minecraft-pi-reborn/launcher/src/client/cache.cpp

#include <cstdlib>
#include <string>
#include <fstream>
#include <unordered_map>
#include <sstream>
#include <sys/stat.h>
#include <unistd.h>

#include <libreborn/libreborn.h>

#include "launcher.h"
#include "cache.h"

// Get Cache Path
static std::string get_cache_path() {
    const char *home = getenv("HOME");
    if (home == NULL) {
        IMPOSSIBLE();
    }
    return std::string(home) + HOME_SUBDIRECTORY_FOR_GAME_DATA "/.launcher-cache";
}

// Load
launcher_cache empty_cache = {
    .username = DEFAULT_USERNAME,
    .render_distance = DEFAULT_RENDER_DISTANCE,
    .feature_flags = {}
};
launcher_cache load_cache() {
    // Log
    DEBUG("Loading Launcher Cache...");

    // Return Value
    launcher_cache ret = empty_cache;

    // Open File
    std::ifstream stream(get_cache_path(), std::ios::in | std::ios::binary);
    if (!stream) {
        // Fail
        struct stat s;
        // No Warning If File Doesn't Exist
        if (stat(get_cache_path().c_str(), &s) == 0) {
            WARN("Unable To Open Launcher Cache For Loading");
        }
    } else {
        // Lock File
        int lock_fd = lock_file(get_cache_path().c_str());

        // Check Version
        unsigned char cache_version;
        stream.read((char *) &cache_version, 1);
        if (stream.eof() || cache_version != (unsigned char) CACHE_VERSION) {
            // Fail
            if (!stream.eof()) {
                WARN("Invalid Launcher Cache Version (Expected: %i, Actual: %i)", (int) CACHE_VERSION, (int) cache_version);
            } else {
                WARN("Unable To Read Launcher Cache Version");
            }
            stream.close();
        } else {
            // Load Username And Render Distance
            launcher_cache cache;
            std::getline(stream, cache.username, '\0');
            std::getline(stream, cache.render_distance, '\0');

            // Load Feature Flags
            std::string flag;
            while (!stream.eof() && std::getline(stream, flag, '\0')) {
                if (flag.length() > 0) {
                    unsigned char is_enabled = 0;
                    stream.read((char *) &is_enabled, 1);
                    cache.feature_flags[flag] = is_enabled != (unsigned char) 0;
                }
                stream.peek();
            }

            // Finish
            stream.close();
            if (!stream) {
                // Fail
                WARN("Failure While Loading Launcher Cache");
            } else {
                // Success
                ret = cache;
            }
        }

        // Unlock File
        unlock_file(get_cache_path().c_str(), lock_fd);
    }

    // Return
    return ret;
}

// Save
#define write_env_to_stream(stream, env) \
    { \
        const char *env_value = getenv(env); \
        if (env == NULL) { \
            IMPOSSIBLE(); \
        } \
        stream.write(env_value, strlen(env_value) + 1); \
    }
void save_cache() {
    // Log
    DEBUG("Saving Launcher Cache...");

    // Open File
    std::ofstream stream(get_cache_path(), std::ios::out | std::ios::binary);
    if (!stream) {
        // Fail
        WARN("Unable To Open Launcher Cache For Saving");
    } else {
        // Lock File
        int lock_fd = lock_file(get_cache_path().c_str());

        // Save Cache Version
        unsigned char cache_version = (unsigned char) CACHE_VERSION;
        stream.write((const char *) &cache_version, 1);

        // Save Username And Render Distance
        write_env_to_stream(stream, "MCPI_USERNAME");
        write_env_to_stream(stream, "MCPI_RENDER_DISTANCE");

        // Save Feature Flags
        std::unordered_map<std::string, bool> flags;
        load_available_feature_flags([&flags](std::string flag) {
            std::string stripped_flag = strip_feature_flag_default(flag, NULL);
            flags[stripped_flag] = false;
        });
        {
            const char *enabled_flags = getenv("MCPI_FEATURE_FLAGS");
            if (enabled_flags == NULL) {
                IMPOSSIBLE();
            }
            std::istringstream enabled_flags_stream(enabled_flags);
            std::string flag;
            while (std::getline(enabled_flags_stream, flag, '|')) {
                if (flag.length() > 0) {
                    flags[flag] = true;
                }
            }
        }
        for (auto &it : flags) {
            stream.write(it.first.c_str(), it.first.size() + 1);
            unsigned char val = it.second ? (unsigned char) 1 : (unsigned char) 0;
            stream.write((const char *) &val, 1);
        }

        // Finish
        stream.close();
        if (!stream.good()) {
            WARN("Failure While Saving Launcher Cache");
        }

        // Unlock File
        unlock_file(get_cache_path().c_str(), lock_fd);
    }
}

// Wipe Cache
void wipe_cache() {
    // Log
    INFO("Wiping Launcher Cache...");

    // Unlink File
    if (unlink(get_cache_path().c_str()) != 0) {
        WARN("Failure While Wiping Cache: %s", strerror(errno));
    }
}