lib/bucket.c

   1 /*
   2  *      Sherlock Library -- Object Buckets
   3  *
   4  *      (c) 2001 Martin Mares <mj@ucw.cz>
   5  *
   6  *      Warning: Touches internals of the fb-file module!
   7  */
   8
   9 #include "lib/lib.h"
  10 #include "lib/bucket.h"
  11 #include "lib/fastbuf.h"
  12
  13 #include <string.h>
  14 #include <fcntl.h>
  15 #include <unistd.h>
  16 #include <sys/file.h>
  17
  18 static int obuck_fd;
  19 static struct fastbuf *obuck_fb;
  20 static struct obuck_header obuck_hdr;
  21 static sh_off_t start_of_this, start_of_next;
  22 static char *obuck_name = "db/objects";         /* FIXME */
  23
  24 void
  25 obuck_init(int writeable)
  26 {
  27   obuck_fb = bopen(obuck_name, (writeable ? O_RDWR | O_CREAT : O_RDONLY), 65536);
  28   obuck_fd = obuck_fb->fd;
  29 }
  30
  31 void
  32 obuck_cleanup(void)
  33 {
  34   bclose(obuck_fb);
  35 }
  36
  37 static void
  38 obuck_broken(char *msg)
  39 {
  40   die("Object pool corrupted: %s", msg);        /* FIXME */
  41 }
  42
  43 static inline void
  44 obuck_lock_read(void)
  45 {
  46   flock(obuck_fd, LOCK_SH);
  47 }
  48
  49 static inline void
  50 obuck_lock_write(void)
  51 {
  52   flock(obuck_fd, LOCK_EX);
  53 }
  54
  55 static inline void
  56 obuck_unlock(void)
  57 {
  58   flock(obuck_fd, LOCK_UN);
  59 }
  60
  61 static void
  62 obuck_fetch_header(oid_t oid)
  63 {
  64   start_of_this = ((sh_off_t) oid) << OBUCK_SHIFT;
  65   bsetpos(obuck_fb, start_of_this);
  66   bread(obuck_fb, &obuck_hdr, sizeof(obuck_hdr));
  67   if (obuck_hdr.magic != OBUCK_MAGIC)
  68     obuck_broken("Missing magic number");
  69   if (obuck_hdr.oid == OBUCK_OID_DELETED)
  70     obuck_broken("Access to deleted bucket");
  71   if (obuck_hdr.oid != oid)
  72     obuck_broken("Invalid backlink");
  73 }
  74
  75 struct fastbuf *
  76 obuck_fetch(struct obuck_header *hdrp)
  77 {
  78   obuck_lock_read();
  79   obuck_fetch_header(hdrp->oid);
  80   memcpy(hdrp, &obuck_hdr, sizeof(obuck_hdr));
  81   return obuck_fb;
  82 }
  83
  84 void
  85 obuck_fetch_abort(struct fastbuf *b UNUSED)
  86 {
  87   obuck_unlock();
  88 }
  89
  90 void
  91 obuck_fetch_end(struct fastbuf *b UNUSED)
  92 {
  93   if (bgetl(b) != OBUCK_TRAILER)
  94     obuck_broken("Corrupted trailer");
  95   obuck_unlock();
  96 }
  97
  98 struct fastbuf *
  99 obuck_write(void)
 100 {
 101   obuck_lock_write();
 102   bseek(obuck_fb, 0, SEEK_END);
 103   start_of_this = btell(obuck_fb);
 104   if (start_of_this & (OBUCK_ALIGN - 1))
 105     obuck_broken("Misaligned file");
 106   obuck_hdr.magic = 0;
 107   obuck_hdr.oid = start_of_this >> OBUCK_SHIFT;
 108   obuck_hdr.length = obuck_hdr.orig_length = 0;
 109   bwrite(obuck_fb, &obuck_hdr, sizeof(obuck_hdr));
 110   return obuck_fb;
 111 }
 112
 113 void
 114 obuck_write_end(struct fastbuf *b UNUSED, struct obuck_header *hdrp)
 115 {
 116   int pad;
 117   obuck_hdr.magic = OBUCK_MAGIC;
 118   obuck_hdr.length = obuck_hdr.orig_length = btell(obuck_fb) - start_of_this - sizeof(obuck_hdr);
 119   bputl(obuck_fb, OBUCK_TRAILER);
 120   pad = (OBUCK_ALIGN - sizeof(obuck_hdr) - obuck_hdr.length - 4) & (OBUCK_ALIGN - 1);
 121   while (pad--)
 122     bputc(obuck_fb, 0);
 123   bflush(obuck_fb);
 124   bsetpos(obuck_fb, start_of_this);
 125   /* FIXME: Can be replaced with single pwrite */
 126   bwrite(obuck_fb, &obuck_hdr, sizeof(obuck_hdr));
 127   bflush(obuck_fb);
 128   obuck_unlock();
 129   memcpy(hdrp, &obuck_hdr, sizeof(obuck_hdr));
 130 }
 131
 132 void
 133 obuck_delete(oid_t oid)
 134 {
 135   obuck_lock_write();
 136   obuck_fetch_header(oid);
 137   obuck_hdr.oid = OBUCK_OID_DELETED;
 138   bflush(obuck_fb);
 139   bsetpos(obuck_fb, start_of_this);
 140   bwrite(obuck_fb, &obuck_hdr, sizeof(obuck_hdr));
 141   bflush(obuck_fb);
 142   obuck_unlock();
 143 }
 144
 145 struct fastbuf *
 146 obuck_walk_init(void)
 147 {
 148   start_of_this = start_of_next = 0;
 149   obuck_lock_read();
 150   return obuck_fb;
 151 }
 152
 153 struct fastbuf *
 154 obuck_walk_next(struct fastbuf *b, struct obuck_header *hdrp)
 155 {
 156   int c;
 157
 158 restart:
 159   start_of_this = start_of_next;
 160   bsetpos(b, start_of_this);
 161   c = bgetc(b);
 162   if (c < 0)
 163     return NULL;
 164   bungetc(b, c);
 165   bread(b, &obuck_hdr, sizeof(obuck_hdr));
 166   if (obuck_hdr.magic != OBUCK_MAGIC)
 167     obuck_broken("Missing magic number");
 168   start_of_next = (start_of_this + sizeof(obuck_hdr) + obuck_hdr.orig_length +
 169         4 + OBUCK_ALIGN - 1) & ~((sh_off_t)(OBUCK_ALIGN - 1));
 170   if (obuck_hdr.oid == OBUCK_OID_DELETED)
 171     goto restart;
 172   memcpy(hdrp, &obuck_hdr, sizeof(obuck_hdr));
 173   return b;
 174 }
 175
 176 void
 177 obuck_walk_end(struct fastbuf *b UNUSED)
 178 {
 179   obuck_unlock();
 180 }
 181
 182 #ifdef TEST
 183 int main(void)
 184 {
 185   int i, j;
 186   struct obuck_header h;
 187   struct fastbuf *b;
 188   obuck_init(1);
 189   for(j=0; j<100; j++)
 190     {
 191       b = obuck_write();
 192       for(i=0; i<100*j; i++)
 193         bputc(b, i);
 194       obuck_write_end(b, &h);
 195       printf("%d\t%08x\t%d\n", j, h.oid, h.orig_length);
 196     }
 197   obuck_delete(0);
 198   b = obuck_walk_init();
 199   while (b = obuck_walk_next(b, &h))
 200     {
 201       printf("<<< %08x\t%d\n", h.oid, h.orig_length);
 202     }
 203   obuck_walk_end(b);
 204   obuck_cleanup();
 205   return 0;
 206 }
 207 #endif