Bootstrap OpenBitdo clean-room SDK and reliability milestone

sdk/crates/bitdo_proto/src/profile.rs

@@ -0,0 +1,63 @@
+use crate::error::{BitdoError, Result};
+use serde::{Deserialize, Serialize};
+
+const MAGIC: &[u8; 4] = b"BDP1";
+
+#[derive(Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
+pub struct ProfileBlob {
+    pub slot: u8,
+    pub payload: Vec<u8>,
+}
+
+impl ProfileBlob {
+    pub fn to_bytes(&self) -> Vec<u8> {
+        let mut out = Vec::with_capacity(4 + 1 + 2 + self.payload.len() + 4);
+        out.extend_from_slice(MAGIC);
+        out.push(self.slot);
+        out.extend_from_slice(&(self.payload.len() as u16).to_le_bytes());
+        out.extend_from_slice(&self.payload);
+        let checksum = checksum(&out[4..]);
+        out.extend_from_slice(&checksum.to_le_bytes());
+        out
+    }
+
+    pub fn from_bytes(data: &[u8]) -> Result<Self> {
+        if data.len() < 11 {
+            return Err(BitdoError::InvalidInput(
+                "profile blob too short".to_owned(),
+            ));
+        }
+        if &data[0..4] != MAGIC {
+            return Err(BitdoError::InvalidInput("invalid profile magic".to_owned()));
+        }
+
+        let slot = data[4];
+        let len = u16::from_le_bytes([data[5], data[6]]) as usize;
+        let payload_end = 7 + len;
+        if payload_end + 4 > data.len() {
+            return Err(BitdoError::InvalidInput(
+                "profile length exceeds blob size".to_owned(),
+            ));
+        }
+
+        let payload = data[7..payload_end].to_vec();
+        let expected = u32::from_le_bytes([
+            data[payload_end],
+            data[payload_end + 1],
+            data[payload_end + 2],
+            data[payload_end + 3],
+        ]);
+        let actual = checksum(&data[4..payload_end]);
+        if expected != actual {
+            return Err(BitdoError::InvalidInput(format!(
+                "checksum mismatch expected={expected:#x} actual={actual:#x}"
+            )));
+        }
+
+        Ok(Self { slot, payload })
+    }
+}
+
+fn checksum(data: &[u8]) -> u32 {
+    data.iter().fold(0u32, |acc, b| acc.wrapping_add(*b as u32))
+}