From d0ecdbef0073a5516c9b7ec56d346cf9f1febd14 Mon Sep 17 00:00:00 2001
From: natrixaeria <upezu@student.kit.edu>
Date: Sat, 9 Nov 2019 01:00:09 +0100
Subject: Create panic screen module with text buffer

---
 kernel/src/io/mod.rs          |  1 +
 kernel/src/io/panic_screen.rs | 57 +++++++++++++++++++++++++++++++++++++++++++
 kernel/src/io/vga_text.rs     | 34 ++++++++------------------
 kernel/src/lib.rs             | 28 ++-------------------
 4 files changed, 70 insertions(+), 50 deletions(-)
 create mode 100644 kernel/src/io/panic_screen.rs

diff --git a/kernel/src/io/mod.rs b/kernel/src/io/mod.rs
index 9ac924a..e5dc66f 100644
--- a/kernel/src/io/mod.rs
+++ b/kernel/src/io/mod.rs
@@ -1,3 +1,4 @@
 pub mod qemu;
 pub mod serial;
 pub mod vga_text;
+pub mod panic_screen;
diff --git a/kernel/src/io/panic_screen.rs b/kernel/src/io/panic_screen.rs
new file mode 100644
index 0000000..ce2c118
--- /dev/null
+++ b/kernel/src/io/panic_screen.rs
@@ -0,0 +1,57 @@
+use core::fmt::Write;
+use crate::io::vga_text::{OStream, CharState, Color};
+
+const PANIC_SCREEN_MESSAGE_BUFFER_SIZE: usize = 2048;
+
+struct TextBuffer<'a> {
+    dst: &'a mut [u8],
+    len: usize
+}
+
+impl<'a> TextBuffer<'a> {
+    fn new(dst: &'a mut [u8]) -> Self {
+        Self { dst, len: 0 }
+    }
+    fn get(&'a mut self) -> &'a mut [u8] {
+        &mut self.dst[..self.len]
+    }
+}
+
+impl<'a> core::fmt::Write for TextBuffer<'a> {
+    fn write_str(&mut self, s: &str) -> core::fmt::Result {
+        if s.len() + self.len > self.dst.len() {
+            Err(core::fmt::Error)
+        } else {
+            let s = s.as_bytes();
+            (&mut self.dst[self.len..self.len+s.len()]).clone_from_slice(s);
+            Ok(self.len += s.len())
+        }
+    }
+}
+
+pub fn show(args: Option<&core::fmt::Arguments>) {
+    let mut stderr = OStream::new();
+    stderr.set_state(CharState::from_colors(
+        Color::LightRed,
+        Color::Red,
+    ));
+    stderr.clear();
+    stderr.print(b"uff-os");
+    stderr.set_row(10);
+    stderr.set_state(CharState::from_colors(
+        Color::White,
+        Color::Red,
+    ));
+    stderr.print_centered(b"<kernel panic>");
+    stderr.set_row(14);
+    stderr.set_state(CharState::from_colors(
+        Color::Cyan,
+        Color::Red,
+    ));
+    stderr.set_centered(true);
+    let buffer: &mut [u8] = &mut [b' '; PANIC_SCREEN_MESSAGE_BUFFER_SIZE];
+    let mut tbuffer = TextBuffer::new(buffer);
+    let _ = core::fmt::write(&mut tbuffer, *args.unwrap_or(&format_args!("no panic information obtainable")));
+    stderr.print(tbuffer.get());
+    stderr.set_centered(false);
+}
diff --git a/kernel/src/io/vga_text.rs b/kernel/src/io/vga_text.rs
index 281a40a..eef56bf 100644
--- a/kernel/src/io/vga_text.rs
+++ b/kernel/src/io/vga_text.rs
@@ -103,7 +103,7 @@ impl OStream {
     pub fn put_char(&mut self, c: VgaChar) {
         if c.byte == b'\n' {
             self.new_line();
-        } else if self.pos.0 >= WIDTH - 1 {
+        } else if self.pos.0 >= WIDTH {
             self.new_line();
             self.put_char(c);
         } else {
@@ -158,31 +158,17 @@ impl OStream {
     }
 
     pub fn print_centered(&mut self, s: &[u8]) {
-        let mut line = &s[..];
-        let mut n = 0;
-        if s.len() == 0 { return; }
-        let slast = s.len() - 1;
-        for (i, &b) in s.iter().enumerate() {
-            if n >= WIDTH {
-                self.set_col(0);
-                self.put_bytes(&line[..WIDTH]);
-                line = &line[WIDTH..];
-                n = 0;
-            }
-            if b == b'\n' || i == slast {
-                if b != b'\n' {
-                    n += 1
-                }
-                self.set_col(((WIDTH - n) / 2) as usize);
-                self.put_bytes(&line[..n]);
+        let mut line_start = 0;
+        let mut line_len = 0;
+        for (n, &c) in s.iter().enumerate() {
+            if line_len >= WIDTH || c == b'\n' || n == s.len() - 1 {
+                self.set_col((WIDTH - line_len) >> 1);
+                self.put_bytes(&s[line_start..(line_start+line_len+1)]);
                 self.new_line();
-                if i == slast {
-                    return;
-                }
-                line = &line[(n + 1)..];
-                n = 0;
+                line_start += line_len;
+                line_len = 0;
             }
-            n += 1;
+            line_len += 1;
         }
     }
 }
diff --git a/kernel/src/lib.rs b/kernel/src/lib.rs
index 15f027b..623f2bc 100644
--- a/kernel/src/lib.rs
+++ b/kernel/src/lib.rs
@@ -57,32 +57,8 @@ pub extern "C" fn _start() -> ! {
 #[panic_handler]
 #[no_mangle]
 pub extern "C" fn panic_handler(info: &core::panic::PanicInfo) -> ! {
-    let mut stderr = OStream::new();
-    stderr.set_state(vga_text::CharState::from_colors(
-        vga_text::Color::LightRed,
-        vga_text::Color::Red,
-    ));
-    stderr.clear();
-    stderr.print(b"uff-os");
-    stderr.set_row(10);
-    stderr.set_state(vga_text::CharState::from_colors(
-        vga_text::Color::White,
-        vga_text::Color::Red,
-    ));
-    stderr.print_centered(b"<kernel panic>");
-    stderr.set_row(14);
-    stderr.set_state(vga_text::CharState::from_colors(
-        vga_text::Color::Cyan,
-        vga_text::Color::Red,
-    ));
-    stderr.set_centered(true);
-    write!(
-        &mut stderr,
-        "{:?}",
-        info.message()
-            .unwrap_or(&format_args!("no panic information obtainable"))
-    );
-    stderr.set_centered(false);
+    io::panic_screen::show(info.message());
+
     if cfg!(test) {
         write!(serial::SerialStream::new(), "Testing failed\n").unwrap();
         qemu::exit_qemu(qemu::QemuExitCode::Failed);
-- 
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