109 lines
3.3 KiB
C++
109 lines
3.3 KiB
C++
// Licensed to the Apache Software Foundation (ASF) under one
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// or more contributor license agreements. See the NOTICE file
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// distributed with this work for additional information
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// regarding copyright ownership. The ASF licenses this file
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// to you under the Apache License, Version 2.0 (the
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// "License"); you may not use this file except in compliance
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// with the License. You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing,
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// software distributed under the License is distributed on an
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// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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// KIND, either express or implied. See the License for the
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// specific language governing permissions and limitations
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// under the License.
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#ifndef DORIS_BE_SRC_QUERY_BE_RUNTIME_FREE_LIST_H
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#define DORIS_BE_SRC_QUERY_BE_RUNTIME_FREE_LIST_H
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#include <stdio.h>
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#include <string.h>
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#include <algorithm>
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#include <vector>
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#include <string>
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#include "common/logging.h"
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namespace doris {
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// Implementation of a free list:
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// The free list is made up of nodes which contain a pointer to the next node
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// and the size of the block. The free list does not allocate any memory and instead
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// overlays the node data over the caller-provided memory.
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//
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// Since the free list does not allocate or acquire any allocations, it needs to have
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// the same lifetime as whereever the allocations came from (i.e MemPool). If, for
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// example, the underlying MemPool is deallocated, if there are any blocks in the
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// free list from that pool, the free list is corrupt.
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class FreeList {
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public:
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// Returns the minimum allocation size that is compatible with
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// the free list. The free list uses the allocations to maintain
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// its own internal linked list structure.
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static int min_size() {
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return sizeof(FreeListNode);
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}
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// C'tor, initializes the free list to be empty
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FreeList() {
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reset();
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}
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// Attempts to allocate a block that is at least the input size
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// from the free list.
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// Returns the size of the entire buffer in *buffer_size.
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// Returns NULL if there is no matching free list size.
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uint8_t* allocate(int size, int* buffer_size) {
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DCHECK(buffer_size != NULL);
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FreeListNode* prev = &_head;
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FreeListNode* node = _head.next;
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while (node != NULL) {
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if (node->size >= size) {
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prev->next = node->next;
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*buffer_size = node->size;
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return reinterpret_cast<uint8_t*>(node);
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}
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prev = node;
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node = node->next;
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}
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*buffer_size = 0;
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return NULL;
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}
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// add a block to the free list. The caller can no longer touch
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// the memory. If the size is too small, the free list ignores
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// the memory.
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void add(uint8_t* memory, int size) {
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if (size < FreeList::min_size()) {
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return;
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}
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FreeListNode* node = reinterpret_cast<FreeListNode*>(memory);
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node->next = _head.next;
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node->size = size;
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_head.next = node;
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}
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// Empties the free list
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void reset() {
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bzero(&_head, sizeof(FreeListNode));
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}
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private:
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struct FreeListNode {
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FreeListNode* next;
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int size;
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};
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FreeListNode _head;
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};
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}
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#endif
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