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
37int
38u_vector_init(struct u_vector *vector, uint32_t element_size, uint32_t size)
39{
40   assert(util_is_power_of_two_nonzero(size));
41   assert(element_size < size && util_is_power_of_two_nonzero(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
52void *
53u_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
96void *
97u_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