Add support for CBOR sequence file format

internal/magic/binary.go

@@ -142,3 +142,119 @@ func Marc(raw []byte, limit uint32) bool {
 	// Field terminator is present.
 	return bytes.Contains(raw, []byte{0x1E})
 }
+
+// Cbor matches CBOR sequence data
+func Cbor(raw []byte, limit uint32) bool {
+	if len(raw) == 0 {
+		return false
+	}
+	for ok := true; ok == true; {
+		ok = cborHelper(&raw)
+	}
+	if len(raw) == 0 {
+		return true
+	} else {
+		return false
+	}
+}
+
+// a helper function for Cbor 
+// inspired by https://www.rfc-editor.org/rfc/rfc8949.html#section-appendix.c
+func cborHelper(raw *[]byte) bool {
+	if len(*raw) == 0 {
+		return false
+	}
+	t := uint8((*raw)[0] & 0xe0)
+	ai := (*raw)[0] & 0x1f
+	uval := uint64(ai)
+	*raw = (*raw)[1:]
+	val, ok := cborHead(raw, t, ai, uval)
+	if ok == false {
+		return ok
+	}
+	switch t {
+	case 0x40, 0x60:
+		if val < 0 {
+			return false
+		}
+		if len(*raw) < val {
+			return false
+		}
+		*raw = (*raw)[val:]
+	case 0x80, 0xa0:
+		if val < 0 {
+			return false
+		}
+		count := 1
+		if t == 0xa0 {
+			count = 2
+		}
+		for i := 0; i < val*count; i++ {
+			if ok = cborHelper(raw); ok == false {
+				return ok
+			}
+		}
+	case 0xc0:
+		for {
+			if len(*raw) == 0 {
+				return false
+			}
+			if uint8((*raw)[0]&0xe0) != 0xc0 {
+				break
+			}
+		}
+		return cborHelper(raw)
+	default:
+		return false
+	}
+	return true
+}
+
+func cborHead(raw *[]byte, t uint8, ai byte, val uint64) (int, bool) {
+	raw_len := len(*raw)
+	if raw_len == 0 {
+		return 0, false
+	}
+	if ai < 24 {
+		return int(val), true
+	}
+	switch ai {
+	case 24:
+		if raw_len < 2 {
+			return 0, false
+		}
+		val = uint64((*raw)[0])
+		*raw = (*raw)[1:]
+		if t == 0xe0 && val < 32 {
+			return 0, false
+		}
+	case 25:
+		if raw_len < 3 {
+			return 0, false
+		}
+		val = uint64(binary.BigEndian.Uint16((*raw)[0:2]))
+		*raw = (*raw)[2:]
+	case 26:
+		if raw_len < 5 {
+			return 0, false
+		}
+		val = uint64(binary.BigEndian.Uint32((*raw)[0:4]))
+		*raw = (*raw)[4:]
+	case 27:
+		if raw_len < 9 {
+			return 0, false
+		}
+		val = binary.BigEndian.Uint64((*raw)[0:8])
+		*raw = (*raw)[8:]
+	case 31:
+		switch t {
+		case 0x00, 0x20, 0xc0:
+			return 0, false
+		case 0xe0:
+			return 0, false
+		}
+	default:
+		return 0, false
+	}
+	return int(val), true
+}

mimetype_test.go

@@ -38,6 +38,7 @@ var files = map[string]string{
 	"bpg.bpg":            "image/bpg",
 	"bz2.bz2":            "application/x-bzip2",
 	"cab.cab":            "application/vnd.ms-cab-compressed",
+	"cbor":               "application/cbor-seq",
 	"class.class":        "application/x-java-applet",
 	"crx.crx":            "application/x-chrome-extension",
 	"csv.csv":            "text/csv",

supported_mimes.md

@@ -1,4 +1,4 @@
-## 165 Supported MIME types
+## 166 Supported MIME types
 This file is automatically generated when running tests. Do not edit manually.
 
 Extension | MIME type | Aliases
@@ -135,6 +135,7 @@ Extension | MIME type | Aliases
 **.pat** | image/x-gimp-pat | -
 **.gbr** | image/x-gimp-gbr | -
 **.glb** | model/gltf-binary | -
+**n/a** | application/cbor-seq | -
 **.txt** | text/plain | -
 **.html** | text/html | -
 **.svg** | image/svg+xml | -

testdata/cbor

@@ -0,0 +1 @@
+�t2013-03-21T20:04:00Z�t2013-03-21T20:04:00Z

tree.go

@@ -24,7 +24,7 @@ var root = newMIME("application/octet-stream", "",
 	gzip, class, swf, crx, ttf, woff, woff2, otf, eot, wasm, shx, dbf, dcm, rar,
 	djvu, mobi, lit, bpg, sqlite3, dwg, nes, lnk, macho, qcp, icns, heic,
 	heicSeq, heif, heifSeq, hdr, mrc, mdb, accdb, zstd, cab, rpm, xz, lzip,
-	torrent, cpio, tzif, xcf, pat, gbr, glb,
+	torrent, cpio, tzif, xcf, pat, gbr, glb, cbor,
 	// Keep text last because it is the slowest check
 	text,
 )
@@ -247,4 +247,5 @@ var (
 	gbr     = newMIME("image/x-gimp-gbr", ".gbr", magic.Gbr)
 	xfdf    = newMIME("application/vnd.adobe.xfdf", ".xfdf", magic.Xfdf)
 	glb     = newMIME("model/gltf-binary", ".glb", magic.Glb)
+	cbor = newMIME("application/cbor-seq", "", magic.Cbor)
 )