1 | #ifndef AWS_COMMON_ZERO_INL |
2 | #define AWS_COMMON_ZERO_INL |
3 | |
4 | /* |
5 | * Copyright 2010-2019 Amazon.com, Inc. or its affiliates. All Rights Reserved. |
6 | * |
7 | * Licensed under the Apache License, Version 2.0 (the "License"). |
8 | * You may not use this file except in compliance with the License. |
9 | * A copy of the License is located at |
10 | * |
11 | * http://aws.amazon.com/apache2.0 |
12 | * |
13 | * or in the "license" file accompanying this file. This file is distributed |
14 | * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either |
15 | * express or implied. See the License for the specific language governing |
16 | * permissions and limitations under the License. |
17 | */ |
18 | |
19 | #include <aws/common/stdbool.h> |
20 | #include <aws/common/stdint.h> |
21 | #include <aws/common/zero.h> |
22 | #include <string.h> |
23 | |
24 | AWS_EXTERN_C_BEGIN |
25 | /** |
26 | * Returns whether each byte is zero. |
27 | */ |
28 | AWS_STATIC_IMPL |
29 | bool aws_is_mem_zeroed(const void *buf, size_t bufsize) { |
30 | /* Optimization idea: vectorized instructions to check more than 64 bits at a time. */ |
31 | |
32 | /* Check 64 bits at a time */ |
33 | const uint64_t *buf_u64 = (const uint64_t *)buf; |
34 | const size_t num_u64_checks = bufsize / 8; |
35 | size_t i; |
36 | for (i = 0; i < num_u64_checks; ++i) { |
37 | if (buf_u64[i]) { |
38 | return false; |
39 | } |
40 | } |
41 | |
42 | /* Update buf to where u64 checks left off */ |
43 | buf = buf_u64 + num_u64_checks; |
44 | bufsize = bufsize % 8; |
45 | |
46 | /* Check 8 bits at a time */ |
47 | const uint8_t *buf_u8 = (const uint8_t *)buf; |
48 | for (i = 0; i < bufsize; ++i) { |
49 | if (buf_u8[i]) { |
50 | return false; |
51 | } |
52 | } |
53 | |
54 | return true; |
55 | } |
56 | |
57 | AWS_EXTERN_C_END |
58 | |
59 | #endif /* AWS_COMMON_ZERO_INL */ |
60 | |