feat: book decryption

All credits go to gawgua for his work, tysm.

decypherer/.gitignore

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+### C++ template
+cmake-*/
+.idea/
+
+# Compiled Object files
+*.slo
+*.lo
+*.o
+*.obj
+
+# Precompiled Headers
+*.gch
+*.pch
+
+# Compiled Dynamic libraries
+*.so
+*.dylib
+*.dll
+
+# Fortran module files
+*.mod
+
+# Compiled Static libraries
+*.lai
+*.la
+*.a
+*.lib
+
+# Executables
+*.exe
+*.out
+*.app
+
+

decypherer/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.30)
+project(decypherer)
+
+set(CMAKE_CXX_STANDARD 20)
+set(CMAKE_CXX_FLAGS -m32)
+
+add_executable(decypherer main.cpp)

decypherer/main.cpp

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+// Again, this is ported C++ code from gawgua's original Python code.
+// All credits go to him, I just used DeepSeek to convert it to C++.
+
+#include <iostream>
+#include <format>
+#include <Windows.h>
+#include <libloaderapi.h>
+
+// MuPDF structure definition
+struct pdf_write_options {
+    int do_incremental;
+    int do_pretty;
+    int do_ascii;
+    int do_compress;
+    int do_compress_images;
+    int do_compress_fonts;
+    int do_decompress;
+    int do_garbage;
+    int do_linear;
+    int do_clean;
+    int do_sanitize;
+    int do_appearance;
+    int do_encrypt;
+    int dont_regenerate_id;
+    int permissions;
+    char opwd_utf8[128];
+    char upwd_utf8[128];
+    int do_snapshot;
+    int do_preserve_metadata;
+    int do_use_objstms;
+    int compression_effort;
+};
+
+int main(const int argc, char* argv[])
+{
+	if (argc < 3) {
+		std::cout << "usage: decypherer.exe <window id> <path> <output>" << std::endl;
+		return 0;
+	}
+    // Arg 1
+    auto window_id = argv[1];
+    // Arg 2
+    auto path = argv[2];
+    // Arg 3
+	const auto output = argv[3];
+
+    const HMODULE mupdf = LoadLibraryA("mupdf-exp-dll-x86.dll");
+    if (mupdf == nullptr) {
+		std::cout << "error: failed to load MuPDF library" << std::endl;
+		return 1;
+    }
+
+    // Define function pointers
+    const auto fz_new_context_imp = reinterpret_cast<void* (*)(void *, void *, unsigned int, const char *)>(GetProcAddress(mupdf, "fz_new_context_imp"));
+    const auto fz_register_document_handlers = reinterpret_cast<void* (*)(void *)>(GetProcAddress(mupdf, "fz_register_document_handlers"));
+    const auto fz_open_document_w = reinterpret_cast<void* (*)(void *, const wchar_t *)>(GetProcAddress(mupdf, "fz_open_document_w"));
+    const auto pdf_save_document = reinterpret_cast<void(*)(void *, void *, const char *, pdf_write_options *)>(GetProcAddress(mupdf, "pdf_save_document"));
+
+    // Build argument path
+    auto arg_path_str = std::format("#OCB#{}#{}", window_id, path);
+    const std::wstring arg_path(arg_path_str.begin(), arg_path_str.end());
+
+    // Create context
+    void* ctx = fz_new_context_imp(nullptr, nullptr, 268435456, "1.16.1");
+    fz_register_document_handlers(ctx);
+
+    // Open document
+    void* doc = fz_open_document_w(ctx, arg_path.c_str());
+
+    // Set save options
+    pdf_write_options opts = {
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, ~0,
+        {}, {}, 0, 0, 0, 0
+    };
+
+    // Save document
+    pdf_save_document(ctx, doc, output, &opts);
+    FreeLibraryAndExitThread(mupdf, 0);
+}