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authorFlorian Weimer <fweimer@redhat.com>2018-07-06 16:53:48 +0200
committerFlorian Weimer <fweimer@redhat.com>2018-07-06 17:52:54 +0200
commit3f5e3f5d066dcffb80af48ae2cf35a01a85a8f10 (patch)
tree2eb99509fbdfb5f61ee40bdf634c63f092b85ae2 /libio
parent397c54c1afa531242602fe3ac7bb47eff0e909f9 (diff)
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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.
Diffstat (limited to 'libio')
-rw-r--r--libio/Makefile4
-rw-r--r--libio/Versions4
-rw-r--r--libio/fseeko.c12
-rw-r--r--libio/fseeko64.c5
-rw-r--r--libio/ftello.c8
-rw-r--r--libio/ftello64.c5
-rw-r--r--libio/readline.c170
-rw-r--r--libio/tst-readline.c236
8 files changed, 435 insertions, 9 deletions
diff --git a/libio/Makefile b/libio/Makefile
index 64d283e..cab0eae 100644
--- a/libio/Makefile
+++ b/libio/Makefile
@@ -49,7 +49,7 @@ routines := \
__fbufsize __freading __fwriting __freadable __fwritable __flbf \
__fpurge __fpending __fsetlocking \
\
- libc_fatal fmemopen oldfmemopen vtables
+ libc_fatal fmemopen oldfmemopen vtables readline
tests = tst_swprintf tst_wprintf tst_swscanf tst_wscanf tst_getwc tst_putwc \
tst_wprintf2 tst-widetext test-fmemopen tst-ext tst-ext2 \
@@ -66,7 +66,7 @@ tests = tst_swprintf tst_wprintf tst_swscanf tst_wscanf tst_getwc tst_putwc \
tst-fwrite-error tst-ftell-partial-wide tst-ftell-active-handler \
tst-ftell-append tst-fputws tst-bz22415 tst-fgetc-after-eof
-tests-internal = tst-vtables tst-vtables-interposed
+tests-internal = tst-vtables tst-vtables-interposed tst-readline
ifeq (yes,$(build-shared))
# Add test-fopenloc only if shared library is enabled since it depends on
diff --git a/libio/Versions b/libio/Versions
index 7712334..acb896a 100644
--- a/libio/Versions
+++ b/libio/Versions
@@ -158,5 +158,9 @@ libc {
# Used by NPTL
_IO_enable_locks;
+
+ __fseeko64;
+ __ftello64;
+ __libc_readline_unlocked;
}
}
diff --git a/libio/fseeko.c b/libio/fseeko.c
index 2df0453..4d086c1 100644
--- a/libio/fseeko.c
+++ b/libio/fseeko.c
@@ -24,11 +24,15 @@
This exception applies to code released by its copyright holders
in files containing the exception. */
+/* We need to disable the redirect for __fseeko64 for the alias
+ definitions below to work. */
+#define __fseeko64 __fseeko64_disable
+
#include "libioP.h"
#include "stdio.h"
int
-fseeko (FILE *fp, off_t offset, int whence)
+__fseeko (FILE *fp, off_t offset, int whence)
{
int result;
CHECK_FILE (fp, -1);
@@ -37,7 +41,11 @@ fseeko (FILE *fp, off_t offset, int whence)
_IO_release_lock (fp);
return result;
}
+weak_alias (__fseeko, fseeko)
#ifdef __OFF_T_MATCHES_OFF64_T
-weak_alias (fseeko, fseeko64)
+weak_alias (__fseeko, fseeko64)
+# undef __fseeko64
+strong_alias (__fseeko, __fseeko64)
+libc_hidden_ver (__fseeko, __fseeko64)
#endif
diff --git a/libio/fseeko64.c b/libio/fseeko64.c
index eea6455..1d9bb19 100644
--- a/libio/fseeko64.c
+++ b/libio/fseeko64.c
@@ -32,7 +32,7 @@
#ifndef __OFF_T_MATCHES_OFF64_T
int
-fseeko64 (FILE *fp, off64_t offset, int whence)
+__fseeko64 (FILE *fp, off64_t offset, int whence)
{
int result;
CHECK_FILE (fp, -1);
@@ -41,5 +41,6 @@ fseeko64 (FILE *fp, off64_t offset, int whence)
_IO_release_lock (fp);
return result;
}
-
+libc_hidden_def (__fseeko64)
+weak_alias (__fseeko64, fseeko64)
#endif
diff --git a/libio/ftello.c b/libio/ftello.c
index 5405821..5a3caf4 100644
--- a/libio/ftello.c
+++ b/libio/ftello.c
@@ -24,12 +24,15 @@
This exception applies to code released by its copyright holders
in files containing the exception. */
+/* We need to disable the redirect for __ftello64 for the alias
+ definitions below to work. */
+#define __ftello64 __ftello64_disable
+
#include <stdio.h>
#include <stdlib.h>
#include <libioP.h>
#include <errno.h>
-
off_t
__ftello (FILE *fp)
{
@@ -61,4 +64,7 @@ weak_alias (__ftello, ftello)
#ifdef __OFF_T_MATCHES_OFF64_T
weak_alias (__ftello, ftello64)
+# undef __ftello64
+strong_alias (__ftello, __ftello64)
+libc_hidden_ver (__ftello, __ftello64)
#endif
diff --git a/libio/ftello64.c b/libio/ftello64.c
index 281667f..d5546e1 100644
--- a/libio/ftello64.c
+++ b/libio/ftello64.c
@@ -32,7 +32,7 @@
#ifndef __OFF_T_MATCHES_OFF64_T
off64_t
-ftello64 (FILE *fp)
+__ftello64 (FILE *fp)
{
off64_t pos;
CHECK_FILE (fp, -1L);
@@ -52,5 +52,6 @@ ftello64 (FILE *fp)
}
return pos;
}
-
+libc_hidden_def (__ftello64)
+weak_alias (__ftello64, ftello64)
#endif
diff --git a/libio/readline.c b/libio/readline.c
new file mode 100644
index 0000000..3638459
--- /dev/null
+++ b/libio/readline.c
@@ -0,0 +1,170 @@
+/* fgets with ERANGE error reporting and size_t buffer length.
+ 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/>. */
+
+#include <assert.h>
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "libioP.h"
+
+/* Return -1 and set errno to EINVAL if it is ERANGE. */
+static ssize_t
+fail_no_erange (void)
+{
+ if (errno == ERANGE)
+ __set_errno (EINVAL);
+ return -1;
+}
+
+/* Slow path for reading the line. Called with no data in the stream
+ read buffer. Write data to [BUFFER, BUFFER_END). */
+static ssize_t
+readline_slow (FILE *fp, char *buffer, char *buffer_end)
+{
+ char *start = buffer;
+
+ while (buffer < buffer_end)
+ {
+ if (__underflow (fp) == EOF)
+ {
+ if (_IO_ferror_unlocked (fp))
+ /* If the EOF was caused by a read error, report it. */
+ return fail_no_erange ();
+ *buffer = '\0';
+ /* Do not include the null terminator. */
+ return buffer - start;
+ }
+
+ /* __underflow has filled the buffer. */
+ char *readptr = fp->_IO_read_ptr;
+ ssize_t readlen = fp->_IO_read_end - readptr;
+ /* Make sure that __underflow really has acquired some data. */
+ assert (readlen > 0);
+ char *pnl = memchr (readptr, '\n', readlen);
+ if (pnl != NULL)
+ {
+ /* We found the terminator. */
+ size_t line_length = pnl - readptr;
+ if (line_length + 2 > buffer_end - buffer)
+ /* Not enough room in the caller-supplied buffer. */
+ break;
+ memcpy (buffer, readptr, line_length + 1);
+ buffer[line_length + 1] = '\0';
+ fp->_IO_read_ptr = pnl + 1;
+ /* Do not include the null terminator. */
+ return buffer - start + line_length + 1;
+ }
+
+ if (readlen >= buffer_end - buffer)
+ /* Not enough room in the caller-supplied buffer. */
+ break;
+
+ /* Save and consume the stream buffer. */
+ memcpy (buffer, readptr, readlen);
+ fp->_IO_read_ptr = fp->_IO_read_end;
+ buffer += readlen;
+ }
+
+ /* The line does not fit into the buffer. */
+ __set_errno (ERANGE);
+ return -1;
+}
+
+ssize_t
+__libc_readline_unlocked (FILE *fp, char *buffer, size_t buffer_length)
+{
+ char *buffer_end = buffer + buffer_length;
+
+ /* Orient the stream. */
+ if (__builtin_expect (fp->_mode, -1) == 0)
+ _IO_fwide (fp, -1);
+
+ /* Fast path: The line terminator is found in the buffer. */
+ char *readptr = fp->_IO_read_ptr;
+ ssize_t readlen = fp->_IO_read_end - readptr;
+ off64_t start_offset; /* File offset before reading anything. */
+ if (readlen > 0)
+ {
+ char *pnl = memchr (readptr, '\n', readlen);
+ if (pnl != NULL)
+ {
+ size_t line_length = pnl - readptr;
+ /* Account for line and null terminators. */
+ if (line_length + 2 > buffer_length)
+ {
+ __set_errno (ERANGE);
+ return -1;
+ }
+ memcpy (buffer, readptr, line_length + 1);
+ buffer[line_length + 1] = '\0';
+ /* Consume the entire line. */
+ fp->_IO_read_ptr = pnl + 1;
+ return line_length + 1;
+ }
+
+ /* If the buffer does not have enough space for what is pending
+ in the stream (plus a NUL terminator), the buffer is too
+ small. */
+ if (readlen + 1 > buffer_length)
+ {
+ __set_errno (ERANGE);
+ return -1;
+ }
+
+ /* End of line not found. We need all the buffered data. Fall
+ through to the slow path. */
+ memcpy (buffer, readptr, readlen);
+ buffer += readlen;
+ /* The original length is invalid after this point. Use
+ buffer_end instead. */
+#pragma GCC poison buffer_length
+ /* Read the old offset before updating the read pointer. */
+ start_offset = __ftello64 (fp);
+ fp->_IO_read_ptr = fp->_IO_read_end;
+ }
+ else
+ {
+ readlen = 0;
+ start_offset = __ftello64 (fp);
+ }
+
+ /* Slow path: Read more data from the underlying file. We need to
+ restore the file pointer if the buffer is too small. First,
+ check if the __ftello64 call above failed. */
+ if (start_offset < 0)
+ return fail_no_erange ();
+
+ ssize_t result = readline_slow (fp, buffer, buffer_end);
+ if (result < 0)
+ {
+ if (errno == ERANGE)
+ {
+ /* Restore the file pointer so that the caller may read the
+ same line again. */
+ if (__fseeko64 (fp, start_offset, SEEK_SET) < 0)
+ return fail_no_erange ();
+ __set_errno (ERANGE);
+ }
+ /* Do not restore the file position on other errors; it is
+ likely that the __fseeko64 call would fail, too. */
+ return -1;
+ }
+ return readlen + result;
+}
+libc_hidden_def (__libc_readline_unlocked)
diff --git a/libio/tst-readline.c b/libio/tst-readline.c
new file mode 100644
index 0000000..60c58c6
--- /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>