libcbor 0.12.0
libcbor is a C library for parsing and generating CBOR, the general-purpose schema-less binary data format.
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memory_utils.c
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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
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}
_cbor_malloc_t _cbor_malloc
Definition allocators.c:10
_cbor_realloc_t _cbor_realloc
Definition allocators.c:11
bool _cbor_safe_to_add(size_t a, size_t b)
Can a and b be added without overflowing size_t?
size_t _cbor_safe_signaling_add(size_t a, size_t b)
Adds a and b, propagating zeros and returning 0 on overflow.
void * _cbor_realloc_multiple(void *pointer, size_t item_size, size_t item_count)
Overflow-proof contiguous array reallocation.
void * _cbor_alloc_multiple(size_t item_size, size_t item_count)
Overflow-proof contiguous array allocation.
size_t _cbor_highest_bit(size_t number)
Highest on bit position.
bool _cbor_safe_to_multiply(size_t a, size_t b)
Can a and b be multiplied without overflowing size_t?