copy.go

/*
The MIT License (MIT)

Copyright (c) 2018 otiai10

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/
package main

import (
	"io"
	"io/ioutil"
	"os"
	"path/filepath"
)

// Copy copies src to dest, doesn't matter if src is a directory or a file
func Copy(src, dest string) error {
	info, err := os.Lstat(src)
	if err != nil {
		return err
	}
	return copy(src, dest, info)
}

// copy dispatches copy-funcs according to the mode.
// Because this "copy" could be called recursively,
// "info" MUST be given here, NOT nil.
func copy(src, dest string, info os.FileInfo) error {
	if info.Mode()&os.ModeSymlink != 0 {
		return lcopy(src, dest, info)
	}
	if info.IsDir() {
		return dcopy(src, dest, info)
	}
	return fcopy(src, dest, info)
}

// fcopy is for just a file,
// with considering existence of parent directory
// and file permission.
func fcopy(src, dest string, info os.FileInfo) error {

	if err := os.MkdirAll(filepath.Dir(dest), os.ModePerm); err != nil {
		return err
	}

	f, err := os.Create(dest)
	if err != nil {
		return err
	}
	defer f.Close()

	if err = os.Chmod(f.Name(), info.Mode()); err != nil {
		return err
	}

	s, err := os.Open(src)
	if err != nil {
		return err
	}
	defer s.Close()

	_, err = io.Copy(f, s)
	return err
}

// dcopy is for a directory,
// with scanning contents inside the directory
// and pass everything to "copy" recursively.
func dcopy(srcdir, destdir string, info os.FileInfo) error {

	if err := os.MkdirAll(destdir, info.Mode()); err != nil {
		return err
	}

	contents, err := ioutil.ReadDir(srcdir)
	if err != nil {
		return err
	}

	for _, content := range contents {
		cs, cd := filepath.Join(srcdir, content.Name()), filepath.Join(destdir, content.Name())
		if err := copy(cs, cd, content); err != nil {
			// If any error, exit immediately
			return err
		}
	}
	return nil
}

// lcopy is for a symlink,
// with just creating a new symlink by replicating src symlink.
func lcopy(src, dest string, info os.FileInfo) error {
	src, err := os.Readlink(src)
	if err != nil {
		return err
	}
	return os.Symlink(src, dest)
}