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Annotation of 43BSD/contrib/jove/temp.h, revision 1.1

1.1     ! root        1: /*************************************************************************
        !             2:  * This program is copyright (C) 1985, 1986 by Jonathan Payne.  It is    *
        !             3:  * provided to you without charge for use only on a licensed Unix        *
        !             4:  * system.  You may copy JOVE provided that this notice is included with *
        !             5:  * the copy.  You may not sell copies of this program or versions        *
        !             6:  * modified for use on microcomputer systems, unless the copies are      *
        !             7:  * included with a Unix system distribution and the source is provided.  *
        !             8:  *************************************************************************/
        !             9: 
        !            10: /* This algorithm is just like the VI and ED ones.  There are several
        !            11:    differences though.  The first is that I don't just have THREE or TWO
        !            12:    incore blocks of the tmp file.  Instead there is a buffer cache of NBUF
        !            13:    buffers (64 on VM machines and the normal 3 on smaller ones).  Each block
        !            14:    is stored in LRU order and in a hash table by block #.  When a block is
        !            15:    requested it can quickly be looked up in the hash table.  If it's not
        !            16:    there the LRU block is used.  If it finds that the LRU block is dirty it
        !            17:    syncs the whole tmp file, i.e., does all the pending writes.  This works
        !            18:    really well on floppy disk systems, like the IBM PC, if the blocks are
        !            19:    sorted first.
        !            20: 
        !            21:    The constants below are sorta hard to grok because they are in disguise,
        !            22:    but the basic idea is this:  The tmp file is allocated in chunks of
        !            23:    BNDRY/2 (or is it BNDRY? I can't remember) characters.  New lines are
        !            24:    added to the end of the tmp file.  The file is not garbage collected
        !            25:    because that would be too painful.  As a result, commands like Yank and
        !            26:    Kill are really easy.  Basically all we do is make copies of the disk
        !            27:    addresses of the lines.  It's fast--very.  So, putline(buf) writes BUF to
        !            28:    the disk and returns a new disk address.  Getline(addr, buf) is the
        !            29:    opposite of putline().  Lines do NOT cross block bounderies (as in VI and
        !            30:    ED) so that accessing the contents of lines can be much faster.  Pointers
        !            31:    to offsets into disk buffers are returned instead of copying the contents
        !            32:    into local arrays and then using them.  This cut down on the amount of
        !            33:    copying a great deal, at the expense of less efficiency.  But it's not a
        !            34:    big deal, really.  Incrementing the logical disk pointer by INCRMT is
        !            35:    like incrementing the physical disk pointer by a block.  The lower bit is
        !            36:    left alone, so JOVE uses that to mark lines as needing redisplay done to
        !            37:    them. */
        !            38: 
        !            39: #ifndef VMUNIX
        !            40: 
        !            41: #if BUFSIZ == 512
        !            42: #      define  BLKMSK  01777
        !            43: #      define  BNDRY   16
        !            44: #      define  INCRMT  0100
        !            45: #      define  LBTMSK  0760
        !            46: #      define  NMBLKS  1018
        !            47: #      define  OFFBTS  6
        !            48: #      define  OFFMSK  077
        !            49: #      define  SHFT    3
        !            50: #else
        !            51: #      define  BLKMSK  0777
        !            52: #      define  BNDRY   16
        !            53: #      define  INCRMT  0200
        !            54: #      define  LBTMSK  01760
        !            55: #      define  NMBLKS  506
        !            56: #      define  OFFBTS  7
        !            57: #      define  OFFMSK  0177
        !            58: #      define  SHFT    3
        !            59: #endif
        !            60: 
        !            61: #else
        !            62: 
        !            63: #define        BLKMSK  077777
        !            64: #define        BNDRY   2
        !            65: #define        INCRMT  02000
        !            66: #define        LBTMSK  01776
        !            67: #define        NMBLKS  077770
        !            68: #define        OFFBTS  10
        !            69: #define        OFFMSK  01777
        !            70: #define        SHFT    0
        !            71: 
        !            72: #endif VMUNIX
        !            73: 
        !            74: extern int     nleft,          /* Number of good characters left in current block */
        !            75:                tmpfd;
        !            76: extern disk_line
        !            77:                tline;  /* Pointer to end of tmp file */
        !            78: 
        !            79: extern char    *tfname;

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