wasCSharpSQLite – Rev 1
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using System;
using System.Diagnostics;
using System.Text;
using u32 = System.UInt32;
using Pgno = System.UInt32;
namespace Community.CsharpSqlite
{
using sqlite3_value = Sqlite3.Mem;
using sqlite3_pcache = Sqlite3.PCache1;
public partial class Sqlite3
{
/*
** 2008 August 05
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
** This file implements that page cache.
*************************************************************************
** Included in SQLite3 port to C#-SQLite; 2008 Noah B Hart
** C#-SQLite is an independent reimplementation of the SQLite software library
**
** SQLITE_SOURCE_ID: 2011-06-23 19:49:22 4374b7e83ea0a3fbc3691f9c0c936272862f32f2
**
*************************************************************************
*/
//#include "sqliteInt.h"
/*
** A complete page cache is an instance of this structure.
*/
public class PCache
{
public PgHdr pDirty, pDirtyTail; /* List of dirty pages in LRU order */
public PgHdr pSynced; /* Last synced page in dirty page list */
public int _nRef; /* Number of referenced pages */
public int nMax; /* Configured cache size */
public int szPage; /* Size of every page in this cache */
public int szExtra; /* Size of extra space for each page */
public bool bPurgeable; /* True if pages are on backing store */
public dxStress xStress; //int (*xStress)(void*,PgHdr*); /* Call to try make a page clean */
public object pStress; /* Argument to xStress */
public sqlite3_pcache pCache; /* Pluggable cache module */
public PgHdr pPage1; /* Reference to page 1 */
public int nRef /* Number of referenced pages */
{
get
{
return _nRef;
}
set
{
_nRef = value;
}
}
public void Clear()
{
pDirty = null;
pDirtyTail = null;
pSynced = null;
nRef = 0;
}
};
/*
** Some of the Debug.Assert() macros in this code are too expensive to run
** even during normal debugging. Use them only rarely on long-running
** tests. Enable the expensive asserts using the
** -DSQLITE_ENABLE_EXPENSIVE_ASSERT=1 compile-time option.
*/
#if SQLITE_ENABLE_EXPENSIVE_ASSERT
//# define expensive_assert(X) Debug.Assert(X)
static void expensive_assert( bool x ) { Debug.Assert( x ); }
#else
//# define expensive_assert(X)
#endif
/********************************** Linked List Management ********************/
#if !NDEBUG && SQLITE_ENABLE_EXPENSIVE_ASSERT
/*
** Check that the pCache.pSynced variable is set correctly. If it
** is not, either fail an Debug.Assert or return zero. Otherwise, return
** non-zero. This is only used in debugging builds, as follows:
**
** expensive_assert( pcacheCheckSynced(pCache) );
*/
static int pcacheCheckSynced(PCache pCache){
PgHdr p ;
for(p=pCache.pDirtyTail; p!=pCache.pSynced; p=p.pDirtyPrev){
Debug.Assert( p.nRef !=0|| (p.flags&PGHDR_NEED_SYNC) !=0);
}
return (p==null || p.nRef!=0 || (p.flags&PGHDR_NEED_SYNC)==0)?1:0;
}
#endif //* !NDEBUG && SQLITE_ENABLE_EXPENSIVE_ASSERT */
/*
** Remove page pPage from the list of dirty pages.
*/
static void pcacheRemoveFromDirtyList( PgHdr pPage )
{
PCache p = pPage.pCache;
Debug.Assert( pPage.pDirtyNext != null || pPage == p.pDirtyTail );
Debug.Assert( pPage.pDirtyPrev != null || pPage == p.pDirty );
/* Update the PCache1.pSynced variable if necessary. */
if ( p.pSynced == pPage )
{
PgHdr pSynced = pPage.pDirtyPrev;
while ( pSynced != null && ( pSynced.flags & PGHDR_NEED_SYNC ) != 0 )
{
pSynced = pSynced.pDirtyPrev;
}
p.pSynced = pSynced;
}
if ( pPage.pDirtyNext != null )
{
pPage.pDirtyNext.pDirtyPrev = pPage.pDirtyPrev;
}
else
{
Debug.Assert( pPage == p.pDirtyTail );
p.pDirtyTail = pPage.pDirtyPrev;
}
if ( pPage.pDirtyPrev != null )
{
pPage.pDirtyPrev.pDirtyNext = pPage.pDirtyNext;
}
else
{
Debug.Assert( pPage == p.pDirty );
p.pDirty = pPage.pDirtyNext;
}
pPage.pDirtyNext = null;
pPage.pDirtyPrev = null;
#if SQLITE_ENABLE_EXPENSIVE_ASSERT
expensive_assert( pcacheCheckSynced(p) );
#endif
}
/*
** Add page pPage to the head of the dirty list (PCache1.pDirty is set to
** pPage).
*/
static void pcacheAddToDirtyList( PgHdr pPage )
{
PCache p = pPage.pCache;
Debug.Assert( pPage.pDirtyNext == null && pPage.pDirtyPrev == null && p.pDirty != pPage );
pPage.pDirtyNext = p.pDirty;
if ( pPage.pDirtyNext != null )
{
Debug.Assert( pPage.pDirtyNext.pDirtyPrev == null );
pPage.pDirtyNext.pDirtyPrev = pPage;
}
p.pDirty = pPage;
if ( null == p.pDirtyTail )
{
p.pDirtyTail = pPage;
}
if ( null == p.pSynced && 0 == ( pPage.flags & PGHDR_NEED_SYNC ) )
{
p.pSynced = pPage;
}
#if SQLITE_ENABLE_EXPENSIVE_ASSERT
expensive_assert( pcacheCheckSynced(p) );
#endif
}
/*
** Wrapper around the pluggable caches xUnpin method. If the cache is
** being used for an in-memory database, this function is a no-op.
*/
static void pcacheUnpin( PgHdr p )
{
PCache pCache = p.pCache;
if ( pCache.bPurgeable )
{
if ( p.pgno == 1 )
{
pCache.pPage1 = null;
}
sqlite3GlobalConfig.pcache.xUnpin( pCache.pCache, p, false );
}
}
/*************************************************** General Interfaces ******
**
** Initialize and shutdown the page cache subsystem. Neither of these
** functions are threadsafe.
*/
static int sqlite3PcacheInitialize()
{
if ( sqlite3GlobalConfig.pcache.xInit == null )
{
/* IMPLEMENTATION-OF: R-26801-64137 If the xInit() method is NULL, then the
** built-in default page cache is used instead of the application defined
** page cache. */
sqlite3PCacheSetDefault();
}
return sqlite3GlobalConfig.pcache.xInit( sqlite3GlobalConfig.pcache.pArg );
}
static void sqlite3PcacheShutdown()
{
if ( sqlite3GlobalConfig.pcache.xShutdown != null )
{
/* IMPLEMENTATION-OF: R-26000-56589 The xShutdown() method may be NULL. */
sqlite3GlobalConfig.pcache.xShutdown( sqlite3GlobalConfig.pcache.pArg );
}
}
/*
** Return the size in bytes of a PCache object.
*/
static int sqlite3PcacheSize()
{
return 4;
}// sizeof( PCache ); }
/*
** Create a new PCache object. Storage space to hold the object
** has already been allocated and is passed in as the p pointer.
** The caller discovers how much space needs to be allocated by
** calling sqlite3PcacheSize().
*/
static void sqlite3PcacheOpen(
int szPage, /* Size of every page */
int szExtra, /* Extra space associated with each page */
bool bPurgeable, /* True if pages are on backing store */
dxStress xStress,//int (*xStress)(void*,PgHdr*),/* Call to try to make pages clean */
object pStress, /* Argument to xStress */
PCache p /* Preallocated space for the PCache */
)
{
p.Clear();//memset(p, 0, sizeof(PCache));
p.szPage = szPage;
p.szExtra = szExtra;
p.bPurgeable = bPurgeable;
p.xStress = xStress;
p.pStress = pStress;
p.nMax = 100;
}
/*
** Change the page size for PCache object. The caller must ensure that there
** are no outstanding page references when this function is called.
*/
static void sqlite3PcacheSetPageSize( PCache pCache, int szPage )
{
Debug.Assert( pCache.nRef == 0 && pCache.pDirty == null );
if ( pCache.pCache != null )
{
sqlite3GlobalConfig.pcache.xDestroy( ref pCache.pCache );
pCache.pCache = null;
}
pCache.szPage = szPage;
}
/*
** Try to obtain a page from the cache.
*/
static int sqlite3PcacheFetch(
PCache pCache, /* Obtain the page from this cache */
u32 pgno, /* Page number to obtain */
int createFlag, /* If true, create page if it does not exist already */
ref PgHdr ppPage /* Write the page here */
)
{
PgHdr pPage = null;
int eCreate;
Debug.Assert( pCache != null );
Debug.Assert( createFlag == 1 || createFlag == 0 );
Debug.Assert( pgno > 0 );
/* If the pluggable cache (sqlite3_pcache*) has not been allocated,
** allocate it now.
*/
if ( null == pCache.pCache && createFlag != 0 )
{
sqlite3_pcache p;
int nByte;
nByte = pCache.szPage + pCache.szExtra + 0;// sizeof( PgHdr );
p = sqlite3GlobalConfig.pcache.xCreate( nByte, pCache.bPurgeable );
//if ( null == p )
//{
// return SQLITE_NOMEM;
//}
sqlite3GlobalConfig.pcache.xCachesize( p, pCache.nMax );
pCache.pCache = p;
}
eCreate = createFlag * ( 1 + ( ( !pCache.bPurgeable || null == pCache.pDirty ) ? 1 : 0 ) );
if ( pCache.pCache != null )
{
pPage = sqlite3GlobalConfig.pcache.xFetch( pCache.pCache, pgno, eCreate );
}
if ( null == pPage && eCreate == 1 )
{
PgHdr pPg;
/* Find a dirty page to write-out and recycle. First try to find a
** page that does not require a journal-sync (one with PGHDR_NEED_SYNC
** cleared), but if that is not possible settle for any other
** unreferenced dirty page.
*/
#if SQLITE_ENABLE_EXPENSIVE_ASSERT
expensive_assert( pcacheCheckSynced(pCache) );
#endif
for ( pPg = pCache.pSynced;
pPg != null && ( pPg.nRef != 0 || ( pPg.flags & PGHDR_NEED_SYNC ) != 0 );
pPg = pPg.pDirtyPrev
)
;
pCache.pSynced = pPg;
if ( null == pPg )
{
for ( pPg = pCache.pDirtyTail; pPg != null && pPg.nRef != 0; pPg = pPg.pDirtyPrev )
;
}
if ( pPg != null )
{
int rc;
#if SQLITE_LOG_CACHE_SPILL
sqlite3_log(SQLITE_FULL,
"spill page %d making room for %d - cache used: %d/%d",
pPg->pgno, pgno,
sqlite3GlobalConfig.pcache.xPagecount(pCache->pCache),
pCache->nMax);
#endif
rc = pCache.xStress( pCache.pStress, pPg );
if ( rc != SQLITE_OK && rc != SQLITE_BUSY )
{
return rc;
}
}
pPage = sqlite3GlobalConfig.pcache.xFetch( pCache.pCache, pgno, 2 );
}
if ( pPage != null )
{
if ( null == pPage.pData )
{
// memset(pPage, 0, sizeof(PgHdr));
pPage.pData = sqlite3Malloc( pCache.szPage );// pPage->pData = (void*)&pPage[1];
//pPage->pExtra = (void*)&((char*)pPage->pData)[pCache->szPage];
//memset(pPage->pExtra, 0, pCache->szExtra);
pPage.pCache = pCache;
pPage.pgno = pgno;
}
Debug.Assert( pPage.pCache == pCache );
Debug.Assert( pPage.pgno == pgno );
//assert(pPage->pData == (void*)&pPage[1]);
//assert(pPage->pExtra == (void*)&((char*)&pPage[1])[pCache->szPage]);
if ( 0 == pPage.nRef )
{
pCache.nRef++;
}
pPage.nRef++;
if ( pgno == 1 )
{
pCache.pPage1 = pPage;
}
}
ppPage = pPage;
return ( pPage == null && eCreate != 0 ) ? SQLITE_NOMEM : SQLITE_OK;
}
/*
** Decrement the reference count on a page. If the page is clean and the
** reference count drops to 0, then it is made elible for recycling.
*/
static void sqlite3PcacheRelease( PgHdr p )
{
Debug.Assert( p.nRef > 0 );
p.nRef--;
if ( p.nRef == 0 )
{
PCache pCache = p.pCache;
pCache.nRef--;
if ( ( p.flags & PGHDR_DIRTY ) == 0 )
{
pcacheUnpin( p );
}
else
{
/* Move the page to the head of the dirty list. */
pcacheRemoveFromDirtyList( p );
pcacheAddToDirtyList( p );
}
}
}
/*
** Increase the reference count of a supplied page by 1.
*/
static void sqlite3PcacheRef( PgHdr p )
{
Debug.Assert( p.nRef > 0 );
p.nRef++;
}
/*
** Drop a page from the cache. There must be exactly one reference to the
** page. This function deletes that reference, so after it returns the
** page pointed to by p is invalid.
*/
static void sqlite3PcacheDrop( PgHdr p )
{
PCache pCache;
Debug.Assert( p.nRef == 1 );
if ( ( p.flags & PGHDR_DIRTY ) != 0 )
{
pcacheRemoveFromDirtyList( p );
}
pCache = p.pCache;
pCache.nRef--;
if ( p.pgno == 1 )
{
pCache.pPage1 = null;
}
sqlite3GlobalConfig.pcache.xUnpin( pCache.pCache, p, true );
}
/*
** Make sure the page is marked as dirty. If it isn't dirty already,
** make it so.
*/
static void sqlite3PcacheMakeDirty( PgHdr p )
{
p.flags &= ~PGHDR_DONT_WRITE;
Debug.Assert( p.nRef > 0 );
if ( 0 == ( p.flags & PGHDR_DIRTY ) )
{
p.flags |= PGHDR_DIRTY;
pcacheAddToDirtyList( p );
}
}
/*
** Make sure the page is marked as clean. If it isn't clean already,
** make it so.
*/
static void sqlite3PcacheMakeClean( PgHdr p )
{
if ( ( p.flags & PGHDR_DIRTY ) != 0 )
{
pcacheRemoveFromDirtyList( p );
p.flags &= ~( PGHDR_DIRTY | PGHDR_NEED_SYNC );
if ( p.nRef == 0 )
{
pcacheUnpin( p );
}
}
}
/*
** Make every page in the cache clean.
*/
static void sqlite3PcacheCleanAll( PCache pCache )
{
PgHdr p;
while ( ( p = pCache.pDirty ) != null )
{
sqlite3PcacheMakeClean( p );
}
}
/*
** Clear the PGHDR_NEED_SYNC flag from all dirty pages.
*/
static void sqlite3PcacheClearSyncFlags( PCache pCache )
{
PgHdr p;
for ( p = pCache.pDirty; p != null; p = p.pDirtyNext )
{
p.flags &= ~PGHDR_NEED_SYNC;
}
pCache.pSynced = pCache.pDirtyTail;
}
/*
** Change the page number of page p to newPgno.
*/
static void sqlite3PcacheMove( PgHdr p, Pgno newPgno )
{
PCache pCache = p.pCache;
Debug.Assert( p.nRef > 0 );
Debug.Assert( newPgno > 0 );
sqlite3GlobalConfig.pcache.xRekey( pCache.pCache, p, p.pgno, newPgno );
p.pgno = newPgno;
if ( ( p.flags & PGHDR_DIRTY ) != 0 && ( p.flags & PGHDR_NEED_SYNC ) != 0 )
{
pcacheRemoveFromDirtyList( p );
pcacheAddToDirtyList( p );
}
}
/*
** Drop every cache entry whose page number is greater than "pgno". The
** caller must ensure that there are no outstanding references to any pages
** other than page 1 with a page number greater than pgno.
**
** If there is a reference to page 1 and the pgno parameter passed to this
** function is 0, then the data area associated with page 1 is zeroed, but
** the page object is not dropped.
*/
static void sqlite3PcacheTruncate( PCache pCache, u32 pgno )
{
if ( pCache.pCache != null )
{
PgHdr p;
PgHdr pNext;
for ( p = pCache.pDirty; p != null; p = pNext )
{
pNext = p.pDirtyNext;
/* This routine never gets call with a positive pgno except right
** after sqlite3PcacheCleanAll(). So if there are dirty pages,
** it must be that pgno==0.
*/
Debug.Assert( p.pgno > 0 );
if ( ALWAYS( p.pgno > pgno ) )
{
Debug.Assert( ( p.flags & PGHDR_DIRTY ) != 0 );
sqlite3PcacheMakeClean( p );
}
}
if ( pgno == 0 && pCache.pPage1 != null )
{
// memset( pCache.pPage1.pData, 0, pCache.szPage );
pCache.pPage1.pData = sqlite3Malloc( pCache.szPage );
pgno = 1;
}
sqlite3GlobalConfig.pcache.xTruncate( pCache.pCache, pgno + 1 );
}
}
/*
** Close a cache.
*/
static void sqlite3PcacheClose( PCache pCache )
{
if ( pCache.pCache != null )
{
sqlite3GlobalConfig.pcache.xDestroy( ref pCache.pCache );
}
}
/*
** Discard the contents of the cache.
*/
static void sqlite3PcacheClear( PCache pCache )
{
sqlite3PcacheTruncate( pCache, 0 );
}
/*
** Merge two lists of pages connected by pDirty and in pgno order.
** Do not both fixing the pDirtyPrev pointers.
*/
static PgHdr pcacheMergeDirtyList( PgHdr pA, PgHdr pB )
{
PgHdr result = new PgHdr();
PgHdr pTail = result;
while ( pA != null && pB != null )
{
if ( pA.pgno < pB.pgno )
{
pTail.pDirty = pA;
pTail = pA;
pA = pA.pDirty;
}
else
{
pTail.pDirty = pB;
pTail = pB;
pB = pB.pDirty;
}
}
if ( pA != null )
{
pTail.pDirty = pA;
}
else if ( pB != null )
{
pTail.pDirty = pB;
}
else
{
pTail.pDirty = null;
}
return result.pDirty;
}
/*
** Sort the list of pages in accending order by pgno. Pages are
** connected by pDirty pointers. The pDirtyPrev pointers are
** corrupted by this sort.
**
** Since there cannot be more than 2^31 distinct pages in a database,
** there cannot be more than 31 buckets required by the merge sorter.
** One extra bucket is added to catch overflow in case something
** ever changes to make the previous sentence incorrect.
*/
//#define N_SORT_BUCKET 32
const int N_SORT_BUCKET = 32;
static PgHdr pcacheSortDirtyList( PgHdr pIn )
{
PgHdr[] a;
PgHdr p;//a[N_SORT_BUCKET], p;
int i;
a = new PgHdr[N_SORT_BUCKET];//memset(a, 0, sizeof(a));
while ( pIn != null )
{
p = pIn;
pIn = p.pDirty;
p.pDirty = null;
for ( i = 0; ALWAYS( i < N_SORT_BUCKET - 1 ); i++ )
{
if ( a[i] == null )
{
a[i] = p;
break;
}
else
{
p = pcacheMergeDirtyList( a[i], p );
a[i] = null;
}
}
if ( NEVER( i == N_SORT_BUCKET - 1 ) )
{
/* To get here, there need to be 2^(N_SORT_BUCKET) elements in
** the input list. But that is impossible.
*/
a[i] = pcacheMergeDirtyList( a[i], p );
}
}
p = a[0];
for ( i = 1; i < N_SORT_BUCKET; i++ )
{
p = pcacheMergeDirtyList( p, a[i] );
}
return p;
}
/*
** Return a list of all dirty pages in the cache, sorted by page number.
*/
static PgHdr sqlite3PcacheDirtyList( PCache pCache )
{
PgHdr p;
for ( p = pCache.pDirty; p != null; p = p.pDirtyNext )
{
p.pDirty = p.pDirtyNext;
}
return pcacheSortDirtyList( pCache.pDirty );
}
/*
** Return the total number of referenced pages held by the cache.
*/
static int sqlite3PcacheRefCount( PCache pCache )
{
return pCache.nRef;
}
/*
** Return the number of references to the page supplied as an argument.
*/
static int sqlite3PcachePageRefcount( PgHdr p )
{
return p.nRef;
}
/*
** Return the total number of pages in the cache.
*/
static int sqlite3PcachePagecount( PCache pCache )
{
int nPage = 0;
if ( pCache.pCache != null )
{
nPage = sqlite3GlobalConfig.pcache.xPagecount( pCache.pCache );
}
return nPage;
}
#if SQLITE_TEST
/*
** Get the suggested cache-size value.
*/
static int sqlite3PcacheGetCachesize( PCache pCache )
{
return pCache.nMax;
}
#endif
/*
** Set the suggested cache-size value.
*/
static void sqlite3PcacheSetCachesize( PCache pCache, int mxPage )
{
pCache.nMax = mxPage;
if ( pCache.pCache != null )
{
sqlite3GlobalConfig.pcache.xCachesize( pCache.pCache, mxPage );
}
}
#if SQLITE_CHECK_PAGES || (SQLITE_DEBUG)
/*
** For all dirty pages currently in the cache, invoke the specified
** callback. This is only used if the SQLITE_CHECK_PAGES macro is
** defined.
*/
static void sqlite3PcacheIterateDirty( PCache pCache, dxIter xIter )
{
PgHdr pDirty;
for ( pDirty = pCache.pDirty; pDirty != null; pDirty = pDirty.pDirtyNext )
{
xIter( pDirty );
}
}
#endif
}
}