/*
* Empire - A multi-player, client/server Internet based war game.
- * Copyright (C) 1986-2009, Dave Pare, Jeff Bailey, Thomas Ruschak,
- * Ken Stevens, Steve McClure
+ * Copyright (C) 1986-2011, Dave Pare, Jeff Bailey, Thomas Ruschak,
+ * Ken Stevens, Steve McClure, Markus Armbruster
*
- * This program is free software; you can redistribute it and/or modify
+ * Empire is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
+ * the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* ---
*
* Known contributors to this file:
* Dave Pare, 1989
* Steve McClure, 2000
- * Markus Armbruster, 2005-2008
+ * Markus Armbruster, 2005-2011
*/
#include <config.h>
static int do_write(struct empfile *, void *, int, int);
static unsigned get_seqno(struct empfile *, int);
static void new_seqno(struct empfile *, void *);
+static void must_be_fresh(struct empfile *, void *);
static void do_blank(struct empfile *, void *, int, int);
static int ef_check(int);
+static unsigned ef_generation;
+
/*
* Open the file-backed table TYPE (EF_SECTOR, ...).
* HOW are flags to control operation. Naturally, immutable flags are
ef_open(int type, int how, int nelt)
{
struct empfile *ep;
- int oflags, fd, fsiz, nslots;
+ int oflags, fd, fsiz, fids, nslots;
if (ef_check(type) < 0)
return 0;
/* open file */
ep = &empfile[type];
- if (CANT_HAPPEN(ep->fd >= 0))
+ if (CANT_HAPPEN(!ep->file || ep->base != EF_BAD || ep->fd >= 0))
return 0;
oflags = O_RDWR;
if (how & EFF_PRIVATE)
close(fd);
return 0;
}
- ep->fids = fsiz / ep->size;
- if (nelt >= 0 && nelt != ep->fids) {
+ fids = fsiz / ep->size;
+ if (nelt >= 0 && nelt != fids) {
logerror("Can't open %s (got %d records instead of %d)",
- ep->file, ep->fids, nelt);
+ ep->file, fids, nelt);
close(fd);
return 0;
}
if (ep->flags & EFF_STATIC) {
/* ep->cache already points to space for ep->csize elements */
if (how & EFF_MEM) {
- if (ep->fids > ep->csize) {
- logerror("Can't open %s: file larger than %d bytes",
- ep->file, ep->fids * ep->size);
+ if (fids > ep->csize) {
+ logerror("Can't open %s (file larger than %d records)",
+ ep->file, ep->csize);
close(fd);
return 0;
}
if (CANT_HAPPEN(ep->cache))
free(ep->cache);
if (how & EFF_MEM)
- nslots = ep->fids;
+ nslots = fids;
else
nslots = blksize(fd) / ep->size;
if (!ef_realloc_cache(ep, nslots)) {
}
ep->baseid = 0;
ep->cids = 0;
+ ep->fids = fids;
ep->flags = (ep->flags & EFF_IMMUTABLE) | (how & ~EFF_CREATE);
ep->fd = fd;
/* map file into cache */
- if ((how & EFF_MEM) && ep->fids) {
- if (fillcache(ep, 0) != ep->fids) {
+ if ((how & EFF_MEM) && fids) {
+ if (fillcache(ep, 0) != fids) {
ep->cids = 0; /* prevent cache flush */
- ep->flags &= EFF_IMMUTABLE; /* maintain invariant */
ef_close(type);
return 0;
}
}
- if (ep->onresize && ep->onresize(type) < 0)
- return 0;
+ if (ep->onresize)
+ ep->onresize(type);
return 1;
}
}
/*
- * Open the table TYPE as view of table BASE.
+ * Open the table TYPE, which is a view of a base table
+ * The table must not be already open.
* Return non-zero on success, zero on failure.
- * Beware: views work only as long as BASE doesn't change size!
- * You must call ef_close(TYPE) before closing BASE.
+ * Beware: views work only as long as the base table doesn't change size!
+ * You must close the view before closing its base table.
*/
int
-ef_open_view(int type, int base)
+ef_open_view(int type)
{
struct empfile *ep;
+ int base;
- if (CANT_HAPPEN(!EF_IS_VIEW(type)))
- return -1;
+ if (ef_check(type) < 0)
+ return 0;
ep = &empfile[type];
- if (CANT_HAPPEN(!(ef_flags(base) & EFF_MEM)))
+ base = ep->base;
+ if (ef_check(base) < 0)
+ return 0;
+ if (CANT_HAPPEN(!(ef_flags(base) & EFF_MEM)
+ || ep->file || ep->size != empfile[base].size
+ || ep->cache || ep->oninit || ep->postread
+ || ep->prewrite || ep->onresize))
return -1;
ep->cache = empfile[base].cache;
}
/*
- * Close the file-backed table TYPE (EF_SECTOR, ...).
+ * Close the open table TYPE (EF_SECTOR, ...).
* Return non-zero on success, zero on failure.
*/
int
return 0;
ep = &empfile[type];
- if (EF_IS_VIEW(type))
+ if (EF_IS_VIEW(type)) {
ep->cache = NULL;
- else {
+ ep->csize = 0;
+ } else {
if (!ef_flush(type))
retval = 0;
- ep->flags &= EFF_IMMUTABLE;
if (!(ep->flags & EFF_STATIC)) {
free(ep->cache);
ep->cache = NULL;
+ ep->csize = 0;
}
if (close(ep->fd) < 0) {
logerror("Error closing %s (%s)", ep->file, strerror(errno));
}
ep->fd = -1;
}
+ ep->flags &= EFF_IMMUTABLE;
ep->baseid = ep->cids = ep->fids = 0;
- if (ep->onresize && ep->onresize(type) < 0)
- retval = 0;
+ if (ep->onresize)
+ ep->onresize(type);
return retval;
}
/*
* Read element ID from table TYPE into buffer INTO.
* FIXME pass buffer size!
+ * INTO is marked fresh with ef_mark_fresh().
* Return non-zero on success, zero on failure.
*/
int
cachep = ep->cache + (id - ep->baseid) * ep->size;
}
memcpy(into, cachep, ep->size);
+ ef_mark_fresh(type, into);
if (ep->postread)
ep->postread(id, into);
* cache straight to disk.
* Cannot write beyond the end of fully cached table (flags & EFF_MEM).
* Can write at the end of partially cached table.
+ * FROM must be fresh; see ef_make_stale().
* Return non-zero on success, zero on failure.
*/
int
ep = &empfile[type];
if (CANT_HAPPEN((ep->flags & (EFF_MEM | EFF_PRIVATE)) == EFF_PRIVATE))
return 0;
- if (CANT_HAPPEN((ep->flags & EFF_MEM) ? id >= ep->fids : id > ep->fids))
- return 0; /* not implemented */
new_seqno(ep, from);
if (id >= ep->fids) {
- /* write beyond end of file extends it, take note */
+ /* beyond end of file */
+ if (CANT_HAPPEN((ep->flags & EFF_MEM) || id > ep->fids))
+ return 0; /* not implemented */
+ /* write at end of file extends it */
ep->fids = id + 1;
- if (ep->onresize && ep->onresize(type) < 0)
- return 0;
+ if (ep->onresize)
+ ep->onresize(type);
}
- if (id >= ep->baseid && id < ep->baseid + ep->cids)
+ if (id >= ep->baseid && id < ep->baseid + ep->cids) {
cachep = ep->cache + (id - ep->baseid) * ep->size;
- else
+ if (cachep != from)
+ must_be_fresh(ep, from);
+ } else
cachep = NULL;
if (ep->prewrite)
ep->prewrite(id, cachep, from);
* Increment sequence number in BUF, which is about to be written to EP.
* Do nothing if table is not EFF_TYPED (it has no sequence number
* then).
+ * Else, BUF's sequence number must match the one in EP's cache. If
+ * it doesn't, we're about to clobber a previous write.
*/
static void
new_seqno(struct empfile *ep, void *buf)
if (!(ep->flags & EFF_TYPED))
return;
old_seqno = get_seqno(ep, elt->uid);
- if (CANT_HAPPEN(old_seqno != elt->seqno))
- old_seqno = MAX(old_seqno, elt->seqno);
+ CANT_HAPPEN(old_seqno != elt->seqno);
elt->seqno = old_seqno + 1;
}
+/*
+ * Make all copies stale.
+ * Only fresh copies may be written back to the cache.
+ * To be called by functions that may yield the processor.
+ * Writing an copy when there has been a yield since it was read is
+ * unsafe, because we could clobber another thread's write then.
+ * Robust code must assume the that any function that may yield does
+ * yield. Marking copies stale there lets us catch unsafe writes.
+ */
+void
+ef_make_stale(void)
+{
+ ef_generation++;
+}
+
+/* Mark copy of an element of table TYPE in BUF fresh. */
+void
+ef_mark_fresh(int type, void *buf)
+{
+ struct empfile *ep;
+
+ if (ef_check(type) < 0)
+ return;
+ ep = &empfile[type];
+ if (!(ep->flags & EFF_TYPED))
+ return;
+ ((struct emptypedstr *)buf)->generation = ef_generation;
+}
+
+static void
+must_be_fresh(struct empfile *ep, void *buf)
+{
+ struct emptypedstr *elt = buf;
+
+ if (!(ep->flags & EFF_TYPED))
+ return;
+ CANT_HAPPEN(elt->generation != (ef_generation & 0xfff));
+}
+
/*
* Extend table TYPE by COUNT elements.
* Any pointers obtained from ef_ptr() become invalid.
}
}
ep->fids = id + count;
- if (ep->onresize && ep->onresize(type) < 0)
- return 0;
+ if (ep->onresize)
+ ep->onresize(type);
return 1;
}
/*
- * Initialize element ID for EP in BUF.
+ * Initialize element ID for table TYPE in BUF.
* FIXME pass buffer size!
+ * BUF is marked fresh with ef_mark_fresh().
*/
void
ef_blank(int type, int id, void *buf)
elt = buf;
elt->seqno = get_seqno(ep, elt->uid);
}
+ ef_mark_fresh(type, buf);
}
/*
ep->cids = count - ep->baseid;
}
- if (ep->onresize && ep->onresize(type) < 0)
- return 0;
+ if (ep->onresize)
+ ep->onresize(type);
return 1;
}
projects / empserver / blobdiff