strv: add helper to find value in key/value pairs from list of keys

src/basic/strv.c

@@ -7,6 +7,7 @@
 #include <stdlib.h>
 
 #include "alloc-util.h"
+#include "env-util.h"
 #include "escape.h"
 #include "extract-word.h"
 #include "fileio.h"
@@ -63,6 +64,16 @@ char* strv_find_startswith(char * const *l, const char *name) {
         return NULL;
 }
 
+char* strv_find_first_field(char * const *needles, char * const *haystack) {
+        STRV_FOREACH(k, needles) {
+                char *value = strv_env_pairs_get((char **)haystack, *k);
+                if (value)
+                        return value;
+        }
+
+        return NULL;
+}
+
 char** strv_free(char **l) {
         STRV_FOREACH(k, l)
                 free(*k);

src/basic/strv.h

@@ -17,6 +17,9 @@ char* strv_find(char * const *l, const char *name) _pure_;
 char* strv_find_case(char * const *l, const char *name) _pure_;
 char* strv_find_prefix(char * const *l, const char *name) _pure_;
 char* strv_find_startswith(char * const *l, const char *name) _pure_;
+/* Given two vectors, the first a list of keys and the second a list of key-value pairs, returns the value
+ * of the first key from the first vector that is found in the second vector. */
+char* strv_find_first_field(char * const *needles, char * const *haystack) _pure_;
 
 #define strv_contains(l, s) (!!strv_find((l), (s)))
 #define strv_contains_case(l, s) (!!strv_find_case((l), (s)))