Fixed crash on zero-byte read/write (thanks, Ensiform!).

CHANGELOG

@@ -4,6 +4,7 @@
 
 -- stuff in the stable-1.0 branch, backported from 2.0.0 dev branch, etc ---
 
+07112007 - Fixed crash on zero-byte read/write (thanks, Ensiform!).
 05052007 - Fixed zip archiver: could do bogus seek if a small, non-zip file
            got put through isArchive().
 04022007 - Fixed Doxygen comment.

physfs.c

@@ -1797,6 +1797,8 @@ PHYSFS_sint64 PHYSFS_read(PHYSFS_file *handle, void *buffer,
     FileHandle *h = (FileHandle *) handle->opaque;
 
     BAIL_IF_MACRO(!h->forReading, ERR_FILE_ALREADY_OPEN_W, -1);
+    BAIL_IF_MACRO(objSize == 0, NULL, 0);
+    BAIL_IF_MACRO(objCount == 0, NULL, 0);
     if (h->buffer != NULL)
         return(doBufferedRead(handle, buffer, objSize, objCount));
 
@@ -1830,6 +1832,8 @@ PHYSFS_sint64 PHYSFS_write(PHYSFS_file *handle, const void *buffer,
     FileHandle *h = (FileHandle *) handle->opaque;
 
     BAIL_IF_MACRO(h->forReading, ERR_FILE_ALREADY_OPEN_R, -1);
+    BAIL_IF_MACRO(objSize == 0, NULL, 0);
+    BAIL_IF_MACRO(objCount == 0, NULL, 0);
     if (h->buffer != NULL)
         return(doBufferedWrite(handle, buffer, objSize, objCount));