h2_huffman_est.h (3304B)
1 /* SPDX-License-Identifier: LGPL-2.1-or-later OR (GPL-2.0-or-later WITH eCos-exception-2.0) */ 2 /* 3 This file is part of GNU libmicrohttpd. 4 Copyright (C) 2025 Evgeny Grin (Karlson2k) 5 6 GNU libmicrohttpd is free software; you can redistribute it and/or 7 modify it under the terms of the GNU Lesser General Public 8 License as published by the Free Software Foundation; either 9 version 2.1 of the License, or (at your option) any later version. 10 11 GNU libmicrohttpd is distributed in the hope that it will be useful, 12 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 Lesser General Public License for more details. 15 16 Alternatively, you can redistribute GNU libmicrohttpd and/or 17 modify it under the terms of the GNU General Public License as 18 published by the Free Software Foundation; either version 2 of 19 the License, or (at your option) any later version, together 20 with the eCos exception, as follows: 21 22 As a special exception, if other files instantiate templates or 23 use macros or inline functions from this file, or you compile this 24 file and link it with other works to produce a work based on this 25 file, this file does not by itself cause the resulting work to be 26 covered by the GNU General Public License. However the source code 27 for this file must still be made available in accordance with 28 section (3) of the GNU General Public License v2. 29 30 This exception does not invalidate any other reasons why a work 31 based on this file might be covered by the GNU General Public 32 License. 33 34 You should have received copies of the GNU Lesser General Public 35 License and the GNU General Public License along with this library; 36 if not, see <https://www.gnu.org/licenses/>. 37 */ 38 39 /** 40 * @file src/mhd2/h2/hpack/h2_huffman_est.h 41 * @brief HTTP/2 Huffman encoding size estimation functions 42 * @author Karlson2k (Evgeny Grin) 43 */ 44 45 #ifndef MHD_H2_HUFFMAN_EST_H 46 #define MHD_H2_HUFFMAN_EST_H 1 47 48 #include "mhd_sys_options.h" 49 50 #include "sys_base_types.h" 51 52 /** 53 * Estimate minimal possible size of H2 Huffman encoder output 54 * @param str_len the length of the original string to encode, must be 55 * within 32 bit value 56 * @return the estimated minimal size of the encoded string; the real 57 * encoded size is most probably larger 58 */ 59 mhd_static_inline uint_least32_t 60 mhd_h2_huffman_est_min_size (uint_fast32_t str_len) 61 { 62 const uint_fast64_t min_bits = ((uint_fast64_t) str_len) * 5u; 63 mhd_assert (str_len == (str_len & 0xFFFFFFFFu)); 64 65 return (uint_least32_t) ((min_bits + 7u) / 8u); 66 } 67 68 69 /** 70 * Estimate average expected size of H2 Huffman encoder output 71 * @param str_len the length of the original string to encode, must be 72 * within 32 bit value 73 * @return the estimated average size of the encoded string; the real 74 * encoded size may be larger or smaller 75 */ 76 mhd_static_inline uint_least32_t 77 mhd_h2_huffman_est_avg_size (uint_fast32_t str_len) 78 { 79 uint_fast64_t est_bits; 80 mhd_assert (str_len == (str_len & 0xFFFFFFFFu)); 81 82 /* Assume 6.5 bits per symbol in average */ 83 est_bits = ((uint_fast64_t) str_len) * 6u; 84 est_bits += str_len / 2; 85 return (uint_least32_t) ((est_bits + 7u) / 8u); 86 } 87 88 89 #endif /* ! MHD_H2_HUFFMAN_EST_H */