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;

Defined macros

BLKMSK defined in line 63; used 2 times
BNDRY defined in line 64; used 1 times
INCRMT defined in line 65; used 3 times
LBTMSK defined in line 66; used 2 times
NMBLKS defined in line 67; used 1 times
OFFBTS defined in line 68; used 2 times
OFFMSK defined in line 69; used 3 times
SHFT defined in line 70; used 3 times

Usage of this include

Last modified: 1986-03-28
Generated: 2016-12-26
Generated by src2html V0.67
page hit count: 788
Valid CSS Valid XHTML 1.0 Strict