sys/src/cmd/hgfs/patch.c

   1 #include <u.h>
   2 #include <libc.h>
   3 #include <thread.h>
   4 #include "dat.h"
   5 #include "fns.h"
   6
   7 int
   8 fcopy(int dfd, int sfd, vlong len)
   9 {
  10         uchar buf[BUFSZ];
  11         int n;
  12
  13         while(len > 0){
  14                 if((n = BUFSZ) > len)
  15                         n = len;
  16                 if((n = read(sfd, buf, n)) < 0)
  17                         return -1;
  18                 if(write(dfd, buf, n) != n)
  19                         return -1;
  20                 len -= n;
  21         }
  22         return 0;
  23 }
  24
  25 static uchar patchmark[12] = {
  26         0xff, 0xff, 0xff, 0xff,
  27         0xff, 0xff, 0xff, 0xff,
  28         0xff, 0xff, 0xff, 0xff,
  29 };
  30
  31 int
  32 fpatchmark(int pfd, char *)
  33 {
  34         if(write(pfd, patchmark, 12) != 12)
  35                 return -1;
  36         return 0;
  37 }
  38
  39 typedef struct Frag Frag;
  40 struct Frag
  41 {
  42         Frag    *next;
  43         int     fd;
  44         vlong   len;
  45         vlong   off;
  46 };
  47
  48 int
  49 fpatch(int ofd, int bfd, int pfd)
  50 {
  51         vlong off, fstart, fend, start, end, len;
  52         int err, front, back;
  53         Frag *h, *f, *p;
  54         uchar buf[12];
  55
  56         h = nil;
  57         err = -1;
  58
  59         if(bfd >= 0){
  60                 h = malloc(sizeof(Frag));
  61                 h->next = nil;
  62                 h->off = 0;
  63                 h->fd = bfd;
  64                 h->len = seek(h->fd, 0, 2);
  65                 if(h->len < 0)
  66                         goto errout;
  67         }
  68
  69         off = 0;
  70         while(pfd >= 0){
  71                 if(readn(pfd, buf, 12) != 12)
  72                         break;
  73
  74                 if(memcmp(buf, patchmark, 12) == 0){
  75                         off = 0;
  76                         continue;
  77                 }
  78
  79                 start = buf[0]<<24 | buf[1]<<16 | buf[2]<<8 | buf[3];
  80                 end = buf[4]<<24 | buf[5]<<16 | buf[6]<<8 | buf[7];
  81                 len = buf[8]<<24 | buf[9]<<16 | buf[10]<<8 | buf[11];
  82
  83                 if(start > end){
  84                         werrstr("bad patch: start > end");
  85                         goto errout;
  86                 }
  87
  88                 start += off;
  89                 end += off;
  90                 off += start + len - end;
  91
  92                 fstart = 0;
  93                 for(f = h; f; f = f->next, fstart = fend){
  94                         fend = fstart + f->len;
  95                         if(fend <= start)
  96                                 continue;
  97                         if(fstart >= end)
  98                                 break;
  99
 100                         front = start > fstart;
 101                         back = end < fend;
 102                         if(front && back){
 103                                 p = malloc(sizeof(Frag));
 104                                 *p = *f;
 105                                 f->next = p;
 106                                 f->len = start - fstart;
 107                                 p->off += end - fstart;
 108                                 p->len -= end - fstart;
 109                                 break;
 110                         } else if(back){
 111                                 f->off += end - fstart;
 112                                 f->len -= end - fstart;
 113                                 break;
 114                         } else if(front){
 115                                 f->len = start - fstart;
 116                         } else {
 117                                 f->len = 0;
 118                         }
 119                 }
 120
 121                 fstart = 0;
 122                 for(p = nil, f = h; f && fstart < start; p = f, f = f->next)
 123                         fstart += f->len;
 124
 125                 f = malloc(sizeof(Frag));
 126                 f->fd = pfd;
 127                 f->len = len;
 128                 f->off = seek(f->fd, 0, 1);
 129
 130                 if(p){
 131                         f->next = p->next;
 132                         p->next = f;
 133                 } else {
 134                         f->next = h;
 135                         h = f;
 136                 }
 137
 138                 if(f->off < 0)
 139                         goto errout;
 140                 if(seek(pfd, f->len, 1) < 0)
 141                         goto errout;
 142         }
 143
 144         for(f = h; f; f = f->next){
 145                 if(seek(f->fd, f->off, 0) < 0)
 146                         goto errout;
 147                 if(fcopy(ofd, f->fd, f->len) < 0)
 148                         goto errout;
 149         }
 150         err = 0;
 151
 152 errout:
 153         while(f = h){
 154                 h = f->next;
 155                 free(f);
 156         }
 157
 158         return err;
 159 }