1 files changed, 131 insertions, 0 deletions
diff --git a/pkg/buffer/safemem.go b/pkg/buffer/safemem.go
new file mode 100644
index 000000000..071aaa488
--- /dev/null
+++ b/pkg/buffer/safemem.go
@@ -0,0 +1,131 @@
+// Copyright 2020 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 buffer
+
+import (
+	"io"
+
+	"gvisor.dev/gvisor/pkg/safemem"
+)
+
+// WriteBlock returns this buffer as a write Block.
+func (b *Buffer) WriteBlock() safemem.Block {
+	return safemem.BlockFromSafeSlice(b.data[b.write:])
+}
+
+// ReadBlock returns this buffer as a read Block.
+func (b *Buffer) ReadBlock() safemem.Block {
+	return safemem.BlockFromSafeSlice(b.data[b.read:b.write])
+}
+
+// WriteFromBlocks implements safemem.Writer.WriteFromBlocks.
+//
+// This will advance the write index.
+func (v *View) WriteFromBlocks(srcs safemem.BlockSeq) (uint64, error) {
+	need := int(srcs.NumBytes())
+	if need == 0 {
+		return 0, nil
+	}
+
+	var (
+		dst    safemem.BlockSeq
+		blocks []safemem.Block
+	)
+
+	// Need at least one buffer.
+	firstBuf := v.data.Back()
+	if firstBuf == nil {
+		firstBuf = bufferPool.Get().(*Buffer)
+		v.data.PushBack(firstBuf)
+	}
+
+	// Does the last block have sufficient capacity alone?
+	if l := len(firstBuf.data) - firstBuf.write; l >= need {
+		dst = safemem.BlockSeqOf(firstBuf.WriteBlock())
+	} else {
+		// Append blocks until sufficient.
+		need -= l
+		blocks = append(blocks, firstBuf.WriteBlock())
+		for need > 0 {
+			emptyBuf := bufferPool.Get().(*Buffer)
+			v.data.PushBack(emptyBuf)
+			need -= len(emptyBuf.data) // Full block.
+			blocks = append(blocks, emptyBuf.WriteBlock())
+		}
+		dst = safemem.BlockSeqFromSlice(blocks)
+	}
+
+	// Perform the copy.
+	n, err := safemem.CopySeq(dst, srcs)
+	v.size += int64(n)
+
+	// Update all indices.
+	for left := int(n); left > 0; firstBuf = firstBuf.Next() {
+		if l := len(firstBuf.data) - firstBuf.write; left >= l {
+			firstBuf.write += l // Whole block.
+			left -= l
+		} else {
+			firstBuf.write += left // Partial block.
+			left = 0
+		}
+	}
+
+	return n, err
+}
+
+// ReadToBlocks implements safemem.Reader.ReadToBlocks.
+//
+// This will not advance the read index; the caller should follow
+// this call with a call to TrimFront in order to remove the read
+// data from the buffer. This is done to support pipe sematics.
+func (v *View) ReadToBlocks(dsts safemem.BlockSeq) (uint64, error) {
+	need := int(dsts.NumBytes())
+	if need == 0 {
+		return 0, nil
+	}
+
+	var (
+		src    safemem.BlockSeq
+		blocks []safemem.Block
+	)
+
+	firstBuf := v.data.Front()
+	if firstBuf == nil {
+		return 0, io.EOF
+	}
+
+	// Is all the data in a single block?
+	if l := firstBuf.write - firstBuf.read; l >= need {
+		src = safemem.BlockSeqOf(firstBuf.ReadBlock())
+	} else {
+		// Build a list of all the buffers.
+		need -= l
+		blocks = append(blocks, firstBuf.ReadBlock())
+		for buf := firstBuf.Next(); buf != nil && need > 0; buf = buf.Next() {
+			need -= buf.write - buf.read
+			blocks = append(blocks, buf.ReadBlock())
+		}
+		src = safemem.BlockSeqFromSlice(blocks)
+	}
+
+	// Perform the copy.
+	n, err := safemem.CopySeq(dsts, src)
+
+	// See above: we would normally advance the read index here, but we
+	// don't do that in order to support pipe semantics. We rely on a
+	// separate call to TrimFront() in this case.
+
+	return n, err
+}