text: /*
   * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
   *
   * Licensed under the Apache License, Version 2.0 (the "License").
   * You may not use this file except in compliance with the License.
   * A copy of the License is located at
   *
   *  http://aws.amazon.com/apache2.0
   *
   * or in the "license" file accompanying this file. This file is distributed
   * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
   * express or implied. See the License for the specific language governing
   * permissions and limitations under the License.
   */
  
  #include "api/s2n.h"
  #include "stuffer/s2n_stuffer.h"
  
  #include <sys/param.h>
  #include <assert.h>
  
  #include <cbmc_proof/cbmc_utils.h>
  #include <cbmc_proof/make_common_datastructures.h>
  #include <cbmc_proof/proof_allocators.h>
  
  void s2n_stuffer_write_bytes_harness() {
      /* Non-deterministic inputs. */
      struct s2n_stuffer *stuffer = cbmc_allocate_s2n_stuffer();
      __CPROVER_assume(s2n_stuffer_is_valid(stuffer));
      uint32_t index;
      uint32_t size;
      uint8_t *data = can_fail_malloc(size);
  
      /* Non-deterministically set initialized (in s2n_mem) to true. */
      if(nondet_bool()) {
          s2n_mem_init();
      }
  
      /* Save previous state from stuffer. */
      struct s2n_stuffer old_stuffer = *stuffer;
  
      /* Store a byte from the stuffer that wont be overwritten to compare if the write succeeds. */
      __CPROVER_assume(index < stuffer->blob.size);
      if(__CPROVER_overflow_plus(old_stuffer.write_cursor, size)) {
          __CPROVER_assume(index < old_stuffer.write_cursor);
      } else {
          __CPROVER_assume(index < old_stuffer.write_cursor || index >= old_stuffer.write_cursor + size);
      }
      uint8_t untouched_byte = stuffer->blob.data[index];
  
      /* Operation under verification. */
      if (s2n_stuffer_write_bytes(stuffer, data, size) == S2N_SUCCESS) {
          assert(stuffer->write_cursor == old_stuffer.write_cursor + size);
          assert(stuffer->blob.data[index] == untouched_byte);
          assert(stuffer->high_water_mark == MAX(old_stuffer.write_cursor + size, old_stuffer.high_water_mark));
          assert(s2n_stuffer_is_valid(stuffer));
      } else {
          assert(stuffer->write_cursor == old_stuffer.write_cursor);
          assert(stuffer->high_water_mark == old_stuffer.high_water_mark);
      }
      assert(stuffer->read_cursor == old_stuffer.read_cursor);
  }
  