In memory backend (#26)

## [5.2.0] - 2019-07-16
### Added
- In-Memory backend vfs implementation
- Included the in-memory backend to the list of registered backends used in backend_integration_test
- Checking for existence at the start of various File functions (size, seek, etc) and returning and error if the file does not exist on the OS backend
- Tests in  backend_integration_test that ensure that operations done on non-existent files throw an error
- mem.md in vfs/docs, updated link to it in the README.md
### Fixed
- Relative path validation in utils.go now disallows empty names
### Changed
- utils_test.go now expects an empty string NOT to validate
- updated README to include "Touch()" definition under the File interface rather than the Location interface
- updated README to exclude "in-memory-backend" from the list of ideas

CHANGELOG.md

@@ -5,6 +5,21 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+## [5.2.0] - 2019-07-16
+### Added
+- In-Memory backend vfs implementation
+- Included the in-memory backend to the list of registered backends used in backend_integration_test
+- Checking for existence at the start of various File functions (size, seek, etc) and returning and error if the file does not exist on the OS backend
+- Tests in  backend_integration_test that ensure that operations done on non-existent files throw an error
+- mem.md in vfs/docs, updated link to it in the README.md
+### Fixed
+- Relative path validation in utils.go now disallows empty names
+### Changed
+- utils_test.go now expects an empty string NOT to validate
+- updated README to include "Touch()" definition under the File interface rather than the Location interface
+- updated README to exclude "in-memory-backend" from the list of ideas
+
+
 ## [5.1.0] - 2019-07-08
 ### Added
 - Added Touch() method to File interface and implemented in each backend.

README.md

@@ -134,6 +134,7 @@ Feel free to send a pull request if you want to add your backend to the list.
   * [os backend](docs/os.md)
   * [gs backend](docs/gs.md)
   * [s3 backend](docs/s3.md)
+  * [in-memory backend](docs/mem.md)
 * [utils](docs/utils.md)
 
 ### Ideas
@@ -142,7 +143,6 @@ Things to add:
 
 * Add SFTP backend
 * Add Azure storage backend
-* Add in-memory backend
 * Provide better List() functionality with more abstracted filering and paging (iterator?) Retrun File structs vs URIs?
 * Add better/any context.Context() support
 
@@ -266,6 +266,10 @@ type File interface {
 	//
 	// For file:///some/path/to/file.txt, it would return file.txt
 	Name() string
+
+	// Touch creates a zero-length file on the vfs.File if no File exists.  Update File's last modified timestamp.
+    	// Returns error if unable to touch File.
+        Touch() error
 
 	// URI returns the fully qualified absolute URI for the File.  IE, s3://bucket/some/path/to/file.txt
 	URI() string
@@ -302,7 +306,7 @@ type FileSystem interface {
 	NewLocation(volume string, absLocPath string) (Location, error)
 
 	// Name returns the name of the FileSystem ie: Amazon S3, os, Google Cloud Storage, etc.
-	Name() string
+	Name() string	
 
 	// Scheme returns the uri scheme used by the FileSystem: s3, file, gs, etc.
 	Scheme() string
@@ -403,10 +407,6 @@ type Location interface {
 	// * Accepts relative file path.
 	DeleteFile(relFilePath string) error
 
-	// Touch creates a zero-length file on the vfs.File if no File exists.  Update File's last modified timestamp.
-	// Returns error if unable to touch File.
-	Touch() error
-
 	// URI returns the fully qualified absolute URI for the Location.  IE, s3://bucket/some/path/
 	//
 	// URI's for locations must always end with a slash.

backend/mem/doc.go

@@ -0,0 +1,20 @@
+/*
+Package mem built-in mem lib VFS implementation.
+Usage
+Rely on github.com/c2fo/vfs/backend
+  import(
+      "github.com/c2fo/vfs/backend"
+      "github.com/c2fo/vfs/backend/mem"
+  )
+  func UseFs() error {
+      fs, err := backend.Backend(mem.Scheme)
+      ...
+  }
+Or call directly:
+  import _mem "github.com/c2fo/vfs/backend/mem"
+  func DoSomething() {
+	fs := _mem.NewFileSystem()
+      ...
+  }
+*/
+package mem