SQLite

** The insert batch number is a parameter to the TEST primitive.  The
** hash table is rebuilt whenever the batch number increases.  TEST
** operations only look for INSERTs that occurred in prior batches.
**
** The caller is responsible for insuring that there are no duplicate
** INSERTs.
**
** $Id: rowhash.c,v 1.4 2009/04/21 18:20:45 danielk1977 Exp $
*/
#include "sqliteInt.h"

/*
** An upper bound on the size of heap allocations made by this module.
** Limiting the size of allocations helps to avoid memory fragmentation.
*/

** The linked list of RowHashBlock objects also provides a way to sequentially
** scan all elements in the RowHash.  This sequential scan is used when
** rebuilding the hash table.  The hash table is rebuilt after every 
** batch of inserts.
*/
struct RowHashBlock {
  struct RowHashBlockData {

    RowHashBlock *pNext;      /* Next RowHashBlock object in list of them all */
  } data;
  RowHashElem aElem[ROWHASH_ELEM_PER_BLOCK]; /* Available RowHashElem objects */
};

/*
** RowHash structure. References to a structure of this type are passed
** around and used as opaque handles by code in other modules.
*/
struct RowHash {
  int nUsed;              /* Number of used entries in first RowHashBlock */
  int nEntry;             /* Number of used entries over all RowHashBlocks */
  int iBatch;             /* The current insert batch number */
  u8 nHeight;             /* Height of tree of hash pages */
  u8 nLinearLimit;        /* Linear search limit (used if pHash==0) */
  int nBucket;            /* Number of buckets in hash table */
  RowHashPage *pHash;     /* Pointer to root of hash table tree */
  RowHashBlock *pBlock;   /* Linked list of RowHashBlocks */

  /* Allocate the hash-table. */
  if( allocHashTable(&p->pHash, p->nHeight, &nLeaf) ){
    return SQLITE_NOMEM;
  }

  /* Insert all values into the hash-table. */
  for(pBlock=p->pBlock; pBlock; pBlock=pBlock->data.pNext){
    RowHashElem * const pEnd = &pBlock->aElem[
      pBlock==p->pBlock?p->nUsed:ROWHASH_ELEM_PER_BLOCK
    ];
    RowHashElem *pIter;
    for(pIter=pBlock->aElem; pIter<pEnd; pIter++){
      RowHashElem **ppElem = findHashBucket(p, pIter->iVal);
      pIter->pNext = *ppElem;
      *ppElem = pIter;
    }
  }

    }
    p->db = db;
    *pp = p;
  }

  /* If the current RowHashBlock is full, or if the first RowHashBlock has
  ** not yet been allocated, allocate one now. */ 
  if( !p->pBlock || p->nUsed==ROWHASH_ELEM_PER_BLOCK ){
    RowHashBlock *pBlock = (RowHashBlock*)sqlite3Malloc(sizeof(RowHashBlock));
    if( !pBlock ){
      return SQLITE_NOMEM;
    }

    pBlock->data.pNext = p->pBlock;
    p->pBlock = pBlock;
    p->nUsed = 0;
  }
  assert( p->nUsed==(p->nEntry % ROWHASH_ELEM_PER_BLOCK) );

  /* Add iVal to the current RowHashBlock. */
  p->pBlock->aElem[p->nUsed].iVal = iVal;
  p->nUsed++;
  p->nEntry++;
  return SQLITE_OK;
}

/*
** Destroy the RowHash object passed as the first argument.
*/

/*
** 2005 December 14
**
** 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.
**
*************************************************************************
**
** $Id: test_async.c,v 1.58 2009/04/21 18:20:45 danielk1977 Exp $
**
** This file contains an example implementation of an asynchronous IO 
** backend for SQLite.
**
** WHAT IS ASYNCHRONOUS I/O?
**
** With asynchronous I/O, write requests are handled by a separate thread

** Multiple connections from within a single process that use this
** implementation of asynchronous IO may access a single database
** file concurrently. From the point of view of the user, if all
** connections are from within a single process, there is no difference
** between the concurrency offered by "normal" SQLite and SQLite
** using the asynchronous backend.
**
** If connections from within multiple processes may access the
** database file, the ENABLE_FILE_LOCKING symbol (see below) must be
** defined. If it is not defined, then no locks are established on 
** the database file. In this case, if multiple processes access 
** the database file, corruption will quickly result.
**
** If ENABLE_FILE_LOCKING is defined (the default), then connections 
** from within multiple processes may access a single database file