Use an io.ReadSeeker instead of an io.Reader to parse feeds

This will allow to make use of func (*Reader) Seek, instead of re-recreating a
new reader. It's a large commit for a small change, but anything to simply the
reader/buffer/ReadAll/… mess is a step in the right direction I think, and it
should enable more follow-up simplifications.

internal/reader/rdf/parser.go

@@ -12,7 +12,7 @@ import (
 )
 
 // Parse returns a normalized feed struct from a RDF feed.
-func Parse(baseURL string, data io.Reader) (*model.Feed, error) {
+func Parse(baseURL string, data io.ReadSeeker) (*model.Feed, error) {
 	feed := new(rdfFeed)
 	if err := xml.NewXMLDecoder(data).Decode(feed); err != nil {
 		return nil, fmt.Errorf("rdf: unable to parse feed: %w", err)

internal/reader/rdf/parser_test.go

@@ -75,7 +75,7 @@ func TestParseRDFSample(t *testing.T) {
 
 	</rdf:RDF>`
 
-	feed, err := Parse("http://xml.com/pub/rdf.xml", bytes.NewBufferString(data))
+	feed, err := Parse("http://xml.com/pub/rdf.xml", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -186,7 +186,7 @@ func TestParseRDFSampleWithDublinCore(t *testing.T) {
 
 	</rdf:RDF>`
 
-	feed, err := Parse("http://meerkat.oreillynet.com/feed.rdf", bytes.NewBufferString(data))
+	feed, err := Parse("http://meerkat.oreillynet.com/feed.rdf", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -253,7 +253,7 @@ func TestParseItemWithOnlyFeedAuthor(t *testing.T) {
 	  </item>
 	</rdf:RDF>`
 
-	feed, err := Parse("http://meerkat.oreillynet.com", bytes.NewBufferString(data))
+	feed, err := Parse("http://meerkat.oreillynet.com", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -278,7 +278,7 @@ func TestParseItemRelativeURL(t *testing.T) {
 	  </item>
 	</rdf:RDF>`
 
-	feed, err := Parse("http://meerkat.oreillynet.com", bytes.NewBufferString(data))
+	feed, err := Parse("http://meerkat.oreillynet.com", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -307,7 +307,7 @@ func TestParseItemWithoutLink(t *testing.T) {
 	  </item>
 	</rdf:RDF>`
 
-	feed, err := Parse("http://meerkat.oreillynet.com", bytes.NewBufferString(data))
+	feed, err := Parse("http://meerkat.oreillynet.com", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -338,7 +338,7 @@ func TestParseItemWithDublicCoreDate(t *testing.T) {
 	  </item>
 	</rdf:RDF>`
 
-	feed, err := Parse("http://example.org", bytes.NewBufferString(data))
+	feed, err := Parse("http://example.org", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -366,7 +366,7 @@ func TestParseItemWithEncodedHTMLInDCCreatorField(t *testing.T) {
 	  </item>
 	</rdf:RDF>`
 
-	feed, err := Parse("http://example.org", bytes.NewBufferString(data))
+	feed, err := Parse("http://example.org", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -392,7 +392,7 @@ func TestParseItemWithoutDate(t *testing.T) {
 	  </item>
 	</rdf:RDF>`
 
-	feed, err := Parse("http://example.org", bytes.NewBufferString(data))
+	feed, err := Parse("http://example.org", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -419,7 +419,7 @@ func TestParseItemWithEncodedHTMLTitle(t *testing.T) {
 	  </item>
 	</rdf:RDF>`
 
-	feed, err := Parse("http://example.org", bytes.NewBufferString(data))
+	feed, err := Parse("http://example.org", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -431,7 +431,7 @@ func TestParseItemWithEncodedHTMLTitle(t *testing.T) {
 
 func TestParseInvalidXml(t *testing.T) {
 	data := `garbage`
-	_, err := Parse("http://example.org", bytes.NewBufferString(data))
+	_, err := Parse("http://example.org", bytes.NewReader([]byte(data)))
 	if err == nil {
 		t.Fatal("Parse should returns an error")
 	}
@@ -446,7 +446,7 @@ func TestParseFeedWithHTMLEntity(t *testing.T) {
 	  </channel>
 	</rdf:RDF>`
 
-	feed, err := Parse("http://example.org", bytes.NewBufferString(data))
+	feed, err := Parse("http://example.org", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -465,7 +465,7 @@ func TestParseFeedWithInvalidCharacterEntity(t *testing.T) {
 	  </channel>
 	</rdf:RDF>`
 
-	feed, err := Parse("http://example.org", bytes.NewBufferString(data))
+	feed, err := Parse("http://example.org", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -521,7 +521,7 @@ func TestParseFeedWithURLWrappedInSpaces(t *testing.T) {
 	</item>
 	</rdf:RDF>`
 
-	feed, err := Parse("http://biorxiv.org", bytes.NewBufferString(data))
+	feed, err := Parse("http://biorxiv.org", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -556,7 +556,7 @@ func TestParseRDFWithContentEncoded(t *testing.T) {
 		</item>
 	</rdf:RDF>`
 
-	feed, err := Parse("http://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("http://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -589,7 +589,7 @@ func TestParseRDFWithEncodedHTMLDescription(t *testing.T) {
 		</item>
 	</rdf:RDF>`
 
-	feed, err := Parse("http://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("http://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -623,7 +623,7 @@ func TestParseRDFItemWithDuplicateTitleElement(t *testing.T) {
 		</item>
 	</rdf:RDF>`
 
-	feed, err := Parse("http://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("http://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -656,7 +656,7 @@ func TestParseRDFItemWithDublinCoreTitleElement(t *testing.T) {
 		</item>
 	</rdf:RDF>`
 
-	feed, err := Parse("http://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("http://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -688,7 +688,7 @@ func TestParseRDFItemWitEmptyTitleElement(t *testing.T) {
 		</item>
 	</rdf:RDF>`
 
-	feed, err := Parse("http://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("http://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}

internal/reader/rss/parser.go

@@ -12,7 +12,7 @@ import (
 )
 
 // Parse returns a normalized feed struct from a RSS feed.
-func Parse(baseURL string, data io.Reader) (*model.Feed, error) {
+func Parse(baseURL string, data io.ReadSeeker) (*model.Feed, error) {
 	feed := new(rssFeed)
 	if err := xml.NewXMLDecoder(data).Decode(feed); err != nil {
 		return nil, fmt.Errorf("rss: unable to parse feed: %w", err)

internal/reader/rss/parser_test.go

@@ -58,7 +58,7 @@ func TestParseRss2Sample(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("http://liftoff.msfc.nasa.gov/rss.xml", bytes.NewBufferString(data))
+	feed, err := Parse("http://liftoff.msfc.nasa.gov/rss.xml", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -117,7 +117,7 @@ func TestParseFeedWithoutTitle(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -138,7 +138,7 @@ func TestParseEntryWithoutTitleAndDescription(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -162,7 +162,7 @@ func TestParseEntryWithoutTitleButWithDescription(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -185,7 +185,7 @@ func TestParseEntryWithMediaTitle(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -207,7 +207,7 @@ func TestParseEntryWithDCTitleOnly(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -228,7 +228,7 @@ func TestParseEntryWithoutLink(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -256,7 +256,7 @@ func TestParseEntryWithOnlyGuidPermalink(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -282,7 +282,7 @@ func TestParseEntryWithAtomLink(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -305,7 +305,7 @@ func TestParseEntryWithMultipleAtomLinks(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -325,7 +325,7 @@ func TestParseFeedURLWithAtomLink(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -353,7 +353,7 @@ func TestParseFeedWithWebmaster(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -380,7 +380,7 @@ func TestParseFeedWithManagingEditor(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -407,7 +407,7 @@ func TestParseEntryWithAuthorAndInnerHTML(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -436,7 +436,7 @@ func TestParseEntryWithAuthorAndCDATA(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -467,7 +467,7 @@ func TestParseEntryWithNonStandardAtomAuthor(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -496,7 +496,7 @@ func TestParseEntryWithAtomAuthorEmail(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -525,7 +525,7 @@ func TestParseEntryWithAtomAuthor(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -551,7 +551,7 @@ func TestParseEntryWithDublinCoreAuthor(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -577,7 +577,7 @@ func TestParseEntryWithItunesAuthor(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -603,7 +603,7 @@ func TestParseFeedWithItunesAuthor(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -632,7 +632,7 @@ func TestParseFeedWithItunesOwner(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -660,7 +660,7 @@ func TestParseFeedWithItunesOwnerEmail(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -686,7 +686,7 @@ func TestParseEntryWithGooglePlayAuthor(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -712,7 +712,7 @@ func TestParseFeedWithGooglePlayAuthor(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -740,7 +740,7 @@ func TestParseEntryWithDublinCoreDate(t *testing.T) {
 				</channel>
 			</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -768,7 +768,7 @@ func TestParseEntryWithContentEncoded(t *testing.T) {
 		</channel>
 	</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -792,7 +792,7 @@ func TestParseEntryWithFeedBurnerLink(t *testing.T) {
 		</channel>
 	</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -818,7 +818,7 @@ func TestParseEntryTitleWithWhitespaces(t *testing.T) {
 	</channel>
 	</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -848,7 +848,7 @@ func TestParseEntryWithEnclosures(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -896,7 +896,7 @@ func TestParseEntryWithEmptyEnclosureURL(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -933,7 +933,7 @@ func TestParseEntryWithFeedBurnerEnclosures(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -974,7 +974,7 @@ func TestParseEntryWithRelativeURL(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1000,7 +1000,7 @@ func TestParseEntryWithCommentsURL(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1025,7 +1025,7 @@ func TestParseEntryWithInvalidCommentsURL(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1037,7 +1037,7 @@ func TestParseEntryWithInvalidCommentsURL(t *testing.T) {
 
 func TestParseInvalidXml(t *testing.T) {
 	data := `garbage`
-	_, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	_, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err == nil {
 		t.Error("Parse should returns an error")
 	}
@@ -1052,7 +1052,7 @@ func TestParseFeedTitleWithHTMLEntity(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1071,7 +1071,7 @@ func TestParseFeedTitleWithUnicodeEntityAndCdata(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1094,7 +1094,7 @@ func TestParseItemTitleWithHTMLEntity(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1117,7 +1117,7 @@ func TestParseItemTitleWithNumericCharacterReference(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1140,7 +1140,7 @@ func TestParseItemTitleWithDoubleEncodedEntities(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1159,7 +1159,7 @@ func TestParseFeedLinkWithInvalidCharacterEntity(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1193,7 +1193,7 @@ func TestParseEntryWithMediaGroup(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1251,7 +1251,7 @@ func TestParseEntryWithMediaContent(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1302,7 +1302,7 @@ func TestParseEntryWithMediaPeerLink(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1354,7 +1354,7 @@ func TestEntryDescriptionFromItunesSummary(t *testing.T) {
 		</channel>
 	</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1385,7 +1385,7 @@ func TestEntryDescriptionFromItunesSubtitle(t *testing.T) {
 		</channel>
 	</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1419,7 +1419,7 @@ func TestEntryDescriptionFromGooglePlayDescription(t *testing.T) {
 		</channel>
 	</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1451,7 +1451,7 @@ func TestParseEntryWithCategoryAndInnerHTML(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1485,7 +1485,7 @@ func TestParseEntryWithCategoryAndCDATA(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1515,7 +1515,7 @@ func TestParseFeedWithTTLField(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1539,7 +1539,7 @@ func TestParseFeedWithIncorrectTTLValue(t *testing.T) {
 		</channel>
 		</rss>`
 
-	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)))
 	if err != nil {
 		t.Fatal(err)
 	}

internal/reader/xml/decoder.go

@@ -14,13 +14,14 @@ import (
 )
 
 // NewXMLDecoder returns a XML decoder that filters illegal characters.
-func NewXMLDecoder(data io.Reader) *xml.Decoder {
+func NewXMLDecoder(data io.ReadSeeker) *xml.Decoder {
 	var decoder *xml.Decoder
 	buffer, _ := io.ReadAll(data)
 	enc := procInst("encoding", string(buffer))
 	if enc != "" && enc != "utf-8" && enc != "UTF-8" && !strings.EqualFold(enc, "utf-8") {
 		// filter invalid chars later within decoder.CharsetReader
-		decoder = xml.NewDecoder(bytes.NewReader(buffer))
+		data.Seek(0, io.SeekStart)
+		decoder = xml.NewDecoder(data)
 	} else {
 		// filter invalid chars now, since decoder.CharsetReader not called for utf-8 content
 		filteredBytes := bytes.Map(filterValidXMLChar, buffer)