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git.proxmox.com Git - ovs.git/blob - lib/byteq.c
1 /* Copyright (c) 2008, 2009, 2012 Nicira, Inc.
3 * Licensed under the Apache License, Version 2.0 (the "License");
4 * you may not use this file except in compliance with the License.
5 * You may obtain a copy of the License at:
7 * http://www.apache.org/licenses/LICENSE-2.0
9 * Unless required by applicable law or agreed to in writing, software
10 * distributed under the License is distributed on an "AS IS" BASIS,
11 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 * See the License for the specific language governing permissions and
13 * limitations under the License.
23 /* The queue size must be a power of 2. */
24 BUILD_ASSERT_DECL(!(BYTEQ_SIZE
& (BYTEQ_SIZE
- 1)));
26 /* Initializes 'q' as empty. */
28 byteq_init(struct byteq
*q
)
30 q
->head
= q
->tail
= 0;
33 /* Returns the number of bytes current queued in 'q'. */
35 byteq_used(const struct byteq
*q
)
37 return q
->head
- q
->tail
;
40 /* Returns the number of bytes that can be added to 'q' without overflow. */
42 byteq_avail(const struct byteq
*q
)
44 return BYTEQ_SIZE
- byteq_used(q
);
47 /* Returns true if no bytes are queued in 'q',
48 * false if at least one byte is queued. */
50 byteq_is_empty(const struct byteq
*q
)
52 return !byteq_used(q
);
55 /* Returns true if 'q' has no room to queue additional bytes,
56 * false if 'q' has room for at least one more byte. */
58 byteq_is_full(const struct byteq
*q
)
60 return !byteq_avail(q
);
63 /* Adds 'c' at the head of 'q', which must not be full. */
65 byteq_put(struct byteq
*q
, uint8_t c
)
67 ovs_assert(!byteq_is_full(q
));
72 /* Adds the 'n' bytes in 'p' at the head of 'q', which must have at least 'n'
73 * bytes of free space. */
75 byteq_putn(struct byteq
*q
, const void *p_
, size_t n
)
77 const uint8_t *p
= p_
;
78 ovs_assert(byteq_avail(q
) >= n
);
80 size_t chunk
= MIN(n
, byteq_headroom(q
));
81 memcpy(byteq_head(q
), p
, chunk
);
82 byteq_advance_head(q
, chunk
);
88 /* Appends null-terminated string 's' to the head of 'q', which must have
89 * enough space. The null terminator is not added to 'q'. */
91 byteq_put_string(struct byteq
*q
, const char *s
)
93 byteq_putn(q
, s
, strlen(s
));
96 /* Removes a byte from the tail of 'q' and returns it. 'q' must not be
99 byteq_get(struct byteq
*q
)
102 ovs_assert(!byteq_is_empty(q
));
108 /* Writes as much of 'q' as possible to 'fd'. Returns 0 if 'q' is fully
109 * drained by the write, otherwise a positive errno value (e.g. EAGAIN if a
110 * socket or tty buffer filled up). */
112 byteq_write(struct byteq
*q
, int fd
)
114 while (!byteq_is_empty(q
)) {
115 ssize_t n
= write(fd
, byteq_tail(q
), byteq_tailroom(q
));
117 byteq_advance_tail(q
, n
);
126 /* Reads as much possible from 'fd' into 'q'. Returns 0 if 'q' is completely
127 * filled up by the read, EOF if end-of-file was reached before 'q' was filled,
128 * and otherwise a positive errno value (e.g. EAGAIN if a socket or tty buffer
131 byteq_read(struct byteq
*q
, int fd
)
133 while (!byteq_is_full(q
)) {
134 ssize_t n
= read(fd
, byteq_head(q
), byteq_headroom(q
));
136 byteq_advance_head(q
, n
);
138 return !n
? EOF
: errno
;
144 /* Returns the number of contiguous bytes of in-use space starting at the tail
147 byteq_tailroom(const struct byteq
*q
)
149 int used
= byteq_used(q
);
150 int tail_to_end
= BYTEQ_SIZE
- (q
->tail
& (BYTEQ_SIZE
- 1));
151 return MIN(used
, tail_to_end
);
154 /* Returns the first in-use byte of 'q', the point at which data is removed
157 byteq_tail(const struct byteq
*q
)
159 return &q
->buffer
[q
->tail
& (BYTEQ_SIZE
- 1)];
162 /* Removes 'n' bytes from the tail of 'q', which must have at least 'n' bytes
165 byteq_advance_tail(struct byteq
*q
, unsigned int n
)
167 ovs_assert(byteq_tailroom(q
) >= n
);
171 /* Returns the byte after the last in-use byte of 'q', the point at which new
172 * data will be added to 'q'. */
174 byteq_head(struct byteq
*q
)
176 return &q
->buffer
[q
->head
& (BYTEQ_SIZE
- 1)];
179 /* Returns the number of contiguous bytes of free space starting at the head
182 byteq_headroom(const struct byteq
*q
)
184 int avail
= byteq_avail(q
);
185 int head_to_end
= BYTEQ_SIZE
- (q
->head
& (BYTEQ_SIZE
- 1));
186 return MIN(avail
, head_to_end
);
189 /* Adds to 'q' the 'n' bytes after the last currently in-use byte of 'q'. 'q'
190 * must have at least 'n' bytes of headroom. */
192 byteq_advance_head(struct byteq
*q
, unsigned int n
)
194 ovs_assert(byteq_headroom(q
) >= n
);