Use ssmarshal to convert data from and to byte slices

Previously, we manually converted the request and response data from and
to byte slices.  This patch adds the ssmarshal dependency that automates
the serialization and deserialization in the required format.

3 files changed, 61 insertions, 63 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 5437476..a729af6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -60,6 +60,11 @@ dependencies = [
 ]
 
 [[package]]
+name = "encode_unicode"
+version = "0.3.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
 name = "nb"
 version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -72,6 +77,8 @@ dependencies = [
  "cortex-m-rt 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "embedded-hal 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "panic-halt 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.88 (registry+https://github.com/rust-lang/crates.io-index)",
+ "ssmarshal 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "stm32f103xx-usb 0.1.0 (git+https://github.com/mvirkkunen/stm32f103xx-usb?rev=57d23751367461bec5f39322727bdd65e5c2aa30)",
  "stm32f1xx-hal 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "usb-device 0.2.0 (git+https://github.com/mvirkkunen/usb-device?rev=e58e30f3b9c9bf4aab00ea039d129b964a3fd2d3)",
@@ -146,6 +153,33 @@ version = "0.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
+name = "serde"
+version = "1.0.88"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "serde_derive 1.0.88 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "serde_derive"
+version = "1.0.88"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "proc-macro2 0.4.27 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 0.6.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 0.15.26 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "ssmarshal"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "encode_unicode 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.88 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
 name = "stm32f1"
 version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -228,6 +262,7 @@ dependencies = [
 "checksum cortex-m-rt 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)" = "f69d2beca37acc3776c17201c9d1f8904fb9139fa3a4d2cf28c8436a07b21a88"
 "checksum cortex-m-rt-macros 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "d7ae692573e0acccb1579fef1abf5a5bf1d2f3f0149a22b16870ec9309aee25f"
 "checksum embedded-hal 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "9880e55238830314d41d88f1ac7a819d495799c3cc3bc392cc172bab26428c33"
+"checksum encode_unicode 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)" = "90b2c9496c001e8cb61827acdefad780795c42264c137744cae6f7d9e3450abd"
 "checksum nb 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "69f380b5fe9fab8c0d7a6a99cda23e2cc0463bedb2cbc3aada0813b98496ecdc"
 "checksum panic-halt 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "de96540e0ebde571dc55c73d60ef407c653844e6f9a1e2fdbd40c07b9252d812"
 "checksum proc-macro2 0.4.27 (registry+https://github.com/rust-lang/crates.io-index)" = "4d317f9caece796be1980837fd5cb3dfec5613ebdb04ad0956deea83ce168915"
@@ -239,6 +274,9 @@ dependencies = [
 "checksum rustc_version 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)" = "138e3e0acb6c9fb258b19b67cb8abd63c00679d2851805ea151465464fe9030a"
 "checksum semver 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "1d7eb9ef2c18661902cc47e535f9bc51b78acd254da71d375c2f6720d9a40403"
 "checksum semver-parser 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "388a1df253eca08550bef6c72392cfe7c30914bf41df5269b68cbd6ff8f570a3"
+"checksum serde 1.0.88 (registry+https://github.com/rust-lang/crates.io-index)" = "9f301d728f2b94c9a7691c90f07b0b4e8a4517181d9461be94c04bddeb4bd850"
+"checksum serde_derive 1.0.88 (registry+https://github.com/rust-lang/crates.io-index)" = "beed18e6f5175aef3ba670e57c60ef3b1b74d250d962a26604bff4c80e970dd4"
+"checksum ssmarshal 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "f3e6ad23b128192ed337dfa4f1b8099ced0c2bf30d61e551b65fda5916dbb850"
 "checksum stm32f1 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)" = "48763f6f093674476399efbd8d2e52349dc32c3bbf57657234cbb15d309cd8a3"
 "checksum stm32f103xx-usb 0.1.0 (git+https://github.com/mvirkkunen/stm32f103xx-usb?rev=57d23751367461bec5f39322727bdd65e5c2aa30)" = "<none>"
 "checksum stm32f1xx-hal 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "f410543fc282d51e181e3cf5c8adff303d9e5ae8b9eb731e6a07f58a4cec4265"
diff --git a/Cargo.toml b/Cargo.toml
index e3614d5..a11296e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -22,6 +22,15 @@ package = "stm32f1xx-hal"
 version = "0.1.1"
 features = ["stm32f103", "rt"]
 
+[dependencies.serde]
+version = "1.0"
+default-features = false
+features = ["derive"]
+
+[dependencies.ssmarshal]
+version = "1.0"
+default-features = false
+
 [profile.release]
 codegen-units = 1
 debug = true
diff --git a/src/commands.rs b/src/commands.rs
index 62e2983..d2769ed 100644
--- a/src/commands.rs
+++ b/src/commands.rs
@@ -2,7 +2,9 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 use core::default::Default;
-use core::marker::Sized;
+
+use serde::{Deserialize, Serialize};
+use serde::de::DeserializeOwned;
 
 use crate::device::CommandStatus;
 
@@ -16,32 +18,21 @@ enum_cmd! {
     }
 }
 
-trait RequestData: Sized {
-    fn from_bytes(data: &[u8]) -> Option<Self>;
-}
-
-impl RequestData for () {
-    fn from_bytes(_data: &[u8]) -> Option<Self> {
-        Some(())
-    }
-}
-
-trait ResponseData {
-    fn write_bytes(&self, buf: &mut [u8]);
-}
-
 trait Command {
-    type Request: RequestData;
-    type Response: ResponseData;
+    type Request: DeserializeOwned;
+    type Response: Serialize;
 
     fn execute(data: Self::Request) -> Result<Self::Response, CommandStatus>;
 
     fn execute_raw(data: &[u8], buf: &mut [u8]) -> CommandStatus {
-        if let Some(request) = Self::Request::from_bytes(data) {
+        // TODO: better error if (de-)serialization fails
+        if let Ok((request, _)) = ssmarshal::deserialize::<Self::Request>(data) {
             match Self::execute(request) {
                 Ok(response) => {
-                    response.write_bytes(buf);
-                    CommandStatus::Ok
+                    match ssmarshal::serialize(buf, &response) {
+                        Ok(_) => CommandStatus::Ok,
+                        Err(_) => CommandStatus::NotSupported,
+                    }
                 }
                 Err(status) => status,
             }
@@ -51,7 +42,7 @@ trait Command {
     }
 }
 
-#[derive(Debug, Default)]
+#[derive(Debug, Default, Serialize)]
 struct GetStatusResponse {
     firmware_version_minor: u8,
     firmware_version_major: u8,
@@ -60,27 +51,6 @@ struct GetStatusResponse {
     config_capslock: u8,
     config_enable_user_password: u8,
     config_delete_user_password: u8,
-    buf: [u8; 10],
-}
-
-impl ResponseData for GetStatusResponse {
-    fn write_bytes(&self, buf: &mut [u8]) {
-        let card_serial = self.card_serial.to_le_bytes();
-        let data = &[
-            self.firmware_version_minor,
-            self.firmware_version_major,
-            card_serial[0],
-            card_serial[1],
-            card_serial[2],
-            card_serial[3],
-            self.config_numlock,
-            self.config_capslock,
-            self.config_enable_user_password,
-            self.config_delete_user_password,
-        ];
-        assert!(buf.len() >= data.len());
-        buf[..data.len()].copy_from_slice(data);
-    }
 }
 
 #[derive(Debug, Default)]
@@ -97,35 +67,16 @@ impl Command for GetStatusCommand {
     }
 }
 
-#[derive(Debug, Default)]
+#[derive(Debug, Default, Deserialize)]
 struct ReadSlotNameRequest {
     internal_slot_number: u8,
 }
 
-impl RequestData for ReadSlotNameRequest {
-    fn from_bytes(data: &[u8]) -> Option<Self> {
-        if data.is_empty() {
-            None
-        } else {
-            Some(ReadSlotNameRequest {
-                internal_slot_number: data[0],
-            })
-        }
-    }
-}
-
-#[derive(Debug, Default)]
+#[derive(Debug, Default, Serialize)]
 struct ReadSlotNameResponse {
     slot_name: [u8; 15],
 }
 
-impl ResponseData for ReadSlotNameResponse {
-    fn write_bytes(&self, buf: &mut [u8]) {
-        assert!(buf.len() >= self.slot_name.len());
-        buf[..self.slot_name.len()].copy_from_slice(&self.slot_name)
-    }
-}
-
 #[derive(Debug, Default)]
 struct ReadSlotNameCommand {}