74 lines
1.5 KiB
Go
74 lines
1.5 KiB
Go
// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
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// All rights reserved.
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// operator-digest.go
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package expr
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import (
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"fmt"
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"io"
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"git.portale-stac.it/go-pkg/expr/kern"
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"git.portale-stac.it/go-pkg/expr/scan"
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)
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//-------- digest term
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func newDigestTerm(tk *scan.Token) (inst *scan.Term) {
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return &scan.Term{
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Tk: *tk,
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Children: make([]*scan.Term, 0, 2),
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Position: scan.PosInfix,
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Priority: scan.PriIterOp,
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EvalFunc: evalDigest,
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}
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}
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func evalDigest(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
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var leftValue, rightValue any
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var it kern.Iterator
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var item, lastValue any
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if err = opTerm.CheckOperands(); err != nil {
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return
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}
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if leftValue, err = opTerm.Children[0].Compute(ctx); err != nil {
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return
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}
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if it, err = NewIterator(ctx, leftValue, nil); err != nil {
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return nil, fmt.Errorf("left operand of DIGEST must be an iterable data-source; got %s", kern.TypeName(leftValue))
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}
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lastValue = nil
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for item, err = it.Next(); err == nil; item, err = it.Next() {
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ctx.SetVar("_", item)
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ctx.SetVar("__", it.Index())
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ctx.SetVar("_#", it.Count())
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if rightValue, err = opTerm.Children[1].Compute(ctx); err == nil {
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if rightValue == nil {
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break
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} else {
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lastValue = rightValue
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}
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}
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ctx.DeleteVar("_#")
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ctx.DeleteVar("__")
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ctx.DeleteVar("_")
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if err != nil {
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break
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}
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}
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if err == io.EOF {
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err = nil
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}
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v = lastValue
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return
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}
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// init
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func init() {
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scan.RegisterTermConstructor(scan.SymKwDigest, newDigestTerm)
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}
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