Add function generating array of iovec with different FUSE structs

This commit adds a function in the newly created fuse_util library,
which accepts a variable number of arguments and data structures.

Fixes #3609

test/fuse/linux/BUILD

@@ -12,6 +12,7 @@ cc_binary(
     deps = [
         gtest,
         ":fuse_base",
+        "//test/util:fuse_util",
         "//test/util:test_main",
         "//test/util:test_util",
     ],
@@ -24,6 +25,7 @@ cc_library(
     hdrs = ["fuse_base.h"],
     deps = [
         gtest,
+        "//test/util:fuse_util",
         "//test/util:posix_error",
         "//test/util:temp_path",
         "//test/util:test_util",

test/fuse/linux/fuse_base.cc

@@ -26,6 +26,7 @@
 
 #include "absl/strings/str_format.h"
 #include "gtest/gtest.h"
+#include "test/util/fuse_util.h"
 #include "test/util/posix_error.h"
 #include "test/util/temp_path.h"
 #include "test/util/test_util.h"
@@ -137,7 +138,6 @@ PosixError FuseTest::ServerConsumeFuseInit() {
   RETURN_ERROR_IF_SYSCALL_FAIL(
       RetryEINTR(read)(dev_fd_, buf.data(), buf.size()));
 
-  struct iovec iov_out[2];
   struct fuse_out_header out_header = {
       .len = sizeof(struct fuse_out_header) + sizeof(struct fuse_init_out),
       .error = 0,
@@ -148,12 +148,10 @@ PosixError FuseTest::ServerConsumeFuseInit() {
   struct fuse_init_out out_payload = {
       .major = 7,
   };
-  iov_out[0].iov_len = sizeof(out_header);
-  iov_out[0].iov_base = &out_header;
-  iov_out[1].iov_len = sizeof(out_payload);
-  iov_out[1].iov_base = &out_payload;
+  auto iov_out = FuseGenerateIovecs(out_header, out_payload);
 
-  RETURN_ERROR_IF_SYSCALL_FAIL(RetryEINTR(writev)(dev_fd_, iov_out, 2));
+  RETURN_ERROR_IF_SYSCALL_FAIL(
+      RetryEINTR(writev)(dev_fd_, iov_out.data(), iov_out.size()));
   return NoError();
 }
 

test/fuse/linux/stat_test.cc

@@ -24,6 +24,7 @@
 
 #include "gtest/gtest.h"
 #include "test/fuse/linux/fuse_base.h"
+#include "test/util/fuse_util.h"
 #include "test/util/test_util.h"
 
 namespace gvisor {
@@ -43,16 +44,10 @@ class StatTest : public FuseTest {
 
 TEST_F(StatTest, StatNormal) {
   // Set up fixture.
-  std::vector<struct iovec> iov_in(2);
-  std::vector<struct iovec> iov_out(2);
   mode_t expected_mode = S_IRWXU | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH;
   struct timespec atime = {.tv_sec = 1595436289, .tv_nsec = 134150844};
   struct timespec mtime = {.tv_sec = 1595436290, .tv_nsec = 134150845};
   struct timespec ctime = {.tv_sec = 1595436291, .tv_nsec = 134150846};
-  struct fuse_out_header out_header = {
-      .len = sizeof(struct fuse_out_header) + sizeof(struct fuse_attr_out),
-      .error = 0,
-  };
   struct fuse_attr attr = {
       .ino = 1,
       .size = 512,
@@ -70,14 +65,13 @@ TEST_F(StatTest, StatNormal) {
       .rdev = 12,
       .blksize = 4096,
   };
+  struct fuse_out_header out_header = {
+      .len = sizeof(struct fuse_out_header) + sizeof(struct fuse_attr_out),
+  };
   struct fuse_attr_out out_payload = {
       .attr = attr,
   };
-  iov_out[0].iov_len = sizeof(out_header);
-  iov_out[0].iov_base = &out_header;
-  iov_out[1].iov_len = sizeof(out_payload);
-  iov_out[1].iov_base = &out_payload;
-
+  auto iov_out = FuseGenerateIovecs(out_header, out_payload);
   SetServerResponse(FUSE_GETATTR, iov_out);
 
   // Do integration test.
@@ -104,10 +98,7 @@ TEST_F(StatTest, StatNormal) {
   // Check FUSE request.
   struct fuse_in_header in_header;
   struct fuse_getattr_in in_payload;
-  iov_in[0].iov_len = sizeof(in_header);
-  iov_in[0].iov_base = &in_header;
-  iov_in[1].iov_len = sizeof(in_payload);
-  iov_in[1].iov_base = &in_payload;
+  auto iov_in = FuseGenerateIovecs(in_header, in_payload);
 
   GetServerActualRequest(iov_in);
   EXPECT_EQ(in_header.opcode, FUSE_GETATTR);
@@ -117,14 +108,11 @@ TEST_F(StatTest, StatNormal) {
 
 TEST_F(StatTest, StatNotFound) {
   // Set up fixture.
-  std::vector<struct iovec> iov_in(2);
-  std::vector<struct iovec> iov_out(1);
   struct fuse_out_header out_header = {
       .len = sizeof(struct fuse_out_header),
       .error = -ENOENT,
   };
-  iov_out[0].iov_len = sizeof(out_header);
-  iov_out[0].iov_base = &out_header;
+  auto iov_out = FuseGenerateIovecs(out_header);
   SetServerResponse(FUSE_GETATTR, iov_out);
 
   // Do integration test.
@@ -135,10 +123,7 @@ TEST_F(StatTest, StatNotFound) {
   // Check FUSE request.
   struct fuse_in_header in_header;
   struct fuse_getattr_in in_payload;
-  iov_in[0].iov_len = sizeof(in_header);
-  iov_in[0].iov_base = &in_header;
-  iov_in[1].iov_len = sizeof(in_payload);
-  iov_in[1].iov_base = &in_payload;
+  auto iov_in = FuseGenerateIovecs(in_header, in_payload);
 
   GetServerActualRequest(iov_in);
   EXPECT_EQ(in_header.opcode, FUSE_GETATTR);

test/util/BUILD

@@ -45,6 +45,12 @@ cc_library(
     ],
 )
 
+cc_library(
+    name = "fuse_util",
+    testonly = 1,
+    hdrs = ["fuse_util.h"],
+)
+
 cc_library(
     name = "proc_util",
     testonly = 1,

test/util/fuse_util.h

@@ -0,0 +1,67 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef GVISOR_TEST_UTIL_FUSE_UTIL_H_
+#define GVISOR_TEST_UTIL_FUSE_UTIL_H_
+
+#include <sys/uio.h>
+
+#include <string>
+#include <vector>
+
+namespace gvisor {
+namespace testing {
+
+// The fundamental generation function with a single argument. If passed by
+// std::string or std::vector<char>, it will call specialized versions as
+// implemented below.
+template <typename T>
+std::vector<struct iovec> FuseGenerateIovecs(T &first) {
+  return {(struct iovec){.iov_base = &first, .iov_len = sizeof(first)}};
+}
+
+// If an argument is of type std::string, it must be used in read-only scenario.
+// Because we are setting up iovec, which contains the original address of a
+// data structure, we have to drop const qualification. Usually used with
+// variable-length payload data.
+template <typename T = std::string>
+std::vector<struct iovec> FuseGenerateIovecs(std::string &first) {
+  // Pad one byte for null-terminate c-string.
+  return {(struct iovec){.iov_base = const_cast<char *>(first.c_str()),
+                         .iov_len = first.size() + 1}};
+}
+
+// If an argument is of type std::vector<char>, it must be used in write-only
+// scenario and the size of the variable must be greater than or equal to the
+// size of the expected data. Usually used with variable-length payload data.
+template <typename T = std::vector<char>>
+std::vector<struct iovec> FuseGenerateIovecs(std::vector<char> &first) {
+  return {(struct iovec){.iov_base = first.data(), .iov_len = first.size()}};
+}
+
+// A helper function to set up an array of iovec struct for testing purpose.
+// Use variadic class template to generalize different numbers and different
+// types of FUSE structs.
+template <typename T, typename... Types>
+std::vector<struct iovec> FuseGenerateIovecs(T &first, Types &...args) {
+  auto first_iovec = FuseGenerateIovecs(first);
+  auto iovecs = FuseGenerateIovecs(args...);
+  first_iovec.insert(std::end(first_iovec), std::begin(iovecs),
+                     std::end(iovecs));
+  return first_iovec;
+}
+
+}  // namespace testing
+}  // namespace gvisor
+#endif  // GVISOR_TEST_UTIL_FUSE_UTIL_H_