src/pkg/fs/utils.go

package fs

import (
	"fmt"
	"io"
	"io/fs"
	"os"
	"path"
)

// CopyFile copies a source file to a destination file.
func CopyFile(src string, dst string, mode fs.FileMode) error {
	srcFile, err := os.Open(src)
	if err != nil {
		return fmt.Errorf("could not open source file for copying: %v", err)
	}
	defer srcFile.Close()

	dstFile, err := os.OpenFile(dst, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, mode)
	if err != nil {
		return fmt.Errorf("could not open destination file for copying: %v", err)
	}
	defer dstFile.Close()

	_, err = io.Copy(dstFile, srcFile)
	if err != nil {
		return fmt.Errorf("error while copying file %s to %s: %v", src, dst, err)
	}

	return nil
}

// CopyDir copies a source directory to a target directory, preserving file
// permissions.
// This should be faster than calling `cp -r <src> <dst>` for small directories.
func CopyDir(src string, dst string, mode fs.FileMode) error {
	entries, err := os.ReadDir(src)
	if err != nil {
		return fmt.Errorf("failed to read directory for copying: %v", err)
	}

	err = os.MkdirAll(dst, mode)
	if err != nil {
		return err
	}

	for _, entry := range entries {
		entrySrc := path.Join(src, entry.Name())
		entryDst := path.Join(dst, entry.Name())
		entryInfo, err := entry.Info()
		if err != nil {
			return err
		}

		entryMode := entryInfo.Mode()
		if entryInfo.IsDir() {
			err = CopyDir(entrySrc, entryDst, entryMode)
		} else {
			err = CopyFile(entrySrc, entryDst, entryMode)
		}

		if err != nil {
			return err
		}
	}

	return nil
}

// IsDir returns whether or not a path exists and is a directory or is a
// symlink to a directory.
func IsDir(path string) bool {
	info, err := os.Stat(path)
	if err != nil {
		return false
	}

	return info.Mode().IsDir()
}

// IsFile returns whether or not a path exists and is a file or is a
// symlink to a file.
func IsFile(path string) bool {
	info, err := os.Stat(path)
	if err != nil {
		return false
	}

	return info.Mode().IsRegular()
}