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82dfd418bb
The parallelism in csv.Write() seemed like overkill since we had to build the entire CSV in memory in order to take advantage of it. The code is simpler, now, and uses far less memory, though it is likely to be slower for large data.
60 lines
2.1 KiB
Go
60 lines
2.1 KiB
Go
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/chunks"
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"github.com/attic-labs/noms/d"
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"github.com/attic-labs/noms/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 cs, and returns the List and related StructDesc.
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func ValueToListAndElemDesc(v types.Value, cs chunks.ChunkSource) (types.List, types.StructDesc) {
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d.Exp.Equal(types.ListKind, v.Type().Desc.Kind(),
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"Dataset must be List<>, found: %s", v.Type().Desc.Describe())
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u := v.Type().Desc.(types.CompoundDesc).ElemTypes[0]
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d.Exp.Equal(types.UnresolvedKind, u.Desc.Kind(),
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"List<> must be UnresolvedKind, found: %s", u.Desc.Describe())
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pkg := types.ReadPackage(u.PackageRef(), cs)
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d.Exp.Equal(types.PackageKind, pkg.Type().Desc.Kind(),
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"Failed to read package: %s", pkg.Type().Desc.Describe())
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desc := pkg.Types()[u.Ordinal()].Desc
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d.Exp.Equal(types.StructKind, desc.Kind(), "Did not find Struct: %s", desc.Describe())
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return v.(types.List), 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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d.Exp.Equal(types.StructKind, sd.Kind(), "Did not find Struct: %s", sd.Describe())
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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.Exp.NoError(csvWriter.Write(fieldNames), "Failed to write header %v", fieldNames)
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record := make([]string, len(fieldNames))
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l.IterAll(func(v types.Value, index uint64) {
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for i, f := range fieldNames {
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record[i] = fmt.Sprintf("%s", v.(types.Struct).Get(f))
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}
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d.Exp.NoError(csvWriter.Write(record), "Failed to write record %v", record)
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})
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csvWriter.Flush()
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d.Exp.NoError(csvWriter.Error(), "error flushing csv")
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}
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func getFieldNamesFromStruct(structDesc types.StructDesc) (fieldNames []string) {
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for _, f := range structDesc.Fields {
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d.Exp.Equal(true, types.IsPrimitiveKind(f.T.Desc.Kind()),
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"Non-primitive CSV export not supported:", f.T.Desc.Describe())
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fieldNames = append(fieldNames, f.Name)
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}
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return
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}
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