detect wasm file type

match_test.go

@@ -47,6 +47,7 @@ func TestMatchFile(t *testing.T) {
 		{"pptx"},
 		{"xlsx"},
 		{"mov"},
+		{"wasm"},
 	}
 
 	for _, test := range cases {

matchers/application.go

@@ -0,0 +1,20 @@
+package matchers
+
+var (
+	TypeWasm = newType("wasm", "application/wasm")
+)
+
+var Application = Map{
+	TypeWasm: Wasm,
+}
+
+// Wasm detects a Web Assembly 1.0 filetype.
+func Wasm(buf []byte) bool {
+	// WASM has starts with `\0asm`, followed by the version.
+	// http://webassembly.github.io/spec/core/binary/modules.html#binary-magic
+	return len(buf) >= 8 &&
+		buf[0] == 0x00 && buf[1] == 0x61 &&
+		buf[2] == 0x73 && buf[3] == 0x6D &&
+		buf[4] == 0x01 && buf[5] == 0x00 &&
+		buf[6] == 0x00 && buf[7] == 0x00
+}

matchers/matchers.go

@@ -47,5 +47,5 @@ func register(matchers ...Map) {
 func init() {
 	// Arguments order is intentional
 	// Archive files will be checked last due to prepend above in func NewMatcher
-	register(Archive, Document, Font, Audio, Video, Image)
+	register(Archive, Document, Font, Audio, Video, Image, Application)
 }