libc/test/src/stdio/rewind_test.cpp

//===-- Unittests for file operations like fopen, flcose etc --------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#include "src/__support/CPP/scope.h"
#include "src/stdio/fclose.h"
#include "src/stdio/ferror.h"
#include "src/stdio/fopen.h"
#include "src/stdio/fread.h"
#include "src/stdio/fwrite.h"
#include "src/stdio/rewind.h"
#include "test/UnitTest/ErrnoCheckingTest.h"
#include "test/UnitTest/ErrnoSetterMatcher.h"
#include "test/UnitTest/Test.h"

using LlvmLibcRewindTest = LIBC_NAMESPACE::testing::ErrnoCheckingTest;
using LIBC_NAMESPACE::cpp::scope_exit;
using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Succeeds;

TEST_F(LlvmLibcRewindTest, WriteRewindRead) {
  constexpr char FILENAME[] = "testdata/rewind.test";
  auto FILEPATH = libc_make_test_file_path(FILENAME);
  constexpr char FIRST_DATA[] = "123456789";

  {
    ::FILE *file = LIBC_NAMESPACE::fopen(FILEPATH, "w");
    ASSERT_FALSE(file == nullptr);
    scope_exit close_file([&] { ASSERT_EQ(0, LIBC_NAMESPACE::fclose(file)); });

    ASSERT_THAT(LIBC_NAMESPACE::fwrite(FIRST_DATA, 1, sizeof(FIRST_DATA), file),
                Succeeds(sizeof(FIRST_DATA)));

    // File state is "123456789"

    LIBC_NAMESPACE::rewind(file);

    // Cursor is back to the start

    constexpr char SECOND_DATA[] = "abc";
    ASSERT_THAT(
        LIBC_NAMESPACE::fwrite(SECOND_DATA, 1, sizeof(SECOND_DATA) - 1, file),
        Succeeds(sizeof(SECOND_DATA) - 1));

    // File state is "abc456789"

    // attempt to read from write-only file causing error state
    char read_data[sizeof(FIRST_DATA)];
    ASSERT_EQ(LIBC_NAMESPACE::fread(read_data, 1, sizeof(read_data), file),
              size_t(0));
    ASSERT_ERRNO_FAILURE();
    ASSERT_NE(LIBC_NAMESPACE::ferror(file), 0);

    // rewind to start and check that that clears the error.
    LIBC_NAMESPACE::rewind(file);
    ASSERT_EQ(LIBC_NAMESPACE::ferror(file), 0);
  }

  {
    // Reopen the file in read mode.
    ::FILE *file = LIBC_NAMESPACE::fopen(FILEPATH, "r");
    ASSERT_FALSE(file == nullptr);
    scope_exit close_file([&] { ASSERT_EQ(0, LIBC_NAMESPACE::fclose(file)); });

    char read_data[sizeof(FIRST_DATA)];
    // Read the file to check that it was written correctly.
    ASSERT_THAT(LIBC_NAMESPACE::fread(read_data, 1, 3, file),
                Succeeds(size_t(3)));
    read_data[3] = '\0';
    ASSERT_STREQ(read_data, "abc");
    ASSERT_EQ(LIBC_NAMESPACE::ferror(file), 0);

    // check that rewind also works on read files.
    LIBC_NAMESPACE::rewind(file);
    ASSERT_THAT(LIBC_NAMESPACE::fread(read_data, 1, sizeof(read_data), file),
                Succeeds(sizeof(FIRST_DATA)));
    read_data[sizeof(FIRST_DATA) - 1] = '\0';
    ASSERT_STREQ(read_data, "abc456789");
  }
}