From e5413c066489a5ed388a78c789de9c347a4616bc Mon Sep 17 00:00:00 2001
From: elsid <elsid.mail@gmail.com>
Date: Mon, 18 Oct 2021 01:43:33 +0200
Subject: [PATCH] Add functions to compress/decompress vector of bytes

---
 apps/openmw_test_suite/CMakeLists.txt       |  1 +
 apps/openmw_test_suite/misc/compression.cpp | 31 +++++++++++++
 components/CMakeLists.txt                   |  1 +
 components/misc/compression.cpp             | 48 +++++++++++++++++++++
 components/misc/compression.hpp             | 14 ++++++
 5 files changed, 95 insertions(+)
 create mode 100644 apps/openmw_test_suite/misc/compression.cpp
 create mode 100644 components/misc/compression.cpp
 create mode 100644 components/misc/compression.hpp

diff --git a/apps/openmw_test_suite/CMakeLists.txt b/apps/openmw_test_suite/CMakeLists.txt
index e8a296b563..3d19834066 100644
--- a/apps/openmw_test_suite/CMakeLists.txt
+++ b/apps/openmw_test_suite/CMakeLists.txt
@@ -25,6 +25,7 @@ if (GTEST_FOUND AND GMOCK_FOUND)
         misc/test_stringops.cpp
         misc/test_endianness.cpp
         misc/progressreporter.cpp
+        misc/compression.cpp
 
         nifloader/testbulletnifloader.cpp
 
diff --git a/apps/openmw_test_suite/misc/compression.cpp b/apps/openmw_test_suite/misc/compression.cpp
new file mode 100644
index 0000000000..e062599f4a
--- /dev/null
+++ b/apps/openmw_test_suite/misc/compression.cpp
@@ -0,0 +1,31 @@
+#include <components/misc/compression.hpp>
+
+#include <gtest/gtest.h>
+
+#include <algorithm>
+#include <cstdlib>
+#include <cstring>
+
+namespace
+{
+    using namespace testing;
+    using namespace Misc;
+
+    TEST(MiscCompressionTest, compressShouldAddPrefixWithDataSize)
+    {
+        const std::vector<std::byte> data(1234);
+        const std::vector<std::byte> compressed = compress(data);
+        int size = 0;
+        std::memcpy(&size, compressed.data(), sizeof(size));
+        EXPECT_EQ(size, data.size());
+    }
+
+    TEST(MiscCompressionTest, decompressIsInverseToCompress)
+    {
+        const std::vector<std::byte> data(1024);
+        const std::vector<std::byte> compressed = compress(data);
+        EXPECT_LT(compressed.size(), data.size());
+        const std::vector<std::byte> decompressed = decompress(compressed);
+        EXPECT_EQ(decompressed, data);
+    }
+}
diff --git a/components/CMakeLists.txt b/components/CMakeLists.txt
index e71aa88f3c..7b06b6702d 100644
--- a/components/CMakeLists.txt
+++ b/components/CMakeLists.txt
@@ -93,6 +93,7 @@ add_component_dir (esmterrain
 
 add_component_dir (misc
     constants utf8stream stringops resourcehelpers rng messageformatparser weakcache thread
+    compression
     )
 
 add_component_dir (debug
diff --git a/components/misc/compression.cpp b/components/misc/compression.cpp
new file mode 100644
index 0000000000..7f76d0900c
--- /dev/null
+++ b/components/misc/compression.cpp
@@ -0,0 +1,48 @@
+#include "compression.hpp"
+
+#include <lz4.h>
+
+#include <cstddef>
+#include <cstring>
+#include <stdexcept>
+#include <string>
+#include <vector>
+
+namespace Misc
+{
+    std::vector<std::byte> compress(const std::vector<std::byte>& data)
+    {
+        const std::size_t originalSize = data.size();
+        std::vector<std::byte> result(static_cast<std::size_t>(LZ4_compressBound(static_cast<int>(originalSize)) + sizeof(originalSize)));
+        const int size = LZ4_compress_default(
+            reinterpret_cast<const char*>(data.data()),
+            reinterpret_cast<char*>(result.data()) + sizeof(originalSize),
+            static_cast<int>(data.size()),
+            static_cast<int>(result.size() - sizeof(originalSize))
+        );
+        if (size == 0)
+            throw std::runtime_error("Failed to compress");
+        std::memcpy(result.data(), &originalSize, sizeof(originalSize));
+        result.resize(static_cast<std::size_t>(size) + sizeof(originalSize));
+        return result;
+    }
+
+    std::vector<std::byte> decompress(const std::vector<std::byte>& data)
+    {
+        std::size_t originalSize;
+        std::memcpy(&originalSize, data.data(), sizeof(originalSize));
+        std::vector<std::byte> result(originalSize);
+        const int size = LZ4_decompress_safe(
+            reinterpret_cast<const char*>(data.data()) + sizeof(originalSize),
+            reinterpret_cast<char*>(result.data()),
+            static_cast<int>(data.size() - sizeof(originalSize)),
+            static_cast<int>(result.size())
+        );
+        if (size < 0)
+            throw std::runtime_error("Failed to decompress");
+        if (originalSize != static_cast<std::size_t>(size))
+            throw std::runtime_error("Size of decompressed data (" + std::to_string(size)
+                                     + ") doesn't match stored (" + std::to_string(originalSize) + ")");
+        return result;
+    }
+}
diff --git a/components/misc/compression.hpp b/components/misc/compression.hpp
new file mode 100644
index 0000000000..2b951ebed6
--- /dev/null
+++ b/components/misc/compression.hpp
@@ -0,0 +1,14 @@
+#ifndef OPENMW_COMPONENTS_MISC_COMPRESSION_H
+#define OPENMW_COMPONENTS_MISC_COMPRESSION_H
+
+#include <cstddef>
+#include <vector>
+
+namespace Misc
+{
+    std::vector<std::byte> compress(const std::vector<std::byte>& data);
+
+    std::vector<std::byte> decompress(const std::vector<std::byte>& data);
+}
+
+#endif