core.memory - D Programming Language - Digital Mars

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Last update Wed Sep 2 00:11:54 2009

# core.memory

$(DDOC_SECTIONS The memory module provides an interface to the garbage collector and to any other OS or API-level memory management facilities.

$(DDOC_LICENSE struct GC;
  This struct encapsulates all garbage collection functionality for the D programming language.

  static void enable();
    Enables automatic garbage collection behavior if collections have previously been suspended by a call to disable. This function is reentrant, and must be called once for every call to disable before automatic collections are enabled.

  static void disable();
    Disables automatic garbage collections performed to minimize the process footprint. Collections may continue to occur in instances where the implementation deems necessary for correct program behavior, such as during an out of memory condition. This function is reentrant, but enable must be called once for each call to disable.

  static void collect();
    Begins a full collection. While the meaning of this may change based on the garbage collector implementation, typical behavior is to scan all stack segments for roots, mark accessible memory blocks as alive, and then to reclaim free space. This action may need to suspend all running threads for at least part of the collection process.

  static void minimize();
    Indicates that the managed memory space be minimized by returning free physical memory to the operating system. The amount of free memory returned depends on the allocator design and on program behavior.

  enum BlkAttr;
    Elements for a bit field representing memory block attributes. These are manipulated via the getAttr, setAttr, clrAttr functions.

    FINALIZE
      Finalize the data in this block on collect.

    NO_SCAN
      Do not scan through this block on collect.

    NO_MOVE
      Do not move this memory block on collect.

  alias BlkInfo;
    Contains aggregate information about a block of managed memory. The purpose of this struct is to support a more efficient query style in instances where detailed information is needed.

    base = A pointer to the base of the block in question. size = The size of the block, calculated from base. attr = Attribute bits set on the memory block.

  static uint getAttr(void* p);
    Returns a bit field representing all block attributes set for the memory referenced by p. If p references memory not originally allocated by this garbage collector, points to the interior of a memory block, or if p is null, zero will be returned.

    Parameters:

    void* p | A pointer to the root of a valid memory block or to null.

    Returns:
    A bit field containing any bits set for the memory block referenced by p or zero on error.

  static uint setAttr(void* p, uint a);
    Sets the specified bits for the memory references by p. If p references memory not originally allocated by this garbage collector, points to the interior of a memory block, or if p is null, no action will be performed.

    Parameters:

    void* p | A pointer to the root of a valid memory block or to null.
    uint a | A bit field containing any bits to set for this memory block. The result of a call to getAttr after the specified bits have been set.

  static uint clrAttr(void* p, uint a);
    Clears the specified bits for the memory references by p. If p references memory not originally allocated by this garbage collector, points to the interior of a memory block, or if p is null, no action will be performed.

    Parameters:

    void* p | A pointer to the root of a valid memory block or to null.
    uint a | A bit field containing any bits to clear for this memory block.

    Returns:
    The result of a call to getAttr after the specified bits have been cleared.

  static void* malloc(size_t sz, uint ba = 0);
    Requests an aligned block of managed memory from the garbage collector. This memory may be deleted at will with a call to free, or it may be discarded and cleaned up automatically during a collection run. If allocation fails, this function will call onOutOfMemory which is expected to throw an OutOfMemoryException.

    Parameters:

    size_t sz | The desired allocation size in bytes.
    uint ba | A bitmask of the attributes to set on this block.

    Returns:
    A reference to the allocated memory or null if insufficient memory is available.

    Throws:
    OutOfMemoryException on allocation failure.

  static void* calloc(size_t sz, uint ba = 0);
    Requests an aligned block of managed memory from the garbage collector, which is initialized with all bits set to zero. This memory may be deleted at will with a call to free, or it may be discarded and cleaned up automatically during a collection run. If allocation fails, this function will call onOutOfMemory which is expected to throw an OutOfMemoryException.

    Parameters:

    size_t sz | The desired allocation size in bytes.
    uint ba | A bitmask of the attributes to set on this block.

    Returns:
    A reference to the allocated memory or null if insufficient memory is available.

    Throws:
    OutOfMemoryException on allocation failure.

  static void* realloc(void* p, size_t sz, uint ba = 0);
    If sz is zero, the memory referenced by p will be deallocated as if by a call to free. A new memory block of size sz will then be allocated as if by a call to malloc, or the implementation may instead resize the memory block in place. The contents of the new memory block will be the same as the contents of the old memory block, up to the lesser of the new and old sizes. Note that existing memory will only be freed by realloc if sz is equal to zero. The garbage collector is otherwise expected to later reclaim the memory block if it is unused. If allocation fails, this function will call onOutOfMemory which is expected to throw an OutOfMemoryException. If p references memory not originally allocated by this garbage collector, or if it points to the interior of a memory block, no action will be taken. If ba is zero (the default) and p references the head of a valid, known memory block then any bits set on the current block will be set on the new block if a reallocation is required. If ba is not zero and p references the head of a valid, known memory block then the bits in ba will replace those on the current memory block and will also be set on the new block if a reallocation is required.

    Parameters:

    void* p | A pointer to the root of a valid memory block or to null.
    size_t sz | The desired allocation size in bytes.
    uint ba | A bitmask of the attributes to set on this block.

    Returns:
    A reference to the allocated memory on success or null if sz is zero. On failure, the original value of p is returned.

    Throws:
    OutOfMemoryException on allocation failure.

  static size_t extend(void* p, size_t mx, size_t sz);
    Requests that the managed memory block referenced by p be extended in place by at least mx bytes, with a desired extension of sz bytes. If an extension of the required size is not possible, if p references memory not originally allocated by this garbage collector, or if p points to the interior of a memory block, no action will be taken.

    Parameters:

    size_t mx | The minimum extension size in bytes.
    size_t sz | The desired extension size in bytes.

    Returns:
    The size in bytes of the extended memory block referenced by p or zero if no extension occurred.

  static size_t reserve(size_t sz);
    Requests that at least sz bytes of memory be obtained from the operating system and marked as free.

    Parameters:

    size_t sz | The desired size in bytes.

    Returns:
    The actual number of bytes reserved or zero on error.

  static void free(void* p);
    Deallocates the memory referenced by p. If p is null, no action occurs. If p references memory not originally allocated by this garbage collector, or if it points to the interior of a memory block, no action will be taken. The block will not be finalized regardless of whether the FINALIZE attribute is set. If finalization is desired, use delete instead.

    Parameters:

    void* p | A pointer to the root of a valid memory block or to null.

  static void* addrOf(void* p);
    Returns the base address of the memory block containing p. This value is useful to determine whether p is an interior pointer, and the result may be passed to routines such as sizeOf which may otherwise fail. If p references memory not originally allocated by this garbage collector, if p is null, or if the garbage collector does not support this operation, null will be returned.

    Parameters:

    void* p | A pointer to the root or the interior of a valid memory block or to null.

    Returns:
    The base address of the memory block referenced by p or null on error.

  static size_t sizeOf(void* p);
    Returns the true size of the memory block referenced by p. This value represents the maximum number of bytes for which a call to realloc may resize the existing block in place. If p references memory not originally allocated by this garbage collector, points to the interior of a memory block, or if p is null, zero will be returned.

    Parameters:

    void* p | A pointer to the root of a valid memory block or to null.

    Returns:
    The size in bytes of the memory block referenced by p or zero on error.

  static BlkInfo query(void* p);
    Returns aggregate information about the memory block containing p. If p references memory not originally allocated by this garbage collector, if p is null, or if the garbage collector does not support this operation, BlkInfo.init will be returned. Typically, support for this operation is dependent on support for addrOf.

    Parameters:

    void* p | A pointer to the root or the interior of a valid memory block or to null.

    Returns:
    Information regarding the memory block referenced by p or BlkInfo.init on error.

  static void addRoot(void* p);
    Adds the memory address referenced by p to an internal list of roots to be scanned during a collection. If p is null, no operation is performed.

    Parameters:

    void* p | A pointer to a valid memory address or to null.

  static void addRange(void* p, size_t sz);
    Adds the memory block referenced by p and of size sz to an internal list of ranges to be scanned during a collection. If p is null, no operation is performed.

    Parameters:

    void* p | A pointer to a valid memory address or to null.
    size_t sz | The size in bytes of the block to add. If sz is zero then the no operation will occur. If p is null then sz must be zero.

  static void removeRoot(void* p);
    Removes the memory block referenced by p from an internal list of roots to be scanned during a collection. If p is null or does not represent a value previously passed to add(void*) then no operation is performed.

    p = A pointer to a valid memory address or to null.

  static void removeRange(void* p);
    Removes the memory block referenced by p from an internal list of ranges to be scanned during a collection. If p is null or does not represent a value previously passed to add(void*, size_t) then no operation is performed.

    Parameters:

    void* p | A pointer to a valid memory address or to null.

Copyright Sean Kelly 2005 - 2009. | Page generated by Ddoc.