main.c

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#include <stdbool.h>
#include <stdio.h>
#include <string.h>
#include <windows.h>
 
typedef int (*launcher_main_fn)(int argc, char **argv);
 
static const char *const LAUNCHER_DLL_RELATIVE_PATH = "modules\\libdttr_launcher.dll";
 
static bool get_exe_dir(char *buf, size_t buf_size) {
    if (buf_size == 0) {
        return false;
    }
 
    const DWORD len = GetModuleFileNameA(NULL, buf, (DWORD)buf_size);
    if (len == 0 || len >= buf_size) {
        buf[0] = '\0';
        return false;
    }
 
    char *last_sep = strrchr(buf, '\\');
    if (!last_sep) {
        buf[0] = '\0';
        return false;
    }
 
    last_sep[1] = '\0';
    return true;
}
 
static bool launcher_dll_path(char *out, size_t out_size) {
    if (!get_exe_dir(out, out_size)) {
        return false;
    }
 
    const size_t len = strlen(out);
    if (len >= out_size) {
        return false;
    }
 
    const int
        written = snprintf(out + len, out_size - len, "%s", LAUNCHER_DLL_RELATIVE_PATH);
    return written > 0 && (size_t)written < out_size - len;
}
 
static void show_startup_error(const char *message, DWORD error) {
    char detail[512];
    char text[768];
 
    if (error
        && FormatMessageA(
            FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
            NULL,
            error,
            0,
            detail,
            sizeof(detail),
            NULL
        )
        && detail[0]) {
        snprintf(text, sizeof(text), "%s\n\nError %lu: %s", message, error, detail);
    } else {
        snprintf(text, sizeof(text), "%s", message);
    }
 
    MessageBoxA(NULL, text, "DttR: Error", MB_OK | MB_ICONERROR);
}
 
static launcher_main_fn resolve_launcher_main(HMODULE module) {
    return (launcher_main_fn)GetProcAddress(module, "dttr_launcher_main");
}
 
int main(int argc, char *argv[]) {
    char path[MAX_PATH];
    if (!launcher_dll_path(path, sizeof(path))) {
        show_startup_error("Could not resolve the DttR launcher module path.", 0);
        return 1;
    }
 
    HMODULE module = LoadLibraryExA(path, NULL, LOAD_WITH_ALTERED_SEARCH_PATH);
    if (!module) {
        show_startup_error(
            "Could not load modules\\libdttr_launcher.dll.",
            GetLastError()
        );
        return 1;
    }
 
    launcher_main_fn launcher_main = resolve_launcher_main(module);
    if (!launcher_main) {
        show_startup_error(
            "Could not find the DttR launcher entry point.",
            GetLastError()
        );
        FreeLibrary(module);
        return 1;
    }
 
    return launcher_main(argc, argv);
}