+static unsigned long do_compress(void **pptr, unsigned long size)
+{
+ z_stream stream;
+ void *in, *out;
+ unsigned long maxsize;
+
+ memset(&stream, 0, sizeof(stream));
+ deflateInit(&stream, pack_compression_level);
+ maxsize = deflateBound(&stream, size);
+
+ in = *pptr;
+ out = xmalloc(maxsize);
+ *pptr = out;
+
+ stream.next_in = in;
+ stream.avail_in = size;
+ stream.next_out = out;
+ stream.avail_out = maxsize;
+ while (deflate(&stream, Z_FINISH) == Z_OK)
+ ; /* nothing */
+ deflateEnd(&stream);
+
+ free(in);
+ return stream.total_out;
+}
+