src/vm/RegExpStatics.h

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: set ts=8 sts=2 et sw=2 tw=80:
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef vm_RegExpStatics_h
#define vm_RegExpStatics_h

#include "gc/Marking.h"
#include "vm/JSContext.h"
#include "vm/MatchPairs.h"
#include "vm/RegExpShared.h"
#include "vm/Runtime.h"

namespace js {

class GlobalObject;
class RegExpStaticsObject;

class RegExpStatics {
  /* The latest RegExp output, set after execution. */
  VectorMatchPairs matches;
  HeapPtr<JSLinearString*> matchesInput;

  /*
   * The previous RegExp input, used to resolve lazy state.
   * A raw RegExpShared cannot be stored because it may be in
   * a different compartment via evalcx().
   */
  HeapPtr<JSAtom*> lazySource;
  JS::RegExpFlags lazyFlags;
  size_t lazyIndex;

  /* The latest RegExp input, set before execution. */
  HeapPtr<JSString*> pendingInput;

  /*
   * If non-zero, |matchesInput| and the |lazy*| fields may be used
   * to replay the last executed RegExp, and |matches| is invalid.
   */
  int32_t pendingLazyEvaluation;

 public:
  RegExpStatics() { clear(); }
  static RegExpStaticsObject* create(JSContext* cx);

 private:
  bool executeLazy(JSContext* cx);

  inline void checkInvariants();

  /*
   * Check whether a match for pair |pairNum| occurred.  If so, allocate and
   * store the match string in |*out|; otherwise place |undefined| in |*out|.
   */
  bool makeMatch(JSContext* cx, size_t pairNum, MutableHandleValue out);
  bool createDependent(JSContext* cx, size_t start, size_t end,
                       MutableHandleValue out);

 public:
  /* Mutators. */
  inline bool updateFromMatchPairs(JSContext* cx, JSLinearString* input,
                                   VectorMatchPairs& newPairs);

  inline void clear();

  /* Corresponds to JSAPI functionality to set the pending RegExp input. */
  void reset(JSString* newInput) {
    clear();
    pendingInput = newInput;
    checkInvariants();
  }

  inline void setPendingInput(JSString* newInput);

 public:
  void trace(JSTracer* trc) {
    /*
     * Changes to this function must also be reflected in
     * RegExpStatics::AutoRooter::trace().
     */
    TraceNullableEdge(trc, &matchesInput, "res->matchesInput");
    TraceNullableEdge(trc, &lazySource, "res->lazySource");
    TraceNullableEdge(trc, &pendingInput, "res->pendingInput");
  }

  /* Value creators. */

  bool createPendingInput(JSContext* cx, MutableHandleValue out);
  bool createLastMatch(JSContext* cx, MutableHandleValue out);
  bool createLastParen(JSContext* cx, MutableHandleValue out);
  bool createParen(JSContext* cx, size_t pairNum, MutableHandleValue out);
  bool createLeftContext(JSContext* cx, MutableHandleValue out);
  bool createRightContext(JSContext* cx, MutableHandleValue out);

  static size_t offsetOfPendingInput() {
    return offsetof(RegExpStatics, pendingInput);
  }

  static size_t offsetOfMatchesInput() {
    return offsetof(RegExpStatics, matchesInput);
  }

  static size_t offsetOfLazySource() {
    return offsetof(RegExpStatics, lazySource);
  }

  static size_t offsetOfLazyFlags() {
    return offsetof(RegExpStatics, lazyFlags);
  }

  static size_t offsetOfLazyIndex() {
    return offsetof(RegExpStatics, lazyIndex);
  }

  static size_t offsetOfPendingLazyEvaluation() {
    return offsetof(RegExpStatics, pendingLazyEvaluation);
  }
};

inline bool RegExpStatics::createDependent(JSContext* cx, size_t start,
                                           size_t end, MutableHandleValue out) {
  /* Private function: caller must perform lazy evaluation. */
  MOZ_ASSERT(!pendingLazyEvaluation);

  MOZ_ASSERT(start <= end);
  MOZ_ASSERT(end <= matchesInput->length());
  JSString* str = NewDependentString(cx, matchesInput, start, end - start);
  if (!str) {
    return false;
  }
  out.setString(str);
  return true;
}

inline bool RegExpStatics::createPendingInput(JSContext* cx,
                                              MutableHandleValue out) {
  /* Lazy evaluation need not be resolved to return the input. */
  out.setString(pendingInput ? pendingInput.get()
                             : cx->runtime()->emptyString.ref());
  return true;
}

inline bool RegExpStatics::makeMatch(JSContext* cx, size_t pairNum,
                                     MutableHandleValue out) {
  /* Private function: caller must perform lazy evaluation. */
  MOZ_ASSERT(!pendingLazyEvaluation);

  if (matches.empty() || pairNum >= matches.pairCount() ||
      matches[pairNum].isUndefined()) {
    out.setUndefined();
    return true;
  }

  const MatchPair& pair = matches[pairNum];
  return createDependent(cx, pair.start, pair.limit, out);
}

inline bool RegExpStatics::createLastMatch(JSContext* cx,
                                           MutableHandleValue out) {
  if (!executeLazy(cx)) {
    return false;
  }
  return makeMatch(cx, 0, out);
}

inline bool RegExpStatics::createLastParen(JSContext* cx,
                                           MutableHandleValue out) {
  if (!executeLazy(cx)) {
    return false;
  }

  if (matches.empty() || matches.pairCount() == 1) {
    out.setString(cx->runtime()->emptyString);
    return true;
  }
  const MatchPair& pair = matches[matches.pairCount() - 1];
  if (pair.start == -1) {
    out.setString(cx->runtime()->emptyString);
    return true;
  }
  MOZ_ASSERT(pair.start >= 0 && pair.limit >= 0);
  MOZ_ASSERT(pair.limit >= pair.start);
  return createDependent(cx, pair.start, pair.limit, out);
}

inline bool RegExpStatics::createParen(JSContext* cx, size_t pairNum,
                                       MutableHandleValue out) {
  MOZ_ASSERT(pairNum >= 1);
  if (!executeLazy(cx)) {
    return false;
  }

  if (matches.empty() || pairNum >= matches.pairCount()) {
    out.setString(cx->runtime()->emptyString);
    return true;
  }
  return makeMatch(cx, pairNum, out);
}

inline bool RegExpStatics::createLeftContext(JSContext* cx,
                                             MutableHandleValue out) {
  if (!executeLazy(cx)) {
    return false;
  }

  if (matches.empty()) {
    out.setString(cx->runtime()->emptyString);
    return true;
  }
  if (matches[0].start < 0) {
    out.setUndefined();
    return true;
  }
  return createDependent(cx, 0, matches[0].start, out);
}

inline bool RegExpStatics::createRightContext(JSContext* cx,
                                              MutableHandleValue out) {
  if (!executeLazy(cx)) {
    return false;
  }

  if (matches.empty()) {
    out.setString(cx->runtime()->emptyString);
    return true;
  }
  if (matches[0].limit < 0) {
    out.setUndefined();
    return true;
  }
  return createDependent(cx, matches[0].limit, matchesInput->length(), out);
}

inline bool RegExpStatics::updateFromMatchPairs(JSContext* cx,
                                                JSLinearString* input,
                                                VectorMatchPairs& newPairs) {
  MOZ_ASSERT(input);

  /* Unset all lazy state. */
  pendingLazyEvaluation = false;
  this->lazySource = nullptr;
  this->lazyIndex = size_t(-1);

  BarrieredSetPair<JSString, JSLinearString>(cx->zone(), pendingInput, input,
                                             matchesInput, input);

  if (!matches.initArrayFrom(newPairs)) {
    ReportOutOfMemory(cx);
    return false;
  }

  return true;
}

inline void RegExpStatics::clear() {
  matches.forgetArray();
  matchesInput = nullptr;
  lazySource = nullptr;
  lazyFlags = JS::RegExpFlag::NoFlags;
  lazyIndex = size_t(-1);
  pendingInput = nullptr;
  pendingLazyEvaluation = false;
}

inline void RegExpStatics::setPendingInput(JSString* newInput) {
  pendingInput = newInput;
}

inline void RegExpStatics::checkInvariants() {
#ifdef DEBUG
  if (pendingLazyEvaluation) {
    MOZ_ASSERT(lazySource);
    MOZ_ASSERT(matchesInput);
    MOZ_ASSERT(lazyIndex != size_t(-1));
    return;
  }

  if (matches.empty()) {
    MOZ_ASSERT(!matchesInput);
    return;
  }

  /* Pair count is non-zero, so there must be match pairs input. */
  MOZ_ASSERT(matchesInput);
  size_t mpiLen = matchesInput->length();

  /* Both members of the first pair must be non-negative. */
  MOZ_ASSERT(!matches[0].isUndefined());
  MOZ_ASSERT(matches[0].limit >= 0);

  /* Present pairs must be valid. */
  for (size_t i = 0; i < matches.pairCount(); i++) {
    if (matches[i].isUndefined()) {
      continue;
    }
    const MatchPair& pair = matches[i];
    MOZ_ASSERT(mpiLen >= size_t(pair.limit) && pair.limit >= pair.start &&
               pair.start >= 0);
  }
#endif /* DEBUG */
}

} /* namespace js */

#endif /* vm_RegExpStatics_h */