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// Copyright 2017 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "ui/accessibility/platform/ax_unique_id.h"
#include "base/check_op.h"
#include "base/containers/contains.h"
#include "base/no_destructor.h"
#include "third_party/abseil-cpp/absl/container/flat_hash_set.h"
namespace ui {
namespace {
// Returns the container of assigned IDs.
absl::flat_hash_set<AXPlatformNodeId>& GetAssignedIds() {
static base::NoDestructor<absl::flat_hash_set<AXPlatformNodeId>> assigned_ids;
return *assigned_ids;
}
} // namespace
AXUniqueId::~AXUniqueId() {
if (id_ != AXPlatformNodeId()) {
GetAssignedIds().erase(id_);
}
}
// static
AXPlatformNodeId AXUniqueId::GetNextAXUniqueId(int32_t max_id) {
static int32_t current_id = 0;
static bool has_wrapped = false;
auto& assigned_ids = GetAssignedIds();
const int32_t prev_id = current_id;
do {
if (current_id >= max_id) {
current_id = 1;
has_wrapped = true;
} else {
++current_id;
}
CHECK_NE(current_id, prev_id)
<< "There are over 2 billion available IDs, so the newly created ID "
"cannot be equal to the most recently created ID.";
// If it |has_wrapped| then we need to continue until we find the first
// unassigned ID.
} while (has_wrapped &&
base::Contains(assigned_ids, AXPlatformNodeId(current_id)));
assigned_ids.insert(AXPlatformNodeId(current_id));
return AXPlatformNodeId(current_id);
}
} // namespace ui
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