basic/strv: add function to insert items at position

src/basic/strv.c

@@ -446,7 +446,7 @@ int strv_push_pair(char ***l, char *a, char *b) {
         return 0;
 }
 
-int strv_push_prepend(char ***l, char *value) {
+int strv_insert(char ***l, unsigned position, char *value) {
         char **c;
         unsigned n, m, i;
 
@@ -454,6 +454,7 @@ int strv_push_prepend(char ***l, char *value) {
                 return 0;
 
         n = strv_length(*l);
+        position = MIN(position, n);
 
         /* increase and check for overflow */
         m = n + 2;
@@ -464,10 +465,12 @@ int strv_push_prepend(char ***l, char *value) {
         if (!c)
                 return -ENOMEM;
 
-        for (i = 0; i < n; i++)
+        for (i = 0; i < position; i++)
+                c[i] = (*l)[i];
+        c[position] = value;
+        for (i = position; i < n; i++)
                 c[i+1] = (*l)[i];
 
-        c[0] = value;
         c[n+1] = NULL;
 
         free(*l);

src/basic/strv.h

@@ -54,7 +54,12 @@ int strv_extendf(char ***l, const char *format, ...) _printf_(2,0);
 int strv_extend_front(char ***l, const char *value);
 int strv_push(char ***l, char *value);
 int strv_push_pair(char ***l, char *a, char *b);
-int strv_push_prepend(char ***l, char *value);
+int strv_insert(char ***l, unsigned position, char *value);
+
+static inline int strv_push_prepend(char ***l, char *value) {
+        return strv_insert(l, 0, value);
+}
+
 int strv_consume(char ***l, char *value);
 int strv_consume_pair(char ***l, char *a, char *b);
 int strv_consume_prepend(char ***l, char *value);

src/test/test-strv.c

@@ -447,6 +447,36 @@ static void test_strv_from_stdarg_alloca(void) {
         test_strv_from_stdarg_alloca_one(STRV_MAKE_EMPTY, NULL);
 }
 
+static void test_strv_insert(void) {
+        _cleanup_strv_free_ char **a = NULL;
+
+        assert_se(strv_insert(&a, 0, strdup("first")) == 0);
+        assert_se(streq(a[0], "first"));
+        assert_se(!a[1]);
+
+        assert_se(strv_insert(&a, 0, NULL) == 0);
+        assert_se(streq(a[0], "first"));
+        assert_se(!a[1]);
+
+        assert_se(strv_insert(&a, 1, strdup("two")) == 0);
+        assert_se(streq(a[0], "first"));
+        assert_se(streq(a[1], "two"));
+        assert_se(!a[2]);
+
+        assert_se(strv_insert(&a, 4, strdup("tri")) == 0);
+        assert_se(streq(a[0], "first"));
+        assert_se(streq(a[1], "two"));
+        assert_se(streq(a[2], "tri"));
+        assert_se(!a[3]);
+
+        assert_se(strv_insert(&a, 1, strdup("duo")) == 0);
+        assert_se(streq(a[0], "first"));
+        assert_se(streq(a[1], "duo"));
+        assert_se(streq(a[2], "two"));
+        assert_se(streq(a[3], "tri"));
+        assert_se(!a[4]);
+}
+
 static void test_strv_push_prepend(void) {
         _cleanup_strv_free_ char **a = NULL;
 
@@ -723,6 +753,7 @@ int main(int argc, char *argv[]) {
         test_strv_extend();
         test_strv_extendf();
         test_strv_from_stdarg_alloca();
+        test_strv_insert();
         test_strv_push_prepend();
         test_strv_push();
         test_strv_equal();