1 files changed, 87 insertions, 0 deletions
diff --git a/vendor/google.golang.org/appengine/datastore/transaction.go b/vendor/google.golang.org/appengine/datastore/transaction.go
new file mode 100644
index 000000000..a7f3f2b28
--- /dev/null
+++ b/vendor/google.golang.org/appengine/datastore/transaction.go
@@ -0,0 +1,87 @@
+// Copyright 2011 Google Inc. All rights reserved.
+// Use of this source code is governed by the Apache 2.0
+// license that can be found in the LICENSE file.
+
+package datastore
+
+import (
+	"errors"
+
+	"golang.org/x/net/context"
+
+	"google.golang.org/appengine/internal"
+	pb "google.golang.org/appengine/internal/datastore"
+)
+
+func init() {
+	internal.RegisterTransactionSetter(func(x *pb.Query, t *pb.Transaction) {
+		x.Transaction = t
+	})
+	internal.RegisterTransactionSetter(func(x *pb.GetRequest, t *pb.Transaction) {
+		x.Transaction = t
+	})
+	internal.RegisterTransactionSetter(func(x *pb.PutRequest, t *pb.Transaction) {
+		x.Transaction = t
+	})
+	internal.RegisterTransactionSetter(func(x *pb.DeleteRequest, t *pb.Transaction) {
+		x.Transaction = t
+	})
+}
+
+// ErrConcurrentTransaction is returned when a transaction is rolled back due
+// to a conflict with a concurrent transaction.
+var ErrConcurrentTransaction = errors.New("datastore: concurrent transaction")
+
+// RunInTransaction runs f in a transaction. It calls f with a transaction
+// context tc that f should use for all App Engine operations.
+//
+// If f returns nil, RunInTransaction attempts to commit the transaction,
+// returning nil if it succeeds. If the commit fails due to a conflicting
+// transaction, RunInTransaction retries f, each time with a new transaction
+// context. It gives up and returns ErrConcurrentTransaction after three
+// failed attempts. The number of attempts can be configured by specifying
+// TransactionOptions.Attempts.
+//
+// If f returns non-nil, then any datastore changes will not be applied and
+// RunInTransaction returns that same error. The function f is not retried.
+//
+// Note that when f returns, the transaction is not yet committed. Calling code
+// must be careful not to assume that any of f's changes have been committed
+// until RunInTransaction returns nil.
+//
+// Since f may be called multiple times, f should usually be idempotent.
+// datastore.Get is not idempotent when unmarshaling slice fields.
+//
+// Nested transactions are not supported; c may not be a transaction context.
+func RunInTransaction(c context.Context, f func(tc context.Context) error, opts *TransactionOptions) error {
+	xg := false
+	if opts != nil {
+		xg = opts.XG
+	}
+	attempts := 3
+	if opts != nil && opts.Attempts > 0 {
+		attempts = opts.Attempts
+	}
+	for i := 0; i < attempts; i++ {
+		if err := internal.RunTransactionOnce(c, f, xg); err != internal.ErrConcurrentTransaction {
+			return err
+		}
+	}
+	return ErrConcurrentTransaction
+}
+
+// TransactionOptions are the options for running a transaction.
+type TransactionOptions struct {
+	// XG is whether the transaction can cross multiple entity groups. In
+	// comparison, a single group transaction is one where all datastore keys
+	// used have the same root key. Note that cross group transactions do not
+	// have the same behavior as single group transactions. In particular, it
+	// is much more likely to see partially applied transactions in different
+	// entity groups, in global queries.
+	// It is valid to set XG to true even if the transaction is within a
+	// single entity group.
+	XG bool
+	// Attempts controls the number of retries to perform when commits fail
+	// due to a conflicting transaction. If omitted, it defaults to 3.
+	Attempts int
+}