1/*
2 * Copyright (c) 2014-2020 Pavel Kalvoda <me@pavelkalvoda.com>
3 *
4 * libcbor is free software; you can redistribute it and/or modify
5 * it under the terms of the MIT license. See LICENSE for details.
6 */
7
8#include "memory_utils.h"
9#include "cbor/common.h"
10
11// TODO: Consider builtins
12// (https://gcc.gnu.org/onlinedocs/gcc/Integer-Overflow-Builtins.html)
13
14/** Highest on bit position */
15size_t _cbor_highest_bit(size_t number) {
16  size_t bit = 0;
17  while (number != 0) {
18    bit++;
19    number >>= 1;
20  }
21
22  return bit;
23}
24
25bool _cbor_safe_to_multiply(size_t a, size_t b) {
26  if (a <= 1 || b <= 1) return true;
27  return _cbor_highest_bit(a) + _cbor_highest_bit(b) <= sizeof(size_t) * 8;
28}
29
30bool _cbor_safe_to_add(size_t a, size_t b) {
31  // Unsigned integer overflow doesn't constitute UB
32  size_t sum = a + b;
33  return sum >= a && sum >= b;
34}
35
36size_t _cbor_safe_signaling_add(size_t a, size_t b) {
37  if (a == 0 || b == 0) return 0;
38  if (_cbor_safe_to_add(a, b)) return a + b;
39  return 0;
40}
41
42void* _cbor_alloc_multiple(size_t item_size, size_t item_count) {
43  if (_cbor_safe_to_multiply(item_size, item_count)) {
44    return _cbor_malloc(item_size * item_count);
45  } else {
46    return NULL;
47  }
48}
49
50void* _cbor_realloc_multiple(void* pointer, size_t item_size,
51                             size_t item_count) {
52  if (_cbor_safe_to_multiply(item_size, item_count)) {
53    return _cbor_realloc(pointer, item_size * item_count);
54  } else {
55    return NULL;
56  }
57}
58