fs: make an in memory object for short transfers

fs/object.go

@@ -1,6 +1,12 @@
 package fs
 
-import "time"
+import (
+	"bytes"
+	"errors"
+	"io"
+	"io/ioutil"
+	"time"
+)
 
 // NewStaticObjectInfo returns a static ObjectInfo
 // If hashes is nil and fs is not nil, the hash map will be replaced with
@@ -48,3 +54,182 @@ func (i *staticObjectInfo) Hash(h HashType) (string, error) {
 	}
 	return "", ErrHashUnsupported
 }
+
+// MemoryFs is an in memory Fs, it only supports FsInfo and Put
+var MemoryFs memoryFs
+
+// memoryFs is an in memory fs
+type memoryFs struct{}
+
+// Name of the remote (as passed into NewFs)
+func (memoryFs) Name() string { return "memory" }
+
+// Root of the remote (as passed into NewFs)
+func (memoryFs) Root() string { return "" }
+
+// String returns a description of the FS
+func (memoryFs) String() string { return "memory" }
+
+// Precision of the ModTimes in this Fs
+func (memoryFs) Precision() time.Duration { return time.Nanosecond }
+
+// Returns the supported hash types of the filesystem
+func (memoryFs) Hashes() HashSet { return SupportedHashes }
+
+// Features returns the optional features of this Fs
+func (memoryFs) Features() *Features { return &Features{} }
+
+// List the objects and directories in dir into entries.  The
+// entries can be returned in any order but should be for a
+// complete directory.
+//
+// dir should be "" to list the root, and should not have
+// trailing slashes.
+//
+// This should return ErrDirNotFound if the directory isn't
+// found.
+func (memoryFs) List(dir string) (entries DirEntries, err error) {
+	return nil, nil
+}
+
+// NewObject finds the Object at remote.  If it can't be found
+// it returns the error ErrorObjectNotFound.
+func (memoryFs) NewObject(remote string) (Object, error) {
+	return nil, ErrorObjectNotFound
+}
+
+// Put in to the remote path with the modTime given of the given size
+//
+// May create the object even if it returns an error - if so
+// will return the object and the error, otherwise will return
+// nil and the error
+func (memoryFs) Put(in io.Reader, src ObjectInfo, options ...OpenOption) (Object, error) {
+	o := NewMemoryObject(src.Remote(), src.ModTime(), nil)
+	return o, o.Update(in, src, options...)
+}
+
+// Mkdir makes the directory (container, bucket)
+//
+// Shouldn't return an error if it already exists
+func (memoryFs) Mkdir(dir string) error {
+	return errors.New("memoryFs: can't make directory")
+}
+
+// Rmdir removes the directory (container, bucket) if empty
+//
+// Return an error if it doesn't exist or isn't empty
+func (memoryFs) Rmdir(dir string) error {
+	return ErrorDirNotFound
+}
+
+var _ Fs = MemoryFs
+
+// MemoryObject is an in memory object
+type MemoryObject struct {
+	remote  string
+	modTime time.Time
+	content []byte
+}
+
+// NewMemoryObject returns an in memory Object with the modTime and content passed in
+func NewMemoryObject(remote string, modTime time.Time, content []byte) *MemoryObject {
+	return &MemoryObject{
+		remote:  remote,
+		modTime: modTime,
+		content: content,
+	}
+}
+
+// Content returns the underlying buffer
+func (o *MemoryObject) Content() []byte {
+	return o.content
+}
+
+// Fs returns read only access to the Fs that this object is part of
+func (o *MemoryObject) Fs() Info {
+	return MemoryFs
+}
+
+// Remote returns the remote path
+func (o *MemoryObject) Remote() string {
+	return o.remote
+}
+
+// String returns a description of the Object
+func (o *MemoryObject) String() string {
+	return o.remote
+}
+
+// ModTime returns the modification date of the file
+func (o *MemoryObject) ModTime() time.Time {
+	return o.modTime
+}
+
+// Size returns the size of the file
+func (o *MemoryObject) Size() int64 {
+	return int64(len(o.content))
+}
+
+// Storable says whether this object can be stored
+func (o *MemoryObject) Storable() bool {
+	return true
+}
+
+// Hash returns the requested hash of the contents
+func (o *MemoryObject) Hash(h HashType) (string, error) {
+	hash, err := NewMultiHasherTypes(HashSet(h))
+	if err != nil {
+		return "", err
+	}
+	_, err = hash.Write(o.content)
+	if err != nil {
+		return "", err
+	}
+	return hash.Sums()[h], nil
+}
+
+// SetModTime sets the metadata on the object to set the modification date
+func (o *MemoryObject) SetModTime(modTime time.Time) error {
+	o.modTime = modTime
+	return nil
+}
+
+// Open opens the file for read.  Call Close() on the returned io.ReadCloser
+func (o *MemoryObject) Open(options ...OpenOption) (io.ReadCloser, error) {
+	content := o.content
+	for _, option := range options {
+		switch x := option.(type) {
+		case *RangeOption:
+			content = o.content[x.Start:x.End]
+		case *SeekOption:
+			content = o.content[x.Offset:]
+		default:
+			if option.Mandatory() {
+				Logf(o, "Unsupported mandatory option: %v", option)
+			}
+		}
+	}
+	return ioutil.NopCloser(bytes.NewBuffer(content)), nil
+}
+
+// Update in to the object with the modTime given of the given size
+//
+// This re-uses the internal buffer if at all possible.
+func (o *MemoryObject) Update(in io.Reader, src ObjectInfo, options ...OpenOption) (err error) {
+	size := src.Size()
+	if size == 0 {
+		o.content = nil
+	} else if size < 0 || int64(cap(o.content)) < size {
+		o.content, err = ioutil.ReadAll(in)
+	} else {
+		o.content = o.content[:size]
+		_, err = io.ReadFull(in, o.content)
+	}
+	o.modTime = src.ModTime()
+	return err
+}
+
+// Remove this object
+func (o *MemoryObject) Remove() error {
+	return errors.New("memoryObject.Remove not supported")
+}