Greetings,
I have qustion about chunk class in SmallObj.
Chunk::Allocate/Deallocate funtions.
void* Chunk::Allocate(std::size_t blockSize)
{
if ( IsFilled() ) return NULL;
assert((firstAvailableBlock_ * blockSize) / blockSize ==
firstAvailableBlock_);
[b]unsigned char * pResult = pData_ + (firstAvailableBlock_ * blockSize);
firstAvailableBlock_ = *pResult; //and if next block was allready allocated?!!![/b]
--blocksAvailable_;
return pResult;
}
// Chunk::Deallocate ----------------------------------------------------------
void Chunk::Deallocate(void* p, std::size_t blockSize)
{
assert(p >= pData_);
unsigned char* toRelease = static_cast<unsigned char*>(p);
// Alignment check
assert((toRelease - pData_) % blockSize == 0);
unsigned char index = static_cast< unsigned char >(
( toRelease - pData_ ) / blockSize);
#if defined(DEBUG) || defined(_DEBUG)
// Check if block was already deleted. Attempting to delete the same
// block more than once causes Chunk's linked-list of stealth indexes to
// become corrupt. And causes count of blocksAvailable_ to be wrong.
if ( 0 < blocksAvailable_ )
assert( firstAvailableBlock_ != index );
#endif
*toRelease = firstAvailableBlock_;
[b] firstAvailableBlock_ = index; //OK AND What about free blocks before this???[/b]
// Truncation check
assert(firstAvailableBlock_ == (toRelease - pData_) / blockSize);
++blocksAvailable_;
}
Problem 1)
We dont check if next block is already allocated, we can allocate block more tha once without deallocating it.
Example allocating 2 blocks:
Problem 2)
For example we have allocated 8 blocks of char(it's not mater)
Then we deallocated blocks with index 6, 2, 4, 8
last index will be 8! (as last deallocate)
More than while we reach end of blocks we have 3 blocks available and will have errors of allocating from this stage.
ps Maybe i some thing dont understand so can you help me
loki 0.1.7
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Greetings,
I have qustion about chunk class in SmallObj.
Chunk::Allocate/Deallocate funtions.
void* Chunk::Allocate(std::size_t blockSize) { if ( IsFilled() ) return NULL; assert((firstAvailableBlock_ * blockSize) / blockSize == firstAvailableBlock_); [b]unsigned char * pResult = pData_ + (firstAvailableBlock_ * blockSize); firstAvailableBlock_ = *pResult; //and if next block was allready allocated?!!![/b] --blocksAvailable_; return pResult; } // Chunk::Deallocate ---------------------------------------------------------- void Chunk::Deallocate(void* p, std::size_t blockSize) { assert(p >= pData_); unsigned char* toRelease = static_cast<unsigned char*>(p); // Alignment check assert((toRelease - pData_) % blockSize == 0); unsigned char index = static_cast< unsigned char >( ( toRelease - pData_ ) / blockSize); #if defined(DEBUG) || defined(_DEBUG) // Check if block was already deleted. Attempting to delete the same // block more than once causes Chunk's linked-list of stealth indexes to // become corrupt. And causes count of blocksAvailable_ to be wrong. if ( 0 < blocksAvailable_ ) assert( firstAvailableBlock_ != index ); #endif *toRelease = firstAvailableBlock_; [b] firstAvailableBlock_ = index; //OK AND What about free blocks before this???[/b] // Truncation check assert(firstAvailableBlock_ == (toRelease - pData_) / blockSize); ++blocksAvailable_; }Problem 1)
We dont check if next block is already allocated, we can allocate block more tha once without deallocating it.
Example allocating 2 blocks:
Problem 2)
For example we have allocated 8 blocks of char(it's not mater)
Then we deallocated blocks with index 6, 2, 4, 8
last index will be 8! (as last deallocate)
More than while we reach end of blocks we have 3 blocks available and will have errors of allocating from this stage.
ps Maybe i some thing dont understand so can you help me
loki 0.1.7