diff --git a/internal/charset/charset.go b/internal/charset/charset.go
index 380357f..d1ccdd1 100644
--- a/internal/charset/charset.go
+++ b/internal/charset/charset.go
@@ -29,7 +29,7 @@ var (
 	}
 
 	// https://github.com/file/file/blob/fa93fb9f7d21935f1c7644c47d2975d31f12b812/src/encoding.c#L241
-	textChars [256]byte = [256]byte{
+	textChars = [256]byte{
 		/*                  BEL BS HT LF VT FF CR    */
 		F, F, F, F, F, F, F, T, T, T, T, T, T, T, F, F, /* 0x0X */
 		/*                              ESC          */
diff --git a/internal/json/json.go b/internal/json/json.go
index 683b159..ee39349 100644
--- a/internal/json/json.go
+++ b/internal/json/json.go
@@ -74,7 +74,7 @@ type (
 )
 
 // Scan returns the number of bytes scanned and if there was any error
-// in trying to reach the end of data
+// in trying to reach the end of data.
 func Scan(data []byte) (int, error) {
 	s := &scanner{}
 	_ = checkValid(data, s)
diff --git a/internal/magic/archive.go b/internal/magic/archive.go
index 8f5ff87..b4a1702 100644
--- a/internal/magic/archive.go
+++ b/internal/magic/archive.go
@@ -37,6 +37,12 @@ var (
 	Xz = prefix([]byte{0xFD, 0x37, 0x7A, 0x58, 0x5A, 0x00})
 	// Lzip matches an Lzip compressed file.
 	Lzip = prefix([]byte{0x4c, 0x5a, 0x49, 0x50})
+	// RPM matches an RPM or Delta RPM package file.
+	RPM = prefix([]byte{0xed, 0xab, 0xee, 0xdb}, []byte("drpm"))
+	// Cpio matches a cpio archive file.
+	Cpio = prefix([]byte("070707"), []byte("070701"), []byte("070702"))
+	// RAR matches a RAR archive file.
+	RAR = prefix([]byte("Rar!\x1A\x07\x00"), []byte("Rar!\x1A\x07\x01\x00"))
 )
 
 // Zstd matches a Zstandard archive file.
@@ -46,27 +52,8 @@ func Zstd(raw []byte, limit uint32) bool {
 		bytes.HasPrefix(raw[1:], []byte{0xB5, 0x2F, 0xFD})
 }
 
-// Rpm matches an RPM or Delta RPM package file.
-func Rpm(raw []byte, limit uint32) bool {
-	return bytes.HasPrefix(raw, []byte{0xed, 0xab, 0xee, 0xdb}) ||
-		bytes.HasPrefix(raw, []byte("drpm"))
-}
-
-// Cpio matches a cpio archive file.
-func Cpio(raw []byte, limit uint32) bool {
-	return bytes.HasPrefix(raw, []byte("070707")) ||
-		bytes.HasPrefix(raw, []byte("070701")) ||
-		bytes.HasPrefix(raw, []byte("070702"))
-}
-
-// Rar matches a RAR archive file.
-func Rar(raw []byte, limit uint32) bool {
-	return bytes.HasPrefix(raw, []byte("Rar!\x1A\x07\x00")) ||
-		bytes.HasPrefix(raw, []byte("Rar!\x1A\x07\x01\x00"))
-}
-
-// Crx matches a Chrome extension file: a zip archive prepended by a package header.
-func Crx(raw []byte, limit uint32) bool {
+// CRX matches a Chrome extension file: a zip archive prepended by a package header.
+func CRX(raw []byte, limit uint32) bool {
 	const minHeaderLen = 16
 	if len(raw) < minHeaderLen || !bytes.HasPrefix(raw, []byte("Cr24")) {
 		return false
diff --git a/internal/magic/audio.go b/internal/magic/audio.go
index ca3c833..d17e324 100644
--- a/internal/magic/audio.go
+++ b/internal/magic/audio.go
@@ -22,6 +22,8 @@ var (
 	Voc = prefix([]byte("Creative Voice File"))
 	// M3u matches a Playlist file.
 	M3u = prefix([]byte("#EXTM3U"))
+	// AAC matches an Advanced Audio Coding file.
+	AAC = prefix([]byte{0xFF, 0xF1}, []byte{0xFF, 0xF9})
 )
 
 // Mp3 matches an mp3 file.
@@ -52,24 +54,18 @@ func Mp3(raw []byte, limit uint32) bool {
 	return false
 }
 
-// Aac matches an Advanced Audio Coding file.
-func Aac(raw []byte, limit uint32) bool {
-	return bytes.HasPrefix(raw, []byte{0xFF, 0xF1}) ||
-		bytes.HasPrefix(raw, []byte{0xFF, 0xF9})
-}
-
 // Wav matches a Waveform Audio File Format file.
 func Wav(raw []byte, limit uint32) bool {
 	return len(raw) > 12 &&
 		bytes.Equal(raw[:4], []byte("RIFF")) &&
-		bytes.Equal(raw[8:12], []byte("\x57\x41\x56\x45"))
+		bytes.Equal(raw[8:12], []byte{0x57, 0x41, 0x56, 0x45})
 }
 
 // Aiff matches Audio Interchange File Format file.
 func Aiff(raw []byte, limit uint32) bool {
 	return len(raw) > 12 &&
-		bytes.Equal(raw[:4], []byte("\x46\x4F\x52\x4D")) &&
-		bytes.Equal(raw[8:12], []byte("\x41\x49\x46\x46"))
+		bytes.Equal(raw[:4], []byte{0x46, 0x4F, 0x52, 0x4D}) &&
+		bytes.Equal(raw[8:12], []byte{0x41, 0x49, 0x46, 0x46})
 }
 
 // Qcp matches a Qualcomm Pure Voice file.
diff --git a/internal/magic/binary.go b/internal/magic/binary.go
index 3419dcf..feca467 100644
--- a/internal/magic/binary.go
+++ b/internal/magic/binary.go
@@ -19,6 +19,10 @@ var (
 	Nes = prefix([]byte{0x4E, 0x45, 0x53, 0x1A})
 	// TzIf matches a Time Zone Information Format (TZif) file.
 	TzIf = prefix([]byte("TZif"))
+	// SWF matches an Adobe Flash swf file.
+	SWF = prefix([]byte("CWS"), []byte("FWS"), []byte("ZWS"))
+	// Torrent has bencoded text in the beginning.
+	Torrent = prefix([]byte("d8:announce"))
 )
 
 // Java bytecode and Mach-O binaries share the same magic number.
@@ -57,13 +61,6 @@ func MachO(raw []byte, limit uint32) bool {
 		le == macho.Magic64
 }
 
-// Swf matches an Adobe Flash swf file.
-func Swf(raw []byte, limit uint32) bool {
-	return bytes.HasPrefix(raw, []byte("CWS")) ||
-		bytes.HasPrefix(raw, []byte("FWS")) ||
-		bytes.HasPrefix(raw, []byte("ZWS"))
-}
-
 // Dbf matches a dBase file.
 // https://www.dbase.com/Knowledgebase/INT/db7_file_fmt.htm
 func Dbf(raw []byte, limit uint32) bool {
@@ -142,3 +139,19 @@ func Marc(raw []byte, limit uint32) bool {
 	// Field terminator is present in first 2048 bytes.
 	return bytes.Contains(raw[:min(2048, len(raw))], []byte{0x1E})
 }
+
+// Glb matches a glTF model format file.
+// GLB is the binary file format representation of 3D models save in
+// the GL transmission Format (glTF).
+// see more: https://docs.fileformat.com/3d/glb/
+//           https://www.iana.org/assignments/media-types/model/gltf-binary
+// GLB file format is based on little endian and its header structure
+// show  below:
+//
+// <-- 12-byte header                             -->
+// | magic            | version          | length   |
+// | (uint32)         | (uint32)         | (uint32) |
+// | \x67\x6C\x54\x46 | \x01\x00\x00\x00 | ...      |
+// | g   l   T   F    | 1                | ...      |
+var Glb = prefix([]byte("\x67\x6C\x54\x46\x02\x00\x00\x00"),
+	[]byte("\x67\x6C\x54\x46\x01\x00\x00\x00"))
diff --git a/internal/magic/model.go b/internal/magic/model.go
deleted file mode 100644
index 687effa..0000000
--- a/internal/magic/model.go
+++ /dev/null
@@ -1,17 +0,0 @@
-package magic
-
-// Glb matches a glTF model format file.
-// GLB is the binary file format representation of 3D models save in
-// the GL transmission Format (glTF).
-// see more: https://docs.fileformat.com/3d/glb/
-//           https://www.iana.org/assignments/media-types/model/gltf-binary
-// GLB file format is based on little endian and its header structure
-// show  below:
-//
-// <-- 12-byte header                             -->
-// | magic            | version          | length   |
-// | (uint32)         | (uint32)         | (uint32) |
-// | \x67\x6C\x54\x46 | \x01\x00\x00\x00 | ...      |
-// | g   l   T   F    | 1                | ...      |
-var Glb = prefix([]byte("\x67\x6C\x54\x46\x02\x00\x00\x00"),
-	[]byte("\x67\x6C\x54\x46\x01\x00\x00\x00"))
diff --git a/internal/magic/signature.go b/internal/magic/signature.go
index 0cb5359..abab040 100644
--- a/internal/magic/signature.go
+++ b/internal/magic/signature.go
@@ -1,4 +1,4 @@
-// package magic holds the matching functions used to find MIME types.
+// Package magic holds the matching functions used to find MIME types.
 package magic
 
 import (
@@ -7,6 +7,10 @@ import (
 )
 
 type (
+	// Detector receiveѕ the raw data of a file and returns whether the data
+	// meets any conditions. The limit parameter is an upper limit to the number
+	// of bytes received and is used to tell if the byte slice represents the
+	// whole file or is just the header of a file: len(raw) < limit or len(raw)>limit.
 	Detector func(raw []byte, limit uint32) bool
 	xmlSig   struct {
 		// the local name of the root tag
@@ -151,7 +155,7 @@ func ftyp(sigs ...[]byte) Detector {
 	}
 }
 
-func newXmlSig(localName, xmlns string) xmlSig {
+func newXMLSig(localName, xmlns string) xmlSig {
 	ret := xmlSig{xmlns: []byte(xmlns)}
 	if localName != "" {
 		ret.localName = []byte(fmt.Sprintf("<%s", localName))
diff --git a/internal/magic/text.go b/internal/magic/text.go
index dff756c..db5ff5a 100644
--- a/internal/magic/text.go
+++ b/internal/magic/text.go
@@ -9,8 +9,8 @@ import (
 )
 
 var (
-	// Html matches a Hypertext Markup Language file.
-	Html = markup(
+	// HTML matches a Hypertext Markup Language file.
+	HTML = markup(
 		[]byte("<!DOCTYPE HTML"),
 		[]byte("<HTML"),
 		[]byte("<HEAD"),
@@ -29,43 +29,43 @@ var (
 		[]byte("<P"),
 		[]byte("<!--"),
 	)
-	// Xml matches an Extensible Markup Language file.
-	Xml = markup([]byte("<?XML"))
+	// XML matches an Extensible Markup Language file.
+	XML = markup([]byte("<?XML"))
 	// Owl2 matches an Owl ontology file.
-	Owl2 = xml(newXmlSig("Ontology", `xmlns="http://www.w3.org/2002/07/owl#"`))
+	Owl2 = xml(newXMLSig("Ontology", `xmlns="http://www.w3.org/2002/07/owl#"`))
 	// Rss matches a Rich Site Summary file.
-	Rss = xml(newXmlSig("rss", ""))
+	Rss = xml(newXMLSig("rss", ""))
 	// Atom matches an Atom Syndication Format file.
-	Atom = xml(newXmlSig("feed", `xmlns="http://www.w3.org/2005/Atom"`))
+	Atom = xml(newXMLSig("feed", `xmlns="http://www.w3.org/2005/Atom"`))
 	// Kml matches a Keyhole Markup Language file.
 	Kml = xml(
-		newXmlSig("kml", `xmlns="http://www.opengis.net/kml/2.2"`),
-		newXmlSig("kml", `xmlns="http://earth.google.com/kml/2.0"`),
-		newXmlSig("kml", `xmlns="http://earth.google.com/kml/2.1"`),
-		newXmlSig("kml", `xmlns="http://earth.google.com/kml/2.2"`),
+		newXMLSig("kml", `xmlns="http://www.opengis.net/kml/2.2"`),
+		newXMLSig("kml", `xmlns="http://earth.google.com/kml/2.0"`),
+		newXMLSig("kml", `xmlns="http://earth.google.com/kml/2.1"`),
+		newXMLSig("kml", `xmlns="http://earth.google.com/kml/2.2"`),
 	)
 	// Xliff matches a XML Localization Interchange File Format file.
-	Xliff = xml(newXmlSig("xliff", `xmlns="urn:oasis:names:tc:xliff:document:1.2"`))
+	Xliff = xml(newXMLSig("xliff", `xmlns="urn:oasis:names:tc:xliff:document:1.2"`))
 	// Collada matches a COLLAborative Design Activity file.
-	Collada = xml(newXmlSig("COLLADA", `xmlns="http://www.collada.org/2005/11/COLLADASchema"`))
+	Collada = xml(newXMLSig("COLLADA", `xmlns="http://www.collada.org/2005/11/COLLADASchema"`))
 	// Gml matches a Geography Markup Language file.
 	Gml = xml(
-		newXmlSig("", `xmlns:gml="http://www.opengis.net/gml"`),
-		newXmlSig("", `xmlns:gml="http://www.opengis.net/gml/3.2"`),
-		newXmlSig("", `xmlns:gml="http://www.opengis.net/gml/3.3/exr"`),
+		newXMLSig("", `xmlns:gml="http://www.opengis.net/gml"`),
+		newXMLSig("", `xmlns:gml="http://www.opengis.net/gml/3.2"`),
+		newXMLSig("", `xmlns:gml="http://www.opengis.net/gml/3.3/exr"`),
 	)
 	// Gpx matches a GPS Exchange Format file.
-	Gpx = xml(newXmlSig("gpx", `xmlns="http://www.topografix.com/GPX/1/1"`))
+	Gpx = xml(newXMLSig("gpx", `xmlns="http://www.topografix.com/GPX/1/1"`))
 	// Tcx matches a Training Center XML file.
-	Tcx = xml(newXmlSig("TrainingCenterDatabase", `xmlns="http://www.garmin.com/xmlschemas/TrainingCenterDatabase/v2"`))
+	Tcx = xml(newXMLSig("TrainingCenterDatabase", `xmlns="http://www.garmin.com/xmlschemas/TrainingCenterDatabase/v2"`))
 	// X3d matches an Extensible 3D Graphics file.
-	X3d = xml(newXmlSig("X3D", `xmlns:xsd="http://www.w3.org/2001/XMLSchema-instance"`))
+	X3d = xml(newXMLSig("X3D", `xmlns:xsd="http://www.w3.org/2001/XMLSchema-instance"`))
 	// Amf matches an Additive Manufacturing XML file.
-	Amf = xml(newXmlSig("amf", ""))
+	Amf = xml(newXMLSig("amf", ""))
 	// Threemf matches a 3D Manufacturing Format file.
-	Threemf = xml(newXmlSig("model", `xmlns="http://schemas.microsoft.com/3dmanufacturing/core/2015/02"`))
+	Threemf = xml(newXMLSig("model", `xmlns="http://schemas.microsoft.com/3dmanufacturing/core/2015/02"`))
 	// Xfdf matches a XML Forms Data Format file.
-	Xfdf = xml(newXmlSig("xfdf", `xmlns="http://ns.adobe.com/xfdf/"`))
+	Xfdf = xml(newXMLSig("xfdf", `xmlns="http://ns.adobe.com/xfdf/"`))
 	// VCard matches a Virtual Contact File.
 	VCard = ciPrefix([]byte("BEGIN:VCARD\n"), []byte("BEGIN:VCARD\r\n"))
 	// ICalendar matches a iCalendar file.
@@ -253,7 +253,7 @@ func NdJSON(raw []byte, limit uint32) bool {
 	return lCount > 1 && hasObjOrArr
 }
 
-// Har matches a HAR Spec file.
+// HAR matches a HAR Spec file.
 // Spec: http://www.softwareishard.com/blog/har-12-spec/
 func HAR(raw []byte, limit uint32) bool {
 	s := []byte(`"log"`)
@@ -279,12 +279,12 @@ func HAR(raw []byte, limit uint32) bool {
 	// Skip any whitespace after the colon.
 	raw = trimLWS(raw[1:])
 
-	harJsonTypes := [][]byte{
+	harJSONTypes := [][]byte{
 		[]byte(`"version"`),
 		[]byte(`"creator"`),
 		[]byte(`"entries"`),
 	}
-	for _, t := range harJsonTypes {
+	for _, t := range harJSONTypes {
 		si := bytes.Index(raw, t)
 		if si > -1 {
 			return true
diff --git a/internal/magic/torrent.go b/internal/magic/torrent.go
deleted file mode 100644
index ca6a5c9..0000000
--- a/internal/magic/torrent.go
+++ /dev/null
@@ -1,4 +0,0 @@
-package magic
-
-// Torrent has bencoded text in the beginning.
-var Torrent = prefix([]byte("d8:announce"))
diff --git a/mime.go b/mime.go
index 51dc4cd..e5a1c4e 100644
--- a/mime.go
+++ b/mime.go
@@ -70,7 +70,6 @@ func newMIME(
 	mime, extension string,
 	detector magic.Detector,
 	children ...*MIME) *MIME {
-
 	m := &MIME{
 		mime:      mime,
 		extension: extension,
diff --git a/mimetype.go b/mimetype.go
index 61f1fbe..08e68e3 100644
--- a/mimetype.go
+++ b/mimetype.go
@@ -52,7 +52,7 @@ func DetectReader(r io.Reader) (*MIME, error) {
 			return errMIME, err
 		}
 	} else {
-		n := 0
+		var n int
 		in = make([]byte, l)
 		// io.UnexpectedEOF means len(r) < len(in). It is not an error in this case,
 		// it just means the input file is smaller than the allocated bytes slice.
diff --git a/tree.go b/tree.go
index 374728b..dfd3227 100644
--- a/tree.go
+++ b/tree.go
@@ -77,14 +77,14 @@ var (
 	oggAudio = newMIME("audio/ogg", ".oga", magic.OggAudio)
 	oggVideo = newMIME("video/ogg", ".ogv", magic.OggVideo)
 	text     = newMIME("text/plain", ".txt", magic.Text, html, svg, xml, php, js, lua, perl, python, json, ndJSON, rtf, tcl, csv, tsv, vCard, iCalendar, warc)
-	xml      = newMIME("text/xml", ".xml", magic.Xml, rss, atom, x3d, kml, xliff, collada, gml, gpx, tcx, amf, threemf, xfdf, owl2)
+	xml      = newMIME("text/xml", ".xml", magic.XML, rss, atom, x3d, kml, xliff, collada, gml, gpx, tcx, amf, threemf, xfdf, owl2)
 	json     = newMIME("application/json", ".json", magic.JSON, geoJSON, har)
 	har      = newMIME("application/json", ".har", magic.HAR)
 	csv      = newMIME("text/csv", ".csv", magic.Csv)
 	tsv      = newMIME("text/tab-separated-values", ".tsv", magic.Tsv)
 	geoJSON  = newMIME("application/geo+json", ".geojson", magic.GeoJSON)
 	ndJSON   = newMIME("application/x-ndjson", ".ndjson", magic.NdJSON)
-	html     = newMIME("text/html", ".html", magic.Html)
+	html     = newMIME("text/html", ".html", magic.HTML)
 	php      = newMIME("text/x-php", ".php", magic.Php)
 	rtf      = newMIME("text/rtf", ".rtf", magic.Rtf)
 	js       = newMIME("application/javascript", ".js", magic.Js).
@@ -147,7 +147,7 @@ var (
 	au   = newMIME("audio/basic", ".au", magic.Au)
 	amr  = newMIME("audio/amr", ".amr", magic.Amr).
 		alias("audio/amr-nb")
-	aac  = newMIME("audio/aac", ".aac", magic.Aac)
+	aac  = newMIME("audio/aac", ".aac", magic.AAC)
 	voc  = newMIME("audio/x-unknown", ".voc", magic.Voc)
 	aMp4 = newMIME("audio/mp4", ".mp4", magic.AMp4).
 		alias("audio/x-m4a", "audio/x-mp4a")
@@ -173,8 +173,8 @@ var (
 		alias("video/asf", "video/x-ms-wmv")
 	rmvb  = newMIME("application/vnd.rn-realmedia-vbr", ".rmvb", magic.Rmvb)
 	class = newMIME("application/x-java-applet", ".class", magic.Class)
-	swf   = newMIME("application/x-shockwave-flash", ".swf", magic.Swf)
-	crx   = newMIME("application/x-chrome-extension", ".crx", magic.Crx)
+	swf   = newMIME("application/x-shockwave-flash", ".swf", magic.SWF)
+	crx   = newMIME("application/x-chrome-extension", ".crx", magic.CRX)
 	ttf   = newMIME("font/ttf", ".ttf", magic.Ttf).
 		alias("font/sfnt", "application/x-font-ttf", "application/font-sfnt")
 	woff    = newMIME("font/woff", ".woff", magic.Woff)
@@ -194,7 +194,7 @@ var (
 	ar      = newMIME("application/x-archive", ".a", magic.Ar, deb).
 		alias("application/x-unix-archive")
 	deb = newMIME("application/vnd.debian.binary-package", ".deb", magic.Deb)
-	rpm = newMIME("application/x-rpm", ".rpm", magic.Rpm)
+	rpm = newMIME("application/x-rpm", ".rpm", magic.RPM)
 	dcm = newMIME("application/dicom", ".dcm", magic.Dcm)
 	odt = newMIME("application/vnd.oasis.opendocument.text", ".odt", magic.Odt, ott).
 		alias("application/x-vnd.oasis.opendocument.text")
@@ -217,7 +217,7 @@ var (
 	odc = newMIME("application/vnd.oasis.opendocument.chart", ".odc", magic.Odc).
 		alias("application/x-vnd.oasis.opendocument.chart")
 	sxc = newMIME("application/vnd.sun.xml.calc", ".sxc", magic.Sxc)
-	rar = newMIME("application/x-rar-compressed", ".rar", magic.Rar).
+	rar = newMIME("application/x-rar-compressed", ".rar", magic.RAR).
 		alias("application/x-rar")
 	djvu    = newMIME("image/vnd.djvu", ".djvu", magic.DjVu)
 	mobi    = newMIME("application/x-mobipocket-ebook", ".mobi", magic.Mobi)