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

     /* $NetBSD: pipe.h,v 1.38 2021/01/25 19:21:11 dholland Exp $ */
     
     /*
      * 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: src/sys/sys/pipe.h,v 1.18 2002/02/27 07:35:59 alfred Exp $
     */
    
    #ifndef _SYS_PIPE_H_
    #define _SYS_PIPE_H_
    
    #include <sys/selinfo.h>                /* for struct selinfo */
    #include <sys/time.h>                   /* for struct timespec */
    
    #include <uvm/uvm_extern.h>
    
    /*
     * 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   (4*PIPE_SIZE)
    #endif
    
    /*
     * Maximum size of transfer for direct write transfer. If the amount
     * of data in buffer is larger, it would be transferred in chunks of this
     * size.
     */
    #ifndef PIPE_DIRECT_CHUNK
    #define PIPE_DIRECT_CHUNK       (1*1024*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
    
    /*
     * 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 {
            size_t  cnt;            /* number of chars currently in buffer */
            u_int   in;             /* in pointer */
            u_int   out;            /* out pointer */
            size_t  size;           /* size of buffer */
            void *  buffer;         /* kva of buffer */
    };
    
    /*
     * Bits in pipe_state.
     */
    #define PIPE_ASYNC      0x001   /* Async I/O */
    #define PIPE_EOF        0x010   /* Pipe is in EOF condition */
    #define PIPE_SIGNALR    0x020   /* Do selwakeup() on read(2) */
    #define PIPE_LOCKFL     0x100   /* Process has exclusive access to
                                       pointers/data. */
    /*      unused          0x200   */
    #define PIPE_RESTART    0x400   /* Return ERESTART to blocked syscalls */
    
    /*
     * Per-pipe data structure.
     * Two of these are linked together to produce bi-directional pipes.
     */
    struct pipe {
            kmutex_t *pipe_lock;            /* pipe mutex */
            kcondvar_t pipe_rcv;            /* cv for readers */
            kcondvar_t pipe_wcv;            /* cv for writers */
            kcondvar_t pipe_draincv;        /* cv for close */
            kcondvar_t pipe_lkcv;           /* locking */
            struct  pipebuf pipe_buffer;    /* data storage */
            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_btime;    /* time of creation */
           pid_t   pipe_pgid;              /* process group for sigio */
           u_int   pipe_waiters;           /* number of waiters pending */
           struct  pipe *pipe_peer;        /* link with other direction */
           u_int   pipe_state;             /* pipe status info */
           int     pipe_busy;              /* busy flag, to handle rundown */
           vaddr_t pipe_kmem;              /* preallocated PIPE_SIZE buffer */
   };
   
   /*
    * KERN_PIPE subtypes
    */
   #define KERN_PIPE_MAXKVASZ              1       /* maximum kva size (obsolete) */
   #define KERN_PIPE_LIMITKVA              2       /* limit kva for laons (obsolete) */
   #define KERN_PIPE_MAXBIGPIPES           3       /* maximum # of "big" pipes */
   #define KERN_PIPE_NBIGPIPES             4       /* current number of "big" p. */
   #define KERN_PIPE_KVASIZE               5       /* current pipe kva size */
   
   #ifdef _KERNEL
   int     sysctl_dopipe(int *, u_int, void *, size_t *, void *, size_t);
   void    pipe_init(void);
   #endif /* _KERNEL */
   
   #endif /* !_SYS_PIPE_H_ */

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