1 files changed, 395 insertions, 0 deletions
diff --git a/src/os/readfrom_linux_test.go b/src/os/readfrom_linux_test.go
new file mode 100644
index 0000000..1d145da
--- /dev/null
+++ b/src/os/readfrom_linux_test.go
@@ -0,0 +1,395 @@
+// Copyright 2020 The Go 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 os_test
+
+import (
+	"bytes"
+	"internal/poll"
+	"io"
+	"math/rand"
+	"os"
+	. "os"
+	"path/filepath"
+	"strconv"
+	"syscall"
+	"testing"
+	"time"
+)
+
+func TestCopyFileRange(t *testing.T) {
+	sizes := []int{
+		1,
+		42,
+		1025,
+		syscall.Getpagesize() + 1,
+		32769,
+	}
+	t.Run("Basic", func(t *testing.T) {
+		for _, size := range sizes {
+			t.Run(strconv.Itoa(size), func(t *testing.T) {
+				testCopyFileRange(t, int64(size), -1)
+			})
+		}
+	})
+	t.Run("Limited", func(t *testing.T) {
+		t.Run("OneLess", func(t *testing.T) {
+			for _, size := range sizes {
+				t.Run(strconv.Itoa(size), func(t *testing.T) {
+					testCopyFileRange(t, int64(size), int64(size)-1)
+				})
+			}
+		})
+		t.Run("Half", func(t *testing.T) {
+			for _, size := range sizes {
+				t.Run(strconv.Itoa(size), func(t *testing.T) {
+					testCopyFileRange(t, int64(size), int64(size)/2)
+				})
+			}
+		})
+		t.Run("More", func(t *testing.T) {
+			for _, size := range sizes {
+				t.Run(strconv.Itoa(size), func(t *testing.T) {
+					testCopyFileRange(t, int64(size), int64(size)+7)
+				})
+			}
+		})
+	})
+	t.Run("DoesntTryInAppendMode", func(t *testing.T) {
+		dst, src, data, hook := newCopyFileRangeTest(t, 42)
+
+		dst2, err := OpenFile(dst.Name(), O_RDWR|O_APPEND, 0755)
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer dst2.Close()
+
+		if _, err := io.Copy(dst2, src); err != nil {
+			t.Fatal(err)
+		}
+		if hook.called {
+			t.Fatal("called poll.CopyFileRange for destination in O_APPEND mode")
+		}
+		mustSeekStart(t, dst2)
+		mustContainData(t, dst2, data) // through traditional means
+	})
+	t.Run("NotRegular", func(t *testing.T) {
+		t.Run("BothPipes", func(t *testing.T) {
+			hook := hookCopyFileRange(t)
+
+			pr1, pw1, err := Pipe()
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer pr1.Close()
+			defer pw1.Close()
+
+			pr2, pw2, err := Pipe()
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer pr2.Close()
+			defer pw2.Close()
+
+			// The pipe is empty, and PIPE_BUF is large enough
+			// for this, by (POSIX) definition, so there is no
+			// need for an additional goroutine.
+			data := []byte("hello")
+			if _, err := pw1.Write(data); err != nil {
+				t.Fatal(err)
+			}
+			pw1.Close()
+
+			n, err := io.Copy(pw2, pr1)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if n != int64(len(data)) {
+				t.Fatalf("transfered %d, want %d", n, len(data))
+			}
+			if !hook.called {
+				t.Fatalf("should have called poll.CopyFileRange")
+			}
+			pw2.Close()
+			mustContainData(t, pr2, data)
+		})
+		t.Run("DstPipe", func(t *testing.T) {
+			dst, src, data, hook := newCopyFileRangeTest(t, 255)
+			dst.Close()
+
+			pr, pw, err := Pipe()
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer pr.Close()
+			defer pw.Close()
+
+			n, err := io.Copy(pw, src)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if n != int64(len(data)) {
+				t.Fatalf("transfered %d, want %d", n, len(data))
+			}
+			if !hook.called {
+				t.Fatalf("should have called poll.CopyFileRange")
+			}
+			pw.Close()
+			mustContainData(t, pr, data)
+		})
+		t.Run("SrcPipe", func(t *testing.T) {
+			dst, src, data, hook := newCopyFileRangeTest(t, 255)
+			src.Close()
+
+			pr, pw, err := Pipe()
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer pr.Close()
+			defer pw.Close()
+
+			// The pipe is empty, and PIPE_BUF is large enough
+			// for this, by (POSIX) definition, so there is no
+			// need for an additional goroutine.
+			if _, err := pw.Write(data); err != nil {
+				t.Fatal(err)
+			}
+			pw.Close()
+
+			n, err := io.Copy(dst, pr)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if n != int64(len(data)) {
+				t.Fatalf("transfered %d, want %d", n, len(data))
+			}
+			if !hook.called {
+				t.Fatalf("should have called poll.CopyFileRange")
+			}
+			mustSeekStart(t, dst)
+			mustContainData(t, dst, data)
+		})
+	})
+	t.Run("Nil", func(t *testing.T) {
+		var nilFile *File
+		anyFile, err := os.CreateTemp("", "")
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer Remove(anyFile.Name())
+		defer anyFile.Close()
+
+		if _, err := io.Copy(nilFile, nilFile); err != ErrInvalid {
+			t.Errorf("io.Copy(nilFile, nilFile) = %v, want %v", err, ErrInvalid)
+		}
+		if _, err := io.Copy(anyFile, nilFile); err != ErrInvalid {
+			t.Errorf("io.Copy(anyFile, nilFile) = %v, want %v", err, ErrInvalid)
+		}
+		if _, err := io.Copy(nilFile, anyFile); err != ErrInvalid {
+			t.Errorf("io.Copy(nilFile, anyFile) = %v, want %v", err, ErrInvalid)
+		}
+
+		if _, err := nilFile.ReadFrom(nilFile); err != ErrInvalid {
+			t.Errorf("nilFile.ReadFrom(nilFile) = %v, want %v", err, ErrInvalid)
+		}
+		if _, err := anyFile.ReadFrom(nilFile); err != ErrInvalid {
+			t.Errorf("anyFile.ReadFrom(nilFile) = %v, want %v", err, ErrInvalid)
+		}
+		if _, err := nilFile.ReadFrom(anyFile); err != ErrInvalid {
+			t.Errorf("nilFile.ReadFrom(anyFile) = %v, want %v", err, ErrInvalid)
+		}
+	})
+}
+
+func testCopyFileRange(t *testing.T, size int64, limit int64) {
+	dst, src, data, hook := newCopyFileRangeTest(t, size)
+
+	// If we have a limit, wrap the reader.
+	var (
+		realsrc io.Reader
+		lr      *io.LimitedReader
+	)
+	if limit >= 0 {
+		lr = &io.LimitedReader{N: limit, R: src}
+		realsrc = lr
+		if limit < int64(len(data)) {
+			data = data[:limit]
+		}
+	} else {
+		realsrc = src
+	}
+
+	// Now call ReadFrom (through io.Copy), which will hopefully call
+	// poll.CopyFileRange.
+	n, err := io.Copy(dst, realsrc)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// If we didn't have a limit, we should have called poll.CopyFileRange
+	// with the right file descriptor arguments.
+	if limit > 0 && !hook.called {
+		t.Fatal("never called poll.CopyFileRange")
+	}
+	if hook.called && hook.dstfd != int(dst.Fd()) {
+		t.Fatalf("wrong destination file descriptor: got %d, want %d", hook.dstfd, dst.Fd())
+	}
+	if hook.called && hook.srcfd != int(src.Fd()) {
+		t.Fatalf("wrong source file descriptor: got %d, want %d", hook.srcfd, src.Fd())
+	}
+
+	// Check that the offsets after the transfer make sense, that the size
+	// of the transfer was reported correctly, and that the destination
+	// file contains exactly the bytes we expect it to contain.
+	dstoff, err := dst.Seek(0, io.SeekCurrent)
+	if err != nil {
+		t.Fatal(err)
+	}
+	srcoff, err := src.Seek(0, io.SeekCurrent)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if dstoff != srcoff {
+		t.Errorf("offsets differ: dstoff = %d, srcoff = %d", dstoff, srcoff)
+	}
+	if dstoff != int64(len(data)) {
+		t.Errorf("dstoff = %d, want %d", dstoff, len(data))
+	}
+	if n != int64(len(data)) {
+		t.Errorf("short ReadFrom: wrote %d bytes, want %d", n, len(data))
+	}
+	mustSeekStart(t, dst)
+	mustContainData(t, dst, data)
+
+	// If we had a limit, check that it was updated.
+	if lr != nil {
+		if want := limit - n; lr.N != want {
+			t.Fatalf("didn't update limit correctly: got %d, want %d", lr.N, want)
+		}
+	}
+}
+
+// newCopyFileRangeTest initializes a new test for copy_file_range.
+//
+// It creates source and destination files, and populates the source file
+// with random data of the specified size. It also hooks package os' call
+// to poll.CopyFileRange and returns the hook so it can be inspected.
+func newCopyFileRangeTest(t *testing.T, size int64) (dst, src *File, data []byte, hook *copyFileRangeHook) {
+	t.Helper()
+
+	hook = hookCopyFileRange(t)
+	tmp := t.TempDir()
+
+	src, err := Create(filepath.Join(tmp, "src"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { src.Close() })
+
+	dst, err = Create(filepath.Join(tmp, "dst"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { dst.Close() })
+
+	// Populate the source file with data, then rewind it, so it can be
+	// consumed by copy_file_range(2).
+	prng := rand.New(rand.NewSource(time.Now().Unix()))
+	data = make([]byte, size)
+	prng.Read(data)
+	if _, err := src.Write(data); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := src.Seek(0, io.SeekStart); err != nil {
+		t.Fatal(err)
+	}
+
+	return dst, src, data, hook
+}
+
+// mustContainData ensures that the specified file contains exactly the
+// specified data.
+func mustContainData(t *testing.T, f *File, data []byte) {
+	t.Helper()
+
+	got := make([]byte, len(data))
+	if _, err := io.ReadFull(f, got); err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(got, data) {
+		t.Fatalf("didn't get the same data back from %s", f.Name())
+	}
+	if _, err := f.Read(make([]byte, 1)); err != io.EOF {
+		t.Fatalf("not at EOF")
+	}
+}
+
+func mustSeekStart(t *testing.T, f *File) {
+	if _, err := f.Seek(0, io.SeekStart); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func hookCopyFileRange(t *testing.T) *copyFileRangeHook {
+	h := new(copyFileRangeHook)
+	h.install()
+	t.Cleanup(h.uninstall)
+	return h
+}
+
+type copyFileRangeHook struct {
+	called bool
+	dstfd  int
+	srcfd  int
+	remain int64
+
+	original func(dst, src *poll.FD, remain int64) (int64, bool, error)
+}
+
+func (h *copyFileRangeHook) install() {
+	h.original = *PollCopyFileRangeP
+	*PollCopyFileRangeP = func(dst, src *poll.FD, remain int64) (int64, bool, error) {
+		h.called = true
+		h.dstfd = dst.Sysfd
+		h.srcfd = src.Sysfd
+		h.remain = remain
+		return h.original(dst, src, remain)
+	}
+}
+
+func (h *copyFileRangeHook) uninstall() {
+	*PollCopyFileRangeP = h.original
+}
+
+// On some kernels copy_file_range fails on files in /proc.
+func TestProcCopy(t *testing.T) {
+	const cmdlineFile = "/proc/self/cmdline"
+	cmdline, err := os.ReadFile(cmdlineFile)
+	if err != nil {
+		t.Skipf("can't read /proc file: %v", err)
+	}
+	in, err := os.Open(cmdlineFile)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer in.Close()
+	outFile := filepath.Join(t.TempDir(), "cmdline")
+	out, err := os.Create(outFile)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := io.Copy(out, in); err != nil {
+		t.Fatal(err)
+	}
+	if err := out.Close(); err != nil {
+		t.Fatal(err)
+	}
+	copy, err := os.ReadFile(outFile)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(cmdline, copy) {
+		t.Errorf("copy of %q got %q want %q\n", cmdlineFile, copy, cmdline)
+	}
+}