src/ipc/mem/PagePool.cc

   1 /*
   2  * $Id$
   3  *
   4  * DEBUG: section 54    Interprocess Communication
   5  *
   6  */
   7
   8 #include "config.h"
   9 #include "base/TextException.h"
  10 #include "ipc/mem/Page.h"
  11 #include "ipc/mem/PagePool.h"
  12
  13
  14 static String
  15 PageIndexId(String id)
  16 {
  17     id.append("-index");
  18     return id;
  19 }
  20
  21
  22 // Ipc::Mem::PagePool
  23
  24 Ipc::Mem::PagePool::PagePool(const String &id, const unsigned int capacity, const size_t pageSize):
  25     pageIndex(PageIndexId(id), capacity),
  26     shm(id.termedBuf())
  27 {
  28     shm.create(sizeof(Shared) + pageSize*capacity);
  29     assert(shm.mem());
  30     shared = new (shm.mem()) Shared(capacity, pageSize);
  31 }
  32
  33 Ipc::Mem::PagePool::PagePool(const String &id):
  34     pageIndex(PageIndexId(id)), shm(id.termedBuf())
  35 {
  36     shm.open();
  37     shared = reinterpret_cast<Shared *>(shm.mem());
  38     assert(shared);
  39 }
  40
  41 bool
  42 Ipc::Mem::PagePool::get(PageId &page)
  43 {
  44     if (pageIndex.pop(page.number)) {
  45         page.pool = shared->theId;
  46         return true;
  47     }
  48     return false;
  49 }
  50
  51 void
  52 Ipc::Mem::PagePool::put(PageId &page)
  53 {
  54     Must(pageIdIsValid(page));
  55     pageIndex.push(page.number);
  56     page = PageId();
  57 }
  58
  59 void *
  60 Ipc::Mem::PagePool::pagePointer(const PageId &page)
  61 {
  62     Must(pageIdIsValid(page));
  63     return shared->theBuf + shared->thePageSize * (page.number - 1);
  64 }
  65
  66 bool
  67 Ipc::Mem::PagePool::pageIdIsValid(const PageId &page) const
  68 {
  69     return page.pool == shared->theId &&
  70         0 < page.number && page.number <= shared->theCapacity;
  71 }
  72
  73
  74 // Ipc::Mem::PagePool::Shared
  75
  76 static unsigned int LastPagePoolId = 0;
  77
  78 Ipc::Mem::PagePool::Shared::Shared(const unsigned int aCapacity, size_t aPageSize):
  79     theId(++LastPagePoolId), theCapacity(aCapacity), thePageSize(aPageSize)
  80 {
  81     if (LastPagePoolId + 1 == 0)
  82         ++LastPagePoolId; // skip zero pool id
  83 }