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      1 /*
      2  * Copyright (C) 2008 The Android Open Source Project
      3  * All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions
      7  * are met:
      8  *  * Redistributions of source code must retain the above copyright
      9  *    notice, this list of conditions and the following disclaimer.
     10  *  * Redistributions in binary form must reproduce the above copyright
     11  *    notice, this list of conditions and the following disclaimer in
     12  *    the documentation and/or other materials provided with the
     13  *    distribution.
     14  *
     15  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     16  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     17  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
     18  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
     19  * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
     20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
     21  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
     22  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
     23  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
     24  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
     25  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     26  * SUCH DAMAGE.
     27  */
     28 
     29 /* implement flockfile(), ftrylockfile() and funlockfile()
     30  *
     31  * we can't use the OpenBSD implementation which uses kernel-specific
     32  * APIs not available on Linux.
     33  *
     34  * Instead, we use a pthread_mutex_t within the FILE* internal state.
     35  * See fileext.h for details.
     36  *
     37  * the behaviour, if fclose() is called while the corresponding
     38  * file is locked is totally undefined.
     39  */
     40 #include <stdio.h>
     41 #include <string.h>
     42 #include <errno.h>
     43 #include "fileext.h"
     44 
     45 
     46 void
     47 flockfile(FILE * fp)
     48 {
     49     if (fp != NULL) {
     50         _FLOCK_LOCK(fp);
     51     }
     52 }
     53 
     54 
     55 int
     56 ftrylockfile(FILE *fp)
     57 {
     58     /* The specification for ftrylockfile() says it returns 0 on success,
     59      * or non-zero on error. So return an errno code directly on error.
     60      */
     61     int  ret = EINVAL;
     62 
     63     if (fp != NULL) {
     64         ret = _FLOCK_TRYLOCK(fp);
     65     }
     66     return ret;
     67 }
     68 
     69 void
     70 funlockfile(FILE * fp)
     71 {
     72     if (fp != NULL) {
     73         _FLOCK_UNLOCK(fp);
     74     }
     75 }
     76