copyfile.go
b3f1c98f34aahotfix-v2.3

copyfile.go
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			package filetools

			// Taken from http://stackoverflow.com/a/21067803

			import (
			"fmt"
			"io"
			"os"
			)

			// CopyFile copies a file from src to dst. If src and dst files exist, and are
			// the same, then return success. Otherise, attempt to create a hard link
			// between the two files. If that fail, copy the file contents from src to dst.
			func CopyFile(src, dst string) (err error) {
			sfi, err := os.Stat(src)
			if err != nil {
			return
			}
			if !sfi.Mode().IsRegular() {
			// cannot copy non-regular files (e.g., directories,
			// symlinks, devices, etc.)
			return fmt.Errorf("CopyFile: non-regular source file %s (%q)", sfi.Name(), sfi.Mode().String())
			}
			dfi, err := os.Stat(dst)
			if err != nil {
			if !os.IsNotExist(err) {
			return
			}
			} else {
			if !(dfi.Mode().IsRegular()) {
			return fmt.Errorf("CopyFile: non-regular destination file %s (%q)", dfi.Name(), dfi.Mode().String())
			}
			if os.SameFile(sfi, dfi) {
			return
			}
			}
			if err = os.Link(src, dst); err == nil {
			return
			}
			err = copyFileContents(src, dst)
			return
			}

			// copyFileContents copies the contents of the file named src to the file named
			// by dst. The file will be created if it does not already exist. If the
			// destination file exists, all it's contents will be replaced by the contents
			// of the source file.
			func copyFileContents(src, dst string) (err error) {
			in, err := os.Open(src)
			if err != nil {
			return
			}
			defer in.Close()
			out, err := os.Create(dst)
			if err != nil {
			return
			}
			defer func() {
			cerr := out.Close()
			if err == nil {
			err = cerr
			}
			}()
			if _, err = io.Copy(out, in); err != nil {
			return
			}
			err = out.Sync()
			return
			}