sys/src/9/bitsy/tar.c

   1 #include "u.h"
   2 #include "../port/lib.h"
   3 #include "mem.h"
   4 #include "dat.h"
   5 #include "fns.h"
   6 #include "io.h"
   7 #include "../port/error.h"
   8
   9 typedef union Hblock Hblock;
  10
  11 #define TBLOCK  512
  12 #define NAMSIZ  100
  13 union   Hblock
  14 {
  15         char    dummy[TBLOCK];
  16         struct  header
  17         {
  18                 char    name[NAMSIZ];
  19                 char    mode[8];
  20                 char    uid[8];
  21                 char    gid[8];
  22                 char    size[12];
  23                 char    mtime[12];
  24                 char    chksum[8];
  25                 char    linkflag;
  26                 char    linkname[NAMSIZ];
  27         } dbuf;
  28 };
  29
  30 static int getdir(Hblock *hb, Dir *sp);
  31 static int checksum(Hblock *hb);
  32
  33 uchar*
  34 tarlookup(uchar *addr, char *file, int *dlen)
  35 {
  36         Hblock *hp;
  37         Dir dir;
  38
  39         hp = (Hblock*)addr;
  40         while(getdir(hp, &dir) != 0) {
  41                 if(strcmp(file, hp->dbuf.name) == 0) {
  42                         *dlen = dir.length;
  43                         return (uchar*)(hp+1);
  44                 }
  45                 hp += (dir.length+TBLOCK-1)/TBLOCK + 1;
  46         }
  47         return 0;
  48 }
  49
  50 static int
  51 getdir(Hblock *hp, Dir *sp)
  52 {
  53         int chksum;
  54
  55         if (hp->dbuf.name[0] == '\0')
  56                 return 0;
  57         sp->length = strtol(hp->dbuf.size, 0, 8);
  58         sp->mtime = strtol(hp->dbuf.mtime, 0, 8);
  59         chksum = strtol(hp->dbuf.chksum, 0, 8);
  60         if (chksum != checksum(hp)) {
  61                 print("directory checksum error\n");
  62                 return 0;
  63         }
  64         return 1;
  65 }
  66
  67 static int
  68 checksum(Hblock *hp)
  69 {
  70         int i;
  71         char *cp;
  72
  73         i = 0;
  74         for (cp = hp->dummy; cp < &hp->dummy[TBLOCK]; cp++) {
  75                 if(cp < hp->dbuf.chksum || cp >= &hp->dbuf.chksum[sizeof(hp->dbuf.chksum)])
  76                         i += *cp & 0xff;
  77                 else
  78                         i += ' ' & 0xff;
  79         }
  80         return(i);
  81 }