NAME

       ost::MemPager - The memory pager is used to allocate cumulative memory pages for storing
       object specific 'persistant' data that is presumed to persist during the life of a given
       derived object.

SYNOPSIS

       #include <misc.h>

       Inherited by ost::Keydata [protected], ost::SharedMemPager, and ost::StackPager
       [protected].

   Public Member Functions
       int getPages (void)
           Return the total number of pages that have been allocated for this memory pool.

   Protected Member Functions
       virtual void * first (size_t size)
           Allocate first workspace from paged memory.
       virtual void * alloc (size_t size)
           Allocate memory from either the currently active page, or allocate a new page for the
           object.
       char * first (char *str)
           Allocate a string from the memory pager pool and copy the string into it's new memory
           area.
       char * alloc (const char *str)
           Allocate a string from the memory pager pool and copy the string inti it's new memory
           area.
       MemPager (size_t pagesize=4096)
           Create a paged memory pool for cumulative storage.
       void purge (void)
           purge the current memory pool.
       void clean (void)
           Clean for memory cleanup before exiting.
       virtual ~MemPager ()
           Delete the memory pool and all allocated memory.

   Friends
       class String
       class MemPagerObject

Detailed Description

       The memory pager is used to allocate cumulative memory pages for storing object specific
       'persistant' data that is presumed to persist during the life of a given derived object.

       When the object is destroyed, all accumulated data is automatically purged.

       There are a number of odd and specialized utility classes found in Common C++. The most
       common of these is the 'MemPager' class. This is basically a class to enable page-grouped
       'cumulative' memory allocation; all accumulated allocations are dropped during the
       destructor. This class has found it's way in a lot of other utility classes in Common C++.

       Author:
           David Sugar dyfet@ostel.com Accumulative object memory allocator.

Constructor & Destructor Documentation

   ost::MemPager::MemPager (size_t pagesize = 4096) [protected]
       Create a paged memory pool for cumulative storage. This pool allocates memory in fixed
       'pagesize' chunks. Ideal performance is achived when the pool size matches the system page
       size. This pool can only exist in derived objects.

       Parameters:
           pagesize page size to allocate chunks.

   virtual ost::MemPager::~MemPager () [protected],  [virtual]
       Delete the memory pool and all allocated memory.

Member Function Documentation

   virtual void* ost::MemPager::alloc (size_t size) [protected],  [virtual]
       Allocate memory from either the currently active page, or allocate a new page for the
       object.

       Parameters:
           size size of memory to allocate.

       Returns:
           pointer to allocated memory.

       Reimplemented in ost::SharedMemPager.

   char* ost::MemPager::alloc (const char * str) [protected]
       Allocate a string from the memory pager pool and copy the string inti it's new memory
       area. This checks only the last active page for available space before allocating a new
       page.

       Parameters:
           str string to allocate and copy into paged memory pool.

       Returns:
           copy of string from allocated memory.

   void ost::MemPager::clean (void) [protected]
       Clean for memory cleanup before exiting.

   virtual void* ost::MemPager::first (size_t size) [protected],  [virtual]
       Allocate first workspace from paged memory. This method scans all currently allocated
       blocks for available space before adding new pages and hence is both slower and more
       efficient.

       Parameters:
           size size of memory to allocate.

       Returns:
           pointer to allocated memory.

       Reimplemented in ost::SharedMemPager.

   char* ost::MemPager::first (char * str) [protected]
       Allocate a string from the memory pager pool and copy the string into it's new memory
       area. This method allocates memory by first searching for an available page, and then
       allocating a new page if no space is found.

       Parameters:
           str string to allocate and copy into paged memory pool.

       Returns:
           copy of string from allocated memory.

   int ost::MemPager::getPages (void) [inline]
       Return the total number of pages that have been allocated for this memory pool.

       Returns:
           number of pages allocated.

   void ost::MemPager::purge (void) [protected]
       purge the current memory pool.

Friends And Related Function Documentation

   friend class MemPagerObject [friend]
   friend class String [friend]

Author

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