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authorTaru Karttunen <taruti@taruti.net>2017-09-12 19:06:47 +0300
committerJeremy Stribling <strib@alum.mit.edu>2017-11-27 11:43:01 -0800
commit3834e571da171844efecc4e26fd89082419079a1 (patch)
tree32756a7a66fcf746574393fbba478bc8aac7b368 /storage
parent702718fd59be0aa4b8bf8492403c465107ca17af (diff)
downloadgo-git-3834e571da171844efecc4e26fd89082419079a1.tar.gz
Use optionally locking when updating refs
Diffstat (limited to 'storage')
-rw-r--r--storage/filesystem/internal/dotgit/dotgit.go62
-rw-r--r--storage/filesystem/internal/dotgit/dotgit_test.go6
-rw-r--r--storage/filesystem/reference.go6
-rw-r--r--storage/memory/storage.go15
4 files changed, 76 insertions, 13 deletions
diff --git a/storage/filesystem/internal/dotgit/dotgit.go b/storage/filesystem/internal/dotgit/dotgit.go
index 0c9cd33..e60ffca 100644
--- a/storage/filesystem/internal/dotgit/dotgit.go
+++ b/storage/filesystem/internal/dotgit/dotgit.go
@@ -5,6 +5,7 @@ import (
"bufio"
"errors"
"fmt"
+ "io"
stdioutil "io/ioutil"
"os"
"strings"
@@ -239,7 +240,39 @@ func (d *DotGit) Object(h plumbing.Hash) (billy.File, error) {
return d.fs.Open(file)
}
-func (d *DotGit) SetRef(r *plumbing.Reference) error {
+func (d *DotGit) readReferenceFrom(rd io.Reader, name string) (ref *plumbing.Reference, err error) {
+ b, err := stdioutil.ReadAll(rd)
+ if err != nil {
+ return nil, err
+ }
+
+ line := strings.TrimSpace(string(b))
+ return plumbing.NewReferenceFromStrings(name, line), nil
+}
+
+func (d *DotGit) checkReferenceAndTruncate(f billy.File, old *plumbing.Reference) error {
+ if old == nil {
+ return nil
+ }
+ ref, err := d.readReferenceFrom(f, old.Name().String())
+ if err != nil {
+ return err
+ }
+ if ref.Hash() != old.Hash() {
+ return fmt.Errorf("reference has changed concurrently")
+ }
+ _, err = f.Seek(0, io.SeekStart)
+ if err != nil {
+ return err
+ }
+ err = f.Truncate(0)
+ if err != nil {
+ return err
+ }
+ return nil
+}
+
+func (d *DotGit) SetRef(r, old *plumbing.Reference) error {
var content string
switch r.Type() {
case plumbing.SymbolicReference:
@@ -248,13 +281,30 @@ func (d *DotGit) SetRef(r *plumbing.Reference) error {
content = fmt.Sprintln(r.Hash().String())
}
- f, err := d.fs.Create(r.Name().String())
+ // If we are not checking an old ref, just truncate the file.
+ mode := os.O_RDWR | os.O_CREATE
+ if old == nil {
+ mode |= os.O_TRUNC
+ }
+
+ f, err := d.fs.OpenFile(r.Name().String(), mode, 0666)
if err != nil {
return err
}
defer ioutil.CheckClose(f, &err)
+ err = f.Lock()
+ if err != nil {
+ return err
+ }
+
+ // this is a no-op to call even when old is nil.
+ err = d.checkReferenceAndTruncate(f, old)
+ if err != nil {
+ return err
+ }
+
_, err = f.Write([]byte(content))
return err
}
@@ -493,13 +543,7 @@ func (d *DotGit) readReferenceFile(path, name string) (ref *plumbing.Reference,
}
defer ioutil.CheckClose(f, &err)
- b, err := stdioutil.ReadAll(f)
- if err != nil {
- return nil, err
- }
-
- line := strings.TrimSpace(string(b))
- return plumbing.NewReferenceFromStrings(name, line), nil
+ return d.readReferenceFrom(f, name)
}
// Module return a billy.Filesystem poiting to the module folder
diff --git a/storage/filesystem/internal/dotgit/dotgit_test.go b/storage/filesystem/internal/dotgit/dotgit_test.go
index 7d327c8..119d952 100644
--- a/storage/filesystem/internal/dotgit/dotgit_test.go
+++ b/storage/filesystem/internal/dotgit/dotgit_test.go
@@ -58,21 +58,21 @@ func (s *SuiteDotGit) TestSetRefs(c *C) {
err = dir.SetRef(plumbing.NewReferenceFromStrings(
"refs/heads/foo",
"e8d3ffab552895c19b9fcf7aa264d277cde33881",
- ))
+ ), nil)
c.Assert(err, IsNil)
err = dir.SetRef(plumbing.NewReferenceFromStrings(
"refs/heads/symbolic",
"ref: refs/heads/foo",
- ))
+ ), nil)
c.Assert(err, IsNil)
err = dir.SetRef(plumbing.NewReferenceFromStrings(
"bar",
"e8d3ffab552895c19b9fcf7aa264d277cde33881",
- ))
+ ), nil)
c.Assert(err, IsNil)
refs, err := dir.Refs()
diff --git a/storage/filesystem/reference.go b/storage/filesystem/reference.go
index 49627d3..54cdf56 100644
--- a/storage/filesystem/reference.go
+++ b/storage/filesystem/reference.go
@@ -11,7 +11,11 @@ type ReferenceStorage struct {
}
func (r *ReferenceStorage) SetReference(ref *plumbing.Reference) error {
- return r.dir.SetRef(ref)
+ return r.dir.SetRef(ref, nil)
+}
+
+func (r *ReferenceStorage) CheckAndSetReference(ref, old *plumbing.Reference) error {
+ return r.dir.SetRef(ref, old)
}
func (r *ReferenceStorage) Reference(n plumbing.ReferenceName) (*plumbing.Reference, error) {
diff --git a/storage/memory/storage.go b/storage/memory/storage.go
index 2380fed..69394af 100644
--- a/storage/memory/storage.go
+++ b/storage/memory/storage.go
@@ -12,6 +12,7 @@ import (
)
var ErrUnsupportedObjectType = fmt.Errorf("unsupported object type")
+var ErrRefHasChanged = fmt.Errorf("reference has changed concurrently")
// Storage is an implementation of git.Storer that stores data on memory, being
// ephemeral. The use of this storage should be done in controlled envoriments,
@@ -202,6 +203,20 @@ func (r ReferenceStorage) SetReference(ref *plumbing.Reference) error {
return nil
}
+func (r ReferenceStorage) CheckAndSetReference(ref, old *plumbing.Reference) error {
+ if ref != nil {
+ if old != nil {
+ tmp := r[ref.Name()]
+ if tmp != nil && tmp.Hash() != old.Hash() {
+ return ErrRefHasChanged
+ }
+ }
+ r[ref.Name()] = ref
+ }
+
+ return nil
+}
+
func (r ReferenceStorage) Reference(n plumbing.ReferenceName) (*plumbing.Reference, error) {
ref, ok := r[n]
if !ok {