libmicrohttpd2

commit ab052bb0724cf5fb4caa4ad6652ed5945e0ad55e
parent be38f8db9f360db676c2820a22f19e66ef662f5d
Author: Evgeny Grin (Karlson2k) <k2k@drgrin.dev>
Date:   Wed,  1 Oct 2025 23:25:03 +0200

h2_huffman_est.h: estimation for huffman compression

Diffstat:
A
src/mhd2/h2/hpack/h2_huffman_est.h
 | 
89
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 89 insertions(+), 0 deletions(-)
diff --git a/src/mhd2/h2/hpack/h2_huffman_est.h b/src/mhd2/h2/hpack/h2_huffman_est.h
@@ -0,0 +1,89 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later OR (GPL-2.0-or-later WITH eCos-exception-2.0) */
+/*
+  This file is part of GNU libmicrohttpd.
+  Copyright (C) 2025 Evgeny Grin (Karlson2k)
+
+  GNU libmicrohttpd is free software; you can redistribute it and/or
+  modify it under the terms of the GNU Lesser General Public
+  License as published by the Free Software Foundation; either
+  version 2.1 of the License, or (at your option) any later version.
+
+  GNU libmicrohttpd is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+  Lesser General Public License for more details.
+
+  Alternatively, you can redistribute GNU libmicrohttpd and/or
+  modify it under the terms of the GNU General Public License as
+  published by the Free Software Foundation; either version 2 of
+  the License, or (at your option) any later version, together
+  with the eCos exception, as follows:
+
+    As a special exception, if other files instantiate templates or
+    use macros or inline functions from this file, or you compile this
+    file and link it with other works to produce a work based on this
+    file, this file does not by itself cause the resulting work to be
+    covered by the GNU General Public License. However the source code
+    for this file must still be made available in accordance with
+    section (3) of the GNU General Public License v2.
+
+    This exception does not invalidate any other reasons why a work
+    based on this file might be covered by the GNU General Public
+    License.
+
+  You should have received copies of the GNU Lesser General Public
+  License and the GNU General Public License along with this library;
+  if not, see <https://www.gnu.org/licenses/>.
+*/
+
+/**
+ * @file src/mhd2/h2/hpack/h2_huffman_est.h
+ * @brief  HTTP/2 Huffman encoding size estimation functions
+ * @author Karlson2k (Evgeny Grin)
+ */
+
+#ifndef MHD_H2_HUFFMAN_EST_H
+#define MHD_H2_HUFFMAN_EST_H 1
+
+#include "mhd_sys_options.h"
+
+#include "sys_base_types.h"
+
+/**
+ * Estimate minimal possible size of H2 Huffman encoder output
+ * @param str_len the length of the original string to encode, must be
+ *                within 32 bit value
+ * @return the estimated minimal size of the encoded string; the real
+ *         encoded size is most probably larger
+ */
+mhd_static_inline uint_least32_t
+mhd_h2_huffman_est_min_size (uint_fast32_t str_len)
+{
+  const uint_fast64_t min_bits = ((uint_fast64_t) str_len) * 5u;
+  mhd_assert (str_len == (str_len & 0xFFFFFFFFu));
+
+  return (uint_least32_t) ((min_bits + 7u) / 8u);
+}
+
+
+/**
+ * Estimate average expected size of H2 Huffman encoder output
+ * @param str_len the length of the original string to encode, must be
+ *                within 32 bit value
+ * @return the estimated average size of the encoded string; the real
+ *         encoded size may be larger or smaller
+ */
+mhd_static_inline uint_least32_t
+mhd_h2_huffman_est_avg_size (uint_fast32_t str_len)
+{
+  uint_fast64_t est_bits;
+  mhd_assert (str_len == (str_len & 0xFFFFFFFFu));
+
+  /* Assume 6.5 bits per symbol in average */
+  est_bits = ((uint_fast64_t) str_len) * 6u;
+  est_bits += str_len / 2;
+  return (uint_least32_t) ((est_bits + 7u) / 8u);
+}
+
+
+#endif /* ! MHD_H2_HUFFMAN_EST_H */