libio: Implement internal function __libc_readline_unlocked

This is a variant of fgets which fails with ERANGE if the
buffer is too small, and the buffer length is given as an
argument of type size_t.

This function will be useful for implementing NSS file reading
operations.  Compared to a direct implementation using the public API,
it avoids an lseek system call in case the line terminator can be
found in the internal read buffer.

1 files changed, 236 insertions, 0 deletions

diff --git a/libio/tst-readline.c b/libio/tst-readline.c
new file mode 100644
index 0000000000..60c58c650a
--- /dev/null
+++ b/libio/tst-readline.c
@@ -0,0 +1,236 @@
+/* Test the __libc_readline_unlocked function.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+/* Exercise __libc_readline_unlocked with various combinations of line
+   lengths, stdio buffer sizes, and line read buffer sizes.  */
+
+#include <errno.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/temp_file.h>
+#include <support/test-driver.h>
+#include <support/xmemstream.h>
+#include <support/xstdio.h>
+#include <support/xunistd.h>
+
+enum
+  {
+    maximum_line_length = 7,
+    number_of_lines = 3,
+  };
+
+/* -1: Do not set buffer size.  0: unbuffered.  Otherwise, use this as
+   the size of the buffer.  */
+static int buffer_size;
+
+/* These size of the buffer used for reading.  Must be at least 2.  */
+static int read_size;
+
+/* If a read files with ERANGE, increase the buffer size by this
+   amount.  Must be positive.  */
+static int read_size_increment;
+
+/* If non-zero, do not reset the read size after an ERANGE error.  */
+static int read_size_preserve;
+
+/* If non-zero, no '\n' at the end of the file.  */
+static int no_newline_at_eof;
+
+/* Length of the line, or -1 if the line is not present.  */
+static int line_lengths[number_of_lines];
+
+/* The name of the test file.  */
+static char *test_file_path;
+
+/* The contents of the test file.  */
+static char expected_contents[(maximum_line_length + 2) * number_of_lines + 1];
+static size_t expected_length;
+
+/* Returns a random byte which is not zero or the line terminator.  */
+static char
+random_char (void)
+{
+  static unsigned int rand_state = 1;
+  while (true)
+    {
+      char result = rand_r (&rand_state) >> 16;
+      if (result != 0 && result != '\n')
+        return result;
+    }
+}
+
+/* Create the test file.  */
+static void
+prepare (int argc, char **argv)
+{
+  int fd = create_temp_file ("tst-readline-", &test_file_path);
+  TEST_VERIFY_EXIT (fd >= 0);
+  xclose (fd);
+}
+
+/* Prepare the test file.  Return false if the test parameters are
+   incongruent and the test should be skipped.  */
+static bool
+write_test_file (void)
+{
+  expected_length = 0;
+  char *p = expected_contents;
+  for (int lineno = 0; lineno < number_of_lines; ++lineno)
+    for (int i = 0; i < line_lengths[lineno]; ++i)
+      *p++ = random_char ();
+  expected_length = p - &expected_contents[0];
+  if (no_newline_at_eof)
+    {
+      if (expected_length == 0)
+        return false;
+      --expected_length;
+      --p;
+    }
+  if (test_verbose > 0)
+    {
+      printf ("info: writing test file of %zu bytes:\n", expected_length);
+      for (int i = 0; i < number_of_lines; ++i)
+        printf (" line %d: %d\n", i, line_lengths[i]);
+      if (no_newline_at_eof)
+        puts ("  (no newline at EOF)");
+    }
+  TEST_VERIFY_EXIT (expected_length < sizeof (expected_contents));
+  *p++ = '\0';
+  support_write_file_string (test_file_path, expected_contents);
+  return true;
+}
+
+/* Run a single test (a combination of a test file and read
+   parameters).  */
+static void
+run_test (void)
+{
+  TEST_VERIFY_EXIT (read_size_increment > 0);
+  if (test_verbose > 0)
+    {
+      printf ("info: running test: buffer_size=%d read_size=%d\n"
+              "  read_size_increment=%d read_size_preserve=%d\n",
+              buffer_size, read_size, read_size_increment, read_size_preserve);
+    }
+
+  struct xmemstream result;
+  xopen_memstream (&result);
+
+  FILE *fp = xfopen (test_file_path, "rce");
+  char *fp_buffer = NULL;
+  if (buffer_size == 0)
+    TEST_VERIFY_EXIT (setvbuf (fp, NULL, _IONBF, 0) == 0);
+  if (buffer_size > 0)
+    {
+      fp_buffer = xmalloc (buffer_size);
+      TEST_VERIFY_EXIT (setvbuf (fp, fp_buffer, _IOFBF, buffer_size) == 0);
+    }
+
+  char *line_buffer = xmalloc (read_size);
+  size_t line_buffer_size = read_size;
+
+  while (true)
+    {
+      ssize_t ret = __libc_readline_unlocked
+        (fp, line_buffer, line_buffer_size);
+      if (ret < 0)
+        {
+          TEST_VERIFY (ret == -1);
+          if (errno != ERANGE)
+            FAIL_EXIT1 ("__libc_readline_unlocked: %m");
+          line_buffer_size += read_size_increment;
+          free (line_buffer);
+          line_buffer = xmalloc (line_buffer_size);
+          /* Try reading this line again.  */
+        }
+      else if (ret == 0)
+        break;
+      else
+        {
+          /* A line has been read.  Save it.  */
+          TEST_VERIFY (ret == strlen (line_buffer));
+          const char *pnl = strchr (line_buffer, '\n');
+          /* If there is a \n, it must be at the end.  */
+          TEST_VERIFY (pnl == NULL || pnl == line_buffer + ret - 1);
+          fputs (line_buffer, result.out);
+
+          /* Restore the original read size if required.  */
+          if (line_buffer_size > read_size && !read_size_preserve)
+            {
+              line_buffer_size = read_size;
+              free (line_buffer);
+              line_buffer = xmalloc (line_buffer_size);
+            }
+        }
+    }
+
+  xfclose (fp);
+  free (fp_buffer);
+  free (line_buffer);
+
+  xfclose_memstream (&result);
+  TEST_VERIFY (result.length == expected_length);
+  TEST_VERIFY (strcmp (result.buffer, expected_contents) == 0);
+  if (test_verbose > 0)
+    {
+      printf ("info: expected (%zu): [[%s]]\n",
+              expected_length, expected_contents);
+      printf ("info:   actual (%zu): [[%s]]\n", result.length, result.buffer);
+    }
+  free (result.buffer);
+}
+
+/* Test one test file with multiple read parameters.  */
+static void
+test_one_file (void)
+{
+  for (buffer_size = -1; buffer_size <= maximum_line_length + 1; ++buffer_size)
+    for (read_size = 2; read_size <= maximum_line_length + 2; ++read_size)
+      for (read_size_increment = 1; read_size_increment <= 4;
+           ++read_size_increment)
+        for (read_size_preserve = 0; read_size_preserve < 2;
+             ++read_size_preserve)
+          run_test ();
+}
+
+
+static int
+do_test (void)
+{
+  /* Set up the test file contents.  */
+  for (line_lengths[0] = -1; line_lengths[0] <= maximum_line_length;
+       ++line_lengths[0])
+    for (line_lengths[1] = -1; line_lengths[1] <= maximum_line_length;
+         ++line_lengths[1])
+      for (line_lengths[2] = -1; line_lengths[2] <= maximum_line_length;
+           ++line_lengths[2])
+        for (no_newline_at_eof = 0; no_newline_at_eof < 2; ++no_newline_at_eof)
+          {
+            if (!write_test_file ())
+              continue;
+            test_one_file ();
+          }
+  free (test_file_path);
+  return 0;
+}
+
+#define PREPARE prepare
+#include <support/test-driver.c>