ui: move ops reader to ui package

To prepare support for cached OpBlock to refer to other Ops lists.

The exposure of OpsReader is alleviated by the removal of the Refs
and Data accessors for Ops.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

ui/internal/ops/ops.go

@@ -1,23 +1,5 @@
 package ops
 
-import (
-	"encoding/binary"
-)
-
-type Reader struct {
-	pc    int
-	stack []block
-	Refs  []interface{}
-	data  []byte
-
-	pseudoOp [1]byte
-}
-
-type block struct {
-	retPC int
-	endPC int
-}
-
 type OpType byte
 
 const (
@@ -53,66 +35,3 @@ const (
 	TypePushLen           = 1
 	TypePopLen            = 1
 )
-
-var typeLengths = [...]int{
-	TypeBlockDefLen,
-	TypeBlockLen,
-	TypeTransformLen,
-	TypeLayerLen,
-	TypeRedrawLen,
-	TypeClipLen,
-	TypeImageLen,
-	TypeDrawLen,
-	TypeColorLen,
-	TypePointerHandlerLen,
-	TypeKeyHandlerLen,
-	TypeHideInputLen,
-	TypePushLen,
-	TypePopLen,
-}
-
-// Reset start reading from the op list.
-func (r *Reader) Reset(data []byte, refs []interface{}) {
-	r.Refs = refs
-	r.data = data
-	r.stack = r.stack[:0]
-	r.pc = 0
-}
-
-func (r *Reader) Decode() ([]byte, bool) {
-	bo := binary.LittleEndian
-	for {
-		if r.pc == len(r.data) {
-			return nil, false
-		}
-		if len(r.stack) > 0 {
-			b := r.stack[len(r.stack)-1]
-			if r.pc == b.endPC {
-				r.pc = b.retPC
-				r.stack = r.stack[:len(r.stack)-1]
-				r.pseudoOp[0] = byte(TypePop)
-				return r.pseudoOp[:], true
-			}
-		}
-		t := OpType(r.data[r.pc])
-		n := typeLengths[t]
-		data := r.data[r.pc : r.pc+n]
-		switch t {
-		case TypeBlock:
-			blockIdx := int(bo.Uint32(data[1:]))
-			if OpType(r.data[blockIdx]) != TypeBlockDef {
-				panic("invalid block reference")
-			}
-			blockLen := int(bo.Uint32(r.data[blockIdx+1:]))
-			r.stack = append(r.stack, block{r.pc + n, blockIdx + blockLen})
-			r.pc = blockIdx + TypeBlockDefLen
-			r.pseudoOp[0] = byte(TypePush)
-			return r.pseudoOp[:], true
-		case TypeBlockDef:
-			r.pc += int(bo.Uint32(data[1:]))
-			continue
-		}
-		r.pc += n
-		return data, true
-	}
-}