bool FixedAllocator::Deallocate( void * p, Chunk * hint )
{
assert(!chunks_.empty());
assert(&chunks_.front() <= deallocChunk_);
assert(&chunks_.back() >= deallocChunk_);
assert( &chunks_.front() <= allocChunk_ );
assert( &chunks_.back() >= allocChunk_ );
assert( CountEmptyChunks() < 2 );
Chunk * foundChunk = ( NULL == hint ) ? VicinityFind( p ) : hint;
if ( NULL == foundChunk )
return false;
assert( foundChunk->HasBlock( p, numBlocks_ * blockSize_ ) );
#ifdef LOKI_CHECK_FOR_CORRUPTION
if ( foundChunk->IsCorrupt( numBlocks_, blockSize_, true ) )
{
assert( false );
return false;
}
if ( foundChunk->IsBlockAvailable( p, numBlocks_, blockSize_ ) )
{
assert( false );
return false;
}
#endif
deallocChunk_ = foundChunk;
DoDeallocate(p);
assert( CountEmptyChunks() < 2 );
return true;
}
bool FixedAllocator::TrimEmptyChunk( void )
{
// prove either emptyChunk_ points nowhere, or points to a truly empty Chunk.
assert( ( NULL == emptyChunk_ ) || ( emptyChunk_->HasAvailable( numBlocks_ ) ) );
if ( NULL == emptyChunk_ ) return false;
// If emptyChunk_ points to valid Chunk, then chunk list is not empty.
assert( !chunks_.empty() );
// And there should be exactly 1 empty Chunk.
assert( 1 == CountEmptyChunks() );
Chunk * lastChunk = &chunks_.back();
if ( lastChunk != emptyChunk_ )
std::swap( *emptyChunk_, *lastChunk );
assert( lastChunk->HasAvailable( numBlocks_ ) );
lastChunk->Release();
chunks_.pop_back();
if ( chunks_.empty() )
{
allocChunk_ = NULL;
deallocChunk_ = NULL;
}
else
{
if ( deallocChunk_ == emptyChunk_ )
{
deallocChunk_ = &chunks_.front();
assert( deallocChunk_->blocksAvailable_ < numBlocks_ );
}
if ( allocChunk_ == emptyChunk_ )
{
allocChunk_ = &chunks_.back();
assert( allocChunk_->blocksAvailable_ < numBlocks_ );
}
}
emptyChunk_ = NULL;
assert( 0 == CountEmptyChunks() );
return true;
}
bool FixedAllocator::TrimChunkList( void )
{
if ( chunks_.empty() )
{
assert( NULL == allocChunk_ );
assert( NULL == deallocChunk_ );
}
if ( chunks_.size() == chunks_.capacity() )
return false;
// Use the "make-a-temp-and-swap" trick to remove excess capacity.
Chunks( chunks_ ).swap( chunks_ );
return true;
}
char* allocate(size_t size)
{
assert(size <= chunk_size);
if (chunks.empty() ||
(next_free + size) > chunk_size)
{
char* chunk = new char[chunk_size];
chunks.push_back(chunk);
next_free = 0;
}
char* ptr = chunks.back() + next_free;
next_free += size;
return ptr;
}
void FixedAllocator::Deallocate(void *p)
{
assert(last_dealloc_);
assert(!chunks_.empty());
// find the chunk that holds the pointer.
last_dealloc_ = FindChunk(p);
assert(last_dealloc_);
// found the chunk, so forwards deallocation request to it.
last_dealloc_->Deallocate(p, block_size_);
// the chunk is empty, should we free it?
if (last_dealloc_->blocks_available_ == blocks_)
{
MemChunk *last_chunk = &chunks_.back();
if (last_chunk = last_dealloc_)
{
if (chunks_.size() > 1 && last_dealloc_[-1].blocks_available_ == blocks_)
{
// there are two free chunk, so free one.
last_chunk->Free();
chunks_.pop_back();
last_alloc_ = last_dealloc_ = &chunks_.front();
}
}
else if (last_chunk->blocks_available_ == blocks_)
{
// there are two free chunk, so free one.
last_chunk->Free();
chunks_.pop_back();
last_alloc_ = last_dealloc_;
}
else
{
// move the empty chunk to the bottom.
std::swap(*last_dealloc_, *last_chunk);
last_alloc_ = last_dealloc_;
}
}
}
FixedAllocator::Chunk * FixedAllocator::VicinityFind( void * p )
{
if ( chunks_.empty() ) return NULL;
assert(deallocChunk_);
unsigned char * pc = static_cast< unsigned char * >( p );
const std::size_t chunkLength = numBlocks_ * blockSize_;
Chunk* lo = deallocChunk_;
Chunk* hi = deallocChunk_ + 1;
Chunk* loBound = &chunks_.front();
Chunk* hiBound = &chunks_.back() + 1;
// Special case: deallocChunk_ is the last in the array
if (hi == hiBound) hi = NULL;
for (;;)
{
if (lo)
{
if ( lo->HasBlock( pc, chunkLength ) ) return lo;
if ( lo == loBound )
{
lo = NULL;
if ( NULL == hi ) break;
}
else --lo;
}
if (hi)
{
if ( hi->HasBlock( pc, chunkLength ) ) return hi;
if ( ++hi == hiBound )
{
hi = NULL;
if ( NULL == lo ) break;
}
}
}
return NULL;
}
bool FixedAllocator::Deallocate( void * p, bool doChecks )
{
if ( doChecks )
{
assert(!chunks_.empty());
assert(&chunks_.front() <= deallocChunk_);
assert(&chunks_.back() >= deallocChunk_);
assert( &chunks_.front() <= allocChunk_ );
assert( &chunks_.back() >= allocChunk_ );
}
Chunk * foundChunk = VicinityFind( p );
if ( doChecks )
{
assert( NULL != foundChunk );
}
else if ( NULL == foundChunk )
return false;
deallocChunk_ = foundChunk;
DoDeallocate(p);
return true;
}
MemChunk * FixedAllocator::FindChunk(void *p)
{
assert(last_dealloc_);
assert(!chunks_.empty());
MemChunk *lo_b = &chunks_.front();
MemChunk *hi_b = &chunks_.back()+1;
MemChunk *lo = last_dealloc_;
MemChunk *hi = last_dealloc_+1;
if (hi == hi_b) hi = NULL;
for (;;)
{
if (lo)
{
if (InChunk(lo, p))
return lo;
if (lo == lo_b)
lo = NULL;
else
--lo;
}
if (hi)
{
if (InChunk(hi, p))
return hi;
if (++hi == hi_b)
hi = NULL;
}
}
// Never gets here.
assert(false);
return NULL;
}
bool FixedAllocator::IsCorrupt( void ) const
{
const bool isEmpty = chunks_.empty();
ChunkCIter start( chunks_.begin() );
ChunkCIter last( chunks_.end() );
const size_t emptyChunkCount = CountEmptyChunks();
if ( isEmpty )
{
if ( start != last )
{
assert( false );
return true;
}
if ( 0 < emptyChunkCount )
{
assert( false );
return true;
}
if ( NULL != deallocChunk_ )
{
assert( false );
return true;
}
if ( NULL != allocChunk_ )
{
assert( false );
return true;
}
if ( NULL != emptyChunk_ )
{
assert( false );
return true;
}
}
else
{
const Chunk * front = &chunks_.front();
const Chunk * back = &chunks_.back();
if ( start >= last )
{
assert( false );
return true;
}
if ( back < deallocChunk_ )
{
assert( false );
return true;
}
if ( back < allocChunk_ )
{
assert( false );
return true;
}
if ( front > deallocChunk_ )
{
assert( false );
return true;
}
if ( front > allocChunk_ )
{
assert( false );
return true;
}
switch ( emptyChunkCount )
{
case 0:
if ( emptyChunk_ != NULL )
{
assert( false );
return true;
}
break;
case 1:
if ( emptyChunk_ == NULL )
{
assert( false );
return true;
}
if ( back < emptyChunk_ )
{
assert( false );
return true;
}
if ( front > emptyChunk_ )
{
assert( false );
return true;
}
if ( !emptyChunk_->HasAvailable( numBlocks_ ) )
{
// This may imply somebody tried to delete a block twice.
assert( false );
return true;
}
break;
default:
assert( false );
return true;
}
for ( ChunkCIter it( start ); it != last; ++it )
{
const Chunk & chunk = *it;
if ( chunk.IsCorrupt( numBlocks_, blockSize_, true ) )
return true;
}
}
return false;
}
