FreeBSD/Linux Kernel Cross Reference
sys/sys/pipe.h

     /*
      * Copyright (c) 1996 John S. Dyson
      * All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
      * 1. Redistributions of source code must retain the above copyright
      *    notice immediately at the beginning of the file, without modification,
     *    this list of conditions, and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. Absolutely no warranty of function or purpose is made by the author
     *    John S. Dyson.
     * 4. This work was done expressly for inclusion into FreeBSD.  Other use
     *    is allowed if this notation is included.
     * 5. Modifications may be freely made to this file if the above conditions
     *    are met.
     *
     * $FreeBSD$
     */
    
    #ifndef _SYS_PIPE_H_
    #define _SYS_PIPE_H_
    
    #ifndef KERNEL
    #include <sys/time.h>                   /* for struct timeval */
    #include <sys/select.h>                 /* for struct selinfo */
    #include <vm/vm.h>                      /* for vm_page_t */
    #include <machine/param.h>              /* for PAGE_SIZE */
    #endif
    
    /*
     * Pipe buffer size, keep moderate in value, pipes take kva space.
     */
    #ifndef PIPE_SIZE
    #define PIPE_SIZE       16384
    #endif
    
    #ifndef BIG_PIPE_SIZE
    #define BIG_PIPE_SIZE   (64*1024)
    #endif
    
    /*
     * PIPE_MINDIRECT MUST be smaller than PIPE_SIZE and MUST be bigger
     * than PIPE_BUF.
     */
    #ifndef PIPE_MINDIRECT
    #define PIPE_MINDIRECT  8192
    #endif
    
    #define PIPENPAGES      (BIG_PIPE_SIZE / PAGE_SIZE + 1)
    
    /*
     * Pipe buffer information.
     * Separate in, out, cnt are used to simplify calculations.
     * Buffered write is active when the buffer.cnt field is set.
     */
    struct pipebuf {
            u_int   cnt;            /* number of chars currently in buffer */
            u_int   in;             /* in pointer */
            u_int   out;            /* out pointer */
            u_int   size;           /* size of buffer */
            caddr_t buffer;         /* kva of buffer */
            struct  vm_object *object;      /* VM object containing buffer */
    };
    
    /*
     * Information to support direct transfers between processes for pipes.
     */
    struct pipemapping {
            vm_offset_t     kva;            /* kernel virtual address */
            vm_size_t       cnt;            /* number of chars in buffer */
            vm_size_t       pos;            /* current position of transfer */
            int             npages;         /* number of pages */
            vm_page_t       ms[PIPENPAGES]; /* pages in source process */
    };
    
    /*
     * Bits in pipe_state.
     */
    #define PIPE_ASYNC      0x004   /* Async? I/O. */
    #define PIPE_WANTR      0x008   /* Reader wants some characters. */
    #define PIPE_WANTW      0x010   /* Writer wants space to put characters. */
    #define PIPE_WANT       0x020   /* Pipe is wanted to be run-down. */
    #define PIPE_SEL        0x040   /* Pipe has a select active. */
    #define PIPE_EOF        0x080   /* Pipe is in EOF condition. */
    #define PIPE_LOCK       0x100   /* Process has exclusive access to pointers/data. */
    #define PIPE_LWANT      0x200   /* Process wants exclusive access to pointers/data. */
    #define PIPE_DIRECTW    0x400   /* Pipe direct write active. */
    #define PIPE_DIRECTOK   0x800   /* Direct mode ok. */
    
    /*
     * Per-pipe data structure.
     * Two of these are linked together to produce bi-directional pipes.
     */
    struct pipe {
            struct  pipebuf pipe_buffer;    /* data storage */
           struct  pipemapping pipe_map;   /* pipe mapping for direct I/O */
           struct  selinfo pipe_sel;       /* for compat with select */
           struct  timespec pipe_atime;    /* time of last access */
           struct  timespec pipe_mtime;    /* time of last modify */
           struct  timespec pipe_ctime;    /* time of status change */
           struct  sigio *pipe_sigio;      /* information for async I/O */
           struct  pipe *pipe_peer;        /* link with other direction */
           u_int   pipe_state;             /* pipe status info */
           int     pipe_busy;              /* busy flag, mostly to handle rundown sanely */
   };
   
   #ifdef KERNEL
   int     pipe_stat __P((struct pipe *pipe, struct stat *ub));
   #endif
   
   #endif /* !_SYS_PIPE_H_ */

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