path: root/src/asmjit/core/zone.h

// AsmJit - Machine code generation for C++
//
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#ifndef ASMJIT_CORE_ZONE_H_INCLUDED
#define ASMJIT_CORE_ZONE_H_INCLUDED

#include "../core/support.h"

ASMJIT_BEGIN_NAMESPACE

//! \addtogroup asmjit_zone
//! \{

// ============================================================================
// [asmjit::Zone]
// ============================================================================

//! Zone memory.
//!
//! Zone is an incremental memory allocator that allocates memory by simply
//! incrementing a pointer. It allocates blocks of memory by using C's `malloc()`,
//! but divides these blocks into smaller segments requested by calling
//! `Zone::alloc()` and friends.
//!
//! Zone has no function to release the allocated memory. It has to be released
//! all at once by calling `reset()`. If you need a more friendly allocator that
//! also supports `release()`, consider using `Zone` with `ZoneAllocator`.
class Zone {
public:
  ASMJIT_NONCOPYABLE(Zone)

  //! \cond INTERNAL

  //! A single block of memory managed by `Zone`.
  struct Block {
    inline uint8_t* data() const noexcept {
      return const_cast<uint8_t*>(reinterpret_cast<const uint8_t*>(this) + sizeof(*this));
    }

    //! Link to the previous block.
    Block* prev;
    //! Link to the next block.
    Block* next;
    //! Size of the block.
    size_t size;
  };

  enum Limits : size_t {
    kBlockSize = sizeof(Block),
    kBlockOverhead = Globals::kAllocOverhead + kBlockSize,

    kMinBlockSize = 64, // The number is ridiculously small, but still possible.
    kMaxBlockSize = size_t(1) << (sizeof(size_t) * 8 - 4 - 1),
    kMinAlignment = 1,
    kMaxAlignment = 64
  };

  //! Pointer in the current block.
  uint8_t* _ptr;
  //! End of the current block.
  uint8_t* _end;
  //! Current block.
  Block* _block;

  union {
    struct {
      //! Default block size.
      size_t _blockSize : Support::bitSizeOf<size_t>() - 4;
      //! First block is temporary (ZoneTmp).
      size_t _isTemporary : 1;
      //! Block alignment (1 << alignment).
      size_t _blockAlignmentShift : 3;
    };
    size_t _packedData;
  };

  static ASMJIT_API const Block _zeroBlock;

  //! \endcond

  //! \name Construction & Destruction
  //! \{

  //! Creates a new Zone.
  //!
  //! The `blockSize` parameter describes the default size of the block. If the
  //! `size` parameter passed to `alloc()` is greater than the default size
  //! `Zone` will allocate and use a larger block, but it will not change the
  //! default `blockSize`.
  //!
  //! It's not required, but it's good practice to set `blockSize` to a
  //! reasonable value that depends on the usage of `Zone`. Greater block sizes
  //! are generally safer and perform better than unreasonably low block sizes.
  ASMJIT_INLINE explicit Zone(size_t blockSize, size_t blockAlignment = 1) noexcept {
    _init(blockSize, blockAlignment, nullptr);
  }

  ASMJIT_INLINE Zone(size_t blockSize, size_t blockAlignment, const Support::Temporary& temporary) noexcept {
    _init(blockSize, blockAlignment, &temporary);
  }

  //! Moves an existing `Zone`.
  //!
  //! \note You cannot move an existing `ZoneTmp` as it uses embedded storage.
  //! Attempting to move `ZoneTmp` would result in assertion failure in debug
  //! mode and undefined behavior in release mode.
  ASMJIT_INLINE Zone(Zone&& other) noexcept
    : _ptr(other._ptr),
      _end(other._end),
      _block(other._block),
      _packedData(other._packedData) {
    ASMJIT_ASSERT(!other.isTemporary());
    other._block = const_cast<Block*>(&_zeroBlock);
    other._ptr = other._block->data();
    other._end = other._block->data();
  }

  //! Destroys the `Zone` instance.
  //!
  //! This will destroy the `Zone` instance and release all blocks of memory
  //! allocated by it. It performs implicit `reset(Globals::kResetHard)`.
  ASMJIT_INLINE ~Zone() noexcept { reset(Globals::kResetHard); }

  ASMJIT_API void _init(size_t blockSize, size_t blockAlignment, const Support::Temporary* temporary) noexcept;

  //! Resets the `Zone` invalidating all blocks allocated.
  //!
  //! See `Globals::ResetPolicy` for more details.
  ASMJIT_API void reset(uint32_t resetPolicy = Globals::kResetSoft) noexcept;

  //! \}

  //! \name Accessors
  //! \{

  //! Tests whether this `Zone` is actually a `ZoneTmp` that uses temporary memory.
  ASMJIT_INLINE bool isTemporary() const noexcept { return _isTemporary != 0; }

  //! Returns the default block size.
  ASMJIT_INLINE size_t blockSize() const noexcept { return _blockSize; }
  //! Returns the default block alignment.
  ASMJIT_INLINE size_t blockAlignment() const noexcept { return size_t(1) << _blockAlignmentShift; }
  //! Returns remaining size of the current block.
  ASMJIT_INLINE size_t remainingSize() const noexcept { return (size_t)(_end - _ptr); }

  //! Returns the current zone cursor (dangerous).
  //!
  //! This is a function that can be used to get exclusive access to the current
  //! block's memory buffer.
  template<typename T = uint8_t>
  ASMJIT_INLINE T* ptr() noexcept { return reinterpret_cast<T*>(_ptr); }

  //! Returns the end of the current zone block, only useful if you use `ptr()`.
  template<typename T = uint8_t>
  ASMJIT_INLINE T* end() noexcept { return reinterpret_cast<T*>(_end); }

  //! Sets the current zone pointer to `ptr` (must be within the current block).
  template<typename T>
  ASMJIT_INLINE void setPtr(T* ptr) noexcept {
    uint8_t* p = reinterpret_cast<uint8_t*>(ptr);
    ASMJIT_ASSERT(p >= _ptr && p <= _end);
    _ptr = p;
  }

  //! Sets the end zone pointer to `end` (must be within the current block).
  template<typename T>
  ASMJIT_INLINE void setEnd(T* end) noexcept {
    uint8_t* p = reinterpret_cast<uint8_t*>(end);
    ASMJIT_ASSERT(p >= _ptr && p <= _end);
    _end = p;
  }

  //! \}

  //! \name Utilities
  //! \{

  ASMJIT_INLINE void swap(Zone& other) noexcept {
    // This could lead to a disaster.
    ASMJIT_ASSERT(!this->isTemporary());
    ASMJIT_ASSERT(!other.isTemporary());

    std::swap(_ptr, other._ptr);
    std::swap(_end, other._end);
    std::swap(_block, other._block);
    std::swap(_packedData, other._packedData);
  }

  //! Aligns the current pointer to `alignment`.
  ASMJIT_INLINE void align(size_t alignment) noexcept {
    _ptr = Support::min(Support::alignUp(_ptr, alignment), _end);
  }

  //! Ensures the remaining size is at least equal or greater than `size`.
  //!
  //! \note This function doesn't respect any alignment. If you need to ensure
  //! there is enough room for an aligned allocation you need to call `align()`
  //! before calling `ensure()`.
  ASMJIT_INLINE Error ensure(size_t size) noexcept {
    if (size <= remainingSize())
      return kErrorOk;
    else
      return _alloc(0, 1) ? kErrorOk : DebugUtils::errored(kErrorOutOfMemory);
  }

  ASMJIT_INLINE void _assignBlock(Block* block) noexcept {
    size_t alignment = blockAlignment();
    _ptr = Support::alignUp(block->data(), alignment);
    _end = Support::alignDown(block->data() + block->size, alignment);
    _block = block;
  }

  ASMJIT_INLINE void _assignZeroBlock() noexcept {
    Block* block = const_cast<Block*>(&_zeroBlock);
    _ptr = block->data();
    _end = block->data();
    _block = block;
  }

  //! \}

  //! \name Allocation
  //! \{

  //! Allocates the requested memory specified by `size`.
  //!
  //! Pointer returned is valid until the `Zone` instance is destroyed or reset
  //! by calling `reset()`. If you plan to make an instance of C++ from the
  //! given pointer use placement `new` and `delete` operators:
  //!
  //! ```
  //! using namespace asmjit;
  //!
  //! class Object { ... };
  //!
  //! // Create Zone with default block size of approximately 65536 bytes.
  //! Zone zone(65536 - Zone::kBlockOverhead);
  //!
  //! // Create your objects using zone object allocating, for example:
  //! Object* obj = static_cast<Object*>( zone.alloc(sizeof(Object)) );
  //!
  //! if (!obj) {
  //!   // Handle out of memory error.
  //! }
  //!
  //! // Placement `new` and `delete` operators can be used to instantiate it.
  //! new(obj) Object();
  //!
  //! // ... lifetime of your objects ...
  //!
  //! // To destroy the instance (if required).
  //! obj->~Object();
  //!
  //! // Reset or destroy `Zone`.
  //! zone.reset();
  //! ```
  ASMJIT_INLINE void* alloc(size_t size) noexcept {
    if (ASMJIT_UNLIKELY(size > remainingSize()))
      return _alloc(size, 1);

    uint8_t* ptr = _ptr;
    _ptr += size;
    return static_cast<void*>(ptr);
  }

  //! Allocates the requested memory specified by `size` and `alignment`.
  ASMJIT_INLINE void* alloc(size_t size, size_t alignment) noexcept {
    ASMJIT_ASSERT(Support::isPowerOf2(alignment));
    uint8_t* ptr = Support::alignUp(_ptr, alignment);

    if (ptr >= _end || size > (size_t)(_end - ptr))
      return _alloc(size, alignment);

    _ptr = ptr + size;
    return static_cast<void*>(ptr);
  }

  //! Allocates the requested memory specified by `size` without doing any checks.
  //!
  //! Can only be called if `remainingSize()` returns size at least equal to `size`.
  ASMJIT_INLINE void* allocNoCheck(size_t size) noexcept {
    ASMJIT_ASSERT(remainingSize() >= size);

    uint8_t* ptr = _ptr;
    _ptr += size;
    return static_cast<void*>(ptr);
  }

  //! Allocates the requested memory specified by `size` and `alignment` without doing any checks.
  //!
  //! Performs the same operation as `Zone::allocNoCheck(size)` with `alignment` applied.
  ASMJIT_INLINE void* allocNoCheck(size_t size, size_t alignment) noexcept {
    ASMJIT_ASSERT(Support::isPowerOf2(alignment));

    uint8_t* ptr = Support::alignUp(_ptr, alignment);
    ASMJIT_ASSERT(size <= (size_t)(_end - ptr));

    _ptr = ptr + size;
    return static_cast<void*>(ptr);
  }

  //! Allocates `size` bytes of zeroed memory. See `alloc()` for more details.
  ASMJIT_API void* allocZeroed(size_t size, size_t alignment = 1) noexcept;

  //! Like `alloc()`, but the return pointer is casted to `T*`.
  template<typename T>
  ASMJIT_INLINE T* allocT(size_t size = sizeof(T), size_t alignment = alignof(T)) noexcept {
    return static_cast<T*>(alloc(size, alignment));
  }

  //! Like `allocNoCheck()`, but the return pointer is casted to `T*`.
  template<typename T>
  ASMJIT_INLINE T* allocNoCheckT(size_t size = sizeof(T), size_t alignment = alignof(T)) noexcept {
    return static_cast<T*>(allocNoCheck(size, alignment));
  }

  //! Like `allocZeroed()`, but the return pointer is casted to `T*`.
  template<typename T>
  ASMJIT_INLINE T* allocZeroedT(size_t size = sizeof(T), size_t alignment = alignof(T)) noexcept {
    return static_cast<T*>(allocZeroed(size, alignment));
  }

  //! Like `new(std::nothrow) T(...)`, but allocated by `Zone`.
  template<typename T>
  ASMJIT_INLINE T* newT() noexcept {
    void* p = alloc(sizeof(T), alignof(T));
    if (ASMJIT_UNLIKELY(!p))
      return nullptr;
    return new(p) T();
  }

  //! Like `new(std::nothrow) T(...)`, but allocated by `Zone`.
  template<typename T, typename... Args>
  ASMJIT_INLINE T* newT(Args&&... args) noexcept {
    void* p = alloc(sizeof(T), alignof(T));
    if (ASMJIT_UNLIKELY(!p))
      return nullptr;
    return new(p) T(std::forward<Args>(args)...);
  }

  //! \cond INTERNAL
  //!
  //! Internal alloc function used by other inlines.
  ASMJIT_API void* _alloc(size_t size, size_t alignment) noexcept;
  //! \endcond

  //! Helper to duplicate data.
  ASMJIT_API void* dup(const void* data, size_t size, bool nullTerminate = false) noexcept;

  //! Helper to duplicate data.
  ASMJIT_INLINE void* dupAligned(const void* data, size_t size, size_t alignment, bool nullTerminate = false) noexcept {
    align(alignment);
    return dup(data, size, nullTerminate);
  }

  //! Helper to duplicate a formatted string, maximum size is 256 bytes.
  ASMJIT_API char* sformat(const char* str, ...) noexcept;

  //! \}
};

// ============================================================================
// [b2d::ZoneTmp]
// ============================================================================

//! \ref Zone with `N` bytes of a static storage, used for the initial block.
//!
//! Temporary zones are used in cases where it's known that some memory will be
//! required, but in many cases it won't exceed N bytes, so the whole operation
//! can be performed without a dynamic memory allocation.
template<size_t N>
class ZoneTmp : public Zone {
public:
  ASMJIT_NONCOPYABLE(ZoneTmp)

  //! Temporary storage, embedded after \ref Zone.
  struct Storage {
    char data[N];
  } _storage;

  //! Creates a temporary zone. Dynamic block size is specified by `blockSize`.
  ASMJIT_INLINE explicit ZoneTmp(size_t blockSize, size_t blockAlignment = 1) noexcept
    : Zone(blockSize, blockAlignment, Support::Temporary(_storage.data, N)) {}
};

// ============================================================================
// [asmjit::ZoneAllocator]
// ============================================================================

//! Zone-based memory allocator that uses an existing `Zone` and provides a
//! `release()` functionality on top of it. It uses `Zone` only for chunks
//! that can be pooled, and uses libc `malloc()` for chunks that are large.
//!
//! The advantage of ZoneAllocator is that it can allocate small chunks of memory
//! really fast, and these chunks, when released, will be reused by consecutive
//! calls to `alloc()`. Also, since ZoneAllocator uses `Zone`, you can turn any
//! `Zone` into a `ZoneAllocator`, and use it in your `Pass` when necessary.
//!
//! ZoneAllocator is used by AsmJit containers to make containers having only
//! few elements fast (and lightweight) and to allow them to grow and use
//! dynamic blocks when require more storage.
class ZoneAllocator {
public:
  ASMJIT_NONCOPYABLE(ZoneAllocator)

  //! \cond INTERNAL
  enum {
    // In short, we pool chunks of these sizes:
    //   [32, 64, 96, 128, 192, 256, 320, 384, 448, 512]

    //! How many bytes per a low granularity pool (has to be at least 16).
    kLoGranularity = 32,
    //! Number of slots of a low granularity pool.
    kLoCount = 4,
    //! Maximum size of a block that can be allocated in a low granularity pool.
    kLoMaxSize = kLoGranularity * kLoCount,

    //! How many bytes per a high granularity pool.
    kHiGranularity = 64,
    //! Number of slots of a high granularity pool.
    kHiCount = 6,
    //! Maximum size of a block that can be allocated in a high granularity pool.
    kHiMaxSize = kLoMaxSize + kHiGranularity * kHiCount,

    //! Alignment of every pointer returned by `alloc()`.
    kBlockAlignment = kLoGranularity
  };

  //! Single-linked list used to store unused chunks.
  struct Slot {
    //! Link to a next slot in a single-linked list.
    Slot* next;
  };

  //! A block of memory that has been allocated dynamically and is not part of
  //! block-list used by the allocator. This is used to keep track of all these
  //! blocks so they can be freed by `reset()` if not freed explicitly.
  struct DynamicBlock {
    DynamicBlock* prev;
    DynamicBlock* next;
  };

  //! \endcond

  //! Zone used to allocate memory that fits into slots.
  Zone* _zone;
  //! Indexed slots containing released memory.
  Slot* _slots[kLoCount + kHiCount];
  //! Dynamic blocks for larger allocations (no slots).
  DynamicBlock* _dynamicBlocks;

  //! \name Construction & Destruction
  //! \{

  //! Creates a new `ZoneAllocator`.
  //!
  //! \note To use it, you must first `init()` it.
  inline ZoneAllocator() noexcept {
    memset(this, 0, sizeof(*this));
  }

  //! Creates a new `ZoneAllocator` initialized to use `zone`.
  inline explicit ZoneAllocator(Zone* zone) noexcept {
    memset(this, 0, sizeof(*this));
    _zone = zone;
  }

  //! Destroys the `ZoneAllocator`.
  inline ~ZoneAllocator() noexcept { reset(); }

  //! Tests whether the `ZoneAllocator` is initialized (i.e. has `Zone`).
  inline bool isInitialized() const noexcept { return _zone != nullptr; }

  //! Convenience function to initialize the `ZoneAllocator` with `zone`.
  //!
  //! It's the same as calling `reset(zone)`.
  inline void init(Zone* zone) noexcept { reset(zone); }

  //! Resets this `ZoneAllocator` and also forget about the current `Zone` which
  //! is attached (if any). Reset optionally attaches a new `zone` passed, or
  //! keeps the `ZoneAllocator` in an uninitialized state, if `zone` is null.
  ASMJIT_API void reset(Zone* zone = nullptr) noexcept;

  //! \}

  //! \name Accessors
  //! \{

  //! Returns the assigned `Zone` of this allocator or null if this `ZoneAllocator`
  //! is not initialized.
  inline Zone* zone() const noexcept { return _zone; }

  //! \}

  //! \cond
  //! \name Internals
  //! \{

  //! Returns the slot index to be used for `size`. Returns `true` if a valid slot
  //! has been written to `slot` and `allocatedSize` has been filled with slot
  //! exact size (`allocatedSize` can be equal or slightly greater than `size`).
  static ASMJIT_INLINE bool _getSlotIndex(size_t size, uint32_t& slot) noexcept {
    ASMJIT_ASSERT(size > 0);
    if (size > kHiMaxSize)
      return false;

    if (size <= kLoMaxSize)
      slot = uint32_t((size - 1) / kLoGranularity);
    else
      slot = uint32_t((size - kLoMaxSize - 1) / kHiGranularity) + kLoCount;

    return true;
  }

  //! \overload
  static ASMJIT_INLINE bool _getSlotIndex(size_t size, uint32_t& slot, size_t& allocatedSize) noexcept {
    ASMJIT_ASSERT(size > 0);
    if (size > kHiMaxSize)
      return false;

    if (size <= kLoMaxSize) {
      slot = uint32_t((size - 1) / kLoGranularity);
      allocatedSize = Support::alignUp(size, kLoGranularity);
    }
    else {
      slot = uint32_t((size - kLoMaxSize - 1) / kHiGranularity) + kLoCount;
      allocatedSize = Support::alignUp(size, kHiGranularity);
    }

    return true;
  }

  //! \}
  //! \endcond

  //! \name Allocation
  //! \{

  //! \cond INTERNAL
  ASMJIT_API void* _alloc(size_t size, size_t& allocatedSize) noexcept;
  ASMJIT_API void* _allocZeroed(size_t size, size_t& allocatedSize) noexcept;
  ASMJIT_API void _releaseDynamic(void* p, size_t size) noexcept;
  //! \endcond

  //! Allocates `size` bytes of memory, ideally from an available pool.
  //!
  //! \note `size` can't be zero, it will assert in debug mode in such case.
  inline void* alloc(size_t size) noexcept {
    ASMJIT_ASSERT(isInitialized());
    size_t allocatedSize;
    return _alloc(size, allocatedSize);
  }

  //! Like `alloc(size)`, but provides a second argument `allocatedSize` that
  //! provides a way to know how big the block returned actually is. This is
  //! useful for containers to prevent growing too early.
  inline void* alloc(size_t size, size_t& allocatedSize) noexcept {
    ASMJIT_ASSERT(isInitialized());
    return _alloc(size, allocatedSize);
  }

  //! Like `alloc()`, but the return pointer is casted to `T*`.
  template<typename T>
  inline T* allocT(size_t size = sizeof(T)) noexcept {
    return static_cast<T*>(alloc(size));
  }

  //! Like `alloc(size)`, but returns zeroed memory.
  inline void* allocZeroed(size_t size) noexcept {
    ASMJIT_ASSERT(isInitialized());
    size_t allocatedSize;
    return _allocZeroed(size, allocatedSize);
  }

  //! Like `alloc(size, allocatedSize)`, but returns zeroed memory.
  inline void* allocZeroed(size_t size, size_t& allocatedSize) noexcept {
    ASMJIT_ASSERT(isInitialized());
    return _allocZeroed(size, allocatedSize);
  }

  //! Like `allocZeroed()`, but the return pointer is casted to `T*`.
  template<typename T>
  inline T* allocZeroedT(size_t size = sizeof(T)) noexcept {
    return static_cast<T*>(allocZeroed(size));
  }

  //! Like `new(std::nothrow) T(...)`, but allocated by `Zone`.
  template<typename T>
  inline T* newT() noexcept {
    void* p = allocT<T>();
    if (ASMJIT_UNLIKELY(!p))
      return nullptr;
    return new(p) T();
  }
  //! Like `new(std::nothrow) T(...)`, but allocated by `Zone`.
  template<typename T, typename... Args>
  inline T* newT(Args&&... args) noexcept {
    void* p = allocT<T>();
    if (ASMJIT_UNLIKELY(!p))
      return nullptr;
    return new(p) T(std::forward<Args>(args)...);
  }

  //! Releases the memory previously allocated by `alloc()`. The `size` argument
  //! has to be the same as used to call `alloc()` or `allocatedSize` returned
  //! by `alloc()`.
  inline void release(void* p, size_t size) noexcept {
    ASMJIT_ASSERT(isInitialized());
    ASMJIT_ASSERT(p != nullptr);
    ASMJIT_ASSERT(size != 0);

    uint32_t slot;
    if (_getSlotIndex(size, slot)) {
      static_cast<Slot*>(p)->next = static_cast<Slot*>(_slots[slot]);
      _slots[slot] = static_cast<Slot*>(p);
    }
    else {
      _releaseDynamic(p, size);
    }
  }

  //! \}
};

//! \}

ASMJIT_END_NAMESPACE

#endif // ASMJIT_CORE_ZONE_H_INCLUDED