shmem.c

CFL是Unix下的通用抽象库,以简化Unix下的系统软件开发,CFL库中包含几个分组的函数和宏

/* ----------------------------------------------------------------------------
   CFL - A C Foundation Library
   Copyright (C) 1994-2003  Mark A Lindner

   This file is part of CFL.
   
   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public
   License as published by the Free Software Foundation; either
   version 2 of the License, or (at your option) any later version.
   
   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.
   
   You should have received a copy of the GNU Library General Public
   License along with this library; if not, write to the Free
   Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
   ----------------------------------------------------------------------------
   $Log: shmem.c,v $
   Revision 1.1  2003/03/03 08:20:08  markl
   Initial checkin (clean compile on Solaris & OS X)

   ----------------------------------------------------------------------------
*/

/* Feature test switches */

#include "config.h"

#ifdef linux
#define _POSIX_C_SOURCE 199506L
#define _XOPEN_SOURCE 500
#endif

/* System headers */

#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
#ifdef linux
#include <pthread.h> // Linux references a pthread struct in semaphore.h 
#endif

/* Local headers */

#include "cfl/defs.h"
#include "cfl/ipc.h"
#include "cfl/system.h"
#include "cfl/util.h"

/* Functions */

static size_t __C_shmem_round_size(size_t size)
  {
#if defined _SC_PAGESIZE
  long pagesize = sysconf(_SC_PAGESIZE);
#elif defined HAVE_GETPAGESIZE
  long pagesize = getpagesize();
#else
  #error "No means to determine system page size."
#endif

  return((size_t)(size + pagesize - (size % pagesize)));
  }

/*
 */

c_shmem_t *C_shmem_create(const char *name, size_t size, mode_t mode)
  {
  c_shmem_t *m;
  int fd;
  c_bool_t init = TRUE;

  if((fd = shm_open(name, (O_CREAT | O_RDWR | O_EXCL), mode)) < 0)
    {
    if(errno == EEXIST)
      {
      init = FALSE;

      if((fd = shm_open(name, (O_CREAT | O_RDWR), mode)) < 0)
        return(NULL);
      }
    else
      return(NULL);
    }
  
  m = C_new(c_shmem_t);
  m->name = C_string_dup(name);
  m->fd = fd;
  m->size = __C_shmem_round_size(size);

  if(init)
    ftruncate(m->fd, (off_t)m->size);
  
  m->base = mmap(NULL, m->size, (PROT_READ | PROT_WRITE), MAP_SHARED, m->fd,
                 (off_t)0);


  if(init)
    memset(m->base, 0, m->size);

  return(m);
  }

/*
 */

void C_shmem_destroy(c_shmem_t *mem)
  {
  if(!mem)
    return;

  munmap(mem->base, mem->size);
  shm_unlink(mem->name);
  C_free(mem->name);
  C_free(mem);
  }

/*
 */

c_bool_t C_shmem_resize(c_shmem_t *mem, size_t size)
  {
  size_t oldsize, newsize;
  
  if(!mem || (size <= 0))
    return(FALSE);

  oldsize = mem->size;
  newsize = __C_shmem_round_size(size);

  if(ftruncate(mem->fd, newsize))
    return(FALSE);

  mem->size = newsize;
  if(newsize > oldsize)
    memset(mem->base + oldsize, 0, (newsize - oldsize));

  return(TRUE);
  }

/* end of source file */