dotcloud/docker

package system // import "github.com/docker/docker/pkg/system"

import (
    "golang.org/x/sys/unix"
)

// Lgetxattr retrieves the value of the extended attribute identified by attr
// and associated with the given path in the file system.
// It will returns a nil slice and nil error if the xattr is not set.
func Lgetxattr(path string, attr string) ([]byte, error) {
    sysErr := func(err error) ([]byte, error) {
        return nil, &XattrError{Op: "lgetxattr", Attr: attr, Path: path, Err: err}
    }

    // Start with a 128 length byte array
    dest := make([]byte, 128)
    sz, errno := unix.Lgetxattr(path, attr, dest)

    for errno == unix.ERANGE {
        // Buffer too small, use zero-sized buffer to get the actual size
        sz, errno = unix.Lgetxattr(path, attr, []byte{})
        if errno != nil {
            return sysErr(errno)
        }
        dest = make([]byte, sz)
        sz, errno = unix.Lgetxattr(path, attr, dest)
    }

    switch {
    case errno == unix.ENODATA:
        return nil, nil
    case errno != nil:
        return sysErr(errno)
    }

    return dest[:sz], nil
}

// Lsetxattr sets the value of the extended attribute identified by attr
// and associated with the given path in the file system.
func Lsetxattr(path string, attr string, data []byte, flags int) error {
    err := unix.Lsetxattr(path, attr, data, flags)
    if err != nil {
        return &XattrError{Op: "lsetxattr", Attr: attr, Path: path, Err: err}
    }
    return nil
}