mirror of
https://blitiri.com.ar/repos/chasquid
synced 2025-12-17 14:37:02 +00:00
f3b01cb493
This patch adds a missing docstrings for exported identifiers, and adjust some of the existing ones to match the standard style. In some cases, the identifiers were un-exported after noticing they had no external users. Besides improving documentation, it also reduces the linter noise significantly.
84 lines
2.0 KiB
Go
84 lines
2.0 KiB
Go
// Package safeio implements convenient I/O routines that provide additional
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// levels of safety in the presence of unexpected failures.
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package safeio
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import (
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"io/ioutil"
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"os"
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"path"
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"syscall"
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)
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// FileOp represents an operation on a file (passed by its name).
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type FileOp func(fname string) error
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// WriteFile writes data to a file named by filename, atomically.
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//
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// It's a wrapper to ioutil.WriteFile, but provides atomicity (and increased
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// safety) by writing to a temporary file and renaming it at the end.
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//
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// Before the final rename, the given ops (if any) are called. They can be
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// used to manipulate the file before it is atomically renamed.
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// If any operation fails, the file is removed and the error is returned.
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//
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// Note this relies on same-directory Rename being atomic, which holds in most
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// reasonably modern filesystems.
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func WriteFile(filename string, data []byte, perm os.FileMode, ops ...FileOp) error {
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// Note we create the temporary file in the same directory, otherwise we
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// would have no expectation of Rename being atomic.
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// We make the file names start with "." so there's no confusion with the
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// originals.
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tmpf, err := ioutil.TempFile(path.Dir(filename), "."+path.Base(filename))
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if err != nil {
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return err
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}
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if err = tmpf.Chmod(perm); err != nil {
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tmpf.Close()
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os.Remove(tmpf.Name())
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return err
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}
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if uid, gid := getOwner(filename); uid >= 0 {
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if err = tmpf.Chown(uid, gid); err != nil {
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tmpf.Close()
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os.Remove(tmpf.Name())
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return err
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}
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}
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if _, err = tmpf.Write(data); err != nil {
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tmpf.Close()
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os.Remove(tmpf.Name())
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return err
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}
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if err = tmpf.Close(); err != nil {
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os.Remove(tmpf.Name())
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return err
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}
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for _, op := range ops {
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if err = op(tmpf.Name()); err != nil {
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os.Remove(tmpf.Name())
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return err
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}
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}
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return os.Rename(tmpf.Name(), filename)
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}
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func getOwner(fname string) (uid, gid int) {
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uid = -1
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gid = -1
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stat, err := os.Stat(fname)
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if err == nil {
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if sysstat, ok := stat.Sys().(*syscall.Stat_t); ok {
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uid = int(sysstat.Uid)
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gid = int(sysstat.Gid)
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}
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}
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return
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}
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