81 lines
2.3 KiB
Go
81 lines
2.3 KiB
Go
package datapoint
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import (
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"archive/zip"
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"bytes"
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"encoding/json"
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"fmt"
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"io"
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)
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const (
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MaxBatchBytes = 4 << 20 // Maximum ZIP payload size on the wire.
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MaxBatchJSONBytes = 16 << 20 // Maximum expanded JSON size.
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)
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// ZipBatch packages GPS fixes into an in-memory ZIP containing points.json.
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func ZipBatch(points []DataPoint) ([]byte, error) {
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raw, err := json.Marshal(points)
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if err != nil {
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return nil, fmt.Errorf("encode points: %w", err)
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}
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if len(raw) > MaxBatchJSONBytes {
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return nil, fmt.Errorf("batch JSON exceeds %d bytes", MaxBatchJSONBytes)
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}
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var buf bytes.Buffer
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zw := zip.NewWriter(&buf)
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file, err := zw.Create("points.json")
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if err != nil {
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return nil, err
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}
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if _, err = file.Write(raw); err != nil {
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return nil, err
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}
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if err = zw.Close(); err != nil {
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return nil, err
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}
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if buf.Len() > MaxBatchBytes {
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return nil, fmt.Errorf("ZIP batch exceeds %d bytes", MaxBatchBytes)
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}
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return buf.Bytes(), nil
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}
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// UnzipBatch reads points in memory; archive entries are never written to disk.
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// Legacy JSON batches are accepted so the server can be upgraded first.
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func UnzipBatch(payload []byte) ([]DataPoint, error) {
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if len(payload) > MaxBatchBytes {
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return nil, fmt.Errorf("batch exceeds %d bytes", MaxBatchBytes)
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}
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raw := payload
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if !bytes.HasPrefix(bytes.TrimSpace(payload), []byte("[")) && !bytes.Equal(bytes.TrimSpace(payload), []byte("null")) {
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zr, err := zip.NewReader(bytes.NewReader(payload), int64(len(payload)))
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if err != nil {
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return nil, fmt.Errorf("open ZIP batch: %w", err)
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}
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if len(zr.File) != 1 || zr.File[0].Name != "points.json" {
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return nil, fmt.Errorf("ZIP batch must contain only points.json")
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}
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file := zr.File[0]
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if file.UncompressedSize64 > MaxBatchJSONBytes {
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return nil, fmt.Errorf("expanded batch exceeds %d bytes", MaxBatchJSONBytes)
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}
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r, err := file.Open()
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if err != nil {
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return nil, fmt.Errorf("open points.json: %w", err)
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}
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defer r.Close()
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raw, err = io.ReadAll(io.LimitReader(r, MaxBatchJSONBytes+1))
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if err != nil {
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return nil, fmt.Errorf("read points.json: %w", err)
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}
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if len(raw) > MaxBatchJSONBytes {
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return nil, fmt.Errorf("expanded batch exceeds %d bytes", MaxBatchJSONBytes)
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}
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}
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var points []DataPoint
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if err := json.Unmarshal(raw, &points); err != nil {
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return nil, fmt.Errorf("decode points: %w", err)
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}
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return points, nil
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}
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