public PgHdr pPgHdr = new PgHdr(); // Pointer to Actual Page Header
public void Clear()
{
this.iKey = 0;
this.pNext = null;
this.pCache = null;
this.pPgHdr.ClearState();
}
private RC pcache1ResizeHash()
{
Debug.Assert(MutexEx.Held(pGroup.mutex));
var nNew = nHash * 2;
if (nNew < 256)
nNew = 256;
pcache1LeaveMutex(pGroup);
if (nHash != 0)
MallocEx.sqlite3BeginBenignMalloc();
var apNew = new PgHdr1[nNew];
if (nHash != 0)
MallocEx.sqlite3EndBenignMalloc();
pcache1EnterMutex(pGroup);
if (apNew != null)
{
for (var i = 0; i < nHash; i++)
{
var pNext = apHash[i];
PgHdr1 pPage;
while ((pPage = pNext) != null)
{
var h = (Pgno)(pPage.iKey % nNew);
pNext = pPage.pNext;
pPage.pNext = apNew[h];
apNew[h] = pPage;
}
}
apHash = apNew;
nHash = nNew;
}
return (apHash != null ? RC.OK : RC.NOMEM);
}
public PgHdr pPgHdr = new PgHdr(); // Pointer to Actual Page Header
public void Clear()
{
this.iKey = 0;
this.pNext = null;
this.pCache = null;
this.pPgHdr.ClearState();
}
private static void pcache1PinPage(PgHdr1 pPage)
{
if (pPage == null)
{
return;
}
var pCache = pPage.pCache;
var pGroup = pCache.pGroup;
Debug.Assert(MutexEx.Held(pGroup.mutex));
if (pPage.pLruNext != null || pPage == pGroup.pLruTail)
{
if (pPage.pLruPrev != null)
{
pPage.pLruPrev.pLruNext = pPage.pLruNext;
}
if (pPage.pLruNext != null)
{
pPage.pLruNext.pLruPrev = pPage.pLruPrev;
}
if (pGroup.pLruHead == pPage)
{
pGroup.pLruHead = pPage.pLruNext;
}
if (pGroup.pLruTail == pPage)
{
pGroup.pLruTail = pPage.pLruPrev;
}
pPage.pLruNext = null;
pPage.pLruPrev = null;
pPage.pCache.nRecyclable--;
}
}
private static void pcache1EnforceMaxPage(PGroup pGroup)
{
Debug.Assert(MutexEx.Held(pGroup.mutex));
while (pGroup.nCurrentPage > pGroup.nMaxPage && pGroup.pLruTail != null)
{
PgHdr1 p = pGroup.pLruTail;
Debug.Assert(p.pCache.pGroup == pGroup);
pcache1PinPage(p);
pcache1RemoveFromHash(p);
pcache1FreePage(ref p);
}
}
private static void pcache1FreePage(ref PgHdr1 p)
{
if (Check.ALWAYS(p) != null)
{
var pCache = p.pCache;
if (pCache.bPurgeable)
{
pCache.pGroup.nCurrentPage--;
}
pcache1Free(ref p.pPgHdr);
}
}
private PgHdr1 pcache1AllocPage()
{
var pPg = pcache1Alloc(szPage);
var p = new PgHdr1();
p.pCache = this;
p.pPgHdr = pPg;
if (bPurgeable)
{
pGroup.nCurrentPage++;
}
return(p);
}
private static void pcache1RemoveFromHash(PgHdr1 pPage)
{
var pCache = pPage.pCache;
Debug.Assert(MutexEx.Held(pCache.pGroup.mutex));
var h = (int)(pPage.iKey % pCache.nHash);
PgHdr1 pPrev = null;
PgHdr1 pp;
for (pp = pCache.apHash[h]; pp != pPage; pPrev = pp, pp = pp.pNext) ;
if (pPrev == null)
pCache.apHash[h] = pp.pNext;
else
pPrev.pNext = pp.pNext;
pCache.nPage--;
}
private void pcache1TruncateUnsafe(uint iLimit)
{
#if !DEBUG
uint nPage = 0;
#endif
Debug.Assert(MutexEx.Held(pGroup.mutex));
for (uint h = 0; h < nHash; h++)
{
var pp = apHash[h];
PgHdr1 pPrev = null;
PgHdr1 pPage;
while ((pPage = pp) != null)
{
if (pPage.iKey >= iLimit)
{
nPage--;
pp = pPage.pNext;
pcache1PinPage(pPage);
if (apHash[h] == pPage)
{
apHash[h] = pPage.pNext;
}
else
{
pPrev.pNext = pp;
}
pcache1FreePage(ref pPage);
}
else
{
pp = pPage.pNext;
#if !DEBUG
nPage++;
#endif
}
pPrev = pPage;
}
}
#if !DEBUG
Debug.Assert(pCache.nPage == nPage);
#endif
}
private RC pcache1ResizeHash()
{
Debug.Assert(MutexEx.Held(pGroup.mutex));
var nNew = nHash * 2;
if (nNew < 256)
{
nNew = 256;
}
pcache1LeaveMutex(pGroup);
if (nHash != 0)
{
MallocEx.sqlite3BeginBenignMalloc();
}
var apNew = new PgHdr1[nNew];
if (nHash != 0)
{
MallocEx.sqlite3EndBenignMalloc();
}
pcache1EnterMutex(pGroup);
if (apNew != null)
{
for (var i = 0; i < nHash; i++)
{
var pNext = apHash[i];
PgHdr1 pPage;
while ((pPage = pNext) != null)
{
var h = (Pgno)(pPage.iKey % nNew);
pNext = pPage.pNext;
pPage.pNext = apNew[h];
apNew[h] = pPage;
}
}
apHash = apNew;
nHash = nNew;
}
return(apHash != null ? RC.OK : RC.NOMEM);
}
private static void pcache1PinPage(PgHdr1 pPage)
{
if (pPage == null)
return;
var pCache = pPage.pCache;
var pGroup = pCache.pGroup;
Debug.Assert(MutexEx.Held(pGroup.mutex));
if (pPage.pLruNext != null || pPage == pGroup.pLruTail)
{
if (pPage.pLruPrev != null)
pPage.pLruPrev.pLruNext = pPage.pLruNext;
if (pPage.pLruNext != null)
pPage.pLruNext.pLruPrev = pPage.pLruPrev;
if (pGroup.pLruHead == pPage)
pGroup.pLruHead = pPage.pLruNext;
if (pGroup.pLruTail == pPage)
pGroup.pLruTail = pPage.pLruPrev;
pPage.pLruNext = null;
pPage.pLruPrev = null;
pPage.pCache.nRecyclable--;
}
}
private static void pcache1RemoveFromHash(PgHdr1 pPage)
{
var pCache = pPage.pCache;
Debug.Assert(MutexEx.Held(pCache.pGroup.mutex));
var h = (int)(pPage.iKey % pCache.nHash);
PgHdr1 pPrev = null;
PgHdr1 pp;
for (pp = pCache.apHash[h]; pp != pPage; pPrev = pp, pp = pp.pNext)
{
;
}
if (pPrev == null)
{
pCache.apHash[h] = pp.pNext;
}
else
{
pPrev.pNext = pp.pNext;
}
pCache.nPage--;
}
public PgHdr xFetch(Pgno key, int createFlag)
{
Debug.Assert(bPurgeable || createFlag != 1);
Debug.Assert(bPurgeable || nMin == 0);
Debug.Assert(!bPurgeable || nMin == 10);
Debug.Assert(nMin == 0 || bPurgeable);
PGroup pGroup;
pcache1EnterMutex(pGroup = this.pGroup);
// Step 1: Search the hash table for an existing entry.
PgHdr1 pPage = null;
if (nHash > 0)
{
var h = (int)(key % nHash);
for (pPage = apHash[h]; pPage != null && pPage.iKey != key; pPage = pPage.pNext)
{
;
}
}
// Step 2: Abort if no existing page is found and createFlag is 0
if (pPage != null || createFlag == 0)
{
pcache1PinPage(pPage);
goto fetch_out;
}
// The pGroup local variable will normally be initialized by the pcache1EnterMutex() macro above. But if SQLITE_MUTEX_OMIT is defined,
// then pcache1EnterMutex() is a no-op, so we have to initialize the local variable here. Delaying the initialization of pGroup is an
// optimization: The common case is to exit the module before reaching
// this point.
#if SQLITE_MUTEX_OMIT
pGroup = pCache.pGroup;
#endif
// Step 3: Abort if createFlag is 1 but the cache is nearly full
var nPinned = nPage - nRecyclable;
Debug.Assert(nPinned >= 0);
Debug.Assert(pGroup.mxPinned == pGroup.nMaxPage + 10 - pGroup.nMinPage);
Debug.Assert(n90pct == nMax * 9 / 10);
if (createFlag == 1 && (nPinned >= pGroup.mxPinned || nPinned >= (int)n90pct || pcache1UnderMemoryPressure()))
{
goto fetch_out;
}
if (nPage >= nHash && pcache1ResizeHash() != 0)
{
goto fetch_out;
}
// Step 4. Try to recycle a page.
if (bPurgeable && pGroup.pLruTail != null && ((nPage + 1 >= nMax) || pGroup.nCurrentPage >= pGroup.nMaxPage || pcache1UnderMemoryPressure()))
{
pPage = pGroup.pLruTail;
pcache1RemoveFromHash(pPage);
pcache1PinPage(pPage);
PCache1 pOtherCache;
if ((pOtherCache = pPage.pCache).szPage != szPage)
{
pcache1FreePage(ref pPage);
pPage = null;
}
else
{
pGroup.nCurrentPage -= (pOtherCache.bPurgeable ? 1 : 0) - (bPurgeable ? 1 : 0);
}
}
// Step 5. If a usable page buffer has still not been found, attempt to allocate a new one.
if (null == pPage)
{
if (createFlag == 1)
{
MallocEx.sqlite3BeginBenignMalloc();
}
pcache1LeaveMutex(pGroup);
pPage = pcache1AllocPage();
pcache1EnterMutex(pGroup);
if (createFlag == 1)
{
MallocEx.sqlite3EndBenignMalloc();
}
}
if (pPage != null)
{
var h = (int)(key % nHash);
nPage++;
pPage.iKey = key;
pPage.pNext = apHash[h];
pPage.pCache = this;
pPage.pLruPrev = null;
pPage.pLruNext = null;
PGHDR1_TO_PAGE(pPage).ClearState();
pPage.pPgHdr.PgHdr1 = pPage;
apHash[h] = pPage;
}
fetch_out:
if (pPage != null && key > iMaxKey)
{
iMaxKey = key;
}
pcache1LeaveMutex(pGroup);
return(pPage != null ? PGHDR1_TO_PAGE(pPage) : null);
}
private static void pcache1FreePage(ref PgHdr1 p)
{
if (Check.ALWAYS(p) != null)
{
var pCache = p.pCache;
if (pCache.bPurgeable)
pCache.pGroup.nCurrentPage--;
pcache1Free(ref p.pPgHdr);
}
}
private static PgHdr PGHDR1_TO_PAGE(PgHdr1 p)
{
return(p.pPgHdr);
}
private PgHdr1 pcache1AllocPage()
{
var pPg = pcache1Alloc(szPage);
var p = new PgHdr1();
p.pCache = this;
p.pPgHdr = pPg;
if (bPurgeable)
pGroup.nCurrentPage++;
return p;
}
private static PgHdr PGHDR1_TO_PAGE(PgHdr1 p)
{
return p.pPgHdr;
}
