subtree merge: cyphar/govis

govis is a reimplementation of vis(3) and unvis(3) specifically made to
be unicode aware. It was specifically rewritten to replace cvis and the
other go vis reimplementation we have in go-mtree.

Signed-off-by: Aleksa Sarai <asarai@suse.de>

pkg/govis/govis.go

@@ -0,0 +1,38 @@
+/*
+ * govis: unicode aware vis(3) encoding implementation
+ * Copyright (C) 2017 SUSE LLC.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package govis
+
+type VisFlag uint
+
+// vis() has a variety of flags when deciding what encodings to use. While
+// mtree only uses one set of flags, implementing them all is necessary in
+// order to have compatibility with BSD's vis() and unvis() commands.
+const (
+	VisOctal     VisFlag = (1 << iota)     // VIS_OCTAL: Use octal \ddd format.
+	VisCStyle                              // VIS_CSTYLE: Use \[nrft0..] where appropriate.
+	VisSpace                               // VIS_SP: Also encode space.
+	VisTab                                 // VIS_TAB: Also encode tab.
+	VisNewline                             // VIS_NL: Also encode newline.
+	VisSafe                                // VIS_SAFE: Encode unsafe characters.
+	VisNoSlash                             // VIS_NOSLASH: Inhibit printing '\'.
+	VisHTTPStyle                           // VIS_HTTPSTYLE: HTTP-style escape %xx.
+	VisGlob                                // VIS_GLOB: Encode glob(3) magics.
+	visMask      VisFlag = (1 << iota) - 1 // Mask of all flags.
+
+	VisWhite VisFlag = (VisSpace | VisTab | VisNewline)
+)