summaryrefslogtreecommitdiffstats
path: root/video/mp_image_pool.c
blob: 17c2526b6fe4ca5777ef11baf2db1d0ae9fdd893 (plain)
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
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
/*
 * This file is part of mpv.
 *
 * mpv 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 2 of the License, or
 * (at your option) any later version.
 *
 * mpv 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 mpv; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include "config.h"

#include <stddef.h>
#include <stdbool.h>
#include <pthread.h>
#include <assert.h>

#include "talloc.h"

#include "common/common.h"
#include "video/mp_image.h"

#include "mp_image_pool.h"

static pthread_mutex_t pool_mutex = PTHREAD_MUTEX_INITIALIZER;
#define pool_lock() pthread_mutex_lock(&pool_mutex)
#define pool_unlock() pthread_mutex_unlock(&pool_mutex)

// Thread-safety: the pool itself is not thread-safe, but pool-allocated images
// can be referenced and unreferenced from other threads. (As long as the image
// destructors are thread-safe.)

struct mp_image_pool {
    int max_count;

    struct mp_image **images;
    int num_images;

    mp_image_allocator allocator;
    void *allocator_ctx;

    bool use_lru;
    unsigned int lru_counter;
};

// Used to gracefully handle the case when the pool is freed while image
// references allocated from the image pool are still held by someone.
struct image_flags {
    // If both of these are false, the image must be freed.
    bool referenced;            // outside mp_image reference exists
    bool pool_alive;            // the mp_image_pool references this
    unsigned int order;         // for LRU allocation (basically a timestamp)
};

static void image_pool_destructor(void *ptr)
{
    struct mp_image_pool *pool = ptr;
    mp_image_pool_clear(pool);
}

struct mp_image_pool *mp_image_pool_new(int max_count)
{
    struct mp_image_pool *pool = talloc_ptrtype(NULL, pool);
    talloc_set_destructor(pool, image_pool_destructor);
    *pool = (struct mp_image_pool) {
        .max_count = max_count,
    };
    return pool;
}

void mp_image_pool_clear(struct mp_image_pool *pool)
{
    for (int n = 0; n < pool->num_images; n++) {
        struct mp_image *img = pool->images[n];
        struct image_flags *it = img->priv;
        bool referenced;
        pool_lock();
        assert(it->pool_alive);
        it->pool_alive = false;
        referenced = it->referenced;
        pool_unlock();
        if (!referenced)
            talloc_free(img);
    }
    pool->num_images = 0;
}

// This is the only function that is allowed to run in a different thread.
// (Consider passing an image to another thread, which frees it.)
static void unref_image(void *ptr)
{
    struct mp_image *img = ptr;
    struct image_flags *it = img->priv;
    bool alive;
    pool_lock();
    assert(it->referenced);
    it->referenced = false;
    alive = it->pool_alive;
    pool_unlock();
    if (!alive)
        talloc_free(img);
}

// Return a new image of given format/size. Unlike mp_image_pool_get(), this
// returns NULL if there is no free image of this format/size.
struct mp_image *mp_image_pool_get_no_alloc(struct mp_image_pool *pool, int fmt,
                                            int w, int h)
{
    struct mp_image *new = NULL;
    pool_lock();
    for (int n = 0; n < pool->num_images; n++) {
        struct mp_image *img = pool->images[n];
        struct image_flags *img_it = img->priv;
        assert(img_it->pool_alive);
        if (!img_it->referenced) {
            if (img->imgfmt == fmt && img->w == w && img->h == h) {
                if (pool->use_lru) {
                    struct image_flags *new_it = new ? new->priv : NULL;
                    if (!new_it || new_it->order > img_it->order)
                        new = img;
                } else {
                    new = img;
                    break;
                }
            }
        }
    }
    pool_unlock();
    if (!new)
        return NULL;
    struct image_flags *it = new->priv;
    assert(!it->referenced && it->pool_alive);
    it->referenced = true;
    it->order = ++pool->lru_counter;
    return mp_image_new_custom_ref(new, new, unref_image);
}

// Return a new image of given format/size. The only difference to
// mp_image_alloc() is that there is a transparent mechanism to recycle image
// data allocations through this pool.
// If pool==NULL, mp_image_alloc() is called (for convenience).
// The image can be free'd with talloc_free().
// Returns NULL on OOM.
struct mp_image *mp_image_pool_get(struct mp_image_pool *pool, int fmt,
                                   int w, int h)
{
    if (!pool)
        return mp_image_alloc(fmt, w, h);
    struct mp_image *new = mp_image_pool_get_no_alloc(pool, fmt, w, h);
    if (!new) {
        if (pool->num_images >= pool->max_count)
            mp_image_pool_clear(pool);
        if (pool->allocator) {
            new = pool->allocator(pool->allocator_ctx, fmt, w, h);
        } else {
            new = mp_image_alloc(fmt, w, h);
        }
        if (!new)
            return NULL;
        struct image_flags *it = talloc_ptrtype(new, it);
        *it = (struct image_flags) { .pool_alive = true };
        new->priv = it;
        MP_TARRAY_APPEND(pool, pool->images, pool->num_images, new);
        new = mp_image_pool_get_no_alloc(pool, fmt, w, h);
    }
    return new;
}

// Like mp_image_new_copy(), but allocate the image out of the pool.
// If pool==NULL, a plain copy is made (for convenience).
// Returns NULL on OOM.
struct mp_image *mp_image_pool_new_copy(struct mp_image_pool *pool,
                                        struct mp_image *img)
{
    struct mp_image *new = mp_image_pool_get(pool, img->imgfmt, img->w, img->h);
    if (new) {
        mp_image_copy(new, img);
        mp_image_copy_attributes(new, img);
    }
    return new;
}

// Like mp_image_make_writeable(), but if a copy has to be made, allocate it
// out of the pool.
// If pool==NULL, mp_image_make_writeable() is called (for convenience).
// Returns false on failure (see mp_image_make_writeable()).
bool mp_image_pool_make_writeable(struct mp_image_pool *pool,
                                  struct mp_image *img)
{
    if (mp_image_is_writeable(img))
        return true;
    struct mp_image *new = mp_image_pool_new_copy(pool, img);
    if (!new)
        return false;
    mp_image_steal_data(img, new);
    assert(mp_image_is_writeable(img));
    return true;
}

void mp_image_pool_set_allocator(struct mp_image_pool *pool,
                                 mp_image_allocator cb, void  *cb_data)
{
    pool->allocator = cb;
    pool->allocator_ctx = cb_data;
}

// Put into LRU mode. (Likely better for hwaccel surfaces, but worse for memory.)
void mp_image_pool_set_lru(struct mp_image_pool *pool)
{
    pool->use_lru = true;
}