mirror of
https://github.com/curl/curl.git
synced 2026-04-14 22:11:45 +03:00
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
238 lines
6.4 KiB
C
238 lines
6.4 KiB
C
/***************************************************************************
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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 "uint-bset.h"
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/* The last 3 #include files should be in this order */
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#include "curl_printf.h"
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#include "curl_memory.h"
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#include "memdebug.h"
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#ifdef DEBUGBUILD
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#define CURL_UINT_BSET_MAGIC 0x62757473
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#endif
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void Curl_uint_bset_init(struct uint_bset *bset)
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{
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memset(bset, 0, sizeof(*bset));
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#ifdef DEBUGBUILD
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bset->init = CURL_UINT_BSET_MAGIC;
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#endif
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}
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CURLcode Curl_uint_bset_resize(struct uint_bset *bset, unsigned int nmax)
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{
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unsigned int nslots = (nmax + 63) / 64;
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DEBUGASSERT(bset->init == CURL_UINT_BSET_MAGIC);
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if(nslots != bset->nslots) {
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curl_uint64_t *slots = calloc(nslots, sizeof(curl_uint64_t));
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if(!slots)
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return CURLE_OUT_OF_MEMORY;
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if(bset->slots) {
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memcpy(slots, bset->slots,
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(CURLMIN(nslots, bset->nslots) * sizeof(curl_uint64_t)));
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free(bset->slots);
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}
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bset->slots = slots;
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bset->nslots = nslots;
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}
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return CURLE_OK;
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}
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void Curl_uint_bset_destroy(struct uint_bset *bset)
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{
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DEBUGASSERT(bset->init == CURL_UINT_BSET_MAGIC);
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free(bset->slots);
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memset(bset, 0, sizeof(*bset));
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}
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unsigned int Curl_uint_bset_capacity(struct uint_bset *bset)
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{
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return bset->nslots * 64;
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}
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unsigned int Curl_uint_bset_count(struct uint_bset *bset)
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{
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unsigned int i;
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unsigned int n = 0;
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for(i = 0; i < bset->nslots; ++i) {
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if(bset->slots[i])
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n += CURL_POPCOUNT64(bset->slots[i]);
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}
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return n;
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}
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bool Curl_uint_bset_empty(struct uint_bset *bset)
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{
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unsigned int i;
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for(i = 0; i < bset->nslots; ++i) {
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if(bset->slots[i])
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return FALSE;
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}
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return TRUE;
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}
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void Curl_uint_bset_clear(struct uint_bset *bset)
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{
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if(bset->nslots)
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memset(bset->slots, 0, bset->nslots * sizeof(curl_uint64_t));
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}
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bool Curl_uint_bset_add(struct uint_bset *bset, unsigned int i)
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{
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unsigned int islot = i / 64;
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if(islot >= bset->nslots)
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return FALSE;
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bset->slots[islot] |= ((curl_uint64_t)1 << (i % 64));
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return TRUE;
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}
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void Curl_uint_bset_remove(struct uint_bset *bset, unsigned int i)
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{
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size_t islot = i / 64;
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if(islot < bset->nslots)
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bset->slots[islot] &= ~((curl_uint64_t)1 << (i % 64));
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}
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bool Curl_uint_bset_contains(struct uint_bset *bset, unsigned int i)
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{
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unsigned int islot = i / 64;
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if(islot >= bset->nslots)
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return FALSE;
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return (bset->slots[islot] & ((curl_uint64_t)1 << (i % 64))) != 0;
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}
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bool Curl_uint_bset_first(struct uint_bset *bset, unsigned int *pfirst)
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{
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unsigned int i;
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for(i = 0; i < bset->nslots; ++i) {
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if(bset->slots[i]) {
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*pfirst = (i * 64) + CURL_CTZ64(bset->slots[i]);
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return TRUE;
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}
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}
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*pfirst = UINT_MAX; /* a value we cannot store */
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return FALSE;
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}
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bool Curl_uint_bset_next(struct uint_bset *bset, unsigned int last,
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unsigned int *pnext)
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{
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unsigned int islot;
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curl_uint64_t x;
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++last; /* look for number one higher than last */
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islot = last / 64; /* the slot this would be in */
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if(islot < bset->nslots) {
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/* shift away the bits we already iterated in this slot */
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x = (bset->slots[islot] >> (last % 64));
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if(x) {
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/* more bits set, next is `last` + trailing0s of the shifted slot */
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*pnext = last + CURL_CTZ64(x);
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return TRUE;
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}
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/* no more bits set in the last slot, scan forward */
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for(islot = islot + 1; islot < bset->nslots; ++islot) {
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if(bset->slots[islot]) {
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*pnext = (islot * 64) + CURL_CTZ64(bset->slots[islot]);
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return TRUE;
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}
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}
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}
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*pnext = UINT_MAX; /* a value we cannot store */
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return FALSE;
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}
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#ifdef CURL_POPCOUNT64_IMPLEMENT
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unsigned int Curl_popcount64(curl_uint64_t x)
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{
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/* Compute the "Hamming Distance" between 'x' and 0,
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* which is the number of set bits in 'x'.
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* See: https://en.wikipedia.org/wiki/Hamming_weight */
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const curl_uint64_t m1 = CURL_OFF_TU_C(0x5555555555555555); /* 0101+ */
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const curl_uint64_t m2 = CURL_OFF_TU_C(0x3333333333333333); /* 00110011+ */
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const curl_uint64_t m4 = CURL_OFF_TU_C(0x0f0f0f0f0f0f0f0f); /* 00001111+ */
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/* 1 + 256^1 + 256^2 + 256^3 + ... + 256^7 */
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const curl_uint64_t h01 = CURL_OFF_TU_C(0x0101010101010101);
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x -= (x >> 1) & m1; /* replace every 2 bits with bits present */
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x = (x & m2) + ((x >> 2) & m2); /* replace every nibble with bits present */
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x = (x + (x >> 4)) & m4; /* replace every byte with bits present */
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/* top 8 bits of x + (x<<8) + (x<<16) + (x<<24) + ... which makes the
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* top byte the sum of all individual 8 bytes, throw away the rest */
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return (unsigned int)((x * h01) >> 56);
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}
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#endif /* CURL_POPCOUNT64_IMPLEMENT */
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#ifdef CURL_CTZ64_IMPLEMENT
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unsigned int Curl_ctz64(curl_uint64_t x)
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{
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/* count trailing zeros in a curl_uint64_t.
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* divide and conquer to find the number of lower 0 bits */
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const curl_uint64_t ml32 = CURL_OFF_TU_C(0xFFFFFFFF); /* lower 32 bits */
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const curl_uint64_t ml16 = CURL_OFF_TU_C(0x0000FFFF); /* lower 16 bits */
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const curl_uint64_t ml8 = CURL_OFF_TU_C(0x000000FF); /* lower 8 bits */
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const curl_uint64_t ml4 = CURL_OFF_TU_C(0x0000000F); /* lower 4 bits */
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const curl_uint64_t ml2 = CURL_OFF_TU_C(0x00000003); /* lower 2 bits */
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unsigned int n;
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if(!x)
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return 64;
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n = 1;
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if(!(x & ml32)) {
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n = n + 32;
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x = x >> 32;
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}
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if(!(x & ml16)) {
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n = n + 16;
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x = x >> 16;
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}
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if(!(x & ml8)) {
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n = n + 8;
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x = x >> 8;
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}
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if(!(x & ml4)) {
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n = n + 4;
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x = x >> 4;
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}
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if(!(x & ml2)) {
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n = n + 2;
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x = x >> 2;
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}
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return n - (unsigned int)(x & 1);
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}
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#endif /* CURL_CTZ64_IMPLEMENT */
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