52 lines
1020 B
Go
52 lines
1020 B
Go
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package ast
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type Reference int
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const InvalidReference Reference = -1
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func (r Reference) Valid() bool {
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return r != InvalidReference
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}
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type Builder struct {
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tree Root
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lastIdx int
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}
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func (b *Builder) Tree() *Root {
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return &b.tree
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}
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func (b *Builder) NodeAt(ref Reference) *Node {
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return b.tree.at(ref)
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}
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func (b *Builder) Reset() {
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b.tree.nodes = b.tree.nodes[:0]
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b.lastIdx = 0
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}
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func (b *Builder) Push(n Node) Reference {
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b.lastIdx = len(b.tree.nodes)
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b.tree.nodes = append(b.tree.nodes, n)
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return Reference(b.lastIdx)
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}
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func (b *Builder) PushAndChain(n Node) Reference {
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newIdx := len(b.tree.nodes)
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b.tree.nodes = append(b.tree.nodes, n)
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if b.lastIdx >= 0 {
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b.tree.nodes[b.lastIdx].next = newIdx - b.lastIdx
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}
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b.lastIdx = newIdx
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return Reference(b.lastIdx)
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}
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func (b *Builder) AttachChild(parent Reference, child Reference) {
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b.tree.nodes[parent].child = int(child) - int(parent)
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}
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func (b *Builder) Chain(from Reference, to Reference) {
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b.tree.nodes[from].next = int(to) - int(from)
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}
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