protocol/packp: sideband muxer and demuxer (#143)

* format/pakp: sideband demuxer

* format/pakp: sideband muxer

* format/pakp: sideband demuxer and muxer

* protocol/pakp: sideband demuxer and muxer

* documentation and improvements

* improvements

* handle scan errors properly

1 files changed, 33 insertions, 0 deletions

diff --git a/plumbing/protocol/packp/sideband/common.go b/plumbing/protocol/packp/sideband/common.go
new file mode 100644
index 0000000..de50012
--- /dev/null
+++ b/plumbing/protocol/packp/sideband/common.go
@@ -0,0 +1,33 @@
+package sideband
+
+// Type sideband type "side-band" or "side-band-64k"
+type Type int8
+
+const (
+	// Sideband legacy sideband type up to 1000-byte messages
+	Sideband Type = iota
+	// Sideband64k sideband type up to 65519-byte messages
+	Sideband64k Type = iota
+
+	// MaxPackedSize for Sideband type
+	MaxPackedSize = 1000
+	// MaxPackedSize64k for Sideband64k type
+	MaxPackedSize64k = 65520
+)
+
+// Channel sideband channel
+type Channel byte
+
+// WithPayload encode the payload as a message
+func (ch Channel) WithPayload(payload []byte) []byte {
+	return append([]byte{byte(ch)}, payload...)
+}
+
+const (
+	// PackData packfile content
+	PackData Channel = 1
+	// ProgressMessage progress messages
+	ProgressMessage Channel = 2
+	// ErrorMessage fatal error message just before stream aborts
+	ErrorMessage Channel = 3
+)