From bb750f079954f4e4b290cc6aed7bcb5e53e5ba9b Mon Sep 17 00:00:00 2001
From: Lucas Nogueira <lnogueir@uwaterloo.ca>
Date: Wed, 29 May 2024 17:39:49 -0400
Subject: [PATCH] Improve comment about magic word not present. (#318)

---
 read.go | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/read.go b/read.go
index fe610eb3..eb45cc92 100644
--- a/read.go
+++ b/read.go
@@ -151,15 +151,17 @@ func (r *reader) readValue(t tag.Tag, vr string, vl uint32, isImplicit bool, d *
 // readHeader reads the DICOM magic header and group two metadata elements.
 // This should only be called once per DICOM at the start of parsing.
 func (r *reader) readHeader() ([]*Element, error) {
-	// Check to see if magic word is at byte offset 128. If not, this is a
-	// non-standard non-compliant DICOM. We try to read this DICOM in a
-	// compatibility mode, where we rewind to position 0 and blindly attempt to
-	// parse a Dataset (and do not parse metadata in the usual way).
+	// Check for Preamble (128 bytes) + magic word (4 bytes).
 	data, err := r.rawReader.Peek(128 + 4)
 	if err != nil {
 		return nil, err
 	}
 	if string(data[128:]) != magicWord {
+		// If magic word is not at byte offset 128 this is a non-standard
+		// non-compliant DICOM. We try to read this DICOM in a compatibility
+		// mode, where we rewind to position 0 and blindly attempt to parse
+		// a Dataset (and do not parse metadata in the usual way), which is
+		// why we return nil error.
 		return nil, nil
 	}