FIX: bug in offset() calculation

cehteh · cehteh · commit 25788c1a8257 · 2025-02-18T04:45:10.000+01:00
Off-By-One error when rouding to the next offset.
I totally missed that a bug slipped into the offset calculation because
I only tested with u8 and i32 data.
diff --git a/src/lib.rs b/src/lib.rs
@@ -381,7 +381,7 @@ impl<H, T> HeaderVec<H, T> {
     const fn offset() -> usize {
         // The first location, in units of size_of::<T>(), that is after the header
         // It's the end of the header, rounded up to the nearest size_of::<T>()
-        mem::size_of::<AlignedHeader<H, T>>() / mem::size_of::<T>()
+        (mem::size_of::<AlignedHeader<H, T>>()-1) / mem::size_of::<T>() + 1
     }
 
     /// Compute the number of elements (in units of T) to allocate for a given capacity.

Original file line number	Diff line number	Diff line change
`@@ -381,7 +381,7 @@ impl<H, T> HeaderVec<H, T> {`
`381`	`381`	`const fn offset() -> usize {`
`382`	`382`	`// The first location, in units of size_of::<T>(), that is after the header`
`383`	`383`	`// It's the end of the header, rounded up to the nearest size_of::<T>()`
`384`		`- mem::size_of::<AlignedHeader<H, T>>() / mem::size_of::<T>()`
	`384`	`+ (mem::size_of::<AlignedHeader<H, T>>()-1) / mem::size_of::<T>() + 1`
`385`	`385`	`}`
`386`	`386`
`387`	`387`	`/// Compute the number of elements (in units of T) to allocate for a given capacity.`