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package file
import (
"crypto/sha256"
"log"
"os"
)
func getChecksum(path string) [32]byte {
var checksum [32]byte
data, err := os.ReadFile(path)
if err != nil {
log.Printf("reading %s: %v (file does not exist or cannot be read)", path, err)
return checksum
}
checksum = sha256.Sum256(data)
log.Printf("computed checksum for %s: %x", path, checksum)
return checksum
}
func (f *File) ensureFile(path string, content []byte) error {
existingChecksum := getChecksum(path)
newChecksum := sha256.Sum256(content)
log.Printf("computed checksum for new content: %x", newChecksum)
tmpPath := path + ".tmp"
if err := writeTmpFile(tmpPath, content, f.mode); err != nil {
return err
}
if err := updateFromTmp(tmpPath, path, existingChecksum != newChecksum); err != nil {
return err
}
return f.applyAttributesTo(path)
}
func writeTmpFile(tmpPath string, content []byte, mode os.FileMode) error {
log.Printf("writing %d bytes to temporary file %s with mode %v", len(content), tmpPath, mode)
if err := os.WriteFile(tmpPath, content, mode); err != nil {
log.Printf("failed to write temporary file %s: %v", tmpPath, err)
return err
}
log.Printf("successfully wrote temporary file %s", tmpPath)
return nil
}
func updateFromTmp(tmpPath, path string, checksumChanged bool) error {
if !checksumChanged {
log.Printf("checksums match, removing temporary file %s", tmpPath)
if err := os.Remove(tmpPath); err != nil {
log.Printf("failed to remove temporary file %s: %v", tmpPath, err)
return err
}
log.Printf("no changes needed for %s", path)
return nil
}
log.Printf("checksums differ, renaming %s to %s", tmpPath, path)
if err := os.Rename(tmpPath, path); err != nil {
log.Printf("failed to rename %s to %s: %v", tmpPath, path, err)
os.Remove(tmpPath)
return err
}
log.Printf("successfully updated %s", path)
return nil
}
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