libc/test/src/stdio/fgets_test.cpp

//===-- Unittests for fgets -----------------------------------------------===//
//
// 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/feof.h"
#include "src/stdio/ferror.h"
#include "src/stdio/fgets.h"
#include "src/stdio/fopen.h"
#include "src/stdio/fwrite.h"
#include "test/UnitTest/ErrnoCheckingTest.h"
#include "test/UnitTest/ErrnoSetterMatcher.h"
#include "test/UnitTest/Test.h"

using LlvmLibcFgetsTest = LIBC_NAMESPACE::testing::ErrnoCheckingTest;
using namespace LIBC_NAMESPACE::testing::ErrnoSetterMatcher;
using LIBC_NAMESPACE::cpp::scope_exit;

TEST_F(LlvmLibcFgetsTest, WriteAndReadCharacters) {
  constexpr char FILENAME[] = "testdata/fgets.test";
  char buff[8];
  char *output;

  {
    ::FILE *file = LIBC_NAMESPACE::fopen(FILENAME, "w");
    ASSERT_FALSE(file == nullptr);
    scope_exit close_file(
        [&] { ASSERT_THAT(LIBC_NAMESPACE::fclose(file), Succeeds()); });

    constexpr char CONTENT[] = "123456789\n"
                               "1234567\n"
                               "123456\n"
                               "1";
    constexpr size_t WRITE_SIZE = sizeof(CONTENT) - 1;

    ASSERT_THAT(LIBC_NAMESPACE::fwrite(CONTENT, 1, WRITE_SIZE, file),
                Succeeds(WRITE_SIZE));
    // This is a write-only file so reads should fail.
    ASSERT_THAT(LIBC_NAMESPACE::fgets(buff, 8, file),
                Fails(EBADF, static_cast<char *>(nullptr)));
    // This is an error and not a real EOF.
    ASSERT_EQ(LIBC_NAMESPACE::feof(file), 0);
    ASSERT_NE(LIBC_NAMESPACE::ferror(file), 0);
  }

  {
    ::FILE *file = LIBC_NAMESPACE::fopen(FILENAME, "r");
    ASSERT_FALSE(file == nullptr);
    scope_exit close_file(
        [&] { ASSERT_THAT(LIBC_NAMESPACE::fclose(file), Succeeds()); });

    // The GPU build relies on the host C library, so this check may be
    // different.
#ifndef LIBC_TARGET_ARCH_IS_GPU
    // If we request just 1 byte, it should return just a null byte and not
    // advance the read head. This is implementation defined.
    output = LIBC_NAMESPACE::fgets(buff, 1, file);
    ASSERT_TRUE(output == buff);
    ASSERT_EQ(buff[0], '\0');
    ASSERT_ERRNO_SUCCESS();

    // If we request less than 1 byte, it should do nothing and return nullptr.
    // This is also implementation defined.
    output = LIBC_NAMESPACE::fgets(buff, 0, file);
    ASSERT_TRUE(output == nullptr);
    ASSERT_ERRNO_SUCCESS();
#endif

    const char *output_arr[] = {
        "1234567", "89\n", "1234567", "\n", "123456\n", "1",
    };

    constexpr size_t ARR_SIZE = sizeof(output_arr) / sizeof(char *);

    for (size_t i = 0; i < ARR_SIZE; ++i) {
      output = LIBC_NAMESPACE::fgets(buff, 8, file);

      // This pointer comparison is intentional, fgets should return a pointer
      // to buff when it succeeds.
      ASSERT_TRUE(output == buff);
      ASSERT_EQ(LIBC_NAMESPACE::ferror(file), 0);

      EXPECT_STREQ(buff, output_arr[i]);
    }

    // This should have hit the end of the file, but that isn't an error unless
    // it fails to read anything.
    ASSERT_NE(LIBC_NAMESPACE::feof(file), 0);
    ASSERT_EQ(LIBC_NAMESPACE::ferror(file), 0);
    ASSERT_ERRNO_SUCCESS();

    // Reading more should be an EOF, but not an error.
    output = LIBC_NAMESPACE::fgets(buff, 8, file);
    ASSERT_TRUE(output == nullptr);
    ASSERT_NE(LIBC_NAMESPACE::feof(file), 0);
    ASSERT_ERRNO_SUCCESS();
  }
}