SQLite

/*
** 2004 April 6
**
** 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: btree.c,v 1.500 2008/08/22 12:57:09 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
** Including a description of file format and an overview of operation.
*/
#include "btreeInt.h"

  int i;                     /* Loop counter */
  int pc;                    /* Address of a i-th cell */
  int addr;                  /* Offset of first byte after cell pointer array */
  int hdr;                   /* Offset to the page header */
  int size;                  /* Size of a cell */
  int usableSize;            /* Number of usable bytes on a page */
  int cellOffset;            /* Offset to the cell pointer array */
  int cbrk;                  /* Offset to the cell content area */
  int nCell;                 /* Number of cells on the page */
  unsigned char *data;       /* The page data */
  unsigned char *temp;       /* Temp area for cell content */

  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  assert( pPage->pBt!=0 );
  assert( pPage->pBt->usableSize <= SQLITE_MAX_PAGE_SIZE );
  assert( pPage->nOverflow==0 );
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  temp = sqlite3PagerTempSpace(pPage->pBt->pPager);
  data = pPage->aData;
  hdr = pPage->hdrOffset;
  cellOffset = pPage->cellOffset;
  nCell = pPage->nCell;
  assert( nCell==get2byte(&data[hdr+3]) );
  usableSize = pPage->pBt->usableSize;
  cbrk = get2byte(&data[hdr+5]);
  memcpy(&temp[cbrk], &data[cbrk], usableSize - cbrk);
  cbrk = usableSize;
  for(i=0; i<nCell; i++){
    u8 *pAddr;     /* The i-th cell pointer */
    pAddr = &data[cellOffset + i*2];
    pc = get2byte(pAddr);
    assert( pc<pPage->pBt->usableSize );
    size = cellSizePtr(pPage, &temp[pc]);
    cbrk -= size;
    memcpy(&data[cbrk], &temp[pc], size);
    put2byte(pAddr, cbrk);
  }
  assert( cbrk>=cellOffset+2*nCell );
  put2byte(&data[hdr+5], cbrk);
  data[hdr+1] = 0;
  data[hdr+2] = 0;
  data[hdr+7] = 0;
  addr = cellOffset+2*nCell;
  memset(&data[addr], 0, cbrk-addr);
}

/*
** Allocate nByte bytes of space on a page.
**
** Return the index into pPage->aData[] of the first byte of
** the new allocation.  The caller guarantees that there is enough

  MemPage *pChild;    /* Pointer to a new child page */
  Pgno pgnoChild;     /* Page number of the new child page */
  BtShared *pBt;         /* The BTree */
  int usableSize;     /* Total usable size of a page */
  u8 *data;           /* Content of the parent page */
  u8 *cdata;          /* Content of the child page */
  int hdr;            /* Offset to page header in parent */
  int cbrk;           /* Offset to content of first cell in parent */

  assert( pPage->pParent==0 );
  assert( pPage->nOverflow>0 );
  pBt = pPage->pBt;
  assert( sqlite3_mutex_held(pBt->mutex) );
  rc = allocateBtreePage(pBt, &pChild, &pgnoChild, pPage->pgno, 0);
  if( rc ) return rc;
  assert( sqlite3PagerIswriteable(pChild->pDbPage) );
  usableSize = pBt->usableSize;
  data = pPage->aData;
  hdr = pPage->hdrOffset;
  cbrk = get2byte(&data[hdr+5]);
  cdata = pChild->aData;
  memcpy(cdata, &data[hdr], pPage->cellOffset+2*pPage->nCell-hdr);
  memcpy(&cdata[cbrk], &data[cbrk], usableSize-cbrk);
  if( pChild->isInit ) return SQLITE_CORRUPT;
  rc = sqlite3BtreeInitPage(pChild, pPage);
  if( rc ) goto balancedeeper_out;
  memcpy(pChild->aOvfl, pPage->aOvfl, pPage->nOverflow*sizeof(pPage->aOvfl[0]));
  pChild->nOverflow = pPage->nOverflow;
  if( pChild->nOverflow ){
    pChild->nFree = 0;

** The pager is used to access a database disk file.  It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file.  The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.474 2008/08/22 12:57:09 drh Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"

/*
** Macros for troubleshooting.  Normally turned off
*/

  pPg = pager_lookup(pPager, pgno);
  PAGERTRACE4("PLAYBACK %d page %d hash(%08x)\n",
               PAGERID(pPager), pgno, pager_datahash(pPager->pageSize, aData));
  if( (pPager->state>=PAGER_EXCLUSIVE)
   && (pPg==0 || 0==(pPg->flags&PGHDR_NEED_SYNC))
   && (pPager->fd->pMethods)
  ){
    i64 ofst = (pgno-1)*(i64)pPager->pageSize;
    rc = sqlite3OsWrite(pPager->fd, aData, pPager->pageSize, ofst);
  }
  if( pPg ){
    /* No page should ever be explicitly rolled back that is in use, except
    ** for page 1 which is held in use in order to keep the lock on the
    ** database active. However such a page may be rolled back as a result
    ** of an internal error resulting in an automatic call to
    ** sqlite3PagerRollback().

**              assurance that the journal will not be corrupted to the
**              point of causing damage to the database during rollback.
**
** Numeric values associated with these states are OFF==1, NORMAL=2,
** and FULL=3.
*/
#ifndef SQLITE_OMIT_PAGER_PRAGMAS
void sqlite3PagerSetSafetyLevel(Pager *pPager, int level, int bFullFsync){
  pPager->noSync =  level==1 || pPager->tempFile;
  pPager->fullSync = level==3 && !pPager->tempFile;
  pPager->sync_flags = (bFullFsync?SQLITE_SYNC_FULL:SQLITE_SYNC_NORMAL);
  if( pPager->noSync ) pPager->needSync = 0;
}
#endif

/*
** The following global variable is incremented whenever the library
** attempts to open a temporary file.  This information is used for