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Annotation of Net2/sys/filedesc.h, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1990 The Regents of the University of California.
        !             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:  * 1. Redistributions of source code must retain the above copyright
        !             9:  *    notice, this list of conditions and the following disclaimer.
        !            10:  * 2. Redistributions in binary form must reproduce the above copyright
        !            11:  *    notice, this list of conditions and the following disclaimer in the
        !            12:  *    documentation and/or other materials provided with the distribution.
        !            13:  * 3. All advertising materials mentioning features or use of this software
        !            14:  *    must display the following acknowledgement:
        !            15:  *     This product includes software developed by the University of
        !            16:  *     California, Berkeley and its contributors.
        !            17:  * 4. Neither the name of the University nor the names of its contributors
        !            18:  *    may be used to endorse or promote products derived from this software
        !            19:  *    without specific prior written permission.
        !            20:  *
        !            21:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
        !            22:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            23:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            24:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
        !            25:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            26:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            27:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            28:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            29:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            30:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            31:  * SUCH DAMAGE.
        !            32:  *
        !            33:  *     @(#)filedesc.h  7.4 (Berkeley) 5/4/91
        !            34:  */
        !            35: 
        !            36: /*
        !            37:  * This structure is used for the management of descriptors.  It may be
        !            38:  * shared by multiple processes.
        !            39:  *
        !            40:  * A process is initially started out with NDFILE descriptors stored within
        !            41:  * this structure, selected to be enough for typical applications based on
        !            42:  * the historical limit of 20 open files (and the usage of descriptors by
        !            43:  * shells).  If these descriptors are exhausted, a larger descriptor table
        !            44:  * may be allocated, up to a process' resource limit; the internal arrays
        !            45:  * are then unused.  The initial expansion is set to NDEXTENT; each time
        !            46:  * it runs out, it is doubled until the resource limit is reached. NDEXTENT
        !            47:  * should be selected to be the biggest multiple of OFILESIZE (see below)
        !            48:  * that will fit in a power-of-two sized piece of memory.
        !            49:  */
        !            50: #define NDFILE         20
        !            51: #define NDEXTENT       50              /* 250 bytes in 256-byte alloc. */ 
        !            52: 
        !            53: struct filedesc {
        !            54:        struct  file **fd_ofiles;       /* file structures for open files */
        !            55:        char    *fd_ofileflags;         /* per-process open file flags */
        !            56:        struct  vnode *fd_cdir;         /* current directory */
        !            57:        struct  vnode *fd_rdir;         /* root directory */
        !            58:        int     fd_nfiles;              /* number of open files allocated */
        !            59:        u_short fd_lastfile;            /* high-water mark of fd_ofiles */
        !            60:        u_short fd_freefile;            /* approx. next free file */
        !            61:        u_short fd_cmask;               /* mask for file creation */
        !            62:        u_short fd_refcnt;              /* reference count */
        !            63: };
        !            64: 
        !            65: /*
        !            66:  * Basic allocation of descriptors:
        !            67:  * one of the above, plus arrays for NDFILE descriptors.
        !            68:  */
        !            69: struct filedesc0 {
        !            70:        struct  filedesc fd_fd;
        !            71:        /*
        !            72:         * These arrays are used when the number of open files is
        !            73:         * <= NDFILE, and are then pointed to by the pointers above.
        !            74:         */
        !            75:        struct  file *fd_dfiles[NDFILE];
        !            76:        char    fd_dfileflags[NDFILE];
        !            77: };
        !            78: 
        !            79: /*
        !            80:  * Per-process open flags.
        !            81:  */
        !            82: #define        UF_EXCLOSE      0x01            /* auto-close on exec */
        !            83: #define        UF_MAPPED       0x02            /* mapped from device */
        !            84: 
        !            85: /*
        !            86:  * Storage required per open file descriptor.
        !            87:  */
        !            88: #define OFILESIZE (sizeof(struct file *) + sizeof(char))
        !            89: 
        !            90: #ifdef KERNEL
        !            91: /*
        !            92:  * Kernel global variables and routines.
        !            93:  */
        !            94: int    fdalloc __P((struct proc *p, int want, int *result));
        !            95: int    fdavail __P((struct proc *p, int n));
        !            96: int    falloc __P((struct proc *p, struct file **resultfp, int *resultfd));
        !            97: struct filedesc *fdcopy __P((struct proc *p));
        !            98: void   fdfree __P((struct proc *p));
        !            99: #endif

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