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// Package kstore provides durable, typed document files.
package kstore
import (
"fmt"
"os"
"path/filepath"
)
// Codec serializes and deserializes document values.
type Codec interface {
Marshal(value any) ([]byte, error)
Unmarshal(data []byte, value any) error
}
// Load reads and decodes a document from path.
func Load[T any](path string, codec Codec) (T, error) {
var value T
data, err := os.ReadFile(path) // #nosec G304 -- Callers explicitly provide the document path.
if err != nil {
return value, fmt.Errorf("read document %q: %w", path, err)
}
if err := codec.Unmarshal(data, &value); err != nil {
return value, fmt.Errorf("decode document %q: %w", path, err)
}
return value, nil
}
// Save encodes value and atomically replaces path with the requested mode.
func Save(path string, value any, codec Codec, mode os.FileMode) error {
data, err := codec.Marshal(value)
if err != nil {
return fmt.Errorf("encode document %q: %w", path, err)
}
directory := filepath.Dir(path)
temporary, err := os.CreateTemp(directory, "."+filepath.Base(path)+".tmp-*")
if err != nil {
return fmt.Errorf("create temporary document for %q: %w", path, err)
}
temporaryPath := temporary.Name()
defer os.Remove(temporaryPath) //nolint:errcheck // Best-effort cleanup after close or rename.
if err := temporary.Chmod(mode); err != nil {
_ = temporary.Close()
return fmt.Errorf("set permissions on temporary document for %q: %w", path, err)
}
if _, err := temporary.Write(data); err != nil {
_ = temporary.Close()
return fmt.Errorf("write temporary document for %q: %w", path, err)
}
if err := temporary.Close(); err != nil {
return fmt.Errorf("close temporary document for %q: %w", path, err)
}
if err := os.Rename(temporaryPath, path); err != nil {
return fmt.Errorf("replace document %q: %w", path, err)
}
return nil
}
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