72 lines
1.9 KiB
Go
72 lines
1.9 KiB
Go
// Copyright 2020 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// +build linux
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// Package iovec provides helpers to interact with vectorized I/O on host
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// system.
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package iovec
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import (
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"golang.org/x/sys/unix"
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)
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// MaxIovs is the maximum number of iovecs host platform can accept.
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var MaxIovs = 1024
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// Builder is a builder for slice of unix.Iovec.
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type Builder struct {
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iovec []unix.Iovec
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storage [8]unix.Iovec
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// overflow tracks the last buffer when iovec length is at MaxIovs.
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overflow []byte
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}
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// Add adds buf to b preparing to be written. Zero-length buf won't be added.
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func (b *Builder) Add(buf []byte) {
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if len(buf) == 0 {
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return
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}
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if b.iovec == nil {
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b.iovec = b.storage[:0]
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}
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if len(b.iovec) >= MaxIovs {
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b.addByAppend(buf)
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return
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}
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b.iovec = append(b.iovec, unix.Iovec{Base: &buf[0]})
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b.iovec[len(b.iovec)-1].SetLen(len(buf))
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// Keep the last buf if iovec is at max capacity. We will need to append to it
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// for later bufs.
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if len(b.iovec) == MaxIovs {
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n := len(buf)
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b.overflow = buf[:n:n]
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}
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}
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func (b *Builder) addByAppend(buf []byte) {
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b.overflow = append(b.overflow, buf...)
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b.iovec[len(b.iovec)-1] = unix.Iovec{Base: &b.overflow[0]}
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b.iovec[len(b.iovec)-1].SetLen(len(b.overflow))
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}
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// Build returns the final Iovec slice. The length of returned iovec will not
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// excceed MaxIovs.
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func (b *Builder) Build() []unix.Iovec {
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return b.iovec
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}
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