From d7b56e186521ce2e48e27edda121d780a3d62d27 Mon Sep 17 00:00:00 2001

From: Jan Synacek <jsynacek@redhat.com>

Date: Thu, 23 Nov 2017 08:53:50 +0100

Subject: [PATCH] fileio: add new helper call read_line() as bounded getline()

 replacement

read_line() is much like getline(), and returns a line read from a

FILE*, of arbitrary sizes. In contrast to gets() it will grow the buffer

dynamically, and in contrast to getline() it will place a user-specified

boundary on the line.

(cherry-picked from commit 4f9a66a32dda1d9a28f9bb3fa31c2148524bc46a)

Resolves: #1503106

---

 src/shared/fileio.c    | 77 ++++++++++++++++++++++++++++++++++++++++++

 src/shared/fileio.h    |  2 ++

 src/test/test-fileio.c | 44 ++++++++++++++++++++++++

 3 files changed, 123 insertions(+)

diff --git a/src/shared/fileio.c b/src/shared/fileio.c

index ff6b1a7ed..107737573 100644

--- a/src/shared/fileio.c

+++ b/src/shared/fileio.c

@@ -815,3 +815,80 @@ int get_status_field(const char *filename, const char *pattern, char **field) {

         return 0;

 }

+

+int read_line(FILE *f, size_t limit, char **ret) {

+        _cleanup_free_ char *buffer = NULL;

+        size_t n = 0, allocated = 0, count = 0;

+        int r;

+

+        assert(f);

+

+        /* Something like a bounded version of getline().

+         *

+         * Considers EOF, \n and \0 end of line delimiters, and does not include these delimiters in the string

+         * returned.

+         *

+         * Returns the number of bytes read from the files (i.e. including delimiters — this hence usually differs from

+         * the number of characters in the returned string). When EOF is hit, 0 is returned.

+         *

+         * The input parameter limit is the maximum numbers of characters in the returned string, i.e. excluding

+         * delimiters. If the limit is hit we fail and return -ENOBUFS.

+         *

+         * If a line shall be skipped ret may be initialized as NULL. */

+

+        if (ret) {

+                if (!GREEDY_REALLOC(buffer, allocated, 1))

+                        return -ENOMEM;

+        }

+

+        flockfile(f);

+

+        for (;;) {

+                int c;

+

+                if (n >= limit) {

+                        funlockfile(f);

+                        return -ENOBUFS;

+                }

+

+                errno = 0;

+                c = fgetc_unlocked(f);

+                if (c == EOF) {

+                        /* if we read an error, and have no data to return, then propagate the error */

+                        if (ferror_unlocked(f) && n == 0) {

+                                r = errno > 0 ? -errno : -EIO;

+                                funlockfile(f);

+                                return r;

+                        }

+

+                        break;

+                }

+

+                count++;

+

+                if (IN_SET(c, '\n', 0)) /* Reached a delimiter */

+                        break;

+

+                if (ret) {

+                        if (!GREEDY_REALLOC(buffer, allocated, n + 2)) {

+                                funlockfile(f);

+                                return -ENOMEM;

+                        }

+

+                        buffer[n] = (char) c;

+                }

+

+                n++;

+        }

+

+        funlockfile(f);

+

+        if (ret) {

+                buffer[n] = 0;

+

+                *ret = buffer;

+                buffer = NULL;

+        }

+

+        return (int) count;

+}

diff --git a/src/shared/fileio.h b/src/shared/fileio.h

index 5ae51c1e2..f33464dce 100644

--- a/src/shared/fileio.h

+++ b/src/shared/fileio.h

@@ -43,3 +43,5 @@ int write_env_file(const char *fname, char **l);

 int executable_is_script(const char *path, char **interpreter);

 int get_status_field(const char *filename, const char *pattern, char **field);

+

+int read_line(FILE *f, size_t limit, char **ret);

diff --git a/src/test/test-fileio.c b/src/test/test-fileio.c

index 63e4a19b7..fc5969322 100644

--- a/src/test/test-fileio.c

+++ b/src/test/test-fileio.c

@@ -392,6 +392,49 @@ static void test_load_env_file_pairs(void) {

         unlink(fn);

 }

+static void test_read_line(void) {

+        _cleanup_fclose_ FILE *f = NULL;

+        _cleanup_free_ char *line = NULL;

+

+        char buffer[] =

+                "Some test data\n"

+                "With newlines, and a NUL byte\0"

+                "\n"

+                "an empty line\n"

+                "an ignored line\n"

+                "and a very long line that is supposed to be truncated, because it is so long\n";

+

+        f = fmemopen(buffer, sizeof(buffer), "re");

+        assert_se(f);

+

+        assert_se(read_line(f, (size_t) -1, &line) == 15 && streq(line, "Some test data"));

+        line = mfree(line);

+

+        assert_se(read_line(f, 1024, &line) == 30 && streq(line, "With newlines, and a NUL byte"));

+        line = mfree(line);

+

+        assert_se(read_line(f, 1024, &line) == 1 && streq(line, ""));

+        line = mfree(line);

+

+        assert_se(read_line(f, 1024, &line) == 14 && streq(line, "an empty line"));

+        line = mfree(line);

+

+        assert_se(read_line(f, (size_t) -1, NULL) == 16);

+

+        assert_se(read_line(f, 16, &line) == -ENOBUFS);

+        line = mfree(line);

+

+        /* read_line() stopped when it hit the limit, that means when we continue reading we'll read at the first

+         * character after the previous limit. Let's make use of tha to continue our test. */

+        assert_se(read_line(f, 1024, &line) == 61 && streq(line, "line that is supposed to be truncated, because it is so long"));

+        line = mfree(line);

+

+        assert_se(read_line(f, 1024, &line) == 1 && streq(line, ""));

+        line = mfree(line);

+

+        assert_se(read_line(f, 1024, &line) == 0 && streq(line, ""));

+}

+

 int main(int argc, char *argv[]) {

         log_parse_environment();

         log_open();

@@ -405,6 +448,7 @@ int main(int argc, char *argv[]) {

         test_write_string_file();

         test_write_string_file_no_create();

         test_load_env_file_pairs();

+        test_read_line();

         return 0;

 }