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132 lines
3.5 KiB
Go
132 lines
3.5 KiB
Go
package transformers
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import (
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"fmt"
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"os"
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"strings"
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"github.com/johnkerl/miller/v6/pkg/cli"
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"github.com/johnkerl/miller/v6/pkg/mlrval"
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"github.com/johnkerl/miller/v6/pkg/types"
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)
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// ----------------------------------------------------------------
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const verbNameRemoveEmptyColumns = "remove-empty-columns"
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var RemoveEmptyColumnsSetup = TransformerSetup{
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Verb: verbNameRemoveEmptyColumns,
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UsageFunc: transformerRemoveEmptyColumnsUsage,
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ParseCLIFunc: transformerRemoveEmptyColumnsParseCLI,
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IgnoresInput: false,
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}
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func transformerRemoveEmptyColumnsUsage(
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o *os.File,
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) {
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fmt.Fprintf(o, "Usage: %s %s [options]\n", "mlr", verbNameRemoveEmptyColumns)
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fmt.Fprintf(o, "Omits fields which are empty on every input row. Non-streaming.\n")
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fmt.Fprintf(o, "Options:\n")
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fmt.Fprintf(o, "-h|--help Show this message.\n")
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}
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func transformerRemoveEmptyColumnsParseCLI(
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pargi *int,
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argc int,
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args []string,
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_ *cli.TOptions,
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doConstruct bool, // false for first pass of CLI-parse, true for second pass
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) IRecordTransformer {
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// Skip the verb name from the current spot in the mlr command line
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argi := *pargi
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argi++
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for argi < argc /* variable increment: 1 or 2 depending on flag */ {
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opt := args[argi]
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if !strings.HasPrefix(opt, "-") {
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break // No more flag options to process
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}
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if args[argi] == "--" {
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break // All transformers must do this so main-flags can follow verb-flags
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}
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argi++
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if opt == "-h" || opt == "--help" {
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transformerRemoveEmptyColumnsUsage(os.Stdout)
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os.Exit(0)
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} else {
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transformerRemoveEmptyColumnsUsage(os.Stderr)
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os.Exit(1)
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}
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}
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*pargi = argi
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if !doConstruct { // All transformers must do this for main command-line parsing
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return nil
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}
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transformer, err := NewTransformerRemoveEmptyColumns()
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if err != nil {
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fmt.Fprintln(os.Stderr, err)
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os.Exit(1)
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}
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return transformer
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}
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// ----------------------------------------------------------------
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type TransformerRemoveEmptyColumns struct {
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recordsAndContexts *list.List
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namesWithNonEmptyValues map[string]bool
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}
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func NewTransformerRemoveEmptyColumns() (*TransformerRemoveEmptyColumns, error) {
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tr := &TransformerRemoveEmptyColumns{
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recordsAndContexts: list.New(),
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namesWithNonEmptyValues: make(map[string]bool),
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}
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return tr, nil
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}
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// ---------------------------------------------------------------
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func (tr *TransformerRemoveEmptyColumns) Transform(
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inrecAndContext *types.RecordAndContext,
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outputRecordsAndContexts *types.List[*types.RecordAndContext],
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inputDownstreamDoneChannel <-chan bool,
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outputDownstreamDoneChannel chan<- bool,
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) {
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HandleDefaultDownstreamDone(inputDownstreamDoneChannel, outputDownstreamDoneChannel)
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if !inrecAndContext.EndOfStream {
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inrec := inrecAndContext.Record
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tr.recordsAndContexts.PushBack(inrecAndContext)
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for pe := inrec.Head; pe != nil; pe = pe.Next {
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if !pe.Value.IsVoid() {
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tr.namesWithNonEmptyValues[pe.Key] = true
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}
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}
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} else { // end of record stream
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for e := tr.recordsAndContexts.Front(); e != nil; e = e.Next() {
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outrecAndContext := e.Value.(*types.RecordAndContext)
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outrec := outrecAndContext.Record
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newrec := mlrval.NewMlrmapAsRecord()
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for pe := outrec.Head; pe != nil; pe = pe.Next {
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_, ok := tr.namesWithNonEmptyValues[pe.Key]
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if ok {
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// Transferring ownership from old record to new record; no copy needed
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newrec.PutReference(pe.Key, pe.Value)
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}
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}
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outputRecordsAndContexts.PushBack(types.NewRecordAndContext(newrec, &outrecAndContext.Context))
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}
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outputRecordsAndContexts.PushBack(inrecAndContext) // Emit the stream-terminating null record
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}
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}
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