1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
|
/*
* Copyright (c) 2018-2019 Richard Braun.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* Upstream site with license notes :
* http://git.sceen.net/rbraun/librbraun.git/
*
*
* FIFO message buffer.
*/
#ifndef KERN_MBUF_H
#define KERN_MBUF_H
#include <stdbool.h>
#include <stddef.h>
#include <kern/cbuf.h>
/*
* Message buffer.
*
* Message buffers are built on top of circular byte buffers. They provide
* discrete message transfer from a producer to a consumer.
*
* The order is computed from the maximum message size, and is used to
* determine a header size that can represent up to 2^order - 1 bytes.
*/
struct mbuf {
struct cbuf cbuf;
size_t max_msg_size;
unsigned int order;
};
static inline size_t
mbuf_start(const struct mbuf *mbuf)
{
return cbuf_start(&mbuf->cbuf);
}
static inline size_t
mbuf_end(const struct mbuf *mbuf)
{
return cbuf_end(&mbuf->cbuf);
}
/*
* Initialize a message buffer.
*
* The descriptor is set to use the given buffer for storage. Capacity
* must be a power-of-two.
*/
void mbuf_init(struct mbuf *mbuf, void *buf, size_t capacity,
size_t max_msg_size);
/*
* Clear a message buffer.
*/
void mbuf_clear(struct mbuf *mbuf);
/*
* Push a message to a message buffer.
*
* If the message doesn't fit in the message buffer, either because it is
* larger than the capacity, or because the function isn't allowed to erase
* old messages and the message buffer doesn't have enough available memory
* for the new message, EMSGSIZE is returned. If the message is larger than
* the maximum message size, EINVAL is returned.
*/
int mbuf_push(struct mbuf *mbuf, const void *buf, size_t size, bool erase);
/*
* Pop a message from a message buffer.
*
* On entry, the sizep argument points to the size of the output buffer.
* On return, it is updated to the size of the message. If the message
* doesn't fit in the output buffer, it is not popped, EMSGSIZE is
* returned, but the sizep argument is updated nonetheless to let the
* user know the message size, to potentially retry with a larger buffer.
*
* If the buffer is empty, EAGAIN is returned, and the size of the output
* buffer is unmodified.
*
* The output buffer may be NULL, in which case this function acts as if
* it wasn't, but without writing output data.
*/
int mbuf_pop(struct mbuf *mbuf, void *buf, size_t *sizep);
/*
* Read a message from a message buffer.
*
* On entry, the indexp argument points to the index of the message to
* read in the message buffer, and the sizep argument points to the size
* of the output buffer. On return, if successful, indexp is updated
* to the index of the next message, and sizep to the size of the
* message read.
*
* If the message doesn't fit in the output buffer, it is not read,
* EMSGSIZE is returned, and the sizep argument is updated nonetheless
* to let the user know the message size, to potentially retry with a
* larger buffer.
*
* If the given index refers to the end of the buffer, then EAGAIN is
* returned. If it's outside buffer boundaries, EINVAL is returned.
* Otherwise, if it doesn't point to the beginning of a message, the
* behavior is undefined.
*
* The message buffer isn't changed by this operation.
*/
int mbuf_read(const struct mbuf *mbuf, size_t *indexp,
void *buf, size_t *sizep);
#endif /* KERN_MBUF_H */
|
