Class FirstFitAllocatorBase

• Defined in File first_fit_allocator_base.hpp

Nested Types

• Struct FirstFitAllocatorBase::Memory

class FirstFitAllocatorBase

Memory management helper class using first-fit allocation strategy.

This class keeps track of allocated and free regions within a large memory chunk and can efficiently find the first available block that fits a requested size. It works only with indices and relies on an external class to hold the actual memory.

Internally, it uses a binary segment tree to track the largest available block in any given area of memory. All operations have logarithmic time complexity.

Public Types

enum class Error

Error codes used by the first-fit allocator classes.

Values:

enumerator kAlreadyInUse

Returned when the suballocator is already in use and some memory has not been released yet.

enumerator kInvalidSize

Returned if the size is invalid (negative or too big).

enumerator kOutOfMemory

Returned if the class can’t allocate enough memory.

enumerator kBlockNotAllocated

Returned if we attempt to release a block of memory not allocated yet.

enumerator kLogicError

This error happens when there is a logical issue during execution. This should never happen.

template<typename T>
using expected_t = expected<T, Error>

Expected type used by this class.

using unexpected_t = unexpected<Error>

Unexpected type used by this class.

Public Functions

FirstFitAllocatorBase()

Default constructor.

expected_t<void> allocate(int32_t size)

Allocate internal data structures to handle memory requests for a given size.

Requires 32 * 2^ceil(log2(size)) bytes of memory for internal bookkeeping.

Parameters

size – Maximum size of memory that can be managed.

Returns

Success or error status. Error::kInvalidSize if size is invalid.

expected_t<int32_t> acquire(int32_t size)

Acquire a contiguous block of memory of the specified size.

If such a contiguous block exists, returns the lowest index where the block starts. This block will be marked as allocated until a call to release() is made.

Parameters

size – Size of the memory block to acquire.

Returns

Index of the allocated block on success, Error::kOutOfMemory if no suitable block exists.

expected_t<void> release(int32_t index)

Release a previously acquired block of memory.

The block must have been previously acquired using acquire(). Once released, the memory becomes available for future allocations.

Parameters

index – Starting index of the block to release.

Returns

Success or error status. Error::kBlockNotAllocated if the block was not previously allocated.