yq/pkg/yqlib/stream_evaluator.go

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package yqlib
import (
"container/list"
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"errors"
"fmt"
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"io"
"os"
)
// A yaml expression evaluator that runs the expression multiple times for each given yaml document.
// Uses less memory than loading all documents and running the expression once, but this cannot process
// cross document expressions.
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type StreamEvaluator interface {
Evaluate(filename string, reader io.Reader, node *ExpressionNode, printer Printer, decoder Decoder) (uint, error)
EvaluateFiles(expression string, filenames []string, printer Printer, decoder Decoder) error
EvaluateNew(expression string, printer Printer) error
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}
type streamEvaluator struct {
treeNavigator DataTreeNavigator
fileIndex int
}
func NewStreamEvaluator() StreamEvaluator {
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return &streamEvaluator{treeNavigator: NewDataTreeNavigator()}
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}
func (s *streamEvaluator) EvaluateNew(expression string, printer Printer) error {
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node, err := ExpressionParser.ParseExpression(expression)
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if err != nil {
return err
}
candidateNode := createScalarNode(nil, "")
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inputList := list.New()
inputList.PushBack(candidateNode)
result, errorParsing := s.treeNavigator.GetMatchingNodes(Context{MatchingNodes: inputList}, node)
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if errorParsing != nil {
return errorParsing
}
return printer.PrintResults(result.MatchingNodes)
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}
func (s *streamEvaluator) EvaluateFiles(expression string, filenames []string, printer Printer, decoder Decoder) error {
var totalProcessDocs uint
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node, err := ExpressionParser.ParseExpression(expression)
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if err != nil {
return err
}
for _, filename := range filenames {
reader, err := readStream(filename)
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if err != nil {
return err
}
processedDocs, err := s.Evaluate(filename, reader, node, printer, decoder)
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if err != nil {
return err
}
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totalProcessDocs = totalProcessDocs + processedDocs
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switch reader := reader.(type) {
case *os.File:
safelyCloseFile(reader)
}
}
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if totalProcessDocs == 0 {
// problem is I've already slurped the leading content sadface
return s.EvaluateNew(expression, printer)
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}
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return nil
}
func (s *streamEvaluator) Evaluate(filename string, reader io.Reader, node *ExpressionNode, printer Printer, decoder Decoder) (uint, error) {
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var currentIndex uint
err := decoder.Init(reader)
if err != nil {
return 0, err
}
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for {
candidateNode, errorReading := decoder.Decode()
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if errors.Is(errorReading, io.EOF) {
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s.fileIndex = s.fileIndex + 1
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return currentIndex, nil
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} else if errorReading != nil {
return currentIndex, fmt.Errorf("bad file '%v': %w", filename, errorReading)
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}
candidateNode.document = currentIndex
candidateNode.filename = filename
candidateNode.fileIndex = s.fileIndex
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inputList := list.New()
inputList.PushBack(candidateNode)
result, errorParsing := s.treeNavigator.GetMatchingNodes(Context{MatchingNodes: inputList}, node)
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if errorParsing != nil {
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return currentIndex, errorParsing
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}
err := printer.PrintResults(result.MatchingNodes)
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if err != nil {
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return currentIndex, err
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}
currentIndex = currentIndex + 1
}
}