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58 lines
2.1 KiB
Go
58 lines
2.1 KiB
Go
// Copyright 2016 Attic Labs, Inc. All rights reserved.
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// Licensed under the Apache License, version 2.0:
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// http://www.apache.org/licenses/LICENSE-2.0
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package csv
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import (
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"encoding/csv"
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"fmt"
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"io"
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"github.com/attic-labs/noms/go/d"
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"github.com/attic-labs/noms/go/types"
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)
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// ValueToListAndElemDesc ensures that v is a types.List of structs, pulls the types.StructDesc that describes the elements of v out of vr, and returns the List and related StructDesc.
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func ValueToListAndElemDesc(v types.Value, vr types.ValueReader) (types.List, types.StructDesc) {
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d.PanicIfTrue(types.ListKind != v.Type().Kind(), "Expected ListKind, found %s", types.KindToString[v.Type().Kind()])
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t := v.Type().Desc.(types.CompoundDesc).ElemTypes[0]
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d.PanicIfTrue(types.StructKind != t.Kind(), "Expected StructKind, found %s", types.KindToString[v.Type().Kind()])
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return v.(types.List), t.Desc.(types.StructDesc)
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}
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// Write takes a types.List l of structs (described by sd) and writes it to output as comma-delineated values.
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func Write(l types.List, sd types.StructDesc, comma rune, output io.Writer) {
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structChan := make(chan types.Struct, 1024)
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go func() {
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l.IterAll(func(v types.Value, index uint64) {
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structChan <- v.(types.Struct)
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})
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close(structChan)
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}()
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fieldNames := getFieldNamesFromStruct(sd)
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csvWriter := csv.NewWriter(output)
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csvWriter.Comma = comma
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d.PanicIfTrue(csvWriter.Write(fieldNames) != nil, "Failed to write header %v", fieldNames)
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record := make([]string, len(fieldNames))
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for s := range structChan {
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for i, f := range fieldNames {
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record[i] = fmt.Sprintf("%v", s.Get(f))
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}
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d.PanicIfTrue(csvWriter.Write(record) != nil, "Failed to write record %v", record)
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}
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csvWriter.Flush()
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d.PanicIfTrue(csvWriter.Error() != nil, "error flushing csv")
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}
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func getFieldNamesFromStruct(structDesc types.StructDesc) (fieldNames []string) {
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structDesc.IterFields(func(name string, t *types.Type) {
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d.PanicIfTrue(!types.IsPrimitiveKind(t.Kind()), "Expected primitive kind, found %s", types.KindToString[t.Kind()])
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fieldNames = append(fieldNames, name)
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})
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return
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}
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