+struct unzip_state {
+#if !USE_INFLATE
+ gzFile zf;
+#endif
+ size_t mapped_size;
+ void **whole;
+ void *buffer;
+ size_t size;
+ void *input_buffer;
+ off_t input_pos;
+};
+
+static inline bool
+bigger_buffer (struct unzip_state *state, size_t start)
+{
+ size_t more = state->size ? state->size * 2 : start;
+ char *b = realloc (state->buffer, more);
+ while (unlikely (b == NULL) && more >= state->size + 1024)
+ b = realloc (state->buffer, more -= 1024);
+ if (unlikely (b == NULL))
+ return false;
+ state->buffer = b;
+ state->size = more;
+ return true;
+}
+
+static inline void
+smaller_buffer (struct unzip_state *state, size_t end)
+{
+ state->buffer =
+ realloc (state->buffer, end) ?: end == 0 ? NULL : state->buffer;
+ state->size = end;
+}
+
+static inline Dwfl_Error
+fail (struct unzip_state *state, Dwfl_Error failure)
+{
+ if (state->input_pos == (off_t) state->mapped_size)
+ *state->whole = state->input_buffer;
+ else
+ {
+ free (state->input_buffer);
+ *state->whole = NULL;
+ }
+ free (state->buffer);
+ return failure;
+}
+
+static inline Dwfl_Error
+zlib_fail (struct unzip_state *state, int result)
+{
+ switch (result)
+ {
+ case Z (MEM_ERROR):
+ return fail (state, DWFL_E_NOMEM);
+ case Z (ERRNO):
+ return fail (state, DWFL_E_ERRNO);
+ default:
+ return fail (state, DWFL_E_ZLIB);
+ }
+}
+
+#if !USE_INFLATE
+static Dwfl_Error
+open_stream (int fd, off_t start_offset, struct unzip_state *state)
+{
+ int d = dup (fd);
+ if (unlikely (d < 0))
+ return DWFL_E_BADELF;
+ if (start_offset != 0)
+ {
+ off_t off = lseek (d, start_offset, SEEK_SET);
+ if (off != start_offset)
+ {
+ close (d);
+ return DWFL_E_BADELF;
+ }
+ }
+ state->zf = gzdopen (d, "r");
+ if (unlikely (state->zf == NULL))
+ {
+ close (d);
+ return zlib_fail (state, Z (MEM_ERROR));
+ }
+
+ /* From here on, zlib will close D. */
+
+ return DWFL_E_NOERROR;
+}
+#endif
+