sodiumdecrypter: Ensure to pull enough data from upstream if not starting on a chunk boundary

We round down to the previous chunk boundary, but then we also have to
add the difference between the offset of that chunk to the requested
offset to the size of the buffer that is pulled from upstream. Otherwise
there will be an unneeded short read, which could cause downstream to
EOS too early.

gst-plugin-sodium/src/decrypter.rs

@@ -538,19 +538,26 @@ impl Decrypter {
         let chunk_index = offset as u64 / block_size as u64;
         gst_debug!(CAT, obj: pad, "Stream Block index: {}", chunk_index);
 
-        let buffer =
-            self.pull_requested_buffer(pad, element, requested_size, block_size, chunk_index)?;
+        let pull_offset = offset - (chunk_index * block_size as u64);
+        assert!(pull_offset <= std::u32::MAX as u64);
+        let pull_offset = pull_offset as u32;
+
+        let buffer = self.pull_requested_buffer(
+            pad,
+            element,
+            requested_size + pull_offset,
+            block_size,
+            chunk_index,
+        )?;
 
         let mut state = self.state.lock().unwrap();
         // This will only be run after READY state,
         // and will be guaranted to be initialized
         let state = state.as_mut().unwrap();
 
-        let adapter_offset = offset - (chunk_index * block_size as u64);
-        assert!(adapter_offset <= std::usize::MAX as u64);
-        let adapter_offset = adapter_offset as usize;
-
         state.decrypt_into_adapter(element, &self.srcpad, &buffer, chunk_index)?;
+
+        let adapter_offset = pull_offset as usize;
         state.get_requested_buffer(&self.srcpad, requested_size, adapter_offset)
     }
 }