Add utility functions for mutator's "propose change" opcode

runtime/common/input.c

@@ -93,3 +93,16 @@ void res_mark_consumed_reference(struct fuzzer_state *state,
   unsigned offset = res_get_cur_offset(state) - id_bytes;
   mutator_ref_resource(kind, id, id_bytes, offset);
 }
+
+void res_propose_change_here(struct fuzzer_state *state,
+                             uint64_t replacement, unsigned size) {
+  unsigned offset = res_get_cur_offset(state) - size;
+  mutator_propose_change(offset, replacement, size);
+}
+
+void res_propose_change_if_different(struct fuzzer_state *state, unsigned offset,
+                                     uint64_t replacement, unsigned size) {
+  void *current_data = &state->constant_state.input_buffer[offset];
+  if (memcmp(&current_data, &replacement, size))
+    mutator_propose_change(offset, replacement, size);
+}

runtime/include/kbdysch/input.h

@@ -96,6 +96,16 @@ void res_mark_section_start(struct fuzzer_state *state);
 void res_mark_consumed_reference(struct fuzzer_state *state,
                                  int kind, int id, unsigned id_bytes);
 
+/**
+ * Utility function for mutator interface: call it right after
+ * reading the data to be patched.
+ */
+void res_propose_change_here(struct fuzzer_state *state,
+                             uint64_t replacement, unsigned size);
+
+void res_propose_change_if_different(struct fuzzer_state *state, unsigned offset,
+                                     uint64_t replacement, unsigned size);
+
 #ifdef __cplusplus
 }
 #endif