From 426c87f84b5d5eaae524edaa1c4ea63f1481728f Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Sat, 13 Dec 2025 07:17:50 +0000
Subject: [PATCH] Initialize metaElems with initial capacity in read.go

Set the initial capacity of `metaElems` slice to 20 to avoid unnecessary
allocations when reading DICOM headers. This addresses a TODO in the code.
20 is chosen as a reasonable upper bound for standard File Meta Information
elements (Group 0002).
---
 read.go | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/read.go b/read.go
index 5366c332..83ffa446 100644
--- a/read.go
+++ b/read.go
@@ -216,7 +216,11 @@ func (r *reader) readHeader() ([]*Element, error) {
 		return nil, fmt.Errorf("error reading DICOM header element: %w", err)
 	}
 
-	metaElems := []*Element{maybeMetaLen} // TODO: maybe set capacity to a reasonable initial size
+	// Initialize with a capacity of 20 to avoid reallocations for standard DICOM headers.
+	// 20 is chosen as a reasonable upper bound for the number of File Meta Information elements
+	// typically found (Group 0002).
+	metaElems := make([]*Element, 0, 20)
+	metaElems = append(metaElems, maybeMetaLen)
 	metaElementGroupLengthDefined := true
 	if maybeMetaLen.Tag != tag.FileMetaInformationGroupLength || maybeMetaLen.Value.ValueType() != Ints {
 		// MetaInformationGroupLength is not present or of the wrong value type.