sys/src/libventi/zero.c

   1 #include <u.h>
   2 #include <libc.h>
   3 #include <venti.h>
   4
   5 void
   6 vtzeroextend(int type, uchar *buf, uint n, uint nn)
   7 {
   8         uchar *p, *ep;
   9
  10         switch(type&7) {
  11         case 0:
  12                 memset(buf+n, 0, nn-n);
  13                 break;
  14         default:
  15                 p = buf + (n/VtScoreSize)*VtScoreSize;
  16                 ep = buf + (nn/VtScoreSize)*VtScoreSize;
  17                 while(p < ep) {
  18                         memmove(p, vtzeroscore, VtScoreSize);
  19                         p += VtScoreSize;
  20                 }
  21                 memset(p, 0, buf+nn-p);
  22                 break;
  23         }
  24 }
  25
  26 uint
  27 vtzerotruncate(int type, uchar *buf, uint n)
  28 {
  29         uchar *p;
  30
  31         if(type == VtRootType){
  32                 if(n < VtRootSize)
  33                         return n;
  34                 return VtRootSize;
  35         }
  36
  37         switch(type&7){
  38         case 0:
  39                 for(p = buf + n; p > buf; p--) {
  40                         if(p[-1] != 0)
  41                                 break;
  42                 }
  43                 return p - buf;
  44         default:
  45                 /* ignore slop at end of block */
  46                 p = buf + (n/VtScoreSize)*VtScoreSize;
  47
  48                 while(p > buf) {
  49                         if(memcmp(p - VtScoreSize, vtzeroscore, VtScoreSize) != 0)
  50                                 break;
  51                         p -= VtScoreSize;
  52                 }
  53                 return p - buf;
  54         }
  55 }