From e710f1e5e2faafa9684d335e233592dbc277bf35 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kevin=20L=C3=A4ufer?= <laeufer@cs.berkeley.edu>
Date: Thu, 9 Nov 2023 09:48:40 -0500
Subject: [PATCH] load timescale from fst

---
 Cargo.toml       |  2 +-
 src/fst.rs       | 34 ++++++++++++++++++++++++++++++----
 src/hierarchy.rs |  9 +++++++--
 src/vcd.rs       |  3 ++-
 4 files changed, 40 insertions(+), 8 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index d5c90ed..af95f79 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -12,7 +12,7 @@ edition = "2021"
 [dependencies]
 bytesize = "1.3.0"
 clap = { version = "4.4.6", features = ["derive"] }
-fst-native = "0.6.0"
+fst-native = "0.6.3"
 leb128 = "0.2.5"
 lz4_flex = "0.11.1"
 memmap2 = "0.9.0"
diff --git a/src/fst.rs b/src/fst.rs
index 4df4783..8c98a65 100644
--- a/src/fst.rs
+++ b/src/fst.rs
@@ -90,9 +90,35 @@ fn convert_var_direction(tpe: FstVarDirection) -> VarDirection {
     }
 }
 
-// fn convert_timescale_unit() -> TimescaleUnit {
-//
-// }
+fn convert_timescale(exponent: i8) -> Timescale {
+    if exponent >= 0 {
+        Timescale::new(10u32.pow(exponent as u32), TimescaleUnit::Seconds)
+    } else if exponent >= -3 {
+        Timescale::new(
+            10u32.pow((exponent + 3) as u32),
+            TimescaleUnit::MilliSeconds,
+        )
+    } else if exponent >= -6 {
+        Timescale::new(
+            10u32.pow((exponent + 6) as u32),
+            TimescaleUnit::MicroSeconds,
+        )
+    } else if exponent >= -9 {
+        Timescale::new(10u32.pow((exponent + 9) as u32), TimescaleUnit::NanoSeconds)
+    } else if exponent >= -12 {
+        Timescale::new(
+            10u32.pow((exponent + 12) as u32),
+            TimescaleUnit::PicoSeconds,
+        )
+    } else if exponent >= -15 {
+        Timescale::new(
+            10u32.pow((exponent + 15) as u32),
+            TimescaleUnit::FemtoSeconds,
+        )
+    } else {
+        panic!("Unexpected timescale exponent: {}", exponent);
+    }
+}
 
 fn read_hierarchy<F: BufRead + Seek>(reader: &mut FstReader<F>) -> Hierarchy {
     let mut h = HierarchyBuilder::default();
@@ -100,7 +126,7 @@ fn read_hierarchy<F: BufRead + Seek>(reader: &mut FstReader<F>) -> Hierarchy {
     let fst_header = reader.get_header();
     h.set_version(fst_header.version.trim().to_string());
     h.set_date(fst_header.date.trim().to_string());
-    //TODO: h.set_timescale( Timescale { factor: 0, unit: convert_timescale_unit(fst_header.) } );
+    h.set_timescale(convert_timescale(fst_header.timescale_exponent));
 
     let mut path_names = HashMap::new();
 
diff --git a/src/hierarchy.rs b/src/hierarchy.rs
index 76c59d1..01cf1f0 100644
--- a/src/hierarchy.rs
+++ b/src/hierarchy.rs
@@ -14,6 +14,12 @@ pub struct Timescale {
     pub unit: TimescaleUnit,
 }
 
+impl Timescale {
+    pub fn new(factor: u32, unit: TimescaleUnit) -> Self {
+        Timescale { factor, unit }
+    }
+}
+
 #[derive(Debug, Clone, Copy, PartialEq)]
 pub enum TimescaleUnit {
     FemtoSeconds,
@@ -682,8 +688,7 @@ impl HierarchyBuilder {
         self.meta.version = value;
     }
 
-    pub fn set_timescale(&mut self, factor: u32, unit: TimescaleUnit) {
-        let value = Timescale { factor, unit };
+    pub fn set_timescale(&mut self, value: Timescale) {
         assert!(
             self.meta.timescale.is_none(),
             "Duplicate timescales: {:?} vs {:?}",
diff --git a/src/vcd.rs b/src/vcd.rs
index b1bd874..0d752ef 100644
--- a/src/vcd.rs
+++ b/src/vcd.rs
@@ -104,7 +104,8 @@ fn read_hierarchy(input: &mut (impl BufRead + Seek)) -> (usize, Hierarchy) {
         }
         HeaderCmd::Timescale(factor, unit) => {
             let factor_int = u32::from_str_radix(std::str::from_utf8(factor).unwrap(), 10).unwrap();
-            h.set_timescale(factor_int, convert_timescale_unit(unit));
+            let value = Timescale::new(factor_int, convert_timescale_unit(unit));
+            h.set_timescale(value);
         }
     };