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Begin adding BTree code (CVS 213)
FossilOrigin-Name: bdb1c425f577d455155982ee2cd8cb686bcaf0da
This commit is contained in:
drh
266
src/btree.c
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266
src/btree.c
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/*
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** Copyright (c) 2001 D. Richard Hipp
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**
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** This program is free software; you can redistribute it and/or
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** modify it under the terms of the GNU General Public
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** License as published by the Free Software Foundation; either
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** version 2 of the License, or (at your option) any later version.
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**
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** This program is distributed in the hope that it will be useful,
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** but WITHOUT ANY WARRANTY; without even the implied warranty of
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** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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** General Public License for more details.
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**
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** You should have received a copy of the GNU General Public
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** License along with this library; if not, write to the
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** Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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** Boston, MA 02111-1307, USA.
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**
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** Author contact information:
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** drh@hwaci.com
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** http://www.hwaci.com/drh/
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**
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*************************************************************************
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** $Id: btree.c,v 1.1 2001/04/17 20:09:11 drh Exp $
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*/
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#include "sqliteInt.h"
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#include "pager.h"
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#include "btree.h"
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#include <assert.h>
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typedef unsigned int u32;
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/*
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** Everything we need to know about an open database
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*/
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struct Btree {
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Pager *pPager; /* The page cache */
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BtCursor *pCursor; /* All open cursors */
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u32 *page1; /* First page of the database */
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int inTrans; /* True if a transaction is current */
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};
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typedef Btree Bt;
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/*
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** The maximum depth of a cursor
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*/
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#define MX_LEVEL 20
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/*
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** Within a cursor, each level off the search tree is an instance of
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** this structure.
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*/
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typedef struct BtIdxpt BtIdxpt;
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struct BtIdxpt {
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Pgno pgno; /* The page number */
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u32 *aPage; /* The page data */
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int idx; /* Index into pPage[] */
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};
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/*
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** Everything we need to know about a cursor
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*/
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struct BtCursor {
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Btree *pBt; /* The whole database */
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BtCursor *pPrev, *pNext; /* Linked list of all cursors */
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int valid; /* True if the cursor points to something */
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int nLevel; /* Number of levels of indexing used */
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BtIdxpt aLevel[MX_LEVEL]; /* The index levels */
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};
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/*
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** The first page contains the following additional information:
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**
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** MAGIC-1
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** MAGIC-2
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** First free block
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*/
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#define EXTRA_PAGE_1_CELLS 3
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#define MAGIC_1 0x7264dc61
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#define MAGIC_2 0x54e55d9e
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/*
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** Open a new database
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*/
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int sqliteBtreeOpen(const char *zFilename, int mode, Btree **ppBtree){
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Btree *pBt;
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pBt = sqliteMalloc( sizeof(*pBt) );
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if( pBt==0 ){
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**ppBtree = 0;
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return SQLITE_NOMEM;
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}
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rc = sqlitepager_open(&pBt->pPager, zFilename, 100);
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if( rc!=SQLITE_OK ){
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if( pBt->pPager ) sqlitepager_close(pBt->pPager);
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sqliteFree(pBt);
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*ppBtree = 0;
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return rc;
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}
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pBt->pCursor = 0;
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pBt->page1 = 0;
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*ppBtree = pBt;
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return SQLITE_OK;
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}
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/*
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** Close an open database and invalidate all cursors.
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*/
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int sqliteBtreeClose(Btree *pBt){
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while( pBt->pCursor ){
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sqliteBtreeCloseCursor(pBt->pCursor);
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}
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sqlitepager_close(pBt->pPager);
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sqliteFree(pBt);
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return SQLITE_OK;
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}
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/*
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** Start a new transaction
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*/
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int sqliteBtreeBeginTrans(Btree *pBt){
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int rc;
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if( pBt->inTrans ) return SQLITE_ERROR;
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if( pBt->page1==0 ){
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rc = sqlitepager_get(pBt->pPager, 1, &pBt->page1);
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if( rc!=SQLITE_OK ) return rc;
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}
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rc = sqlitepager_write(pBt->page1);
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if( rc==SQLITE_OK ){
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pBt->inTrans = 1;
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}
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return rc;
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}
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/*
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** Get a reference to page1 of the database file. This will
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** also acquire a readlock on that file.
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*/
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static int lockBtree(Btree *pBt){
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int rc;
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if( pBt->page1 ) return SQLITE_OK;
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rc = sqlitepager_get(pBt->pPager, 1, &pBt->page1);
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if( rc!=SQLITE_OK ) return rc;
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/* Sanity checking on the database file format */
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return rc;
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}
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/*
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** Remove the last reference to the database file. This will
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** remove the read lock.
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*/
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static void unlockBtree(Btree *pBt){
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if( pBt->pCursor==0 && pBt->page1!=0 ){
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sqlitepager_unref(pBt->page1);
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pBt->page1 = 0;
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pBt->inTrans = 0;
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}
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}
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/*
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** Commit the transaction currently in progress. All cursors
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** must be closed before this routine is called.
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*/
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int sqliteBtreeCommit(Btree *pBt){
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int rc;
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assert( pBt->pCursor==0 );
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rc = sqlitepager_commit(pBt->pPager);
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unlockBtree(pBt);
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return rc;
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}
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/*
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** Rollback the transaction in progress. All cursors must be
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** closed before this routine is called.
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*/
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int sqliteBtreeRollback(Btree *pBt){
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int rc;
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assert( pBt->pCursor==0 );
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rc = sqlitepager_rollback(pBt->pPager);
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unlockBtree(pBt);
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return rc;
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}
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/*
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** Create a new cursor. The act of acquiring a cursor
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** gets a read lock on the database file.
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*/
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int sqliteBtreeCursor(Btree *pBt, BtCursor **ppCur){
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int rc;
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BtCursor *pCur;
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if( pBt->page1==0 ){
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rc = lockBtree(pBt);
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if( rc!=SQLITE_OK ){
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*ppCur = 0;
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return rc;
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}
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}
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pCur = sqliteMalloc( sizeof(*pCur) );
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if( pCur==0 ){
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*ppCur = 0;
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unlockBtree(pBt);
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return SQLITE_NOMEM;
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}
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pCur->pPrev = 0;
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pCur->pNext = pBt->pCursor;
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if( pCur->pNext ){
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pCur->pNext->pPrev = pCur;
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}
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pBt->pCursor = pCur;
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pCur->pBt = pBt;
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pCur->nLevel = 1;
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pCur->aLevel[0].pgno = 1;
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pCur->aLevel[0].aPage = pBt->page1;
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pCur->aLevel[0].idx = 0;
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}
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/*
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** Close a cursor.
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*/
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int sqliteBtreeCloseCursor(BtCursor *pCur){
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Btree *pBt = pCur->pBt;
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int i;
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if( pCur->pPrev ){
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pCur->pPrev->pNext = pCur->pNext;
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}else{
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pBt->pCursor = pCur->pNext;
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}
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if( pCur->pNext ){
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pCur->pNext->pPrev = pCur->pPrev;
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}
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for(i=pCur->nLevel-1; i>0; i--){
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sqlitepager_unref(pCur->aLevel[i].aPage);
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}
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if( pBt->pCursor==0 && pBt->inTrans==0 ){
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unlockBtree(pBt);
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}
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sqliteFree(pCur);
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}
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int sqliteBtreeKeySize(BtCursor *pCur){
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int nEntry;
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u32 *aPage;
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BtIdxpt *pIdx;
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int offset;
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if( !pCur->valid ) return 0;
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pIdx = &pCur->aLevel[pCur->nLevel-1];
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aPage = pIdx->aPage;
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offset = (pIdx->pgno==1)*EXTRA_PAGE_1_CELLS;
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nEntry = aPage[offset];
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if( pIdx->idx<nEntry ){
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}
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int sqliteBtreeKey(BtCursor*, int offset, int amt, char *zBuf);
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int sqliteBtreeDataSize(BtCursor*);
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int sqliteBtreeData(BtCursor*, int offset, int amt, char *zBuf);
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/* Move the cursor so that it points to an entry near pKey.
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** Return 0 if the cursor is left pointing exactly at pKey.
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** Return -1 if the cursor points to the largest entry less than pKey.
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** Return 1 if the cursor points to the smallest entry greater than pKey.
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*/
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int sqliteBtreeMoveto(BtCursor*, void *pKey, int nKey);
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int sqliteBtreeDelete(BtCursor*);
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int sqliteBtreeInsert(BtCursor*, void *pKey, int nKey, void *pData, int nData);
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int sqliteBtreeNext(BtCursor*);
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