+static void overlay_save_count() {
+ lseek( overlay.source.fd, overlay.source.to, SEEK_SET );
+ size_t size = sizeof( overlay.count );
+ char *p = (char *) &overlay.count ;
+ while ( size > 0 ) {
+ size_t n = write( overlay.source.fd, p, size );
+ if ( n < 0 ) {
+ perror( overlay.source.filename );
+ exit( 1 );
+ }
+ size -= n;
+ p += n;
+ }
+ if ( overlay.source.dirty++ > 1000 ) {
+ fsync( overlay.source.fd );
+ overlay.source.dirty = 0;
+ }
+}
+
+static void overlay_save_table(size_t lo,size_t hi) {
+ char *p = (char *) FRAG(lo);
+ size_t pos = overlay.source.to + sizeof( overlay.count ) +
+ lo * sizeof( struct Region );
+ size_t size = ( hi - lo ) * sizeof( struct Region );
+ if ( pos != lseek( overlay.source.fd, pos, SEEK_SET ) ) {
+ fprintf( stderr, "%s: seek error\n", overlay.source.filename );
+ exit( 1 );
+ }
+ while ( size > 0 ) {
+ size_t n = write( overlay.source.fd, p, size );
+ if ( n < 0 ) {
+ perror( overlay.source.filename );
+ exit( 1 );
+ }
+ size -= n;
+ p += n;
+ }
+ if ( overlay.source.dirty++ > 1000 ) {
+ fsync( overlay.source.fd );
+ overlay.source.dirty = 0;
+ }
+}
+
+static void overlay_insert(size_t p,off_t pos,size_t size) {
+ size_t bytes;
+ if ( overlay.count >= overlay.limit ) {
+ overlay.limit = overlay.count + 10;
+ bytes = overlay.limit * sizeof( struct Region );
+ overlay.table = overlay.table?
+ realloc( overlay.table, bytes ) : malloc( bytes );
+ }
+ bytes = ( overlay.count++ - p ) * sizeof( struct Region );
+ if ( bytes ) {
+ memmove( FRAG( p+1 ), FRAG( p ), bytes );
+ }
+ FRAG( p )->pos = pos;
+ FRAG( p )->size = size;
+ overlay_save_count();
+}
+
+static void overlay_delete(size_t p) {
+ if ( p < --overlay.count ) {
+ size_t size = ( overlay.count - p ) * sizeof( struct Region );
+ memmove( FRAG(p), FRAG(p+1), size );
+ }
+ overlay_save_count();
+}
+
+static void overlay_mark(off_t pos,size_t size) {
+#if DEBUG
+ fprintf( stderr, "overlay_mark( %ld, %ld )\n", pos, size );
+#endif
+ int deleted = 0;
+ ssize_t q;
+ ssize_t p = overlay_prior_fragment( pos );
+ // p is the nearest region below pos (or -1)
+ if ( p >= 0 && pos <= END(p) ) {
+ // p overlaps mark region
+ if ( END(p) >= pos + size ) {
+#if DEBUG
+ fprintf( stderr, "overlay size 1( %ld )\n", FRAG(p)->size );
+#endif
+ return; // new mark within existing.