13111: Add projects hierarchy under "home".

[arvados.git] / sdk / go / arvados / fs_deferred.go

diff --git a/sdk/go/arvados/fs_deferred.go b/sdk/go/arvados/fs_deferred.go
new file mode 100644 (file)
index 0000000..e638838
--- /dev/null
+++ b/sdk/go/arvados/fs_deferred.go
@@ -0,0 +1,103 @@
+// Copyright (C) The Arvados Authors. All rights reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package arvados
+
+import (
+       "log"
+       "os"
+       "sync"
+       "time"
+)
+
+func deferredCollectionFS(fs FileSystem, parent inode, coll Collection) inode {
+       var modTime time.Time
+       if coll.ModifiedAt != nil {
+               modTime = *coll.ModifiedAt
+       } else {
+               modTime = time.Now()
+       }
+       placeholder := &treenode{
+               fs:     fs,
+               parent: parent,
+               inodes: nil,
+               fileinfo: fileinfo{
+                       name:    coll.Name,
+                       modTime: modTime,
+                       mode:    0755 | os.ModeDir,
+               },
+       }
+       return &deferrednode{wrapped: placeholder, create: func() inode {
+               err := fs.RequestAndDecode(&coll, "GET", "arvados/v1/collections/"+coll.UUID, nil, nil)
+               if err != nil {
+                       log.Printf("BUG: unhandled error: %s", err)
+                       return placeholder
+               }
+               cfs, err := coll.FileSystem(fs, fs)
+               if err != nil {
+                       log.Printf("BUG: unhandled error: %s", err)
+                       return placeholder
+               }
+               root := cfs.rootnode()
+               root.SetParent(parent, coll.Name)
+               return root
+       }}
+}
+
+// A deferrednode wraps an inode that's expensive to build. Initially,
+// it responds to basic directory functions by proxying to the given
+// placeholder. If a caller uses a read/write/lock operation,
+// deferrednode calls the create() func to create the real inode, and
+// proxies to the real inode from then on.
+//
+// In practice, this means a deferrednode's parent's directory listing
+// can be generated using only the placeholder, instead of waiting for
+// create().
+type deferrednode struct {
+       wrapped inode
+       create  func() inode
+       mtx     sync.Mutex
+       created bool
+}
+
+func (dn *deferrednode) realinode() inode {
+       dn.mtx.Lock()
+       defer dn.mtx.Unlock()
+       if !dn.created {
+               dn.wrapped = dn.create()
+               dn.created = true
+       }
+       return dn.wrapped
+}
+
+func (dn *deferrednode) currentinode() inode {
+       dn.mtx.Lock()
+       defer dn.mtx.Unlock()
+       return dn.wrapped
+}
+
+func (dn *deferrednode) Read(p []byte, pos filenodePtr) (int, filenodePtr, error) {
+       return dn.realinode().Read(p, pos)
+}
+
+func (dn *deferrednode) Write(p []byte, pos filenodePtr) (int, filenodePtr, error) {
+       return dn.realinode().Write(p, pos)
+}
+
+func (dn *deferrednode) Child(name string, replace func(inode) inode) inode {
+       return dn.realinode().Child(name, replace)
+}
+
+func (dn *deferrednode) Truncate(size int64) error      { return dn.realinode().Truncate(size) }
+func (dn *deferrednode) SetParent(p inode, name string) { dn.realinode().SetParent(p, name) }
+func (dn *deferrednode) IsDir() bool                    { return dn.currentinode().IsDir() }
+func (dn *deferrednode) Readdir() []os.FileInfo         { return dn.realinode().Readdir() }
+func (dn *deferrednode) Size() int64                    { return dn.currentinode().Size() }
+func (dn *deferrednode) FileInfo() os.FileInfo          { return dn.currentinode().FileInfo() }
+func (dn *deferrednode) Lock()                          { dn.realinode().Lock() }
+func (dn *deferrednode) Unlock()                        { dn.realinode().Unlock() }
+func (dn *deferrednode) RLock()                         { dn.realinode().RLock() }
+func (dn *deferrednode) RUnlock()                       { dn.realinode().RUnlock() }
+func (dn *deferrednode) FS() FileSystem                 { return dn.currentinode().FS() }
+func (dn *deferrednode) Parent() inode                  { return dn.currentinode().Parent() }