fuse: remove the 1GiB buffer view limit

fuse/host.go

@@ -17,6 +17,7 @@ import (
 	"os"
 	"os/signal"
 	"path/filepath"
+	"reflect"
 	"runtime"
 	"strings"
 	"sync"
@@ -116,6 +117,18 @@ func recoverAsErrno(errc0 *c_int) {
 	}
 }
 
+func cByteSlice(ptr *c_char, size c_size_t) []byte {
+	if nil == ptr || 0 == size {
+		return nil
+	}
+	slice := reflect.SliceHeader{
+		Data: uintptr(unsafe.Pointer(ptr)),
+		Len:  int(size),
+		Cap:  int(size),
+	}
+	return *(*[]byte)(unsafe.Pointer(&slice))
+}
+
 func hostGetattr(path0 *c_char, stat0 *c_fuse_stat_t, fi0 *c_struct_fuse_file_info) (errc0 c_int) {
 	defer recoverAsErrno(&errc0)
 	fsop := hostHandleGet(c_fuse_get_context().private_data).fsop
@@ -135,7 +148,10 @@ func hostReadlink(path0 *c_char, buff0 *c_char, size0 c_size_t) (errc0 c_int) {
 	fsop := hostHandleGet(c_fuse_get_context().private_data).fsop
 	path := c_GoString(path0)
 	errc, rslt := fsop.Readlink(path)
-	buff := (*[1 << 30]byte)(unsafe.Pointer(buff0))
+	buff := cByteSlice(buff0, size0)
+	if 0 == size0 {
+		return c_int(errc)
+	}
 	copy(buff[:size0-1], rslt)
 	rlen := len(rslt)
 	if c_size_t(rlen) < size0 {
@@ -284,8 +300,8 @@ func hostRead(path0 *c_char, buff0 *c_char, size0 c_size_t, ofst0 c_fuse_off_t,
 	defer recoverAsErrno(&nbyt0)
 	fsop := hostHandleGet(c_fuse_get_context().private_data).fsop
 	path := c_GoString(path0)
-	buff := (*[1 << 30]byte)(unsafe.Pointer(buff0))
-	nbyt := fsop.Read(path, buff[:size0], int64(ofst0), uint64(fi0.fh))
+	buff := cByteSlice(buff0, size0)
+	nbyt := fsop.Read(path, buff, int64(ofst0), uint64(fi0.fh))
 	return c_int(nbyt)
 }
 
@@ -294,8 +310,8 @@ func hostWrite(path0 *c_char, buff0 *c_char, size0 c_size_t, ofst0 c_fuse_off_t,
 	defer recoverAsErrno(&nbyt0)
 	fsop := hostHandleGet(c_fuse_get_context().private_data).fsop
 	path := c_GoString(path0)
-	buff := (*[1 << 30]byte)(unsafe.Pointer(buff0))
-	nbyt := fsop.Write(path, buff[:size0], int64(ofst0), uint64(fi0.fh))
+	buff := cByteSlice(buff0, size0)
+	nbyt := fsop.Write(path, buff, int64(ofst0), uint64(fi0.fh))
 	return c_int(nbyt)
 }
 
@@ -346,8 +362,8 @@ func hostSetxattr(path0 *c_char, name0 *c_char, buff0 *c_char, size0 c_size_t,
 	fsop := hostHandleGet(c_fuse_get_context().private_data).fsop
 	path := c_GoString(path0)
 	name := c_GoString(name0)
-	buff := (*[1 << 30]byte)(unsafe.Pointer(buff0))
-	errc := fsop.Setxattr(path, name, buff[:size0], int(flags))
+	buff := cByteSlice(buff0, size0)
+	errc := fsop.Setxattr(path, name, buff, int(flags))
 	return c_int(errc)
 }
 
@@ -364,8 +380,8 @@ func hostGetxattr(path0 *c_char, name0 *c_char, buff0 *c_char, size0 c_size_t) (
 		if len(rslt) > int(size0) {
 			return -c_int(ERANGE)
 		}
-		buff := (*[1 << 30]byte)(unsafe.Pointer(buff0))
-		copy(buff[:size0], rslt)
+		buff := cByteSlice(buff0, size0)
+		copy(buff, rslt)
 	}
 	return c_int(len(rslt))
 }
@@ -374,7 +390,7 @@ func hostListxattr(path0 *c_char, buff0 *c_char, size0 c_size_t) (nbyt0 c_int) {
 	defer recoverAsErrno(&nbyt0)
 	fsop := hostHandleGet(c_fuse_get_context().private_data).fsop
 	path := c_GoString(path0)
-	buff := (*[1 << 30]byte)(unsafe.Pointer(buff0))
+	buff := cByteSlice(buff0, size0)
 	size := int(size0)
 	nbyt := 0
 	fill := func(name1 string) bool {
@@ -599,7 +615,10 @@ func hostGetpath(path0 *c_char, buff0 *c_char, size0 c_size_t,
 		fifh = uint64(fi0.fh)
 	}
 	errc, rslt := intf.Getpath(path, fifh)
-	buff := (*[1 << 30]byte)(unsafe.Pointer(buff0))
+	buff := cByteSlice(buff0, size0)
+	if 0 == size0 {
+		return c_int(errc)
+	}
 	copy(buff[:size0-1], rslt)
 	rlen := len(rslt)
 	if c_size_t(rlen) < size0 {

fuse/host_buffer_test.go

@@ -0,0 +1,48 @@
+/*
+ * host_buffer_test.go
+ *
+ * Copyright 2017-2022 Bill Zissimopoulos
+ */
+/*
+ * This file is part of Cgofuse.
+ *
+ * It is licensed under the MIT license. The full license text can be found
+ * in the License.txt file at the root of this project.
+ */
+
+package fuse
+
+import (
+	"testing"
+	"unsafe"
+)
+
+func TestCByteSliceZeroInputs(t *testing.T) {
+	if got := cByteSlice(nil, 1); nil != got {
+		t.Fatal("expected nil slice for nil pointer")
+	}
+
+	buf := []byte{'a'}
+	if got := cByteSlice((*c_char)(unsafe.Pointer(&buf[0])), 0); nil != got {
+		t.Fatal("expected nil slice for zero-sized request")
+	}
+}
+
+func TestCByteSliceSharesBuffer(t *testing.T) {
+	buf := []byte{'a', 'b', 'c'}
+	view := cByteSlice((*c_char)(unsafe.Pointer(&buf[0])), c_size_t(len(buf)))
+
+	if len(view) != len(buf) {
+		t.Fatalf("unexpected slice length: got %d want %d", len(view), len(buf))
+	}
+
+	view[1] = 'x'
+	if buf[1] != 'x' {
+		t.Fatal("expected view writes to update the original buffer")
+	}
+
+	buf[2] = 'y'
+	if view[2] != 'y' {
+		t.Fatal("expected original buffer writes to update the view")
+	}
+}