The Tor Browser: js/src/ds/LifoAlloc.h@129ffea94266 (annotated)

js/src/ds/LifoAlloc.h@129ffea94266 (annotated)

js/src/ds/LifoAlloc.h

Sat, 03 Jan 2015 20:18:00 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Sat, 03 Jan 2015 20:18:00 +0100
branch: TOR_BUG_3246
changeset 7: 129ffea94266
permissions: -rw-r--r--

Conditionally enable double key logic according to:
private browsing mode or privacy.thirdparty.isolate preference and
implement in GetCookieStringCommon and FindCookie where it counts...
With some reservations of how to convince FindCookie users to test
condition and pass a nullptr when disabling double key logic.

 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  * vim: set ts=8 sts=4 et sw=4 tw=99:
  * 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 ds_LifoAlloc_h
 #define ds_LifoAlloc_h
 #include "mozilla/DebugOnly.h"
 #include "mozilla/MathAlgorithms.h"
 #include "mozilla/MemoryChecking.h"
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/PodOperations.h"
 #include "mozilla/TemplateLib.h"
 #include "mozilla/TypeTraits.h"
 // This data structure supports stacky LIFO allocation (mark/release and
 // LifoAllocScope). It does not maintain one contiguous segment; instead, it
 // maintains a bunch of linked memory segments. In order to prevent malloc/free
 // thrashing, unused segments are deallocated when garbage collection occurs.
 #include "jsutil.h"
 namespace js {
 namespace detail {
 static const size_t LIFO_ALLOC_ALIGN = 8;
 MOZ_ALWAYS_INLINE
 char *
 AlignPtr(void *orig)
 {
     static_assert(mozilla::tl::FloorLog2<LIFO_ALLOC_ALIGN>::value ==
                   mozilla::tl::CeilingLog2<LIFO_ALLOC_ALIGN>::value,
                   "LIFO_ALLOC_ALIGN must be a power of two");
     char *result = (char *) ((uintptr_t(orig) + (LIFO_ALLOC_ALIGN - 1)) & (~LIFO_ALLOC_ALIGN + 1));
     JS_ASSERT(uintptr_t(result) % LIFO_ALLOC_ALIGN == 0);
     return result;
 }
 // Header for a chunk of memory wrangled by the LifoAlloc.
 class BumpChunk
 {
     char        *bump;          // start of the available data
     char        *limit;         // end of the data
     BumpChunk   *next_;         // the next BumpChunk
     size_t      bumpSpaceSize;  // size of the data area
     char *headerBase() { return reinterpret_cast<char *>(this); }
     char *bumpBase() const { return limit - bumpSpaceSize; }
     explicit BumpChunk(size_t bumpSpaceSize)
       : bump(reinterpret_cast<char *>(MOZ_THIS_IN_INITIALIZER_LIST()) + sizeof(BumpChunk)),
         limit(bump + bumpSpaceSize),
         next_(nullptr), bumpSpaceSize(bumpSpaceSize)
     {
         JS_ASSERT(bump == AlignPtr(bump));
     }
     void setBump(void *ptr) {
         JS_ASSERT(bumpBase() <= ptr);
         JS_ASSERT(ptr <= limit);
 #if defined(DEBUG) || defined(MOZ_HAVE_MEM_CHECKS)
         char* prevBump = bump;
 #endif
         bump = static_cast<char *>(ptr);
 #ifdef DEBUG
         JS_ASSERT(contains(prevBump));
         // Clobber the now-free space.
         if (prevBump > bump)
             memset(bump, 0xcd, prevBump - bump);
 #endif
         // Poison/Unpoison memory that we just free'd/allocated.
 #if defined(MOZ_HAVE_MEM_CHECKS)
         if (prevBump > bump)
             MOZ_MAKE_MEM_NOACCESS(bump, prevBump - bump);
         else if (bump > prevBump)
             MOZ_MAKE_MEM_UNDEFINED(prevBump, bump - prevBump);
 #endif
     }
   public:
     BumpChunk *next() const { return next_; }
     void setNext(BumpChunk *succ) { next_ = succ; }
     size_t used() const { return bump - bumpBase(); }
     void *start() const { return bumpBase(); }
     void *end() const { return limit; }
     size_t sizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) {
         return mallocSizeOf(this);
     }
     size_t computedSizeOfIncludingThis() {
         return limit - headerBase();
     }
     void resetBump() {
         setBump(headerBase() + sizeof(BumpChunk));
     }
     void *mark() const { return bump; }
     void release(void *mark) {
         JS_ASSERT(contains(mark));
         JS_ASSERT(mark <= bump);
         setBump(mark);
     }
     bool contains(void *mark) const {
         return bumpBase() <= mark && mark <= limit;
     }
     bool canAlloc(size_t n);
     size_t unused() {
         return limit - AlignPtr(bump);
     }
     // Try to perform an allocation of size |n|, return null if not possible.
     MOZ_ALWAYS_INLINE
     void *tryAlloc(size_t n) {
         char *aligned = AlignPtr(bump);
         char *newBump = aligned + n;
         if (newBump > limit)
             return nullptr;
         // Check for overflow.
         if (MOZ_UNLIKELY(newBump < bump))
             return nullptr;
         JS_ASSERT(canAlloc(n)); // Ensure consistency between "can" and "try".
         setBump(newBump);
         return aligned;
     }
     static BumpChunk *new_(size_t chunkSize);
     static void delete_(BumpChunk *chunk);
 };
 } // namespace detail
 // LIFO bump allocator: used for phase-oriented and fast LIFO allocations.
 //
 // Note: |latest| is not necessary "last". We leave BumpChunks latent in the
 // chain after they've been released to avoid thrashing before a GC.
 class LifoAlloc
 {
     typedef detail::BumpChunk BumpChunk;
     BumpChunk   *first;
     BumpChunk   *latest;
     BumpChunk   *last;
     size_t      markCount;
     size_t      defaultChunkSize_;
     size_t      curSize_;
     size_t      peakSize_;
     void operator=(const LifoAlloc &) MOZ_DELETE;
     LifoAlloc(const LifoAlloc &) MOZ_DELETE;
     // Return a BumpChunk that can perform an allocation of at least size |n|
     // and add it to the chain appropriately.
     //
     // Side effect: if retval is non-null, |first| and |latest| are initialized
     // appropriately.
     BumpChunk *getOrCreateChunk(size_t n);
     void reset(size_t defaultChunkSize) {
         JS_ASSERT(mozilla::RoundUpPow2(defaultChunkSize) == defaultChunkSize);
         first = latest = last = nullptr;
         defaultChunkSize_ = defaultChunkSize;
         markCount = 0;
         curSize_ = 0;
     }
     // Append unused chunks to the end of this LifoAlloc.
     void appendUnused(BumpChunk *start, BumpChunk *end) {
         JS_ASSERT(start && end);
         if (last)
             last->setNext(start);
         else
             first = latest = start;
         last = end;
     }
     // Append used chunks to the end of this LifoAlloc. We act as if all the
     // chunks in |this| are used, even if they're not, so memory may be wasted.
     void appendUsed(BumpChunk *start, BumpChunk *latest, BumpChunk *end) {
         JS_ASSERT(start && latest &&  end);
         if (last)
             last->setNext(start);
         else
             first = latest = start;
         last = end;
         this->latest = latest;
     }
     void incrementCurSize(size_t size) {
         curSize_ += size;
         if (curSize_ > peakSize_)
             peakSize_ = curSize_;
     }
     void decrementCurSize(size_t size) {
         JS_ASSERT(curSize_ >= size);
         curSize_ -= size;
     }
   public:
     explicit LifoAlloc(size_t defaultChunkSize)
       : peakSize_(0)
     {
         reset(defaultChunkSize);
     }
     // Steal allocated chunks from |other|.
     void steal(LifoAlloc *other) {
         JS_ASSERT(!other->markCount);
         // Copy everything from |other| to |this| except for |peakSize_|, which
         // requires some care.
         size_t oldPeakSize = peakSize_;
         mozilla::PodAssign(this, other);
         peakSize_ = Max(oldPeakSize, curSize_);
         other->reset(defaultChunkSize_);
     }
     // Append all chunks from |other|. They are removed from |other|.
     void transferFrom(LifoAlloc *other);
     // Append unused chunks from |other|. They are removed from |other|.
     void transferUnusedFrom(LifoAlloc *other);
     ~LifoAlloc() { freeAll(); }
     size_t defaultChunkSize() const { return defaultChunkSize_; }
     // Frees all held memory.
     void freeAll();
     static const unsigned HUGE_ALLOCATION = 50 * 1024 * 1024;
     void freeAllIfHugeAndUnused() {
         if (markCount == 0 && curSize_ > HUGE_ALLOCATION)
             freeAll();
     }
     MOZ_ALWAYS_INLINE
     void *alloc(size_t n) {
         JS_OOM_POSSIBLY_FAIL();
         void *result;
         if (latest && (result = latest->tryAlloc(n)))
             return result;
         if (!getOrCreateChunk(n))
             return nullptr;
         // Since we just created a large enough chunk, this can't fail.
         result = latest->tryAlloc(n);
         MOZ_ASSERT(result);
         return result;
     }
     // Ensures that enough space exists to satisfy N bytes worth of
     // allocation requests, not necessarily contiguous. Note that this does
     // not guarantee a successful single allocation of N bytes.
     MOZ_ALWAYS_INLINE
     bool ensureUnusedApproximate(size_t n) {
         size_t total = 0;
         for (BumpChunk *chunk = latest; chunk; chunk = chunk->next()) {
             total += chunk->unused();
             if (total >= n)
                 return true;
         }
         BumpChunk *latestBefore = latest;
         if (!getOrCreateChunk(n))
             return false;
         if (latestBefore)
             latest = latestBefore;
         return true;
     }
     template <typename T>
     T *newArray(size_t count) {
         JS_STATIC_ASSERT(mozilla::IsPod<T>::value);
         return newArrayUninitialized<T>(count);
     }
     // Create an array with uninitialized elements of type |T|.
     // The caller is responsible for initialization.
     template <typename T>
     T *newArrayUninitialized(size_t count) {
         if (count & mozilla::tl::MulOverflowMask<sizeof(T)>::value)
             return nullptr;
         return static_cast<T *>(alloc(sizeof(T) * count));
     }
     class Mark {
         BumpChunk *chunk;
         void *markInChunk;
         friend class LifoAlloc;
         Mark(BumpChunk *chunk, void *markInChunk) : chunk(chunk), markInChunk(markInChunk) {}
       public:
         Mark() : chunk(nullptr), markInChunk(nullptr) {}
     };
     Mark mark() {
         markCount++;
         return latest ? Mark(latest, latest->mark()) : Mark();
     }
     void release(Mark mark) {
         markCount--;
         if (!mark.chunk) {
             latest = first;
             if (latest)
                 latest->resetBump();
         } else {
             latest = mark.chunk;
             latest->release(mark.markInChunk);
         }
     }
     void releaseAll() {
         JS_ASSERT(!markCount);
         latest = first;
         if (latest)
             latest->resetBump();
     }
     // Get the total "used" (occupied bytes) count for the arena chunks.
     size_t used() const {
         size_t accum = 0;
         for (BumpChunk *chunk = first; chunk; chunk = chunk->next()) {
             accum += chunk->used();
             if (chunk == latest)
                 break;
         }
         return accum;
     }
     // Return true if the LifoAlloc does not currently contain any allocations.
     bool isEmpty() const {
         return !latest || !latest->used();
     }
     // Return the number of bytes remaining to allocate in the current chunk.
     // e.g. How many bytes we can allocate before needing a new block.
     size_t availableInCurrentChunk() const {
         if (!latest)
             return 0;
         return latest->unused();
     }
     // Get the total size of the arena chunks (including unused space).
     size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const {
         size_t n = 0;
         for (BumpChunk *chunk = first; chunk; chunk = chunk->next())
             n += chunk->sizeOfIncludingThis(mallocSizeOf);
         return n;
     }
     // Like sizeOfExcludingThis(), but includes the size of the LifoAlloc itself.
     size_t sizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) const {
         return mallocSizeOf(this) + sizeOfExcludingThis(mallocSizeOf);
     }
     // Get the peak size of the arena chunks (including unused space and
     // bookkeeping space).
     size_t peakSizeOfExcludingThis() const { return peakSize_; }
     // Doesn't perform construction; useful for lazily-initialized POD types.
     template <typename T>
     MOZ_ALWAYS_INLINE
     T *newPod() {
         return static_cast<T *>(alloc(sizeof(T)));
     }
     JS_DECLARE_NEW_METHODS(new_, alloc, MOZ_ALWAYS_INLINE)
     // A mutable enumeration of the allocated data.
     class Enum
     {
         friend class LifoAlloc;
         friend class detail::BumpChunk;
         LifoAlloc *alloc_;  // The LifoAlloc being traversed.
         BumpChunk *chunk_;  // The current chunk.
         char *position_;    // The current position (must be within chunk_).
         // If there is not enough room in the remaining block for |size|,
         // advance to the next block and update the position.
         void ensureSpaceAndAlignment(size_t size) {
             JS_ASSERT(!empty());
             char *aligned = detail::AlignPtr(position_);
             if (aligned + size > chunk_->end()) {
                 chunk_ = chunk_->next();
                 position_ = static_cast<char *>(chunk_->start());
             } else {
                 position_ = aligned;
             }
             JS_ASSERT(uintptr_t(position_) + size <= uintptr_t(chunk_->end()));
         }
       public:
         Enum(LifoAlloc &alloc)
           : alloc_(&alloc),
             chunk_(alloc.first),
             position_(static_cast<char *>(alloc.first ? alloc.first->start() : nullptr))
         {}
         // Return true if there are no more bytes to enumerate.
         bool empty() {
             return !chunk_ || (chunk_ == alloc_->latest && position_ >= chunk_->mark());
         }
         // Move the read position forward by the size of one T.
         template <typename T>
         void popFront() {
             popFront(sizeof(T));
         }
         // Move the read position forward by |size| bytes.
         void popFront(size_t size) {
             ensureSpaceAndAlignment(size);
             position_ = position_ + size;
         }
         // Update the bytes at the current position with a new value.
         template <typename T>
         void updateFront(const T &t) {
             ensureSpaceAndAlignment(sizeof(T));
             memmove(position_, &t, sizeof(T));
         }
         // Return a pointer to the item at the current position. This
         // returns a pointer to the inline storage, not a copy.
         template <typename T>
         T *get(size_t size = sizeof(T)) {
             ensureSpaceAndAlignment(size);
             return reinterpret_cast<T *>(position_);
         }
         // Return a Mark at the current position of the Enum.
         Mark mark() {
             alloc_->markCount++;
             return Mark(chunk_, position_);
         }
     };
 };
 class LifoAllocScope
 {
     LifoAlloc       *lifoAlloc;
     LifoAlloc::Mark mark;
     bool            shouldRelease;
     MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
   public:
     explicit LifoAllocScope(LifoAlloc *lifoAlloc
                             MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
       : lifoAlloc(lifoAlloc),
         mark(lifoAlloc->mark()),
         shouldRelease(true)
     {
         MOZ_GUARD_OBJECT_NOTIFIER_INIT;
     }
     ~LifoAllocScope() {
         if (shouldRelease)
             lifoAlloc->release(mark);
     }
     LifoAlloc &alloc() {
         return *lifoAlloc;
     }
     void releaseEarly() {
         JS_ASSERT(shouldRelease);
         lifoAlloc->release(mark);
         shouldRelease = false;
     }
 };
 class LifoAllocPolicy
 {
     LifoAlloc &alloc_;
   public:
     LifoAllocPolicy(LifoAlloc &alloc)
       : alloc_(alloc)
     {}
     void *malloc_(size_t bytes) {
         return alloc_.alloc(bytes);
     }
     void *calloc_(size_t bytes) {
         void *p = malloc_(bytes);
         if (p)
             memset(p, 0, bytes);
         return p;
     }
     void *realloc_(void *p, size_t oldBytes, size_t bytes) {
         void *n = malloc_(bytes);
         if (!n)
             return n;
         memcpy(n, p, Min(oldBytes, bytes));
         return n;
     }
     void free_(void *p) {
     }
     void reportAllocOverflow() const {
     }
 };
 } // namespace js
 #endif /* ds_LifoAlloc_h */

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js/src/ds/LifoAlloc.h@129ffea94266 (annotated)

js/src/ds/LifoAlloc.h