| Index: third_party/re2/re2/dfa.cc
|
| diff --git a/third_party/re2/re2/dfa.cc b/third_party/re2/re2/dfa.cc
|
| new file mode 100644
|
| index 0000000000000000000000000000000000000000..344ef416653697ac98c002a142c1e552da9902ba
|
| --- /dev/null
|
| +++ b/third_party/re2/re2/dfa.cc
|
| @@ -0,0 +1,2088 @@
|
| +// Copyright 2008 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.
|
| +
|
| +// A DFA (deterministic finite automaton)-based regular expression search.
|
| +//
|
| +// The DFA search has two main parts: the construction of the automaton,
|
| +// which is represented by a graph of State structures, and the execution
|
| +// of the automaton over a given input string.
|
| +//
|
| +// The basic idea is that the State graph is constructed so that the
|
| +// execution can simply start with a state s, and then for each byte c in
|
| +// the input string, execute "s = s->next[c]", checking at each point whether
|
| +// the current s represents a matching state.
|
| +//
|
| +// The simple explanation just given does convey the essence of this code,
|
| +// but it omits the details of how the State graph gets constructed as well
|
| +// as some performance-driven optimizations to the execution of the automaton.
|
| +// All these details are explained in the comments for the code following
|
| +// the definition of class DFA.
|
| +//
|
| +// See http://swtch.com/~rsc/regexp/ for a very bare-bones equivalent.
|
| +
|
| +#include "re2/prog.h"
|
| +#include "re2/stringpiece.h"
|
| +#include "util/atomicops.h"
|
| +#include "util/flags.h"
|
| +#include "util/sparse_set.h"
|
| +
|
| +#define NO_THREAD_SAFETY_ANALYSIS
|
| +
|
| +DEFINE_bool(re2_dfa_bail_when_slow, true,
|
| + "Whether the RE2 DFA should bail out early "
|
| + "if the NFA would be faster (for testing).");
|
| +
|
| +namespace re2 {
|
| +
|
| +#if !defined(__linux__) /* only Linux seems to have memrchr */
|
| +static void* memrchr(const void* s, int c, size_t n) {
|
| + const unsigned char* p = (const unsigned char*)s;
|
| + for (p += n; n > 0; n--)
|
| + if (*--p == c)
|
| + return (void*)p;
|
| +
|
| + return NULL;
|
| +}
|
| +#endif
|
| +
|
| +// Changing this to true compiles in prints that trace execution of the DFA.
|
| +// Generates a lot of output -- only useful for debugging.
|
| +static const bool DebugDFA = false;
|
| +
|
| +// A DFA implementation of a regular expression program.
|
| +// Since this is entirely a forward declaration mandated by C++,
|
| +// some of the comments here are better understood after reading
|
| +// the comments in the sections that follow the DFA definition.
|
| +class DFA {
|
| + public:
|
| + DFA(Prog* prog, Prog::MatchKind kind, int64 max_mem);
|
| + ~DFA();
|
| + bool ok() const { return !init_failed_; }
|
| + Prog::MatchKind kind() { return kind_; }
|
| +
|
| + // Searches for the regular expression in text, which is considered
|
| + // as a subsection of context for the purposes of interpreting flags
|
| + // like ^ and $ and \A and \z.
|
| + // Returns whether a match was found.
|
| + // If a match is found, sets *ep to the end point of the best match in text.
|
| + // If "anchored", the match must begin at the start of text.
|
| + // If "want_earliest_match", the match that ends first is used, not
|
| + // necessarily the best one.
|
| + // If "run_forward" is true, the DFA runs from text.begin() to text.end().
|
| + // If it is false, the DFA runs from text.end() to text.begin(),
|
| + // returning the leftmost end of the match instead of the rightmost one.
|
| + // If the DFA cannot complete the search (for example, if it is out of
|
| + // memory), it sets *failed and returns false.
|
| + bool Search(const StringPiece& text, const StringPiece& context,
|
| + bool anchored, bool want_earliest_match, bool run_forward,
|
| + bool* failed, const char** ep, vector<int>* matches);
|
| +
|
| + // Builds out all states for the entire DFA. FOR TESTING ONLY
|
| + // Returns number of states.
|
| + int BuildAllStates();
|
| +
|
| + // Computes min and max for matching strings. Won't return strings
|
| + // bigger than maxlen.
|
| + bool PossibleMatchRange(string* min, string* max, int maxlen);
|
| +
|
| + // These data structures are logically private, but C++ makes it too
|
| + // difficult to mark them as such.
|
| + class Workq;
|
| + class RWLocker;
|
| + class StateSaver;
|
| +
|
| + // A single DFA state. The DFA is represented as a graph of these
|
| + // States, linked by the next_ pointers. If in state s and reading
|
| + // byte c, the next state should be s->next_[c].
|
| + struct State {
|
| + inline bool IsMatch() const { return flag_ & kFlagMatch; }
|
| + void SaveMatch(vector<int>* v);
|
| +
|
| + int* inst_; // Instruction pointers in the state.
|
| + int ninst_; // # of inst_ pointers.
|
| + uint flag_; // Empty string bitfield flags in effect on the way
|
| + // into this state, along with kFlagMatch if this
|
| + // is a matching state.
|
| + State** next_; // Outgoing arrows from State,
|
| + // one per input byte class
|
| + };
|
| +
|
| + enum {
|
| + kByteEndText = 256, // imaginary byte at end of text
|
| +
|
| + kFlagEmptyMask = 0xFFF, // State.flag_: bits holding kEmptyXXX flags
|
| + kFlagMatch = 0x1000, // State.flag_: this is a matching state
|
| + kFlagLastWord = 0x2000, // State.flag_: last byte was a word char
|
| + kFlagNeedShift = 16, // needed kEmpty bits are or'ed in shifted left
|
| + };
|
| +
|
| + // STL function structures for use with unordered_set.
|
| + struct StateEqual {
|
| + bool operator()(const State* a, const State* b) const {
|
| + if (a == b)
|
| + return true;
|
| + if (a == NULL || b == NULL)
|
| + return false;
|
| + if (a->ninst_ != b->ninst_)
|
| + return false;
|
| + if (a->flag_ != b->flag_)
|
| + return false;
|
| + for (int i = 0; i < a->ninst_; i++)
|
| + if (a->inst_[i] != b->inst_[i])
|
| + return false;
|
| + return true; // they're equal
|
| + }
|
| + };
|
| + struct StateHash {
|
| + size_t operator()(const State* a) const {
|
| + if (a == NULL)
|
| + return 0;
|
| + const char* s = reinterpret_cast<const char*>(a->inst_);
|
| + int len = a->ninst_ * sizeof a->inst_[0];
|
| + if (sizeof(size_t) == sizeof(uint32))
|
| + return Hash32StringWithSeed(s, len, a->flag_);
|
| + else
|
| + return Hash64StringWithSeed(s, len, a->flag_);
|
| + }
|
| + };
|
| +
|
| + typedef unordered_set<State*, StateHash, StateEqual> StateSet;
|
| +
|
| +
|
| + private:
|
| + // Special "firstbyte" values for a state. (Values >= 0 denote actual bytes.)
|
| + enum {
|
| + kFbUnknown = -1, // No analysis has been performed.
|
| + kFbMany = -2, // Many bytes will lead out of this state.
|
| + kFbNone = -3, // No bytes lead out of this state.
|
| + };
|
| +
|
| + enum {
|
| + // Indices into start_ for unanchored searches.
|
| + // Add kStartAnchored for anchored searches.
|
| + kStartBeginText = 0, // text at beginning of context
|
| + kStartBeginLine = 2, // text at beginning of line
|
| + kStartAfterWordChar = 4, // text follows a word character
|
| + kStartAfterNonWordChar = 6, // text follows non-word character
|
| + kMaxStart = 8,
|
| +
|
| + kStartAnchored = 1,
|
| + };
|
| +
|
| + // Resets the DFA State cache, flushing all saved State* information.
|
| + // Releases and reacquires cache_mutex_ via cache_lock, so any
|
| + // State* existing before the call are not valid after the call.
|
| + // Use a StateSaver to preserve important states across the call.
|
| + // cache_mutex_.r <= L < mutex_
|
| + // After: cache_mutex_.w <= L < mutex_
|
| + void ResetCache(RWLocker* cache_lock);
|
| +
|
| + // Looks up and returns the State corresponding to a Workq.
|
| + // L >= mutex_
|
| + State* WorkqToCachedState(Workq* q, uint flag);
|
| +
|
| + // Looks up and returns a State matching the inst, ninst, and flag.
|
| + // L >= mutex_
|
| + State* CachedState(int* inst, int ninst, uint flag);
|
| +
|
| + // Clear the cache entirely.
|
| + // Must hold cache_mutex_.w or be in destructor.
|
| + void ClearCache();
|
| +
|
| + // Converts a State into a Workq: the opposite of WorkqToCachedState.
|
| + // L >= mutex_
|
| + static void StateToWorkq(State* s, Workq* q);
|
| +
|
| + // Runs a State on a given byte, returning the next state.
|
| + State* RunStateOnByteUnlocked(State*, int); // cache_mutex_.r <= L < mutex_
|
| + State* RunStateOnByte(State*, int); // L >= mutex_
|
| +
|
| + // Runs a Workq on a given byte followed by a set of empty-string flags,
|
| + // producing a new Workq in nq. If a match instruction is encountered,
|
| + // sets *ismatch to true.
|
| + // L >= mutex_
|
| + void RunWorkqOnByte(Workq* q, Workq* nq,
|
| + int c, uint flag, bool* ismatch,
|
| + Prog::MatchKind kind,
|
| + int new_byte_loop);
|
| +
|
| + // Runs a Workq on a set of empty-string flags, producing a new Workq in nq.
|
| + // L >= mutex_
|
| + void RunWorkqOnEmptyString(Workq* q, Workq* nq, uint flag);
|
| +
|
| + // Adds the instruction id to the Workq, following empty arrows
|
| + // according to flag.
|
| + // L >= mutex_
|
| + void AddToQueue(Workq* q, int id, uint flag);
|
| +
|
| + // For debugging, returns a text representation of State.
|
| + static string DumpState(State* state);
|
| +
|
| + // For debugging, returns a text representation of a Workq.
|
| + static string DumpWorkq(Workq* q);
|
| +
|
| + // Search parameters
|
| + struct SearchParams {
|
| + SearchParams(const StringPiece& text, const StringPiece& context,
|
| + RWLocker* cache_lock)
|
| + : text(text), context(context),
|
| + anchored(false),
|
| + want_earliest_match(false),
|
| + run_forward(false),
|
| + start(NULL),
|
| + firstbyte(kFbUnknown),
|
| + cache_lock(cache_lock),
|
| + failed(false),
|
| + ep(NULL),
|
| + matches(NULL) { }
|
| +
|
| + StringPiece text;
|
| + StringPiece context;
|
| + bool anchored;
|
| + bool want_earliest_match;
|
| + bool run_forward;
|
| + State* start;
|
| + int firstbyte;
|
| + RWLocker *cache_lock;
|
| + bool failed; // "out" parameter: whether search gave up
|
| + const char* ep; // "out" parameter: end pointer for match
|
| + vector<int>* matches;
|
| +
|
| + private:
|
| + DISALLOW_EVIL_CONSTRUCTORS(SearchParams);
|
| + };
|
| +
|
| + // Before each search, the parameters to Search are analyzed by
|
| + // AnalyzeSearch to determine the state in which to start and the
|
| + // "firstbyte" for that state, if any.
|
| + struct StartInfo {
|
| + StartInfo() : start(NULL), firstbyte(kFbUnknown) { }
|
| + State* start;
|
| + volatile int firstbyte;
|
| + };
|
| +
|
| + // Fills in params->start and params->firstbyte using
|
| + // the other search parameters. Returns true on success,
|
| + // false on failure.
|
| + // cache_mutex_.r <= L < mutex_
|
| + bool AnalyzeSearch(SearchParams* params);
|
| + bool AnalyzeSearchHelper(SearchParams* params, StartInfo* info, uint flags);
|
| +
|
| + // The generic search loop, inlined to create specialized versions.
|
| + // cache_mutex_.r <= L < mutex_
|
| + // Might unlock and relock cache_mutex_ via params->cache_lock.
|
| + inline bool InlinedSearchLoop(SearchParams* params,
|
| + bool have_firstbyte,
|
| + bool want_earliest_match,
|
| + bool run_forward);
|
| +
|
| + // The specialized versions of InlinedSearchLoop. The three letters
|
| + // at the ends of the name denote the true/false values used as the
|
| + // last three parameters of InlinedSearchLoop.
|
| + // cache_mutex_.r <= L < mutex_
|
| + // Might unlock and relock cache_mutex_ via params->cache_lock.
|
| + bool SearchFFF(SearchParams* params);
|
| + bool SearchFFT(SearchParams* params);
|
| + bool SearchFTF(SearchParams* params);
|
| + bool SearchFTT(SearchParams* params);
|
| + bool SearchTFF(SearchParams* params);
|
| + bool SearchTFT(SearchParams* params);
|
| + bool SearchTTF(SearchParams* params);
|
| + bool SearchTTT(SearchParams* params);
|
| +
|
| + // The main search loop: calls an appropriate specialized version of
|
| + // InlinedSearchLoop.
|
| + // cache_mutex_.r <= L < mutex_
|
| + // Might unlock and relock cache_mutex_ via params->cache_lock.
|
| + bool FastSearchLoop(SearchParams* params);
|
| +
|
| + // For debugging, a slow search loop that calls InlinedSearchLoop
|
| + // directly -- because the booleans passed are not constants, the
|
| + // loop is not specialized like the SearchFFF etc. versions, so it
|
| + // runs much more slowly. Useful only for debugging.
|
| + // cache_mutex_.r <= L < mutex_
|
| + // Might unlock and relock cache_mutex_ via params->cache_lock.
|
| + bool SlowSearchLoop(SearchParams* params);
|
| +
|
| + // Looks up bytes in bytemap_ but handles case c == kByteEndText too.
|
| + int ByteMap(int c) {
|
| + if (c == kByteEndText)
|
| + return prog_->bytemap_range();
|
| + return prog_->bytemap()[c];
|
| + }
|
| +
|
| + // Constant after initialization.
|
| + Prog* prog_; // The regular expression program to run.
|
| + Prog::MatchKind kind_; // The kind of DFA.
|
| + int start_unanchored_; // start of unanchored program
|
| + bool init_failed_; // initialization failed (out of memory)
|
| +
|
| + Mutex mutex_; // mutex_ >= cache_mutex_.r
|
| +
|
| + // Scratch areas, protected by mutex_.
|
| + Workq* q0_; // Two pre-allocated work queues.
|
| + Workq* q1_;
|
| + int* astack_; // Pre-allocated stack for AddToQueue
|
| + int nastack_;
|
| +
|
| + // State* cache. Many threads use and add to the cache simultaneously,
|
| + // holding cache_mutex_ for reading and mutex_ (above) when adding.
|
| + // If the cache fills and needs to be discarded, the discarding is done
|
| + // while holding cache_mutex_ for writing, to avoid interrupting other
|
| + // readers. Any State* pointers are only valid while cache_mutex_
|
| + // is held.
|
| + Mutex cache_mutex_;
|
| + int64 mem_budget_; // Total memory budget for all States.
|
| + int64 state_budget_; // Amount of memory remaining for new States.
|
| + StateSet state_cache_; // All States computed so far.
|
| + StartInfo start_[kMaxStart];
|
| + bool cache_warned_; // have printed to LOG(INFO) about the cache
|
| +};
|
| +
|
| +// Shorthand for casting to uint8*.
|
| +static inline const uint8* BytePtr(const void* v) {
|
| + return reinterpret_cast<const uint8*>(v);
|
| +}
|
| +
|
| +// Work queues
|
| +
|
| +// Marks separate thread groups of different priority
|
| +// in the work queue when in leftmost-longest matching mode.
|
| +#define Mark (-1)
|
| +
|
| +// Internally, the DFA uses a sparse array of
|
| +// program instruction pointers as a work queue.
|
| +// In leftmost longest mode, marks separate sections
|
| +// of workq that started executing at different
|
| +// locations in the string (earlier locations first).
|
| +class DFA::Workq : public SparseSet {
|
| + public:
|
| + // Constructor: n is number of normal slots, maxmark number of mark slots.
|
| + Workq(int n, int maxmark) :
|
| + SparseSet(n+maxmark),
|
| + n_(n),
|
| + maxmark_(maxmark),
|
| + nextmark_(n),
|
| + last_was_mark_(true) {
|
| + }
|
| +
|
| + bool is_mark(int i) { return i >= n_; }
|
| +
|
| + int maxmark() { return maxmark_; }
|
| +
|
| + void clear() {
|
| + SparseSet::clear();
|
| + nextmark_ = n_;
|
| + }
|
| +
|
| + void mark() {
|
| + if (last_was_mark_)
|
| + return;
|
| + last_was_mark_ = false;
|
| + SparseSet::insert_new(nextmark_++);
|
| + }
|
| +
|
| + int size() {
|
| + return n_ + maxmark_;
|
| + }
|
| +
|
| + void insert(int id) {
|
| + if (contains(id))
|
| + return;
|
| + insert_new(id);
|
| + }
|
| +
|
| + void insert_new(int id) {
|
| + last_was_mark_ = false;
|
| + SparseSet::insert_new(id);
|
| + }
|
| +
|
| + private:
|
| + int n_; // size excluding marks
|
| + int maxmark_; // maximum number of marks
|
| + int nextmark_; // id of next mark
|
| + bool last_was_mark_; // last inserted was mark
|
| + DISALLOW_EVIL_CONSTRUCTORS(Workq);
|
| +};
|
| +
|
| +DFA::DFA(Prog* prog, Prog::MatchKind kind, int64 max_mem)
|
| + : prog_(prog),
|
| + kind_(kind),
|
| + init_failed_(false),
|
| + q0_(NULL),
|
| + q1_(NULL),
|
| + astack_(NULL),
|
| + mem_budget_(max_mem),
|
| + cache_warned_(false) {
|
| + if (DebugDFA)
|
| + fprintf(stderr, "\nkind %d\n%s\n", (int)kind_, prog_->DumpUnanchored().c_str());
|
| + int nmark = 0;
|
| + start_unanchored_ = 0;
|
| + if (kind_ == Prog::kLongestMatch) {
|
| + nmark = prog->size();
|
| + start_unanchored_ = prog->start_unanchored();
|
| + }
|
| + nastack_ = 2 * prog->size() + nmark;
|
| +
|
| + // Account for space needed for DFA, q0, q1, astack.
|
| + mem_budget_ -= sizeof(DFA);
|
| + mem_budget_ -= (prog_->size() + nmark) *
|
| + (sizeof(int)+sizeof(int)) * 2; // q0, q1
|
| + mem_budget_ -= nastack_ * sizeof(int); // astack
|
| + if (mem_budget_ < 0) {
|
| + LOG(INFO) << StringPrintf("DFA out of memory: prog size %lld mem %lld",
|
| + prog_->size(), max_mem);
|
| + init_failed_ = true;
|
| + return;
|
| + }
|
| +
|
| + state_budget_ = mem_budget_;
|
| +
|
| + // Make sure there is a reasonable amount of working room left.
|
| + // At minimum, the search requires room for two states in order
|
| + // to limp along, restarting frequently. We'll get better performance
|
| + // if there is room for a larger number of states, say 20.
|
| + int one_state = sizeof(State) + (prog_->size()+nmark)*sizeof(int) +
|
| + (prog_->bytemap_range()+1)*sizeof(State*);
|
| + if (state_budget_ < 20*one_state) {
|
| + LOG(INFO) << StringPrintf("DFA out of memory: prog size %lld mem %lld",
|
| + prog_->size(), max_mem);
|
| + init_failed_ = true;
|
| + return;
|
| + }
|
| +
|
| + q0_ = new Workq(prog->size(), nmark);
|
| + q1_ = new Workq(prog->size(), nmark);
|
| + astack_ = new int[nastack_];
|
| +}
|
| +
|
| +DFA::~DFA() {
|
| + delete q0_;
|
| + delete q1_;
|
| + delete[] astack_;
|
| + ClearCache();
|
| +}
|
| +
|
| +// In the DFA state graph, s->next[c] == NULL means that the
|
| +// state has not yet been computed and needs to be. We need
|
| +// a different special value to signal that s->next[c] is a
|
| +// state that can never lead to a match (and thus the search
|
| +// can be called off). Hence DeadState.
|
| +#define DeadState reinterpret_cast<State*>(1)
|
| +
|
| +// Signals that the rest of the string matches no matter what it is.
|
| +#define FullMatchState reinterpret_cast<State*>(2)
|
| +
|
| +#define SpecialStateMax FullMatchState
|
| +
|
| +// Debugging printouts
|
| +
|
| +// For debugging, returns a string representation of the work queue.
|
| +string DFA::DumpWorkq(Workq* q) {
|
| + string s;
|
| + const char* sep = "";
|
| + for (DFA::Workq::iterator it = q->begin(); it != q->end(); ++it) {
|
| + if (q->is_mark(*it)) {
|
| + StringAppendF(&s, "|");
|
| + sep = "";
|
| + } else {
|
| + StringAppendF(&s, "%s%d", sep, *it);
|
| + sep = ",";
|
| + }
|
| + }
|
| + return s;
|
| +}
|
| +
|
| +// For debugging, returns a string representation of the state.
|
| +string DFA::DumpState(State* state) {
|
| + if (state == NULL)
|
| + return "_";
|
| + if (state == DeadState)
|
| + return "X";
|
| + if (state == FullMatchState)
|
| + return "*";
|
| + string s;
|
| + const char* sep = "";
|
| + StringAppendF(&s, "(%p)", state);
|
| + for (int i = 0; i < state->ninst_; i++) {
|
| + if (state->inst_[i] == Mark) {
|
| + StringAppendF(&s, "|");
|
| + sep = "";
|
| + } else {
|
| + StringAppendF(&s, "%s%d", sep, state->inst_[i]);
|
| + sep = ",";
|
| + }
|
| + }
|
| + StringAppendF(&s, " flag=%#x", state->flag_);
|
| + return s;
|
| +}
|
| +
|
| +//////////////////////////////////////////////////////////////////////
|
| +//
|
| +// DFA state graph construction.
|
| +//
|
| +// The DFA state graph is a heavily-linked collection of State* structures.
|
| +// The state_cache_ is a set of all the State structures ever allocated,
|
| +// so that if the same state is reached by two different paths,
|
| +// the same State structure can be used. This reduces allocation
|
| +// requirements and also avoids duplication of effort across the two
|
| +// identical states.
|
| +//
|
| +// A State is defined by an ordered list of instruction ids and a flag word.
|
| +//
|
| +// The choice of an ordered list of instructions differs from a typical
|
| +// textbook DFA implementation, which would use an unordered set.
|
| +// Textbook descriptions, however, only care about whether
|
| +// the DFA matches, not where it matches in the text. To decide where the
|
| +// DFA matches, we need to mimic the behavior of the dominant backtracking
|
| +// implementations like PCRE, which try one possible regular expression
|
| +// execution, then another, then another, stopping when one of them succeeds.
|
| +// The DFA execution tries these many executions in parallel, representing
|
| +// each by an instruction id. These pointers are ordered in the State.inst_
|
| +// list in the same order that the executions would happen in a backtracking
|
| +// search: if a match is found during execution of inst_[2], inst_[i] for i>=3
|
| +// can be discarded.
|
| +//
|
| +// Textbooks also typically do not consider context-aware empty string operators
|
| +// like ^ or $. These are handled by the flag word, which specifies the set
|
| +// of empty-string operators that should be matched when executing at the
|
| +// current text position. These flag bits are defined in prog.h.
|
| +// The flag word also contains two DFA-specific bits: kFlagMatch if the state
|
| +// is a matching state (one that reached a kInstMatch in the program)
|
| +// and kFlagLastWord if the last processed byte was a word character, for the
|
| +// implementation of \B and \b.
|
| +//
|
| +// The flag word also contains, shifted up 16 bits, the bits looked for by
|
| +// any kInstEmptyWidth instructions in the state. These provide a useful
|
| +// summary indicating when new flags might be useful.
|
| +//
|
| +// The permanent representation of a State's instruction ids is just an array,
|
| +// but while a state is being analyzed, these instruction ids are represented
|
| +// as a Workq, which is an array that allows iteration in insertion order.
|
| +
|
| +// NOTE(rsc): The choice of State construction determines whether the DFA
|
| +// mimics backtracking implementations (so-called leftmost first matching) or
|
| +// traditional DFA implementations (so-called leftmost longest matching as
|
| +// prescribed by POSIX). This implementation chooses to mimic the
|
| +// backtracking implementations, because we want to replace PCRE. To get
|
| +// POSIX behavior, the states would need to be considered not as a simple
|
| +// ordered list of instruction ids, but as a list of unordered sets of instruction
|
| +// ids. A match by a state in one set would inhibit the running of sets
|
| +// farther down the list but not other instruction ids in the same set. Each
|
| +// set would correspond to matches beginning at a given point in the string.
|
| +// This is implemented by separating different sets with Mark pointers.
|
| +
|
| +// Looks in the State cache for a State matching q, flag.
|
| +// If one is found, returns it. If one is not found, allocates one,
|
| +// inserts it in the cache, and returns it.
|
| +DFA::State* DFA::WorkqToCachedState(Workq* q, uint flag) {
|
| + if (DEBUG_MODE)
|
| + mutex_.AssertHeld();
|
| +
|
| + // Construct array of instruction ids for the new state.
|
| + // Only ByteRange, EmptyWidth, and Match instructions are useful to keep:
|
| + // those are the only operators with any effect in
|
| + // RunWorkqOnEmptyString or RunWorkqOnByte.
|
| + int* inst = new int[q->size()];
|
| + int n = 0;
|
| + uint needflags = 0; // flags needed by kInstEmptyWidth instructions
|
| + bool sawmatch = false; // whether queue contains guaranteed kInstMatch
|
| + bool sawmark = false; // whether queue contains a Mark
|
| + if (DebugDFA)
|
| + fprintf(stderr, "WorkqToCachedState %s [%#x]", DumpWorkq(q).c_str(), flag);
|
| + for (Workq::iterator it = q->begin(); it != q->end(); ++it) {
|
| + int id = *it;
|
| + if (sawmatch && (kind_ == Prog::kFirstMatch || q->is_mark(id)))
|
| + break;
|
| + if (q->is_mark(id)) {
|
| + if (n > 0 && inst[n-1] != Mark) {
|
| + sawmark = true;
|
| + inst[n++] = Mark;
|
| + }
|
| + continue;
|
| + }
|
| + Prog::Inst* ip = prog_->inst(id);
|
| + switch (ip->opcode()) {
|
| + case kInstAltMatch:
|
| + // This state will continue to a match no matter what
|
| + // the rest of the input is. If it is the highest priority match
|
| + // being considered, return the special FullMatchState
|
| + // to indicate that it's all matches from here out.
|
| + if (kind_ != Prog::kManyMatch &&
|
| + (kind_ != Prog::kFirstMatch ||
|
| + (it == q->begin() && ip->greedy(prog_))) &&
|
| + (kind_ != Prog::kLongestMatch || !sawmark) &&
|
| + (flag & kFlagMatch)) {
|
| + delete[] inst;
|
| + if (DebugDFA)
|
| + fprintf(stderr, " -> FullMatchState\n");
|
| + return FullMatchState;
|
| + }
|
| + // Fall through.
|
| + case kInstByteRange: // These are useful.
|
| + case kInstEmptyWidth:
|
| + case kInstMatch:
|
| + case kInstAlt: // Not useful, but necessary [*]
|
| + inst[n++] = *it;
|
| + if (ip->opcode() == kInstEmptyWidth)
|
| + needflags |= ip->empty();
|
| + if (ip->opcode() == kInstMatch && !prog_->anchor_end())
|
| + sawmatch = true;
|
| + break;
|
| +
|
| + default: // The rest are not.
|
| + break;
|
| + }
|
| +
|
| + // [*] kInstAlt would seem useless to record in a state, since
|
| + // we've already followed both its arrows and saved all the
|
| + // interesting states we can reach from there. The problem
|
| + // is that one of the empty-width instructions might lead
|
| + // back to the same kInstAlt (if an empty-width operator is starred),
|
| + // producing a different evaluation order depending on whether
|
| + // we keep the kInstAlt to begin with. Sigh.
|
| + // A specific case that this affects is /(^|a)+/ matching "a".
|
| + // If we don't save the kInstAlt, we will match the whole "a" (0,1)
|
| + // but in fact the correct leftmost-first match is the leading "" (0,0).
|
| + }
|
| + DCHECK_LE(n, q->size());
|
| + if (n > 0 && inst[n-1] == Mark)
|
| + n--;
|
| +
|
| + // If there are no empty-width instructions waiting to execute,
|
| + // then the extra flag bits will not be used, so there is no
|
| + // point in saving them. (Discarding them reduces the number
|
| + // of distinct states.)
|
| + if (needflags == 0)
|
| + flag &= kFlagMatch;
|
| +
|
| + // NOTE(rsc): The code above cannot do flag &= needflags,
|
| + // because if the right flags were present to pass the current
|
| + // kInstEmptyWidth instructions, new kInstEmptyWidth instructions
|
| + // might be reached that in turn need different flags.
|
| + // The only sure thing is that if there are no kInstEmptyWidth
|
| + // instructions at all, no flags will be needed.
|
| + // We could do the extra work to figure out the full set of
|
| + // possibly needed flags by exploring past the kInstEmptyWidth
|
| + // instructions, but the check above -- are any flags needed
|
| + // at all? -- handles the most common case. More fine-grained
|
| + // analysis can only be justified by measurements showing that
|
| + // too many redundant states are being allocated.
|
| +
|
| + // If there are no Insts in the list, it's a dead state,
|
| + // which is useful to signal with a special pointer so that
|
| + // the execution loop can stop early. This is only okay
|
| + // if the state is *not* a matching state.
|
| + if (n == 0 && flag == 0) {
|
| + delete[] inst;
|
| + if (DebugDFA)
|
| + fprintf(stderr, " -> DeadState\n");
|
| + return DeadState;
|
| + }
|
| +
|
| + // If we're in longest match mode, the state is a sequence of
|
| + // unordered state sets separated by Marks. Sort each set
|
| + // to canonicalize, to reduce the number of distinct sets stored.
|
| + if (kind_ == Prog::kLongestMatch) {
|
| + int* ip = inst;
|
| + int* ep = ip + n;
|
| + while (ip < ep) {
|
| + int* markp = ip;
|
| + while (markp < ep && *markp != Mark)
|
| + markp++;
|
| + sort(ip, markp);
|
| + if (markp < ep)
|
| + markp++;
|
| + ip = markp;
|
| + }
|
| + }
|
| +
|
| + // Save the needed empty-width flags in the top bits for use later.
|
| + flag |= needflags << kFlagNeedShift;
|
| +
|
| + State* state = CachedState(inst, n, flag);
|
| + delete[] inst;
|
| + return state;
|
| +}
|
| +
|
| +// Looks in the State cache for a State matching inst, ninst, flag.
|
| +// If one is found, returns it. If one is not found, allocates one,
|
| +// inserts it in the cache, and returns it.
|
| +DFA::State* DFA::CachedState(int* inst, int ninst, uint flag) {
|
| + if (DEBUG_MODE)
|
| + mutex_.AssertHeld();
|
| +
|
| + // Look in the cache for a pre-existing state.
|
| + State state = { inst, ninst, flag, NULL };
|
| + StateSet::iterator it = state_cache_.find(&state);
|
| + if (it != state_cache_.end()) {
|
| + if (DebugDFA)
|
| + fprintf(stderr, " -cached-> %s\n", DumpState(*it).c_str());
|
| + return *it;
|
| + }
|
| +
|
| + // Must have enough memory for new state.
|
| + // In addition to what we're going to allocate,
|
| + // the state cache hash table seems to incur about 32 bytes per
|
| + // State*, empirically.
|
| + const int kStateCacheOverhead = 32;
|
| + int nnext = prog_->bytemap_range() + 1; // + 1 for kByteEndText slot
|
| + int mem = sizeof(State) + nnext*sizeof(State*) + ninst*sizeof(int);
|
| + if (mem_budget_ < mem + kStateCacheOverhead) {
|
| + mem_budget_ = -1;
|
| + return NULL;
|
| + }
|
| + mem_budget_ -= mem + kStateCacheOverhead;
|
| +
|
| + // Allocate new state, along with room for next and inst.
|
| + char* space = new char[mem];
|
| + State* s = reinterpret_cast<State*>(space);
|
| + s->next_ = reinterpret_cast<State**>(s + 1);
|
| + s->inst_ = reinterpret_cast<int*>(s->next_ + nnext);
|
| + memset(s->next_, 0, nnext*sizeof s->next_[0]);
|
| + memmove(s->inst_, inst, ninst*sizeof s->inst_[0]);
|
| + s->ninst_ = ninst;
|
| + s->flag_ = flag;
|
| + if (DebugDFA)
|
| + fprintf(stderr, " -> %s\n", DumpState(s).c_str());
|
| +
|
| + // Put state in cache and return it.
|
| + state_cache_.insert(s);
|
| + return s;
|
| +}
|
| +
|
| +// Clear the cache. Must hold cache_mutex_.w or be in destructor.
|
| +void DFA::ClearCache() {
|
| + // In case state_cache_ doesn't support deleting entries
|
| + // during iteration, copy into a vector and then delete.
|
| + vector<State*> v;
|
| + v.reserve(state_cache_.size());
|
| + for (StateSet::iterator it = state_cache_.begin();
|
| + it != state_cache_.end(); ++it)
|
| + v.push_back(*it);
|
| + state_cache_.clear();
|
| + for (int i = 0; i < v.size(); i++)
|
| + delete[] reinterpret_cast<const char*>(v[i]);
|
| +}
|
| +
|
| +// Copies insts in state s to the work queue q.
|
| +void DFA::StateToWorkq(State* s, Workq* q) {
|
| + q->clear();
|
| + for (int i = 0; i < s->ninst_; i++) {
|
| + if (s->inst_[i] == Mark)
|
| + q->mark();
|
| + else
|
| + q->insert_new(s->inst_[i]);
|
| + }
|
| +}
|
| +
|
| +// Adds ip to the work queue, following empty arrows according to flag
|
| +// and expanding kInstAlt instructions (two-target gotos).
|
| +void DFA::AddToQueue(Workq* q, int id, uint flag) {
|
| +
|
| + // Use astack_ to hold our stack of states yet to process.
|
| + // It is sized to have room for nastack_ == 2*prog->size() + nmark
|
| + // instructions, which is enough: each instruction can be
|
| + // processed by the switch below only once, and the processing
|
| + // pushes at most two instructions plus maybe a mark.
|
| + // (If we're using marks, nmark == prog->size(); otherwise nmark == 0.)
|
| + int* stk = astack_;
|
| + int nstk = 0;
|
| +
|
| + stk[nstk++] = id;
|
| + while (nstk > 0) {
|
| + DCHECK_LE(nstk, nastack_);
|
| + id = stk[--nstk];
|
| +
|
| + if (id == Mark) {
|
| + q->mark();
|
| + continue;
|
| + }
|
| +
|
| + if (id == 0)
|
| + continue;
|
| +
|
| + // If ip is already on the queue, nothing to do.
|
| + // Otherwise add it. We don't actually keep all the ones
|
| + // that get added -- for example, kInstAlt is ignored
|
| + // when on a work queue -- but adding all ip's here
|
| + // increases the likelihood of q->contains(id),
|
| + // reducing the amount of duplicated work.
|
| + if (q->contains(id))
|
| + continue;
|
| + q->insert_new(id);
|
| +
|
| + // Process instruction.
|
| + Prog::Inst* ip = prog_->inst(id);
|
| + switch (ip->opcode()) {
|
| + case kInstFail: // can't happen: discarded above
|
| + break;
|
| +
|
| + case kInstByteRange: // just save these on the queue
|
| + case kInstMatch:
|
| + break;
|
| +
|
| + case kInstCapture: // DFA treats captures as no-ops.
|
| + case kInstNop:
|
| + stk[nstk++] = ip->out();
|
| + break;
|
| +
|
| + case kInstAlt: // two choices: expand both, in order
|
| + case kInstAltMatch:
|
| + // Want to visit out then out1, so push on stack in reverse order.
|
| + // This instruction is the [00-FF]* loop at the beginning of
|
| + // a leftmost-longest unanchored search, separate out from out1
|
| + // with a Mark, so that out1's threads (which will start farther
|
| + // to the right in the string being searched) are lower priority
|
| + // than the current ones.
|
| + stk[nstk++] = ip->out1();
|
| + if (q->maxmark() > 0 &&
|
| + id == prog_->start_unanchored() && id != prog_->start())
|
| + stk[nstk++] = Mark;
|
| + stk[nstk++] = ip->out();
|
| + break;
|
| +
|
| + case kInstEmptyWidth:
|
| + if ((ip->empty() & flag) == ip->empty())
|
| + stk[nstk++] = ip->out();
|
| + break;
|
| + }
|
| + }
|
| +}
|
| +
|
| +// Running of work queues. In the work queue, order matters:
|
| +// the queue is sorted in priority order. If instruction i comes before j,
|
| +// then the instructions that i produces during the run must come before
|
| +// the ones that j produces. In order to keep this invariant, all the
|
| +// work queue runners have to take an old queue to process and then
|
| +// also a new queue to fill in. It's not acceptable to add to the end of
|
| +// an existing queue, because new instructions will not end up in the
|
| +// correct position.
|
| +
|
| +// Runs the work queue, processing the empty strings indicated by flag.
|
| +// For example, flag == kEmptyBeginLine|kEmptyEndLine means to match
|
| +// both ^ and $. It is important that callers pass all flags at once:
|
| +// processing both ^ and $ is not the same as first processing only ^
|
| +// and then processing only $. Doing the two-step sequence won't match
|
| +// ^$^$^$ but processing ^ and $ simultaneously will (and is the behavior
|
| +// exhibited by existing implementations).
|
| +void DFA::RunWorkqOnEmptyString(Workq* oldq, Workq* newq, uint flag) {
|
| + newq->clear();
|
| + for (Workq::iterator i = oldq->begin(); i != oldq->end(); ++i) {
|
| + if (oldq->is_mark(*i))
|
| + AddToQueue(newq, Mark, flag);
|
| + else
|
| + AddToQueue(newq, *i, flag);
|
| + }
|
| +}
|
| +
|
| +// Runs the work queue, processing the single byte c followed by any empty
|
| +// strings indicated by flag. For example, c == 'a' and flag == kEmptyEndLine,
|
| +// means to match c$. Sets the bool *ismatch to true if the end of the
|
| +// regular expression program has been reached (the regexp has matched).
|
| +void DFA::RunWorkqOnByte(Workq* oldq, Workq* newq,
|
| + int c, uint flag, bool* ismatch,
|
| + Prog::MatchKind kind,
|
| + int new_byte_loop) {
|
| + if (DEBUG_MODE)
|
| + mutex_.AssertHeld();
|
| +
|
| + newq->clear();
|
| + for (Workq::iterator i = oldq->begin(); i != oldq->end(); ++i) {
|
| + if (oldq->is_mark(*i)) {
|
| + if (*ismatch)
|
| + return;
|
| + newq->mark();
|
| + continue;
|
| + }
|
| + int id = *i;
|
| + Prog::Inst* ip = prog_->inst(id);
|
| + switch (ip->opcode()) {
|
| + case kInstFail: // never succeeds
|
| + case kInstCapture: // already followed
|
| + case kInstNop: // already followed
|
| + case kInstAlt: // already followed
|
| + case kInstAltMatch: // already followed
|
| + case kInstEmptyWidth: // already followed
|
| + break;
|
| +
|
| + case kInstByteRange: // can follow if c is in range
|
| + if (ip->Matches(c))
|
| + AddToQueue(newq, ip->out(), flag);
|
| + break;
|
| +
|
| + case kInstMatch:
|
| + if (prog_->anchor_end() && c != kByteEndText)
|
| + break;
|
| + *ismatch = true;
|
| + if (kind == Prog::kFirstMatch) {
|
| + // Can stop processing work queue since we found a match.
|
| + return;
|
| + }
|
| + break;
|
| + }
|
| + }
|
| +
|
| + if (DebugDFA)
|
| + fprintf(stderr, "%s on %d[%#x] -> %s [%d]\n", DumpWorkq(oldq).c_str(),
|
| + c, flag, DumpWorkq(newq).c_str(), *ismatch);
|
| +}
|
| +
|
| +// Processes input byte c in state, returning new state.
|
| +// Caller does not hold mutex.
|
| +DFA::State* DFA::RunStateOnByteUnlocked(State* state, int c) {
|
| + // Keep only one RunStateOnByte going
|
| + // even if the DFA is being run by multiple threads.
|
| + MutexLock l(&mutex_);
|
| + return RunStateOnByte(state, c);
|
| +}
|
| +
|
| +// Processes input byte c in state, returning new state.
|
| +DFA::State* DFA::RunStateOnByte(State* state, int c) {
|
| + if (DEBUG_MODE)
|
| + mutex_.AssertHeld();
|
| + if (state <= SpecialStateMax) {
|
| + if (state == FullMatchState) {
|
| + // It is convenient for routines like PossibleMatchRange
|
| + // if we implement RunStateOnByte for FullMatchState:
|
| + // once you get into this state you never get out,
|
| + // so it's pretty easy.
|
| + return FullMatchState;
|
| + }
|
| + if (state == DeadState) {
|
| + LOG(DFATAL) << "DeadState in RunStateOnByte";
|
| + return NULL;
|
| + }
|
| + if (state == NULL) {
|
| + LOG(DFATAL) << "NULL state in RunStateOnByte";
|
| + return NULL;
|
| + }
|
| + LOG(DFATAL) << "Unexpected special state in RunStateOnByte";
|
| + return NULL;
|
| + }
|
| +
|
| + // If someone else already computed this, return it.
|
| + MaybeReadMemoryBarrier(); // On alpha we need to ensure read ordering
|
| + if (state->next_[ByteMap(c)])
|
| + return state->next_[ByteMap(c)];
|
| +
|
| + // Convert state into Workq.
|
| + StateToWorkq(state, q0_);
|
| +
|
| + // Flags marking the kinds of empty-width things (^ $ etc)
|
| + // around this byte. Before the byte we have the flags recorded
|
| + // in the State structure itself. After the byte we have
|
| + // nothing yet (but that will change: read on).
|
| + uint needflag = state->flag_ >> kFlagNeedShift;
|
| + uint beforeflag = state->flag_ & kFlagEmptyMask;
|
| + uint oldbeforeflag = beforeflag;
|
| + uint afterflag = 0;
|
| +
|
| + if (c == '\n') {
|
| + // Insert implicit $ and ^ around \n
|
| + beforeflag |= kEmptyEndLine;
|
| + afterflag |= kEmptyBeginLine;
|
| + }
|
| +
|
| + if (c == kByteEndText) {
|
| + // Insert implicit $ and \z before the fake "end text" byte.
|
| + beforeflag |= kEmptyEndLine | kEmptyEndText;
|
| + }
|
| +
|
| + // The state flag kFlagLastWord says whether the last
|
| + // byte processed was a word character. Use that info to
|
| + // insert empty-width (non-)word boundaries.
|
| + bool islastword = state->flag_ & kFlagLastWord;
|
| + bool isword = (c != kByteEndText && Prog::IsWordChar(c));
|
| + if (isword == islastword)
|
| + beforeflag |= kEmptyNonWordBoundary;
|
| + else
|
| + beforeflag |= kEmptyWordBoundary;
|
| +
|
| + // Okay, finally ready to run.
|
| + // Only useful to rerun on empty string if there are new, useful flags.
|
| + if (beforeflag & ~oldbeforeflag & needflag) {
|
| + RunWorkqOnEmptyString(q0_, q1_, beforeflag);
|
| + swap(q0_, q1_);
|
| + }
|
| + bool ismatch = false;
|
| + RunWorkqOnByte(q0_, q1_, c, afterflag, &ismatch, kind_, start_unanchored_);
|
| + swap(q0_, q1_);
|
| +
|
| + // Save afterflag along with ismatch and isword in new state.
|
| + uint flag = afterflag;
|
| + if (ismatch)
|
| + flag |= kFlagMatch;
|
| + if (isword)
|
| + flag |= kFlagLastWord;
|
| +
|
| + State* ns = WorkqToCachedState(q0_, flag);
|
| +
|
| + // Write barrier before updating state->next_ so that the
|
| + // main search loop can proceed without any locking, for speed.
|
| + // (Otherwise it would need one mutex operation per input byte.)
|
| + // The annotations below tell race detectors that:
|
| + // a) the access to next_ should be ignored,
|
| + // b) 'ns' is properly published.
|
| + WriteMemoryBarrier(); // Flush ns before linking to it.
|
| + ANNOTATE_PUBLISH_MEMORY_RANGE(ns, sizeof(*ns));
|
| +
|
| + ANNOTATE_IGNORE_WRITES_BEGIN();
|
| + state->next_[ByteMap(c)] = ns;
|
| + ANNOTATE_IGNORE_WRITES_END();
|
| + return ns;
|
| +}
|
| +
|
| +
|
| +//////////////////////////////////////////////////////////////////////
|
| +// DFA cache reset.
|
| +
|
| +// Reader-writer lock helper.
|
| +//
|
| +// The DFA uses a reader-writer mutex to protect the state graph itself.
|
| +// Traversing the state graph requires holding the mutex for reading,
|
| +// and discarding the state graph and starting over requires holding the
|
| +// lock for writing. If a search needs to expand the graph but is out
|
| +// of memory, it will need to drop its read lock and then acquire the
|
| +// write lock. Since it cannot then atomically downgrade from write lock
|
| +// to read lock, it runs the rest of the search holding the write lock.
|
| +// (This probably helps avoid repeated contention, but really the decision
|
| +// is forced by the Mutex interface.) It's a bit complicated to keep
|
| +// track of whether the lock is held for reading or writing and thread
|
| +// that through the search, so instead we encapsulate it in the RWLocker
|
| +// and pass that around.
|
| +
|
| +class DFA::RWLocker {
|
| + public:
|
| + explicit RWLocker(Mutex* mu);
|
| + ~RWLocker();
|
| +
|
| + // If the lock is only held for reading right now,
|
| + // drop the read lock and re-acquire for writing.
|
| + // Subsequent calls to LockForWriting are no-ops.
|
| + // Notice that the lock is *released* temporarily.
|
| + void LockForWriting();
|
| +
|
| + // Returns whether the lock is already held for writing.
|
| + bool IsLockedForWriting() {
|
| + return writing_;
|
| + }
|
| +
|
| + private:
|
| + Mutex* mu_;
|
| + bool writing_;
|
| +
|
| + DISALLOW_EVIL_CONSTRUCTORS(RWLocker);
|
| +};
|
| +
|
| +DFA::RWLocker::RWLocker(Mutex* mu)
|
| + : mu_(mu), writing_(false) {
|
| +
|
| + mu_->ReaderLock();
|
| +}
|
| +
|
| +// This function is marked as NO_THREAD_SAFETY_ANALYSIS because the annotations
|
| +// does not support lock upgrade.
|
| +void DFA::RWLocker::LockForWriting() NO_THREAD_SAFETY_ANALYSIS {
|
| + if (!writing_) {
|
| + mu_->ReaderUnlock();
|
| + mu_->Lock();
|
| + writing_ = true;
|
| + }
|
| +}
|
| +
|
| +DFA::RWLocker::~RWLocker() {
|
| + if (writing_)
|
| + mu_->WriterUnlock();
|
| + else
|
| + mu_->ReaderUnlock();
|
| +}
|
| +
|
| +
|
| +// When the DFA's State cache fills, we discard all the states in the
|
| +// cache and start over. Many threads can be using and adding to the
|
| +// cache at the same time, so we synchronize using the cache_mutex_
|
| +// to keep from stepping on other threads. Specifically, all the
|
| +// threads using the current cache hold cache_mutex_ for reading.
|
| +// When a thread decides to flush the cache, it drops cache_mutex_
|
| +// and then re-acquires it for writing. That ensures there are no
|
| +// other threads accessing the cache anymore. The rest of the search
|
| +// runs holding cache_mutex_ for writing, avoiding any contention
|
| +// with or cache pollution caused by other threads.
|
| +
|
| +void DFA::ResetCache(RWLocker* cache_lock) {
|
| + // Re-acquire the cache_mutex_ for writing (exclusive use).
|
| + bool was_writing = cache_lock->IsLockedForWriting();
|
| + cache_lock->LockForWriting();
|
| +
|
| + // If we already held cache_mutex_ for writing, it means
|
| + // this invocation of Search() has already reset the
|
| + // cache once already. That's a pretty clear indication
|
| + // that the cache is too small. Warn about that, once.
|
| + // TODO(rsc): Only warn if state_cache_.size() < some threshold.
|
| + if (was_writing && !cache_warned_) {
|
| + LOG(INFO) << "DFA memory cache could be too small: "
|
| + << "only room for " << state_cache_.size() << " states.";
|
| + cache_warned_ = true;
|
| + }
|
| +
|
| + // Clear the cache, reset the memory budget.
|
| + for (int i = 0; i < kMaxStart; i++) {
|
| + start_[i].start = NULL;
|
| + start_[i].firstbyte = kFbUnknown;
|
| + }
|
| + ClearCache();
|
| + mem_budget_ = state_budget_;
|
| +}
|
| +
|
| +// Typically, a couple States do need to be preserved across a cache
|
| +// reset, like the State at the current point in the search.
|
| +// The StateSaver class helps keep States across cache resets.
|
| +// It makes a copy of the state's guts outside the cache (before the reset)
|
| +// and then can be asked, after the reset, to recreate the State
|
| +// in the new cache. For example, in a DFA method ("this" is a DFA):
|
| +//
|
| +// StateSaver saver(this, s);
|
| +// ResetCache(cache_lock);
|
| +// s = saver.Restore();
|
| +//
|
| +// The saver should always have room in the cache to re-create the state,
|
| +// because resetting the cache locks out all other threads, and the cache
|
| +// is known to have room for at least a couple states (otherwise the DFA
|
| +// constructor fails).
|
| +
|
| +class DFA::StateSaver {
|
| + public:
|
| + explicit StateSaver(DFA* dfa, State* state);
|
| + ~StateSaver();
|
| +
|
| + // Recreates and returns a state equivalent to the
|
| + // original state passed to the constructor.
|
| + // Returns NULL if the cache has filled, but
|
| + // since the DFA guarantees to have room in the cache
|
| + // for a couple states, should never return NULL
|
| + // if used right after ResetCache.
|
| + State* Restore();
|
| +
|
| + private:
|
| + DFA* dfa_; // the DFA to use
|
| + int* inst_; // saved info from State
|
| + int ninst_;
|
| + uint flag_;
|
| + bool is_special_; // whether original state was special
|
| + State* special_; // if is_special_, the original state
|
| +
|
| + DISALLOW_EVIL_CONSTRUCTORS(StateSaver);
|
| +};
|
| +
|
| +DFA::StateSaver::StateSaver(DFA* dfa, State* state) {
|
| + dfa_ = dfa;
|
| + if (state <= SpecialStateMax) {
|
| + inst_ = NULL;
|
| + ninst_ = 0;
|
| + flag_ = 0;
|
| + is_special_ = true;
|
| + special_ = state;
|
| + return;
|
| + }
|
| + is_special_ = false;
|
| + special_ = NULL;
|
| + flag_ = state->flag_;
|
| + ninst_ = state->ninst_;
|
| + inst_ = new int[ninst_];
|
| + memmove(inst_, state->inst_, ninst_*sizeof inst_[0]);
|
| +}
|
| +
|
| +DFA::StateSaver::~StateSaver() {
|
| + if (!is_special_)
|
| + delete[] inst_;
|
| +}
|
| +
|
| +DFA::State* DFA::StateSaver::Restore() {
|
| + if (is_special_)
|
| + return special_;
|
| + MutexLock l(&dfa_->mutex_);
|
| + State* s = dfa_->CachedState(inst_, ninst_, flag_);
|
| + if (s == NULL)
|
| + LOG(DFATAL) << "StateSaver failed to restore state.";
|
| + return s;
|
| +}
|
| +
|
| +
|
| +//////////////////////////////////////////////////////////////////////
|
| +//
|
| +// DFA execution.
|
| +//
|
| +// The basic search loop is easy: start in a state s and then for each
|
| +// byte c in the input, s = s->next[c].
|
| +//
|
| +// This simple description omits a few efficiency-driven complications.
|
| +//
|
| +// First, the State graph is constructed incrementally: it is possible
|
| +// that s->next[c] is null, indicating that that state has not been
|
| +// fully explored. In this case, RunStateOnByte must be invoked to
|
| +// determine the next state, which is cached in s->next[c] to save
|
| +// future effort. An alternative reason for s->next[c] to be null is
|
| +// that the DFA has reached a so-called "dead state", in which any match
|
| +// is no longer possible. In this case RunStateOnByte will return NULL
|
| +// and the processing of the string can stop early.
|
| +//
|
| +// Second, a 256-element pointer array for s->next_ makes each State
|
| +// quite large (2kB on 64-bit machines). Instead, dfa->bytemap_[]
|
| +// maps from bytes to "byte classes" and then next_ only needs to have
|
| +// as many pointers as there are byte classes. A byte class is simply a
|
| +// range of bytes that the regexp never distinguishes between.
|
| +// A regexp looking for a[abc] would have four byte ranges -- 0 to 'a'-1,
|
| +// 'a', 'b' to 'c', and 'c' to 0xFF. The bytemap slows us a little bit
|
| +// but in exchange we typically cut the size of a State (and thus our
|
| +// memory footprint) by about 5-10x. The comments still refer to
|
| +// s->next[c] for simplicity, but code should refer to s->next_[bytemap_[c]].
|
| +//
|
| +// Third, it is common for a DFA for an unanchored match to begin in a
|
| +// state in which only one particular byte value can take the DFA to a
|
| +// different state. That is, s->next[c] != s for only one c. In this
|
| +// situation, the DFA can do better than executing the simple loop.
|
| +// Instead, it can call memchr to search very quickly for the byte c.
|
| +// Whether the start state has this property is determined during a
|
| +// pre-compilation pass, and if so, the byte b is passed to the search
|
| +// loop as the "firstbyte" argument, along with a boolean "have_firstbyte".
|
| +//
|
| +// Fourth, the desired behavior is to search for the leftmost-best match
|
| +// (approximately, the same one that Perl would find), which is not
|
| +// necessarily the match ending earliest in the string. Each time a
|
| +// match is found, it must be noted, but the DFA must continue on in
|
| +// hope of finding a higher-priority match. In some cases, the caller only
|
| +// cares whether there is any match at all, not which one is found.
|
| +// The "want_earliest_match" flag causes the search to stop at the first
|
| +// match found.
|
| +//
|
| +// Fifth, one algorithm that uses the DFA needs it to run over the
|
| +// input string backward, beginning at the end and ending at the beginning.
|
| +// Passing false for the "run_forward" flag causes the DFA to run backward.
|
| +//
|
| +// The checks for these last three cases, which in a naive implementation
|
| +// would be performed once per input byte, slow the general loop enough
|
| +// to merit specialized versions of the search loop for each of the
|
| +// eight possible settings of the three booleans. Rather than write
|
| +// eight different functions, we write one general implementation and then
|
| +// inline it to create the specialized ones.
|
| +//
|
| +// Note that matches are delayed by one byte, to make it easier to
|
| +// accomodate match conditions depending on the next input byte (like $ and \b).
|
| +// When s->next[c]->IsMatch(), it means that there is a match ending just
|
| +// *before* byte c.
|
| +
|
| +// The generic search loop. Searches text for a match, returning
|
| +// the pointer to the end of the chosen match, or NULL if no match.
|
| +// The bools are equal to the same-named variables in params, but
|
| +// making them function arguments lets the inliner specialize
|
| +// this function to each combination (see two paragraphs above).
|
| +inline bool DFA::InlinedSearchLoop(SearchParams* params,
|
| + bool have_firstbyte,
|
| + bool want_earliest_match,
|
| + bool run_forward) {
|
| + State* start = params->start;
|
| + const uint8* bp = BytePtr(params->text.begin()); // start of text
|
| + const uint8* p = bp; // text scanning point
|
| + const uint8* ep = BytePtr(params->text.end()); // end of text
|
| + const uint8* resetp = NULL; // p at last cache reset
|
| + if (!run_forward)
|
| + swap(p, ep);
|
| +
|
| + const uint8* bytemap = prog_->bytemap();
|
| + const uint8* lastmatch = NULL; // most recent matching position in text
|
| + bool matched = false;
|
| + State* s = start;
|
| +
|
| + if (s->IsMatch()) {
|
| + matched = true;
|
| + lastmatch = p;
|
| + if (want_earliest_match) {
|
| + params->ep = reinterpret_cast<const char*>(lastmatch);
|
| + return true;
|
| + }
|
| + }
|
| +
|
| + while (p != ep) {
|
| + if (DebugDFA)
|
| + fprintf(stderr, "@%d: %s\n", static_cast<int>(p - bp),
|
| + DumpState(s).c_str());
|
| + if (have_firstbyte && s == start) {
|
| + // In start state, only way out is to find firstbyte,
|
| + // so use optimized assembly in memchr to skip ahead.
|
| + // If firstbyte isn't found, we can skip to the end
|
| + // of the string.
|
| + if (run_forward) {
|
| + if ((p = BytePtr(memchr(p, params->firstbyte, ep - p))) == NULL) {
|
| + p = ep;
|
| + break;
|
| + }
|
| + } else {
|
| + if ((p = BytePtr(memrchr(ep, params->firstbyte, p - ep))) == NULL) {
|
| + p = ep;
|
| + break;
|
| + }
|
| + p++;
|
| + }
|
| + }
|
| +
|
| + int c;
|
| + if (run_forward)
|
| + c = *p++;
|
| + else
|
| + c = *--p;
|
| +
|
| + // Note that multiple threads might be consulting
|
| + // s->next_[bytemap[c]] simultaneously.
|
| + // RunStateOnByte takes care of the appropriate locking,
|
| + // including a memory barrier so that the unlocked access
|
| + // (sometimes known as "double-checked locking") is safe.
|
| + // The alternative would be either one DFA per thread
|
| + // or one mutex operation per input byte.
|
| + //
|
| + // ns == DeadState means the state is known to be dead
|
| + // (no more matches are possible).
|
| + // ns == NULL means the state has not yet been computed
|
| + // (need to call RunStateOnByteUnlocked).
|
| + // RunStateOnByte returns ns == NULL if it is out of memory.
|
| + // ns == FullMatchState means the rest of the string matches.
|
| + //
|
| + // Okay to use bytemap[] not ByteMap() here, because
|
| + // c is known to be an actual byte and not kByteEndText.
|
| +
|
| + MaybeReadMemoryBarrier(); // On alpha we need to ensure read ordering
|
| + State* ns = s->next_[bytemap[c]];
|
| + if (ns == NULL) {
|
| + ns = RunStateOnByteUnlocked(s, c);
|
| + if (ns == NULL) {
|
| + // After we reset the cache, we hold cache_mutex exclusively,
|
| + // so if resetp != NULL, it means we filled the DFA state
|
| + // cache with this search alone (without any other threads).
|
| + // Benchmarks show that doing a state computation on every
|
| + // byte runs at about 0.2 MB/s, while the NFA (nfa.cc) can do the
|
| + // same at about 2 MB/s. Unless we're processing an average
|
| + // of 10 bytes per state computation, fail so that RE2 can
|
| + // fall back to the NFA.
|
| + if (FLAGS_re2_dfa_bail_when_slow && resetp != NULL &&
|
| + (p - resetp) < 10*state_cache_.size()) {
|
| + params->failed = true;
|
| + return false;
|
| + }
|
| + resetp = p;
|
| +
|
| + // Prepare to save start and s across the reset.
|
| + StateSaver save_start(this, start);
|
| + StateSaver save_s(this, s);
|
| +
|
| + // Discard all the States in the cache.
|
| + ResetCache(params->cache_lock);
|
| +
|
| + // Restore start and s so we can continue.
|
| + if ((start = save_start.Restore()) == NULL ||
|
| + (s = save_s.Restore()) == NULL) {
|
| + // Restore already did LOG(DFATAL).
|
| + params->failed = true;
|
| + return false;
|
| + }
|
| + ns = RunStateOnByteUnlocked(s, c);
|
| + if (ns == NULL) {
|
| + LOG(DFATAL) << "RunStateOnByteUnlocked failed after ResetCache";
|
| + params->failed = true;
|
| + return false;
|
| + }
|
| + }
|
| + }
|
| + if (ns <= SpecialStateMax) {
|
| + if (ns == DeadState) {
|
| + params->ep = reinterpret_cast<const char*>(lastmatch);
|
| + return matched;
|
| + }
|
| + // FullMatchState
|
| + params->ep = reinterpret_cast<const char*>(ep);
|
| + return true;
|
| + }
|
| + s = ns;
|
| +
|
| + if (s->IsMatch()) {
|
| + matched = true;
|
| + // The DFA notices the match one byte late,
|
| + // so adjust p before using it in the match.
|
| + if (run_forward)
|
| + lastmatch = p - 1;
|
| + else
|
| + lastmatch = p + 1;
|
| + if (DebugDFA)
|
| + fprintf(stderr, "match @%d! [%s]\n",
|
| + static_cast<int>(lastmatch - bp),
|
| + DumpState(s).c_str());
|
| +
|
| + if (want_earliest_match) {
|
| + params->ep = reinterpret_cast<const char*>(lastmatch);
|
| + return true;
|
| + }
|
| + }
|
| + }
|
| +
|
| + // Peek in state to see if a match is coming up.
|
| + if (params->matches && kind_ == Prog::kManyMatch) {
|
| + vector<int>* v = params->matches;
|
| + v->clear();
|
| + if (s > SpecialStateMax) {
|
| + for (int i = 0; i < s->ninst_; i++) {
|
| + Prog::Inst* ip = prog_->inst(s->inst_[i]);
|
| + if (ip->opcode() == kInstMatch)
|
| + v->push_back(ip->match_id());
|
| + }
|
| + }
|
| + }
|
| +
|
| +
|
| + // Process one more byte to see if it triggers a match.
|
| + // (Remember, matches are delayed one byte.)
|
| + int lastbyte;
|
| + if (run_forward) {
|
| + if (params->text.end() == params->context.end())
|
| + lastbyte = kByteEndText;
|
| + else
|
| + lastbyte = params->text.end()[0] & 0xFF;
|
| + } else {
|
| + if (params->text.begin() == params->context.begin())
|
| + lastbyte = kByteEndText;
|
| + else
|
| + lastbyte = params->text.begin()[-1] & 0xFF;
|
| + }
|
| +
|
| + MaybeReadMemoryBarrier(); // On alpha we need to ensure read ordering
|
| + State* ns = s->next_[ByteMap(lastbyte)];
|
| + if (ns == NULL) {
|
| + ns = RunStateOnByteUnlocked(s, lastbyte);
|
| + if (ns == NULL) {
|
| + StateSaver save_s(this, s);
|
| + ResetCache(params->cache_lock);
|
| + if ((s = save_s.Restore()) == NULL) {
|
| + params->failed = true;
|
| + return false;
|
| + }
|
| + ns = RunStateOnByteUnlocked(s, lastbyte);
|
| + if (ns == NULL) {
|
| + LOG(DFATAL) << "RunStateOnByteUnlocked failed after Reset";
|
| + params->failed = true;
|
| + return false;
|
| + }
|
| + }
|
| + }
|
| + s = ns;
|
| + if (DebugDFA)
|
| + fprintf(stderr, "@_: %s\n", DumpState(s).c_str());
|
| + if (s == FullMatchState) {
|
| + params->ep = reinterpret_cast<const char*>(ep);
|
| + return true;
|
| + }
|
| + if (s > SpecialStateMax && s->IsMatch()) {
|
| + matched = true;
|
| + lastmatch = p;
|
| + if (DebugDFA)
|
| + fprintf(stderr, "match @%d! [%s]\n", static_cast<int>(lastmatch - bp),
|
| + DumpState(s).c_str());
|
| + }
|
| + params->ep = reinterpret_cast<const char*>(lastmatch);
|
| + return matched;
|
| +}
|
| +
|
| +// Inline specializations of the general loop.
|
| +bool DFA::SearchFFF(SearchParams* params) {
|
| + return InlinedSearchLoop(params, 0, 0, 0);
|
| +}
|
| +bool DFA::SearchFFT(SearchParams* params) {
|
| + return InlinedSearchLoop(params, 0, 0, 1);
|
| +}
|
| +bool DFA::SearchFTF(SearchParams* params) {
|
| + return InlinedSearchLoop(params, 0, 1, 0);
|
| +}
|
| +bool DFA::SearchFTT(SearchParams* params) {
|
| + return InlinedSearchLoop(params, 0, 1, 1);
|
| +}
|
| +bool DFA::SearchTFF(SearchParams* params) {
|
| + return InlinedSearchLoop(params, 1, 0, 0);
|
| +}
|
| +bool DFA::SearchTFT(SearchParams* params) {
|
| + return InlinedSearchLoop(params, 1, 0, 1);
|
| +}
|
| +bool DFA::SearchTTF(SearchParams* params) {
|
| + return InlinedSearchLoop(params, 1, 1, 0);
|
| +}
|
| +bool DFA::SearchTTT(SearchParams* params) {
|
| + return InlinedSearchLoop(params, 1, 1, 1);
|
| +}
|
| +
|
| +// For debugging, calls the general code directly.
|
| +bool DFA::SlowSearchLoop(SearchParams* params) {
|
| + return InlinedSearchLoop(params,
|
| + params->firstbyte >= 0,
|
| + params->want_earliest_match,
|
| + params->run_forward);
|
| +}
|
| +
|
| +// For performance, calls the appropriate specialized version
|
| +// of InlinedSearchLoop.
|
| +bool DFA::FastSearchLoop(SearchParams* params) {
|
| + // Because the methods are private, the Searches array
|
| + // cannot be declared at top level.
|
| + static bool (DFA::*Searches[])(SearchParams*) = {
|
| + &DFA::SearchFFF,
|
| + &DFA::SearchFFT,
|
| + &DFA::SearchFTF,
|
| + &DFA::SearchFTT,
|
| + &DFA::SearchTFF,
|
| + &DFA::SearchTFT,
|
| + &DFA::SearchTTF,
|
| + &DFA::SearchTTT,
|
| + };
|
| +
|
| + bool have_firstbyte = (params->firstbyte >= 0);
|
| + int index = 4 * have_firstbyte +
|
| + 2 * params->want_earliest_match +
|
| + 1 * params->run_forward;
|
| + return (this->*Searches[index])(params);
|
| +}
|
| +
|
| +
|
| +// The discussion of DFA execution above ignored the question of how
|
| +// to determine the initial state for the search loop. There are two
|
| +// factors that influence the choice of start state.
|
| +//
|
| +// The first factor is whether the search is anchored or not.
|
| +// The regexp program (Prog*) itself has
|
| +// two different entry points: one for anchored searches and one for
|
| +// unanchored searches. (The unanchored version starts with a leading ".*?"
|
| +// and then jumps to the anchored one.)
|
| +//
|
| +// The second factor is where text appears in the larger context, which
|
| +// determines which empty-string operators can be matched at the beginning
|
| +// of execution. If text is at the very beginning of context, \A and ^ match.
|
| +// Otherwise if text is at the beginning of a line, then ^ matches.
|
| +// Otherwise it matters whether the character before text is a word character
|
| +// or a non-word character.
|
| +//
|
| +// The two cases (unanchored vs not) and four cases (empty-string flags)
|
| +// combine to make the eight cases recorded in the DFA's begin_text_[2],
|
| +// begin_line_[2], after_wordchar_[2], and after_nonwordchar_[2] cached
|
| +// StartInfos. The start state for each is filled in the first time it
|
| +// is used for an actual search.
|
| +
|
| +// Examines text, context, and anchored to determine the right start
|
| +// state for the DFA search loop. Fills in params and returns true on success.
|
| +// Returns false on failure.
|
| +bool DFA::AnalyzeSearch(SearchParams* params) {
|
| + const StringPiece& text = params->text;
|
| + const StringPiece& context = params->context;
|
| +
|
| + // Sanity check: make sure that text lies within context.
|
| + if (text.begin() < context.begin() || text.end() > context.end()) {
|
| + LOG(DFATAL) << "Text is not inside context.";
|
| + params->start = DeadState;
|
| + return true;
|
| + }
|
| +
|
| + // Determine correct search type.
|
| + int start;
|
| + uint flags;
|
| + if (params->run_forward) {
|
| + if (text.begin() == context.begin()) {
|
| + start = kStartBeginText;
|
| + flags = kEmptyBeginText|kEmptyBeginLine;
|
| + } else if (text.begin()[-1] == '\n') {
|
| + start = kStartBeginLine;
|
| + flags = kEmptyBeginLine;
|
| + } else if (Prog::IsWordChar(text.begin()[-1] & 0xFF)) {
|
| + start = kStartAfterWordChar;
|
| + flags = kFlagLastWord;
|
| + } else {
|
| + start = kStartAfterNonWordChar;
|
| + flags = 0;
|
| + }
|
| + } else {
|
| + if (text.end() == context.end()) {
|
| + start = kStartBeginText;
|
| + flags = kEmptyBeginText|kEmptyBeginLine;
|
| + } else if (text.end()[0] == '\n') {
|
| + start = kStartBeginLine;
|
| + flags = kEmptyBeginLine;
|
| + } else if (Prog::IsWordChar(text.end()[0] & 0xFF)) {
|
| + start = kStartAfterWordChar;
|
| + flags = kFlagLastWord;
|
| + } else {
|
| + start = kStartAfterNonWordChar;
|
| + flags = 0;
|
| + }
|
| + }
|
| + if (params->anchored || prog_->anchor_start())
|
| + start |= kStartAnchored;
|
| + StartInfo* info = &start_[start];
|
| +
|
| + // Try once without cache_lock for writing.
|
| + // Try again after resetting the cache
|
| + // (ResetCache will relock cache_lock for writing).
|
| + if (!AnalyzeSearchHelper(params, info, flags)) {
|
| + ResetCache(params->cache_lock);
|
| + if (!AnalyzeSearchHelper(params, info, flags)) {
|
| + LOG(DFATAL) << "Failed to analyze start state.";
|
| + params->failed = true;
|
| + return false;
|
| + }
|
| + }
|
| +
|
| + if (DebugDFA)
|
| + fprintf(stderr, "anchored=%d fwd=%d flags=%#x state=%s firstbyte=%d\n",
|
| + params->anchored, params->run_forward, flags,
|
| + DumpState(info->start).c_str(), info->firstbyte);
|
| +
|
| + params->start = info->start;
|
| + params->firstbyte = info->firstbyte;
|
| +
|
| + return true;
|
| +}
|
| +
|
| +// Fills in info if needed. Returns true on success, false on failure.
|
| +bool DFA::AnalyzeSearchHelper(SearchParams* params, StartInfo* info,
|
| + uint flags) {
|
| + // Quick check; okay because of memory barriers below.
|
| + if (info->firstbyte != kFbUnknown)
|
| + return true;
|
| +
|
| + MutexLock l(&mutex_);
|
| + if (info->firstbyte != kFbUnknown)
|
| + return true;
|
| +
|
| + q0_->clear();
|
| + AddToQueue(q0_,
|
| + params->anchored ? prog_->start() : prog_->start_unanchored(),
|
| + flags);
|
| + info->start = WorkqToCachedState(q0_, flags);
|
| + if (info->start == NULL)
|
| + return false;
|
| +
|
| + if (info->start == DeadState) {
|
| + WriteMemoryBarrier(); // Synchronize with "quick check" above.
|
| + info->firstbyte = kFbNone;
|
| + return true;
|
| + }
|
| +
|
| + if (info->start == FullMatchState) {
|
| + WriteMemoryBarrier(); // Synchronize with "quick check" above.
|
| + info->firstbyte = kFbNone; // will be ignored
|
| + return true;
|
| + }
|
| +
|
| + // Compute info->firstbyte by running state on all
|
| + // possible byte values, looking for a single one that
|
| + // leads to a different state.
|
| + int firstbyte = kFbNone;
|
| + for (int i = 0; i < 256; i++) {
|
| + State* s = RunStateOnByte(info->start, i);
|
| + if (s == NULL) {
|
| + WriteMemoryBarrier(); // Synchronize with "quick check" above.
|
| + info->firstbyte = firstbyte;
|
| + return false;
|
| + }
|
| + if (s == info->start)
|
| + continue;
|
| + // Goes to new state...
|
| + if (firstbyte == kFbNone) {
|
| + firstbyte = i; // ... first one
|
| + } else {
|
| + firstbyte = kFbMany; // ... too many
|
| + break;
|
| + }
|
| + }
|
| + WriteMemoryBarrier(); // Synchronize with "quick check" above.
|
| + info->firstbyte = firstbyte;
|
| + return true;
|
| +}
|
| +
|
| +// The actual DFA search: calls AnalyzeSearch and then FastSearchLoop.
|
| +bool DFA::Search(const StringPiece& text,
|
| + const StringPiece& context,
|
| + bool anchored,
|
| + bool want_earliest_match,
|
| + bool run_forward,
|
| + bool* failed,
|
| + const char** epp,
|
| + vector<int>* matches) {
|
| + *epp = NULL;
|
| + if (!ok()) {
|
| + *failed = true;
|
| + return false;
|
| + }
|
| + *failed = false;
|
| +
|
| + if (DebugDFA) {
|
| + fprintf(stderr, "\nprogram:\n%s\n", prog_->DumpUnanchored().c_str());
|
| + fprintf(stderr, "text %s anchored=%d earliest=%d fwd=%d kind %d\n",
|
| + text.as_string().c_str(), anchored, want_earliest_match,
|
| + run_forward, kind_);
|
| + }
|
| +
|
| + RWLocker l(&cache_mutex_);
|
| + SearchParams params(text, context, &l);
|
| + params.anchored = anchored;
|
| + params.want_earliest_match = want_earliest_match;
|
| + params.run_forward = run_forward;
|
| + params.matches = matches;
|
| +
|
| + if (!AnalyzeSearch(¶ms)) {
|
| + *failed = true;
|
| + return false;
|
| + }
|
| + if (params.start == DeadState)
|
| + return false;
|
| + if (params.start == FullMatchState) {
|
| + if (run_forward == want_earliest_match)
|
| + *epp = text.begin();
|
| + else
|
| + *epp = text.end();
|
| + return true;
|
| + }
|
| + if (DebugDFA)
|
| + fprintf(stderr, "start %s\n", DumpState(params.start).c_str());
|
| + bool ret = FastSearchLoop(¶ms);
|
| + if (params.failed) {
|
| + *failed = true;
|
| + return false;
|
| + }
|
| + *epp = params.ep;
|
| + return ret;
|
| +}
|
| +
|
| +// Deletes dfa.
|
| +//
|
| +// This is a separate function so that
|
| +// prog.h can be used without moving the definition of
|
| +// class DFA out of this file. If you set
|
| +// prog->dfa_ = dfa;
|
| +// then you also have to set
|
| +// prog->delete_dfa_ = DeleteDFA;
|
| +// so that ~Prog can delete the dfa.
|
| +static void DeleteDFA(DFA* dfa) {
|
| + delete dfa;
|
| +}
|
| +
|
| +DFA* Prog::GetDFA(MatchKind kind) {
|
| + DFA*volatile* pdfa;
|
| + if (kind == kFirstMatch || kind == kManyMatch) {
|
| + pdfa = &dfa_first_;
|
| + } else {
|
| + kind = kLongestMatch;
|
| + pdfa = &dfa_longest_;
|
| + }
|
| +
|
| + // Quick check; okay because of memory barrier below.
|
| + DFA *dfa = *pdfa;
|
| + if (dfa != NULL) {
|
| + ANNOTATE_HAPPENS_AFTER(dfa);
|
| + return dfa;
|
| + }
|
| +
|
| + MutexLock l(&dfa_mutex_);
|
| + dfa = *pdfa;
|
| + if (dfa != NULL)
|
| + return dfa;
|
| +
|
| + // For a forward DFA, half the memory goes to each DFA.
|
| + // For a reverse DFA, all the memory goes to the
|
| + // "longest match" DFA, because RE2 never does reverse
|
| + // "first match" searches.
|
| + int64 m = dfa_mem_/2;
|
| + if (reversed_) {
|
| + if (kind == kLongestMatch || kind == kManyMatch)
|
| + m = dfa_mem_;
|
| + else
|
| + m = 0;
|
| + }
|
| + dfa = new DFA(this, kind, m);
|
| + delete_dfa_ = DeleteDFA;
|
| +
|
| + // Synchronize with "quick check" above.
|
| + ANNOTATE_HAPPENS_BEFORE(dfa);
|
| + WriteMemoryBarrier();
|
| + *pdfa = dfa;
|
| +
|
| + return dfa;
|
| +}
|
| +
|
| +
|
| +// Executes the regexp program to search in text,
|
| +// which itself is inside the larger context. (As a convenience,
|
| +// passing a NULL context is equivalent to passing text.)
|
| +// Returns true if a match is found, false if not.
|
| +// If a match is found, fills in match0->end() to point at the end of the match
|
| +// and sets match0->begin() to text.begin(), since the DFA can't track
|
| +// where the match actually began.
|
| +//
|
| +// This is the only external interface (class DFA only exists in this file).
|
| +//
|
| +bool Prog::SearchDFA(const StringPiece& text, const StringPiece& const_context,
|
| + Anchor anchor, MatchKind kind,
|
| + StringPiece* match0, bool* failed, vector<int>* matches) {
|
| + *failed = false;
|
| +
|
| + StringPiece context = const_context;
|
| + if (context.begin() == NULL)
|
| + context = text;
|
| + bool carat = anchor_start();
|
| + bool dollar = anchor_end();
|
| + if (reversed_) {
|
| + bool t = carat;
|
| + carat = dollar;
|
| + dollar = t;
|
| + }
|
| + if (carat && context.begin() != text.begin())
|
| + return false;
|
| + if (dollar && context.end() != text.end())
|
| + return false;
|
| +
|
| + // Handle full match by running an anchored longest match
|
| + // and then checking if it covers all of text.
|
| + bool anchored = anchor == kAnchored || anchor_start() || kind == kFullMatch;
|
| + bool endmatch = false;
|
| + if (kind == kManyMatch) {
|
| + endmatch = true;
|
| + } else if (kind == kFullMatch || anchor_end()) {
|
| + endmatch = true;
|
| + kind = kLongestMatch;
|
| + }
|
| +
|
| + // If the caller doesn't care where the match is (just whether one exists),
|
| + // then we can stop at the very first match we find, the so-called
|
| + // "shortest match".
|
| + bool want_shortest_match = false;
|
| + if (match0 == NULL && !endmatch) {
|
| + want_shortest_match = true;
|
| + kind = kLongestMatch;
|
| + }
|
| +
|
| + DFA* dfa = GetDFA(kind);
|
| + const char* ep;
|
| + bool matched = dfa->Search(text, context, anchored,
|
| + want_shortest_match, !reversed_,
|
| + failed, &ep, matches);
|
| + if (*failed)
|
| + return false;
|
| + if (!matched)
|
| + return false;
|
| + if (endmatch && ep != (reversed_ ? text.begin() : text.end()))
|
| + return false;
|
| +
|
| + // If caller cares, record the boundary of the match.
|
| + // We only know where it ends, so use the boundary of text
|
| + // as the beginning.
|
| + if (match0) {
|
| + if (reversed_)
|
| + *match0 = StringPiece(ep, text.end() - ep);
|
| + else
|
| + *match0 = StringPiece(text.begin(), ep - text.begin());
|
| + }
|
| + return true;
|
| +}
|
| +
|
| +// Build out all states in DFA. Returns number of states.
|
| +int DFA::BuildAllStates() {
|
| + if (!ok())
|
| + return 0;
|
| +
|
| + // Pick out start state for unanchored search
|
| + // at beginning of text.
|
| + RWLocker l(&cache_mutex_);
|
| + SearchParams params(NULL, NULL, &l);
|
| + params.anchored = false;
|
| + if (!AnalyzeSearch(¶ms) || params.start <= SpecialStateMax)
|
| + return 0;
|
| +
|
| + // Add start state to work queue.
|
| + StateSet queued;
|
| + vector<State*> q;
|
| + queued.insert(params.start);
|
| + q.push_back(params.start);
|
| +
|
| + // Flood to expand every state.
|
| + for (int i = 0; i < q.size(); i++) {
|
| + State* s = q[i];
|
| + for (int c = 0; c < 257; c++) {
|
| + State* ns = RunStateOnByteUnlocked(s, c);
|
| + if (ns > SpecialStateMax && queued.find(ns) == queued.end()) {
|
| + queued.insert(ns);
|
| + q.push_back(ns);
|
| + }
|
| + }
|
| + }
|
| +
|
| + return q.size();
|
| +}
|
| +
|
| +// Build out all states in DFA for kind. Returns number of states.
|
| +int Prog::BuildEntireDFA(MatchKind kind) {
|
| + //LOG(ERROR) << "BuildEntireDFA is only for testing.";
|
| + return GetDFA(kind)->BuildAllStates();
|
| +}
|
| +
|
| +// Computes min and max for matching string.
|
| +// Won't return strings bigger than maxlen.
|
| +bool DFA::PossibleMatchRange(string* min, string* max, int maxlen) {
|
| + if (!ok())
|
| + return false;
|
| +
|
| + // NOTE: if future users of PossibleMatchRange want more precision when
|
| + // presented with infinitely repeated elements, consider making this a
|
| + // parameter to PossibleMatchRange.
|
| + static int kMaxEltRepetitions = 0;
|
| +
|
| + // Keep track of the number of times we've visited states previously. We only
|
| + // revisit a given state if it's part of a repeated group, so if the value
|
| + // portion of the map tuple exceeds kMaxEltRepetitions we bail out and set
|
| + // |*max| to |PrefixSuccessor(*max)|.
|
| + //
|
| + // Also note that previously_visited_states[UnseenStatePtr] will, in the STL
|
| + // tradition, implicitly insert a '0' value at first use. We take advantage
|
| + // of that property below.
|
| + map<State*, int> previously_visited_states;
|
| +
|
| + // Pick out start state for anchored search at beginning of text.
|
| + RWLocker l(&cache_mutex_);
|
| + SearchParams params(NULL, NULL, &l);
|
| + params.anchored = true;
|
| + if (!AnalyzeSearch(¶ms))
|
| + return false;
|
| + if (params.start == DeadState) { // No matching strings
|
| + *min = "";
|
| + *max = "";
|
| + return true;
|
| + }
|
| + if (params.start == FullMatchState) // Every string matches: no max
|
| + return false;
|
| +
|
| + // The DFA is essentially a big graph rooted at params.start,
|
| + // and paths in the graph correspond to accepted strings.
|
| + // Each node in the graph has potentially 256+1 arrows
|
| + // coming out, one for each byte plus the magic end of
|
| + // text character kByteEndText.
|
| +
|
| + // To find the smallest possible prefix of an accepted
|
| + // string, we just walk the graph preferring to follow
|
| + // arrows with the lowest bytes possible. To find the
|
| + // largest possible prefix, we follow the largest bytes
|
| + // possible.
|
| +
|
| + // The test for whether there is an arrow from s on byte j is
|
| + // ns = RunStateOnByteUnlocked(s, j);
|
| + // if (ns == NULL)
|
| + // return false;
|
| + // if (ns != DeadState && ns->ninst > 0)
|
| + // The RunStateOnByteUnlocked call asks the DFA to build out the graph.
|
| + // It returns NULL only if the DFA has run out of memory,
|
| + // in which case we can't be sure of anything.
|
| + // The second check sees whether there was graph built
|
| + // and whether it is interesting graph. Nodes might have
|
| + // ns->ninst == 0 if they exist only to represent the fact
|
| + // that a match was found on the previous byte.
|
| +
|
| + // Build minimum prefix.
|
| + State* s = params.start;
|
| + min->clear();
|
| + for (int i = 0; i < maxlen; i++) {
|
| + if (previously_visited_states[s] > kMaxEltRepetitions) {
|
| + VLOG(2) << "Hit kMaxEltRepetitions=" << kMaxEltRepetitions
|
| + << " for state s=" << s << " and min=" << CEscape(*min);
|
| + break;
|
| + }
|
| + previously_visited_states[s]++;
|
| +
|
| + // Stop if min is a match.
|
| + State* ns = RunStateOnByteUnlocked(s, kByteEndText);
|
| + if (ns == NULL) // DFA out of memory
|
| + return false;
|
| + if (ns != DeadState && (ns == FullMatchState || ns->IsMatch()))
|
| + break;
|
| +
|
| + // Try to extend the string with low bytes.
|
| + bool extended = false;
|
| + for (int j = 0; j < 256; j++) {
|
| + ns = RunStateOnByteUnlocked(s, j);
|
| + if (ns == NULL) // DFA out of memory
|
| + return false;
|
| + if (ns == FullMatchState ||
|
| + (ns > SpecialStateMax && ns->ninst_ > 0)) {
|
| + extended = true;
|
| + min->append(1, j);
|
| + s = ns;
|
| + break;
|
| + }
|
| + }
|
| + if (!extended)
|
| + break;
|
| + }
|
| +
|
| + // Build maximum prefix.
|
| + previously_visited_states.clear();
|
| + s = params.start;
|
| + max->clear();
|
| + for (int i = 0; i < maxlen; i++) {
|
| + if (previously_visited_states[s] > kMaxEltRepetitions) {
|
| + VLOG(2) << "Hit kMaxEltRepetitions=" << kMaxEltRepetitions
|
| + << " for state s=" << s << " and max=" << CEscape(*max);
|
| + break;
|
| + }
|
| + previously_visited_states[s] += 1;
|
| +
|
| + // Try to extend the string with high bytes.
|
| + bool extended = false;
|
| + for (int j = 255; j >= 0; j--) {
|
| + State* ns = RunStateOnByteUnlocked(s, j);
|
| + if (ns == NULL)
|
| + return false;
|
| + if (ns == FullMatchState ||
|
| + (ns > SpecialStateMax && ns->ninst_ > 0)) {
|
| + extended = true;
|
| + max->append(1, j);
|
| + s = ns;
|
| + break;
|
| + }
|
| + }
|
| + if (!extended) {
|
| + // Done, no need for PrefixSuccessor.
|
| + return true;
|
| + }
|
| + }
|
| +
|
| + // Stopped while still adding to *max - round aaaaaaaaaa... to aaaa...b
|
| + *max = PrefixSuccessor(*max);
|
| +
|
| + // If there are no bytes left, we have no way to say "there is no maximum
|
| + // string". We could make the interface more complicated and be able to
|
| + // return "there is no maximum but here is a minimum", but that seems like
|
| + // overkill -- the most common no-max case is all possible strings, so not
|
| + // telling the caller that the empty string is the minimum match isn't a
|
| + // great loss.
|
| + if (max->empty())
|
| + return false;
|
| +
|
| + return true;
|
| +}
|
| +
|
| +// PossibleMatchRange for a Prog.
|
| +bool Prog::PossibleMatchRange(string* min, string* max, int maxlen) {
|
| + DFA* dfa = NULL;
|
| + {
|
| + MutexLock l(&dfa_mutex_);
|
| + // Have to use dfa_longest_ to get all strings for full matches.
|
| + // For example, (a|aa) never matches aa in first-match mode.
|
| + if (dfa_longest_ == NULL) {
|
| + dfa_longest_ = new DFA(this, Prog::kLongestMatch, dfa_mem_/2);
|
| + delete_dfa_ = DeleteDFA;
|
| + }
|
| + dfa = dfa_longest_;
|
| + }
|
| + return dfa->PossibleMatchRange(min, max, maxlen);
|
| +}
|
| +
|
| +} // namespace re2
|
|
|
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