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// Copyright 2011 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// This file contains the implementation of IdAllocator.
#include "gpu/command_buffer/common/id_allocator.h"
#include <stdint.h>
#include <limits>
#include "base/check.h"
namespace gpu {
IdAllocator::IdAllocator() {
static_assert(kInvalidResource == 0u, "kInvalidResource must be 0");
// Simplify the code by making sure that lower_bound(id) never
// returns the beginning of the map, if id is valid (eg !=
// kInvalidResource).
used_ids_.insert(std::make_pair(0u, 0u));
}
IdAllocator::~IdAllocator() = default;
ResourceId IdAllocator::AllocateID() {
return AllocateIDRange(1u);
}
ResourceId IdAllocator::AllocateIDAtOrAbove(ResourceId desired_id) {
if (desired_id == 0u || desired_id == 1u) {
return AllocateIDRange(1u);
}
ResourceIdRangeMap::iterator current = used_ids_.lower_bound(desired_id);
ResourceIdRangeMap::iterator next = current;
if (current == used_ids_.end() || current->first > desired_id) {
current--;
} else {
next++;
}
ResourceId first_id = current->first;
ResourceId last_id = current->second;
DCHECK(desired_id >= first_id);
if (desired_id - 1u <= last_id) {
// Append to current range.
last_id++;
if (last_id == 0) {
// The increment overflowed.
return AllocateIDRange(1u);
}
current->second = last_id;
if (next != used_ids_.end() && next->first - 1u == last_id) {
// Merge with next range.
current->second = next->second;
used_ids_.erase(next);
}
return last_id;
} else if (next != used_ids_.end() && next->first - 1u == desired_id) {
// Prepend to next range.
ResourceId last_existing_id = next->second;
used_ids_.erase(next);
used_ids_.insert(std::make_pair(desired_id, last_existing_id));
return desired_id;
}
used_ids_.insert(std::make_pair(desired_id, desired_id));
return desired_id;
}
ResourceId IdAllocator::AllocateIDRange(uint32_t range) {
DCHECK(range > 0u);
ResourceIdRangeMap::iterator current = used_ids_.begin();
ResourceIdRangeMap::iterator next = current;
while (++next != used_ids_.end()) {
if (next->first - current->second > range) {
break;
}
current = next;
}
ResourceId first_id = current->second + 1u;
ResourceId last_id = first_id + range - 1u;
if (first_id == 0u || last_id < first_id) {
return kInvalidResource;
}
current->second = last_id;
if (next != used_ids_.end() && next->first - 1u == last_id) {
// Merge with next range.
current->second = next->second;
used_ids_.erase(next);
}
return first_id;
}
bool IdAllocator::MarkAsUsed(ResourceId id) {
DCHECK(id);
ResourceIdRangeMap::iterator current = used_ids_.lower_bound(id);
if (current != used_ids_.end() && current->first == id) {
return false;
}
ResourceIdRangeMap::iterator next = current;
--current;
if (current->second >= id) {
return false;
}
DCHECK(current->first < id && current->second < id);
if (current->second + 1u == id) {
// Append to current range.
current->second = id;
if (next != used_ids_.end() && next->first - 1u == id) {
// Merge with next range.
current->second = next->second;
used_ids_.erase(next);
}
return true;
} else if (next != used_ids_.end() && next->first - 1u == id) {
// Prepend to next range.
ResourceId last_existing_id = next->second;
used_ids_.erase(next);
used_ids_.insert(std::make_pair(id, last_existing_id));
return true;
}
used_ids_.insert(std::make_pair(id, id));
return true;
}
void IdAllocator::FreeID(ResourceId id) {
FreeIDRange(id, 1u);
}
void IdAllocator::FreeIDRange(ResourceId first_id, uint32_t range) {
static_assert(kInvalidResource == 0u, "kInvalidResource must be 0");
if (range == 0u || (first_id == 0u && range == 1u)) {
return;
}
if (first_id == 0u) {
first_id++;
range--;
}
ResourceId last_id = first_id + range - 1u;
if (last_id < first_id) {
last_id = std::numeric_limits<ResourceId>::max();
}
while (true) {
ResourceIdRangeMap::iterator current = used_ids_.lower_bound(last_id);
if (current == used_ids_.end() || current->first > last_id) {
--current;
}
if (current->second < first_id) {
return;
}
if (current->first >= first_id) {
ResourceId last_existing_id = current->second;
used_ids_.erase(current);
if (last_id < last_existing_id) {
used_ids_.insert(std::make_pair(last_id + 1u, last_existing_id));
}
} else if (current->second <= last_id) {
current->second = first_id - 1u;
} else {
DCHECK(current->first < first_id && current->second > last_id);
ResourceId last_existing_id = current->second;
current->second = first_id - 1u;
used_ids_.insert(std::make_pair(last_id + 1u, last_existing_id));
}
}
}
bool IdAllocator::InUse(ResourceId id) const {
if (id == kInvalidResource) {
return false;
}
ResourceIdRangeMap::const_iterator current = used_ids_.lower_bound(id);
if (current != used_ids_.end()) {
if (current->first == id) {
return true;
}
}
--current;
return current->second >= id;
}
} // namespace gpu
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