refactor(decode): split god-file into mdds/decode/{error,headers,transport,extract,cell,v3} + lift tdbe::time (refs #500)

CHANGELOG.md

@@ -5,6 +5,25 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [8.0.34] - 2026-05-07
+
+### Changed
+
+- **`crates/thetadatadx/src/decode.rs` (2177 LoC) split into
+  `mdds/decode/{error,headers,transport,extract,cell,v3}` modules.**
+  Pure structural refactor; public API unchanged. Re-exports
+  preserved at `thetadatadx::mdds::decode::*`.
+
+- **Eastern-time + DST primitives lifted to `tdbe::time`.**
+  `eastern_offset_ms`, `march_second_sunday_utc`,
+  `november_first_sunday_utc`, `april_first_sunday_utc`,
+  `october_last_sunday_utc`, `civil_to_epoch_days`,
+  `timestamp_to_ms_of_day`, `timestamp_to_date` — single canonical
+  module reused by mdds, fpss, flatfiles. Patch bump tdbe 0.12.9
+  → 0.12.10.
+
+  Refs #500.
+
 ## [8.0.33] - 2026-05-07
 
 ### Added

crates/tdbe/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "tdbe"
-version = "0.12.9"
+version = "0.12.10"
 edition.workspace = true
 rust-version.workspace = true
 authors.workspace = true

crates/tdbe/src/latency.rs

@@ -4,8 +4,10 @@
 //! (YYYYMMDD) into epoch nanoseconds, then subtracts from the local
 //! `received_at_ns` wall-clock timestamp captured at frame decode time.
 //!
-//! No external timezone crate -- uses the same civil-date math and US DST
-//! rules (Energy Policy Act 2005) as `thetadatadx::decode`.
+//! Civil-date / DST primitives live in [`crate::time`]; this module is a
+//! thin wrapper that adds the YYYYMMDD-and-`ms_of_day` decomposition.
+
+use crate::time::{civil_to_epoch_days, eastern_offset_ms};
 
 /// Compute wire-to-application latency in nanoseconds.
 ///
@@ -52,88 +54,6 @@ fn exchange_epoch_ns(ms_of_day: i32, date_yyyymmdd: i32) -> i64 {
     exchange_epoch_ms * 1_000_000
 }
 
-// ---------------------------------------------------------------------------
-//  Civil-date / DST helpers (same algorithm as thetadatadx::decode)
-// ---------------------------------------------------------------------------
-
-/// Convert civil date to days since 1970-01-01 (Euclidean algorithm).
-// Reason: the Euclidean date algorithm uses intentional signed/unsigned conversions
-// that are safe for all valid calendar dates (year 0..9999).
-#[allow(clippy::cast_sign_loss, clippy::cast_possible_wrap)]
-fn civil_to_epoch_days(year: i32, month: u32, day: u32) -> i64 {
-    let y = if month <= 2 {
-        i64::from(year) - 1
-    } else {
-        i64::from(year)
-    };
-    let m = if month <= 2 {
-        i64::from(month) + 9
-    } else {
-        i64::from(month) - 3
-    };
-    let era = if y >= 0 { y } else { y - 399 } / 400;
-    let yoe = (y - era * 400) as u64;
-    let doy = (153 * m as u64 + 2) / 5 + u64::from(day) - 1;
-    let doe = yoe * 365 + yoe / 4 - yoe / 100 + doy;
-    era * 146_097 + doe as i64 - 719_468
-}
-
-/// Eastern Time UTC offset in milliseconds for a given `epoch_ms`.
-///
-/// US DST rule (Energy Policy Act of 2005):
-/// - EDT (UTC-4): second Sunday of March 2:00 AM local -> first Sunday of November 2:00 AM local
-/// - EST (UTC-5): rest of the year
-// Reason: the Euclidean date algorithm uses intentional signed/unsigned conversions
-// that are safe for all valid epoch timestamps in the market data date range.
-#[allow(
-    clippy::cast_possible_wrap,
-    clippy::cast_sign_loss,
-    clippy::cast_possible_truncation
-)]
-fn eastern_offset_ms(epoch_ms: u64) -> i64 {
-    let epoch_secs = epoch_ms as i64 / 1_000;
-    let days_since_epoch = epoch_secs / 86_400;
-
-    // Civil date from days since 1970-01-01.
-    let z = days_since_epoch + 719_468;
-    let era = if z >= 0 { z } else { z - 146_096 } / 146_097;
-    let doe = (z - era * 146_097) as u32;
-    let yoe = (doe - doe / 1_460 + doe / 36_524 - doe / 146_096) / 365;
-    let year = yoe as i32 + (era * 400) as i32;
-    let doy = doe - (365 * yoe + yoe / 4 - yoe / 100);
-    let mp = (5 * doy + 2) / 153;
-    let month = if mp < 10 { mp + 3 } else { mp - 9 };
-    let year = if month <= 2 { year + 1 } else { year };
-
-    let dst_start_utc = march_second_sunday_utc(year);
-    let dst_end_utc = november_first_sunday_utc(year);
-
-    let epoch_ms_i64 = epoch_ms as i64;
-    if epoch_ms_i64 >= dst_start_utc && epoch_ms_i64 < dst_end_utc {
-        -4 * 3_600 * 1_000 // EDT
-    } else {
-        -5 * 3_600 * 1_000 // EST
-    }
-}
-
-/// Epoch ms of the second Sunday of March at 7:00 AM UTC (= 2:00 AM EST).
-fn march_second_sunday_utc(year: i32) -> i64 {
-    let mar1 = civil_to_epoch_days(year, 3, 1);
-    let dow = ((mar1 + 3) % 7 + 7) % 7; // 0=Mon..6=Sun
-    let days_to_first_sunday = (6 - dow + 7) % 7;
-    let second_sunday = mar1 + days_to_first_sunday + 7;
-    second_sunday * 86_400_000 + 7 * 3_600 * 1_000
-}
-
-/// Epoch ms of the first Sunday of November at 6:00 AM UTC (= 2:00 AM EDT).
-fn november_first_sunday_utc(year: i32) -> i64 {
-    let nov1 = civil_to_epoch_days(year, 11, 1);
-    let dow = ((nov1 + 3) % 7 + 7) % 7;
-    let days_to_first_sunday = (6 - dow + 7) % 7;
-    let first_sunday = nov1 + days_to_first_sunday;
-    first_sunday * 86_400_000 + 6 * 3_600 * 1_000
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;

crates/tdbe/src/lib.rs

@@ -23,6 +23,7 @@ pub mod json_canon;
 pub mod latency;
 pub mod right;
 pub mod sequences;
+pub mod time;
 pub mod types;
 
 // Convenience re-exports at crate root