1 package unstable

     2 

     3 // root contains a full AST.

     4 //

     5 // It is immutable once constructed with Builder.

     6 type root struct {

     7 	nodes []Node

     8 }

     9 

    10 // Iterator over the top level nodes.

    11 func (r *root) Iterator() Iterator {

    12 	it := Iterator{}

    13 	if len(r.nodes) > 0 {

    14 		it.node = &r.nodes[0]

    15 	}

    16 	return it

    17 }

    18 

    19 func (r *root) at(idx reference) *Node {

    20 	return &r.nodes[idx]

    21 }

    22 

    23 type reference int

    24 

    25 const invalidReference reference = -1

    26 

    27 func (r reference) Valid() bool {

    28 	return r != invalidReference

    29 }

    30 

    31 type builder struct {

    32 	tree    root

    33 	lastIdx int

    34 }

    35 

    36 func (b *builder) Tree() *root {

    37 	return &b.tree

    38 }

    39 

    40 func (b *builder) NodeAt(ref reference) *Node {

    41 	return b.tree.at(ref)

    42 }

    43 

    44 func (b *builder) Reset() {

    45 	b.tree.nodes = b.tree.nodes[:0]

    46 	b.lastIdx = 0

    47 }

    48 

    49 func (b *builder) Push(n Node) reference {

    50 	b.lastIdx = len(b.tree.nodes)

    51 	b.tree.nodes = append(b.tree.nodes, n)

    52 	return reference(b.lastIdx)

    53 }

    54 

    55 func (b *builder) PushAndChain(n Node) reference {

    56 	newIdx := len(b.tree.nodes)

    57 	b.tree.nodes = append(b.tree.nodes, n)

    58 	if b.lastIdx >= 0 {

    59 		b.tree.nodes[b.lastIdx].next = newIdx - b.lastIdx

    60 	}

    61 	b.lastIdx = newIdx

    62 	return reference(b.lastIdx)

    63 }

    64 

    65 func (b *builder) AttachChild(parent reference, child reference) {

    66 	b.tree.nodes[parent].child = int(child) - int(parent)

    67 }

    68 

    69 func (b *builder) Chain(from reference, to reference) {

    70 	b.tree.nodes[from].next = int(to) - int(from)

    71 }