

    template <typename T>
    static bool DoParse3ary(const char *str, size_t n, void *dest) {
        return re2_internal::Parse(str, n, reinterpret_cast<T *>(dest));
    }

    template <typename T>
    static bool DoParse4ary(const char *str, size_t n, void *dest) {
        return re2_internal::Parse(str, n, reinterpret_cast<T *>(dest), 10);
    }

#if !defined(_MSC_VER)
    template <typename T>
    static bool DoParseFrom(const char *str, size_t n, void *dest) {
        if (dest == NULL)
            return true;
        return reinterpret_cast<T *>(dest)->ParseFrom(str, n);
    }
#endif

    void *arg_;
    Parser parser_;
};

template <typename T>
inline RE2::Arg RE2::CRadix(T *ptr) {
    return RE2::Arg(ptr, [](const char *str, size_t n, void *dest) -> bool { return re2_internal::Parse(str, n, reinterpret_cast<T *>(dest), 0); });
}

template <typename T>
inline RE2::Arg RE2::Hex(T *ptr) {
    return RE2::Arg(ptr, [](const char *str, size_t n, void *dest) -> bool { return re2_internal::Parse(str, n, reinterpret_cast<T *>(dest), 16); });
}

template <typename T>
inline RE2::Arg RE2::Octal(T *ptr) {
    return RE2::Arg(ptr, [](const char *str, size_t n, void *dest) -> bool { return re2_internal::Parse(str, n, reinterpret_cast<T *>(dest), 8); });
}

// Silence warnings about missing initializers for members of LazyRE2.
#if !defined(__clang__) && defined(__GNUC__) && __GNUC__ >= 6
#pragma GCC diagnostic ignored "-Wmissing-field-initializers"
#endif

// Helper for writing global or static RE2s safely.
// Write
//     static LazyRE2 re = {".*"};
// and then use *re instead of writing
//     static RE2 re(".*");
// The former is more careful about multithreaded
// situations than the latter.
//
// N.B. This class never deletes the RE2 object that
// it constructs: that's a feature, so that it can be used
// for global and function static variables.
class LazyRE2 {
private:
    struct NoArg {};

public:
    typedef RE2 element_type; // support std::pointer_traits

    // Constructor omitted to preserve braced initialization in C++98.

    // Pretend to be a pointer to Type (never NULL due to on-demand creation):
    RE2 &operator*() const { return *get(); }
    RE2 *operator->() const { return get(); }

    // Named accessor/initializer:
    RE2 *get() const {
        std::call_once(once_, &LazyRE2::Init, this);
        return ptr_;
    }

    // All data fields must be public to support {"foo"} initialization.
    const char *pattern_;
    RE2::CannedOptions options_;
    NoArg barrier_against_excess_initializers_;

    mutable RE2 *ptr_;
    mutable std::once_flag once_;

private:
    static void Init(const LazyRE2 *lazy_re2) { lazy_re2->ptr_ = new RE2(lazy_re2->pattern_, lazy_re2->options_); }

    void operator=(const LazyRE2 &); // disallowed
};

namespace hooks {

// Most platforms support thread_local. Older versions of iOS don't support
// thread_local, but for the sake of brevity, we lump together all versions
// of Apple platforms that aren't macOS. If an iOS application really needs
// the context pointee someday, we can get more specific then...
//
// As per https://github.com/google/re2/issues/325, thread_local support in
// MinGW seems to be buggy. (FWIW, Abseil folks also avoid it.)
#define RE2_HAVE_THREAD_LOCAL
#if (defined(__APPLE__) && !(defined(TARGET_OS_OSX) && TARGET_OS_OSX)) || defined(__MINGW32__)
#undef RE2_HAVE_THREAD_LOCAL
#endif

// A hook must not make any assumptions regarding the lifetime of the context
// pointee beyond the current invocation of the hook. Pointers and references
// obtained via the context pointee should be considered invalidated when the
// hook returns. Hence, any data about the context pointee (e.g. its pattern)
// would have to be copied in order for it to be kept for an indefinite time.
//
// A hook must not use RE2 for matching. Control flow reentering RE2::Match()
// could result in infinite mutual recursion. To discourage that possibility,
// RE2 will not maintain the context pointer correctly when used in that way.
#ifdef RE2_HAVE_THREAD_LOCAL
extern thread_local const RE2 *context;
#endif

struct DFAStateCacheReset {
    int64_t state_budget;
    size_t state_cache_size;
};

struct DFASearchFailure {
    // Nothing yet...
};

#define DECLARE_HOOK(type)                                                                                                                           \
    using type##Callback = void(const type &);                                                                                                       \
    void Set##type##Hook(type##Callback *cb);                                                                                                        \
    type##Callback *Get##type##Hook();

DECLARE_HOOK(DFAStateCacheReset)
DECLARE_HOOK(DFASearchFailure)

#undef DECLARE_HOOK

} // namespace hooks

} // namespace re2

using re2::LazyRE2;
using re2::RE2;

#endif // RE2_RE2_H_