Pass old element to empfile callback prewrite()

Change sct_prewrite(), shp_prewrite(), pln_prewrite(), lnd_prewrite(),
nuk_prewrite() accordingly.  New argument isn't used for anything,
yet.

src/lib/common/file.c

@@ -314,7 +314,7 @@ int
 ef_read(int type, int id, void *into)
 {
     struct empfile *ep;
-    void *from;
+    void *cachep;
 
     if (ef_check(type) < 0)
 	return 0;
@@ -325,15 +325,15 @@ ef_read(int type, int id, void *into)
 	return 0;
 
     if (ep->flags & EFF_MEM) {
-	from = ep->cache + id * ep->size;
+	cachep = ep->cache + id * ep->size;
     } else {
 	if (ep->baseid + ep->cids <= id || ep->baseid > id) {
 	    if (fillcache(ep, id) < 1)
 		return 0;
 	}
-	from = ep->cache + (id - ep->baseid) * ep->size;
+	cachep = ep->cache + (id - ep->baseid) * ep->size;
     }
-    memcpy(into, from, ep->size);
+    memcpy(into, cachep, ep->size);
 
     if (ep->postread)
 	ep->postread(id, into);
@@ -480,15 +480,19 @@ int
 ef_write(int type, int id, void *from)
 {
     struct empfile *ep;
-    char *to;
+    char *cachep;
 
     if (ef_check(type) < 0)
 	return 0;
     ep = &empfile[type];
     if (CANT_HAPPEN((ep->flags & (EFF_MEM | EFF_PRIVATE)) == EFF_PRIVATE))
 	return 0;
+    if (id >= ep->baseid && id < ep->baseid + ep->cids)
+	cachep = ep->cache + (id - ep->baseid) * ep->size;
+    else
+	cachep = NULL;
     if (ep->prewrite)
-	ep->prewrite(id, from);
+	ep->prewrite(id, cachep, from);
     if (CANT_HAPPEN((ep->flags & EFF_MEM) ? id >= ep->fids : id > ep->fids))
 	return 0;		/* not implemented */
     new_seqno(ep, from);
@@ -496,12 +500,8 @@ ef_write(int type, int id, void *from)
 	if (do_write(ep, from, id, 1) < 0)
 	    return 0;
     }
-    if (id >= ep->baseid && id < ep->baseid + ep->cids) {
-	/* update the cache if necessary */
-	to = ep->cache + (id - ep->baseid) * ep->size;
-	if (to != from)
-	    memcpy(to, from, ep->size);
-    }
+    if (cachep && cachep != from)	/* update the cache if necessary */
+	memcpy(cachep, from, ep->size);
     if (id >= ep->fids) {
 	/* write beyond end of file extends it, take note */
 	ep->fids = id + 1;

src/lib/subs/fileinit.c

@@ -42,7 +42,7 @@
 struct fileinit {
     int ef_type;
     void (*postread) (int, void *);
-    void (*prewrite) (int, void *);
+    void (*prewrite) (int, void *, void *);
 };
 
 static struct fileinit fileinit[] = {

src/lib/subs/land.c

@@ -109,9 +109,9 @@ lnd_postread(int n, void *ptr)
 }
 
 void
-lnd_prewrite(int n, void *ptr)
+lnd_prewrite(int n, void *old, void *new)
 {
-    struct lndstr *llp = ptr;
+    struct lndstr *llp = new;
     struct lndstr *lp;
     struct plnstr *pp;
     int i;

src/lib/subs/nuke.c

@@ -74,9 +74,9 @@ nuk_postread(int n, void *ptr)
 }
 
 void
-nuk_prewrite(int n, void *ptr)
+nuk_prewrite(int n, void *old, void *new)
 {
-    struct nukstr *np = ptr;
+    struct nukstr *np = new;
 
     if (np->nuk_effic == 0) {
 	if (np->nuk_own)

src/lib/subs/plane.c

@@ -108,9 +108,9 @@ pln_postread(int n, void *ptr)
 }
 
 void
-pln_prewrite(int n, void *ptr)
+pln_prewrite(int n, void *old, void *new)
 {
-    struct plnstr *pp = ptr;
+    struct plnstr *pp = new;
     struct nukstr *np;
     int i;
 

src/lib/subs/sect.c

@@ -59,9 +59,9 @@ sct_postread(int id, void *ptr)
 }
 
 void
-sct_prewrite(int id, void *ptr)
+sct_prewrite(int id, void *old, void *new)
 {
-    struct sctstr *sp = ptr;
+    struct sctstr *sp = new;
     int mil, civs;
     natid own;
 

src/lib/subs/ship.c

@@ -62,9 +62,9 @@ shp_postread(int n, void *ptr)
 }
 
 void
-shp_prewrite(int n, void *ptr)
+shp_prewrite(int n, void *old, void *new)
 {
-    struct shpstr *sp = ptr;
+    struct shpstr *sp = new;
     struct lndstr *lp;
     struct plnstr *pp;
     int i;