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909af1a43b
Change multi's book keeping of transfers to no longer use lists, but a special table and bitsets for unsigned int values. `multi-xfers` is the `uint_tbl` where `multi_add_handle()` inserts a new transfer which assigns it a unique identifier `mid`. Use bitsets to keep track of transfers that are in state "process" or "pending" or "msgsent". Use sparse bitsets to replace `conn->easyq` and event handlings tracking of transfers per socket. Instead of pointers, keep the mids involved. Provide base data structures and document them in docs/internal: * `uint_tbl`: a table of transfers with `mid` as lookup key, handing out a mid for adds between 0 - capacity. * `uint_bset`: a bitset keeping unsigned ints from 0 - capacity. * `uint_spbset`: a sparse bitset for keeping a small number of unsigned int values * `uint_hash`: for associating `mid`s with a pointer. This makes the `mid` the recommended way to refer to transfers inside the same multi without risk of running into a UAF. Modifying table and bitsets is safe while iterating over them. Overall memory requirements are lower as with the double linked list apprach. Closes #16761
100 lines
3.7 KiB
C
100 lines
3.7 KiB
C
#ifndef HEADER_CURL_UINT_SPBSET_H
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#define HEADER_CURL_UINT_SPBSET_H
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/***************************************************************************
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* _ _ ____ _
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* Project ___| | | | _ \| |
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* / __| | | | |_) | |
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* | (__| |_| | _ <| |___
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* \___|\___/|_| \_\_____|
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*
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* Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
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*
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* This software is licensed as described in the file COPYING, which
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* you should have received as part of this distribution. The terms
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* are also available at https://curl.se/docs/copyright.html.
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*
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* You may opt to use, copy, modify, merge, publish, distribute and/or sell
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* copies of the Software, and permit persons to whom the Software is
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* furnished to do so, under the terms of the COPYING file.
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*
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* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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* KIND, either express or implied.
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*
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* SPDX-License-Identifier: curl
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*
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***************************************************************************/
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#include "curl_setup.h"
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#include <curl/curl.h>
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/* A "sparse" bitset for unsigned int values.
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* It can hold any unsigned int value.
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*
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* Optimized for the case where only a small set of numbers need
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* to be kept, especially when "close" together. Then storage space
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* is most efficient, deteriorating when many number are far apart.
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*/
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/* 4 slots = 256 bits, keep this a 2^n value. */
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#define CURL_UINT_SPBSET_CH_SLOTS 4
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#define CURL_UINT_SPBSET_CH_MASK ((CURL_UINT_SPBSET_CH_SLOTS * 64) - 1)
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/* store the uint value from offset to
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* (offset + (CURL_UINT_SPBSET_CHUNK_SLOTS * 64) - 1 */
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struct uint_spbset_chunk {
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struct uint_spbset_chunk *next;
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curl_uint64_t slots[CURL_UINT_SPBSET_CH_SLOTS];
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unsigned int offset;
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};
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struct uint_spbset {
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struct uint_spbset_chunk head;
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#ifdef DEBUGBUILD
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int init;
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#endif
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};
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void Curl_uint_spbset_init(struct uint_spbset *bset);
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void Curl_uint_spbset_destroy(struct uint_spbset *bset);
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/* Get the cardinality of the bitset, e.g. numbers present in the set. */
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unsigned int Curl_uint_spbset_count(struct uint_spbset *bset);
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/* TRUE of bitset is empty */
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bool Curl_uint_spbset_empty(struct uint_spbset *bset);
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/* Clear the bitset, making it empty. */
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void Curl_uint_spbset_clear(struct uint_spbset *bset);
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/* Add the number `i` to the bitset.
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* Numbers can be added more than once, without making a difference.
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* Returns FALSE if allocations failed. */
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bool Curl_uint_spbset_add(struct uint_spbset *bset, unsigned int i);
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/* Remove the number `i` from the bitset. */
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void Curl_uint_spbset_remove(struct uint_spbset *bset, unsigned int i);
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/* Return TRUE if the bitset contains number `i`. */
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bool Curl_uint_spbset_contains(struct uint_spbset *bset, unsigned int i);
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/* Get the first number in the bitset, e.g. the smallest.
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* Returns FALSE when the bitset is empty. */
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bool Curl_uint_spbset_first(struct uint_spbset *bset, unsigned int *pfirst);
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/* Get the next number in the bitset, following `last` in natural order.
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* Put another way, this is the smallest number greater than `last` in
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* the bitset. `last` does not have to be present in the set.
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*
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* Returns FALSE when no such number is in the set.
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*
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* This allows to iterate the set while being modified:
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* - added numbers higher than 'last' will be picked up by the iteration.
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* - added numbers lower than 'last' will not show up.
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* - removed numbers lower or equal to 'last' will not show up.
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* - removed numbers higher than 'last' will not be visited. */
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bool Curl_uint_spbset_next(struct uint_spbset *bset, unsigned int last,
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unsigned int *pnext);
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#endif /* HEADER_CURL_UINT_SPBSET_H */
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