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// 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
}
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