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authorDaniel Schadt <kingdread@gmx.de>2020-10-01 16:27:48 +0200
committerDaniel Schadt <kingdread@gmx.de>2020-10-01 16:27:48 +0200
commitfa3f8e5ce231a5844e59f0d5e1081b5c6f8274c8 (patch)
tree7ec2404fecdc7188a4f0f546dc0895847721309a /src/lib.rs
parent65bd385540db567751405df000f6b063226d8b8a (diff)
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manually implement Deserialize for Agent
The rationale is included in the comment below. The gist is that we want to avoid deserializing Agent<Player> (and others) directly, as that would circumvent the checks. As a small bonus, we now skip the phantom_data field in serialization, as that's just an implementation detail that other consumers shouldn't worry about.
Diffstat (limited to 'src/lib.rs')
-rw-r--r--src/lib.rs157
1 files changed, 156 insertions, 1 deletions
diff --git a/src/lib.rs b/src/lib.rs
index 2dff6a4..5ba6340 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -444,7 +444,7 @@ impl TryFrom<&raw::Agent> for AgentKind {
/// `Kind`. An escape hatch is the method [`.erase()`][Agent::erase], which erases the kind
/// information and produces the default `Agent<()>`. Functions/methods that only take `Agent<()>`
/// can therefore be used by any other agent as well.
-#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[cfg_attr(feature = "serde", derive(serde::Serialize))]
#[derive(Debug, Clone, Hash, PartialEq, Eq, Getters, CopyGetters)]
// For the reasoning of #[repr(C)] see Agent::transmute.
#[repr(C)]
@@ -513,9 +513,164 @@ pub struct Agent<Kind = ()> {
#[get_copy = "pub"]
master_agent: Option<u64>,
+ #[cfg_attr(feature = "serde", serde(skip_serializing))]
phantom_data: PhantomData<Kind>,
}
+// We could derive this, however that would derive Deserialize generically for Agent<T>, where T is
+// deserializable. In particular, this would mean that you could deserialize Agent<Character>,
+// Agent<Player> and Agent<Gadget> directly, which would not be too bad - the problem is that serde
+// has no way of knowing if the serialized agent actually is a character/player/gadget agent, as
+// that information only exists on the type level. This meant that you could "coerce" agents into
+// the wrong type, safely, using a serialization followed by a deserialization.
+// Now this doesn't actually lead to memory unsafety or other bad behaviour, but it could mean that
+// the program would panic if you tried to access a non-existing field, e.g. by calling
+// Agent<Character>::id() on a non-character agent.
+// In order to prevent this, we manually implement Deserialize only for Agent<()>, so that the
+// usual conversion functions with the proper checks have to be used.
+#[cfg(feature = "serde")]
+impl<'de> serde::Deserialize<'de> for Agent {
+ fn deserialize<D: serde::Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
+ use serde::de::{self, Deserialize, Deserializer, MapAccess, SeqAccess, Visitor};
+ use std::fmt;
+
+ #[derive(serde::Deserialize)]
+ #[serde(field_identifier, rename_all = "snake_case")]
+ enum Field {
+ Addr,
+ Kind,
+ Toughness,
+ Concentration,
+ Healing,
+ Condition,
+ InstanceId,
+ FirstAware,
+ LastAware,
+ MasterAgent,
+ };
+
+ struct AgentVisitor;
+
+ impl<'de> Visitor<'de> for AgentVisitor {
+ type Value = Agent;
+
+ fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+ formatter.write_str("struct Agent")
+ }
+
+ fn visit_map<V: MapAccess<'de>>(self, mut map: V) -> Result<Agent, V::Error> {
+ let mut addr = None;
+ let mut kind = None;
+ let mut toughness = None;
+ let mut concentration = None;
+ let mut healing = None;
+ let mut condition = None;
+ let mut instance_id = None;
+ let mut first_aware = None;
+ let mut last_aware = None;
+ let mut master_agent = None;
+
+ while let Some(key) = map.next_key()? {
+ match key {
+ Field::Addr => {
+ if addr.is_some() {
+ return Err(de::Error::duplicate_field("addr"));
+ }
+ addr = Some(map.next_value()?);
+ }
+ Field::Kind => {
+ if kind.is_some() {
+ return Err(de::Error::duplicate_field("kind"));
+ }
+ kind = Some(map.next_value()?);
+ }
+ Field::Toughness => {
+ if toughness.is_some() {
+ return Err(de::Error::duplicate_field("toughness"));
+ }
+ toughness = Some(map.next_value()?);
+ }
+ Field::Concentration => {
+ if concentration.is_some() {
+ return Err(de::Error::duplicate_field("concentration"));
+ }
+ concentration = Some(map.next_value()?);
+ }
+ Field::Healing => {
+ if healing.is_some() {
+ return Err(de::Error::duplicate_field("healing"));
+ }
+ healing = Some(map.next_value()?);
+ }
+ Field::Condition => {
+ if condition.is_some() {
+ return Err(de::Error::duplicate_field("condition"));
+ }
+ condition = Some(map.next_value()?);
+ }
+ Field::InstanceId=> {
+ if instance_id.is_some() {
+ return Err(de::Error::duplicate_field("instance_id"));
+ }
+ instance_id = Some(map.next_value()?);
+ }
+ Field::FirstAware=> {
+ if first_aware.is_some() {
+ return Err(de::Error::duplicate_field("first_aware"));
+ }
+ first_aware = Some(map.next_value()?);
+ }
+ Field::LastAware => {
+ if last_aware.is_some() {
+ return Err(de::Error::duplicate_field("last_aware"));
+ }
+ last_aware = Some(map.next_value()?);
+ }
+ Field::MasterAgent => {
+ if master_agent.is_some() {
+ return Err(de::Error::duplicate_field("master_agent"));
+ }
+ master_agent = Some(map.next_value()?);
+ }
+ }
+ }
+
+ Ok(Agent {
+ addr: addr.ok_or_else(|| de::Error::missing_field("addr"))?,
+ kind: kind.ok_or_else(|| de::Error::missing_field("kind"))?,
+ toughness: toughness.ok_or_else(|| de::Error::missing_field("toughness"))?,
+ concentration: concentration
+ .ok_or_else(|| de::Error::missing_field("concentration"))?,
+ healing: healing.ok_or_else(|| de::Error::missing_field("healing"))?,
+ condition: condition.ok_or_else(|| de::Error::missing_field("condition"))?,
+ instance_id: instance_id
+ .ok_or_else(|| de::Error::missing_field("instance_id"))?,
+ first_aware: first_aware
+ .ok_or_else(|| de::Error::missing_field("first_aware"))?,
+ last_aware: last_aware.ok_or_else(|| de::Error::missing_field("last_aware"))?,
+ master_agent: master_agent
+ .ok_or_else(|| de::Error::missing_field("master_agent"))?,
+ phantom_data: PhantomData,
+ })
+ }
+ };
+
+ const FIELDS: &'static [&'static str] = &[
+ "addr",
+ "kind",
+ "toughness",
+ "concentration",
+ "healing",
+ "condition",
+ "instance_id",
+ "first_aware",
+ "last_aware",
+ "master_agent",
+ ];
+ deserializer.deserialize_struct("Agent", FIELDS, AgentVisitor)
+ }
+}
+
impl TryFrom<&raw::Agent> for Agent {
type Error = EvtcError;