From 97afdf08922956627073d929bcb2529306333313 Mon Sep 17 00:00:00 2001
From: Lukas Oesch <lukasoesch20@gmail.com>
Date: Sat, 25 Apr 2026 23:29:27 +0200
Subject: add demo code

---
 kernel/src/main.cpp | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)

(limited to 'kernel')

diff --git a/kernel/src/main.cpp b/kernel/src/main.cpp
index 60b6e6e..9f4ec1e 100644
--- a/kernel/src/main.cpp
+++ b/kernel/src/main.cpp
@@ -9,6 +9,7 @@
 #include <kapi/cio.hpp>
 #include <kapi/cpu.hpp>
 #include <kapi/devices.hpp>
+#include <kapi/filesystem.hpp>
 #include <kapi/interrupts.hpp>
 #include <kapi/memory.hpp>
 #include <kapi/system.hpp>
@@ -187,6 +188,64 @@ auto run_test_code() -> void
   kstd::println("---------------------------------");
 }
 
+auto run_demo() -> void
+{
+  // 1) open a file
+  auto fd_1 = kapi::filesystem::open("/entrance/tickets.txt");
+  if (fd_1 == -1)
+  {
+    kstd::os::panic("demo failed");
+  }
+
+  // 2) read from the file
+  kstd::vector<std::byte> buffer_1{10};
+  auto bytes_read = kapi::filesystem::read(fd_1, buffer_1.data(), buffer_1.size());
+  auto buffer_as_str = std::string_view{reinterpret_cast<char *>(buffer_1.data()), static_cast<size_t>(bytes_read)};
+  kstd::println("Read {} bytes from /entrance/tickets.txt: {}", bytes_read, buffer_as_str);
+
+  // 3) show that /entrance/information/info_1.txt is not accessible before mounting
+  auto fd_before_mount = kapi::filesystem::open("/entrance/information/info_1.txt");
+  if (fd_before_mount == -1)
+  {
+    kstd::println("/entrance/information/info_1.txt is not accessible before mounting, as expected.");
+  }
+
+  // 4) mount a new filesystem on top of /entrance
+  kapi::filesystem::mount("/dev/ram16", "/entrance");
+
+  // 5) open a file from the new filesystem
+  auto fd_2 = kapi::filesystem::open("/entrance/information/info_1.txt");
+  if (fd_2 == -1)
+  {
+    kstd::os::panic("demo failed");
+  }
+
+  // 6) read from the new file
+  kstd::vector<std::byte> buffer_2{10};
+  bytes_read = kapi::filesystem::read(fd_2, buffer_2.data(), buffer_2.size());
+  buffer_as_str = std::string_view{reinterpret_cast<char *>(buffer_2.data()), static_cast<size_t>(bytes_read)};
+  kstd::println("Read {} bytes from /entrance/information/info_1.txt: {}", bytes_read, buffer_as_str);
+
+  // 7) open device as file
+  auto fd_3 = kapi::filesystem::open("/dev/ram48");
+  if (fd_3 == -1)
+  {
+    kstd::os::panic("demo failed");
+  }
+
+  // 8) read from the device file
+  kstd::vector<std::byte> buffer_3{2};
+  bytes_read = kapi::filesystem::read(fd_3, buffer_3.data(), buffer_3.size());
+  kstd::println("Read {} bytes from /dev/ram48: {::#04x}", bytes_read, buffer_3);
+
+  // 9) write to the device file
+  kstd::vector<std::byte> write_buffer{std::byte{0xAA}, std::byte{0xAA}};
+  auto bytes_written = kapi::filesystem::write(fd_3, write_buffer.data(), write_buffer.size());
+  kstd::println("Written {} bytes to /dev/ram48: {::#04x}", bytes_written, write_buffer);
+
+  // 10) do memory dump to show that the write to the device file had an effect
+}
+
 auto main() -> int
 {
   kapi::cio::init();
@@ -221,6 +280,10 @@ auto main() -> int
   kernel::filesystem::vfs::init();
   kstd::println("[OS] Virtual filesystem initialized.");
 
+  // TODO BA-FS26 remove demo and test code again?
+  // run_demo();
+
+  // TODO BA-FS26 remove demo and test code again?
   run_test_code();
   kstd::println("[TEST] All tests completed.");
 
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