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Annotation of 43BSD/contrib/jove/temp.h, revision 1.1.1.1

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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