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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#pragma once
#include "freelist.h"
#include <climits>
namespace vespamalloc::segment {
template <int MaxCount>
FreeListT<MaxCount>::FreeListT(BlockT * blockList) :
_blockList(blockList),
_count(0)
{
for (size_t i = 0; i < NELEMS(_freeStartIndex); i++) {
_freeStartIndex[i] = -1;
}
}
template <int MaxCount>
FreeListT<MaxCount>::~FreeListT() = default;
template <int MaxCount>
void
FreeListT<MaxCount>::add(Index startIndex)
{
Index i(0);
Index numBlocks(_blockList[startIndex].freeChainLength());
for (i=0; (i < _count) && (_freeStartIndex[i] < startIndex); i++) { }
Index prevIndex(0), nextIndex(0);
BlockT * prev(nullptr), * next(nullptr);
if (i > 0) {
prevIndex = _freeStartIndex[i-1];
prev = & _blockList[prevIndex];
}
if (i < _count) {
nextIndex = _freeStartIndex[i];
next = & _blockList[nextIndex];
}
if (prev && (prevIndex + prev->freeChainLength() == startIndex)) {
// Join with freeChain ahead.
prev->freeChainLength(prev->freeChainLength() + numBlocks);
startIndex = prevIndex;
} else if (next && (startIndex + numBlocks == nextIndex)) {
// Join with freeChain that follows.
_freeStartIndex[i] = startIndex;
nextIndex = startIndex;
Index oldNextCount = next->freeChainLength();
next = & _blockList[startIndex];
next->freeChainLength(oldNextCount + numBlocks);
} else {
// Insert.
for(Index j=0; j < (_count-i); j++) {
_freeStartIndex[_count-j] = _freeStartIndex[_count-j-1];
}
_count++;
_freeStartIndex[i] = startIndex;
}
if (prev && next && (prevIndex + prev->freeChainLength() == nextIndex)) {
prev->freeChainLength(prev->freeChainLength() + next->freeChainLength());
_count--;
for(Index j=i; j < _count; j++) {
_freeStartIndex[j] = _freeStartIndex[j+1];
}
_freeStartIndex[_count] = -1;
}
}
template <int MaxCount>
void *
FreeListT<MaxCount>::sub(Index numBlocks)
{
void * block(nullptr);
size_t bestFitIndex(_count);
int bestLeft(INT_MAX);
for(size_t i=0; i < _count; i++) {
size_t index(_freeStartIndex[i]);
BlockT & b = _blockList[index];
int left = b.freeChainLength() - numBlocks;
if ((left >= 0) && (left < bestLeft)) {
bestLeft = left;
bestFitIndex = i;
}
}
if (bestLeft != INT_MAX) {
block = linkOut(bestFitIndex, bestLeft);
}
return block;
}
template <int MaxCount>
uint32_t
FreeListT<MaxCount>::lastBlock(Index nextBlock)
{
Index lastIndex(0);
if (_count > 0) {
Index index(_freeStartIndex[_count-1]);
BlockT & b = _blockList[index];
if (index + b.freeChainLength() == nextBlock) {
lastIndex = index;
}
}
return lastIndex;
}
template <int MaxCount>
void
FreeListT<MaxCount>::info(FILE * os)
{
for (Index i=0; i < _count; i++) {
Index index(_freeStartIndex[i]);
const BlockT & b = _blockList[index];
fprintf(os, "Free #%3d block #%5d chainlength %5d size %10lu\n",
i, index, b.freeChainLength(), b.freeChainLength()*BlockSize);
}
}
template <int MaxCount>
uint32_t
FreeListT<MaxCount>::numFreeBlocks() const
{
Index freeBlockCount(0);
for (Index i=0; i < _count; i++) {
Index index(_freeStartIndex[i]);
const BlockT & b = _blockList[index];
freeBlockCount += b.freeChainLength();
}
return freeBlockCount;
}
template <int MaxCount>
void *
FreeListT<MaxCount>::linkOut(Index findex, Index left)
{
size_t index(_freeStartIndex[findex]);
BlockT & b = _blockList[index];
Index startIndex = index + left;
void *block = fromBlockId(startIndex);
if (left > 0) {
b.freeChainLength(left);
} else {
_count--;
for(Index j=findex; j < (_count); j++) {
_freeStartIndex[j] = _freeStartIndex[j+1];
}
_freeStartIndex[_count] = -1;
}
return block;
}
}
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