tec_nd_compress.hpp

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// Time-stamp: <Last changed 2026-02-11 16:47:05 by magnolia>
/*----------------------------------------------------------------------
------------------------------------------------------------------------
Copyright (c) 2020-2026 The Emacs Cat (https://github.com/olddeuteronomy/tec).
 
   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at
 
     http://www.apache.org/licenses/LICENSE-2.0
 
   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
------------------------------------------------------------------------
----------------------------------------------------------------------*/
 
#pragma once
 
#include <cerrno>
#include <cstddef>
 
#if defined (_TEC_USE_ZLIB)
#include <zlib.h>
// TEC library optionally uses the Zlib library (http://zlib.net).
// If used, Zlib is Copyright (C) 1995-2024 Jean-loup Gailly and Mark Adler.
#endif
 
#include "tec/tec_def.hpp"   // IWYU pragma: keep
#include "tec/tec_trace.hpp" // IWYU pragma: keep
#include "tec/tec_status.hpp"
#include "tec/net/tec_compression.hpp"
#include "tec/net/tec_net_data.hpp"
 
 
namespace tec {
 
class NdCompress {
protected:
    int type_; 
    int level_; 
    size_t min_size_; 
 
public:
    NdCompress()
        : type_{CompressionParams::kDefaultCompression}
        , level_{CompressionParams::kDefaultCompressionLevel}
        , min_size_{CompressionParams::kMinSize}
    {}
 
    explicit NdCompress(int _type,
                        int _level = CompressionParams::kDefaultCompressionLevel,
                        size_t _min_size = CompressionParams::kMinSize)
        : type_{_type}
        , level_{_level}
        , min_size_{_min_size}
    {}
 
    virtual Status compress(NetData& nd) const {
        TEC_ENTER("NdCompress::compress");
#if defined (ZLIB_VERSION)
        if (type_ == CompressionParams::kCompressionZlib) {
            TEC_TRACE("Type={} Level={} MinSize={}", type_, level_, min_size_);
            return compress_zlib(nd);
        }
#endif
        // No compression required.
        TEC_TRACE("OFF.");
        nd.header.set_compression(CompressionParams::kNoCompression);
        return {};
    }
 
    virtual Status uncompress(NetData& nd) const {
        TEC_ENTER("NdCompress::uncompress");
        int compression = nd.header.get_compression();
        nd.rewind();
        if (compression == CompressionParams::kNoCompression) {
            // Nothing to do.
            TEC_TRACE("OFF.");
            return {};
        }
#if defined (ZLIB_VERSION)
        if (compression == CompressionParams::kCompressionZlib) {
            return uncompress_zlib(nd);
        }
#endif
        return {ENOTSUP, Error::Kind::Unsupported};
    }
 
protected:
 
    /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     *
     *                        ZLIB compression
     *
     *~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
 
#if defined (ZLIB_VERSION)
 
    virtual Status compress_zlib(NetData& nd) const {
        TEC_ENTER("NdCompress::compress_zlib");
        if (nd.header.size < min_size_) {
            // Data too small -- no compression required.
            nd.header.set_compression(CompressionParams::kNoCompression);
            return {};
        }
        //
        // Calculate output size.
        //
        auto size_compressed = ::compressBound(nd.header.size);
        if (size_compressed == 0) {
            return{EINVAL, Error::Kind::RuntimeErr};
        }
        //
        // Prepare temp NetData.
        //
        NetData tmp;
        tmp.header = nd.header;
        tmp.header.size_uncompressed = nd.header.size;
        tmp.header.set_compression(type_);
        tmp.header.set_compression_level(level_);
        // Prepare output buffer.
        tmp.bytes().resize(size_compressed);
        //
        // Compressing.
        //
        TEC_TRACE("Compressing {} bytes...", nd.header.size);
        auto result = ::compress2(
            (Bytef*)tmp.bytes().ptr(0), &size_compressed,
            (const Bytef*)nd.bytes().ptr(0), nd.size(),
            level_);
        if (result != Z_OK) {
            return {EILSEQ, Error::Kind::RuntimeErr};
        }
        //
        // Update input NetData inplace.
        //
        tmp.header.size = size_compressed;
        nd.move_from(std::move(tmp), size_compressed);
        TEC_TRACE("Compressed to {} bytes with ratio {}.",
            size_compressed,
                  (double)nd.header.size_uncompressed / (double)nd.header.size);
        return {};
    }
 
    virtual Status uncompress_zlib(NetData& nd) const {
        TEC_ENTER("NdCompress::uncompress_zlib");
        if (nd.header.get_compression() == CompressionParams::kNoCompression) {
            // No uncompression required.
            return {};
        }
        //
        // Prepare temp NetData.
        //
        NetData tmp;
        tmp.header = nd.header;
        // Prepare output buffer.
        uLongf dest_len = nd.header.size_uncompressed;
        tmp.bytes().resize(dest_len);
        //
        // Uncompressing.
        //
        TEC_TRACE("Uncompressing {} bytes...", nd.size());
        auto result = ::uncompress(
            (Bytef*)tmp.data(), &dest_len,
            (const Bytef*)nd.data(), nd.size());
        if (result != Z_OK) {
            return {EILSEQ, Error::Kind::RuntimeErr};
        }
        //
        // Update input NetData inplace.
        //
        tmp.header.size = dest_len;
        tmp.header.size_uncompressed = 0;
        nd.move_from(std::move(tmp));
        TEC_TRACE("Upcompressed to {} bytes.", nd.size());
        return {};
    }
 
#endif // defined(ZLIB_VERSION)
};
 
} // namespace tec