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package jsonutil
import (
"encoding/json"
"errors"
"fmt"
"io"
"os"
"github.com/ethereum-optimism/optimism/op-service/ioutil"
)
func LoadJSON[X any](inputPath string) (*X, error) {
if inputPath == "" {
return nil, errors.New("no path specified")
}
var f io.ReadCloser
f, err := ioutil.OpenDecompressed(inputPath)
if err != nil {
return nil, fmt.Errorf("failed to open file %q: %w", inputPath, err)
}
defer f.Close()
var state X
decoder := json.NewDecoder(f)
if err := decoder.Decode(&state); err != nil {
return nil, fmt.Errorf("failed to decode file %q: %w", inputPath, err)
}
// We are only expecting 1 JSON object - confirm there is no trailing data
if _, err := decoder.Token(); err != io.EOF {
return nil, fmt.Errorf("unexpected trailing data in file %q", inputPath)
}
return &state, nil
}
func WriteJSON[X any](outputPath string, value X, perm os.FileMode) error {
if outputPath == "" {
return nil
}
var out io.Writer
finish := func() error { return nil }
if outputPath != "-" {
f, err := ioutil.NewAtomicWriterCompressed(outputPath, perm)
if err != nil {
return fmt.Errorf("failed to open output file: %w", err)
}
// Ensure we close the stream without renaming even if failures occur.
defer func() {
_ = f.Abort()
}()
out = f
// Closing the file causes it to be renamed to the final destination
// so make sure we handle any errors it returns
finish = f.Close
} else {
out = os.Stdout
}
enc := json.NewEncoder(out)
enc.SetIndent("", " ")
if err := enc.Encode(value); err != nil {
return fmt.Errorf("failed to encode to JSON: %w", err)
}
_, err := out.Write([]byte{'\n'})
if err != nil {
return fmt.Errorf("failed to append new-line: %w", err)
}
if err := finish(); err != nil {
return fmt.Errorf("failed to finish write: %w", err)
}
return nil
}