os_common.h

sqlite-3.4.1,嵌入式数据库.是一个功能强大的开源数据库,给学习和研发以及小型公司的发展带来了全所未有的好处.

/*
** 2004 May 22
**
** 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 contains macros and a little bit of code that is common to
** all of the platform-specific files (os_*.c) and is #included into those
** files.
**
** This file should be #included by the os_*.c files only.  It is not a
** general purpose header file.
*/

/*
** At least two bugs have slipped in because we changed the MEMORY_DEBUG
** macro to SQLITE_DEBUG and some older makefiles have not yet made the
** switch.  The following code should catch this problem at compile-time.
*/
#ifdef MEMORY_DEBUG
# error "The MEMORY_DEBUG macro is obsolete.  Use SQLITE_DEBUG instead."
#endif


/*
 * When testing, this global variable stores the location of the
 * pending-byte in the database file.
 */
#ifdef SQLITE_TEST
unsigned int sqlite3_pending_byte = 0x40000000;
#endif

int sqlite3_os_trace = 0;
#ifdef SQLITE_DEBUG
#define OSTRACE1(X)         if( sqlite3_os_trace ) sqlite3DebugPrintf(X)
#define OSTRACE2(X,Y)       if( sqlite3_os_trace ) sqlite3DebugPrintf(X,Y)
#define OSTRACE3(X,Y,Z)     if( sqlite3_os_trace ) sqlite3DebugPrintf(X,Y,Z)
#define OSTRACE4(X,Y,Z,A)   if( sqlite3_os_trace ) sqlite3DebugPrintf(X,Y,Z,A)
#define OSTRACE5(X,Y,Z,A,B) if( sqlite3_os_trace ) sqlite3DebugPrintf(X,Y,Z,A,B)
#define OSTRACE6(X,Y,Z,A,B,C) \
    if(sqlite3_os_trace) sqlite3DebugPrintf(X,Y,Z,A,B,C)
#define OSTRACE7(X,Y,Z,A,B,C,D) \
    if(sqlite3_os_trace) sqlite3DebugPrintf(X,Y,Z,A,B,C,D)
#else
#define OSTRACE1(X)
#define OSTRACE2(X,Y)
#define OSTRACE3(X,Y,Z)
#define OSTRACE4(X,Y,Z,A)
#define OSTRACE5(X,Y,Z,A,B)
#define OSTRACE6(X,Y,Z,A,B,C)
#define OSTRACE7(X,Y,Z,A,B,C,D)
#endif

/*
** Macros for performance tracing.  Normally turned off.  Only works
** on i486 hardware.
*/
#ifdef SQLITE_PERFORMANCE_TRACE
__inline__ unsigned long long int hwtime(void){
  unsigned long long int x;
  __asm__("rdtsc\n\t"
          "mov %%edx, %%ecx\n\t"
          :"=A" (x));
  return x;
}
static unsigned long long int g_start;
static unsigned int elapse;
#define TIMER_START       g_start=hwtime()
#define TIMER_END         elapse=hwtime()-g_start
#define TIMER_ELAPSED     elapse
#else
#define TIMER_START
#define TIMER_END
#define TIMER_ELAPSED     0
#endif

/*
** If we compile with the SQLITE_TEST macro set, then the following block
** of code will give us the ability to simulate a disk I/O error.  This
** is used for testing the I/O recovery logic.
*/
#ifdef SQLITE_TEST
int sqlite3_io_error_hit = 0;
int sqlite3_io_error_pending = 0;
int sqlite3_io_error_persist = 0;
int sqlite3_diskfull_pending = 0;
int sqlite3_diskfull = 0;
#define SimulateIOError(CODE)  \
  if( sqlite3_io_error_pending || sqlite3_io_error_hit ) \
     if( sqlite3_io_error_pending-- == 1 \
         || (sqlite3_io_error_persist && sqlite3_io_error_hit) ) \
                { local_ioerr(); CODE; }
static void local_ioerr(){
  IOTRACE(("IOERR\n"));
  sqlite3_io_error_hit = 1;
}
#define SimulateDiskfullError(CODE) \
   if( sqlite3_diskfull_pending ){ \
     if( sqlite3_diskfull_pending == 1 ){ \
       local_ioerr(); \
       sqlite3_diskfull = 1; \
       sqlite3_io_error_hit = 1; \
       CODE; \
     }else{ \
       sqlite3_diskfull_pending--; \
     } \
   }
#else
#define SimulateIOError(A)
#define SimulateDiskfullError(A)
#endif

/*
** When testing, keep a count of the number of open files.
*/
#ifdef SQLITE_TEST
int sqlite3_open_file_count = 0;
#define OpenCounter(X)  sqlite3_open_file_count+=(X)
#else
#define OpenCounter(X)
#endif

/*
** sqlite3GenericMalloc
** sqlite3GenericRealloc
** sqlite3GenericOsFree
** sqlite3GenericAllocationSize
**
** Implementation of the os level dynamic memory allocation interface in terms
** of the standard malloc(), realloc() and free() found in many operating
** systems. No rocket science here.
**
** There are two versions of these four functions here. The version
** implemented here is only used if memory-management or memory-debugging is
** enabled. This version allocates an extra 8-bytes at the beginning of each
** block and stores the size of the allocation there.
**
** If neither memory-management or debugging is enabled, the second
** set of implementations is used instead.
*/
#if defined(SQLITE_ENABLE_MEMORY_MANAGEMENT) || defined (SQLITE_MEMDEBUG)
void *sqlite3GenericMalloc(int n){
  char *p = (char *)malloc(n+8);
  assert(n>0);
  assert(sizeof(int)<=8);
  if( p ){
    *(int *)p = n;
    p += 8;
  }
  return (void *)p;
}
void *sqlite3GenericRealloc(void *p, int n){
  char *p2 = ((char *)p - 8);
  assert(n>0);
  p2 = (char*)realloc(p2, n+8);
  if( p2 ){
    *(int *)p2 = n;
    p2 += 8;
  }
  return (void *)p2;
}
void sqlite3GenericFree(void *p){
  assert(p);
  free((void *)((char *)p - 8));
}
int sqlite3GenericAllocationSize(void *p){
  return p ? *(int *)((char *)p - 8) : 0;
}
#else
void *sqlite3GenericMalloc(int n){
  char *p = (char *)malloc(n);
  return (void *)p;
}
void *sqlite3GenericRealloc(void *p, int n){
  assert(n>0);
  p = realloc(p, n);
  return p;
}
void sqlite3GenericFree(void *p){
  assert(p);
  free(p);
}
/* Never actually used, but needed for the linker */
int sqlite3GenericAllocationSize(void *p){ return 0; }
#endif

/*
** The default size of a disk sector
*/
#ifndef PAGER_SECTOR_SIZE
# define PAGER_SECTOR_SIZE 512
#endif