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 off, vlong len)
   9 {
  10         uchar buf[BUFSZ];
  11         int n;
  12
  13         while(len != 0){
  14                 n = BUFSZ;
  15                 if(len > 0 && n > len)
  16                         n = len;
  17                 if((n = pread(sfd, buf, n, off)) < 0)
  18                         return -1;
  19                 if(n == 0)
  20                         return len > 0 ? -1 : 0;
  21                 if(write(dfd, buf, n) != n)
  22                         return -1;
  23                 if(off >= 0)
  24                         off += n;
  25                 if(len > 0)
  26                         len -= n;
  27         }
  28         return 0;
  29 }
  30
  31 static uchar patchmark[12] = {
  32         0xff, 0xff, 0xff, 0xff,
  33         0xff, 0xff, 0xff, 0xff,
  34         0xff, 0xff, 0xff, 0xff,
  35 };
  36
  37 int
  38 fpatchmark(int pfd, char *)
  39 {
  40         if(write(pfd, patchmark, 12) != 12)
  41                 return -1;
  42         return 0;
  43 }
  44
  45 typedef struct Frag Frag;
  46 struct Frag
  47 {
  48         Frag    *next;
  49         int     fd;
  50         vlong   len;
  51         vlong   off;
  52 };
  53
  54 int
  55 fpatch(int ofd, int bfd, int pfd)
  56 {
  57         vlong off, fstart, fend, start, end, len;
  58         int err, front, back;
  59         Frag *h, *f, *p;
  60         uchar buf[12];
  61
  62         h = nil;
  63         err = -1;
  64
  65         if(bfd >= 0){
  66                 h = malloc(sizeof(Frag));
  67                 if(h == nil)
  68                         goto errout;
  69                 h->next = nil;
  70                 h->off = 0;
  71                 h->fd = bfd;
  72                 h->len = seek(h->fd, 0, 2);
  73                 if(h->len < 0)
  74                         goto errout;
  75         }
  76
  77         off = 0;
  78         while(pfd >= 0){
  79                 if(readn(pfd, buf, 12) != 12)
  80                         break;
  81
  82                 if(memcmp(buf, patchmark, 12) == 0){
  83                         off = 0;
  84                         continue;
  85                 }
  86
  87                 start = buf[0]<<24 | buf[1]<<16 | buf[2]<<8 | buf[3];
  88                 end = buf[4]<<24 | buf[5]<<16 | buf[6]<<8 | buf[7];
  89                 len = buf[8]<<24 | buf[9]<<16 | buf[10]<<8 | buf[11];
  90
  91                 if(start > end){
  92                         werrstr("bad patch: start > end");
  93                         goto errout;
  94                 }
  95
  96                 start += off;
  97                 end += off;
  98                 off += start + len - end;
  99
 100                 fstart = 0;
 101                 for(f = h; f; f = f->next, fstart = fend){
 102                         fend = fstart + f->len;
 103                         if(fend <= start)
 104                                 continue;
 105                         if(fstart >= end)
 106                                 break;
 107
 108                         front = start > fstart;
 109                         back = end < fend;
 110                         if(front && back){
 111                                 p = malloc(sizeof(Frag));
 112                                 if(p == nil)
 113                                         goto errout;
 114                                 *p = *f;
 115                                 f->next = p;
 116                                 f->len = start - fstart;
 117                                 p->off += end - fstart;
 118                                 p->len -= end - fstart;
 119                                 break;
 120                         } else if(back){
 121                                 f->off += end - fstart;
 122                                 f->len -= end - fstart;
 123                                 break;
 124                         } else if(front){
 125                                 f->len = start - fstart;
 126                         } else {
 127                                 f->len = 0;
 128                         }
 129                 }
 130
 131                 fstart = 0;
 132                 for(p = nil, f = h; f && fstart < start; p = f, f = f->next)
 133                         fstart += f->len;
 134
 135                 f = malloc(sizeof(Frag));
 136                 if(f == nil)
 137                         goto errout;
 138                 f->fd = pfd;
 139                 f->len = len;
 140                 f->off = seek(f->fd, 0, 1);
 141
 142                 if(p){
 143                         f->next = p->next;
 144                         p->next = f;
 145                 } else {
 146                         f->next = h;
 147                         h = f;
 148                 }
 149
 150                 if(f->off < 0)
 151                         goto errout;
 152                 if(seek(pfd, f->len, 1) < 0)
 153                         goto errout;
 154         }
 155
 156         for(f = h; f; f = f->next)
 157                 if(fcopy(ofd, f->fd, f->off, f->len) < 0)
 158                         goto errout;
 159         err = 0;
 160
 161 errout:
 162         while(f = h){
 163                 h = f->next;
 164                 free(f);
 165         }
 166
 167         return err;
 168 }