1 files changed, 54 insertions, 0 deletions
diff --git a/vendor/github.com/prometheus/tsdb/fileutil/preallocate.go b/vendor/github.com/prometheus/tsdb/fileutil/preallocate.go
new file mode 100644
index 000000000..c747b7cf8
--- /dev/null
+++ b/vendor/github.com/prometheus/tsdb/fileutil/preallocate.go
@@ -0,0 +1,54 @@
+// Copyright 2015 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package fileutil
+
+import (
+	"io"
+	"os"
+)
+
+// Preallocate tries to allocate the space for given
+// file. This operation is only supported on linux by a
+// few filesystems (btrfs, ext4, etc.).
+// If the operation is unsupported, no error will be returned.
+// Otherwise, the error encountered will be returned.
+func Preallocate(f *os.File, sizeInBytes int64, extendFile bool) error {
+	if sizeInBytes == 0 {
+		// fallocate will return EINVAL if length is 0; skip
+		return nil
+	}
+	if extendFile {
+		return preallocExtend(f, sizeInBytes)
+	}
+	return preallocFixed(f, sizeInBytes)
+}
+
+func preallocExtendTrunc(f *os.File, sizeInBytes int64) error {
+	curOff, err := f.Seek(0, io.SeekCurrent)
+	if err != nil {
+		return err
+	}
+	size, err := f.Seek(sizeInBytes, io.SeekEnd)
+	if err != nil {
+		return err
+	}
+	if _, err = f.Seek(curOff, io.SeekStart); err != nil {
+		return err
+	}
+	if sizeInBytes > size {
+		return nil
+	}
+	return f.Truncate(sizeInBytes)
+}