gz_compress
gz_compress(in, out);
gz_compress(stdin, file);
gz_compress(in, file);
in_size = gz_compress(in, out, &size, basename(file), (uint32_t)isb.st_mtime);
gz_compress(STDIN_FILENO, STDOUT_FILENO, &gsize, "", mtime);
#define gz_compress(if, of, sz, fn, tm) gz_compress(if, of, sz)
static off_t gz_compress(int, int, off_t *, const char *, uint32_t);