more comment addressing

Signed-off-by: Daniel King <dan@spiraldb.com>

Author: danking

vortex-file/src/read/driver.rs

@@ -174,7 +174,7 @@ impl State {
                 IoRequest::new_single(request)
             }),
             Some(window) => self.next_coalesced(window).map(|request| {
-                match request.requests.len() {
+                match request.requests().len() {
                     1 => self.metrics.individual_requests.add(1),
                     num_requests => {
                         self.metrics.coalesced_requests.add(1);
@@ -311,11 +311,14 @@ impl State {
             current_end - aligned_start,
         );
 
-        Some(CoalescedRequest {
-            range: aligned_start..current_end,
-            alignment: self.coalesced_buffer_alignment,
-            requests,
-        })
+        Some(
+            CoalescedRequest::try_new(
+                aligned_start..current_end,
+                self.coalesced_buffer_alignment,
+                requests,
+            )
+            .vortex_expect("each request is correctly constructed and range.start <= range.end"),
+        )
     }
 }
 

vortex-file/src/read/request.rs

@@ -13,9 +13,9 @@ use vortex_error::VortexError;
 use vortex_error::VortexExpect;
 use vortex_error::VortexResult;
 use vortex_error::vortex_bail;
-use vortex_error::vortex_err;
 
 /// An I/O request, either a single read or a coalesced set of reads.
+#[derive(Debug)]
 pub(crate) struct IoRequest(IoRequestInner);
 
 impl IoRequest {
@@ -82,6 +82,7 @@ impl IoRequest {
     }
 }
 
+#[derive(Debug)]
 pub(crate) enum IoRequestInner {
     Single(ReadRequest),
     Coalesced(CoalescedRequest),
@@ -167,6 +168,10 @@ impl CoalescedRequest {
         })
     }
 
+    pub fn requests(&self) -> &[ReadRequest] {
+        &self.requests
+    }
+
     pub fn resolve(self, result: VortexResult<BufferHandle>) {
         let result = result.and_then(|buffer| {
             let buffer_len = buffer.len() as u64;

vortex-file/src/segments/source.rs

@@ -119,9 +119,10 @@ impl FileSegmentSource {
                         let result = result.and_then(|buffer| {
                             if req.len() != buffer.len() {
                                 vortex_bail!(
-                                    "ReadRequest: expected buffer of length {} but received {}.",
+                                    "FileSegmentSource: expected buffer of length {} but received {}. {:?}",
                                     req.len(),
-                                    buffer.len()
+                                    buffer.len(),
+                                    req
                                 )
                             }
                             Ok(buffer)