string-table: Move more implementation logic into functions

Let's move some more implementation logic into functions. We keep
the logic that requires the macro in the macro and move the rest into
functions.

While we're at it, let's also make the parameter declarations of
all the string table macros less clausthrophobic.

src/basic/string-table.c

@@ -1,9 +1,17 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
+#include "parse-util.h"
 #include "string-table.h"
 #include "string-util.h"
 
-ssize_t string_table_lookup(const char * const *table, size_t len, const char *key) {
+const char* string_table_lookup_to_string(const char * const *table, size_t len, ssize_t i) {
+        if (i < 0 || i >= (ssize_t) len)
+                return NULL;
+
+        return table[i];
+}
+
+ssize_t string_table_lookup_from_string(const char * const *table, size_t len, const char *key) {
         if (!key)
                 return -EINVAL;
 
@@ -13,3 +21,49 @@ ssize_t string_table_lookup(const char * const *table, size_t len, const char *k
 
         return -EINVAL;
 }
+
+ssize_t string_table_lookup_from_string_with_boolean(const char * const *table, size_t len, const char *key, ssize_t yes) {
+        if (!key)
+                return -EINVAL;
+
+        int b = parse_boolean(key);
+        if (b == 0)
+                return 0;
+        if (b > 0)
+                return yes;
+
+        return string_table_lookup_from_string(table, len, key);
+}
+
+int string_table_lookup_to_string_fallback(const char * const *table, size_t len, ssize_t i, size_t max, char **ret) {
+        char *s;
+
+        if (i < 0 || i > (ssize_t) max)
+                return -ERANGE;
+        if (i < (ssize_t) len && table[i]) {
+                s = strdup(table[i]);
+                if (!s)
+                        return -ENOMEM;
+        } else if (asprintf(&s, "%zd", i) < 0)
+                return -ENOMEM;
+
+        *ret = s;
+        return 0;
+}
+
+ssize_t string_table_lookup_from_string_fallback(const char * const *table, size_t len, const char *s, size_t max) {
+        unsigned u = 0;
+
+        if (!s)
+                return -EINVAL;
+
+        ssize_t i = string_table_lookup_from_string(table, len, s);
+        if (i >= 0)
+                return i;
+        if (safe_atou(s, &u) < 0)
+                return -EINVAL;
+        if (u > max)
+                return -EINVAL;
+
+        return u;
+}