[VOL-4291] Rw-core updates for gRPC migration
Change-Id: I8d5a554409115b29318089671ca4e1ab3fa98810
diff --git a/vendor/github.com/coreos/etcd/pkg/ioutil/pagewriter.go b/vendor/github.com/coreos/etcd/pkg/ioutil/pagewriter.go
new file mode 100644
index 0000000..cf9a8dc
--- /dev/null
+++ b/vendor/github.com/coreos/etcd/pkg/ioutil/pagewriter.go
@@ -0,0 +1,117 @@
+// Copyright 2016 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 ioutil
+
+import (
+ "io"
+)
+
+var defaultBufferBytes = 128 * 1024
+
+// PageWriter implements the io.Writer interface so that writes will
+// either be in page chunks or from flushing.
+type PageWriter struct {
+ w io.Writer
+ // pageOffset tracks the page offset of the base of the buffer
+ pageOffset int
+ // pageBytes is the number of bytes per page
+ pageBytes int
+ // bufferedBytes counts the number of bytes pending for write in the buffer
+ bufferedBytes int
+ // buf holds the write buffer
+ buf []byte
+ // bufWatermarkBytes is the number of bytes the buffer can hold before it needs
+ // to be flushed. It is less than len(buf) so there is space for slack writes
+ // to bring the writer to page alignment.
+ bufWatermarkBytes int
+}
+
+// NewPageWriter creates a new PageWriter. pageBytes is the number of bytes
+// to write per page. pageOffset is the starting offset of io.Writer.
+func NewPageWriter(w io.Writer, pageBytes, pageOffset int) *PageWriter {
+ return &PageWriter{
+ w: w,
+ pageOffset: pageOffset,
+ pageBytes: pageBytes,
+ buf: make([]byte, defaultBufferBytes+pageBytes),
+ bufWatermarkBytes: defaultBufferBytes,
+ }
+}
+
+func (pw *PageWriter) Write(p []byte) (n int, err error) {
+ if len(p)+pw.bufferedBytes <= pw.bufWatermarkBytes {
+ // no overflow
+ copy(pw.buf[pw.bufferedBytes:], p)
+ pw.bufferedBytes += len(p)
+ return len(p), nil
+ }
+ // complete the slack page in the buffer if unaligned
+ slack := pw.pageBytes - ((pw.pageOffset + pw.bufferedBytes) % pw.pageBytes)
+ if slack != pw.pageBytes {
+ partial := slack > len(p)
+ if partial {
+ // not enough data to complete the slack page
+ slack = len(p)
+ }
+ // special case: writing to slack page in buffer
+ copy(pw.buf[pw.bufferedBytes:], p[:slack])
+ pw.bufferedBytes += slack
+ n = slack
+ p = p[slack:]
+ if partial {
+ // avoid forcing an unaligned flush
+ return n, nil
+ }
+ }
+ // buffer contents are now page-aligned; clear out
+ if err = pw.Flush(); err != nil {
+ return n, err
+ }
+ // directly write all complete pages without copying
+ if len(p) > pw.pageBytes {
+ pages := len(p) / pw.pageBytes
+ c, werr := pw.w.Write(p[:pages*pw.pageBytes])
+ n += c
+ if werr != nil {
+ return n, werr
+ }
+ p = p[pages*pw.pageBytes:]
+ }
+ // write remaining tail to buffer
+ c, werr := pw.Write(p)
+ n += c
+ return n, werr
+}
+
+// Flush flushes buffered data.
+func (pw *PageWriter) Flush() error {
+ _, err := pw.flush()
+ return err
+}
+
+// FlushN flushes buffered data and returns the number of written bytes.
+func (pw *PageWriter) FlushN() (int, error) {
+ return pw.flush()
+}
+
+func (pw *PageWriter) flush() (int, error) {
+ if pw.bufferedBytes == 0 {
+ return 0, nil
+ }
+ n, err := pw.w.Write(pw.buf[:pw.bufferedBytes])
+ pw.pageOffset = (pw.pageOffset + pw.bufferedBytes) % pw.pageBytes
+ pw.bufferedBytes = 0
+ return n, err
+}