string-util: rework strextend() to optionally inset separators between each appended...

This adds a new flavour of strextend(), called
strextend_with_separator(), which takes an optional separator string. If
specified, the separator is inserted between each appended string, as
well as before the first one, but only if the original string was
non-empty.

This new call is particularly useful when appending new options to mount
option strings and suchlike, which need to be comma-separated, and
initially start out from an empty string.

diff --git a/src/basic/string-util.c b/src/basic/string-util.c
index 312e83433e4e5ec9723e54be34f31070f40504db..e916000b25bb274c330907d88310f22c7d8e2384 100644 (file)
--- a/src/basic/string-util.c
+++ b/src/basic/string-util.c
@@ -734,16 +734,20 @@ char *strip_tab_ansi(char **ibuf, size_t *_isz) {
         return obuf;
 }
 
-char *strextend(char **x, ...) {
-        va_list ap;
-        size_t f, l;
+char *strextend_with_separator(char **x, const char *separator, ...) {
+        bool need_separator;
+        size_t f, l, l_separator;
         char *r, *p;
+        va_list ap;
 
         assert(x);
 
         l = f = strlen_ptr(*x);
 
-        va_start(ap, x);
+        need_separator = !isempty(*x);
+        l_separator = strlen_ptr(separator);
+
+        va_start(ap, separator);
         for (;;) {
                 const char *t;
                 size_t n;
@@ -753,22 +757,29 @@ char *strextend(char **x, ...) {
                         break;
 
                 n = strlen(t);
+
+                if (need_separator)
+                        n += l_separator;
+
                 if (n > ((size_t) -1) - l) {
                         va_end(ap);
                         return NULL;
                 }
 
                 l += n;
+                need_separator = true;
         }
         va_end(ap);
 
+        need_separator = !isempty(*x);
+
         r = realloc(*x, l+1);
         if (!r)
                 return NULL;
 
         p = r + f;
 
-        va_start(ap, x);
+        va_start(ap, separator);
         for (;;) {
                 const char *t;
 
@@ -776,10 +787,17 @@ char *strextend(char **x, ...) {
                 if (!t)
                         break;
 
+                if (need_separator && separator)
+                        p = stpcpy(p, separator);
+
                 p = stpcpy(p, t);
+
+                need_separator = true;
         }
         va_end(ap);
 
+        assert(p == r + l);
+
         *p = 0;
         *x = r;
 

diff --git a/src/basic/string-util.h b/src/basic/string-util.h
index 684af0f3e48e9b49be5cb680a644ba7aa4d855a6..09a737ad3763a0618bd5b9b704237323f4f0bc99 100644 (file)
--- a/src/basic/string-util.h
+++ b/src/basic/string-util.h
@@ -179,7 +179,9 @@ char *strreplace(const char *text, const char *old_string, const char *new_strin
 
 char *strip_tab_ansi(char **p, size_t *l);
 
-char *strextend(char **x, ...) _sentinel_;
+char *strextend_with_separator(char **x, const char *separator, ...) _sentinel_;
+
+#define strextend(x, ...) strextend_with_separator(x, NULL, __VA_ARGS__)
 
 char *strrep(const char *s, unsigned n);
 

diff --git a/src/test/test-string-util.c b/src/test/test-string-util.c
index 7a14b8efd38a754f522cfcd032f89ad041073aac..07ee98465c63e933d330e53e557671030136bb38 100644 (file)
--- a/src/test/test-string-util.c
+++ b/src/test/test-string-util.c
@@ -104,9 +104,37 @@ static void test_strstrip(void) {
 }
 
 static void test_strextend(void) {
-        _cleanup_free_ char *str = strdup("0123");
-        strextend(&str, "456", "78", "9", NULL);
-        assert_se(streq(str, "0123456789"));
+        _cleanup_free_ char *str = NULL;
+
+        assert_se(strextend(&str, NULL));
+        assert_se(streq_ptr(str, ""));
+        assert_se(strextend(&str, "", "0", "", "", "123", NULL));
+        assert_se(streq_ptr(str, "0123"));
+        assert_se(strextend(&str, "456", "78", "9", NULL));
+        assert_se(streq_ptr(str, "0123456789"));
+}
+
+static void test_strextend_with_separator(void) {
+        _cleanup_free_ char *str = NULL;
+
+        assert_se(strextend_with_separator(&str, NULL, NULL));
+        assert_se(streq_ptr(str, ""));
+        str = mfree(str);
+
+        assert_se(strextend_with_separator(&str, "...", NULL));
+        assert_se(streq_ptr(str, ""));
+        assert_se(strextend_with_separator(&str, "...", NULL));
+        assert_se(streq_ptr(str, ""));
+        str = mfree(str);
+
+        assert_se(strextend_with_separator(&str, "xyz", "a", "bb", "ccc", NULL));
+        assert_se(streq_ptr(str, "axyzbbxyzccc"));
+        str = mfree(str);
+
+        assert_se(strextend_with_separator(&str, ",", "start", "", "1", "234", NULL));
+        assert_se(streq_ptr(str, "start,,1,234"));
+        assert_se(strextend_with_separator(&str, ";", "more", "5", "678", NULL));
+        assert_se(streq_ptr(str, "start,,1,234;more;5;678"));
 }
 
 static void test_strrep(void) {
@@ -399,6 +427,7 @@ int main(int argc, char *argv[]) {
         test_streq_ptr();
         test_strstrip();
         test_strextend();
+        test_strextend_with_separator();
         test_strrep();
         test_strappend();
         test_string_has_cc();