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//
// Copyright (c) 2002-2011 The ANGLE Project Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//
// HandleAllocator.cpp: Implements the gl::HandleAllocator class, which is used
// to allocate GL handles.
#include "libANGLE/HandleAllocator.h"
#include <algorithm>
#include "common/debug.h"
namespace gl
{
struct HandleAllocator::HandleRangeComparator
{
bool operator()(const HandleRange &range, GLuint handle) const
{
return (range.end < handle);
}
};
HandleAllocator::HandleAllocator() : mBaseValue(1), mNextValue(1)
{
mUnallocatedList.push_back(HandleRange(1, std::numeric_limits<GLuint>::max()));
}
HandleAllocator::HandleAllocator(GLuint maximumHandleValue) : mBaseValue(1), mNextValue(1)
{
mUnallocatedList.push_back(HandleRange(1, maximumHandleValue));
}
HandleAllocator::~HandleAllocator()
{
}
void HandleAllocator::setBaseHandle(GLuint value)
{
ASSERT(mBaseValue == mNextValue);
mBaseValue = value;
mNextValue = value;
}
GLuint HandleAllocator::allocate()
{
ASSERT(!mUnallocatedList.empty() || !mReleasedList.empty());
// Allocate from released list, constant time.
if (!mReleasedList.empty())
{
GLuint reusedHandle = mReleasedList.back();
mReleasedList.pop_back();
return reusedHandle;
}
// Allocate from unallocated list, constant time.
auto listIt = mUnallocatedList.begin();
GLuint freeListHandle = listIt->begin;
ASSERT(freeListHandle > 0);
if (listIt->begin == listIt->end)
{
mUnallocatedList.erase(listIt);
}
else
{
listIt->begin++;
}
return freeListHandle;
}
void HandleAllocator::release(GLuint handle)
{
// Add to released list, constant time.
mReleasedList.push_back(handle);
}
void HandleAllocator::reserve(GLuint handle)
{
// Clear from released list -- might be a slow operation.
if (!mReleasedList.empty())
{
auto releasedIt = std::find(mReleasedList.begin(), mReleasedList.end(), handle);
if (releasedIt != mReleasedList.end())
{
mReleasedList.erase(releasedIt);
return;
}
}
// Not in released list, reserve in the unallocated list.
auto boundIt = std::lower_bound(mUnallocatedList.begin(), mUnallocatedList.end(), handle, HandleRangeComparator());
ASSERT(boundIt != mUnallocatedList.end());
GLuint begin = boundIt->begin;
GLuint end = boundIt->end;
if (handle == begin || handle == end)
{
if (begin == end)
{
mUnallocatedList.erase(boundIt);
}
else if (handle == begin)
{
boundIt->begin++;
}
else
{
ASSERT(handle == end);
boundIt->end--;
}
return;
}
ASSERT(begin < handle && handle < end);
// need to split the range
auto placementIt = mUnallocatedList.erase(boundIt);
placementIt = mUnallocatedList.insert(placementIt, HandleRange(handle + 1, end));
mUnallocatedList.insert(placementIt, HandleRange(begin, handle - 1));
}
} // namespace gl
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