Add support/ code for checking file contents

For use in freopen tests, add various support/ helper interfaces for
use in checking file contents.

Tested for x86_64.

support/Makefile

@@ -49,6 +49,8 @@ libsupport-routines = \
   support_check_stat_fd \
   support_check_stat_path \
   support_chroot \
+  support_compare_file_bytes \
+  support_compare_file_string \
   support_copy_file \
   support_copy_file_range \
   support_create_timer \
@@ -65,6 +67,8 @@ libsupport-routines = \
   support_isolate_in_subprocess \
   support_mutex_pi_monotonic \
   support_need_proc \
+  support_open_and_compare_file_bytes \
+  support_open_and_compare_file_string \
   support_openpty \
   support_path_support_time64 \
   support_paths \

support/file_contents.h

@@ -0,0 +1,63 @@
+/* Functionality for checking file contents.
+   Copyright (C) 2024 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef SUPPORT_FILE_CONTENTS_H
+#define SUPPORT_FILE_CONTENTS_H
+
+#include <support/check.h>
+#include <stdio.h>
+
+__BEGIN_DECLS
+
+/* Check that an already-open file has exactly the given bytes,
+   starting at the current location in the file.  The file position
+   indicator is updated to point after the bytes compared.  Return 0
+   if equal, 1 otherwise or on read error.  */
+int support_compare_file_bytes (FILE *fp, const char *contents, size_t length);
+
+/* Check that an already-open file has exactly the given string as
+   contents, starting at the current offset.  The file position
+   indicator is updated to point after the bytes compared.  Return 0
+   if equal, 1 otherwise or on read error.  */
+int support_compare_file_string (FILE *fp, const char *contents);
+
+/* Check that a not-currently-open file has exactly the given bytes.
+   Return 0 if equal, 1 otherwise or on read error.  */
+int support_open_and_compare_file_bytes (const char *file,
+					 const char *contents,
+					 size_t length);
+
+/* Check that a not-currently-open file has exactly the given string
+   as contents, starting at the current offset.  Return 0 if equal, 1
+   otherwise or on read error.  */
+int support_open_and_compare_file_string (const char *file,
+					  const char *contents);
+
+/* Compare bytes read from an open file with the given string.  The
+   file position indicator is updated to point after the bytes
+   compared.  */
+#define TEST_COMPARE_FILE_STRING(FP, CONTENTS)			\
+  TEST_COMPARE (support_compare_file_string (FP, CONTENTS), 0)
+
+/* Read a file and compare bytes read from it with the given string.  */
+#define TEST_OPEN_AND_COMPARE_FILE_STRING(FILE, CONTENTS)		\
+  TEST_COMPARE (support_open_and_compare_file_string (FILE, CONTENTS), 0)
+
+__END_DECLS
+
+#endif /* SUPPORT_FILE_CONTENTS_H */

support/support_compare_file_bytes.c

@@ -0,0 +1,42 @@
+/* Compare bytes from an open file.
+   Copyright (C) 2024 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <stdio.h>
+
+#include <support/file_contents.h>
+
+/* Check that an already-open file has exactly the given bytes,
+   starting at the current offset.  */
+
+int
+support_compare_file_bytes (FILE *fp, const char *contents, size_t length)
+{
+  int c;
+  while (length > 0)
+    {
+      c = getc (fp);
+      if (c == EOF || (unsigned char) c != (unsigned char) contents[0])
+	return 1;
+      contents++;
+      length--;
+    }
+  c = getc (fp);
+  if (c != EOF || ferror (fp))
+    return 1;
+  return 0;
+}

support/support_compare_file_string.c

@@ -0,0 +1,28 @@
+/* Compare string from an open file.
+   Copyright (C) 2024 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <stdio.h>
+#include <string.h>
+
+#include <support/file_contents.h>
+
+int
+support_compare_file_string (FILE *fp, const char *contents)
+{
+  return support_compare_file_bytes (fp, contents, strlen (contents));
+}

support/support_open_and_compare_file_bytes.c

@@ -0,0 +1,33 @@
+/* Compare bytes from a file.
+   Copyright (C) 2024 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <support/file_contents.h>
+#include <support/xstdio.h>
+
+/* Check that a not-currently-open file has exactly the given
+   bytes.  */
+
+int
+support_open_and_compare_file_bytes (const char *file, const char *contents,
+				     size_t length)
+{
+  FILE *fp = xfopen (file, "r");
+  int ret = support_compare_file_bytes (fp, contents, length);
+  xfclose (fp);
+  return ret;
+}

support/support_open_and_compare_file_string.c

@@ -0,0 +1,32 @@
+/* Compare string from a file.
+   Copyright (C) 2024 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <string.h>
+
+#include <support/file_contents.h>
+#include <support/xstdio.h>
+
+/* Check that a not-currently-open file has exactly the given string
+   as contents, starting at the current offset.  */
+
+int
+support_open_and_compare_file_string (const char *file, const char *contents)
+{
+  return support_open_and_compare_file_bytes (file, contents,
+					      strlen (contents));
+}