add vendoring

vendor/github.com/ssor/bom/bom.go

@@ -0,0 +1,34 @@
+package bom
+
+import (
+	"bytes"
+	"io"
+	"io/ioutil"
+)
+
+const (
+	bom0 = 0xef
+	bom1 = 0xbb
+	bom2 = 0xbf
+)
+
+// CleanBom returns b with the 3 byte BOM stripped off the front if it is present.
+// If the BOM is not present, then b is returned.
+func CleanBom(b []byte) []byte {
+	if len(b) >= 3 &&
+		b[0] == bom0 &&
+		b[1] == bom1 &&
+		b[2] == bom2 {
+		return b[3:]
+	}
+	return b
+}
+
+// NewReaderWithoutBom returns an io.Reader that will skip over initial UTF-8 byte order marks.
+func NewReaderWithoutBom(r io.Reader) (io.Reader, error) {
+	bs, err := ioutil.ReadAll(r)
+	if err != nil {
+		return nil, err
+	}
+	return bytes.NewReader(CleanBom(bs)), nil
+}