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 1.263 2005/07/09 02:16:03 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
**
**     Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
**     "Sorting And Searching", pages 473-480. Addison-Wesley
**     Publishing Company, Reading, Massachusetts.

** One or the other of the two processes must give way or there can be
** no progress.  By returning SQLITE_BUSY and not invoking the busy callback
** when A already has a read lock, we encourage A to give up and let B
** proceed.
*/
int sqlite3BtreeBeginTrans(Btree *pBt, int wrflag){
  int rc = SQLITE_OK;



  /* If the btree is already in a write-transaction, or it
  ** is already in a read-transaction and a read-transaction
  ** is requested, this is a no-op.
  */
  if( pBt->inTrans==TRANS_WRITE || (pBt->inTrans==TRANS_READ && !wrflag) ){
    return SQLITE_OK;

    if( rc==SQLITE_OK ){
      pBt->inTrans = (wrflag?TRANS_WRITE:TRANS_READ);
      if( wrflag ) pBt->inStmt = 0;
    }else{
      unlockBtreeIfUnused(pBt);
    }
  }while( rc==SQLITE_BUSY && pBt->inTrans==TRANS_NONE &&
          sqlite3InvokeBusyHandler(pBt->pBusyHandler) );


  return rc;
}

#ifndef SQLITE_OMIT_AUTOVACUUM

/*
** Set the pointer-map entries for all children of page pPage. Also, if

**
*************************************************************************
** Main file for the SQLite library.  The routines in this file
** implement the programmer interface to the library.  Routines in
** other files are for internal use by SQLite and should not be
** accessed by users of the library.
**
** $Id: main.c,v 1.295 2005/07/09 02:16:03 drh Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>

/*
** The following constant value is used by the SQLITE_BIGENDIAN and

  if( (count+1)*1000 > timeout ){
    return 0;
  }
  sqlite3OsSleep(1000);
  return 1;
#endif
}

/*
** Invoke the given busy handler.
**
** This routine is called when an operation failed with a lock.
** If this routine returns non-zero, the lock is retried.  If it
** returns 0, the operation aborts with an SQLITE_BUSY error.
*/
int sqlite3InvokeBusyHandler(BusyHandler *p){
  int rc;
  if( p==0 || p->xFunc==0 || p->nBusy<0 ) return 0;
  rc = p->xFunc(p->pArg, p->nBusy);
  if( rc==0 ){
    p->nBusy = -1;
  }else{
    p->nBusy++;
  }
  return rc; 
}

/*
** This routine sets the busy callback for an Sqlite database to the
** given callback function with the given argument.
*/
int sqlite3_busy_handler(
  sqlite3 *db,
  int (*xBusy)(void*,int),
  void *pArg
){
  if( sqlite3SafetyCheck(db) ){
    return SQLITE_MISUSE;
  }
  db->busyHandler.xFunc = xBusy;
  db->busyHandler.pArg = pArg;
  db->busyHandler.nBusy = 0;
  return SQLITE_OK;
}

#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
/*
** This routine sets the progress callback for an Sqlite database to the
** given callback function with the given argument. The progress callback will

** 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 1.208 2005/07/09 02:16:03 drh Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
#include "os.h"
#include "pager.h"
#include <assert.h>
#include <string.h>

}
#else
#define memoryTruncate(p)
#endif

/*
** Try to obtain a lock on a file.  Invoke the busy callback if the lock
** is currently not available.  Repeat until the busy callback returns
** false or until the lock succeeds.
**
** Return SQLITE_OK on success and an error code if we cannot obtain
** the lock.
*/
static int pager_wait_on_lock(Pager *pPager, int locktype){
  int rc;
  assert( PAGER_SHARED==SHARED_LOCK );
  assert( PAGER_RESERVED==RESERVED_LOCK );
  assert( PAGER_EXCLUSIVE==EXCLUSIVE_LOCK );
  if( pPager->state>=locktype ){
    rc = SQLITE_OK;
  }else{


    do {
      rc = sqlite3OsLock(&pPager->fd, locktype);
    }while( rc==SQLITE_BUSY && sqlite3InvokeBusyHandler(pPager->pBusyHandler) );



    if( rc==SQLITE_OK ){
      pPager->state = locktype;
    }
  }
  return rc;
}

/*
** 2001 September 15
**
** 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.
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.393 2005/07/09 02:16:03 drh Exp $
*/
#ifndef _SQLITEINT_H_
#define _SQLITEINT_H_

/*
** These #defines should enable >2GB file support on Posix if the
** underlying operating system supports it.  If the OS lacks

** handle is passed a pointer to sqlite.busyHandler. The busy-handler
** callback is currently invoked only from within pager.c.
*/
typedef struct BusyHandler BusyHandler;
struct BusyHandler {
  int (*xFunc)(void *,int);  /* The busy callback */
  void *pArg;                /* First arg to busy callback */
  int nBusy;                 /* Incremented with each busy call */
};

/*
** Defer sourcing vdbe.h and btree.h until after the "u8" and 
** "BusyHandler typedefs.
*/
#include "vdbe.h"

void sqlite3ColumnDefault(Vdbe *, Table *, int);
void sqlite3AlterFinishAddColumn(Parse *, Token *);
void sqlite3AlterBeginAddColumn(Parse *, SrcList *);
const char *sqlite3TestErrorName(int);
CollSeq *sqlite3GetCollSeq(sqlite3*, CollSeq *, const char *, int);
char sqlite3AffinityType(const Token*);
void sqlite3Analyze(Parse*, Token*, Token*);
int sqlite3InvokeBusyHandler(BusyHandler*);

#ifdef SQLITE_SSE
#include "sseInt.h"
#endif

#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 1.475 2005/07/09 02:16:03 drh Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>
#include "vdbeInt.h"

/*

  pTos = p->pTos;
  if( sqlite3_malloc_failed ) goto no_mem;
  if( p->popStack ){
    popStack(&pTos, p->popStack);
    p->popStack = 0;
  }
  p->resOnStack = 0;
  db->busyHandler.nBusy = 0;
  CHECK_FOR_INTERRUPT;
  for(pc=p->pc; rc==SQLITE_OK; pc++){
    assert( pc>=0 && pc<p->nOp );
    assert( pTos<=&p->aStack[pc] );
    if( sqlite3_malloc_failed ) goto no_mem;
#ifdef VDBE_PROFILE
    origPc = pc;

# 2005 july 8
#
# 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 test the busy handler
#
# $Id: busy.test,v 1.1 2005/07/09 02:16:03 drh Exp $


set testdir [file dirname $argv0]
source $testdir/tester.tcl

do_test busy-1.1 {
  sqlite3 db2 test.db
  execsql {
    CREATE TABLE t1(x);
    INSERT INTO t1 VALUES(1);
    SELECT * FROM t1
  }
} 1
proc busy x {
  lappend ::busyargs $x
  if {$x>2} {return 1}
  return 0
}
do_test busy-1.2 {
  db busy busy
  db2 eval {begin exclusive}
  catchsql {begin immediate}
} {1 {database is locked}}
do_test busy-1.3 {
  set busyargs
} {0 1 2 3}

db2 close

finish_test