127 lines
3.1 KiB
Go
127 lines
3.1 KiB
Go
// Copyright 2015 Google Inc. All Rights Reserved.
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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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package buffer
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import (
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"fmt"
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"io"
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"syscall"
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"unsafe"
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"github.com/jacobsa/fuse/internal/fusekernel"
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)
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// All requests read from the kernel, without data, are shorter than
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// this.
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var pageSize int
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// We size the buffer to have enough room for a fuse request plus data
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// associated with a write request.
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var bufSize int
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func init() {
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pageSize = syscall.Getpagesize()
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bufSize = pageSize + MaxWriteSize
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}
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// An incoming message from the kernel, including leading fusekernel.InHeader
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// struct. Provides storage for messages and convenient access to their
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// contents.
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type InMessage struct {
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remaining []byte
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storage []byte
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size int
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}
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// NewInMessage creates a new InMessage with its storage initialized.
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func NewInMessage() *InMessage {
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return &InMessage{
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storage: make([]byte, bufSize),
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}
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}
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// Initialize with the data read by a single call to r.Read. The first call to
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// Consume will consume the bytes directly after the fusekernel.InHeader
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// struct.
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func (m *InMessage) Init(r io.Reader) error {
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n, err := r.Read(m.storage[:])
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if err != nil {
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return err
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}
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// Make sure the message is long enough.
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const headerSize = unsafe.Sizeof(fusekernel.InHeader{})
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if uintptr(n) < headerSize {
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return fmt.Errorf("Unexpectedly read only %d bytes.", n)
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}
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m.size = n
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m.remaining = m.storage[headerSize:n]
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// Check the header's length.
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if int(m.Header().Len) != n {
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return fmt.Errorf(
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"Header says %d bytes, but we read %d",
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m.Header().Len,
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n)
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}
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return nil
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}
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// Return a reference to the header read in the most recent call to Init.
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func (m *InMessage) Header() *fusekernel.InHeader {
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return (*fusekernel.InHeader)(unsafe.Pointer(&m.storage[0]))
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}
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// Return the number of bytes left to consume.
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func (m *InMessage) Len() uintptr {
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return uintptr(len(m.remaining))
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}
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// Consume the next n bytes from the message, returning a nil pointer if there
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// are fewer than n bytes available.
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func (m *InMessage) Consume(n uintptr) unsafe.Pointer {
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if m.Len() == 0 || n > m.Len() {
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return nil
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}
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p := unsafe.Pointer(&m.remaining[0])
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m.remaining = m.remaining[n:]
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return p
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}
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// Equivalent to Consume, except returns a slice of bytes. The result will be
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// nil if Consume would fail.
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func (m *InMessage) ConsumeBytes(n uintptr) []byte {
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if n > m.Len() {
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return nil
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}
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b := m.remaining[:n]
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m.remaining = m.remaining[n:]
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return b
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}
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// Get the next n bytes after the message to use them as a temporary buffer
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func (m *InMessage) GetFree(n int) []byte {
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if n <= 0 || n > len(m.storage)-m.size {
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return nil
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}
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return m.storage[m.size : m.size+n]
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}
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