51 lines
968 B
Go
51 lines
968 B
Go
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// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
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// All rights reserved.
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// data-cursors.go
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package expr
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import (
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"io"
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)
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const (
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initName = "init"
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nextName = "next"
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currentName = "current"
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)
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type dataCursor struct {
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ds map[any]*term
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ctx ExprContext
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index int
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resource any
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nextFunc Functor
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currentFunc Functor
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}
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func (dc *dataCursor) String() string {
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return "$(...)"
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}
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func (dc *dataCursor) Current() (item any, err error) { // must return io.EOF at the last item
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if item, err = dc.currentFunc.Invoke(dc.ctx, currentName, []any{}); err == nil && item == nil {
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err = io.EOF
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}
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return
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}
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func (dc *dataCursor) Next() (item any, err error) { // must return io.EOF after the last item
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if item, err = dc.nextFunc.Invoke(dc.ctx, nextName, []any{}); err == nil {
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if item == nil {
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err = io.EOF
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} else {
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dc.index++
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}
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}
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return
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}
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func (dc *dataCursor) Index() int {
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return dc.index
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}
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