SQLite

**
*************************************************************************
** 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 1.216 2004/06/12 00:42:35 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>

/*
** A pointer to this structure is used to communicate information

/*
** This routine sets the busy callback for an Sqlite database to the
** given callback function with the given argument.
*/
void sqlite3_busy_handler(
  sqlite *db,
  int (*xBusy)(void*,const char*,int),
  void *pArg
){
  db->busyHandler.xFunc = xBusy;
  db->busyHandler.pArg = pArg;
}

#ifndef SQLITE_OMIT_PROGRESS_CALLBACK

** 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 1.123 2004/06/10 23:35:50 drh Exp $
*/
#include "os.h"         /* Must be first to enable large file support */
#include "sqliteInt.h"
#include "pager.h"
#include <assert.h>
#include <string.h>

  ** will require a journal playback.
  */
  do {
    rc = sqlite3OsLock(&pPager->fd, EXCLUSIVE_LOCK);
  }while( rc==SQLITE_BUSY && 
      pPager->pBusyHandler && 
      pPager->pBusyHandler->xFunc && 
      pPager->pBusyHandler->xFunc(pPager->pBusyHandler->pArg, "", busy++)
  );
  if( rc!=SQLITE_OK ){
    return rc;
  }
  pPager->state = PAGER_EXCLUSIVE;

  while( pList ){

  if( pPager->nRef==0 && !pPager->memDb ){
    int busy = 1;
    do {
      rc = sqlite3OsLock(&pPager->fd, SHARED_LOCK);
    }while( rc==SQLITE_BUSY && 
        pPager->pBusyHandler && 
        pPager->pBusyHandler->xFunc && 
        pPager->pBusyHandler->xFunc(pPager->pBusyHandler->pArg, "", busy++)
    );
    if( rc!=SQLITE_OK ){
      return rc;
    }
    pPager->state = PAGER_SHARED;

    /* If a journal file exists, and there is no RESERVED lock on the

    }else{
      int busy = 1;
      do {
        rc = sqlite3OsLock(&pPager->fd, RESERVED_LOCK);
      }while( rc==SQLITE_BUSY && 
          pPager->pBusyHandler && 
          pPager->pBusyHandler->xFunc && 
          pPager->pBusyHandler->xFunc(pPager->pBusyHandler->pArg, "", busy++)
      );
      if( rc!=SQLITE_OK ){
        return rc;
      }
      pPager->nMaster = nMaster;
      pPager->state = PAGER_RESERVED;
      pPager->dirtyCache = 0;

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the SQLite library
** presents to client programs.
**
** @(#) $Id: sqlite.h.in,v 1.99 2004/06/12 00:42:35 danielk1977 Exp $
*/
#ifndef _SQLITE_H_
#define _SQLITE_H_
#include <stdarg.h>     /* Needed for the definition of va_list */

/*
** Make sure we can call this stuff from C++.

** Sqlite is re-entrant, so the busy handler may start a new query. 
** (It is not clear why anyone would every want to do this, but it
** is allowed, in theory.)  But the busy handler may not close the
** database.  Closing the database from a busy handler will delete 
** data structures out from under the executing query and will 
** probably result in a coredump.
*/
void sqlite3_busy_handler(sqlite*, int(*)(void*,const char*,int), void*);

/*
** This routine sets a busy handler that sleeps for a while when a
** table is locked.  The handler will sleep multiple times until 
** at least "ms" milleseconds of sleeping have been done.  After
** "ms" milleseconds of sleeping, the handler returns 0 which
** causes sqlite3_exec() to return SQLITE_BUSY.

/*
** 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 1.283 2004/06/12 00:42:35 danielk1977 Exp $
*/
#include "config.h"
#include "sqlite3.h"
#include "hash.h"
#include "parse.h"
#include <stdio.h>
#include <stdlib.h>

**
** The sqlite.busyHandler member of the sqlite struct contains the busy
** callback for the database handle. Each pager opened via the sqlite
** handle is passed a pointer to sqlite.busyHandler. The busy-handler
** callback is currently invoked only from within pager.c.
*/
struct BusyHandler {
  int (*xFunc)(void *,const char*,int);  /* The busy callback */
  void *pArg;                            /* First arg to busy callback */
};

/*
** Each database is an instance of the following structure.
**
** The sqlite.temp_store determines where temporary database files
** are stored.  If 1, then a file is created to hold those tables.  If

/*
** 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.
**
*************************************************************************
** A TCL Interface to SQLite
**
** $Id: tclsqlite.c,v 1.83 2004/06/10 10:50:38 danielk1977 Exp $
*/
#ifndef NO_TCL     /* Omit this whole file if TCL is unavailable */

#include "sqliteInt.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>

  Tcl_Free((char*)pDb);
}

/*
** This routine is called when a database file is locked while trying
** to execute SQL.
*/
static int DbBusyHandler(void *cd, const char *zTable, int nTries){
  SqliteDb *pDb = (SqliteDb*)cd;
  int rc;
  char zVal[30];
  char *zCmd;
  Tcl_DString cmd;

  Tcl_DStringInit(&cmd);
  Tcl_DStringAppend(&cmd, pDb->zBusy, -1);
  Tcl_DStringAppendElement(&cmd, zTable);
  sprintf(zVal, " %d", nTries);
  Tcl_DStringAppend(&cmd, zVal, -1);
  zCmd = Tcl_DStringValue(&cmd);
  rc = Tcl_Eval(pDb->interp, zCmd);
  Tcl_DStringFree(&cmd);
  if( rc!=TCL_OK || atoi(Tcl_GetStringResult(pDb->interp)) ){
    return 0;
  }
  return 1;

**
** 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 1.366 2004/06/12 00:42:35 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>
#include "vdbeInt.h"

/*

  if( pBt ){
    if( db->nMaster<0 ){
      db->nMaster = strlen(sqlite3BtreeGetFilename(db->aDb[0].pBt))+20;
    }
    rc = sqlite3BtreeBeginTrans(pBt, pOp->p2, db->nMaster);
    if( rc==SQLITE_BUSY ){
        if( db->busyHandler.xFunc==0 ){
          p->pc = pc;
          p->rc = SQLITE_BUSY;
          p->pTos = pTos;
          return SQLITE_BUSY;
        }else{
          sqlite3SetString(&p->zErrMsg, sqlite3ErrStr(rc), (char*)0);
        }
    }
    if( rc!=SQLITE_OK && rc!=SQLITE_READONLY && rc!=SQLITE_BUSY ){
      goto abort_due_to_error;
    }
  }
  break;
}

/* Opcode: ReadCookie P1 P2 *

    pCur->pIncrKey = &pCur->pKeyInfo->incrKey;
    pCur->pKeyInfo->enc = p->db->enc;
  }else{
    pCur->pIncrKey = &pCur->bogusIncrKey;
  }
  switch( rc ){
    case SQLITE_BUSY: {
      if( db->busyHandler.xFunc ){
        p->pc = pc;
        p->rc = SQLITE_BUSY;
        p->pTos = &pTos[1 + (pOp->p2<=0)]; /* Operands must remain on stack */
        return SQLITE_BUSY;
      }else{
        sqlite3SetString(&p->zErrMsg, sqlite3ErrStr(rc), (char*)0);
      }
      break;
    }
    case SQLITE_OK: {
      int flags = sqlite3BtreeFlags(pCur->pCursor);
      pCur->intKey = (flags & BTREE_INTKEY)!=0;
      pCur->zeroData = (flags & BTREE_ZERODATA)!=0;
      break;
    }

# 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.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this script is database locks.
#
# $Id: lock.test,v 1.23 2004/06/10 00:29:12 drh Exp $


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

# Create an alternative connection to the database
#

  catchsql {SELECT * FROM t2} db2
} {0 {9 8}}

# If the other thread (the one that does not hold the transaction with
# a RESERVED lock) tries to get a RESERVED lock, we get a busy callback.
#
do_test lock-2.3 {
  proc callback {args} {
    set ::callback_value $args
    break
  }
  set ::callback_value {}
  db2 busy callback
  set r [catch {execsql {UPDATE t1 SET a=b, b=a} db2} msg]
  lappend r $msg
  lappend r $::callback_value
} {1 {database is locked} {{} 1}}
do_test lock-2.4 {
  proc callback {file count} {
    lappend ::callback_value $count
    if {$count>4} break
  }
  set ::callback_value {}
  db2 busy callback
  set r [catch {execsql {UPDATE t1 SET a=b, b=a} db2} msg]
  lappend r $msg
  lappend r $::callback_value
} {1 {database is locked} {1 2 3 4 5}}
do_test lock-2.5 {
  proc callback {file count} {
    lappend ::callback_value $count
    if {$count>4} break
  }
  set ::callback_value {}
  db2 busy callback
  set r [catch {execsql {SELECT * FROM t1} db2} msg]
  lappend r $msg
  lappend r $::callback_value
} {0 {2 1} {}}

# In this test, the 3rd invocation of the busy callback causes
# the first thread to release its transaction.  That allows the
# second thread to continue.
#
do_test lock-2.6 {
  proc callback {file count} {
    lappend ::callback_value $count
    if {$count>2} {
      execsql {ROLLBACK}
    }
  }
  set ::callback_value {}
  db2 busy callback
  set r [catch {execsql {SELECT * FROM t2} db2} msg]
  lappend r $msg
  lappend r $::callback_value
} {0 {9 8} {}}
do_test lock-2.7 {
  proc callback {file count} {
    lappend ::callback_value $count
    if {$count>2} {
      execsql {ROLLBACK}
    }
  }
  set ::callback_value {}
  db2 busy callback

} {1 {database is locked}}
do_test lock-4.2 {
  set ::callback_value {}
  set rc [catch {db2 eval {UPDATE t1 SET a=0}} msg]
  lappend rc $msg $::callback_value
} {1 {database is locked} {}}
do_test lock-4.3 {
  proc callback {file count} {
    lappend ::callback_value $count
    if {$count>4} break
  }
  db2 busy callback
  set rc [catch {db2 eval {UPDATE t1 SET a=0}} msg]
  lappend rc $msg $::callback_value
} {1 {database is locked} {1 2 3 4 5}}

extern char *sqlite_mprintf(const char *zFormat, ...);
extern char *sqlite_vmprintf(const char *zFormat, va_list);

/*
** When a lock occurs, yield.
*/
static int db_is_locked(void *NotUsed, const char *zNotUsed, int iNotUsed){
  /* sched_yield(); */
  if( verbose ) printf("BUSY %s\n", (char*)NotUsed);
  usleep(100);
  return 1;
}

/*