src/ipc/mem/PagePool.h

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