test_history_snapshot.c

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/*
    This file is part of Ansel,
    Copyright (C) 2026 Aurélien PIERRE.
 
    Ansel 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.
 
    Ansel 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 Ansel.  If not, see <http://www.gnu.org/licenses/>.
*/
 
/* The contract between a history snapshot and the writer's copy-on-write gate.
 *
 * dt_dev_pixelpipe_change() resyncs a pipe against a dt_dev_history_snapshot_t with
 * history_mutex RELEASED. That is only sound if two things hold, and this file pins both:
 *
 *   1. the snapshot holds one reference per item, so nothing it walks can be freed under it;
 *   2. dt_dev_history_cow_touch() clones a shared item instead of mutating it in place, so
 *      nothing the snapshot walks can CHANGE under it either -- and the pipe's last-synced
 *      marker, which the GUI thread re-points at the clone, keeps every refcount balanced.
 *
 * A dt_develop_t is built by hand here: the functions under test touch dev->history,
 * dev->history_mutex, dev->pipe and dev->preview_pipe and nothing else, and dt_dev_init()
 * would drag the whole application in for no gain. */
 
#include "develop/develop.h"
#include "develop/dev_history.h"
#include "develop/pixelpipe_hb.h"
#include "system/atomic.h"
#include "system/dtpthread.h"
 
#include <glib.h>
#include <stdarg.h>
#include <stddef.h>
#include <stdlib.h>
// cmocka.h declares `extern jmp_buf global_expect_assert_env' at file scope without including
// <setjmp.h> itself. Same suppression as the other tests here, and for the same reason.
#include <setjmp.h>  // NOLINT(misc-include-cleaner)
#include <stdint.h>
#include <cmocka.h>
 
typedef struct _fixture_t
{
  dt_develop_t dev;
  dt_dev_pixelpipe_t pipe;
} _fixture_t;
 
static int _setup(void **state)
{
  _fixture_t *f = calloc(1, sizeof(_fixture_t));
  if(!f) return -1;
  dt_pthread_rwlock_init(&f->dev.history_mutex, NULL);
  f->dev.pipe = &f->pipe;
  f->dev.preview_pipe = NULL;
  *state = f;
  return 0;
}
 
static int _teardown(void **state)
{
  _fixture_t *f = *state;
  // Whatever a test left in the pipe's marker and in history is released here, so a test
  // that asserts on refcounts mid-way does not have to also be its own janitor.
  dt_dev_free_history_item(dt_atomic_exch_ptr(&f->pipe.last_history_item, NULL));
  g_list_free_full(f->dev.history, dt_dev_free_history_item);
  f->dev.history = NULL;
  dt_pthread_rwlock_destroy(&f->dev.history_mutex);
  free(f);
  return 0;
}
 
static int _refs(const dt_dev_history_item_t *item)
{
  return dt_atomic_get_int(&((dt_dev_history_item_t *)item)->refcount);
}
 
static dt_dev_history_item_t *_append(dt_develop_t *dev, const uint64_t hash)
{
  dt_dev_history_item_t *item = dt_dev_history_item_create();
  assert_non_null(item);
  item->hash = hash;
  dev->history = g_list_append(dev->history, item);
  item->num = g_list_index(dev->history, item);
  return item;
}
 
static void _a_snapshot_references_every_item_and_releases_them(void **state)
{
  _fixture_t *f = *state;
  dt_dev_history_item_t *a = _append(&f->dev, 0xA);
  dt_dev_history_item_t *b = _append(&f->dev, 0xB);
  dt_dev_history_item_t *c = _append(&f->dev, 0xC);
  f->dev.history_end = 3;
  dt_dev_set_history_hash(&f->dev, 0xABC);
 
  dt_dev_history_snapshot_t snap;
  dt_pthread_rwlock_rdlock(&f->dev.history_mutex);
  dt_dev_history_snapshot_take(&f->dev, &snap);
  dt_pthread_rwlock_unlock(&f->dev.history_mutex);
 
  // Same items, same order, one extra reference each. No copy: the pointers are identical.
  assert_int_equal(g_list_length(snap.items), 3);
  assert_ptr_equal(g_list_nth_data(snap.items, 0), a);
  assert_ptr_equal(g_list_nth_data(snap.items, 1), b);
  assert_ptr_equal(g_list_nth_data(snap.items, 2), c);
  assert_int_equal(_refs(a), 2);
  assert_int_equal(_refs(b), 2);
  assert_int_equal(_refs(c), 2);
 
  // end and hash travel with the list.
  assert_int_equal(snap.history_end, 3);
  assert_int_equal(snap.history_hash, 0xABC);
 
  dt_dev_history_snapshot_release(&snap);
  assert_null(snap.items);
  assert_int_equal(_refs(a), 1);
  assert_int_equal(_refs(b), 1);
  assert_int_equal(_refs(c), 1);
}
 
static void _history_end_is_clamped_to_the_list_at_snapshot_time(void **state)
{
  _fixture_t *f = *state;
  _append(&f->dev, 0x1);
  _append(&f->dev, 0x2);
  f->dev.history_end = 99; // stale, larger than the list
 
  dt_dev_history_snapshot_t snap;
  dt_pthread_rwlock_rdlock(&f->dev.history_mutex);
  dt_dev_history_snapshot_take(&f->dev, &snap);
  dt_pthread_rwlock_unlock(&f->dev.history_mutex);
 
  assert_int_equal(snap.history_end, 2);
  dt_dev_history_snapshot_release(&snap);
}
 
static void _cow_touch_leaves_an_exclusively_owned_item_alone(void **state)
{
  _fixture_t *f = *state;
  dt_dev_history_item_t *item = _append(&f->dev, 0x1);
  assert_int_equal(_refs(item), 1);
 
  dt_dev_history_item_t *touched = dt_dev_history_cow_touch(&f->dev, item);
 
  // Nobody else can see it: mutate in place, no clone, no churn.
  assert_ptr_equal(touched, item);
  assert_int_equal(_refs(item), 1);
  assert_ptr_equal(g_list_nth_data(f->dev.history, 0), item);
}
 
static void _cow_touch_clones_an_item_a_snapshot_is_holding(void **state)
{
  _fixture_t *f = *state;
  dt_dev_history_item_t *original = _append(&f->dev, 0x1);
  original->enabled = TRUE;
  f->dev.history_end = 1;
 
  dt_dev_history_snapshot_t snap;
  dt_pthread_rwlock_rdlock(&f->dev.history_mutex);
  dt_dev_history_snapshot_take(&f->dev, &snap);
  dt_pthread_rwlock_unlock(&f->dev.history_mutex);
  assert_int_equal(_refs(original), 2);
 
  dt_dev_history_item_t *clone = dt_dev_history_cow_touch(&f->dev, original);
 
  // The writer got a fresh object and dev->history now names it ...
  assert_non_null(clone);
  assert_ptr_not_equal(clone, original);
  assert_ptr_equal(g_list_nth_data(f->dev.history, 0), clone);
  assert_int_equal(_refs(clone), 1);
  assert_int_equal(clone->hash, original->hash);
  assert_true(clone->enabled);
 
  // ... while the snapshot still names the original, which it alone now keeps alive.
  assert_ptr_equal(g_list_nth_data(snap.items, 0), original);
  assert_int_equal(_refs(original), 1);
 
  // A mutation of the clone is invisible through the snapshot -- the whole point.
  clone->enabled = FALSE;
  clone->hash = 0x2;
  assert_true(((dt_dev_history_item_t *)g_list_nth_data(snap.items, 0))->enabled);
  assert_int_equal(((dt_dev_history_item_t *)g_list_nth_data(snap.items, 0))->hash, 0x1);
 
  dt_dev_history_snapshot_release(&snap); // drops the original's last reference
}
 
static void _cow_touch_repoints_the_pipe_marker_and_balances_every_reference(void **state)
{
  _fixture_t *f = *state;
  dt_dev_history_item_t *original = _append(&f->dev, 0x1);
  f->dev.history_end = 1;
 
  // The pipe recorded this item as its last-synced marker, holding a reference on it, the
  // way _pipe_set_last_history_item() does at the end of a resync.
  dt_dev_history_item_ref(original);
  dt_atomic_set_ptr(&f->pipe.last_history_item, original);
  assert_int_equal(_refs(original), 2); // history + pipe
 
  dt_dev_history_snapshot_t snap;
  dt_pthread_rwlock_rdlock(&f->dev.history_mutex);
  dt_dev_history_snapshot_take(&f->dev, &snap);
  dt_pthread_rwlock_unlock(&f->dev.history_mutex);
  assert_int_equal(_refs(original), 3); // history + pipe + snapshot
 
  dt_dev_history_item_t *clone = dt_dev_history_cow_touch(&f->dev, original);
  assert_ptr_not_equal(clone, original);
 
  // The marker followed the clone, so an in-place top-entry rewrite keeps its bounded resync;
  // the reference the marker held on the original moved with it.
  assert_ptr_equal(dt_atomic_get_ptr(&f->pipe.last_history_item), clone);
  assert_int_equal(_refs(clone), 2);    // history + pipe
  assert_int_equal(_refs(original), 1); // snapshot only
 
  dt_dev_history_snapshot_release(&snap);
 
  // Dropping the pipe's marker the way dt_dev_pixelpipe_cleanup() does leaves the clone
  // owned by history alone: nothing leaked, nothing double-released.
  dt_dev_free_history_item(dt_atomic_exch_ptr(&f->pipe.last_history_item, NULL));
  assert_int_equal(_refs(clone), 1);
}
 
static void _cow_touch_ignores_a_marker_naming_a_different_item(void **state)
{
  _fixture_t *f = *state;
  dt_dev_history_item_t *first = _append(&f->dev, 0x1);
  dt_dev_history_item_t *second = _append(&f->dev, 0x2);
  f->dev.history_end = 2;
 
  dt_dev_history_item_ref(first);
  dt_atomic_set_ptr(&f->pipe.last_history_item, first);
 
  dt_dev_history_snapshot_t snap;
  dt_pthread_rwlock_rdlock(&f->dev.history_mutex);
  dt_dev_history_snapshot_take(&f->dev, &snap);
  dt_pthread_rwlock_unlock(&f->dev.history_mutex);
 
  dt_dev_history_item_t *clone = dt_dev_history_cow_touch(&f->dev, second);
  assert_ptr_not_equal(clone, second);
 
  // The marker named `first', not the item being cloned: it must not move.
  assert_ptr_equal(dt_atomic_get_ptr(&f->pipe.last_history_item), first);
  assert_int_equal(_refs(first), 3);  // history + pipe + snapshot
  assert_int_equal(_refs(clone), 1);  // history
  assert_int_equal(_refs(second), 1); // snapshot
 
  dt_dev_history_snapshot_release(&snap);
}
 
int main(void)
{
  const struct CMUnitTest tests[] = {
    cmocka_unit_test_setup_teardown(_a_snapshot_references_every_item_and_releases_them, _setup, _teardown),
    cmocka_unit_test_setup_teardown(_history_end_is_clamped_to_the_list_at_snapshot_time, _setup, _teardown),
    cmocka_unit_test_setup_teardown(_cow_touch_leaves_an_exclusively_owned_item_alone, _setup, _teardown),
    cmocka_unit_test_setup_teardown(_cow_touch_clones_an_item_a_snapshot_is_holding, _setup, _teardown),
    cmocka_unit_test_setup_teardown(_cow_touch_repoints_the_pipe_marker_and_balances_every_reference, _setup, _teardown),
    cmocka_unit_test_setup_teardown(_cow_touch_ignores_a_marker_naming_a_different_item, _setup, _teardown),
  };
 
  return cmocka_run_group_tests(tests, NULL, NULL);
}
 
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