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 ff6b1a7ed7..1077375735 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 5ae51c1e28..f33464dce7 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 63e4a19b76..fc59693228 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;
}