1 files changed, 90 insertions, 0 deletions
diff --git a/pkg/sentry/kernel/pipe/buffer.go b/pkg/sentry/kernel/pipe/buffer.go
new file mode 100644
index 000000000..4360dc44f
--- /dev/null
+++ b/pkg/sentry/kernel/pipe/buffer.go
@@ -0,0 +1,90 @@
+// Copyright 2018 The gVisor 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 pipe
+
+import (
+	"sync"
+
+	"gvisor.googlesource.com/gvisor/pkg/sentry/safemem"
+)
+
+// buffer encapsulates a queueable byte buffer.
+//
+// Note that the total size is slightly less than two pages. This
+// is done intentionally to ensure that the buffer object aligns
+// with runtime internals. We have no hard size or alignment
+// requirements. This two page size will effectively minimize
+// internal fragmentation, but still have a large enough chunk
+// to limit excessive segmentation.
+//
+// +stateify savable
+type buffer struct {
+	data  [8144]byte
+	read  int
+	write int
+	bufferEntry
+}
+
+// Reset resets internal data.
+//
+// This must be called before use.
+func (b *buffer) Reset() {
+	b.read = 0
+	b.write = 0
+}
+
+// Empty indicates the buffer is empty.
+//
+// This indicates there is no data left to read.
+func (b *buffer) Empty() bool {
+	return b.read == b.write
+}
+
+// Full indicates the buffer is full.
+//
+// This indicates there is no capacity left to write.
+func (b *buffer) Full() bool {
+	return b.write == len(b.data)
+}
+
+// WriteFromBlocks implements safemem.Writer.WriteFromBlocks.
+func (b *buffer) WriteFromBlocks(srcs safemem.BlockSeq) (uint64, error) {
+	dst := safemem.BlockSeqOf(safemem.BlockFromSafeSlice(b.data[b.write:]))
+	n, err := safemem.CopySeq(dst, srcs)
+	b.write += int(n)
+	return n, err
+}
+
+// ReadToBlocks implements safemem.Reader.ReadToBlocks.
+func (b *buffer) ReadToBlocks(dsts safemem.BlockSeq) (uint64, error) {
+	src := safemem.BlockSeqOf(safemem.BlockFromSafeSlice(b.data[b.read:b.write]))
+	n, err := safemem.CopySeq(dsts, src)
+	b.read += int(n)
+	return n, err
+}
+
+// bufferPool is a pool for buffers.
+var bufferPool = sync.Pool{
+	New: func() interface{} {
+		return new(buffer)
+	},
+}
+
+// newBuffer grabs a new buffer from the pool.
+func newBuffer() *buffer {
+	b := bufferPool.Get().(*buffer)
+	b.Reset()
+	return b
+}