Add direct copy

common/bufio/splice_linux.go

@@ -0,0 +1,79 @@
+package bufio
+
+import (
+	"syscall"
+
+	E "github.com/sagernet/sing/common/exceptions"
+	N "github.com/sagernet/sing/common/network"
+
+	"golang.org/x/sys/unix"
+)
+
+const maxSpliceSize = 1 << 20
+
+func splice(source syscall.RawConn, destination syscall.RawConn, readCounters []N.CountFunc, writeCounters []N.CountFunc) (handed bool, n int64, err error) {
+	handed = true
+	var pipeFDs [2]int
+	err = unix.Pipe2(pipeFDs[:], syscall.O_CLOEXEC|syscall.O_NONBLOCK)
+	if err != nil {
+		return
+	}
+	defer unix.Close(pipeFDs[0])
+	defer unix.Close(pipeFDs[1])
+
+	_, _ = unix.FcntlInt(uintptr(pipeFDs[0]), unix.F_SETPIPE_SZ, maxSpliceSize)
+	var readN int
+	var readErr error
+	var writeErr error
+	readFunc := func(fd uintptr) (done bool) {
+		p0, p1 := unix.Splice(int(fd), nil, pipeFDs[1], nil, maxSpliceSize, unix.SPLICE_F_NONBLOCK)
+		readN = int(p0)
+		readErr = p1
+		return readErr != unix.EAGAIN
+	}
+	writeFunc := func(fd uintptr) (done bool) {
+		var writeN int
+		size := readN
+		for size > 0 {
+			p0, p1 := unix.Splice(pipeFDs[0], nil, int(fd), nil, size, unix.SPLICE_F_NONBLOCK|unix.SPLICE_F_MOVE)
+			writeN = int(p0)
+			writeErr = p1
+			if writeErr != nil {
+				return writeErr != unix.EAGAIN
+			}
+			size -= int(writeN)
+		}
+		return true
+	}
+	for {
+		err = source.Read(readFunc)
+		if err != nil {
+			readErr = err
+		}
+		if readErr != nil {
+			if readErr == unix.EINVAL || readErr == unix.ENOSYS {
+				handed = false
+				return
+			}
+			err = E.Cause(readErr, "splice read")
+			return
+		}
+		if readN == 0 {
+			return
+		}
+		err = destination.Write(writeFunc)
+		if err != nil {
+			writeErr = err
+		}
+		if writeErr != nil {
+			err = E.Cause(writeErr, "splice write")
+			return
+		}
+		for _, readCounter := range readCounters {
+			readCounter(int64(readN))
+		}
+		for _, writeCounter := range writeCounters {
+			writeCounter(int64(readN))
+		}
+	}
+}