dotcloud/docker

// Package longpath introduces some constants and helper functions for handling
// long paths in Windows.
//
// Long paths are expected to be prepended with "\\?\" and followed by either a
// drive letter, a UNC server\share, or a volume identifier.
package longpath // import "github.com/docker/docker/pkg/longpath"

import (
    "os"
    "runtime"
    "strings"
)

// Prefix is the longpath prefix for Windows file paths.
//
// Deprecated: this const is only used internally, and will be removed in the next release
const Prefix = longPathPrefix

// longPathPrefix is the longpath prefix for Windows file paths.
const longPathPrefix = `\\?\`

// AddPrefix adds the Windows long path prefix to the path provided if
// it does not already have it.
func AddPrefix(path string) string {
    if strings.HasPrefix(path, longPathPrefix) {
        return path
    }
    if strings.HasPrefix(path, `\\`) {
        // This is a UNC path, so we need to add 'UNC' to the path as well.
        return longPathPrefix + `UNC` + path[1:]
    }
    return longPathPrefix + path
}

// MkdirTemp is the equivalent of [os.MkdirTemp], except that on Windows
// the result is in Windows longpath format. On Unix systems it is
// equivalent to [os.MkdirTemp].
func MkdirTemp(dir, prefix string) (string, error) {
    tempDir, err := os.MkdirTemp(dir, prefix)
    if err != nil {
        return "", err
    }
    if runtime.GOOS != "windows" {
        return tempDir, nil
    }
    return AddPrefix(tempDir), nil
}