From 33f04012168f3a2341f57f7fc0a0e9baf7fd364d Mon Sep 17 00:00:00 2001
From: Robin Krahl <robin@nitrokey.com>
Date: Mon, 9 Oct 2023 20:41:35 +0200
Subject: [PATCH] Refactor CommandView::to_owned

This patch replaces Vec::from_slice with Vec::extend_from_slice in
CommandView::to_owned.  This reduces the stack usage on lpc55 to one
third (!), from ca. 23 kB to ca. 8 kB with S = 7609.
---
 src/command.rs | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/src/command.rs b/src/command.rs
index d14d269..c93bae8 100644
--- a/src/command.rs
+++ b/src/command.rs
@@ -567,10 +567,12 @@ impl<'a> CommandView<'a> {
             p1,
             p2,
             le,
-            data,
+            data: data_slice,
             extended,
         } = self;
-        Ok(Command {
+        // We use this way to construct the command instead of Data::from_slice as that would
+        // triple stack usage on the lpc55.
+        let mut command = Command {
             // header
             class,
             instruction,
@@ -579,9 +581,14 @@ impl<'a> CommandView<'a> {
             // maximum expected response length
             le,
             // payload
-            data: Data::from_slice(data).map_err(|_| FromSliceError::TooLong)?,
+            data: Data::new(),
             extended,
-        })
+        };
+        command
+            .data
+            .extend_from_slice(data_slice)
+            .map_err(|_| FromSliceError::TooLong)?;
+        Ok(command)
     }
 }