netplay: introduce ICompressionAdapter facility for dealing with co…

…mpression

The patch provides:
* Base `ICompressionAdapter` interface for compression utilities
  to be used in the networking code
* `ZlibCompressionAdapter` implementation, which handles the existing
  zlib compression logic.

`tcp::Socket` now uses `ZlibCompressionAdapter` directly, which would
later be helpful in isolating and extracting more low-level stuff
(`readNoInt`, `writeAll`, `flush`) into a higher level of abstraction
(`IClientConnection` and pending writes manager).

Signed-off-by: Pavel Solodovnikov <pavel.al.solodovnikov@gmail.com>

lib/netplay/compression_adapter.h

@@ -0,0 +1,140 @@
+/*
+	This file is part of Warzone 2100.
+	Copyright (C) 2025  Warzone 2100 Project
+
+	Warzone 2100 is free software; you can redistribute it 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.
+
+	Warzone 2100 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 General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with Warzone 2100; if not, write to the Free Software
+	Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+*/
+
+#pragma once
+
+#include "net_result.h"
+
+#include <stddef.h>
+#include <stdint.h>
+#include <vector>
+
+/// <summary>
+/// Generic facade for integration of various compression algorithms into WZ's
+/// networking code.
+///
+/// Provides very basic facilities to initialize compression/decompression streams
+/// and perform compression/decompression tasks.
+/// </summary>
+class ICompressionAdapter
+{
+public:
+
+	virtual ~ICompressionAdapter() = default;
+
+	/// <summary>
+	/// The first thing that should be called on an `ICompressionAdapter` instance
+	/// before doing anything else with it.
+	///
+	/// Initializes states of internal buffers, streams, etc.
+	/// </summary>
+	/// <returns>
+	/// In case of failure, returns an error code describing the error.
+	/// </returns>
+	virtual net::result<void> initialize() = 0;
+
+	/// <summary>
+	/// Executes the compression routine against `src` buffer of a given size.
+	/// The result (compressed buffer) can be later accessed via `compressionOutBuffer()` function.
+	///
+	/// This function should be used to incrementally compress incoming data.
+	///
+	/// Note, that it won't necessarily flush all the data to the output buffer,
+	/// so one would then need to call `flushCompressionStream()` to flush all
+	/// internal streams to the output buffer.
+	/// </summary>
+	/// <param name="src">Source buffer containing uncompressed data</param>
+	/// <param name="size">Size of the source buffer in bytes</param>
+	/// <returns>
+	/// In case of failure, returns an error code describing the error.
+	/// </returns>
+	virtual net::result<void> compress(const void* src, size_t size) = 0;
+	/// <summary>
+	/// Flushes the internal compression stream to the output buffer.
+	/// The resulting data can be accessed via `compressionOutBuffer()`
+	/// accessor function.
+	/// </summary>
+	/// <returns>
+	/// In case of failure, returns an error code describing the error.
+	/// </returns>
+	virtual net::result<void> flushCompressionStream() = 0;
+	/// <summary>
+	/// Accessor function (non-const) for compression output buffer (this will be the
+	/// implicit destination to `compress()` and `flushCompressionStream()` functions.
+	/// </summary>
+	virtual std::vector<uint8_t>& compressionOutBuffer() = 0;
+	/// <summary>
+	/// Accessor function (const) for compression output buffer (this will be the
+	/// implicit destination to `compress()` and `flushCompressionStream()` functions.
+	/// </summary>
+	virtual const std::vector<uint8_t>& compressionOutBuffer() const = 0;
+
+	/// <summary>
+	/// Decompress the data from the compressed buffer into `dst` output buffer
+	/// of a given size.
+	///
+	/// The caller is responsible for ensuring that `dst` is long enough to
+	/// hold the decompression result of `size` length in bytes.
+	///
+	/// One would also need to call `resetDecompressionStreamInput()` function
+	/// first to specify the input buffer (containing compressed data) before
+	/// calling this function.
+	///
+	/// </summary>
+	/// <param name="dst">Destination buffer, where the decompressed data will go</param>
+	/// <param name="size">Size of the destination buffer</param>
+	/// <returns>
+	/// In case of failure, returns an error code describing the error.
+	/// </returns>
+	virtual net::result<void> decompress(void* dst, size_t size) = 0;
+	/// <summary>
+	/// Accessor function (non-const) for decompression input buffer (this will be
+	/// the implicit source for `decompress()` function).
+	/// </summary>
+	virtual std::vector<uint8_t>& decompressionInBuffer() = 0;
+	/// <summary>
+	/// Accessor function (const) for decompression input buffer (this will be
+	/// the implicit source for `decompress()` function).
+	/// </summary>
+	virtual const std::vector<uint8_t>& decompressionInBuffer() const = 0;
+	/// <summary>
+	/// Remaining free space (in bytes) at the decompression output buffer.
+	/// </summary>
+	virtual size_t availableSpaceToDecompress() const = 0;
+	/// <summary>
+	/// Returns `true` if the internal decompression stream doesn't have any more
+	/// available bytes in the input buffer (all input was consumed by a prior
+	/// `decompress()` function call).
+	/// </summary>
+	virtual bool decompressionStreamConsumedAllInput() const = 0;
+	/// <summary>
+	/// Returns `true` if the decompression algorithm needs to process more input (i.e.
+	/// there's more data available to process).
+	/// </summary>
+	virtual bool decompressionNeedInput() const = 0;
+	/// <summary>
+	/// Update the decompression algorithm on whether it needs more input or not.
+	/// </summary>
+	virtual void setDecompressionNeedInput(bool needInput) = 0;
+	/// <summary>
+	/// Updates the available input bytes count at the decompression input stream.
+	/// </summary>
+	/// <param name="size">New size for the decompression input stream</param>
+	virtual void resetDecompressionStreamInputSize(size_t size) = 0;
+};