gpu/command_buffer/common/id_allocator.cc

   1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 // This file contains the implementation of IdAllocator.
   6
   7 #include "gpu/command_buffer/common/id_allocator.h"
   8
   9 #include "base/logging.h"
  10
  11 namespace gpu {
  12
  13 IdAllocator::IdAllocator() {}
  14
  15 IdAllocator::~IdAllocator() {}
  16
  17 ResourceId IdAllocator::AllocateID() {
  18   ResourceId id;
  19   ResourceIdSet::iterator iter = free_ids_.begin();
  20   if (iter != free_ids_.end()) {
  21     id = *iter;
  22   } else {
  23     id = LastUsedId() + 1;
  24     if (!id) {
  25       // We wrapped around to 0.
  26       id = FindFirstUnusedId();
  27     }
  28   }
  29   MarkAsUsed(id);
  30   return id;
  31 }
  32
  33 ResourceId IdAllocator::AllocateIDAtOrAbove(ResourceId desired_id) {
  34   ResourceId id;
  35   ResourceIdSet::iterator iter = free_ids_.lower_bound(desired_id);
  36   if (iter != free_ids_.end()) {
  37     id = *iter;
  38   } else if (LastUsedId() < desired_id) {
  39     id = desired_id;
  40   } else {
  41     id = LastUsedId() + 1;
  42     if (!id) {
  43       // We wrapped around to 0.
  44       id = FindFirstUnusedId();
  45     }
  46   }
  47   MarkAsUsed(id);
  48   return id;
  49 }
  50
  51 bool IdAllocator::MarkAsUsed(ResourceId id) {
  52   DCHECK(id);
  53   free_ids_.erase(id);
  54   std::pair<ResourceIdSet::iterator, bool> result = used_ids_.insert(id);
  55   return result.second;
  56 }
  57
  58 void IdAllocator::FreeID(ResourceId id) {
  59   if (id) {
  60     used_ids_.erase(id);
  61     free_ids_.insert(id);
  62   }
  63 }
  64
  65 bool IdAllocator::InUse(ResourceId id) const {
  66   return id == kInvalidResource || used_ids_.find(id) != used_ids_.end();
  67 }
  68
  69 ResourceId IdAllocator::LastUsedId() const {
  70   if (used_ids_.empty()) {
  71     return 0u;
  72   } else {
  73     return *used_ids_.rbegin();
  74   }
  75 }
  76
  77 ResourceId IdAllocator::FindFirstUnusedId() const {
  78   ResourceId id = 1;
  79   for (ResourceIdSet::const_iterator it = used_ids_.begin();
  80        it != used_ids_.end(); ++it) {
  81     if ((*it) != id) {
  82       return id;
  83     }
  84     ++id;
  85   }
  86   return id;
  87 }
  88
  89 }  // namespace gpu