Merge branch '19088-s3-properties-tags'

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

diff --git a/sdk/go/arvados/fs_base.go b/sdk/go/arvados/fs_base.go
index 5f2747ac9ada9225455331daee0f10640202907f..2ad4d1f859f1141035c04cb4180c5ef623d1fa04 100644 (file)
--- a/sdk/go/arvados/fs_base.go
+++ b/sdk/go/arvados/fs_base.go
@@ -8,6 +8,7 @@ import (
        "errors"
        "fmt"
        "io"
+       "io/fs"
        "log"
        "net/http"
        "os"
@@ -77,6 +78,24 @@ type File interface {
        Stat() (os.FileInfo, error)
        Truncate(int64) error
        Sync() error
+       // Create a snapshot of a file or directory tree, which can
+       // then be spliced onto a different path or a different
+       // collection.
+       Snapshot() (*Subtree, error)
+       // Replace this file or directory with the given snapshot.
+       // The target must be inside a collection: Splice returns an
+       // error if the File is a virtual file or directory like
+       // by_id, a project directory, .arvados#collection,
+       // etc. Splice can replace directories with regular files and
+       // vice versa, except it cannot replace the root directory of
+       // a collection with a regular file.
+       Splice(snapshot *Subtree) error
+}
+
+// A Subtree is a detached part of a filesystem tree that can be
+// spliced into a filesystem via (File)Splice().
+type Subtree struct {
+       inode inode
 }
 
 // A FileSystem is an http.Filesystem plus Stat() and support for
@@ -141,6 +160,18 @@ type FileSystem interface {
        MemorySize() int64
 }
 
+type fsFS struct {
+       FileSystem
+}
+
+// FS returns an fs.FS interface to the given FileSystem, to enable
+// the use of fs.WalkDir, etc.
+func FS(fs FileSystem) fs.FS { return fsFS{fs} }
+func (fs fsFS) Open(path string) (fs.File, error) {
+       f, err := fs.FileSystem.Open(path)
+       return f, err
+}
+
 type inode interface {
        SetParent(parent inode, name string)
        Parent() inode
@@ -152,6 +183,12 @@ type inode interface {
        Readdir() ([]os.FileInfo, error)
        Size() int64
        FileInfo() os.FileInfo
+       // Create a snapshot of this node and its descendants.
+       Snapshot() (inode, error)
+       // Replace this node with a copy of the provided snapshot.
+       // Caller may provide the same snapshot to multiple Splice
+       // calls, but must not modify the snapshot concurrently.
+       Splice(inode) error
 
        // Child() performs lookups and updates of named child nodes.
        //
@@ -197,6 +234,14 @@ type fileinfo struct {
        mode    os.FileMode
        size    int64
        modTime time.Time
+       // If not nil, sys() returns the source data structure, which
+       // can be a *Collection, *Group, or nil. Currently populated
+       // only for project dirs and top-level collection dirs. Does
+       // not stay up to date with upstream changes.
+       //
+       // Intended to support keep-web's properties-as-s3-metadata
+       // feature (https://dev.arvados.org/issues/19088).
+       sys func() interface{}
 }
 
 // Name implements os.FileInfo.
@@ -224,9 +269,12 @@ func (fi fileinfo) Size() int64 {
        return fi.size
 }
 
-// Sys implements os.FileInfo.
+// Sys implements os.FileInfo. See comment in fileinfo struct.
 func (fi fileinfo) Sys() interface{} {
-       return nil
+       if fi.sys == nil {
+               return nil
+       }
+       return fi.sys()
 }
 
 type nullnode struct{}
@@ -270,6 +318,14 @@ func (*nullnode) MemorySize() int64 {
        return 64
 }
 
+func (*nullnode) Snapshot() (inode, error) {
+       return nil, ErrInvalidOperation
+}
+
+func (*nullnode) Splice(inode) error {
+       return ErrInvalidOperation
+}
+
 type treenode struct {
        fs       FileSystem
        parent   inode
@@ -370,7 +426,7 @@ func (n *treenode) MemorySize() (size int64) {
        for _, inode := range n.inodes {
                size += inode.MemorySize()
        }
-       return
+       return 64 + size
 }
 
 type fileSystem struct {
@@ -418,14 +474,14 @@ func (fs *fileSystem) openFile(name string, flag int, perm os.FileMode) (*fileha
        default:
                return nil, fmt.Errorf("invalid flags 0x%x", flag)
        }
-       if !writable && parent.IsDir() {
+       if parent.IsDir() {
                // A directory can be opened via "foo/", "foo/.", or
                // "foo/..".
                switch name {
                case ".", "":
-                       return &filehandle{inode: parent}, nil
+                       return &filehandle{inode: parent, readable: readable, writable: writable}, nil
                case "..":
-                       return &filehandle{inode: parent.Parent()}, nil
+                       return &filehandle{inode: parent.Parent(), readable: readable, writable: writable}, nil
                }
        }
        createMode := flag&os.O_CREATE != 0
@@ -559,7 +615,7 @@ func (fs *fileSystem) Rename(oldname, newname string) error {
                // supported. Locking inodes from different
                // filesystems could deadlock, so we must error out
                // now.
-               return ErrInvalidArgument
+               return ErrInvalidOperation
        }
 
        // To ensure we can test reliably whether we're about to move
@@ -697,3 +753,32 @@ func rlookup(start inode, path string) (node inode, err error) {
 func permittedName(name string) bool {
        return name != "" && name != "." && name != ".." && !strings.Contains(name, "/")
 }
+
+// Snapshot returns a Subtree that's a copy of the given path. It
+// returns an error if the path is not inside a collection.
+func Snapshot(fs FileSystem, path string) (*Subtree, error) {
+       f, err := fs.OpenFile(path, os.O_RDONLY, 0)
+       if err != nil {
+               return nil, err
+       }
+       defer f.Close()
+       return f.Snapshot()
+}
+
+// Splice inserts newsubtree at the indicated target path.
+//
+// Splice returns an error if target is not inside a collection.
+//
+// Splice returns an error if target is the root of a collection and
+// newsubtree is a snapshot of a file.
+func Splice(fs FileSystem, target string, newsubtree *Subtree) error {
+       f, err := fs.OpenFile(target, os.O_WRONLY, 0)
+       if os.IsNotExist(err) {
+               f, err = fs.OpenFile(target, os.O_CREATE|os.O_WRONLY, 0700)
+       }
+       if err != nil {
+               return fmt.Errorf("open %s: %w", target, err)
+       }
+       defer f.Close()
+       return f.Splice(newsubtree)
+}