[GitHub] [arrow-rs] viirya commented on a diff in pull request #1816: Fix Decimal and List ArrayData Validation (#1813) (#1814)

[GitBox <gi...@apache.org>]

viirya commented on code in PR #1816:
URL: https://github.com/apache/arrow-rs/pull/1816#discussion_r891600614


##########
arrow/src/array/data.rs:
##########
@@ -738,40 +738,47 @@ impl ArrayData {
     /// entries.
     ///
     /// For an empty array, the `buffer` can also be empty.
-    fn typed_offsets<'a, T: ArrowNativeType + num::Num + std::fmt::Display>(
-        &'a self,
-        buffer: &'a Buffer,
-    ) -> Result<&'a [T]> {
+    fn typed_offsets<T: ArrowNativeType + num::Num>(&self) -> Result<&[T]> {
         // An empty list-like array can have 0 offsets
-        if buffer.is_empty() && self.len == 0 {
+        if self.len == 0 && self.buffers[0].is_empty() {
             return Ok(&[]);
         }
 
-        // Validate that there are the correct number of offsets for this array's length
-        let required_offsets = self.len + self.offset + 1;
+        self.typed_buffer(0, self.len + 1)
+    }
+
+    /// Returns a reference to the data in `buffer` as a typed slice after validating
+    fn typed_buffer<T: ArrowNativeType + num::Num>(
+        &self,
+        idx: usize,
+        len: usize,
+    ) -> Result<&[T]> {
+        let buffer = &self.buffers[idx];
+
+        let required_len = (len + self.offset) * std::mem::size_of::<T>();
 
-        if (buffer.len() / std::mem::size_of::<T>()) < required_offsets {
+        if buffer.len() < required_len {

Review Comment:
   Hmm, shouldn't it be
   
   ```rust
   let required_len = len * std::mem::size_of::<T>();
   if buffer.len() < required_len {
     ...
   }
   ```
   



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