From 62732d7b7f184d182b5d26c13a6752f1c328f5e1 Mon Sep 17 00:00:00 2001
From: Naoki Ikeguchi <me@s6n.jp>
Date: Sat, 24 Sep 2022 13:28:13 +0900
Subject: [PATCH 1/2] feat: Support no_std environment

---
 apdu-core/Cargo.toml     | 4 ++++
 apdu-core/src/command.rs | 3 +++
 apdu-core/src/error.rs   | 5 +++--
 apdu-core/src/lib.rs     | 4 ++++
 4 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/apdu-core/Cargo.toml b/apdu-core/Cargo.toml
index 60342fb..e975cf3 100644
--- a/apdu-core/Cargo.toml
+++ b/apdu-core/Cargo.toml
@@ -14,3 +14,7 @@ authors = [
 ]
 
 [dependencies]
+
+[features]
+std = []
+default = ["std"]
diff --git a/apdu-core/src/command.rs b/apdu-core/src/command.rs
index 11790c5..d0c928b 100644
--- a/apdu-core/src/command.rs
+++ b/apdu-core/src/command.rs
@@ -1,3 +1,6 @@
+use alloc::vec;
+use alloc::vec::Vec;
+
 /// An APDU command to be transmitted
 pub struct Command {
     pub cla: u8,
diff --git a/apdu-core/src/error.rs b/apdu-core/src/error.rs
index e6f57f8..392cf1c 100644
--- a/apdu-core/src/error.rs
+++ b/apdu-core/src/error.rs
@@ -1,4 +1,4 @@
-use std::fmt::{Display, Formatter};
+use core::fmt::{Display, Formatter};
 
 use crate::Response;
 
@@ -9,7 +9,7 @@ pub struct Error {
 }
 
 impl Display for Error {
-    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
         let (sw1, sw2) = self.response.trailer;
 
         write!(
@@ -20,4 +20,5 @@ impl Display for Error {
     }
 }
 
+#[cfg(feature = "std")]
 impl std::error::Error for Error {}
diff --git a/apdu-core/src/lib.rs b/apdu-core/src/lib.rs
index 3d6e6d8..38e755a 100644
--- a/apdu-core/src/lib.rs
+++ b/apdu-core/src/lib.rs
@@ -1,5 +1,9 @@
 //! Core library for composing APDU commands and parsing their responses.
 
+#![cfg_attr(not(feature = "std"), no_std)]
+
+extern crate alloc;
+
 mod command;
 mod error;
 mod response;

From 343a9a42075e459c8c9596705021e24562ab9d0c Mon Sep 17 00:00:00 2001
From: Naoki Ikeguchi <me@s6n.jp>
Date: Sat, 24 Sep 2022 13:31:05 +0900
Subject: [PATCH 2/2] docs: Document about no_std support

---
 README.md | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/README.md b/README.md
index 8bde299..0e53f39 100644
--- a/README.md
+++ b/README.md
@@ -25,5 +25,14 @@ Add to your Cargo.toml as a dependency as follows:
 apdu = "0.2"
 ```
 
+## 🛠 no_std support
+apdu-core crate does support no_std environments.
+If you are using this crate in no_std, turn `std` feature off by disabling default features:
+
+```toml
+[dependencies]
+apdu-core = { version = "0.2", default-features = false }
+```
+
 ## 📄 Documentation
 See [docs.rs](https://docs.rs/apdu/).