1 /*
2 * Copyright © 2015 Intel Corporation
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining a
5 * copy of this software and associated documentation files (the "Software"),
6 * to deal in the Software without restriction, including without limitation
7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8 * and/or sell copies of the Software, and to permit persons to whom the
9 * Software is furnished to do so, subject to the following conditions:
10 *
11 * The above copyright notice and this permission notice (including the next
12 * paragraph) shall be included in all copies or substantial portions of the
13 * Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
21 * IN THE SOFTWARE.
22 */
23
24 #include <string.h>
25 #include "util/u_math.h"
26 #include "util/u_vector.h"
27
28 /** @file u_vector.c
29 *
30 * A dynamically growable, circular buffer. Elements are added at head and
31 * removed from tail. head and tail are free-running uint32_t indices and we
32 * only compute the modulo with size when accessing the array. This way,
33 * number of bytes in the queue is always head - tail, even in case of
34 * wraparound.
35 */
36
37 int
u_vector_init(struct u_vector * vector,uint32_t element_size,uint32_t size)38 u_vector_init(struct u_vector *vector, uint32_t element_size, uint32_t size)
39 {
40 assert(util_is_power_of_two(size));
41 assert(element_size < size && util_is_power_of_two(element_size));
42
43 vector->head = 0;
44 vector->tail = 0;
45 vector->element_size = element_size;
46 vector->size = size;
47 vector->data = malloc(size);
48
49 return vector->data != NULL;
50 }
51
52 void *
u_vector_add(struct u_vector * vector)53 u_vector_add(struct u_vector *vector)
54 {
55 uint32_t offset, size, split, src_tail, dst_tail;
56 void *data;
57
58 if (vector->head - vector->tail == vector->size) {
59 size = vector->size * 2;
60 data = malloc(size);
61 if (data == NULL)
62 return NULL;
63 src_tail = vector->tail & (vector->size - 1);
64 dst_tail = vector->tail & (size - 1);
65 if (src_tail == 0) {
66 /* Since we know that the vector is full, this means that it's
67 * linear from start to end so we can do one copy.
68 */
69 memcpy((char *)data + dst_tail, vector->data, vector->size);
70 } else {
71 /* In this case, the vector is split into two pieces and we have
72 * to do two copies. We have to be careful to make sure each
73 * piece goes to the right locations. Thanks to the change in
74 * size, it may or may not still wrap around.
75 */
76 split = u_align_u32(vector->tail, vector->size);
77 assert(vector->tail <= split && split < vector->head);
78 memcpy((char *)data + dst_tail, (char *)vector->data + src_tail,
79 split - vector->tail);
80 memcpy((char *)data + (split & (size - 1)), vector->data,
81 vector->head - split);
82 }
83 free(vector->data);
84 vector->data = data;
85 vector->size = size;
86 }
87
88 assert(vector->head - vector->tail < vector->size);
89
90 offset = vector->head & (vector->size - 1);
91 vector->head += vector->element_size;
92
93 return (char *)vector->data + offset;
94 }
95
96 void *
u_vector_remove(struct u_vector * vector)97 u_vector_remove(struct u_vector *vector)
98 {
99 uint32_t offset;
100
101 if (vector->head == vector->tail)
102 return NULL;
103
104 assert(vector->head - vector->tail <= vector->size);
105
106 offset = vector->tail & (vector->size - 1);
107 vector->tail += vector->element_size;
108
109 return (char *)vector->data + offset;
110 }
111