root/third_party/sqlite/src/src/test_pcache.c

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DEFINITIONS

This source file includes following definitions.
  1. testpcacheInit
  2. testpcacheShutdown
  3. testpcacheRandom
  4. testpcacheCreate
  5. testpcacheCachesize
  6. testpcachePagecount
  7. testpcacheFetch
  8. testpcacheUnpin
  9. testpcacheRekey
  10. testpcacheTruncate
  11. testpcacheDestroy
  12. installTestPCache

/*
** 2008 November 18
**
** 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 contains code used for testing the SQLite system.
** None of the code in this file goes into a deliverable build.
** 
** This file contains an application-defined pager cache
** implementation that can be plugged in in place of the
** default pcache.  This alternative pager cache will throw
** some errors that the default cache does not.
**
** This pagecache implementation is designed for simplicity
** not speed.  
*/
#include "sqlite3.h"
#include <string.h>
#include <assert.h>

/*
** Global data used by this test implementation.  There is no
** mutexing, which means this page cache will not work in a
** multi-threaded test.
*/
typedef struct testpcacheGlobalType testpcacheGlobalType;
struct testpcacheGlobalType {
  void *pDummy;             /* Dummy allocation to simulate failures */
  int nInstance;            /* Number of current instances */
  unsigned discardChance;   /* Chance of discarding on an unpin (0-100) */
  unsigned prngSeed;        /* Seed for the PRNG */
  unsigned highStress;      /* Call xStress agressively */
};
static testpcacheGlobalType testpcacheGlobal;

/*
** Initializer.
**
** Verify that the initializer is only called when the system is
** uninitialized.  Allocate some memory and report SQLITE_NOMEM if
** the allocation fails.  This provides a means to test the recovery
** from a failed initialization attempt.  It also verifies that the
** the destructor always gets call - otherwise there would be a
** memory leak.
*/
static int testpcacheInit(void *pArg){
  assert( pArg==(void*)&testpcacheGlobal );
  assert( testpcacheGlobal.pDummy==0 );
  assert( testpcacheGlobal.nInstance==0 );
  testpcacheGlobal.pDummy = sqlite3_malloc(10);
  return testpcacheGlobal.pDummy==0 ? SQLITE_NOMEM : SQLITE_OK;
}

/*
** Destructor
**
** Verify that this is only called after initialization.
** Free the memory allocated by the initializer.
*/
static void testpcacheShutdown(void *pArg){
  assert( pArg==(void*)&testpcacheGlobal );
  assert( testpcacheGlobal.pDummy!=0 );
  assert( testpcacheGlobal.nInstance==0 );
  sqlite3_free( testpcacheGlobal.pDummy );
  testpcacheGlobal.pDummy = 0;
}

/*
** Number of pages in a cache.
**
** The number of pages is a hard upper bound in this test module.
** If more pages are requested, sqlite3PcacheFetch() returns NULL.
**
** If testing with in-memory temp tables, provide a larger pcache.
** Some of the test cases need this.
*/
#if defined(SQLITE_TEMP_STORE) && SQLITE_TEMP_STORE>=2
# define TESTPCACHE_NPAGE    499
#else
# define TESTPCACHE_NPAGE    217
#endif
#define TESTPCACHE_RESERVE   17

/*
** Magic numbers used to determine validity of the page cache.
*/
#define TESTPCACHE_VALID  0x364585fd
#define TESTPCACHE_CLEAR  0xd42670d4

/*
** Private implementation of a page cache.
*/
typedef struct testpcache testpcache;
struct testpcache {
  int szPage;               /* Size of each page.  Multiple of 8. */
  int bPurgeable;           /* True if the page cache is purgeable */
  int nFree;                /* Number of unused slots in a[] */
  int nPinned;              /* Number of pinned slots in a[] */
  unsigned iRand;           /* State of the PRNG */
  unsigned iMagic;          /* Magic number for sanity checking */
  struct testpcachePage {
    unsigned key;              /* The key for this page. 0 means unallocated */
    int isPinned;              /* True if the page is pinned */
    void *pData;               /* Data for this page */
  } a[TESTPCACHE_NPAGE];    /* All pages in the cache */
};

/*
** Get a random number using the PRNG in the given page cache.
*/
static unsigned testpcacheRandom(testpcache *p){
  unsigned x = 0;
  int i;
  for(i=0; i<4; i++){
    p->iRand = (p->iRand*69069 + 5);
    x = (x<<8) | ((p->iRand>>16)&0xff);
  }
  return x;
}


/*
** Allocate a new page cache instance.
*/
static sqlite3_pcache *testpcacheCreate(int szPage, int bPurgeable){
  int nMem;
  char *x;
  testpcache *p;
  int i;
  assert( testpcacheGlobal.pDummy!=0 );
  szPage = (szPage+7)&~7;
  nMem = sizeof(testpcache) + TESTPCACHE_NPAGE*szPage;
  p = sqlite3_malloc( nMem );
  if( p==0 ) return 0;
  x = (char*)&p[1];
  p->szPage = szPage;
  p->nFree = TESTPCACHE_NPAGE;
  p->nPinned = 0;
  p->iRand = testpcacheGlobal.prngSeed;
  p->bPurgeable = bPurgeable;
  p->iMagic = TESTPCACHE_VALID;
  for(i=0; i<TESTPCACHE_NPAGE; i++, x += szPage){
    p->a[i].key = 0;
    p->a[i].isPinned = 0;
    p->a[i].pData = (void*)x;
  }
  testpcacheGlobal.nInstance++;
  return (sqlite3_pcache*)p;
}

/*
** Set the cache size
*/
static void testpcacheCachesize(sqlite3_pcache *pCache, int newSize){
  testpcache *p = (testpcache*)pCache;
  assert( p->iMagic==TESTPCACHE_VALID );
  assert( newSize>=1 );
  assert( testpcacheGlobal.pDummy!=0 );
  assert( testpcacheGlobal.nInstance>0 );
}

/*
** Return the number of pages in the cache that are being used.
** This includes both pinned and unpinned pages.
*/
static int testpcachePagecount(sqlite3_pcache *pCache){
  testpcache *p = (testpcache*)pCache;
  assert( p->iMagic==TESTPCACHE_VALID );
  assert( testpcacheGlobal.pDummy!=0 );
  assert( testpcacheGlobal.nInstance>0 );
  return TESTPCACHE_NPAGE - p->nFree;
}

/*
** Fetch a page.
*/
static void *testpcacheFetch(
  sqlite3_pcache *pCache,
  unsigned key,
  int createFlag
){
  testpcache *p = (testpcache*)pCache;
  int i, j;
  assert( p->iMagic==TESTPCACHE_VALID );
  assert( testpcacheGlobal.pDummy!=0 );
  assert( testpcacheGlobal.nInstance>0 );

  /* See if the page is already in cache.  Return immediately if it is */
  for(i=0; i<TESTPCACHE_NPAGE; i++){
    if( p->a[i].key==key ){
      if( !p->a[i].isPinned ){
        p->nPinned++;
        assert( p->nPinned <= TESTPCACHE_NPAGE - p->nFree );
        p->a[i].isPinned = 1;
      }
      return p->a[i].pData;
    }
  }

  /* If createFlag is 0, never allocate a new page */
  if( createFlag==0 ){
    return 0;
  }

  /* If no pages are available, always fail */
  if( p->nPinned==TESTPCACHE_NPAGE ){
    return 0;
  }

  /* Do not allocate the last TESTPCACHE_RESERVE pages unless createFlag is 2 */
  if( p->nPinned>=TESTPCACHE_NPAGE-TESTPCACHE_RESERVE && createFlag<2 ){
    return 0;
  }

  /* Do not allocate if highStress is enabled and createFlag is not 2.  
  **
  ** The highStress setting causes pagerStress() to be called much more
  ** often, which exercises the pager logic more intensely.
  */
  if( testpcacheGlobal.highStress && createFlag<2 ){
    return 0;
  }

  /* Find a free page to allocate if there are any free pages.
  ** Withhold TESTPCACHE_RESERVE free pages until createFlag is 2.
  */
  if( p->nFree>TESTPCACHE_RESERVE || (createFlag==2 && p->nFree>0) ){
    j = testpcacheRandom(p) % TESTPCACHE_NPAGE;
    for(i=0; i<TESTPCACHE_NPAGE; i++, j = (j+1)%TESTPCACHE_NPAGE){
      if( p->a[j].key==0 ){
        p->a[j].key = key;
        p->a[j].isPinned = 1;
        memset(p->a[j].pData, 0, p->szPage);
        p->nPinned++;
        p->nFree--;
        assert( p->nPinned <= TESTPCACHE_NPAGE - p->nFree );
        return p->a[j].pData;
      }
    }

    /* The prior loop always finds a freepage to allocate */
    assert( 0 );
  }

  /* If this cache is not purgeable then we have to fail.
  */
  if( p->bPurgeable==0 ){
    return 0;
  }

  /* If there are no free pages, recycle a page.  The page to
  ** recycle is selected at random from all unpinned pages.
  */
  j = testpcacheRandom(p) % TESTPCACHE_NPAGE;
  for(i=0; i<TESTPCACHE_NPAGE; i++, j = (j+1)%TESTPCACHE_NPAGE){
    if( p->a[j].key>0 && p->a[j].isPinned==0 ){
      p->a[j].key = key;
      p->a[j].isPinned = 1;
      memset(p->a[j].pData, 0, p->szPage);
      p->nPinned++;
      assert( p->nPinned <= TESTPCACHE_NPAGE - p->nFree );
      return p->a[j].pData;
    }
  }

  /* The previous loop always finds a page to recycle. */
  assert(0);
  return 0;
}

/*
** Unpin a page.
*/
static void testpcacheUnpin(
  sqlite3_pcache *pCache,
  void *pOldPage,
  int discard
){
  testpcache *p = (testpcache*)pCache;
  int i;
  assert( p->iMagic==TESTPCACHE_VALID );
  assert( testpcacheGlobal.pDummy!=0 );
  assert( testpcacheGlobal.nInstance>0 );

  /* Randomly discard pages as they are unpinned according to the
  ** discardChance setting.  If discardChance is 0, the random discard
  ** never happens.  If discardChance is 100, it always happens.
  */
  if( p->bPurgeable
  && (100-testpcacheGlobal.discardChance) <= (testpcacheRandom(p)%100)
  ){
    discard = 1;
  }

  for(i=0; i<TESTPCACHE_NPAGE; i++){
    if( p->a[i].pData==pOldPage ){
      /* The pOldPage pointer always points to a pinned page */
      assert( p->a[i].isPinned );
      p->a[i].isPinned = 0;
      p->nPinned--;
      assert( p->nPinned>=0 );
      if( discard ){
        p->a[i].key = 0;
        p->nFree++;
        assert( p->nFree<=TESTPCACHE_NPAGE );
      }
      return;
    }
  }

  /* The pOldPage pointer always points to a valid page */
  assert( 0 );
}


/*
** Rekey a single page.
*/
static void testpcacheRekey(
  sqlite3_pcache *pCache,
  void *pOldPage,
  unsigned oldKey,
  unsigned newKey
){
  testpcache *p = (testpcache*)pCache;
  int i;
  assert( p->iMagic==TESTPCACHE_VALID );
  assert( testpcacheGlobal.pDummy!=0 );
  assert( testpcacheGlobal.nInstance>0 );

  /* If there already exists another page at newKey, verify that
  ** the other page is unpinned and discard it.
  */
  for(i=0; i<TESTPCACHE_NPAGE; i++){
    if( p->a[i].key==newKey ){
      /* The new key is never a page that is already pinned */
      assert( p->a[i].isPinned==0 );
      p->a[i].key = 0;
      p->nFree++;
      assert( p->nFree<=TESTPCACHE_NPAGE );
      break;
    }
  }

  /* Find the page to be rekeyed and rekey it.
  */
  for(i=0; i<TESTPCACHE_NPAGE; i++){
    if( p->a[i].key==oldKey ){
      /* The oldKey and pOldPage parameters match */
      assert( p->a[i].pData==pOldPage );
      /* Page to be rekeyed must be pinned */
      assert( p->a[i].isPinned );
      p->a[i].key = newKey;
      return;
    }
  }

  /* Rekey is always given a valid page to work with */
  assert( 0 );
}


/*
** Truncate the page cache.  Every page with a key of iLimit or larger
** is discarded.
*/
static void testpcacheTruncate(sqlite3_pcache *pCache, unsigned iLimit){
  testpcache *p = (testpcache*)pCache;
  unsigned int i;
  assert( p->iMagic==TESTPCACHE_VALID );
  assert( testpcacheGlobal.pDummy!=0 );
  assert( testpcacheGlobal.nInstance>0 );
  for(i=0; i<TESTPCACHE_NPAGE; i++){
    if( p->a[i].key>=iLimit ){
      p->a[i].key = 0;
      if( p->a[i].isPinned ){
        p->nPinned--;
        assert( p->nPinned>=0 );
      }
      p->nFree++;
      assert( p->nFree<=TESTPCACHE_NPAGE );
    }
  }
}

/*
** Destroy a page cache.
*/
static void testpcacheDestroy(sqlite3_pcache *pCache){
  testpcache *p = (testpcache*)pCache;
  assert( p->iMagic==TESTPCACHE_VALID );
  assert( testpcacheGlobal.pDummy!=0 );
  assert( testpcacheGlobal.nInstance>0 );
  p->iMagic = TESTPCACHE_CLEAR;
  sqlite3_free(p);
  testpcacheGlobal.nInstance--;
}


/*
** Invoke this routine to register or unregister the testing pager cache
** implemented by this file.
**
** Install the test pager cache if installFlag is 1 and uninstall it if
** installFlag is 0.
**
** When installing, discardChance is a number between 0 and 100 that
** indicates the probability of discarding a page when unpinning the
** page.  0 means never discard (unless the discard flag is set).
** 100 means always discard.
*/
void installTestPCache(
  int installFlag,            /* True to install.  False to uninstall. */
  unsigned discardChance,     /* 0-100.  Chance to discard on unpin */
  unsigned prngSeed,          /* Seed for the PRNG */
  unsigned highStress         /* Call xStress agressively */
){
  static const sqlite3_pcache_methods testPcache = {
    (void*)&testpcacheGlobal,
    testpcacheInit,
    testpcacheShutdown,
    testpcacheCreate,
    testpcacheCachesize,
    testpcachePagecount,
    testpcacheFetch,
    testpcacheUnpin,
    testpcacheRekey,
    testpcacheTruncate,
    testpcacheDestroy,
  };
  static sqlite3_pcache_methods defaultPcache;
  static int isInstalled = 0;

  assert( testpcacheGlobal.nInstance==0 );
  assert( testpcacheGlobal.pDummy==0 );
  assert( discardChance<=100 );
  testpcacheGlobal.discardChance = discardChance;
  testpcacheGlobal.prngSeed = prngSeed ^ (prngSeed<<16);
  testpcacheGlobal.highStress = highStress;
  if( installFlag!=isInstalled ){
    if( installFlag ){
      sqlite3_config(SQLITE_CONFIG_GETPCACHE, &defaultPcache);
      assert( defaultPcache.xCreate!=testpcacheCreate );
      sqlite3_config(SQLITE_CONFIG_PCACHE, &testPcache);
    }else{
      assert( defaultPcache.xCreate!=0 );
      sqlite3_config(SQLITE_CONFIG_PCACHE, &defaultPcache);
    }
    isInstalled = installFlag;
  }
}

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