dep ensure

vendor/github.com/hanwen/go-fuse/fuse/splice_linux.go

@@ -0,0 +1,97 @@
+// Copyright 2016 the Go-FUSE Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package fuse
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/hanwen/go-fuse/splice"
+)
+
+func (s *Server) setSplice() {
+	s.canSplice = splice.Resizable()
+}
+
+// trySplice:  Zero-copy read from fdData.Fd into /dev/fuse
+//
+// This is a four-step process:
+//
+//	1) Splice data form fdData.Fd into the "pair1" pipe buffer --> pair1: [payload]
+//	   Now we know the actual payload length and can
+//     construct the reply header
+//	2) Write header into the "pair2" pipe buffer               --> pair2: [header]
+//	4) Splice data from "pair1" into "pair2"                   --> pair2: [header][payload]
+//	3) Splice the data from "pair2" into /dev/fuse
+//
+// This dance is neccessary because header and payload cannot be split across
+// two splices and we cannot seek in a pipe buffer.
+func (ms *Server) trySplice(header []byte, req *request, fdData *readResultFd) error {
+	var err error
+
+	// Get a pair of connected pipes
+	pair1, err := splice.Get()
+	if err != nil {
+		return err
+	}
+	defer splice.Done(pair1)
+
+	// Grow buffer pipe to requested size + one extra page
+	// Without the extra page the kernel will block once the pipe is almost full
+	pair1Sz := fdData.Size() + os.Getpagesize()
+	if err := pair1.Grow(pair1Sz); err != nil {
+		return err
+	}
+
+	// Read data from file
+	payloadLen, err := pair1.LoadFromAt(fdData.Fd, fdData.Size(), fdData.Off)
+
+	if err != nil {
+		// TODO - extract the data from splice.
+		return err
+	}
+
+	// Get another pair of connected pipes
+	pair2, err := splice.Get()
+	if err != nil {
+		return err
+	}
+	defer splice.Done(pair2)
+
+	// Grow pipe to header + actually read size + one extra page
+	// Without the extra page the kernel will block once the pipe is almost full
+	header = req.serializeHeader(payloadLen)
+	total := len(header) + payloadLen
+	pair2Sz := total + os.Getpagesize()
+	if err := pair2.Grow(pair2Sz); err != nil {
+		return err
+	}
+
+	// Write header into pair2
+	n, err := pair2.Write(header)
+	if err != nil {
+		return err
+	}
+	if n != len(header) {
+		return fmt.Errorf("Short write into splice: wrote %d, want %d", n, len(header))
+	}
+
+	// Write data into pair2
+	n, err = pair2.LoadFrom(pair1.ReadFd(), payloadLen)
+	if err != nil {
+		return err
+	}
+	if n != payloadLen {
+		return fmt.Errorf("Short splice: wrote %d, want %d", n, payloadLen)
+	}
+
+	// Write header + data to /dev/fuse
+	_, err = pair2.WriteTo(uintptr(ms.mountFd), total)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}