From 2252edf22816f27a934bca50c2c8b1b302c3178f Mon Sep 17 00:00:00 2001
From: Paul Pan <i@0x7f.app>
Date: Fri, 15 Sep 2023 16:49:55 +0800
Subject: [PATCH] feat: implement Reader on RawConsole

---
 src/arch/io.rs                       | 10 ++++++----
 src/arch/riscv/board/virt/mod.rs     |  2 ++
 src/arch/riscv/board/virt/printer.rs |  6 ++++++
 src/arch/riscv/board/virt/reader.rs  | 11 +++++++++++
 src/arch/riscv/io.rs                 | 16 +++++++++++++++-
 src/lib.rs                           |  1 +
 6 files changed, 41 insertions(+), 5 deletions(-)
 create mode 100644 src/arch/riscv/board/virt/reader.rs

diff --git a/src/arch/io.rs b/src/arch/io.rs
index caa84a5..40288a3 100644
--- a/src/arch/io.rs
+++ b/src/arch/io.rs
@@ -1,8 +1,6 @@
-use core::fmt::Write;
-
 pub struct RawConsole;
 
-pub trait Printer: Write {
+pub trait Printer: core::fmt::Write {
     fn put_char(c: char);
 
     #[inline]
@@ -64,7 +62,11 @@ pub trait Printer: Write {
     }
 }
 
-impl Write for RawConsole {
+pub trait Reader {
+    fn get_char() -> char;
+}
+
+impl core::fmt::Write for RawConsole {
     fn write_str(&mut self, s: &str) -> core::fmt::Result {
         Self::put_str(s);
         Ok(())
diff --git a/src/arch/riscv/board/virt/mod.rs b/src/arch/riscv/board/virt/mod.rs
index 545cbe0..7cd41af 100644
--- a/src/arch/riscv/board/virt/mod.rs
+++ b/src/arch/riscv/board/virt/mod.rs
@@ -1,3 +1,5 @@
 pub const UART0_BASE: usize = 0x1000_0000;
+pub const UART0_LSR: usize = 0x1000_0005;
 
 pub mod printer;
+pub mod reader;
diff --git a/src/arch/riscv/board/virt/printer.rs b/src/arch/riscv/board/virt/printer.rs
index 8b98120..611427b 100644
--- a/src/arch/riscv/board/virt/printer.rs
+++ b/src/arch/riscv/board/virt/printer.rs
@@ -1,5 +1,11 @@
 use crate::arch::io::{Printer, RawConsole};
 
+/*
+    Theoretically, we should wait until
+    "THR Empty" bit (1<<5 in LSR) is set
+    before writing to UART.
+*/
+
 impl Printer for RawConsole {
     #[inline]
     fn put_char(c: char) {
diff --git a/src/arch/riscv/board/virt/reader.rs b/src/arch/riscv/board/virt/reader.rs
new file mode 100644
index 0000000..d2b07cb
--- /dev/null
+++ b/src/arch/riscv/board/virt/reader.rs
@@ -0,0 +1,11 @@
+use crate::arch::io::{RawConsole, Reader};
+
+impl Reader for RawConsole {
+    #[inline]
+    fn get_char() -> char {
+        let uart = super::UART0_BASE as *mut char;
+        let line_sts = super::UART0_LSR as *mut u8;
+        while unsafe { line_sts.read_volatile() } & 0x01 == 0 {}
+        unsafe { uart.read_volatile() }
+    }
+}
diff --git a/src/arch/riscv/io.rs b/src/arch/riscv/io.rs
index 41f1697..bcb6486 100644
--- a/src/arch/riscv/io.rs
+++ b/src/arch/riscv/io.rs
@@ -1,5 +1,5 @@
 #[allow(unused_imports)]
-use crate::arch::io::{Printer, RawConsole};
+use crate::arch::io::{Printer, RawConsole, Reader};
 
 #[cfg(feature = "board_default")]
 impl Printer for RawConsole {
@@ -8,3 +8,17 @@ impl Printer for RawConsole {
         sbi_rt::legacy::console_putchar(c as usize);
     }
 }
+
+#[cfg(feature = "board_default")]
+impl Reader for RawConsole {
+    fn get_char() -> char {
+        loop {
+            #[allow(deprecated)]
+            let ch = sbi_rt::legacy::console_getchar();
+            if ch == usize::MAX {
+                continue;
+            }
+            return ch as u8 as char;
+        }
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 72ce742..c3ae463 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3,6 +3,7 @@
 #![feature(naked_functions)]
 #![feature(panic_info_message)]
 #![feature(fmt_internals)]
+#![feature(stmt_expr_attributes)]
 
 // arch
 pub mod arch;