src/ipc/mem/PagePool.h

   1 /*
   2  * $Id$
   3  *
   4  */
   5
   6 #ifndef SQUID_IPC_MEM_PAGE_POOL_H
   7 #define SQUID_IPC_MEM_PAGE_POOL_H
   8
   9 #include "ipc/mem/Page.h"
  10 #include "ipc/mem/PageStack.h"
  11 #include "ipc/mem/Pointer.h"
  12
  13 namespace Ipc {
  14
  15 namespace Mem {
  16
  17 /// Atomic container of shared memory pages. Implemented using a collection of
  18 /// Segments, each with a PageStack index of free pages. All pools must be
  19 /// created by a single process.
  20 class PagePool {
  21 public:
  22     typedef Ipc::Mem::Owner<PageStack> Owner;
  23
  24     static Owner *Init(const char *const id, const unsigned int capacity, const size_t pageSize);
  25
  26     PagePool(const char *const id);
  27
  28     unsigned int capacity() const { return pageIndex->capacity(); }
  29     size_t pageSize() const { return pageIndex->pageSize(); }
  30     /// lower bound for the number of free pages
  31     unsigned int size() const { return pageIndex->size(); }
  32     /// approximate number of shared memory pages used now
  33     size_t level() const { return capacity() - size(); }
  34     /// approximate number of shared memory pages used now for given purpose
  35     size_t level(const int purpose) const;
  36
  37     /// sets page ID and returns true unless no free pages are found
  38     bool get(const PageId::Purpose purpose, PageId &page);
  39     /// makes identified page available as a free page to future get() callers
  40     void put(PageId &page);
  41     /// converts page handler into a temporary writeable shared memory pointer
  42     char *pagePointer(const PageId &page);
  43
  44 private:
  45     Ipc::Mem::Pointer<PageStack> pageIndex; ///< free pages index
  46     /// number of shared memory pages used now for each purpose
  47     AtomicWord *const theLevels;
  48     char *const theBuf; ///< pages storage
  49 };
  50
  51 } // namespace Mem
  52
  53 } // namespace Ipc
  54
  55 #endif // SQUID_IPC_MEM_PAGE_POOL_H