add initial code to support max latency

Author: cctdaniel

program/c/src/oracle/oracle.h

@@ -195,8 +195,9 @@ typedef struct pc_price
   pc_ema_t        twac_;              // time-weighted average conf interval
   int64_t         timestamp_;         // unix timestamp of aggregate price
   uint8_t         min_pub_;           // min publishers for valid price
-  int8_t          drv2_;              // space for future derived values
-  int16_t         drv3_;              // space for future derived values
+  int8_t          message_sent_;      // flag to indicate if the current aggregate price has been sent as a message to the message buffer, 0 if not sent, 1 if sent
+  uint8_t         max_latency_;       // configurable max latency in slots between send and receive
+  int8_t          drv3_;              // space for future derived values
   int32_t         drv4_;              // space for future derived values
   pc_pub_key_t    prod_;              // product id/ref-account
   pc_pub_key_t    next_;              // next price account in list

program/c/src/oracle/upd_aggregate.h

@@ -175,7 +175,7 @@ static inline bool upd_aggregate( pc_price_t *ptr, uint64_t slot, int64_t timest
            // No overflow for INT64_MIN+conf or INT64_MAX-conf as 0 < conf < INT64_MAX
            // These checks ensure that price - conf and price + conf do not overflow.
            (int64_t)0 < conf && (INT64_MIN + conf) <= price && price <= (INT64_MAX-conf) &&
-           slot_diff >= 0 && slot_diff <= PC_MAX_SEND_LATENCY ) {
+           slot_diff <= (ptr->max_latency_ ? ptr->max_latency_ : PC_MAX_SEND_LATENCY) ) {
         numv += 1;
         prcs[ nprcs++ ] = price - conf;
         prcs[ nprcs++ ] = price;

program/rust/src/accounts/price.rs

@@ -65,7 +65,10 @@ mod price_pythnet {
         /// Minimum valid publisher quotes for a succesful aggregation
         pub min_pub_:           u8,
         pub message_sent_:      u8,
-        pub unused_2_:          i16,
+        /// Configurable max latency in slots between send and receive
+        pub max_latency_:       u8,
+        /// Unused placeholder for alignment
+        pub unused_2_:          i8,
         pub unused_3_:          i32,
         /// Corresponding product account
         pub product_account:    Pubkey,
@@ -116,6 +119,7 @@ mod price_pythnet {
                     self.agg_.price_,
                     self.agg_.conf_,
                     self.agg_.pub_slot_.saturating_sub(self.prev_slot_),
+                    self.max_latency_,
                 ); // pub_slot should always be >= prev_slot, but we protect ourselves against underflow just in case
                 Ok(())
             } else {
@@ -172,11 +176,13 @@ mod price_pythnet {
     }
 
     impl PriceCumulative {
-        pub fn update(&mut self, price: i64, conf: u64, slot_gap: u64) {
+        pub fn update(&mut self, price: i64, conf: u64, slot_gap: u64, max_latency: i16) {
             self.price += i128::from(price) * i128::from(slot_gap);
             self.conf += u128::from(conf) * u128::from(slot_gap);
+            // Use PC_MAX_SEND_LATENCY if max_latency is 0, otherwise use max_latency
+            let latency = if max_latency == 0 { PC_MAX_SEND_LATENCY.into() } else { max_latency.into() };
             // This is expected to saturate at 0 most of the time (while the feed is up).
-            self.num_down_slots += slot_gap.saturating_sub(PC_MAX_SEND_LATENCY.into());
+            self.num_down_slots += slot_gap.saturating_sub(latency as u64);
         }
     }
 }
@@ -225,7 +231,10 @@ mod price_solana {
         /// Whether the current aggregate price has been sent as a message to the message buffer.
         /// 0 = false, 1 = true. (this is a u8 to make the Pod trait happy)
         pub message_sent_:      u8,
-        pub unused_2_:          i16,
+        /// Configurable max latency in slots between send and receive
+        pub max_latency_:       u8,
+        /// Unused placeholder for alignment
+        pub unused_2_:          i8,
         pub unused_3_:          i32,
         /// Corresponding product account
         pub product_account:    Pubkey,