SQLite

**
******************************************************************************
**
** This file contains code that is specific to particular operating
** systems.  The purpose of this file is to provide a uniform abstraction
** on which the rest of SQLite can operate.
*/
#include "os.h"          /* Must be first to enable large file support */
#include "sqliteInt.h"

#if OS_UNIX
# include <time.h>
# ifndef O_LARGEFILE
#  define O_LARGEFILE 0
# endif
# ifndef O_NOFOLLOW

int sqliteOsSeek(OsFile *id, off_t offset){
  SEEK(offset/1024 + 1);
#if OS_UNIX
  lseek(id->fd, offset, SEEK_SET);
  return SQLITE_OK;
#endif
#if OS_WIN
  {
    LONG upperBits = offset>>32;
    SetFilePointer(id->h, offset, &upperBits, FILE_BEGIN);
  }
  return SQLITE_OK;
#endif
}

/*
** Make sure all writes to a particular file are committed to disk.
*/

*/
int sqliteOsTruncate(OsFile *id, off_t nByte){
  SimulateIOError(SQLITE_IOERR);
#if OS_UNIX
  return ftruncate(id->fd, nByte)==0 ? SQLITE_OK : SQLITE_IOERR;
#endif
#if OS_WIN
  {
    LONG upperBits = nByte>>32;
    SetFilePointer(id->h, nByte, &upperBits, FILE_BEGIN);
    SetEndOfFile(id->h);
  }
  return SQLITE_OK;
#endif
}

/*
** Determine the current size of a file in bytes
*/
int sqliteOsFileSize(OsFile *id, off_t *pSize){
#if OS_UNIX
  struct stat buf;
  SimulateIOError(SQLITE_IOERR);
  if( fstat(id->fd, &buf)!=0 ){
    return SQLITE_IOERR;
  }
  *pSize = buf.st_size;
  return SQLITE_OK;
#endif
#if OS_WIN
  DWORD upperBits, lowerBits;
  SimulateIOError(SQLITE_IOERR);
  lowerBits = GetFileSize(id->h, &upperBits);
  *pSize = (((off_t)upperBits)<<32) + lowerBits;
  return SQLITE_OK;
#endif
}

#if OS_WIN
/*
** Return true (non-zero) if we are running under WinNT, Win2K or WinXP.

** This header file (together with is companion C source-code file
** "os.c") attempt to abstract the underlying operating system so that
** the SQLite library will work on both POSIX and windows systems.
*/
#ifndef _SQLITE_OS_H_
#define _SQLITE_OS_H_

/*
** These #defines should enable >2GB file support on Posix if the
** underlying operating system supports it.  If the OS lacks
** large file support, or if the OS is windows, these should be no-ops.
*/
#define _LARGE_FILE       1
#define _FILE_OFFSET_BITS 64
#define _LARGEFILE_SOURCE 1

/*
** Figure out if we are dealing with Unix or Windows.
*/
#ifndef OS_UNIX
# ifndef OS_WIN
#  if defined(_WIN32) || defined(WIN32) || defined(__CYGWIN__) || defined(__MINGW32__) || defined(__BORLANDC__)
#    define OS_WIN 1
#    define OS_UNIX 0
#  else
#    define OS_WIN 0

#include <windows.h>
#include <winbase.h>
  typedef struct OsFile OsFile;
  struct OsFile {
    HANDLE h;               /* Handle for accessing the file */
    int locked;             /* 0: unlocked, <0: write lock, >0: read lock */
  };
# ifdef _MSC_VER
    typedef __int64 off_t;
# else
    typedef long long off_t;
# endif
# define SQLITE_TEMPNAME_SIZE (MAX_PATH+50)
# define SQLITE_MIN_SLEEP_MS 1
#endif

int sqliteOsDelete(const char*);
int sqliteOsFileExists(const char*);
int sqliteOsOpenReadWrite(const char*, OsFile*, int*);

** 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 1.55 2002/11/06 14:08:11 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>

/*
** The page cache as a whole is always in one of the following
** states:
**

}


proc chng {date desc} {
  puts "<DT><B>$date</B></DT>"
  puts "<DD><P><UL>$desc</UL></P></DD>"
}

chng {2002 Nov ?? (2.7.4)} {
<li>Database files can now grow to be up to 2^41 bytes.  The old limit
    was 2^31 bytes.</li>
}

chng {2002 Oct 30 (2.7.3)} {
<li>Various compiler compatibility fixes.</li>
<li>Fix a bug in the "expr IN ()" operator.</li>
<li>Accept column names in parentheses.</li>
<li>Fix a problem with string memory management in the VDBE</li>
<li>Fix a bug in the "table_info" pragma"</li>

#
# Run this script to generated a faq.html output file
#
set rcsid {$Id: faq.tcl,v 1.21 2002/11/06 14:08:12 drh Exp $}

puts {<html>
<head>
  <title>SQLite Frequently Asked Questions</title>
</head>
<body bgcolor="white">
<h1 align="center">Frequently Asked Questions</h1>

ORDER BY name
</pre></blockquote>
}

faq {
  Are there any known size limits to SQLite databases?
} {
  <p>As of version 2.7.4, 
  SQLite can handle databases up to 2^41 bytes (2 terabytes)
  in size on both Windows and Unix.  Older version of SQLite
  were limited to databases of 2^31 bytes (2 gigabytes).</p>


  <p>SQLite arbitrarily limits the amount of data in one row to 1 megabyte.
  There is a single #define in the source code that can be changed to raise
  this limit as high as 16 megabytes if desired.</p>

  <p>There is a theoretical limit of about 2^32 (4 billion) rows
  in a single table, but this limit has never been tested.</p>

  There is also a theoretical limit of about 2^32
  tables and indices.</p>


  <p>The name and "CREATE TABLE" statement for a table must fit entirely
  within a 1-megabyte row of the SQLITE_MASTER table.  Other than this,
  there are no constraints on the length of the name of a table, or on the
  number of columns, etc.  Indices are similarly unconstrained.</p>

  <p>The names of tables, indices, view, triggers, and columns can be
  as long as desired.  However, the names of SQL functions (as created
  by the <a href="c_interface.html#cfunc">sqlite_create_function()</a> API)
  may not exceed 255 characters in length.</p>
}
















faq {
  What is the maximum size of a VARCHAR in SQLite?
} {
  <p>Remember, SQLite is typeless.  A VARCHAR column can hold as much
  data as any other column.  The total amount of data in a single row
  of the database is limited to 1 megabyte.  You can increase this limit
  to 16 megabytes, if you need to, by adjusting a single #define in the

#
# Run this TCL script to generate HTML for the index.html file.
#
set rcsid {$Id: index.tcl,v 1.70 2002/11/06 14:08:12 drh Exp $}

puts {<html>
<head><title>SQLite: An Embeddable SQL Database Engine</title></head>
<body bgcolor=white>
<h1 align=center>SQLite<br>An Embeddable SQL Database Engine</h1>
<p align=center>}
puts "This page was last modified on [lrange $rcsid 3 4] UTC<br>"

<li>Implements most of SQL92.
    (<a href="omitted.html">Features not supported</a>)</li>
<li>A complete database (with multiple tables and indices) is
    stored in a single disk file.</li>
<li>Atomic commit and rollback protect data integrity.</li>
<li>Database files can be freely shared between machines with
    different byte orders.</li>
<li>Supports databases up to 2 terabytes (2^41 bytes) in size.</li>
<li>Small memory footprint: less than 25K lines of C code.</li>
<li><a href="speed.html">Four times faster</a> than PostgreSQL.
    Twice as fast as SQLite 1.0.</li>
<li>Very simple 
<a href="c_interface.html">C/C++ interface</a> requires the use of only
three functions and one opaque structure.</li>
<li><a href="tclsqlite.html">TCL bindings</a> included.