Ignore point padding for compressed files

Ignores any potential point padding between the end of the point data and the start of the first elvr if the point format is compressed.

Closes #39

src/reader.rs

@@ -265,18 +265,33 @@ impl<'a> Reader<'a> {
 
         read.seek(SeekFrom::Start(offset_to_end_of_points))?;
         if let Some(evlr) = evlr {
-            match evlr.start_of_first_evlr.cmp(&offset_to_end_of_points) {
-                Ordering::Less => {
-                    return Err(Error::OffsetToEvlrsTooSmall(evlr.start_of_first_evlr).into())
-                }
-                Ordering::Equal => {} // pass
-                Ordering::Greater => {
-                    let n = evlr.start_of_first_evlr - offset_to_end_of_points;
-                    read.by_ref()
-                        .take(n)
-                        .read_to_end(&mut builder.point_padding)?;
+            // Account for any padding between the end of the point data and the start of the ELVRs
+            //
+            // Ignore this case if the point format is compressed.
+            // See https://github.com/gadomski/las-rs/issues/39
+            //
+            // When reading a compressed file, evlr.start_of_first_evlr
+            // is a compressed byte offset, while offset_to_end_of_points
+            // is an uncompressed byte offset, which results in
+            // evlr.start_of_first_evlr < offset_to_end_of_points,
+            //
+            // In this case, we assume that the ELVRs follow the point
+            // record data directly and there is no point_padding to account for.
+            if !builder.point_format.is_compressed {
+                match evlr.start_of_first_evlr.cmp(&offset_to_end_of_points) {
+                    Ordering::Less => {
+                        return Err(Error::OffsetToEvlrsTooSmall(evlr.start_of_first_evlr).into());
+                    }
+                    Ordering::Equal => {} // pass
+                    Ordering::Greater => {
+                        let n = evlr.start_of_first_evlr - offset_to_end_of_points;
+                        read.by_ref()
+                            .take(n)
+                            .read_to_end(&mut builder.point_padding)?;
+                    }
                 }
             }
+            read.seek(SeekFrom::Start(evlr.start_of_first_evlr))?;
             builder
                 .evlrs
                 .push(raw::Vlr::read_from(&mut read, true).map(Vlr::new)?);