httpcompression.h

/*******************************************************************************
Copyright (c) 2026, Jan Koester jan.koester@gmx.net
All rights reserved.
 
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.
    * Neither the name of the <organization> nor the
      names of its contributors may be used to endorse or promote products
      derived from this software without specific prior written permission.
 
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*******************************************************************************/
 
#pragma once
 
#include <string>
#include <vector>
 
namespace libhttppp {
namespace compression {
 
// None: no encoding (or "identity") -- send as-is.
// Gzip/Brotli: an encoding this module can itself produce and consume.
// Other: some encoding present that isn't gzip or brotli (e.g. "deflate", "zstd", or a
// comma-joined list) -- opaque to this module, callers must leave the body untouched.
enum class Encoding { None, Gzip, Brotli, Other };
 
// Maps a single Content-Encoding token (case-insensitive) to Encoding.
Encoding fromToken(const std::string &contentEncoding);
 
// Content-Encoding token this module would send for enc ("gzip"/"br"). Only valid for
// Gzip/Brotli.
const char *toToken(Encoding enc);
 
// Picks the best encoding this module can produce for a client's Accept-Encoding header,
// honoring q-values (q=0 excludes) and "*" per RFC 7231 §5.3.4. Prefers Brotli over gzip
// when both are acceptable with equal preference (better ratio at comparable CPU cost).
// Returns Encoding::None if the header is empty/absent or nothing acceptable remains.
Encoding negotiate(const std::string &acceptEncoding);
 
// True if the client's Accept-Encoding header declares enc acceptable at all (q>0, via an
// explicit token or "*"), independent of whether it's negotiate()'s top pick. Only meaningful
// for Encoding::Gzip/Brotli -- always false otherwise. Use this before forwarding a response
// in an encoding other than what negotiate() picked (e.g. a decode-and-transcode fallback):
// negotiate() returning a different encoding only means enc wasn't the *preferred* one, not
// that the client can't decode it at all.
bool accepts(const std::string &acceptEncoding, Encoding enc);
 
// True if contentType (as returned by HttpResponse::getContentType() -- already lowercased,
// parameters stripped) is worth spending CPU to compress. Binary/already-compressed formats
// (images, video, archives) are excluded.
bool isCompressible(const std::string &contentType);
 
bool gzipCompress(const std::vector<char> &in, std::vector<char> &out, int level = 6);
bool gzipDecompress(const std::vector<char> &in, std::vector<char> &out);
 
bool brotliCompress(const std::vector<char> &in, std::vector<char> &out, int quality = 5);
bool brotliDecompress(const std::vector<char> &in, std::vector<char> &out);
 
} // namespace compression
} // namespace libhttppp