Initial commit

src/FileManager.cpp

@@ -0,0 +1,99 @@
+#include "FileManager.h"
+
+#include <cstring>
+#include <fstream>
+#include <sstream>
+#include <stdexcept>
+#include <utility>
+
+namespace NGame {
+
+TFileManager::TFileManager(const std::string& dataDirectory, const std::string& archivePath, std::size_t cacheSize) 
+    : DataDirectory_(dataDirectory), ArchivePath_(archivePath), Cache_(cacheSize) {
+    
+}
+
+std::string TFileManager::Get(const std::string& path) {
+    if (Cache_.Contains(path)) {
+        return Cache_.Get(path);
+    }
+
+    auto getAttempt = FromFilesystem(path);
+    if (getAttempt.second) {
+        Cache_.Set(path, getAttempt.first);
+        return getAttempt.first;
+    }
+
+    getAttempt = FromArchive(path);
+    if (getAttempt.second) {
+        Cache_.Set(path, getAttempt.first);
+        return getAttempt.first;
+    }
+
+    throw std::runtime_error("can't find file " + path);
+}
+
+std::pair<std::string, bool> TFileManager::FromFilesystem(const std::string& path) {
+    auto finalPath = DataDirectory_ + "/" + path;
+    
+    std::ifstream fileStream(finalPath, std::ios::in | std::ios::binary);
+    if (!fileStream.is_open()) {
+        return std::make_pair<std::string, bool>({}, false);
+    }
+
+    std::stringstream fileStringStream;
+    fileStringStream << fileStream.rdbuf();
+    return std::make_pair(fileStringStream.str(), true);
+}
+
+std::pair<std::string, bool> TFileManager::FromArchive(const std::string& path) {
+    std::ifstream archiveStream(ArchivePath_, std::ios::in | std::ios::binary);
+    if (!archiveStream.is_open()) {
+        return std::make_pair<std::string, bool>({}, false);
+    }
+    
+    // Identify and validate PAK file
+    char identifier[4];
+    archiveStream.read(identifier, 4);
+    if (std::memcmp(identifier, "PACK", 4)) {
+        return std::make_pair<std::string, bool>({}, false);
+    }
+    
+    std::uint32_t tocOffset = ReadInt32(archiveStream);
+    std::uint32_t tocSize = ReadInt32(archiveStream) / 64;
+
+    if (!tocSize || tocOffset < 12) {
+        return std::make_pair<std::string, bool>({}, false);
+    }
+
+    // Find requested file
+    archiveStream.seekg(tocOffset);
+
+    for (std::uint32_t index = 0; index < tocSize; ++index) {
+        char name[56];
+        
+        archiveStream.read(name, 56);
+        std::uint32_t fileOffset = ReadInt32(archiveStream);
+        std::uint32_t fileSize = ReadInt32(archiveStream);
+
+        if (std::strncmp(name, path.c_str(), 56)) {
+            continue;
+        }
+
+        archiveStream.seekg(fileOffset);
+        std::string result(fileSize, 0);
+        archiveStream.read(result.data(), result.size());
+
+        return std::make_pair(result, true);
+    }
+
+    return std::make_pair<std::string, bool>({}, false);
+}
+
+std::uint32_t TFileManager::ReadInt32(std::ifstream& stream) {
+    unsigned char bytes[4];
+    stream.read(reinterpret_cast<char*>(bytes), 4);
+    return (bytes[0] << 0) | (bytes[1] << 8) | (bytes[2] << 16) | (bytes[3] << 24);
+}
+
+} // namespace NGame