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 1.448 2008/03/29 16:01:04 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"

/*
** Obtain a lock on the table whose root page is iTab.  The
** lock is a write lock if isWritelock is true or a read lock
** if it is false.
*/
int sqlite3BtreeLockTable(Btree *p, int iTab, u8 isWriteLock){
  int rc = SQLITE_OK;

  u8 lockType = (isWriteLock?WRITE_LOCK:READ_LOCK);


  sqlite3BtreeEnter(p);
  rc = queryTableLock(p, iTab, lockType);
  if( rc==SQLITE_OK ){
    rc = lockTable(p, iTab, lockType);
  }
  sqlite3BtreeLeave(p);

  return rc;
}
#endif

#ifndef SQLITE_OMIT_INCRBLOB
/*
** Argument pCsr must be a cursor opened for writing on an 

**     CREATE INDEX
**     DROP INDEX
**     creating ID lists
**     BEGIN TRANSACTION
**     COMMIT
**     ROLLBACK
**
** $Id: build.c,v 1.478 2008/04/01 03:27:39 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** This routine is called when a new SQL statement is beginning to
** be parsed.  Initialize the pParse structure as needed.

  if( 0==(pVdbe = sqlite3GetVdbe(pParse)) ){
    return;
  }

  for(i=0; i<pParse->nTableLock; i++){
    TableLock *p = &pParse->aTableLock[i];
    int p1 = p->iDb;
    if( p->isWriteLock ){
      p1 = -1*(p1+1);
    }
    sqlite3VdbeAddOp4(pVdbe, OP_TableLock, p1, p->iTab, 0, p->zName, P4_STATIC);

  }
}
#else
  #define codeTableLocks(x)
#endif

/*

**
** Various scripts scan this source file in order to generate HTML
** documentation, headers files, or other derived files.  The formatting
** of the code in this file is, therefore, important.  See other comments
** in this file for details.  If in doubt, do not deviate from existing
** commenting and indentation practices when changing or adding code.
**
** $Id: vdbe.c,v 1.724 2008/04/01 00:36:10 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>
#include "vdbeInt.h"

/*
** The following global variable is incremented every time a cursor

  }else{
    p->expired = 1;
  }
  break;
}

#ifndef SQLITE_OMIT_SHARED_CACHE
/* Opcode: TableLock P1 P2 * P4 *
**
** Obtain a lock on a particular table. This instruction is only used when
** the shared-cache feature is enabled. 
**
** If P1 is not negative, then it is the index of the database
** in sqlite3.aDb[] and a read-lock is required. If P1 is negative, a 
** write-lock is required. In this case the index of the database is the 
** absolute value of P1 minus one (iDb = abs(P1) - 1;) and a write-lock is
** required. 
**
** P2 contains the root-page of the table to lock.
**
** P4 contains a pointer to the name of the table being locked. This is only
** used to generate an error message if the lock cannot be obtained.
*/
case OP_TableLock: {
  int p1 = pOp->p1; 
  u8 isWriteLock = (p1<0);
  if( isWriteLock ){
    p1 = (-1*p1)-1;
  }
  assert( p1>=0 && p1<db->nDb );
  assert( (p->btreeMask & (1<<p1))!=0 );

  rc = sqlite3BtreeLockTable(db->aDb[p1].pBt, pOp->p2, isWriteLock);
  if( rc==SQLITE_LOCKED ){
    const char *z = pOp->p4.z;
    sqlite3SetString(&p->zErrMsg, "database table is locked: ", z, (char*)0);
  }
  break;
}