SQLite

        /* Start of free block is off the page */
        return SQLITE_CORRUPT_BKPT; 
      }
      next = get2byte(&data[pc]);
      size = get2byte(&data[pc+2]);
      if( (next>0 && next<=pc+size+3) || pc+size>usableSize ){
        /* Free blocks must be in ascending order. And the last byte of
        ** the free-block must lie on the database page.  */
        return SQLITE_CORRUPT_BKPT; 
      }
      nFree = nFree + size;
      pc = next;
    }

    /* At this point, nFree contains the sum of the offset to the start

          btreeInvokeBusyHandler(pBt) );

  if( rc==SQLITE_OK ){
    if( p->inTrans==TRANS_NONE ){
      pBt->nTransaction++;
#ifndef SQLITE_OMIT_SHARED_CACHE
      if( p->sharable ){
        assert( p->lock.pBtree==p && p->lock.iTable==1 );
        p->lock.eLock = READ_LOCK;
        p->lock.pNext = pBt->pLock;
        pBt->pLock = &p->lock;
      }
#endif
    }
    p->inTrans = (wrflag?TRANS_WRITE:TRANS_READ);

  /* Delete all indices associated with this table. */
  for(pIndex = pTable->pIndex; pIndex; pIndex=pNext){
    pNext = pIndex->pNext;
    assert( pIndex->pSchema==pTable->pSchema );
    if( !db || db->pnBytesFreed==0 ){
      char *zName = pIndex->zName; 
      TESTONLY ( Index *pOld = ) sqlite3HashInsert(
         &pIndex->pSchema->idxHash, zName, sqlite3Strlen30(zName), 0
      );
      assert( db==0 || sqlite3SchemaMutexHeld(db, 0, pIndex->pSchema) );
      assert( pOld==pIndex || pOld==0 );
    }
    freeIndex(db, pIndex);
  }

  sysctlbyname("hw.ncpu", &cpuCount, &len, NULL, 0);
  if( cpuCount>1 ){
    /* defer MT decisions to system malloc */
    _sqliteZone_ = malloc_default_zone();
  }else{
    /* only 1 core, use our own zone to contention over global locks, 
    ** e.g. we have our own dedicated locks */
    bool success;
    malloc_zone_t* newzone = malloc_create_zone(4096, 0);
    malloc_set_zone_name(newzone, "Sqlite_Heap");
    do{
      success = OSAtomicCompareAndSwapPtrBarrier(NULL, newzone, 
                                 (void * volatile *)&_sqliteZone_);
    }while(!_sqliteZone_);
    if( !success ){
      /* somebody registered a zone first */
      malloc_destroy_zone(newzone);
    }
  }
#endif
  UNUSED_PARAMETER(NotUsed);
  return SQLITE_OK;

    /* random NFS retry error, unless during file system support 
     * introspection, in which it actually means what it says */
    return SQLITE_BUSY;
    
  case EACCES: 
    /* EACCES is like EAGAIN during locking operations, but not any other time*/
    if( (sqliteIOErr == SQLITE_IOERR_LOCK) || 
        (sqliteIOErr == SQLITE_IOERR_UNLOCK) || 
        (sqliteIOErr == SQLITE_IOERR_RDLOCK) ||
        (sqliteIOErr == SQLITE_IOERR_CHECKRESERVEDLOCK) ){
      return SQLITE_BUSY;
    }
    /* else fall through */
  case EPERM: 
    return SQLITE_PERM;
    
  /* EDEADLK is only possible if a call to fcntl(F_SETLKW) is made. And

      lock.l_type = F_UNLCK;
      lock.l_whence = SEEK_SET;
      lock.l_start = lock.l_len = 0L;
      if( unixFileLock(pFile, &lock)==0 ){
        pInode->eFileLock = NO_LOCK;
      }else{
        rc = SQLITE_IOERR_UNLOCK;
        pFile->lastErrno = errno;
        pInode->eFileLock = NO_LOCK;
        pFile->eFileLock = NO_LOCK;
      }
    }

    /* Decrement the count of locks against this same file.  When the
    ** count reaches zero, close any other file descriptors whose close
    ** was deferred because of outstanding locks.
    */
    pInode->nLock--;
    assert( pInode->nLock>=0 );
    if( pInode->nLock==0 ){
      closePendingFds(pFile);
    }
  }

end_unlock:
  unixLeaveMutex();
  if( rc==SQLITE_OK ) pFile->eFileLock = eFileLock;
  return rc;
}

/*

static int dotlockUnlock(sqlite3_file *id, int eFileLock) {
  unixFile *pFile = (unixFile*)id;
  char *zLockFile = (char *)pFile->lockingContext;
  int rc;

  assert( pFile );
  OSTRACE(("UNLOCK  %d %d was %d pid=%d (dotlock)\n", pFile->h, eFileLock,
           pFile->eFileLock, getpid()));
  assert( eFileLock<=SHARED_LOCK );
  
  /* no-op if possible */
  if( pFile->eFileLock==eFileLock ){
    return SQLITE_OK;
  }

static int semUnlock(sqlite3_file *id, int eFileLock) {
  unixFile *pFile = (unixFile*)id;
  sem_t *pSem = pFile->pInode->pSem;

  assert( pFile );
  assert( pSem );
  OSTRACE(("UNLOCK  %d %d was %d pid=%d (sem)\n", pFile->h, eFileLock,
           pFile->eFileLock, getpid()));
  assert( eFileLock<=SHARED_LOCK );
  
  /* no-op if possible */
  if( pFile->eFileLock==eFileLock ){
    return SQLITE_OK;
  }
  

#else
    newOffset = lseek(id->h, offset, SEEK_SET);
    SimulateIOError( newOffset-- );
    if( newOffset!=offset ){
      if( newOffset == -1 ){
        ((unixFile*)id)->lastErrno = errno;
      }else{
        ((unixFile*)id)->lastErrno = 0;
      }
      return -1;
    }
    got = osRead(id->h, pBuf, cnt);
#endif
    if( got==cnt ) break;
    if( got<0 ){

  do{
    newOffset = lseek(id->h, offset, SEEK_SET);
    SimulateIOError( newOffset-- );
    if( newOffset!=offset ){
      if( newOffset == -1 ){
        ((unixFile*)id)->lastErrno = errno;
      }else{
        ((unixFile*)id)->lastErrno = 0;
      }
      return -1;
    }
    got = osWrite(id->h, pBuf, cnt);
  }while( got<0 && errno==EINTR );
#endif
  TIMER_END;

** as POSIX read & write locks over fixed set of locations (via fsctl),
** on AFP and SMB only exclusive byte-range locks are available via fsctl
** with _IOWR('z', 23, struct ByteRangeLockPB2) to track the same 5 states.
** To simulate a F_RDLCK on the shared range, on AFP a randomly selected
** address in the shared range is taken for a SHARED lock, the entire
** shared range is taken for an EXCLUSIVE lock):
**
**      PENDING_BYTE        0x40000000
**      RESERVED_BYTE       0x40000001
**      SHARED_RANGE        0x40000002 -> 0x40000200
**
** This works well on the local file system, but shows a nearly 100x
** slowdown in read performance on AFP because the AFP client disables
** the read cache when byte-range locks are present.  Enabling the read
** cache exposes a cache coherency problem that is present on all OS X

#include <string.h>
#include <ctype.h>
#include <stdlib.h>
#include <assert.h>

#ifndef __WIN32__
#   if defined(_WIN32) || defined(WIN32)
#       define __WIN32__
#   endif
#endif

#ifdef __WIN32__
#ifdef __cplusplus
extern "C" {
#endif

            if( sp->subsym[j]->prec>=0 ){
              rp->precsym = sp->subsym[j];
              break;
            }
          }
        }else if( sp->prec>=0 ){
          rp->precsym = rp->rhs[i];
        }
      }
    }
  }
  return;
}

/* Find all nonterminals which will generate the empty string.

          progress += SetAdd(s1->firstset,s2->index);
          break;
        }else if( s2->type==MULTITERMINAL ){
          for(j=0; j<s2->nsubsym; j++){
            progress += SetAdd(s1->firstset,s2->subsym[j]->index);
          }
          break;
        }else if( s1==s2 ){
          if( s1->lambda==LEMON_FALSE ) break;
        }else{
          progress += SetUnion(s1->firstset,s2->firstset);
          if( s2->lambda==LEMON_FALSE ) break;
        }
      }
    }
  }while( progress );
  return;
}

/* Compute all LR(0) states for the grammar.  Links

      for(cfp=lemp->sorted[i]->cfp; cfp; cfp=cfp->next){
        if( cfp->status==COMPLETE ) continue;
        for(plp=cfp->fplp; plp; plp=plp->next){
          change = SetUnion(plp->cfp->fws,cfp->fws);
          if( change ){
            plp->cfp->status = INCOMPLETE;
            progress = 1;
          }
        }
        cfp->status = COMPLETE;
      }
    }
  }while( progress );
}

static int resolve_conflict(struct action *,struct action *);

      if( cfp->rp->nrhs==cfp->dot ){        /* Is dot at extreme right? */
        for(j=0; j<lemp->nterminal; j++){
          if( SetFind(cfp->fws,j) ){
            /* Add a reduce action to the state "stp" which will reduce by the
            ** rule "cfp->rp" if the lookahead symbol is "lemp->symbols[j]" */
            Action_add(&stp->ap,REDUCE,lemp->symbols[j],(char *)cfp->rp);
          }
        }
      }
    }
  }

  /* Add the accepting token */
  if( lemp->start ){
    sp = Symbol_find(lemp->start);

            break;
          }else if( xsp->type==MULTITERMINAL ){
            int k;
            for(k=0; k<xsp->nsubsym; k++){
              SetAdd(newcfp->fws, xsp->subsym[k]->index);
            }
            break;
          }else{
            SetUnion(newcfp->fws,xsp->firstset);
            if( xsp->lambda==LEMON_FALSE ) break;
          }
        }
        if( i==rp->nrhs ) Plink_add(&cfp->fplp,newcfp);
      }
    }
  }
  return;
}

        psp->state = WAITING_FOR_ARROW;
      }else if( x[0]=='{' ){
        if( psp->prevrule==0 ){
          ErrorMsg(psp->filename,psp->tokenlineno,
"There is no prior rule upon which to attach the code \
fragment which begins on this line.");
          psp->errorcnt++;
        }else if( psp->prevrule->code!=0 ){
          ErrorMsg(psp->filename,psp->tokenlineno,
"Code fragment beginning on this line is not the first \
to follow the previous rule.");
          psp->errorcnt++;
        }else{
          psp->prevrule->line = psp->tokenlineno;
          psp->prevrule->code = &x[1];
        }
      }else if( x[0]=='[' ){
        psp->state = PRECEDENCE_MARK_1;
      }else{
        ErrorMsg(psp->filename,psp->tokenlineno,
          "Token \"%s\" should be either \"%%\" or a nonterminal name.",
          x);
        psp->errorcnt++;

        rp = (struct rule *)calloc( sizeof(struct rule) + 
             sizeof(struct symbol*)*psp->nrhs + sizeof(char*)*psp->nrhs, 1);
        if( rp==0 ){
          ErrorMsg(psp->filename,psp->tokenlineno,
            "Can't allocate enough memory for this rule.");
          psp->errorcnt++;
          psp->prevrule = 0;
        }else{
          int i;
          rp->ruleline = psp->tokenlineno;
          rp->rhs = (struct symbol**)&rp[1];
          rp->rhsalias = (const char**)&(rp->rhs[psp->nrhs]);
          for(i=0; i<psp->nrhs; i++){
            rp->rhs[i] = psp->rhs[i];
            rp->rhsalias[i] = psp->alias[i];
          }
          rp->lhs = psp->lhs;
          rp->lhsalias = psp->lhsalias;
          rp->nrhs = psp->nrhs;
          rp->code = 0;
          rp->precsym = 0;
          rp->index = psp->gp->nrule++;
          rp->nextlhs = rp->lhs->rule;
          rp->lhs->rule = rp;
          rp->next = 0;
          if( psp->firstrule==0 ){
            psp->firstrule = psp->lastrule = rp;
          }else{
            psp->lastrule->next = rp;
            psp->lastrule = rp;
          }
          psp->prevrule = rp;
        }
        psp->state = WAITING_FOR_DECL_OR_RULE;
      }else if( isalpha(x[0]) ){
        if( psp->nrhs>=MAXRHS ){
          ErrorMsg(psp->filename,psp->tokenlineno,
            "Too many symbols on RHS of rule beginning at \"%s\".",
            x);
          psp->errorcnt++;
          psp->state = RESYNC_AFTER_RULE_ERROR;
        }else{
          psp->rhs[psp->nrhs] = Symbol_new(x);
          psp->alias[psp->nrhs] = 0;
          psp->nrhs++;
        }
      }else if( (x[0]=='|' || x[0]=='/') && psp->nrhs>0 ){
        struct symbol *msp = psp->rhs[psp->nrhs-1];
        if( msp->type!=MULTITERMINAL ){
          struct symbol *origsp = msp;
          msp = (struct symbol *) calloc(1,sizeof(*msp));
          memset(msp, 0, sizeof(*msp));
          msp->type = MULTITERMINAL;

        psp->declargslot = 0;
        psp->decllinenoslot = 0;
        psp->insertLineMacro = 1;
        psp->state = WAITING_FOR_DECL_ARG;
        if( strcmp(x,"name")==0 ){
          psp->declargslot = &(psp->gp->name);
          psp->insertLineMacro = 0;
        }else if( strcmp(x,"include")==0 ){
          psp->declargslot = &(psp->gp->include);
        }else if( strcmp(x,"code")==0 ){
          psp->declargslot = &(psp->gp->extracode);
        }else if( strcmp(x,"token_destructor")==0 ){
          psp->declargslot = &psp->gp->tokendest;
        }else if( strcmp(x,"default_destructor")==0 ){
          psp->declargslot = &psp->gp->vardest;
        }else if( strcmp(x,"token_prefix")==0 ){
          psp->declargslot = &psp->gp->tokenprefix;
          psp->insertLineMacro = 0;
        }else if( strcmp(x,"syntax_error")==0 ){
          psp->declargslot = &(psp->gp->error);
        }else if( strcmp(x,"parse_accept")==0 ){
          psp->declargslot = &(psp->gp->accept);
        }else if( strcmp(x,"parse_failure")==0 ){
          psp->declargslot = &(psp->gp->failure);
        }else if( strcmp(x,"stack_overflow")==0 ){
          psp->declargslot = &(psp->gp->overflow);
        }else if( strcmp(x,"extra_argument")==0 ){
          psp->declargslot = &(psp->gp->arg);
          psp->insertLineMacro = 0;
        }else if( strcmp(x,"token_type")==0 ){
          psp->declargslot = &(psp->gp->tokentype);
          psp->insertLineMacro = 0;

          psp->preccounter++;
          psp->declassoc = RIGHT;
          psp->state = WAITING_FOR_PRECEDENCE_SYMBOL;
        }else if( strcmp(x,"nonassoc")==0 ){
          psp->preccounter++;
          psp->declassoc = NONE;
          psp->state = WAITING_FOR_PRECEDENCE_SYMBOL;
        }else if( strcmp(x,"destructor")==0 ){
          psp->state = WAITING_FOR_DESTRUCTOR_SYMBOL;
        }else if( strcmp(x,"type")==0 ){
          psp->state = WAITING_FOR_DATATYPE_SYMBOL;
        }else if( strcmp(x,"fallback")==0 ){
          psp->fallback = 0;
          psp->state = WAITING_FOR_FALLBACK_ID;
        }else if( strcmp(x,"wildcard")==0 ){
          psp->state = WAITING_FOR_WILDCARD_ID;
        }else{
          ErrorMsg(psp->filename,psp->tokenlineno,
            "Unknown declaration keyword: \"%%%s\".",x);
          psp->errorcnt++;
          psp->state = RESYNC_AFTER_DECL_ERROR;
        }
      }else{
        ErrorMsg(psp->filename,psp->tokenlineno,
          "Illegal declaration keyword: \"%s\".",x);
        psp->errorcnt++;
        psp->state = RESYNC_AFTER_DECL_ERROR;
      }
      break;

      }else if( isupper(x[0]) ){
        struct symbol *sp;
        sp = Symbol_new(x);
        if( sp->prec>=0 ){
          ErrorMsg(psp->filename,psp->tokenlineno,
            "Symbol \"%s\" has already be given a precedence.",x);
          psp->errorcnt++;
        }else{
          sp->prec = psp->preccounter;
          sp->assoc = psp->declassoc;
        }
      }else{
        ErrorMsg(psp->filename,psp->tokenlineno,
          "Can't assign a precedence to \"%s\".",x);
        psp->errorcnt++;
      }
      break;
    case WAITING_FOR_DECL_ARG:

          int prevc;
          cp = &cp[2];
          prevc = 0;
          while( (c= *cp)!=0 && (c!='/' || prevc!='*') ){
            if( c=='\n' ) lineno++;
            prevc = c;
            cp++;
          }
        }else if( c=='/' && cp[1]=='/' ){  /* Skip C++ style comments too */
          cp = &cp[2];
          while( (c= *cp)!=0 && c!='\n' ) cp++;
          if( c ) lineno++;
        }else if( c=='\'' || c=='\"' ){    /* String a character literals */
          int startchar, prevc;
          startchar = c;
          prevc = 0;
          for(cp++; (c= *cp)!=0 && (c!=startchar || prevc=='\\'); cp++){
            if( c=='\n' ) lineno++;
            if( prevc=='\\' ) prevc = 0;
            else              prevc = c;
          }
        }
      }
      if( c==0 ){
        ErrorMsg(ps.filename,ps.tokenlineno,
"C code starting on this line is not terminated before the end of the file.");
        ps.errorcnt++;
        nextcp = cp;
      }else{