gocloud.dev: gocloud.dev/blob/fileblob Index | Examples | Files

package fileblob

import "gocloud.dev/blob/fileblob"

Package fileblob provides a blob implementation that uses the filesystem. Use OpenBucket to construct a *blob.Bucket.


For blob.OpenBucket, fileblob registers for the scheme "file". To customize the URL opener, or for more details on the URL format, see URLOpener. See https://gocloud.dev/concepts/urls/ for background information.


Go CDK supports all UTF-8 strings; to make this work with providers lacking full UTF-8 support, strings must be escaped (during writes) and unescaped (during reads). The following escapes are performed for fileblob:

- Blob keys: ASCII characters 0-31 are escaped to "__0x<hex>__".
  If os.PathSeparator != "/", it is also escaped.
  Additionally, the "/" in "../", the trailing "/" in "//", and a trailing
  "/" is key names are escaped in the same way.
  On Windows, the characters "<>:"|?*" are also escaped.


fileblob exposes the following types for As:

- Error: *os.PathError


// Create a temporary directory.
dir, err := ioutil.TempDir("", "go-cloud-fileblob-example")
if err != nil {
defer os.RemoveAll(dir)

// On Unix, append the dir to "file://".
// On Windows, convert "\" to "/" and add a leading "/":
dirpath := filepath.ToSlash(dir)
if os.PathSeparator != '/' && !strings.HasPrefix(dirpath, "/") {
    dirpath = "/" + dirpath

// blob.OpenBucket creates a *blob.Bucket from a URL.
ctx := context.Background()
b, err := blob.OpenBucket(ctx, "file://"+dirpath)
if err != nil {
defer b.Close()

// Now we can use b to read or write files to the container.
err = b.WriteAll(ctx, "my-key", []byte("hello world"), nil)
if err != nil {
data, err := b.ReadAll(ctx, "my-key")
if err != nil {


hello world



Package Files

attrs.go fileblob.go


const Scheme = "file"

Scheme is the URL scheme fileblob registers its URLOpener under on blob.DefaultMux.

func OpenBucket Uses

func OpenBucket(dir string, opts *Options) (*blob.Bucket, error)

OpenBucket creates a *blob.Bucket backed by the filesystem and rooted at dir, which must exist. See the package documentation for an example.


// This example is used in https://gocloud.dev/howto/blob/open-bucket/#local-ctor

// The directory you pass to fileblob.OpenBucket must exist first.
const myDir = "path/to/local/directory"
if err := os.MkdirAll(myDir, 0777); err != nil {

// Create a file-based bucket.
bucket, err := fileblob.OpenBucket(myDir, nil)
if err != nil {
defer bucket.Close()

type Options Uses

type Options struct {
    // URLSigner implements signing URLs (to allow access to a resource without
    // further authorization) and verifying that a given URL is unexpired and
    // contains a signature produced by the URLSigner.
    // URLSigner is only required for utilizing the SignedURL API.
    URLSigner URLSigner

Options sets options for constructing a *blob.Bucket backed by fileblob.

type URLOpener Uses

type URLOpener struct{}

URLOpener opens file bucket URLs like "file:///foo/bar/baz".

The URL's host is ignored.

If os.PathSeparator != "/", any leading "/" from the path is dropped and remaining '/' characters are converted to os.PathSeparator.

No query options are supported. Examples:

- file:///a/directory
  -> Passes "/a/directory" to OpenBucket.
- file://localhost/a/directory
  -> Also passes "/a/directory".
- file:///c:/foo/bar on Windows.
  -> Passes "c:\foo\bar".
- file://localhost/c:/foo/bar on Windows.
  -> Also passes "c:\foo\bar".

func (*URLOpener) OpenBucketURL Uses

func (*URLOpener) OpenBucketURL(ctx context.Context, u *url.URL) (*blob.Bucket, error)

OpenBucketURL opens a blob.Bucket based on u.

type URLSigner Uses

type URLSigner interface {
    // URLFromKey defines how the bucket's object key will be turned
    // into a signed URL. URLFromKey must be safe to call from multiple goroutines.
    URLFromKey(ctx context.Context, key string, opts *driver.SignedURLOptions) (*url.URL, error)

    // KeyFromURL must be able to validate a URL returned from URLFromKey.
    // KeyFromURL must only return the object if if the URL is
    // both unexpired and authentic. KeyFromURL must be safe to call from
    // multiple goroutines. Implementations of KeyFromURL should not modify
    // the URL argument.
    KeyFromURL(ctx context.Context, surl *url.URL) (string, error)

URLSigner defines an interface for creating and verifying a signed URL for objects in a fileblob bucket. Signed URLs are typically used for granting access to an otherwise-protected resource without requiring further authentication, and callers should take care to restrict the creation of signed URLs as is appropriate for their application.

type URLSignerHMAC Uses

type URLSignerHMAC struct {
    // contains filtered or unexported fields

URLSignerHMAC signs URLs by adding the object key, expiration time, and a hash-based message authentication code (HMAC) into the query parameters. Values of URLSignerHMAC with the same secret key will accept URLs produced by others as valid.

func NewURLSignerHMAC Uses

func NewURLSignerHMAC(baseURL *url.URL, secretKey []byte) *URLSignerHMAC

NewURLSignerHMAC creates a URLSignerHMAC. If the secret key is empty, then NewURLSignerHMAC panics.

func (*URLSignerHMAC) KeyFromURL Uses

func (h *URLSignerHMAC) KeyFromURL(ctx context.Context, sURL *url.URL) (string, error)

KeyFromURL checks expiry and signature, and returns the object key only if the signed URL is both authentic and unexpired.

func (*URLSignerHMAC) URLFromKey Uses

func (h *URLSignerHMAC) URLFromKey(ctx context.Context, key string, opts *driver.SignedURLOptions) (*url.URL, error)

URLFromKey creates a signed URL by copying the baseURL and appending the object key, expiry, and signature as a query params.

Package fileblob imports 21 packages (graph) and is imported by 10 packages. Updated 2019-05-16. Refresh now. Tools for package owners.