Big nasty commit to add code generation for encoding

tape/tag.go

@@ -0,0 +1,45 @@
+package tape
+
+import "git.tebibyte.media/sashakoshka/hopp/codec"
+
+type Tag byte; const (
+	SI      Tag = 0 << 5  // Small integer
+	LI      Tag = 1 << 5  // Large integer
+	FP      Tag = 2 << 5  // Floating point
+	SBA     Tag = 3 << 5  // Small byte array
+	LBA     Tag = 4 << 5  // Large byte array
+	OTA     Tag = 5 << 5  // One-tag array
+	KTV     Tag = 6 << 5  // Key-tag-value table
+	TNMask  Tag = 0xE0    // The entire TN bitfield
+	CNMask  Tag = 0x20    // The entire CN bitfield
+	CNLimit Tag = 32      // All valid CNs are < CNLimit
+)
+
+func (tag Tag) TN() int {
+	return int(tag >> 5)
+}
+
+func (tag Tag) CN() int {
+	return int(tag & CNMask)
+}
+
+func (tag Tag) WithCN(cn int) Tag {
+	return (tag & TNMask) | Tag(cn % 32)
+}
+
+func (tag Tag) Is(other Tag) bool {
+	return tag.TN() == other.TN()
+}
+
+// BufferTag returns the appropriate tag for a buffer.
+func BufferTag(value []byte) Tag {
+	return bufferLenTag(len(value))
+}
+
+func bufferLenTag(length int) Tag {
+	if length < int(CNLimit) {
+		return SBA.WithCN(length)
+	} else {
+		return LBA.WithCN(codec.IntBytes(uint64(length)))
+	}
+}