Break up the mutex implementation into separate source files, one

each for unix, w32, and os2. (CVS 4312)

FossilOrigin-Name: fc5cd71aef5ac194f51d73350d773d532020967e

src/mutex_w32.c

@@ -0,0 +1,181 @@
+/*
+** 2007 August 14
+**
+** 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 the C functions that implement mutexes for win32
+**
+** $Id: mutex_w32.c,v 1.1 2007/08/28 16:34:43 drh Exp $
+*/
+#include "sqliteInt.h"
+
+/*
+** The code in this file is only used if we are compiling multithreaded
+** on a win32 system.
+*/
+#ifdef SQLITE_MUTEX_WIN32
+
+/*
+** Each recursive mutex is an instance of the following structure.
+*/
+struct sqlite3_mutex {
+  CRITICAL_SECTION mutex;    /* Mutex controlling the lock */
+  int id;                    /* Mutex type */
+  int nRef;                  /* Number of enterances */
+  DWORD owner;               /* Thread holding this mutex */
+};
+
+/*
+** The sqlite3_mutex_alloc() routine allocates a new
+** mutex and returns a pointer to it.  If it returns NULL
+** that means that a mutex could not be allocated.  SQLite
+** will unwind its stack and return an error.  The argument
+** to sqlite3_mutex_alloc() is one of these integer constants:
+**
+** <ul>
+** <li>  SQLITE_MUTEX_FAST               0
+** <li>  SQLITE_MUTEX_RECURSIVE          1
+** <li>  SQLITE_MUTEX_STATIC_MASTER      2
+** <li>  SQLITE_MUTEX_STATIC_MEM         3
+** <li>  SQLITE_MUTEX_STATIC_PRNG        4
+** </ul>
+**
+** The first two constants cause sqlite3_mutex_alloc() to create
+** a new mutex.  The new mutex is recursive when SQLITE_MUTEX_RECURSIVE
+** is used but not necessarily so when SQLITE_MUTEX_FAST is used.
+** The mutex implementation does not need to make a distinction
+** between SQLITE_MUTEX_RECURSIVE and SQLITE_MUTEX_FAST if it does
+** not want to.  But SQLite will only request a recursive mutex in
+** cases where it really needs one.  If a faster non-recursive mutex
+** implementation is available on the host platform, the mutex subsystem
+** might return such a mutex in response to SQLITE_MUTEX_FAST.
+**
+** The other allowed parameters to sqlite3_mutex_alloc() each return
+** a pointer to a static preexisting mutex.  Three static mutexes are
+** used by the current version of SQLite.  Future versions of SQLite
+** may add additional static mutexes.  Static mutexes are for internal
+** use by SQLite only.  Applications that use SQLite mutexes should
+** use only the dynamic mutexes returned by SQLITE_MUTEX_FAST or
+** SQLITE_MUTEX_RECURSIVE.
+**
+** Note that if one of the dynamic mutex parameters (SQLITE_MUTEX_FAST
+** or SQLITE_MUTEX_RECURSIVE) is used then sqlite3_mutex_alloc()
+** returns a different mutex on every call.  But for the static 
+** mutex types, the same mutex is returned on every call that has
+** the same type number.
+*/
+sqlite3_mutex *sqlite3_mutex_alloc(int iType){
+  sqlite3_mutex *p;
+
+  switch( iType ){
+    case SQLITE_MUTEX_FAST:
+    case SQLITE_MUTEX_RECURSIVE: {
+      p = sqlite3MallocZero( sizeof(*p) );
+      if( p ){
+        p->id = iType;
+        InitializeCriticalSection(&p->mutex);
+      }
+      break;
+    }
+    default: {
+      static sqlite3_mutex staticMutexes[5];
+      static int isInit = 0;
+      while( !isInit ){
+        static long lock = 0;
+        if( InterlockedIncrement(&lock)==1 ){
+          int i;
+          for(i=0; i<sizeof(staticMutexes)/sizeof(staticMutexes[0]); i++){
+            InitializeCriticalSection(&staticMutexes[i].mutex);
+          }
+          isInit = 1;
+        }else{
+          Sleep(1);
+        }
+      }
+      assert( iType-2 >= 0 );
+      assert( iType-2 < sizeof(staticMutexes)/sizeof(staticMutexes[0]) );
+      p = &staticMutexes[iType-2];
+      p->id = iType;
+      break;
+    }
+  }
+  return p;
+}
+
+
+/*
+** This routine deallocates a previously
+** allocated mutex.  SQLite is careful to deallocate every
+** mutex that it allocates.
+*/
+void sqlite3_mutex_free(sqlite3_mutex *p){
+  assert( p );
+  assert( p->nRef==0 );
+  assert( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE );
+  DeleteCriticalSection(&p->mutex);
+  sqlite3_free(p);
+}
+
+/*
+** The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt
+** to enter a mutex.  If another thread is already within the mutex,
+** sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return
+** SQLITE_BUSY.  The sqlite3_mutex_try() interface returns SQLITE_OK
+** upon successful entry.  Mutexes created using SQLITE_MUTEX_RECURSIVE can
+** be entered multiple times by the same thread.  In such cases the,
+** mutex must be exited an equal number of times before another thread
+** can enter.  If the same thread tries to enter any other kind of mutex
+** more than once, the behavior is undefined.
+*/
+void sqlite3_mutex_enter(sqlite3_mutex *p){
+  assert( p );
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );
+  EnterCriticalSection(&p->mutex);
+  p->owner = GetCurrentThreadId(); 
+  p->nRef++;
+}
+int sqlite3_mutex_try(sqlite3_mutex *p){
+  int rc;
+  assert( p );
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );
+  if( TryEnterCriticalSection(&p->mutex) ){
+    p->owner = GetCurrentThreadId();
+    p->nRef++;
+    rc = SQLITE_OK;
+  }else{
+    rc = SQLITE_BUSY;
+  }
+  return rc;
+}
+
+/*
+** The sqlite3_mutex_leave() routine exits a mutex that was
+** previously entered by the same thread.  The behavior
+** is undefined if the mutex is not currently entered or
+** is not currently allocated.  SQLite will never do either.
+*/
+void sqlite3_mutex_leave(sqlite3_mutex *p){
+  assert( p->nRef>0 );
+  assert( p->owner==GetCurrentThreadId() );
+  p->nRef--;
+  assert( p->nRef==0 || p->id==SQLITE_MUTEX_RECURSIVE );
+  LeaveCriticalSection(&p->mutex);
+}
+
+/*
+** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
+** intended for use only inside assert() statements.
+*/
+int sqlite3_mutex_held(sqlite3_mutex *p){
+  return p==0 || (p->nRef!=0 && p->owner==GetCurrentThreadId());
+}
+int sqlite3_mutex_notheld(sqlite3_mutex *p){
+  return p==0 || p->nRef==0 || p->owner!=GetCurrentThreadId();
+}
+#endif /* SQLITE_MUTEX_WIN */