Import the LSM code from SQLite4 for use in an experimental virtual table.

NB: This is a speculative experiment and could easily result in a dead-end
branch.

FossilOrigin-Name: 3d930501a2acb7f20932cfeb4e3fe308b4569cd6

ext/lsm1/lsm_mutex.c

@@ -0,0 +1,88 @@
+/*
+** 2012-01-30
+**
+** 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.
+**
+*************************************************************************
+**
+** Mutex functions for LSM.
+*/
+#include "lsmInt.h"
+
+/*
+** Allocate a new mutex.
+*/
+int lsmMutexNew(lsm_env *pEnv, lsm_mutex **ppNew){
+  return pEnv->xMutexNew(pEnv, ppNew);
+}
+
+/*
+** Return a handle for one of the static mutexes.
+*/
+int lsmMutexStatic(lsm_env *pEnv, int iMutex, lsm_mutex **ppStatic){
+  return pEnv->xMutexStatic(pEnv, iMutex, ppStatic);
+}
+
+/*
+** Free a mutex allocated by lsmMutexNew().
+*/
+void lsmMutexDel(lsm_env *pEnv, lsm_mutex *pMutex){
+  if( pMutex ) pEnv->xMutexDel(pMutex);
+}
+
+/*
+** Enter a mutex.
+*/
+void lsmMutexEnter(lsm_env *pEnv, lsm_mutex *pMutex){
+  pEnv->xMutexEnter(pMutex);
+}
+
+/*
+** Attempt to enter a mutex, but do not block. If successful, return zero.
+** Otherwise, if the mutex is already held by some other thread and is not
+** entered, return non zero.
+**
+** Each successful call to this function must be matched by a call to
+** lsmMutexLeave().
+*/
+int lsmMutexTry(lsm_env *pEnv, lsm_mutex *pMutex){
+  return pEnv->xMutexTry(pMutex);
+}
+
+/*
+** Leave a mutex.
+*/
+void lsmMutexLeave(lsm_env *pEnv, lsm_mutex *pMutex){
+  pEnv->xMutexLeave(pMutex);
+}
+
+#ifndef NDEBUG
+/*
+** Return non-zero if the mutex passed as the second argument is held
+** by the calling thread, or zero otherwise. If the implementation is not 
+** able to tell if the mutex is held by the caller, it should return
+** non-zero.
+**
+** This function is only used as part of assert() statements.
+*/
+int lsmMutexHeld(lsm_env *pEnv, lsm_mutex *pMutex){
+  return pEnv->xMutexHeld ? pEnv->xMutexHeld(pMutex) : 1;
+}
+
+/*
+** Return non-zero if the mutex passed as the second argument is not 
+** held by the calling thread, or zero otherwise. If the implementation 
+** is not able to tell if the mutex is held by the caller, it should 
+** return non-zero.
+**
+** This function is only used as part of assert() statements.
+*/
+int lsmMutexNotHeld(lsm_env *pEnv, lsm_mutex *pMutex){
+  return pEnv->xMutexNotHeld ? pEnv->xMutexNotHeld(pMutex) : 1;
+}
+#endif