From 4904a61ca08d7ca992afbb8bf94b1d08bd32462a Mon Sep 17 00:00:00 2001
From: Matt Harvey <mattharvey@google.com>
Date: Thu, 16 Sep 2021 18:42:08 +0000
Subject: [PATCH] Merge "Implements some std::io functions in kata_io"

GitOrigin-RevId: b5b1afb7b0528acd100fd35a84a48b984f1b02c1
---
 .../DebugConsole/kata-io/src/lib.rs           | 51 +++++++++++++++----
 .../DebugConsole/kata-line-reader/src/lib.rs  | 10 +++-
 2 files changed, 48 insertions(+), 13 deletions(-)

diff --git a/apps/system/components/DebugConsole/kata-io/src/lib.rs b/apps/system/components/DebugConsole/kata-io/src/lib.rs
index 9ca92d3..5557257 100644
--- a/apps/system/components/DebugConsole/kata-io/src/lib.rs
+++ b/apps/system/components/DebugConsole/kata-io/src/lib.rs
@@ -4,14 +4,43 @@ pub struct Error;
 
 pub type Result<T> = core::result::Result<T, Error>;
 
-/// Interface for the CLI to consume bytes.
+/// Partial mimic of std::io::Read.
 pub trait Read {
     fn read(&mut self, buf: &mut [u8]) -> Result<usize>;
+
+    fn read_exact(&mut self, mut buf: &mut [u8]) -> Result<()> {
+        while !buf.is_empty() {
+            match self.read(buf) {
+                Ok(0) => break,
+                Ok(n) => {
+                    let tmp = buf;
+                    buf = &mut tmp[n..];
+                }
+                Err(e) => return Err(e),
+            }
+        }
+        if !buf.is_empty() {
+            Err(Error)
+        } else {
+            Ok(())
+        }
+    }
 }
 
-/// Interface for the CLI to emit bytes.
+/// Partial mimic of std::io::Write.
 pub trait Write {
     fn write(&mut self, buf: &[u8]) -> Result<usize>;
+
+    fn write_all(&mut self, mut buf: &[u8]) -> Result<()> {
+        while !buf.is_empty() {
+            match self.write(buf) {
+                Ok(0) => return Err(Error),
+                Ok(n) => buf = &buf[n..],
+                Err(e) => return Err(e),
+            }
+        }
+        Ok(())
+    }
 }
 
 /// Adapter for writing core::fmt formatted strings.
@@ -25,13 +54,13 @@ impl core::fmt::Write for dyn Write + '_ {
     }
 }
 
-impl dyn Read + '_ {
-    pub fn get_u8(&mut self) -> Result<u8> {
-        let mut buf: [u8; 1] = [0u8];
-        let n_read = self.read(&mut buf)?;
-        match n_read {
-            1usize => Ok(buf[0]),
-            _ => Err(Error),
-        }
-    }
+pub enum SeekFrom {
+    Start(u64),
+    End(i64),
+    Current(i64),
+}
+
+/// Partial mimic of std::io::Seek.
+pub trait Seek {
+    fn seek(&mut self, pos: SeekFrom) -> Result<u64>;
 }
diff --git a/apps/system/components/DebugConsole/kata-line-reader/src/lib.rs b/apps/system/components/DebugConsole/kata-line-reader/src/lib.rs
index ccecae5..5bce7e0 100644
--- a/apps/system/components/DebugConsole/kata-line-reader/src/lib.rs
+++ b/apps/system/components/DebugConsole/kata-line-reader/src/lib.rs
@@ -39,6 +39,12 @@ pub struct LineReader {
     buf: [u8; LINE_MAX],
 }
 
+fn get_u8(reader: &mut dyn io::Read) -> io::Result<u8> {
+    let mut buf: [u8; 1] = [0u8];
+    reader.read_exact(&mut buf)?;
+    Ok(buf[0])
+}
+
 impl LineReader {
     pub fn new() -> LineReader {
         LineReader {
@@ -55,13 +61,13 @@ impl LineReader {
         const BACKSPACE: u8 = 8u8;
         let mut len = 0;
         while len < self.buf.len() {
-            let mut c = input.get_u8()?;
+            let mut c = get_u8(input)?;
             while c == DEL || c == BACKSPACE {
                 if len > 0 {
                     output.write(&[BACKSPACE, b' ', BACKSPACE])?;
                     len -= 1;
                 }
-                c = input.get_u8()?;
+                c = get_u8(input)?;
             }
             if c == b'\r' || c == b'\n' {
                 if len > 0 {