1 | #ifndef AWS_COMMON_RING_BUFFER_INL |
2 | #define AWS_COMMON_RING_BUFFER_INL |
3 | /* |
4 | * Copyright 2010-2019 Amazon.com, Inc. or its affiliates. All Rights Reserved. |
5 | * |
6 | * Licensed under the Apache License, Version 2.0 (the "License"). |
7 | * You may not use this file except in compliance with the License. |
8 | * A copy of the License is located at |
9 | * |
10 | * http://aws.amazon.com/apache2.0 |
11 | * |
12 | * or in the "license" file accompanying this file. This file is distributed |
13 | * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either |
14 | * express or implied. See the License for the specific language governing |
15 | * permissions and limitations under the License. |
16 | */ |
17 | |
18 | #include <aws/common/ring_buffer.h> |
19 | |
20 | AWS_EXTERN_C_BEGIN |
21 | /* |
22 | * Checks whether atomic_ptr correctly points to a memory location within the bounds of the aws_ring_buffer |
23 | */ |
24 | AWS_STATIC_IMPL bool aws_ring_buffer_check_atomic_ptr( |
25 | const struct aws_ring_buffer *ring_buf, |
26 | const uint8_t *atomic_ptr) { |
27 | return (atomic_ptr >= ring_buf->allocation && atomic_ptr <= ring_buf->allocation_end); |
28 | } |
29 | |
30 | /** |
31 | * Checks whether the ring buffer is empty |
32 | */ |
33 | AWS_STATIC_IMPL bool aws_ring_buffer_is_empty(const struct aws_ring_buffer *ring_buf) { |
34 | uint8_t *head = (uint8_t *)aws_atomic_load_ptr(&ring_buf->head); |
35 | uint8_t *tail = (uint8_t *)aws_atomic_load_ptr(&ring_buf->tail); |
36 | return head == tail; |
37 | } |
38 | |
39 | /** |
40 | * Evaluates the set of properties that define the shape of all valid aws_ring_buffer structures. |
41 | * It is also a cheap check, in the sense it run in constant time (i.e., no loops or recursion). |
42 | */ |
43 | AWS_STATIC_IMPL bool aws_ring_buffer_is_valid(const struct aws_ring_buffer *ring_buf) { |
44 | uint8_t *head = (uint8_t *)aws_atomic_load_ptr(&ring_buf->head); |
45 | uint8_t *tail = (uint8_t *)aws_atomic_load_ptr(&ring_buf->tail); |
46 | bool head_in_range = aws_ring_buffer_check_atomic_ptr(ring_buf, head); |
47 | bool tail_in_range = aws_ring_buffer_check_atomic_ptr(ring_buf, tail); |
48 | /* if head points-to the first element of the buffer then tail must too */ |
49 | bool valid_head_tail = (head != ring_buf->allocation) || (tail == ring_buf->allocation); |
50 | return ring_buf && AWS_MEM_IS_READABLE(ring_buf->allocation, ring_buf->allocation_end - ring_buf->allocation) && |
51 | head_in_range && tail_in_range && valid_head_tail && (ring_buf->allocator != NULL); |
52 | } |
53 | AWS_EXTERN_C_END |
54 | #endif /* AWS_COMMON_RING_BUFFER_INL */ |
55 | |