update vendor

vendor/github.com/qiniu/x/bytes.v7/replace.go

@@ -0,0 +1,54 @@
+package bytes
+
+import (
+	"bytes"
+)
+
+// ---------------------------------------------------
+
+func ReplaceAt(b []byte, off, nsrc int, dest []byte) []byte {
+
+	ndelta := len(dest) - nsrc
+	if ndelta < 0 {
+		left := b[off+nsrc:]
+		off += copy(b[off:], dest)
+		off += copy(b[off:], left)
+		return b[:off]
+	}
+
+	if ndelta > 0 {
+		b = append(b, dest[:ndelta]...)
+		copy(b[off+len(dest):], b[off+nsrc:])
+		copy(b[off:], dest)
+	} else {
+		copy(b[off:], dest)
+	}
+	return b
+}
+
+func ReplaceOne(b []byte, from int, src, dest []byte) ([]byte, int) {
+
+	pos := bytes.Index(b[from:], src)
+	if pos < 0 {
+		return b, -1
+	}
+
+	from += pos
+	return ReplaceAt(b, from, len(src), dest), from + len(dest)
+}
+
+func Replace(b []byte, src, dest []byte, n int) []byte {
+
+	from := 0
+	for n != 0 {
+		b, from = ReplaceOne(b, from, src, dest)
+		if from < 0 {
+			break
+		}
+		n--
+	}
+	return b
+}
+
+// ---------------------------------------------------
+