fix: avoid no_std panic in ceil helpers on non-finite input

Byte::from_f64/from_f32 let +inf past the size >= 0.0 guard and then called
the no_std ceil helpers, which used Decimal::from_f64(v).unwrap(). Decimal
conversion returns None for non-finite values, so this panicked in no_std
builds while std returned None. Fall back to the input value for non-finite
input so no_std matches std and the documented None contract is upheld.

src/common.rs

@@ -36,7 +36,13 @@ pub(crate) fn ceil_f64(v: f64) -> f64 {
 pub(crate) fn ceil_f64(v: f64) -> f64 {
     debug_assert!(v >= 0.0);
 
-    Decimal::from_f64(v).unwrap().ceil().to_f64().unwrap()
+    // `Decimal::from_f64` returns `None` for non-finite values (e.g. infinity),
+    // so fall back to the input to mirror `f64::ceil` in the `std` path and
+    // avoid panicking.
+    match Decimal::from_f64(v) {
+        Some(d) => d.ceil().to_f64().unwrap_or(v),
+        None => v,
+    }
 }
 
 #[cfg(any(feature = "byte", feature = "bit"))]
@@ -54,7 +60,13 @@ pub(crate) fn ceil_f32(v: f32) -> f32 {
 pub(crate) fn ceil_f32(v: f32) -> f32 {
     debug_assert!(v >= 0.0);
 
-    Decimal::from_f32(v).unwrap().ceil().to_f32().unwrap()
+    // `Decimal::from_f32` returns `None` for non-finite values (e.g. infinity),
+    // so fall back to the input to mirror `f32::ceil` in the `std` path and
+    // avoid panicking.
+    match Decimal::from_f32(v) {
+        Some(d) => d.ceil().to_f32().unwrap_or(v),
+        None => v,
+    }
 }
 
 #[cfg(any(feature = "byte", feature = "bit"))]

tests/byte.rs

@@ -170,3 +170,13 @@ fn tests() {
         assert_eq!(byte, serde_json::from_str::<Byte>(case.0).unwrap(), "{i}");
     }
 }
+
+#[test]
+fn from_non_finite_returns_none() {
+    // Non-finite inputs are "too large" and must return None instead of
+    // panicking, consistently across the `std` and `no_std` builds.
+    assert_eq!(Byte::from_f64(f64::INFINITY), None);
+    assert_eq!(Byte::from_f64(f64::NAN), None);
+    assert_eq!(Byte::from_f32(f32::INFINITY), None);
+    assert_eq!(Byte::from_f32(f32::NAN), None);
+}