void*
nsPresArena::Allocate(uint32_t aCode, size_t aSize)
{
NS_ABORT_IF_FALSE(aSize > 0, "PresArena cannot allocate zero bytes");
// We only hand out aligned sizes
aSize = PL_ARENA_ALIGN(&mPool, aSize);
// If there is no free-list entry for this type already, we have
// to create one now, to record its size.
FreeList* list = mFreeLists.PutEntry(aCode);
nsTArray<void*>::index_type len = list->mEntries.Length();
if (list->mEntrySize == 0) {
NS_ABORT_IF_FALSE(len == 0, "list with entries but no recorded size");
list->mEntrySize = aSize;
} else {
NS_ABORT_IF_FALSE(list->mEntrySize == aSize,
"different sizes for same object type code");
}
void* result;
if (len > 0) {
// LIFO behavior for best cache utilization
result = list->mEntries.ElementAt(len - 1);
list->mEntries.RemoveElementAt(len - 1);
#if defined(DEBUG)
{
MOZ_MAKE_MEM_DEFINED(result, list->mEntrySize);
char* p = reinterpret_cast<char*>(result);
char* limit = p + list->mEntrySize;
for (; p < limit; p += sizeof(uintptr_t)) {
uintptr_t val = *reinterpret_cast<uintptr_t*>(p);
NS_ABORT_IF_FALSE(val == mozPoisonValue(),
nsPrintfCString("PresArena: poison overwritten; "
"wanted %.16llx "
"found %.16llx "
"errors in bits %.16llx",
uint64_t(mozPoisonValue()),
uint64_t(val),
uint64_t(mozPoisonValue() ^ val)
).get());
}
}
#endif
MOZ_MAKE_MEM_UNDEFINED(result, list->mEntrySize);
return result;
}
// Allocate a new chunk from the arena
list->mEntriesEverAllocated++;
PL_ARENA_ALLOCATE(result, &mPool, aSize);
if (!result) {
NS_ABORT_OOM(aSize);
}
return result;
}
inline size_t
nsRuleData::GetPoisonOffset()
{
// Fill in mValueOffsets such that mValueStorage + mValueOffsets[i]
// will yield the frame poison value for all uninitialized value
// offsets.
static_assert(sizeof(uintptr_t) == sizeof(size_t),
"expect uintptr_t and size_t to be the same size");
static_assert(uintptr_t(-1) > uintptr_t(0),
"expect uintptr_t to be unsigned");
static_assert(size_t(-1) > size_t(0),
"expect size_t to be unsigned");
uintptr_t framePoisonValue = mozPoisonValue();
return size_t(framePoisonValue - uintptr_t(mValueStorage)) /
sizeof(nsCSSValue);
}
