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get_file_copy.go
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/
get_file_copy.go
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package getter
import (
"context"
"fmt"
"io"
"os"
)
// readerFunc is syntactic sugar for read interface.
type readerFunc func(p []byte) (n int, err error)
func (rf readerFunc) Read(p []byte) (n int, err error) { return rf(p) }
// Copy is a io.Copy cancellable by context
func Copy(ctx context.Context, dst io.Writer, src io.Reader) (int64, error) {
// Copy will call the Reader and Writer interface multiple time, in order
// to copy by chunk (avoiding loading the whole file in memory).
return io.Copy(dst, readerFunc(func(p []byte) (int, error) {
select {
case <-ctx.Done():
// context has been canceled
// stop process and propagate "context canceled" error
return 0, ctx.Err()
default:
// otherwise just run default io.Reader implementation
return src.Read(p)
}
}))
}
// copyReader copies from an io.Reader into a file, using umask to create the dst file
func copyReader(dst string, src io.Reader, fmode, umask os.FileMode) error {
dstF, err := os.OpenFile(dst, os.O_RDWR|os.O_CREATE|os.O_TRUNC, fmode)
if err != nil {
return err
}
defer dstF.Close()
_, err = io.Copy(dstF, src)
if err != nil {
return err
}
// Explicitly chmod; the process umask is unconditionally applied otherwise.
// We'll mask the mode with our own umask, but that may be different than
// the process umask
return os.Chmod(dst, mode(fmode, umask))
}
// copyFile copies a file in chunks from src path to dst path, using umask to create the dst file
func copyFile(ctx context.Context, dst, src string, disableSymlinks bool, fmode, umask os.FileMode) (int64, error) {
if disableSymlinks {
fileInfo, err := os.Lstat(src)
if err != nil {
return 0, fmt.Errorf("failed to check copy file source for symlinks: %w", err)
}
if fileInfo.Mode()&os.ModeSymlink == os.ModeSymlink {
return 0, ErrSymlinkCopy
}
}
srcF, err := os.Open(src)
if err != nil {
return 0, err
}
defer srcF.Close()
dstF, err := os.OpenFile(dst, os.O_RDWR|os.O_CREATE|os.O_TRUNC, fmode)
if err != nil {
return 0, err
}
defer dstF.Close()
count, err := Copy(ctx, dstF, srcF)
if err != nil {
return 0, err
}
// Explicitly chmod; the process umask is unconditionally applied otherwise.
// We'll mask the mode with our own umask, but that may be different than
// the process umask
err = os.Chmod(dst, mode(fmode, umask))
return count, err
}